Availability of hydrogen for lunar base activities

NASA Technical Reports Server (NTRS)

Bustin, Roberta

1990-01-01

Hydrogen will be needed on a lunar base to make water for consumables, to provide fuel, and to serve as reducing agent in the extraction of oxygen from lunar minerals. The abundance and distribution of solar wind implanted hydrogen were studied. Hydrogen was found in all samples studied with concentrations varying widely depending on soil maturity, grain size, and mineral composition. Seven cores returned from the moon were studied. Although hydrogen was implanted in the upper surface layer of the regolith, it was found throughout the cores due to micrometeorite reworking of the soil.

Silicate and carbonate mineral weathering in soil profiles developed on Pleistocene glacial drift (Michigan, USA): Mass balances based on soil water geochemistry

NASA Astrophysics Data System (ADS)

Jin, Lixin; Williams, Erika L.; Szramek, Kathryn J.; Walter, Lynn M.; Hamilton, Stephen K.

2008-02-01

Geochemistry of soil, soil water, and soil gas was characterized in representative soil profiles of three Michigan watersheds. Because of differences in source regions, parent materials in the Upper Peninsula of Michigan (the Tahquamenon watershed) contain only silicates, while those in the Lower Peninsula (the Cheboygan and the Huron watersheds) have significant mixtures of silicate and carbonate minerals. These differences in soil mineralogy and climate conditions permit us to examine controls on carbonate and silicate mineral weathering rates and to better define the importance of silicate versus carbonate dissolution in the early stage of soil-water cation acquisition. Soil waters of the Tahquamenon watershed are the most dilute; solutes reflect amphibole and plagioclase dissolution along with significant contributions from atmospheric precipitation sources. Soil waters in the Cheboygan and the Huron watersheds begin their evolution as relatively dilute solutions dominated by silicate weathering in shallow carbonate-free soil horizons. Here, silicate dissolution is rapid and reaction rates dominantly are controlled by mineral abundances. In the deeper soil horizons, silicate dissolution slows down and soil-water chemistry is dominated by calcite and dolomite weathering, where solutions reach equilibrium with carbonate minerals within the soil profile. Thus, carbonate weathering intensities are dominantly controlled by annual precipitation, temperature and soil pCO 2. Results of a conceptual model support these field observations, implying that dolomite and calcite are dissolving at a similar rate, and further dissolution of more soluble dolomite after calcite equilibrium produces higher dissolved inorganic carbon concentrations and a Mg 2+/Ca 2+ ratio of 0.4. Mass balance calculations show that overall, silicate minerals and atmospheric inputs generally contribute <10% of Ca 2+ and Mg 2+ in natural waters. Dolomite dissolution appears to be a major process, rivaling calcite dissolution as a control on divalent cation and inorganic carbon contents of soil waters. Furthermore, the fraction of Mg 2+ derived from silicate mineral weathering is much smaller than most of the values previously estimated from riverine chemistry.

Post-deposition early-phase migration and retention behavior of radiocesium in a litter-mineral soil system in a Japanese deciduous forest affected by the Fukushima nuclear accident.

PubMed

Koarashi, Jun; Nishimura, Syusaku; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi

2016-12-01

The fate of radiocesium ( 137 Cs) derived from the Fukushima nuclear accident and associated radiation risks are largely dependent on its migration and retention behavior in the litter-soil system of Japanese forest ecosystems. However, this behavior has not been well quantified. We established field lysimeters in a Japanese deciduous broad-leaved forest soon after the Fukushima nuclear accident to continuously monitor the downward transfer of 137 Cs at three depths: the litter-mineral soil boundary and depths of 5 cm and 10 cm in the mineral soil. Observations were conducted at two sites within the forest from May 2011 to May 2015. Results revealed similar temporal and depth-wise variations in 137 Cs downward fluxes for both sites. The 137 Cs downward fluxes generally decreased year by year at all depths, indicating that 137 Cs was rapidly leached from the forest-floor litter layer and was then immobilized in the upper (0-5 cm) mineral soil layer through its interaction with clay minerals. The 137 Cs fluxes also showed seasonal variation, which was in accordance with variations in the throughfall and soil temperature at the sites. There was no detectable 137 Cs flux at a depth of 10 cm in the mineral soil in the third and fourth years after the accident. The decreased inventory of mobile (or bioavailable) 137 Cs observed during early stages after deposition indicates that the litter-soil system in the Japanese deciduous forest provides only a temporary source for 137 Cs recycling in plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Viability of litter-stored Pinus taeda L. seeds after simulated prescribed winter burns

Treesearch

Michael D. Cain; Michael G. Shelton

1998-01-01

Stratified loblolly pine (Pinus taeda L.) seeds were placed at three depths in a reconstructed forest floor and subjected to simulated prescribed winter burns. Within the forest floor, pine seeds were placed at the L/upper-F interface, upper-F/lower-F interface, and lower-F/mineral-soil interface. Wind was generated by electric box-fans. Seeds that...

Availability of hydrogen for lunar base activities

NASA Technical Reports Server (NTRS)

Bustin, Roberta; Gibson, Everett K., Jr.

1992-01-01

Hydrogen will be needed on a lunar base to make water for consumables, to provide fuel, and to serve as a reducing agent in the extraction of oxygen from lunar minerals. This study was undertaken in order to learn more about the abundance and distribution of solar-wind-implanted hydrogen. Hydrogen was found in all samples studied, with concentrations, varying widely depending on soil maturity, grain size, and mineral composition. Seven cores returned from the Moon were studied. Although hydrogen was implanted in the upper surface layer of the regolith, it was found throughout the cores due to micrometeorite reworking of the soil.

Relevant magnetic and soil parameters as potential indicators of soil conservation status of Mediterranean agroecosystems

NASA Astrophysics Data System (ADS)

Quijano, Laura; Chaparro, Marcos A. E.; Marié, Débora C.; Gaspar, Leticia; Navas, Ana

2014-09-01

The main sources of magnetic minerals in soils unaffected by anthropogenic pollution are iron oxides and hydroxides derived from parent materials through soil formation processes. Soil magnetic minerals can be used as indicators of environmental factors including soil forming processes, degree of pedogenesis, weathering processes and biological activities. In this study measurements of magnetic susceptibility are used to detect the presence and the concentration of soil magnetic minerals in topsoil and bulk samples in a small cultivated field, which forms a hydrological unit that can be considered to be representative of the rainfed agroecosystems of Mediterranean mountain environments. Additional magnetic studies such as isothermal remanent magnetization (IRM), anhysteretic remanent magnetization (ARM) and thermomagnetic measurements are used to identify and characterize the magnetic mineralogy of soil minerals. The objectives were to analyse the spatial variability of the magnetic parameters to assess whether topographic factors, soil redistribution processes, and soil properties such as soil texture, organic matter and carbonate contents analysed in this study, are related to the spatial distribution pattern of magnetic properties. The medians of mass specific magnetic susceptibility at low frequency (χlf) were 36.0 and 31.1 × 10-8 m3 kg-1 in bulk and topsoil samples respectively. High correlation coefficients were found between the χlf in topsoil and bulk core samples (r = 0.951, p < 0.01). In addition, volumetric magnetic susceptibility was measured in situ in the field (κis) and values varied from 13.3 to 64.0 × 10-5 SI. High correlation coefficients were found between χlf in topsoil measured in the laboratory and volumetric magnetic susceptibility field measurements (r = 0.894, p < 0.01). The results obtained from magnetic studies such as IRM, ARM and thermomagnetic measurements show the presence of magnetite, which is the predominant magnetic carrier, and hematite. The predominance of superparamagnetic minerals in upper soil layers suggests enrichment in pedogenic minerals. The finer soil particles, the organic matter content and the magnetic susceptibility values are statistically correlated and their spatial variability is related to similar physical processes. Runoff redistributes soil components including magnetic minerals and exports fine particles out the field. This research contributed to further knowledge on the application of soil magnetic properties to derive useful information on soil processes in Mediterranean cultivated soils.

Determination of hydrogen abundance in selected lunar soils

NASA Technical Reports Server (NTRS)

Bustin, Roberta

1987-01-01

Hydrogen was implanted in lunar soil through solar wind activity. In order to determine the feasibility of utilizing this solar wind hydrogen, it is necessary to know not only hydrogen abundances in bulk soils from a variety of locations but also the distribution of hydrogen within a given soil. Hydrogen distribution in bulk soils, grain size separates, mineral types, and core samples was investigated. Hydrogen was found in all samples studied. The amount varied considerably, depending on soil maturity, mineral types present, grain size distribution, and depth. Hydrogen implantation is definitely a surface phenomenon. However, as constructional particles are formed, previously exposed surfaces become embedded within particles, causing an enrichment of hydrogen in these species. In view of possibly extracting the hydrogen for use on the lunar surface, it is encouraging to know that hydrogen is present to a considerable depth and not only in the upper few millimeters. Based on these preliminary studies, extraction of solar wind hydrogen from lunar soil appears feasible, particulary if some kind of grain size separation is possible.

Shifts of tundra bacterial and archaeal communities along a permafrost thaw gradient in Alaska.

PubMed

Deng, Jie; Gu, Yunfu; Zhang, Jin; Xue, Kai; Qin, Yujia; Yuan, Mengting; Yin, Huaqun; He, Zhili; Wu, Liyou; Schuur, Edward A G; Tiedje, James M; Zhou, Jizhong

2015-01-01

Understanding the response of permafrost microbial communities to climate warming is crucial for evaluating ecosystem feedbacks to global change. This study investigated soil bacterial and archaeal communities by Illumina MiSeq sequencing of 16S rRNA gene amplicons across a permafrost thaw gradient at different depths in Alaska with thaw progression for over three decades. Over 4.6 million passing 16S rRNA gene sequences were obtained from a total of 97 samples, corresponding to 61 known classes and 470 genera. Soil depth and the associated soil physical-chemical properties had predominant impacts on the diversity and composition of the microbial communities. Both richness and evenness of the microbial communities decreased with soil depth. Acidobacteria, Verrucomicrobia, Alpha- and Gamma-Proteobacteria dominated the microbial communities in the upper horizon, whereas abundances of Bacteroidetes, Delta-Proteobacteria and Firmicutes increased towards deeper soils. Effects of thaw progression were absent in microbial communities in the near-surface organic soil, probably due to greater temperature variation. Thaw progression decreased the abundances of the majority of the associated taxa in the lower organic soil, but increased the abundances of those in the mineral soil, including groups potentially involved in recalcitrant C degradation (Actinomycetales, Chitinophaga, etc.). The changes in microbial communities may be related to altered soil C sources by thaw progression. Collectively, this study revealed different impacts of thaw in the organic and mineral horizons and suggests the importance of studying both the upper and deeper soils while evaluating microbial responses to permafrost thaw. © 2014 John Wiley & Sons Ltd.

Increasing Soil Calcium Availability Alters Forest Soil Carbon Stocks

NASA Astrophysics Data System (ADS)

Melvin, A.; Goodale, C. L.

2011-12-01

Acid deposition in the Northeastern U.S. has been linked to a loss of soil base cations, especially calcium (Ca). While much research has addressed the effects of Ca depletion on soil and stream acidification, few studies have investigated its effects on ecosystem carbon (C) balance. We studied the long-term effects of increased Ca availability on C cycling in a northern hardwood forest in the Adirondack Park, NY. In 1989, calcium carbonate (lime) was added to ~ 100 ha of the Woods Lake Watershed to ameliorate the effects of soil Ca depletion. An additional 100 ha were maintained as controls. We hypothesized that the lime addition would improve forest health and that this improvement would be evident in increased tree biomass, leaf litter, and fine root production. Within the forest floor, we anticipated that the increased pH associated with liming would stimulate microbial activity resulting in increased decomposition and basal soil respiration, and reduced C stocks. Additionally, we hypothesized that increased Ca availability could enhance Ca-OM complexation in the upper mineral soils, leading to increased C stocks in these horizons. Eighteen years after liming, soil pH and exchangeable Ca pools remained elevated in the forest floor and upper mineral soil of the limed plots. Forest floor C stocks were significantly larger in limed plots (68 vs. 31 t C ha-1), and were driven primarily by greater C accumulation in the forest floor Oa horizon. Mineral soil C stocks did not differ between limed and control soils. Liming did not affect tree growth, however a net decline in biomass was observed across the entire watershed. There was a trend for larger fine root and foliar litter inputs in limed plots relative to controls, but the observed forest floor accumulation appears to be driven primarily by a suppression of decomposition. Liming reduced basal soil respiration rates by 17 and 43 % in the Oe and Oa horizons, respectively. This research suggests that Ca may stabilize soil organic matter and that long-term Ca depletion caused by acid deposition could have large, unexpected effects on ecosystem C dynamics.

Heavy minerals in the 2011 Tohoku-oki tsunami deposits—insights into sediment sources and hydrodynamics

NASA Astrophysics Data System (ADS)

Jagodziński, Robert; Sternal, Beata; Szczuciński, Witold; Chagué-Goff, Catherine; Sugawara, Daisuke

2012-12-01

The 2011 Tohoku-oki tsunami left sand and mud deposits more than 4 km inland on the coastal plain of Sendai, Japan. The tsunami deposits, pre-tsunami soils and beach sediments were analysed for grain size, and heavy mineral content and assemblages to test the applicability of heavy mineral analyses in the identification of tsunami deposits and interpretation of associated sedimentation processes. Heavy minerals comprised on average 35% of the tsunami deposit in the 0.125-0.25 mm grain size fraction. The most common were orthopyroxenes, clinopyroxenes, amphiboles, limonites and opaque minerals. Heavy mineral concentrations and assemblages were similar in the tsunami deposits, beach and pre-tsunami soils and sediments and thus tsunami deposits could not simply be identified based on their heavy minerals. Sediment provenance analysis revealed that tsunami deposits left within 1.5 km of the shoreline were mostly eroded from the beach, dune and local soils, while deposits farther inland (> 1.5 km) were mostly derived from local soil erosion. No evidence was found for a significant contribution of offshore sediments. Detailed analyses revealed that the lowermost portion of tsunami deposits was mostly of local origin, while the sediment source of the upper portion was variable. A comparison with a previous study of heavy minerals in 2004 IOT deposits confirms that heavy minerals in tsunami deposits are mostly source-dependent and may represent a useful supplementary tool in studies of tsunami deposits. However, the interpretation must always be placed in the local geological context and corroborated with other "tsunami proxies".

Soil Surface Organic Layers in Alaska's Arctic Foothills: Development, Distribution and Microclimatic Feedbacks

NASA Astrophysics Data System (ADS)

Baughman, C. A.; Mann, D. H.; Verbyla, D.; Valentine, D.; Kunz, M. L.; Heiser, P. A.

2013-12-01

Accumulated organic matter at the ground surface plays an important role in arctic ecosystems. These soil surface organic layers (SSOLs) influence temperature, moisture, and chemistry in the underlying mineral soil and, on a global basis, comprise enormous stores of labile carbon. Understanding the dynamics of SSOLs is prerequisite to modeling the responses of arctic ecosystem processes to climate changes. Here, we ask three questions regarding SSOLs in the Arctic Foothills in northern Alaska: 1) What environmental factors control their spatial distribution? 2) How long do they take to form? 3) What is the relationship between SSOL thickness and mineral soil temperature through the growing season? The best topographically-controlled predictors of SSOL thickness and spatial distribution are duration of sunlight during the growing-season, upslope drainage area, slope gradient, and elevation. SSOLs begin to form within several decades following disturbance but require 500-700 years to reach equilibrium states. Once formed, mature SSOLs lower peak growing-season temperature and mean annual temperature in the underlying mineral horizon by 8° and 3° C respectively, which reduces available growing degree days within the upper mineral soil by nearly 80%. How ongoing climate change in northern Alaska will affect the region's SSOLs is an open and potentially crucial question.

Provenance and geochemical behavior of fluorine in the soils of an endemic fluorosis belt, central Iran

NASA Astrophysics Data System (ADS)

Dehbandi, Reza; Moore, Farid; Keshavarzi, Behnam

2017-05-01

The concentration of fluorine, major, trace and rare earth elements (REEs) were used to estimate the probable sources and provenance of fluorine in the soils of an endemic fluorosis belt in central Iran. Total fluorine (TF) in soils varied from 146 to 406 mg/kg with a mean of 277.5 mg/kg. Calculated enrichment factor (EF) and single factor pollution index (SFPI) revealed that the majority of soil samples were moderately contaminated by fluorine. The very strong positive correlation of TF with weathering indices and soil's fine sized fractions indicated that chemical weathering and alteration of parent rocks/soils are the main controlling factors of fluorine behavior in soils. Fluorine affinity to immobile transition trace elements and REEs suggested the role of heavy minerals as the potential F host phases. Modal mineralogy along with SEM-EDX analysis indicated that apatite, fluorapophyllite, epidote, biotite, muscovite and chlorite, as well as, clay minerals are the main F-bearing minerals in the studied soils. Discriminant, bivariate and ternary diagrams of elemental compositions displayed similar geochemical signature of soils to intermediate-acidic rocks and local shales. Based on the weathering indices, soils were immature and showed a non-steady state weathering trend from upper continental crust (UCC), acidic and intermediate igneous source rocks towards shale composition possibly due to mixing of moderately weathered and un-weathered sources of different primary compositions.

Changes in soil characteristics and C dynamics after mangrove clearing (Vietnam).

PubMed

Grellier, Séraphine; Janeau, Jean-Louis; Dang Hoai, Nhon; Nguyen Thi Kim, Cuc; Le Thi Phuong, Quynh; Pham Thi Thu, Thao; Tran-Thi, Nhu-Trang; Marchand, Cyril

2017-09-01

Of the blue carbon sinks, mangroves have one of the highest organic matter (OM) storage capacities in their soil due to low mineralization processes resulting from waterlogging. However, mangroves are disappearing worldwide because of demographic increases. In addition to the loss of CO 2 fixation, mangrove clearing can strongly affect soil characteristics and C storage. The objectives of the present study were to quantify the evolution of soil quality, carbon stocks and carbon fluxes after mangrove clearing. Sediment cores to assess physico-chemical properties were collected and in situ CO 2 fluxes were measured at the soil-air interface in a mangrove of Northern Vietnam. We compared a Kandelia candel mangrove forest with a nearby zone that had been cleared two years before the study. Significant decrease of clay content and an increase in bulk density for the upper 35cm in the cleared zone were observed. Soil organic carbon (OC) content in the upper 35cm decreased by >65% two years after clearing. The quantity and the quality of the carbon changed, with lower carbon to nitrogen ratios, indicating a more decomposed OM, a higher content of dissolved organic carbon, and a higher content of inorganic carbon (three times higher). This highlights the efficiency of mineralization processes following clearing. Due to the rapid decrease in the soil carbon content, CO 2 fluxes at sediment interface were >50% lower in the cleared zone. Taking into account carbonate precipitation after OC mineralization, the mangrove soil lost ~10MgOCha -1 yr -1 mostly as CO 2 to the atmosphere and possibly as dissolved forms towards adjacent ecosystems. The impacts on the carbon cycle of mangrove clearing as shown by the switch from a C sink to a C source highlight the importance of maintaining these ecosystems, particularly in a context of climate change. Copyright © 2017 Elsevier B.V. All rights reserved.

Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach

USGS Publications Warehouse

Bullen, T.D.; Bailey, S.W.

2005-01-01

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87Sr/86Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87Sr/86Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87Sr/86Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms. ?? Springer 2005.

Massive carbon addition to an organic-rich Andosol increased the subsoil but not the topsoil carbon stock

NASA Astrophysics Data System (ADS)

Zieger, Antonia; Kaiser, Klaus; Ríos Guayasamín, Pedro; Kaupenjohann, Martin

2018-05-01

Andosols are among the most carbon-rich soils, with an average of 254 Mg ha-1 organic carbon (OC) in the upper 100 cm. A current theory proposes an upper limit for OC stocks independent of increasing carbon input, because of finite binding capacities of the soil mineral phase. We tested the possible limits in OC stocks for Andosols with already large OC concentrations and stocks (212 g kg-1 in the first horizon, 301 Mg ha-1 in the upper 100 cm). The soils received large inputs of 1800 Mg OC ha-1 as sawdust within a time period of 20 years. Adjacent soils without sawdust application served as controls. We determined total OC stocks as well as the storage forms of organic matter (OM) of five horizons down to 100 cm depth. Storage forms considered were pyrogenic carbon, OM of < 1.6 g cm-3 density and with little to no interaction with the mineral phase, and strongly mineral-bonded OM forming particles of densities between 1.6 and 2.0 g cm-3 or > 2.0 g cm-3. The two fractions > 1.6 g cm-3 were also analysed for aluminium-organic matter complexes (Al-OM complexes) and imogolite-type phases using ammonium-oxalate-oxalic-acid extraction and X-ray diffraction (XRD). Pyrogenic organic carbon represented only up to 5 wt % of OC, and thus contributed little to soil OM. In the two topsoil horizons, the fraction between 1.6 and 2.0 g cm-3 had 65-86 wt % of bulk soil OC and was dominated by Al-OM complexes. In deeper horizons, the fraction > 2.0 g cm-3 contained 80-97 wt % of the bulk soil's total OC and was characterized by a mixture of Al-OM complexes and imogolite-type phases, with proportions of imogolite-type phases increasing with depth. In response to the sawdust application, only the OC stock at 25-50 cm depth increased significantly (α = 0.05, 1 - β = 0.8). The increase was entirely due to increased OC in the two fractions > 1.6 g cm-3. However, there was no significant increase in the total OC stocks within the upper 100 cm. The results suggest that long-term large OC inputs cannot be taken up by the obviously OC-saturated topsoil but induce downward migration and gradually increasing storage of OC in subsurface soil layers. The small additional OC accumulation despite the extremely large OC input over 20 years, however, shows that long time periods of high input are needed to promote the downward movement and deep soil storage of OC.

Spatial patterns and controls of soil chemical weathering rates along a transient hillslope

USGS Publications Warehouse

Yoo, K.; Mudd, S.M.; Sanderman, J.; Amundson, Ronald; Blum, A.

2009-01-01

Hillslopes have been intensively studied by both geomorphologists and soil scientists. Whereas geomorphologists have focused on the physical soil production and transport on hillslopes, soil scientists have been concerned with the topographic variation of soil geochemical properties. We combined these differing approaches and quantified soil chemical weathering rates along a grass covered hillslope in Coastal California. The hillslope is comprised of both erosional and depositional sections. In the upper eroding section, soil production is balanced by physical erosion and chemical weathering. The hillslope then transitions to a depositional slope where soil accumulates due to a historical reduction of channel incision at the hillslope's base. Measurements of hillslope morphology and soil thickness were combined with the elemental composition of the soil and saprolite, and interpreted through a process-based model that accounts for both chemical weathering and sediment transport. Chemical weathering of the minerals as they moved downslope via sediment transport imparted spatial variation in the geochemical properties of the soil. Inverse modeling of the field and laboratory data revealed that the long-term soil chemical weathering rates peak at 5 g m- 2 yr- 1 at the downslope end of the eroding section and decrease to 1.5 g m- 2 yr- 1 within the depositional section. In the eroding section, soil chemical weathering rates appear to be primarily controlled by the rate of mineral supply via colluvial input from upslope. In the depositional slope, geochemical equilibrium between soil water and minerals appeared to limit the chemical weathering rate. Soil chemical weathering was responsible for removing 6% of the soil production in the eroding section and 5% of colluvial influx in the depositional slope. These were among the lowest weathering rates reported for actively eroding watersheds, which was attributed to the parent material with low amount of weatherable minerals and intense coating of the primary minerals by secondary clay and iron oxides. We showed that both the morphologic disequilibrium of the hillslope and the spatial heterogeneity of soil properties are due to spatial variations in the physical and chemical processes that removed mass from the soil. ?? 2009 Elsevier B.V.

Global W`o'rming and Darwin Revisited: Quantifying Soil Mixing Rates by Non-native Earthworms in Fennoscandian Boreal and Arctic Ecosystems

NASA Astrophysics Data System (ADS)

Wackett, A. A.; Yoo, K.; Cameron, E. K.; Olid, C.; Klaminder, J.

2017-12-01

Fennoscandian boreal and arctic ecosystems represent some of the most pristine environments in Europe and store sizeable quantities of soil carbon. Both ecosystems may have evolved without native earthworms since the last glaciation, but are now increasingly subject to arrivals of novel geoengineering earthworm species due to human activities. As a result, invaded areas are devoid of the typical thick organic horizon present in earthworm free forest soils and instead contain carbon-rich mineral (A-horizon) soils at the surface. How rapidly this transition occurs and how it affects the fate of soil organic carbon (SOC) pools is not well known. In this study, we quantify the rates at which earthworm-mediated mixing of forest soils proceeds in these formerly glaciated landscapes. We infer soil mass fluxes using the vertical distribution of 210Pb in soils from Fennoscandia (N=4) and North America (N=1) and quantify annual mixing velocities as well as vertical fluxes of organic and mineral matter throughout the upper soil profiles. Across the sites, mixing velocities generally increase with increasing earthworm biomass and functional group diversity, and our annual mixing rates closely align with those predicted by Darwin for earthworm-engineered ecosystems in the UK 130 years earlier. Reduction of the O-horizon is concomitant with a decrease in surface SOC contents. However, we observe minimal changes to SOC inventories with earthworm invasion across the sites, reflecting the upward translocation of mineral soil and accompanying increase in soil bulk densities. Thus, the reduction or depletion of organic horizon by exotic earthworms does not necessarily involve loss of SOC via earthworm-accelerated decomposition, but is rather compensated for by physical mixing of organic matter and minerals, which may facilitate stabilizing organo-mineral interactions. This work constitutes an important step to elucidate how non-native earthworms impact SOC inventories and potentially carbon turnover time across the formerly glaciated worlds.

Defining the upper viscosity limit for mineral slurries used in drilled shaft construction : [summary].

DOT National Transportation Integrated Search

2014-02-01

Many structures built on Floridas variable, sandy : soils require deep foundations, such as pilings. : Although pilings may be more familiar, drilled : shafts are also often used. Drilled shafts require : less expensive equipment and create less o...

Synergistic Processing of Biphenyl and Benzoate: Carbon Flow Through the Bacterial Community in Polychlorinated-Biphenyl-Contaminated Soil

NASA Astrophysics Data System (ADS)

Leewis, Mary-Cathrine; Uhlik, Ondrej; Leigh, Mary Beth

2016-02-01

Aerobic mineralization of PCBs, which are toxic and persistent organic pollutants, involves the upper (biphenyl, BP) and lower (benzoate, BZ) degradation pathways. The activity of different members of the soil microbial community in performing one or both pathways, and their synergistic interactions during PCB biodegradation, are not well understood. This study investigates BP and BZ biodegradation and subsequent carbon flow through the microbial community in PCB-contaminated soil. DNA stable isotope probing (SIP) was used to identify the bacterial guilds involved in utilizing 13C-biphenyl (unchlorinated analogue of PCBs) and/or 13C-benzoate (product/intermediate of BP degradation and analogue of chlorobenzoates). By performing SIP with two substrates in parallel, we reveal microbes performing the upper (BP) and/or lower (BZ) degradation pathways, and heterotrophic bacteria involved indirectly in processing carbon derived from these substrates (i.e. through crossfeeding). Substrate mineralization rates and shifts in relative abundance of labeled taxa suggest that BP and BZ biotransformations were performed by microorganisms with different growth strategies: BZ-associated bacteria were fast growing, potentially copiotrophic organisms, while microbes that transform BP were oligotrophic, slower growing, organisms. Our findings provide novel insight into the functional interactions of soil bacteria active in processing biphenyl and related aromatic compounds in soil, revealing how carbon flows through a bacterial community.

Vertical profile measurements of soil air suggest immobilization of gaseous elemental mercury in mineral soil.

PubMed

Obrist, Daniel; Pokharel, Ashok K; Moore, Christopher

2014-02-18

Evasion of gaseous elemental Hg (Hg(0)g) from soil surfaces is an important source of atmospheric Hg, but the volatility and solid-gas phase partitioning of Hg(0) within soils is poorly understood. We developed a novel system to continuously measure Hg(0)g concentrations in soil pores at multiple depths and locations, and present a total of 297 days of measurements spanning 14 months in two forests in the Sierra Nevada mountains, California, U.S. Temporal patterns showed consistent pore Hg(0)g concentrations below levels measured in the atmosphere (termed Hg(0)g immobilization), ranging from 66 to 94% below atmospheric concentrations throughout multiple seasons. The lowest pore Hg(0)g concentrations were observed in the deepest soil layers (40 cm), but significant immobilization was already present in the top 7 cm. In the absence of sinks or sources, pore Hg(0)g levels would be in equilibrium with atmospheric concentrations due to the porous nature of the soil matrix and gas diffusion. Therefore, we explain decreases in pore Hg(0)g in mineral soils below atmospheric concentrations--or below levels found in upper soils as observed in previous studies--with the presence of an Hg(0)g sink in mineral soils possibly related to Hg(0)g oxidation or other processes such as sorption or dissolution in soil water. Surface chamber measurements showing daytime Hg(0)g emissions and nighttime Hg(0)g deposition indicate that near-surface layers likely dominate net atmospheric Hg(0)g exchange resulting in typical diurnal cycles due to photochemcial reduction at the surface and possibly Hg(0)g evasion from litter layers. In contrast, mineral soils seem to be decoupled from this surface exchange, showing consistent Hg(0)g uptake and downward redistribution--although our calculations indicate these fluxes to be minor compared to other mass fluxes. A major implication is that once Hg is incorporated into mineral soils, it may be unlikely subjected to renewed Hg(0)g re-emission from undisturbed, background soils emphasizing the important role of soils in sequestering past and current Hg pollution loads.

Mercury in litterfall and upper soil horizons in forested ecosystems in Vermont, USA.

PubMed

Juillerat, Juliette I; Ross, Donald S; Bank, Michael S

2012-08-01

Mercury (Hg) is an atmospheric pollutant that, in forest ecosystems, accumulates in foliage and upper soil horizons. The authors measured soil and litterfall Hg at 15 forest sites (northern hardwood to mixed hardwood/conifer) throughout Vermont, USA, to examine variation among tree species, forest type, and soils. Differences were found among the 12 tree species sampled from at least two sites, with Acer pensylvanicum having significantly greater litterfall total Hg concentration. Senescent leaves had greater Hg concentrations if they originated lower in the canopy or had higher surface:weight ratios. Annual litterfall Hg flux had a wide range, 12.6 to 28.5 µg/m(2) (mean, 17.9 µg/m(2) ), not related to forest type. Soil and Hg pools in the Oi horizon (litter layer) were not related to the measured Hg deposition flux in litterfall or to total modeled Hg deposition. Despite having lower Hg concentrations, upper mineral soil (A horizons) had greater Hg pools than organic soil horizons (forest floor) due to greater bulk density. Significant differences were found in Hg concentration and Hg/C ratio among soil horizons but not among forest types. Overall, our findings highlight the importance of site history and the benefits of collecting litterfall and soils simultaneously. Observed differences in forest floor Hg pools were strongly correlated with carbon pools, which appeared to be a function of historic land-use patterns. Copyright © 2012 SETAC.

Weathering behavior of REE-Y in a granitic soil profile (Case of Strengbach watershed)

NASA Astrophysics Data System (ADS)

Gangloff, Sophie; Stille, Peter; Chabaux, François

2017-04-01

Rare earth elements and yttrium (REE-Y) can be used as tracers of bedrock weathering and soil formation. One of the aims of this study is to better understand the different phenomena which impact the REE-Y mobilization and modify the REE-Y pattern along a soil profile. Our study has been performed on a granitic soil profile and soil solutions corresponding, sampled in a forest parcel covered with spruces from the Strengbach catchment. The behavior of the REE-Y pattern are compared with previously published results. The samples were collected from 2009 to 2013 and ultra-filtered to determine the spatial and temporal influence as well as that of the colloidal and dissolved fractions on the evolution of the REE-Y patterns. The EFTi of the soil indicates that during alteration process, phosphate minerals and zircon might be dissolved and induce the formation of secondary mineral phase like xenotime in the deeper soil horizons. The ultra-filtered soil solutions from humic horizon show that the REE-Y are principally enriched in the colloidal fraction controlling the REE-Y dynamic while in the deeper soil solutions colloidal and dissolved fractions influence the REE-Y. The mobility of REE-Y is controlled by the dissolution of the zircon and phosphate minerals, the precipitation of the REE-Y(PO4) and the evolution of OC with depth. The comparative study of the soil profile, soil water extracts and soil solutions show that (Eu*/Eu)DS anomaly reflects weathering of plagioclase in the micropores and the migration of the released Eu to the macropores, the (Ce*/Ce) anomaly, is stabilized by the electron shuttling of the humic acid (aromaticity) and provides information on the redox conditions only in the deeper soil horizons depleted in humic acid and finally the HREE enrichment in the deeper soil solutions results from the partial dissolution of secondary minerals in the upper soil horizons (above 30 cm depth).

Effects of nitrogen additions on above- and belowground carbon dynamics in two tropical forests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cusack, D.; Silver, W.L.; Torn, M.S.

2011-04-15

Anthropogenic nitrogen (N) deposition is increasing rapidly in tropical regions, adding N to ecosystems that often have high background N availability. Tropical forests play an important role in the global carbon (C) cycle, yet the effects of N deposition on C cycling in these ecosystems are poorly understood. We used a field N-fertilization experiment in lower and upper elevation tropical rain forests in Puerto Rico to explore the responses of above- and belowground C pools to N addition. As expected, tree stem growth and litterfall productivity did not respond to N fertilization in either of these Nrich forests, indicating amore » lack of N limitation to net primary productivity (NPP). In contrast, soil C concentrations increased significantly with N fertilization in both forests, leading to larger C stocks in fertilized plots. However, different soil C pools responded to N fertilization differently. Labile (low density) soil C fractions and live fine roots declined with fertilization, while mineral-associated soil C increased in both forests. Decreased soil CO2 fluxes in fertilized plots were correlated with smaller labile soil C pools in the lower elevation forest (R2 = 0.65, p\\0.05), and with lower live fine root biomass in the upper elevation forest (R2 = 0.90, p\\0.05). Our results indicate that soil C storage is sensitive to N deposition in tropical forests, even where plant productivity is not N-limited. The mineral-associated soil C pool has the potential to respond relatively quickly to N additions, and can drive increases in bulk soil C stocks in tropical forests.« less

The influence of soil organic matter chemistry and site/soil properties in predicting the decomposability of tundra soils

NASA Astrophysics Data System (ADS)

Matamala, R.; Jastrow, J. D.; Fan, Z.; Liang, C.; Calderon, F.; Michaelson, G.; Mishra, U.; Ping, C. L.

2017-12-01

With the increase in high latitude warming, there is a need to better understand the potential vulnerability of soil organic matter (SOM) stored in Arctic regions. In this study, we used mid infrared spectroscopy (MidIR) to determine the influence of soil chemistry and site properties in the short-term mineralization potential of SOM stored in tundra soils. Soils from the active and permafrost layers were collected from four tundra sites on the Coastal Plain, and Arctic Foothills of the North Slope of Alaska and were incubated for 60 days at a range of temperatures. Site and soil properties including acidic versus non-acidic tundra, lowland versus upland areas, total soil organic carbon (TOC) and total nitrogen (TN) concentrations, 60-day carbon mineralization potential (CMP), MidIR spectra and the chemical composition of the SOM stored in these soils were determined. Partial least squares (PLS) models for CMP versus MidIR spectra were produced upon splitting the dataset into site and soil properties categories. We found that SOM composition determined by MidIR spectroscopy was most effective in predicting CMP for tundra soils and it was most relevant for the active-layer mineral and upper permafrost soil horizons and/or soils with C concentrations of 10% or lower. Analysis of the factor loadings and standardized beta coefficients from the CMP PLS models indicated that spectral bands associated with clay contents, phenolic OH, aliphatic, silicates, carboxylic acids, and polysaccharides were influential for lower TOC soils, but these bands were less important for higher TOC soils. High TOC soils were influenced by a combination of other factors. Our results suggest that different factors affect the short-term CMP of SOM in tundra soils depending on the amount of TOC present. We show MidIR as a powerful tool for quickly and reasonably estimating the short-term CMP of tundra soils. Widespread application of MidIR measurements to already collected and archived tundra region soils could provide a quick and reliable assessment of the CMP of these soils, reduce the need for incubation studies, and contribute to upscaling and model benchmarking of SOM mineralization of tundra soils.

Results of the second national forest soil inventory in Germany - Interpretation of level and stock profiles for PCDD/F and PCB in terms of vegetation and humus type.

PubMed

Pandelova, Marchela; Henkelmann, Bernhard; Bussian, Bernd M; Schramm, Karl-Werner

2018-01-01

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were detected in 86 humic topsoil layers and in a subset of 11 randomly selected top mineral forest soils at the depths of 0-5cm and 5-10cm collected from different federal states of Germany. The distribution of these persistent organic pollutants (POPs) in humic topsoils with respect to vegetation cover (coniferous vs. deciduous vs. mixed), total organic carbon (TOC), altitude and latitude data was investigated. There is cross correlation between the contents and TOC while the correlation with latitude indicates higher abundances of POPs in central Germany where there is high population density accompanied with industrial activities. The calculated stocks suggest that humus type (mor, mull, or moder) in conjunction with forest type can explain the relative POPs abundances in different soil layers. Generally, humic topsoils show highest contents of POPs compare to the two mineral soils with a ratio of 100:10:1. However, the stock humic layers of coniferous stands contribute about 50% to the total stock, whereas at deciduous stands the stock is mainly located in the upper mineral soil layer (0-5cm). The soil-water distribution coefficients (Kd) were calculated to estimate the potential translocation in the different soil types. The Kd values vary among the PCBs and PCDD/Fs congeners and are most variable for humic topsoils. There is pronounced chemical abundance in the top mineral soils with increasing Kd and this points to non-water bound transport processes for superlipophilic compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

Persistence of soil organic matter in eroding versus depositional landform positions

USGS Publications Warehouse

Berhe, Asmeret Asefaw; Harden, Jennifer W.; Torn, Margaret S.; Kleber, Markus; Burton, Sarah D.; Harte, John

2012-01-01

Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in controlling storage and persistence of SOM in different types of eroding and depositional landform positions. By combining density fractionation with elemental and spectroscopic analyses, we showed that SOM in depositional settings is less transformed and better preserved than SOM in eroding landform positions. However, which environmental factors exert primary control on storage and persistence of SOM depended on the nature of the landform position considered. In an annual grassland watershed, protection of SOM by physical isolation inside aggregates and chemical association of organic matter (complexation) with soil minerals, as assessed by correlation with radiocarbon concentration, were more effective in the poorly drained, lowest-lying depositional landform positions, compared to well-drained landform positions in the upper parts of the watershed. Results of this study demonstrated that processes of soil erosion and deposition are important mechanisms of long-term OM stabilization.

Tundra fire disturbance homogonizes belowground food web structure, function and dynamics

NASA Astrophysics Data System (ADS)

Moore, J. C.; Pressler, Y.; Koltz, A.; Asmus, A.; Simpson, R.

2016-12-01

Tundra fires on Alaska's North Slope are on the rise due to increased lightning strikes since 2000. On July 16, 2007 lightning ignited the Anaktuvuk River fire, burning a 40-by-10 mile swath of tundra about 24 miles north of Toolik Field Station. The fire burned 401 square miles, was visible from space, and released more than 2.3 million tons of carbon into the atmosphere. A large amount of the organic layer of the soil was burned, changing the over all composition of the site and exposing deeper soil horizons. Due to fundamental transitions in soil characteristics and vegetation we hypothesized that the belowground food web community would be affected both in terms of biomass and location within the soil profile. Microbial biomass was reduced with burn severity. In the lower organic horizon there was a significant reduction in fungal biomass but we did not observe this effect in the upper organic soil. We did not observe a significant effect of burn severity on individual group biomass within higher trophic levels. Canonical Discriminant Analysis using the biomass estimates of the functional groups in the food webs found that the webs are becoming increasingly homogenized in the severely burned site compared to the moderately burned and unburned sites. The unburned soils differed significantly from soil at both burn sites; the greatest effects on food web structure were at the lower organic depth, whereas. We modeled the effects of the fire on soil organic matter processing rates and energy flow through the three food webs. The model estimated a decrease in C and N mineralization with fire severity, due in large part to the loss of organic material. While the organic horizon at the unburned site had 12 times greater C and N mineralization than the mineral soils, we observed little to no difference in C and N mineralization between the organic and mineral soil horizons in the moderately and severely burned sites. Our results show that the fire significantly altered the trophic structure of the soil food web, with loss of trophic complexity with increasing fire severity, which correlated strongly with C and N processing and food web stability.

Hydrologic regime controls soil phosphorus fluxes in restoration and undisturbed wetlands

USGS Publications Warehouse

Aldous, A.; McCormick, P.; Ferguson, C.; Graham, S.; Craft, C.

2005-01-01

Many wetland restoration projects occur on former agricultural soils that have a history of disturbance and fertilization, making them prone to phosphorus (P) release upon flooding. To study the relationship between P release and hydrologic regime, we collected soil cores from three restoration wetlands and three undisturbed wetlands around Upper Klamath Lake in southern Oregon, U.S.A. Soil cores were subjected to one of three hydrologic regimes - flooded, moist, and dry - for 7.5 weeks, and P fluxes were measured upon reflooding. Soils from restoration wetlands released P upon reflooding regardless of the hydrologic regime, with the greatest releases coming from soils that had been flooded or dried. Undisturbed wetland soils released P only after drying. Patterns in P release can be explained by a combination of physical and biological processes, including the release of iron-bound P due to anoxia in the flooded treatment and the mineralization of organic P under aerobic conditions in the dry treatment. Higher rates of soil P release from restoration wetland soils, particularly under flooded conditions, were associated with higher total P concentrations compared with undisturbed wetland soils. We conclude that maintaining moist soil is the means to minimize P release from recently flooded wetland soils. Alternatively, prolonged flooding provides a means of liberating excess labile P from former agricultural soils while minimizing continued organic P mineralization and soil subsidence. ?? 2005 Society for Ecological Restoration International.

Polynomial response of 2,4-D mineralization to temperature in soils at varying soil moisture contents, slope positions and depths.

PubMed

Shymko, Janna L; Farenhorst, Annemieke; Zvomuya, Francis

2011-01-01

The herbicide 2,4-D [2,4-(dichlorophenoxy) acetic acid] is a widely used broadleaf control agent in cereal production systems. Although 2,4-D soil-residual activity (half-lives) are typically less than 10 days, this herbicide also has as a short-term leaching potential due to its relatively weak retention by soil constituents. Herbicide residual effects and leaching are influenced by environmental variables such as soil moisture and temperature. The objective of this study was to determine impacts of these environmental variables on the magnitude and extent of 2,4-D mineralization in a cultivated undulating Manitoba prairie landscape. Microcosm incubation experiments were utilized to assess 2,4-D half-lives and total mineralization using a 4 × 4 × 3 × 2 factorial design (with soil temperature at 4 levels: 5, 10, 20 and 40°C; soil moisture at 4 levels: 60, 85, 110, 135 % of field capacity; slope position at 3 levels: upper-, mid- and lower-slopes; and soil depth at 2 levels: 0-5 cm and 5-15 cm). Half-lives (t(½)) varied from 3 days to 51 days with the total 2,4-D mineralization (M(T)) ranging from 5.8 to 50.9 %. The four-way interaction (temperature × moisture × slope × depth) significantly (p < 0.001) influenced both t(½) and M(T). Second-order polynomial equations best described the relations of temperature with t(½) and M(T) as was expected from a biological system. However, the interaction and variability of t(½) and M(T) among different temperatures, soil moistures, slope positions, and soil depth combinations indicates that the complex nature of these interacting factors should be considered when applying 2,4-D in agricultural fields and in utilizing these parameters in pesticide fate models.

The role of leaf cutter ants on soil organic carbon dynamics in a wet tropical forest

NASA Astrophysics Data System (ADS)

Schwendenmann, L.; Meredyth-Young, M.; Dierick, D.; Allen, M. F.; Harmon, T. C.; Oberbauer, S. F.; Rundel, P.; Trahan, N. A.; Zelikova, T. J.

2016-12-01

Tropical forest ecosystems play an important role in the global carbon (C) cycle. Neotropical forests are significantly influenced by leaf cutter ants (LCA) which are the most important herbivore in these systems. LCA cut fresh leaves and bring large amounts of plant biomass into their nests to grow their fungus gardens. The excavation and continual maintenance of their large nests modifies soil characteristics and biogeochemistry with direct and indirect impacts on soil organic carbon (SOC) dynamics. The aim of this study was to quantify the effects of LCA (Atta cephalotes) on soil C mineralization, carbon degrading enzymes (β-glucosidase and α-glucosidase), and labile soil C (hot water extractable carbon) across a 1 m soil depth profile and comparing between two different soils (residual and alluvial) and forest types (primary and secondary) in a wet tropical rainforest in Costa Rica. We hypothesized that C mineralization rates will be higher inside LCA nests due to continual input of fresh organic matter, as evidenced by higher microbial biomass and carbon degrading enzymes. Similarly, we expected more labile C inside nests. All soil C parameters were highly variable among sites and between nests and controls. Carbon mineralization rates ranged from 0.02 to 0.2 µmol C h-1 g soil-1 during the initial decay phase which lasted approximately 6 days during soil incubation. The highest respiration rates were measured in the top 20 cm of the primary forest residual soil. Contrary to our expectations, C mineralization rates were higher in control soils, where C degrading enzymes were in higher concentrations (around 250 µmol). The labile soil C concentrations were variable across sites (2-25 mg C g soil-1) and higher in the upper soil profiles, but no significant differences were found between controls and nests. Our results indicate greater heterogeneity inside the nests than previously expected. We explain our findings in terms of the removal of leaf and organic matter from the nest surface by LCA, which may have led to a reduction in available carbon substrate for microbial decomposition.

Oaks belowground: mycorrhizas, truffles, and small mammals

Treesearch

Jonathan Frank; Seth Barry; Joseph Madden; Darlene Southworth

2008-01-01

Oaks depend on hidden diversity belowground. Oregon white oaks (Quercus garryana) form ectomycorrhizas with more than 40 species of fungi at a 25-ha site. Several of the most common oak mycorrhizal fungi form hypogeous fruiting bodies or truffles in the upper layer of mineral soil. We collected 18 species of truffles associated with Oregon white...

Chemical features of soils in a natural forest of West Hungary

NASA Astrophysics Data System (ADS)

Hofmann, Eszter; Bidló, András

2015-04-01

The present research focuses on the chemical results of soils formed on miocene carbonate rocks in a natural forest of West Hungary. Soil profiles derived from the Szárhalom Forest, located near the Lake Fertő, next to the city of Sopron. Six soil profiles were opened and analysed in this area. In the field the following physical parameters were evaluated from the soil profiles: transition, structure, compactness, roots, skeletal percent, colour, physical assortment, concretion and soil defect. Laboratory analysis involved the measurement of acidity, particle distribution, carbonated lime content, humus content, ammonium lactate-acetic acid soluble phosphorus- and potassium content, potassium chloride soluble calcium- and magnesium content, ethylene-diamine-tetraacetic-acid (EDTA) and diethylene-triamine-pentaacetic-acid (DTPA) soluble copper-, iron-, manganese- and zinc contents. These soils formed under a hornbeam-oak forest climate mainly and under a beech forest climate diffusely. The location and climate of the sites forms a basis of the comparison of the soils with similar base rock. The formation of the acidic and humus-rich upper layer of the soil profiles is influenced by the mineral composition and the weathering of the rocks. X-ray diffraction (Philips P W3710/PW1050 type X-ray diffractometer), thermoanalytical measurements (Mettler Toledo TGA/DSC 1 type thermogravimeter) and ICP-OES (Thermo Scientific iCAP 7000 Series) were also carried out to determine the mineral composition of the soils and the content of heavy metals. The soil samples were collected with both traditional and undisturbed (using the Kubiena box) sampling methods to enable further micromorphological investigations as well. The research is supported by the "Agroclimate-2" (VKSZ_12-1-2013-0034) joint EU-national research project. Key words: Natural forest, Miocene limestone, Mineral composition, Thermal analysis, Micromorphology

Health risk assessment of potentially harmful elements and dietary minerals from vegetables irrigated with untreated wastewater, Pakistan.

PubMed

Zia, Munir H; Watts, Michael J; Niaz, Abid; Middleton, Daniel R S; Kim, Alexander W

2017-08-01

In the developing world, vegetables are commonly grown in suburban areas irrigated with untreated wastewater containing potentially harmful elements (PHEs). In Pakistan, there is no published work on the bioaccessibility aspect of PHEs and dietary minerals (DMs) in sewage-irrigated soil or the vegetables grown on such soils in Pakistan. Several industrial districts of Pakistan were selected for assessment of the risk associated with the ingestion of vegetables grown over sewage-irrigated soils. Both the total and bioaccessible fraction of PHEs (Cd, Co, Cr, Ni, and Pb) and DMs (Fe, Cu, Mn, Zn, Ca, Mg, and I) in soils and vegetable samples were measured. The concentrations of these PHEs and DMs in sewage-irrigated and control soils were below published upper threshold limits. However, compared to control soils, sewage irrigation over the years decreased soil pH (7.7 vs 8.1) and enhanced dissolved organic carbon (1.8 vs 0.8 %), which could enhance the phyto-availability of PHEs and DMs to crops. Of the PHEs and DMs, the highest transfer factor (soil to plant) was noted for Cd and Ca, respectively. Concentrations of PHEs in most of the sewage-irrigated vegetables were below the published upper threshold limits, except for Cd in the fruiting portion of eggplant and bell pepper (0.06-0.08 mg/kg Cd, dry weight) at three locations in Gujarat and Kasur districts. The bioaccessible fraction of PHEs can reduce the context of dietary intake measurements compared to total concentrations, but differences between both measurements were not significant for Cd. Since the soils of the sampled districts are not overly contaminated compared to control sites, vegetables grown over sewage-irrigated soils would provide an opportunity to harvest mineral-rich vegetables potentially providing consumers 62, 60, 12, 104, and 63 % higher dietary intake of Cu, Mn, Zn, Ca, and Mg, respectively. Based on Fe and vanadium correlations in vegetables, it is inferred that a significant proportion of total dietary Fe intake could be contributed by soil particles adhered to the consumable portion of vegetables. Faecal sterol ratios were used to identify and distinguish the source of faecal contamination in soils from Gujranwala, Gujarat, and Lahore districts, confirming the presence of human-derived sewage biomarkers at different stages of environmental alteration. A strong correlation of some metals with soil organic matter concentration was observed, but none with sewage biomarkers.

The impact of extreme environmental factors on the mineralization potential of the soil

NASA Astrophysics Data System (ADS)

Zinyakova, Natalia; Semenov, Vyacheslav

2016-04-01

Warming, drying, wetting are the prevalent disturbing natural impacts that affect the upper layers of uncultivated and arable soils. The effect of drying-wetting cycles act as a physiological stress for the soil microbial community and cause changes in its structure, the partial death or lysis of the microbial biomass. The mobilization of the SOM and the stabilization of the potentially mineralizable components lead to change of mineralization potential in the soil. To test the effects of different moisture regime on plant growth and soil biological properties, plot experiment with the gray forest soil including trials with plants (corn) and bare fallow was performed. Different regimes of soil moisture (conditionally optimal, relatively deficient soil moisture and repeated cycles of drying-wetting) were created. Control of soil moisture was taken every two or three days. Gas sampling was carried out using closed chambers. Soil samples were collected at the end of the pot experiment. The potentially mineralizable content of soil organic carbon (SOC) was measured by biokinetic method based on (1) aerobic incubation of soil samples under constant temperature and moisture conditions during 158 days, (2) quantitation of C-CO2, and (3) fitting of C-CO2 cumulative curve by a model of first-order kinetic. Total soil organic carbon was measured by Tyrin's wet chemical oxidation method. Permanent deficient moisture in the soil favored the preservation of potentially mineralizable SOC. Two repeated cycles of drying-wetting did not reduce the potentially mineralizable carbon content in comparison with control under optimal soil moisture during 90 days of experiment. The emission loss of C-CO2 from the soil with plants was 1.4-1.7 times higher than the decrease of potentially mineralizable SOC due to the contribution of root respiration. On the contrary, the decrease of potentially mineralized SOC in the soil without plants was 1.1-1.2 times larger than C-CO2 emissions from the soil as a result of stabilization processes. Thus, the alternation of drying-wetting cycles results in 1) the death of microbial biomass and recolonization of the soil microorganisms; 2) favors the splitting and degradation of soil aggregates, as well as the reaggregation and stabilization of aggregates; 3) contributes to the mobilization of the SOM and also 4) initiates the stabilization of the potentially mineralizable components. The effect of drying-wetting cycles is expressed not so much in the loss of the total soil organic carbon as in the degradation of the SOM quality with decreasing its mineralization potential. We can conclude that different soil moisture regimes lead to essential changes of mineralization potential in the gray forest soil. The amount of mineralization loss soil carbon via C-CO2 emission is directly associated with the decrease of potentially mineralizable carbon. Deficient moisture is a reason for temporarily sequestration of SOC potentially mineralizable under optimal moisture. This work was supported by RSF. Project number 14-14-00625

Water chemistry at Snowshoe Mountain, Colorado: mixed processes in a common bedrock

USGS Publications Warehouse

Hoch, A.R.; Reddy, M.M.

2001-01-01

At Snowshoe Mountain the primary bedrock is quite homogeneous, but weathering processes vary as waters moves through the soils, vadose zone and phreatic zone of the subsurface. In the thin soil, physical degradation of tuff facilitates preferential dissolution of potassium ion from glass within the rock matrix, while other silicate minerals remain unaltered. In the vadose zone, in the upper few meters of fractured bedrock, dilute water infiltrates during spring snowmelt and summer storms, leading to preferential dissolution of augite exposed on fracture surfaces. Deeper yet, in the phreatic zone of the fractured bedrock, Pleistocene calcite fracture fillings dissolve, and dioctahedral and trioctahedral clays form as penetrative weathering alters feldspar and pyroxene. Alkalinity is generated and silica concentrations are buffered by mineral alteration reactions.

Field trip guidebook on environmental impact of clays along the upper Texas coast

NASA Technical Reports Server (NTRS)

Garcia, Theron D.; Ming, Douglas W.; Tuck, Lisa Kay

1991-01-01

The field trip was prepared to provide an opportunity to see first hand some the environmental hazards associated with clays in the Houston, Texas area. Because of the very high clay content in area soils and underlying Beaumont Formation clay, Houston is a fitting location to host the Clay Mineral Society. Examinations were made of (1) expansive soils, (2) subsidence and surface faulting, and (3) a landfill located southeast of Houston at the Gulf Coast Waste Disposal Authority where clay is part of the liner material.

Deep Soil Carbon Influenced Following Forest Organic Matter Manipulation In A Loblolly Pine Plantation In The Southeastern United States

NASA Astrophysics Data System (ADS)

Hatten, J. A.; Mack, J.; Sucre, E.; Leggett, Z.; Roberts, S.; Dewey, J.

2013-12-01

Forest harvest residues and forest floor materials are significant sources of mineral soil organic matter and nutrients for regenerating and establishing forests. Harvest residues in particular are occasionally removed, piled, or burned following harvesting. Weyerhaeuser Company established an experimental study to evaluate the effect of the removal and addition of harvest residual and forest-floor on site productivity and soil carbon. This study was installed in a loblolly pine plantation near Millport, Alabama, USA on the Upper Gulf Coastal Plain to test both extremes from complete removal of harvest residues and forest floor to doubling of these materials. This study has been continuously monitored since its establishment in 1994. We have examined the effects of varying forest floor levels on the biomass, soil carbon content, and soil carbon composition in the context of these management activities. Above- and below-ground productivity, soil moisture, soil temperature, and nutrient dynamics have been related to soil organic carbon in mineral soil, size/density fractionation, and lignin and cutin biomarkers from the cupric oxide (CuO)-oxidation technique. We have found that while removing litter and harvest residues has little effect on biomass production and soil carbon, importing litter and harvest residues increases forest productivity and soil carbon content. Interestingly, increased carbon was observed in all depths assessed (O horizon, 0-20, 20-40, and 40-60cm) suggesting that this practice may sequester organic carbon in deep soil horizons. Our biomarker analysis indicated that importing litter and harvest residues increased relative contributions from above ground sources at the 20-40cm depth and increased relative contributions from belowground sources at the 40-60cm depth. These results suggest that organic matter manipulations in managed forests can have significant effects on deep soil carbon that may be resistant to mineralization or the effects of other perturbations such as climate change.

Soil biochemical properties of grassland ecosystems under anthropogenic emission of nitrogen compounds

NASA Astrophysics Data System (ADS)

Kudrevatykh, Irina; Ivashchenko, Kristina; Ananyeva, Nadezhda

2016-04-01

Inflow of pollutants in terrestrial ecosystems nowadays increases dramatically, that might be led to disturbance of natural biogeochemical cycles and landscapes structure. Production of nitrogen fertilizers is one of the air pollution sources, namely by nitrogen compounds (NH4+, NO3-, NO2-). Air pollution by nitrogen compounds of terrestrial ecosystems might be affected on soil biochemical properties, which results increasing mineral nitrogen content in soil, changing soil P/N and Al/Ca ratios, and, finally, the deterioration of soil microbial community functioning. The research is focused on the assessment of anthropogenic emission of nitrogen compounds on soil properties of grassland ecosystems in European Russia. Soil samples (Voronic Chernozem Pachic, upper 10 cm mineral layer, totally 10) were taken from grassland ecosystem: near (5-10 m) nitrogen fertilizer factory (NFF), and far from it (20-30 km, served as a control) in Tula region. In soil samples the NH4+ and NO3- (Kudeyarov's photocolorimetric method), P, Ca, Al (X-ray fluorescence method) contents were measured. Soil microbial biomass carbon (Cmic) was analyzed by substrate-induced respiration method. Soil microbial respiration (MR) was assessed by CO2 rate production. Soil microbial metabolic quotient (qCO2) was calculated as MR/Cmic ratio. Near NFF the soil ammonium and nitrate nitrogen contents were a strongly varied, variation coefficient (CV) was 42 and 86This study was supported by Russian Foundation of Basic Research Grant No. 14-04-00098, 15-44-03220, 15-04-00915.

Long term changes in atmospheric N and S throughfall deposition and effects on soil solution chemistry in a Scots pine forest in the Netherlands.

PubMed

Boxman, Andries W; Peters, Roy C J H; Roelofs, Jan G M

2008-12-01

In a Scots pine forest the throughfall deposition and the chemical composition of the soil solution was monitored since 1984. (Inter)national legislation measures led to a reduction of the deposition of nitrogen and sulphur. The deposition of sulphur has decreased by approximately 65%. The total mineral-nitrogen deposition has decreased by ca. 25%, which is mainly due to a reduction in ammonium-N deposition (-40%), since nitrate-N deposition has increased (+50%). The nitrogen concentration in the upper mineral soil solution at 10 cm depth has decreased, leading to an improved nutritional balance, which may result in improved tree vitality. In the drainage water at 90 cm depth the fluxes of NO3(-) and SO4(2-) have decreased, resulting in a reduced leeching of accompanying base cations, thus preserving nutrients in the ecosystem. It may take still several years, however, before this will meet the prerequisite of a sustainable ecosystem.

Mineralization of organic-matter labile fragments in the humus-accumulative horizon of soddy-podzolic soil

NASA Astrophysics Data System (ADS)

Trofimov, S. Ya.; Lazarev, A. S.; Fokin, A. D.

2012-12-01

The mineralization rate of the 14C-labeled organic matter (OM) in the humus-accumulative AE horizon of a soddy-podzolic soil was determined in a laboratory experiment. The labeling was performed in a field experiment when microamounts of 14C-labeled glucose, glycine, and uracil were added to tree waste in sacks embedded in the upper layer of the forest litter. Samples containing 14C were taken from the AE horizon (above which the sacks with the labeled material were placed) 7 and 20 months after the beginning of the experiment. The soil samples were wetted to a water content corresponding to ˜80% of the total water capacity and placed in hermetic vessels containing vials with a periodically renewed alkali solution. The incubation was performed at room temperature for 3.5 months; the alkali solutions in the vials were replaced and titrated 12 times during this period. Mineralization curves were plotted from the amounts of carbon dioxide absorbed by a 0.3 N NaOH solution, which were calculated for each time interval; its 14C content was determined by the scintillation method. The experimental treatments also included the determination of the OM mineralization rate in material from the AE horizon pretreated with a heavy liquid or a heavy liquid and a 0.1 N NaOH solution. The differences between the mineralization rates of the labeled organic matter applied to the soil in the form of glucose, glycine, and uracil under the field conditions after the interaction for 7 and 20 months were revealed. The changes in the mineralization rate after the successive extraction of the labile organic matter with a heavy liquid and a 0.1 N NaOH solution were studied. It was shown that the transformation of the labeled low-molecular-weight organic compounds in the soil over 20 months included their strong inclusion into the humus composition, which was confirmed by the similar values of the mineralization constants of the native and 14C-labeled OM. In addition, the treatments with the heavy liquid or the heavy liquid and the NaOH solution had almost identical effects on the mineralization of the native and 14C-labeled OM. The mineralization constants of the native and 14C-labeled OM in the samples taken after 7 months of the field experiment differed significantly.

Viability of litter-stored Quercus falcata Michx. acorns after simulated prescribed winter burns

Treesearch

Michael D. Cain; Michael G. Shelton

1998-01-01

Partially stratified (11 days) southern red oak (Quercus falcata Michx.) acorns were placed at three depths in a reconstructed forest floor and subjected to simulated prescribed winter burns. Within the forest floor, acorns were placed within the L layer, at the upper-F/ lower-F interface, and at the lower-F/mineral-soil interface. Winds for a...

The effect of hydraulic lift on organic matter decomposition, soil nitrogen cycling, and nitrogen acquisition by a grass species.

PubMed

Armas, Cristina; Kim, John H; Bleby, Timothy M; Jackson, Robert B

2012-01-01

Hydraulic lift (HL) is the passive movement of water through plant roots, driven by gradients in water potential. The greater soil-water availability resulting from HL may in principle lead to higher plant nutrient uptake, but the evidence for this hypothesis is not universally supported by current experiments. We grew a grass species common in North America in two-layer pots with three treatments: (1) the lower layer watered, the upper one unwatered (HL), (2) both layers watered (W), and (3) the lower layer watered, the upper one unwatered, but with continuous light 24 h a day to limit HL (no-HL). We inserted ingrowth cores filled with enriched-nitrogen organic matter ((15)N-OM) in the upper layer and tested whether decomposition, mineralization and uptake of (15)N were higher in plants performing HL than in plants without HL. Soils in the upper layer were significantly wetter in the HL treatment than in the no-HL treatment. Decomposition rates were similar in the W and HL treatments and lower in no-HL. On average, the concentration of NH(4)(+)-N in ingrowth cores was highest in the W treatment, and NO(3)(-)-N concentrations were highest in the no-HL treatment, with HL having intermediate values for both, suggesting differential mineralization of organic N among treatments. Aboveground biomass, leaf (15)N contents and the (15)N uptake in aboveground tissues were higher in W and HL than in no-HL, indicating higher nutrient uptake and improved N status of plants performing HL. However, there were no differences in total root nitrogen content or (15)N uptake by roots, indicating that HL affected plant allocation of acquired N to photosynthetic tissues. Our evidence for the role of HL in organic matter decomposition and nutrient cycling suggests that HL could have positive effects on plant nutrient dynamics and nutrient turnover.

Assessing Impacts of 20 yr Old Miscanthus on Soil Organic Carbon Quality

NASA Astrophysics Data System (ADS)

Hu, Yaxian; Schäfer, Gerhard; Kuhn, Nikolaus

2015-04-01

The use of biomass as a renewable energy source has become increasingly popular in Upper Rhine Region to meet the demand for renewable energy. Miscanthus is one of the most favorite biofuel crops, due to its long life and large yields, as well as low energy and fertilizer inputs. However, current research on Miscanthus is mostly focused on the techniques and economics to produce biofuel or the impacts of side products such as ash and sulfur emissions to human health. Research on the potential impacts of Miscanthus onto soil quality, especially carbon quality after long-term adoption, is very limited. Some positive benefits, such as sequestrating organic carbon, have been repeatedly reported in previous research. Yet the quality of newly sequestrated organic carbon and its potential impacts onto global carbon cycling remain unclear. To fully account for the risks and benefits of Miscanthus, it is required to investigate the quality as well as the potential CO2 emissions of soil organic carbon on Miscanthus fields. As a part of the Interreg Project to assess the environmental impacts of biomass production in the Upper Rhine Region, this study aims to evaluate the carbon quality and the potential CO2 emissions after long-term Miscanthus adoption. Soils were sampled at 0-10, 10-40, 40-70, and 70-100 cm depths on three Miscanthus fields with up to 20 years of cultivation in Ammerzwiller France, Münchenstein Switzerland, and Farnsburg Switzerland. Soil texture, pH, organic carbon and nitrogen content were measured for each sampled layer. Topsoils of 0-10 cm and subsoils of 10-40 cm were also incubated for 40 days to determine the mineralization potential of the soil organic matter. Our results show that: 1) only in top soils of 0-10 cm, the 20 year old Miscanthus field has significantly higher soil organic carbon concentrations, than the control site. No significant differences were observed in deeper soil layers. Similar tendencies were also observed for organic nitrogen content as well C/N ratios. This indicates that the positive benefits of Miscanthus in sequestrating organic carbon and improving soil quality are probably only effective in top soils. 2) Soils from the 20 years old Miscanthus fields produced significantly more CO2 than the control site, suggesting the great susceptibility of organic carbon on Miscanthus fields to mineralization. Overall, our results indicate a potentially additional contribution of Miscanthus fields to atmospheric CO2 compared to reference soils, cautioning the widespread adoption of Miscanthus. Consequently, further studies aiming at a full emission balance are required to assess the overall environmental impacts of biomass production in the Upper Rhine Region.

Hydrogeomorphic Classification of Wetlands on Mt. Desert Island, Maine, Including Hydrologic Susceptibility Factors for Wetlands in Acadia National Park

USGS Publications Warehouse

Nielsen, Martha G.

2006-01-01

The U.S. Geological Survey, in cooperation with the National Park Service, developed a hydrogeomorphic (HGM) classification system for wetlands greater than 0.4 hectares (ha) on Mt. Desert Island, Maine, and applied this classification using map-scale data to more than 1,200 mapped wetland units on the island. In addition, two hydrologic susceptibility factors were defined for a subset of these wetlands, using 11 variables derived from landscape-scale characteristics of the catchment areas of these wetlands. The hydrologic susceptibility factors, one related to the potential hydrologic pathways for contaminants and the other to the susceptibility of wetlands to disruptions in water supply from projected future changes in climate, were used to indicate which wetlands (greater than 1 ha) in Acadia National Park (ANP) may warrant further investigation or monitoring. The HGM classification system consists of 13 categories: Riverine-Upper Perennial, Riverine-Nonperennial, Riverine- Tidal, Depressional-Closed, Depressional-Semiclosed, Depressional-Open, Depressional-No Ground-Water Input, Mineral Soil Flat, Organic Soil Flat, Tidal Fringe, Lacustrine Fringe, Slope, and Hilltop/Upper Hillslope. A dichotomous key was developed to aid in the classification of wetlands. The National Wetland Inventory maps produced by the U.S. Fish and Wildlife Service provided the wetland mapping units used for this classification. On the basis of topographic map information and geographic information system (GIS) layers at a scale of 1:24,000 or larger, 1,202 wetland units were assigned a preliminary HGM classification. Two of the 13 HGM classes (Riverine-Tidal and Depressional-No Ground-Water Input) were not assigned to any wetlands because criteria for determining those classes are not available at that map scale, and must be determined by more site-specific information. Of the 1,202 wetland polygons classified, which cover 1,830 ha in ANP, 327 were classified as Slope, 258 were Depressional (Open, Semiclosed, and Closed), 231 were Riverine (Upper Perennial and Nonperennial), 210 were Soil Flat (Mineral and Organic), 68 were Lacustrine Fringe, 51 were Tidal Fringe, 22 were Hilltop/Upper Hillslope, and another 35 were small open water bodies. Most small, isolated wetlands classified on the island are Slope wetlands. The least common, Hilltop/Upper Hillslope wetlands, only occur on a few hilltops and shoulders of hills and mountains. Large wetland complexes generally consist of groups of Depressional wetlands and Mineral Soil Flat or Organic Soil Flat wetlands, often with fringing Slope wetlands at their edges and Riverine wetlands near streams flowing through them. The two analyses of wetland hydrologic susceptibility on Mt. Desert Island were applied to 186 wetlands located partially or entirely within ANP. These analyses were conducted using individually mapped catchments for each wetland. The 186 wetlands were aggregated from the original 1,202 mapped wetland polygons on the basis of their HGM classes. Landscape-level hydrologic, geomorphic, and soil variables were defined for the catchments of the wetlands, and transformed into scaled scores from 0 to 10 for each variable. The variables included area of the wetland, area of the catchment, area of the wetland divided by the area of the catchment, the average topographic slope of the catchment, the amount of the catchment where bedrock crops out with no soil cover or excessively thin soil cover, the amount of storage (in lakes and wetlands) in the catchment, the topographic relief of the catchment, the amount of clay-rich soil in the catchment, the amount of manmade impervious surface, whether the wetland had a stream inflow, and whether the wetland had a hydraulic connection to a lake or estuary. These data were determined using a GIS and data layers mapped at a scale of 1:24,000 or larger. These landscape variables were combined in different ways for the two hydrologic susceptibility fact

Nitrogen dynamics across silvicultural canopy gaps in young forests of western Oregon

USGS Publications Warehouse

Thiel, A.L.; Perakis, S.S.

2009-01-01

Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. The effect of gap creation on available nitrogen (N) is of concern to managers because N is often a limiting nutrient in Pacific Northwest forests. We investigated patterns of N availability in the forest floor and upper mineral soil (0-10 cm) across 6-8-year-old silvicultural canopy gaps in three 50-70-year-old Douglas-fir forests spanning a wide range of soil N capital in the Coast Range and Cascade Mountains of western Oregon. We used extractable ammonium (NH4+) and nitrate (NO3-) pools, net N mineralization and nitrification rates, and NH4+ and NO3- ion exchange resin (IER) concentrations to quantify N availability along north-south transects run through the centers of 0.4 and 0.1 ha gaps. In addition, we measured several factors known to influence N availability, including litterfall, moisture, temperature, and decomposition rates. In general, gap-forest differences in N availability were more pronounced in the mineral soil than in the forest floor. Mineral soil extractable NH4+ and NO3- pools, net N mineralization and nitrification rates, and NH4+ and NO3- IER concentrations were all significantly elevated in gaps relative to adjacent forest, and in several cases exhibited significantly greater spatial variability in gaps than forest. Nitrogen availability along the edges of gaps more often resembled levels in the adjacent forest than in gap centers. For the majority of response variables, there were no significant differences between northern and southern transect positions, nor between 0.4 and 0.1 ha gaps. Forest floor and mineral soil gravimetric percent moisture and temperature showed few differences along transects, while litterfall carbon (C) inputs and litterfall C:N ratios in gaps were significantly lower than in the adjacent forest. Reciprocal transfer incubations of mineral soil samples between gap and forest positions revealed that soil originating from gaps had greater net nitrification rates than forest samples, regardless of incubation environment. Overall, our results suggest that increased N availability in 6-8-year-old silvicultural gaps in young western Oregon forests may be due more to the quality and quantity of litterfall inputs resulting from early-seral species colonizing gaps than by changes in temperature and moisture conditions caused by gap creation.

Fire Ecology of Seeds from Rubus Spp.: A Competitor During Natural Pine Regeneration

Treesearch

Michael D. Cain; Michael G. Shelton

1999-01-01

Air-dried blackbeny (Rubus spp.) fruits were placed at three depths in a reconstructed forest floor and subjected to a simulated prescribed summer bum. Within the forest floor, fruits were placed on the L layer, at the upper-F/lower-F interface, and at the lower-F/mineral-soil interface. Wind for a headfire was generated by electric boxfans....

Modeling hydrological controls on vegetation distribution across topography in Seward Peninsula, Alaska

NASA Astrophysics Data System (ADS)

Mekonnen, Z. A.; Riley, W. J.; Grant, R. F.; Salmon, V. G.; Iversen, C. M.; Biraud, S.; Breen, A. L.

2017-12-01

Observed changes in vegetation affect carbon and nutrient cycles in diverse landscapes of northern ecosystems. These changes can be affected by topography and landscape hydrology. We applied a coupled transect version of the ecosystem model ecosys in a landscape underlain by impermeable permafrost at Kougarok, Alaska to examine hydrological controls on watershed-scale vegetation distributions. Our preliminary results indicate strong relationships between vegetation distribution and soil physical and hydraulic properties that control water, nutrients, and energy flows across the hillslope. Modeled differences in aboveground biomass across the Kougarok hillslope had a good agreement (R2 0.80) with preliminary biomass measurements from the NGEE-Arctic project in summer 2016. Low soil water content from shallower soil depth and lateral flow of water and nutrients in the upper slope position of the hillslope resulted in water stress and low N mineralization for plants with deeper roots. The middle slope position had intermediate soil moisture from deeper soil and higher N mineralization that favoured fast-growing and deep-rooted plants. The gentle slope and deeper soil in the lower slope position resulted in saturated soil, thus reduced O2 for microbes, hence favouring plants with higher root porosity. Earth system models that do not account for the underlying mechanisms of surface and sub-surface flows of water, nutrients, and energy may not predict these types of dynamics in Arctic ecosystems.

Understanding the role of soil erosion on co2-c loss using (13)c isotopic signatures in abandoned Mediterranean agricultural land.

PubMed

Novara, Agata; Keesstra, Saskia; Cerdà, Artemio; Pereira, Paulo; Gristina, Luciano

2016-04-15

Understanding soil water erosion processes is essential to evaluate the redistribution of soil organic carbon (SOC) within a landscape and is fundamental to assess the role of soil erosion in the global carbon (C) budget. The main aim of this study was to estimate the C redistribution and losses using (13)C natural abundance. Carbon losses in soil sediment, dissolved organic carbon (DOC) and CO2 emission were determined. Four bounded parallel plots were installed on a 10% slope. In the upper part of the plots, C3soil was replaced with C4soil. The SOC and δ(13)C were measured after 145.2mm rainfall in the upper (2m far from C4strip), middle (4m far from C4strip) lower (6m far from C4strip) trams of the plot and in the sediments collected in the Gerlach collector at the lower part of the plot. A laboratory incubation experiment was performed to evaluate the CO2 emission rate of soils in each area. OC was mainly lost in the sediments as 2.08g(-)(2) of C was lost after 145.2mm rainfall. DOC losses were only 5.61% of off-site OC loss. Three months after the beginning of the experiment, 15.90% of SOC in the upper tram of the plot had a C4 origin. The C4-SOC content decreased along the 6m length of the plot, and in the sediments collected by the Gerlach collector. CO2 emission rate was high in the upper plot tram due to the high SOC content. The discrimination of CO2 in C3 and C4 portion permitted to increase our level of understanding on the stability of SOC and its resilience to decomposition. The transport of sediments along the plot increased SOC mineralization by 43%. Our study underlined the impact of rainfall in C losses in soil and water in abandoned Mediterranean agriculture fields and the consequent implications on the C balance. Copyright © 2016 Elsevier B.V. All rights reserved.

Lack of bedrock grain size influence on the soil production rate

NASA Astrophysics Data System (ADS)

Gontier, Adrien; Rihs, Sophie; Chabaux, Francois; Lemarchand, Damien; Pelt, Eric; Turpault, Marie-Pierre

2015-10-01

Our study deals with the part played by bedrock grain size on soil formation rates. U- and Th-series disequilibria were measured in two soil profiles developed from two different facies of the same bedrock, i.e., fine and coarse grain size granites, in the geomorphically flat landscape of the experimental Breuil-Chenue forest site, Morvan, France. The U- and Th-series disequilibria of soil layers and the inferred soil formation rate (1-2 mm ky-1) are nearly identical along the two profiles despite differences in bedrock grain size, variable weathering states and a significant redistribution of U and Th from the uppermost soil layers. This indicates that the soil production rate is more affected by regional geomorphology than by the underlying bedrock texture. Such a production rate inferred from residual soil minerals integrated over the age of the soil is consistent with the flat and slowly eroding geomorphic landscape of the study site. It also compares well to the rate inferred from dissolved solutes integrated over the shorter time scale of solute transport from granitic and basaltic watersheds under similar climates. However, it is significantly lower than the denudation or soil formation rates previously reported from either cosmogenic isotope or U-series measurements from similar climates and lithologies. Our results highlight the particularly low soil production rates of flat terrains in temperate climates. Moreover, they provide evidence that the reactions of mineral weathering actually take place in horizons deeper than 1 m, while a chemical steady state of both concentrations and U-series disequilibria is established in the upper most soil layers, i.e., above ∼70 cm depth. In such cases, the use of soil surface horizons for determining weathering rates is precluded and illustrates the need to focus instead on the deepest soil horizons.

Assessment of soil calcium status in red spruce forests in the northeastern United States

USGS Publications Warehouse

Lawrence, G.B.; David, M.B.; Bailey, S.W.; Shortle, W.C.

1997-01-01

Long-term changes in concentrations of available Ca in soils of red spruce forests have been documented, but remaining questions about the magnitude and regional extent of these changes have precluded an assessment of the current and future status of soil Ca. To address this problem, soil samples were collected in 1992-93 from 12 sites in New York, Vermont, New Hampshire, and Maine to provide additional data necessary to synthesize all available research results on soil Ca in red spruce forests. Sites were chosen to encompass the range of environmental conditions experienced by red spruce. Concentrations of exchangeable Ca ranged from 2.13 to 21.6 cmol(c) kg-1 in the Oa horizon, and from 0.11 to 0.68 cmol(c) kg-1 in the upper 10 cm of the B horizon. These measurements expanded the range of exchangeable Ca reported in the literature for both horizons in northeastern red spruce forests. Exchangeable Ca was the largest Ca fraction in the forest floor at most sites (92% of acid-extractable Ca), but mineral Ca was the largest fraction at the three sites that also had the highest mineral-matter concentrations. The primary factor causing variability in Ca concentrations among sites was the mineralogy of parent material, but exchangeable concentrations in the B horizon of all sites were probably reduced by acidic deposition. Because the majority of Ca in the forest floor is in a readily leachable form, and Ca inputs to the forest floor from the mineral soil and atmospheric deposition have been decreasing in recent decades, the previously documented decreases in Ca concentrations in the forest floor over previous decades may extend into the future.

Factors Controlling Pre-Columbian and Early Historic Maize Productivity in the American Southwest, Part 2: The Chaco Halo, Mesa Verde, Pajarito Plateau/Bandelier, and Zuni Archaeological Regions

USGS Publications Warehouse

Benson, L.V.

2011-01-01

Chemical and nutrient analyses of 471 soil samples from 161 sites within four archaeological regions (Pajarito Plateau/Bandelier, Zuni, Mesa Verde, and the Chaco Halo) were combined with historical climate data in order to evaluate the agricultural productivity of each region. In addition, maize productivity and field-life calculations were performed using organic-nitrogen (N) values from the upper 50 cm of soil in each region and a range (1-3%/year) of N-mineralization rates. The endmember values of this range were assumed representative of dry and wet climate states. With respect to precipitation and heat, the Pajarito Plateau area has excellent agricultural potential; the agricultural potentials of the Zuni and Mesa Verde regions are good; and the agricultural potential of the Chaco Halo is poor. Calculations of N mineralization and field life indicate that Morfield Valley in Mesa Verde should be able to provide 10 bu/ac of maize for decades (without the addition of N) when organic N-mineralization rates exceed 2%. Productivity and field-life potential decrease in the following order: Zuni, Mesa Verde, Bandelier, Chaco Halo. The Chaco Halo is very unproductive; e. g., 10 bushels per acre can be achieved within the Halo only from soils having the highest organic N concentration (third quartile) and which undergo the highest rate (3%) of N mineralization. ?? 2010 US Government.

Mechanisms of soil degradation and consequences for carbon stocks on Tibetan grasslands

NASA Astrophysics Data System (ADS)

Kuzyakov, Yakov; Schleuss, Per-Marten; Miehe, Georg; Heitkamp, Felix; Sebeer, Elke; Spielvogel, Sandra; Xu, Xingliang; Guggenberger, Georg

2016-04-01

Tibetan grasslands provide tremendous sinks for carbon (C) and represent important grazing ground. Strong degradation - the destroying the upper root-mat/soil horizon of Kobresia pastures, has dramatic consequences for soil organic carbon (SOC) and nutrient storage. To demonstrate specific degradation patterns and elucidate mechanisms, as well as to assess consequences for SOC storage, we investigated a sequence of six degradation stages common over the whole Kobresia ecosystem. The soil degradation sequence consists of following mechanisms: Overgrazing and trampling by livestock provide the prerequisite for grassland degradation as both (a) cause plant dying, (b) reduce grassland recovery and (c) destroy protective Kobresia root-mats. These anthropogenic induced processes are amplified by naturally occurring degradation in harsh climate. The frequently repeated soil moisture and temperature fluctuations induce volume changes and tensions leading to polygonal cracking of the root mats. Then the plants die and erosion gradually extend the surface cracks. Soil erosion cause a high SOC loss from the upper horizons (0-10 cm: ~5.1 kg C m-2), whereas SOC loss beneath the surface cracks is caused by both, decreasing root C-input and SOC mineralization (SOC losses by mineralization: ~2.5 kg C m-2). Root biomass decreases with degradation and indicated lower C input. The negative δ13C shift of SOC reflects intensive decomposition and corresponds to a relative enrichment of 13C depleted lignin components. We conclude that the combined effects of overgrazing and harsh climate reduce root C input, increase SOC decomposition and initiate erosion leading to SOC loss up to 70% of intact soil (0-30 cm: ~7.6 kg C m-2). Consequently, a high amount of C is released back to the atmosphere as CO2, or is deposited in depressions and river beds creating a potential source of N2O and CH4. Concluding, anthropogenically induced overgrazing makes the Kobresia root-mat sensitive to natural degradation processes and lead to strong up to complete destroying of soils and so, of pastures ground and ecosystems on Tibetan plateau.

Effect of O horizon and Forest Harvest Residue Manipulations on Soil Organic Matter Content and Composition of a Loblolly Pine Plantation in the Southeastern United States

NASA Astrophysics Data System (ADS)

Hatten, J.; Mack, J.; Dewey, J.; Sucre, E.; Leggett, Z.

2012-04-01

Forest harvest residues and forest floor materials are significant sources of mineral soil organic matter and nutrients for regenerating and establishing forests. Harvest residues in particular are occasionally removed, piled, or burned following harvesting. While the forest floor is never purposely removed during operational harvesting and site preparation, they could become in high demand as bioenergy markets develop. Weyerhaeuser Company established an experimental study to evaluate the effect of forest-floor manipulation on site productivity and soil carbon. This study was installed in a loblolly pine plantation near Millport, Alabama, USA on the Upper Gulf Coastal Plain to test both extremes from complete removal of harvest residues and forest floor to doubling of these materials. This study has been continuously monitored since its establishment in 1994. We have examined the effects of varying forest floor levels on the biomass, soil carbon content, and soil carbon composition in the context of these management activities. Above- and below-ground productivity, soil moisture, soil temperature, and nutrient dynamics have been related to soil organic carbon in mineral soil size/density fractionation and lignin and cutin biomarkers from the cupric oxide (CuO) oxidation technique. We have found that while removing litter and harvest residues has little effect on biomass production and soil carbon, importing litter and harvest residues increases forest productivity and soil carbon content. Interestingly, increased carbon was observed in all depths assessed (O horizon, 0-20, 20-40, and 40-60cm) suggesting that this practice may sequester organic carbon in deep soil horizons. Our biomarker analysis indicated that importing litter and harvest residues increased relative contributions from above ground sources at the 20-40cm depth and increased relative contributions from belowground sources at the 40-60cm depth. These results suggest that organic matter manipulations in managed forests can have significant effects on deep soil carbon that may be resistant to mineralization or the effects of other perturbations such as climate change.

The role of the upper tidal estuary in wetland blue carbon storage and flux

USGS Publications Warehouse

Krauss, Ken W.; Noe, Gregory B.; Duberstein, Jamie A.; Conner, William H.; Stagg, Camille L.; Cormier, Nicole; Jones, Miriam C.; Bernhardt, Christopher E.; Lockaby, B. Graeme; From, Andrew S.; Doyle, Thomas W.; Day, Richard H.; Ensign, Scott H.; Pierfelice, Katherine N.; Hupp, Cliff R.; Chow, Alex T.; Whitbeck, Julie L.

2018-01-01

Carbon (C) standing stocks, C mass balance, and soil C burial in tidal freshwater forested wetlands (TFFW) and TFFW transitioning to low‐salinity marshes along the upper estuary are not typically included in “blue carbon” accounting, but may represent a significant C sink. Results from two salinity transects along the tidal Waccamaw and Savannah rivers of the US Atlantic Coast show total C standing stocks were 321‐1264 Mg C ha‐1 among all sites, generally shifting to greater soil storage as salinity increased. Carbon mass balance inputs (litterfall, woody growth, herbaceous growth, root growth, surface accumulation) minus C outputs (surface litter and root decomposition, gaseous C) over a period of up to 11 years were 340‐900 g C m‐2 yr‐1. Soil C burial was variable (7‐337 g C m‐2 yr‐1), and lateral C export was estimated as C mass balance minus soil C burial as 267‐849 g C m‐2yr‐1. This represents a large amount of C export to support aquatic biogeochemical transformations. Despite reduced C persistence within emergent vegetation, decomposition of organic matter, and higher lateral C export, total C storage increased as forests converted to marsh with salinization. These tidal river wetlands exhibited high N mineralization in salinity‐stressed forested sites and considerable P mineralization in low salinity marshes. Large C standing stocks and rates of C sequestration suggest that TFFW and oligohaline marshes are considerably important globally to coastal C dynamics and in facilitating energy transformations in areas of the world in which they occur.

Transformation of ecofunctional parameters of soil microbial cenoses in clearings for power transmission lines in Central Siberia

NASA Astrophysics Data System (ADS)

Bogorodskaya, A. V.; Ponomareva, T. V.; Efimov, D. Yu.; Shishikin, A. S.

2017-06-01

Changes in soil microbial processes and phytocenotic parameters were studied in clearings made for power transmission lines in the subtaiga and southern taiga of Central Siberia. In these clearings, secondary meadow communities play the main environmental role. The substitution of meadow vegetation for forest vegetation, the increase in the phytomass by 40-120%, and the transformation of the hydrothermic regime in the clearings led to the intensification of the humus-accumulative process, growth of the humus content, reduction in acidity and oligotrophy of the upper horizons in the gray soils of the meadow communities, and more active microbial mineralization of organic matter. In the humus horizon of the soils under meadows, the microbial biomass (Cmicr) increased by 20-90%, and the intensity of basal respiration became higher by 60-90%. The values of the microbial metabolic quotient were also higher in these soils than in the soils under the native forests. In the 0- to 50-cm layer of the gray soils under the meadows, the total Cmicr reserves were 35-45% greater and amounted to 230-320 g/m3; the total microbial production of CO2 was 1.5-2 times higher than that in the soil of the adjacent forest and reached 770-840 mg CO2-C/m3 h. The predominance of mineralization processes in the soils under meadows in the clearings reflected changes in edaphic and trophic conditions of the soils and testified to an active inclusion of the herb falloff into the biological cycle.

Recovery of carbon and nutrient pools in a northern forested wetland 11 years after harvesting and site preparation

Treesearch

Carl C. Trettin; Martin F. Jurgensen; Margaret R. Gale; James W. McLaughlin

2011-01-01

We measured the change in above- and below-ground carbon and nutrient pools 11 years after the harvesting and site preparation of a histic-mineral soil wetland forest in the Upper Peninsula of Michigan. The original stand of black spruce (Picea mariana), jack pine (Pinus banksiana) and tamarack (Larix laricina) was whole-tree harvested, and three post-harvest...

Layer of organic pine forest soil on top of chlorophenol-contaminated mineral soil enhances contaminant degradation.

PubMed

Sinkkonen, Aki; Kauppi, Sari; Simpanen, Suvi; Rantalainen, Anna-Lea; Strömmer, Rauni; Romantschuk, Martin

2013-03-01

Chlorophenols, like many other synthetic compounds, are persistent problem in industrial areas. These compounds are easily degraded in certain natural environments where the top soil is organic. Some studies suggest that mineral soil contaminated with organic compounds is rapidly remediated if it is mixed with organic soil. We hypothesized that organic soil with a high degradation capacity even on top of the contaminated mineral soil enhances degradation of recalcitrant chlorophenols in the mineral soil below. We first compared chlorophenol degradation in different soils by spiking pristine and pentachlorophenol-contaminated soils with 2,4,6-trichlorophenol in 10-L buckets. In other experiments, we covered contaminated mineral soil with organic pine forest soil. We also monitored in situ degradation on an old sawmill site where mineral soil was either left intact or covered with organic pine forest soil. 2,4,6-Trichlorophenol was rapidly degraded in organic pine forest soil, but the degradation was slower in other soils. If a thin layer of the pine forest humus was added on top of mineral sawmill soil, the original chlorophenol concentrations (high, ca. 70 μg g(-1), or moderate, ca. 20 μg g(-1)) in sawmill soil decreased by >40 % in 24 days. No degradation was noticed if the mineral soil was kept bare or if the covering humus soil layer was sterilized beforehand. Our results suggest that covering mineral soil with an organic soil layer is an efficient way to remediate recalcitrant chlorophenol contamination in mineral soils. The results of the field experiment are promising.

The Trench Throws a Dirt Clod at Scientists

NASA Technical Reports Server (NTRS)

2004-01-01

This picture, obtained by the microscopic imager on NASA's Opportunity rover during sol 24, February 17 PST, shows soil clods exposed in the upper wall of the trench dug by Opportunity's right front wheel on sol 23. The clods were not exposed until the trench was made. The presence of soil clods implies weak bonding between individual soil grains. The chemical agent or mineral that causes the dirt to bind together into a clod, which scientists call the 'bonding agent,' is currently unknown. Moessbauer and alpha particle X-ray spectrometer measurements of this spot, planned for sol 25, might help explain the bonding, which would ultimately help the rover team understand how geological processes vary across the red planet. In any case, the bonds between soil grains here cannot be very strong because the wheel dug down through this layer with little trouble.

Mineralogical Composition of Particle-Size Fractions of Solonetzes from the North Crimean Lowland

NASA Astrophysics Data System (ADS)

Chizhikova, N. P.; Khitrov, N. B.; Tronza, G. E.; Kol'tsov, S. A.; Varlamov, E. B.; Chechetko, E. S.; Churilin, N. A.

2017-12-01

Data on the mineralogical composition of clay (<1 μm), fine silt (1-5 μm), medium silt (5-10 μm), and coarser (>10 μm) fractions of meadow solonchakous solonetzes (Calcic Gypsic Salic Stagnic Solonetz (Albic, Siltic, Columnic, Cutanic, Differentic)) developing from loesslike loam and clay in the North Crimean Lowland are presented. Fractions >5 μm constitute nearly 50% of the soil mass and are characterized by the same mineralogical composition in the entire profile; they consist of quartz, plagioclases, potassium feldspars, and micas (biotite and muscovite). The eluvial-illuvial redistribution of clay in the course of solonetzic process is accompanied by changes in the portion of mixed-layer minerals and hydromicas in the upper part of the profile; a larger part of the smectitic phase is transformed into the superdisperse state. In the eluvial SEL horizon and in the illuvial BSN horizon, the clay fraction is impoverished in smectitic phase and enriched in trioctahedral hydromicas. Upon calculation of the content of clay minerals per bulk soil mass, the distribution of mixed-layer minerals is either eluvial, or eluvial-illuvial, whereas the distribution of hydromicas has an illuvial pattern without distinct eluvial minimum in the SEL horizons. The eluvial-illuvial distribution pattern of clay minerals in solonetzes of the North Crimean Lowland is compared with the distribution pattern of clay minerals in solonetzes of the West Siberian Lowland. Coefficients characterizing differentiation of solonetzes by the contents of particular mineral components are suggested.

Salt and N leaching and soil accumulation due to cover cropping practices

NASA Astrophysics Data System (ADS)

Gabriel, J. L.; Quemada, M.

2012-04-01

Nitrate leaching beyond the root zone can increase water contamination hazards and decrease crop available N. Cover crops used in spite of fallow are an alternative to reduce nitrate contamination in the vadose zone, because reducing drainage and soil mineral N accumulation. Cover crops can improve important characteristics in irrigated land as water retention capacity or soil aggregate stability. However, increasing evapotranspiration and consequent drainage below the root system reduction, could lead to soil salt accumulation. Salinity affects more than 80 million ha of arable land in many areas of the world, and one of the principal causes for yield reduction and even land degradation in the Mediterranean region. Few studies dealt with both problems at the same time. Therefore, it is necessary a long-term evaluation of the potential effect on soil salinity and nitrate leaching, in order to ensure that potential disadvantages that could originate from soil salt accumulation are compensated with all advantages of cover cropping. A study of the soil salinity and nitrate leaching was conducted during 4 years in a semiarid irrigated agricultural area of Central Spain. Three treatments were studied during the intercropping period of maize (Zea mays L.): barley (Hordeum vulgare L.), vetch (Vicia villosa L.) and fallow. Cover crops were killed in March allowing seeding of maize of the entire trial in April, and all treatments were irrigated and fertilised following the same procedure. Before sowing, and after harvesting maize and cover crops, soil salt and nitrate accumulation was determined along the soil profile. Soil analysis was conducted at six depths every 0.20 m in each plot in samples from four 0 to 1.2-m depth holes dug. The electrical conductivity of the saturated paste extract and soil mineral nitrogen was measured in each soil sample. A numerical model based on the Richards water balance equation was applied in order to calculate drainage at 1.2 m depth, using daily soil water content measurements, based on calibrated capacitance probes. Our results showed that drainage during the irrigated period was minimized, because irrigation water was adjusted to crop needs, leading to soil salt and nitrate accumulation on the upper layers after maize harvest. Then, during the intercrop period, most of salt and nitrate leaching occurred. Cover crops use led to shorter drainage period, lower drainage water amount and lower nitrate and salt leaching than treatment with fallow. These effects were related with a larger nitrate accumulation in the upper layers of the soil after cover crop treatments. But there was not soil salt accumulation increase in treatments with cover crops, and even decreased after years with a large cover crop biomass production. Then, adoption of cover crops in this kind of irrigated cropping system reduced water drainage beyond the root zone, salt and nitrate leaching diminished as a consequence but did not lead to salt accumulation in the upper soil layers. Acknowledgements: Financial support by CICYT, Spain (ref. AGL2005-00163 and AGL 2011-24732) and Comunidad de Madrid (project AGRISOST, S2009/AGR-1630).

Mercury distribution in two Sierran forest and one desert sagebrush steppe ecosystems and the effects of fire.

PubMed

Engle, Mark A; Sexauer Gustin, Mae; Johnson, Dale W; Murphy, James F; Miller, Wally W; Walker, Roger F; Wright, Joan; Markee, Melissa

2006-08-15

Mercury (Hg) concentration, reservoir mass, and Hg reservoir size were determined for vegetation components, litter, and mineral soil for two Sierran forest sites and one desert sagebrush steppe site. Mercury was found to be held primarily in the mineral soil (maximum depth of 60 to 100 cm), which contained more than 90% of the total ecosystem reservoir. However, Hg in foliage, bark, and litter plays a more dominant role in Hg cycling than the mineral soil. Mercury partitioning into ecosystem components at the Sierran forest sites was similar to that observed for other US forest sites. Vegetation and litter Hg reservoirs were significantly smaller in the sagebrush steppe system because of lower biomass. Data collected from these ecosystems after wildfire and prescribed burns showed a significant decrease in the Hg pool from certain reservoirs. No loss from mineral soil was observed for the study areas but data from fire severity points suggested that Hg in the upper few millimeters of surface soil may be volatilized due to exposure to elevated temperatures. Comparison of data from burned and unburned plots suggested that the only significant source of atmospheric Hg from the prescribed burn was combustion of litter. Differences in unburned versus burned Hg reservoirs at the forest wildfire site demonstrated that drastic reduction in the litter and above ground live biomass Hg reservoirs after burning had occurred. Sagebrush and litter were absent in the burned plots after a wildfire suggesting that both reservoirs were released during the fire. Mercury emissions due to fire from the forest prescribed burn, forest wildfire, and sagebrush steppe wildfire sites were roughly estimated at 2.0 to 5.1, 2.2 to 4.9, and 0.36+/-0.13 g ha(-1), respectively, with litter and vegetation being the most important sources.

[Near infrared spectrum analysis and meaning of the soil in 512 earthquake surface rupture zone in Pingtong, Sichuan].

PubMed

Yi, Ze-bang; Cao, Jian-jin; Luo, Song-ying; Wang, Zheng-yang; Liao, Yi-peng

2014-08-01

Through modern near infrared spectrum, the authors analyzed the yellow soil from the rupture zone located in Ping- tong town,Pingwu, Sichuan province. By rapid identification of the characteristic of peak absorption of mineral particles, the result shows that the soil samples mainly composed of calcite, dolomite, muscovite, sericite, illite, smectite; talc, tremolite, actinolite, chlorite, etc. And the mineral compositions of the soil is basically the same with the yellow soil in Sichuan region. By analyzing and comparing it was revealed that part of mineral compositions of the soil are in accordance with the characteristics of the rock mineral compositions below the rupture zone, indicating that part of the minerals of the soil's evolution is closely related to the rock compositions in this area; and the compositions of the clay mineral in the rupture zone is similar to the Ma Lan loess in the north of China, so it is presumed that the clay minerals in these two kinds of soil have the same genetic type. The characteristic of the mineral composition of the soil is in accordance with evolution characteristics of the rocks which is bellow the rupture zone, also it was demonstrated that the results of soil minerals near-infrared analysis can effectively analyze the mineral particles in the soil and indicate the pedogenic environment. Therefore, the result shows the feasibility of adopting modern near-infrared spectrum for rapid analysis of mineral particles of the soil and research of geology. Meanwhile, the results can be the foundation of this region's soil mineral analysis, and also provide new ideas and methods for the future research of soil minerals and the earthquake rupture zone.

Biologically enhanced mineral weathering: what does it look like, can we model it?

NASA Astrophysics Data System (ADS)

Schulz, M. S.; Lawrence, C. R.; Harden, J. W.; White, A. F.

2011-12-01

The interaction between plants and minerals in soils is hugely important and poorly understood as it relates to the fate of soil carbon. Plant roots, fungi and bacteria inhabit the mineral soil and work symbiotically to extract nutrients, generally through low molecular weight exudates (organic acids, extracelluar polysachrides (EPS), siderophores, etc.). Up to 60% of photosynthetic carbon is allocated below ground as roots and exudates, both being important carbon sources in soils. Some exudates accelerate mineral weathering. To test whether plant exudates are incorporated into poorly crystalline secondary mineral phases during precipitation, we are investigating the biologic-mineral interface. We sampled 5 marine terraces along a soil chronosequence (60 to 225 ka), near Santa Cruz, CA. The effects of the biologic interactions with mineral surfaces were characterized through the use of Scanning Electron Microscopy (SEM). Morphologically, mycorrhizal fungi were observed fully surrounding minerals, fungal hyphae were shown to tunnel into primary silicate minerals and we have observed direct hyphal attachment to mineral surfaces. Fungal tunneling was seen in all 5 soils by SEM. Additionally, specific surface area (using a nitrogen BET method) of primary minerals was measured to determine if the effects of mineral tunneling are quantifiable in older soils. Results suggest that fungal tunneling is more extensive in the primary minerals of older soils. We have also examined the influence of organic acids on primary mineral weathering during soil development using a geochemical reactive transport model (CrunchFlow). Addition of organic acids in our models of soil development at Santa Cruz result in decreased activity of Fe and Al in soil pore water, which subsequently alters the spatial extent of primary mineral weathering and kaolinite precipitation. Overall, our preliminary modeling results suggest biological processes may be an important but underrepresented aspect of soil development in geochemical models.

Eucalyptus obliqua seedling growth in organic vs. mineral soil horizons

PubMed Central

Barry, Karen M.; Janos, David P.; Nichols, Scott; Bowman, David M. J. S.

2015-01-01

Eucalyptus obliqua, the most widespread timber tree in Tasmania, is a pioneer after fire which can eliminate the organic layer of forest soil, exposing the underlying mineral soil. We compared seedling growth, mycorrhiza formation, and mineral nutrient limitation in organic layer vs. mineral soil. We grew E. obliqua seedlings separately in pots of organic layer and mineral soil in a glasshouse. Additional treatments of organic soil only, involved fully crossed methyl-bromide fumigation and fertilization. Fertilization comprised chelated iron for 121 days after transplant (DAT) followed by soluble phosphorus. At 357 DAT, whole plant dry weight was three times greater in ambient organic than in mineral soil. In organic soil, fumigation halved ectomycorrhiza abundance and reduced seedling growth at 149 DAT, but by 357 DAT when negative effects of fumigation on seedling growth had disappeared, neither fumigation nor fertilization affected mycorrhiza abundance. Iron fertilization diminished seedling growth, but subsequent phosphorus fertilization improved it. E. obliqua seedlings grow much better in organic layer soil than in mineral soil, although phosphorus remains limiting. The prevalent forestry practice of burning to mineral soil after timber harvest exposes a poor growth medium likely only partially compensated by fire-induced mineral soil alterations. PMID:25750650

Quantifying bioturbation and soil thickening over the late Quaternary

NASA Astrophysics Data System (ADS)

Wilkinson, M. T.; Pietsch, T.; Fox, J. F.

2009-04-01

We present geochemistry and biochemistry data to explore how bioturbation has operated in a residual sandstone-derived soil that thickened during the Holocene following aeolian deflation during the Last Glacial Maximum. Our site is located on a plateau cut into Triassic sandstones in humid Blue Mountains, SE Australia, where precipitation is ~1100 mm/a, and the mean annual maximum and minimum temperatures are 17°C and 5°C, respectively. Vegetation cover increase occurred ~13 ka, based on nearby palaeodune activity and pollen data from other highland sites. Our interpretation of terrestrial cosmogenic radionuclides (TCN) data suggests that ~30 cm of soil thickening has taken place since 13 ka, which includes 16 cm of bedrock lowering. Biofabrics preserve a short-term picture of biotically-displaced soil. In general, bioturbation decreases exponentially with increasing soil depth. The upper 21 cm of the profile is ~95% bioturbated; the middle 13 cm is 13 - 32% bioturbated; and the lowest 52 cm is 1 - 6% bioturbated. Tree roots penetrate weakness in the sandstone below this depth. Fallout radionuclides (7Be, 210Pb, and 137Cs) in the profile also suggest that vertical mixing in the upper 20 - 40 cm occurs over short—decadal—timescales. Optically stimulated luminescene (OSL) data records the time that quartz grains were last at the surface, and are used here to demonstrate vertical mixing of the profile over tens of thousands of years. OSL data indicates that some soil grains at all burial depths were once at the surface, consistent with modern process observations. Carbon and nitrogen isotopic values (delta 13C and delta 15N) of soil organic matter support the existence of soil organic matter turnover in the upper 30 cm of the soil column when regressed with log(SOC) and log(TN). Our carbon isotope data defy typical trends below ~30 cm for residual, undisturbed soils. We suggest this may reflect the absence of bioturbation during the LGM when the climate was cold and dry, and soil was deflated. Since ~13 ka, we believe the vegetation cover increased and bioturbation became affective, resulting in mixing of organic and mineral material, and concurrent soil thickening.

The Impact of Organo-Mineral Complexation on Mineral Weathering in the Soil Zone under Unsaturated Conditions

NASA Astrophysics Data System (ADS)

Michael, H. A.; Tan, F.; Yoo, K.; Imhoff, P. T.

2017-12-01

While organo-mineral complexes can protect organic matter (OM) from biodegradation, their impact on soil mineral weathering is not clear. Previous bench-scale experiments that focused on specific OM and minerals showed that the adsorption of OM to mineral surfaces accelerates the dissolution of some minerals. However, the impact of natural organo-mineral complexes on mineral dissolution under unsaturated conditions is not well known. In this study, soil samples prepared from an undisturbed forest site were used to determine mineral weathering rates under differing conditions of OM sorption to minerals. Two types of soil samples were generated: 1) soil with OM (C horizon soil from 84-100cm depth), and 2) soil without OM (the same soil as in 1) but with OM removed by heating to 350°for 24 h). Soil samples were column-packed and subjected to intermittent infiltration and drainage to mimic natural rainfall events. Each soil sample type was run in duplicate. The unsaturated condition was created by applying gas pressure to the column, and the unsaturated chemical weathering rates during each cycle were calculated from the effluent concentrations. During a single cycle, when applying the same gas pressure, soils with OM retained more moisture than OM-removed media, indicating increased water retention capacity under the impact of OM. This is consistent with the water retention data measured by evaporation experiments (HYPROP) and the dew point method (WP4C Potential Meter). Correspondingly, silicon (Si) denudation rates indicated that dissolution of silicate minerals was 2-4 times higher in OM soils, suggesting that organo-mineral complexes accelerate mineral dissolution under unsaturated conditions. When combining data from all cycles, the results showed that Si denudation rates were positively related to soil water content: denundation rate increased with increasing water content. Therefore, natural mineral chemical weathering under unsaturated conditions, while widely considered to be facilitated by biological and chemical activities, may also be affected by soil retention properties.

Who's on First? Part II: Bacterial and fungal colonization of fresh soil minerals

NASA Astrophysics Data System (ADS)

Whitman, T.; Neurath, R.; Zhang, P.; Yuan, T.; Weber, P. K.; Zhou, J.; Pett-Ridge, J.; Firestone, M. K.

2015-12-01

Soil organic matter (SOM) stabilization by soil minerals is an important mechanism influencing soil C cycling. Microbes make up only a few percent of total SOM, but have a disproportionate impact on SOM cycling. Their direct interactions with soil minerals, however, are not well characterized. We studied colonization of fresh minerals by soil microbes in an Avena barbata (wild oat) California grassland soil microcosm. Examining quartz, ferrihydrite, kaolinite, and the heavy fraction of the native soil, we asked: (1) Do different minerals select for different communities, or do random processes drive the colonization of fresh minerals? (2) What factors influence which taxa colonize fresh minerals? After incubating mesh bags (<18 μm) of minerals buried next to actively growing plant roots for 2 months, we used high-throughput sequencing of 16S and ITS2 genes to characterize the microbial communities colonizing the minerals. We found significant differences between the microbial community composition of different minerals and soil for both bacteria and fungi. We found a higher relative abundance of arbuscular mycorrhial fungi with ferrihydrite and quartz, and nanoscale secondary ion mass spectrometry (NanoSIMS) imaging of these minerals suggests that some fungal hyphae are moving C directly from roots to mineral surfaces. The enriched presence of both nematode-associated fungi (Pochonia sp.) and bacteria (Candidatus Xiphinematobacter) in the minerals suggests that these minerals may be a habitat for nematodes. Bacteria of the family Chitinophagaceae and genus Janthinobacterium were significantly enriched on both ferrihydrite and quartz minerals, both of which may interact with colonizing fungi. These findings suggest that: (1) Microbial colonization of fresh minerals is not a fully passive or neutral process. (2) Mineral exploration by plant-associated fungi and soil fauna transport may be factors in determining the initial colonization of minerals and subsequent C protection.

Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

NASA Astrophysics Data System (ADS)

Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

2017-04-01

Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil dust will be compared to existing AIDA experiments at higher temperatures published by Steinke et al. (2016). Finally, the ice nucleation activity of both desert dust and agricultural soil dust will be compared for the upper tropospheric temperature regime. Andreae et al. (2009), Sources and Nature of Atmospheric Aerosols, in Aerosol Pollution Impact on Precipitation - A Scientific Review, Ch.3, Springer Netherlands, 45-89 Cziczo et al. (2013), Clarifying the Dominant Sources and Mechanisms of Cirrus Cloud Formation, Science, 340, 1320-1324 O'Sullivan et al. (2014), Ice nucleation by fertile soil dusts: relative importance of mineral and biogenic components, Atmos. Chem. Phys., 14, 1853-1867 Steinke et al. (2016), Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina and Germany, J. Geophys. Res., 121 Tobo et al. (2014), Organic matter matters for ice nuclei of agricultural soil origin, Atmos. Chem. Phys., 14, 8521-8531 Ullrich et al. (2017), A new ice nucleation active site parametrization for desert dust and soot, J. Atmos. Sci., in press

Effect of soil metal contamination on glyphosate mineralization: role of zinc in the mineralization rates of two copper-spiked mineral soils.

PubMed

Kim, Bojeong; Kim, Young Sik; Kim, Bo Min; Hay, Anthony G; McBride, Murray B

2011-03-01

A systematic investigation into lowered degradation rates of glyphosate in metal-contaminated soils was performed by measuring mineralization of [(14)C]glyphosate to (14)CO(2) in two mineral soils that had been spiked with Cu and/or Zn at various loadings. Cumulative (14)CO(2) release was estimated to be approximately 6% or less of the amount of [(14)C]glyphosate originally added in both soils over an 80-d incubation. For all but the highest Cu treatments (400 mg kg(-1)) in the coarse-textured Arkport soil, mineralization began without a lag phase and declined over time. No inhibition of mineralization was observed for Zn up to 400 mg kg(-1) in either soil, suggesting differential sensitivity of glyphosate mineralization to the types of metal and soil. Interestingly, Zn appeared to alleviate high-Cu inhibition of mineralization in the Arkport soil. The protective role of Zn against Cu toxicity was also observed in the pure culture study with Pseudomonas aeruginosa, suggesting that increased mineralization rates in high Cu soil with Zn additions might have been due to alleviation of cellular toxicity by Zn rather than a mineralization specific mechanism. Extensive use of glyphosate combined with its reduced degradation in Cu-contaminated, coarse-textured soils may increase glyphosate persistence in soil and consequently facilitate Cu and glyphosate mobilization in the soil environment. Copyright © 2010 SETAC.

Rapid Turnover and Minimal Accretion of Mineral Soil Carbon During 60-Years of Pine Forest Growth on Previously Cultivated Land

NASA Astrophysics Data System (ADS)

Richter, D., Jr.; Mobley, M. L.; Billings, S. A.; Markewitz, D.

2016-12-01

At the Calhoun Long-Term Soil-Ecosystem field experiment (1957-present), reforestation of previously cultivated land over fifty years nearly doubled soil organic carbon (SOC) in surface soils (0 to 7.5-cm) but these gains were offset by significant SOC losses in subsoils (35 to 60-cm). Nearly all of the accretions in surface soils amounted to gains in light fraction SOC, whereas losses at depth were associated with silt and clay-sized particles. These changes are documented in the Calhoun Long-Term Soil-Ecosystem (LTSE) study that resampled soil from 16 plots about every five years and archived all soil samples from four soil layers within the upper 60-cm of mineral soil. We combined soil bulk density, density fractionation, stable isotopes, and radioisotopes to explore changes in SOC and soil organic nitrogen (SON) associated with five decades of the growth of a loblolly pine secondary forest. Isotopic signatures showed relatively large accumulations of contemporary forest-derived carbon in surface soils, and no accumulation of forest-derived carbon in subsoils. We interpret results to indicate that land-use change from cotton fields to secondary pine forests drove soil biogeochemical and hydrological changes that enhanced root and microbial activity and SOM decomposition in subsoils. As pine stands matured and are now transitioning to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth has eased due to pine mortality, and bulk SOM and SON and their isotopes in subsoils have stabilized. We anticipate major changes in the next fifty years as 1957 pine trees transition to hardwoods. This study emphasizes the importance of long-term experiments and deep soil measurements when characterizing SOC and SON responses to land use change. There is a remarkable paucity of E long-term soil data deeper than 30 cm.

The Evolution of Porosity During Weathering of Serpentinite and the Creation of Thin Regolith in the Appalachian Piedmont

NASA Astrophysics Data System (ADS)

Marcon, V.; Gu, X.; Brantley, S. L.

2017-12-01

Life on Earth relies on the breakdown of impermeable bedrock into porous weathered rock to release nutrients and open pathways for gases and fluids to move through the subsurface. Serpentinites, though rare, are found across the globe and often have thin soils. Few studies have evaluated how porosity, a first order control on weathering, evolves from unweathered serpentinite bedrock to the soil. In this study, we evaluated weathering of serpentinites from bedrock to soil along a ridgetop in Nottingham Park, PA. A suite of geochemical analyses were used to determine chemical and physical changes during weathering. We used neutron scattering to measure pores 2nm to 20 microns in size (referred to here as nanoporosity). As this serpentinite weathers, small pores ( 1nm in diameter) are occluded and total nanoporosity and pore connectivity decrease throughout the weathered rock. Specifically, total nanoporosity decreases from 10% in the unweathered parent material to 5% in the weathered rock. However, in the upper meter of the profile, total nanoporosity increases as Fe, Mg, Mn, Si, Ni, Cr, and V are depleted. Additionally, bulk density and strain calculations suggest total volume expansion throughout the weathered rock followed by volume collapse in the upper 0.5m of the profile. We propose that low temperature reactions alter olivine in the parent material to serpentine minerals at the parent-weathered rock interface, resulting in a volume expansion and the loss of nanopores 1-100nm in size in this weathered rock zone. Volume expansion has long been reported to occur during low temperature serpentinization. We also infer that this loss of porosity limits the infiltration of reactive meteoric fluids into the deeper rock material and restricts the depth of regolith development. Following low temperature serpentinization, serpentine minerals (e.g. antigorite and lizardite) dissolve higher in the weathered rock. Because serpentinite rocks lack a non-reactive mineral such as quartz to provide supportive skeleton in the regolith, dissolution ultimately leads to collapse in the upper meter of the profile. The evolution of porosity in this profile can help explain why serpentinite regolith is characteristically thin to non-existent in the Piedmont: thin regolith occurs because of porosity occlusion as well as collapse.

[Research on characteristics of soil clay mineral evolution in paddy field and dry land by XRD spectrum].

PubMed

Zhang, Zhi-dan; Li, Qiao; Luo, Xiang-li; Jiang, Hai-chao; Zheng, Qing-fu; Zhao, Lan-po; Wang, Ji-hong

2014-08-01

The present paper took the typical saline-alkali soil in Jilin province as study object, and determinated the soil clay mineral composition characteristics of soil in paddy field and dry land. Then XRD spectrum was used to analyze the evolutionary mechanism of clay mineral in the two kinds of soil. The results showed that the physical and chemical properties of soil in paddy field were better than those in dry land, and paddy field would promote the weathering of mineral particles in saline-alkali soil and enhance the silt content. Paddy field soil showed a strong potassium-removal process, with a higher degree of clay mineral hydration and lower degree of illite crystallinity. Analysis of XRD spectrum showed that the clay mineral composition was similar in two kinds of soil, while the intensity and position of diffraction peak showed difference. The evolution process of clay mineral in dry land was S/I mixture-->vermiculite, while in paddy field it was S/I mixture-->vermiculite-->kaolinite. One kind of hydroxylated 'chlorite' mineral would appear in saline-alkali soil in long-term cultivated paddy field. Taking into account that the physical and chemical properties of soil in paddy field were better then those in dry land, we could know that paddy field could help much improve soil structure, cultivate high-fertility soil and improve saline-alkali soil. This paper used XRD spectrum to determine the characteristics of clay minerals comprehensively, and analyzed two'kinds of land use comparatively, and was a new perspective of soil minerals study.

Changes in soil CO2 efflux of organic calcaric soils due to disturbance by wind

NASA Astrophysics Data System (ADS)

Mayer, M.; Katzensteiner, K.

2012-04-01

Disturbances such as windthrow or insect infestations are supposed to have a significant influence on the soil carbon balance of affected forests. Increasing soil temperatures and changes in the soil moisture regime, caused by the removed tree layer, are expected to change soil CO2 efflux, also known as soil respiration. Beside an anticipated stimulation of the carbon mineralization, the main part of root allocated CO2 is offset due to the blown down trees. On mountain forest sites of the Northern Limestone Alps, where highly active organic soils above calcareous parent material are characteristic (Folic Histosols and Rendzic Leptosols), an increase of the mineralization rate of carbon may contribute to enormous humus losses. Serious site degradation can be the consequence, especially on south exposed slopes where extreme climatic conditions occur. The present study tries to give insights to disturbance induced changes in temporal and spatial behaviour of soil respiration for a montane mountain forest located in the Northern Limestone Alps of Upper Austria. Soil respiration, soil temperature and volumetric water content were measured on two windthrow areas (blow down dates were 2007 and 2009 respectively) as well as in an adjacent mature mixed forest during the vegetation periods of 2010 and 2011. Soil respiration in both years was mainly driven by soil temperature, which explained up to 90 % of the concerning temporal variation. Volumetric water content had a significant influence as additional temporal driver. After removing the temperature trend, significant differences in basal soil respiration rates were found for the disturbance area and the forest stand. Inter seasonal declines in soil respiration were ascertained for the mature stand as well as for the recent windthrow. Particular decreases are related to drought stress in summer 2011 and a proceeded decomposition of labile soil carbon components at the windthrow site. An interaction between soil type and stratum showed a distinctive decrease in the soil CO2 efflux pattern for organic soils by comparing the recent and old disturbance areas. Such a downward trend was also detected on the more recently disturbed area in the consecutive years. These findings support the assumption that carbon mineralization can account for excessive losses in soil organic carbon after forest disturbance, whereas organic humus soils are supposed to be particularly vulnerable. This study is part of the INTERREG Bayern-Österreich 2007 -2013 project 'SicAlp - Standortssicherung im Kalkalpin' which is funded by the European Regional Development Fund (ERDF) and national funding.

Relationship between the parent material and the soil, in plain and mountainous areas

NASA Astrophysics Data System (ADS)

Kerek, Barbara; Kuti, Laszlo; Dobos, Timea; Vatai, Jozsef; Szentpetery, Ildiko

2013-04-01

One of the most important tasks of the soil is the nutrition of plants. This function is determinated by those parts of the geological media on what is the soil situated and from what the soil was formed (those two can be different). Soil can be formed definitely just from sediment, so it is more proper to speak about parent material than parent rock. Soil forming sediment is defined as the loose sediment on the surface, which is the upper layer of near-surface rocks in flat and hilly regions, and it is the upper layer of the sediment-ensemble situated on the undisturbed bedrock in mountainous areas. Considering its origin, these sediments could be autochthon or allochton. Soil forming is determinated, besides other factors (climate, elevation, vegetation, etc.), by the parent material, which has a crucial influence on the type, quality and fertility of soils through its mineral composition, physical and chemical characteristics. Agrogeological processes happen in the superficial loose sediments in mountainous areas, but the underlying solid rock (where on the surface or close to it, there is solid rock), has an effect on them. The plain and hilly regions covered by thick loose sediment and the areas build up by solid rock and covered with thinner loose sediment in mountainous areas should be searched separately. In plain areas the near-surface formations have to be studied as a whole down to the saturated zone, but at least to 10 m. In regions of mountain and mountain fronts, the thickness, the composition and genetics of the young unconsolidated sediments situated above the older solid rocks have a vital importance, and also the relations among the soils, soil forming sediments and the base rocks have to be understood.

Imaging and Analytical Approaches for Characterization of Soil Mineral Weathering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dohnalkova, Alice; Arey, Bruce; Varga, Tamas

Soil minerals weathering is the primary natural source of nutrients necessary to sustain productivity in terrestrial ecosystems. Soil microbial communities increase soil mineral weathering and mineral-derived nutrient availability through physical and chemical processes. Rhizosphere, the zone immediately surrounding plant roots, is a biogeochemical hotspot with microbial activity, soil organic matter production, mineral weathering, and secondary phase formation all happening in a small temporally ephemeral zone of steep geochemical gradients. The detailed exploration of the micro-scale rhizosphere is essential to our better understanding of large-scale processes in soils, such as nutrient cycling, transport and fate of soil components, microbial-mineral interactions, soilmore » erosion, soil organic matter turnover and its molecular-level characterization, and predictive modeling.« less

Mineral Types and Tree Species Determine the Functional and Taxonomic Structures of Forest Soil Bacterial Communities.

PubMed

Colin, Y; Nicolitch, O; Turpault, M-P; Uroz, S

2017-03-01

Although minerals represent important soil constituents, their impact on the diversity and structure of soil microbial communities remains poorly documented. In this study, pure mineral particles with various chemistries (i.e., obsidian, apatite, and calcite) were considered. Each mineral type was conditioned in mesh bags and incubated in soil below different tree stands (beech, coppice with standards, and Corsican pine) for 2.5 years to determine the relative impacts of mineralogy and mineral weatherability on the taxonomic and functional diversities of mineral-associated bacterial communities. After this incubation period, the minerals and the surrounding bulk soil were collected to determine mass loss and to perform soil analyses, enzymatic assays, and cultivation-dependent and -independent analyses. Notably, our 16S rRNA gene pyrosequencing analyses revealed that after the 2.5-year incubation period, the mineral-associated bacterial communities strongly differed from those of the surrounding bulk soil for all tree stands considered. When focusing only on minerals, our analyses showed that the bacterial communities associated with calcite, the less recalcitrant mineral type, significantly differed from those that colonized obsidian and apatite minerals. The cultivation-dependent analysis revealed significantly higher abundances of effective mineral-weathering bacteria on the most recalcitrant minerals (i.e., apatite and obsidian). Together, our data showed an enrichment of Betaproteobacteria and effective mineral-weathering bacteria related to the Burkholderia and Collimonas genera on the minerals, suggesting a key role for these taxa in mineral weathering and nutrient cycling in nutrient-poor forest ecosystems. IMPORTANCE Forests are usually developed on nutrient-poor and rocky soils, while nutrient-rich soils have been dedicated to agriculture. In this context, nutrient recycling and nutrient access are key processes in such environments. Deciphering how soil mineralogy influences the diversity, structure, and function of soil bacterial communities in relation to the soil conditions is crucial to better understanding the relative role of the soil bacterial communities in nutrient cycling and plant nutrition in nutrient-poor environments. The present study determined in detail the diversity and structure of bacterial communities associated with different mineral types incubated for 2.5 years in the soil under different tree species using cultivation-dependent and -independent analyses. Our data showed an enrichment of specific bacterial taxa on the minerals, specifically on the most weathered minerals, suggesting that they play key roles in mineral weathering and nutrient cycling in nutrient-poor forest ecosystems. Copyright © 2017 American Society for Microbiology.

Mineral Types and Tree Species Determine the Functional and Taxonomic Structures of Forest Soil Bacterial Communities

PubMed Central

Colin, Y.; Nicolitch, O.; Turpault, M.-P.

2016-01-01

ABSTRACT Although minerals represent important soil constituents, their impact on the diversity and structure of soil microbial communities remains poorly documented. In this study, pure mineral particles with various chemistries (i.e., obsidian, apatite, and calcite) were considered. Each mineral type was conditioned in mesh bags and incubated in soil below different tree stands (beech, coppice with standards, and Corsican pine) for 2.5 years to determine the relative impacts of mineralogy and mineral weatherability on the taxonomic and functional diversities of mineral-associated bacterial communities. After this incubation period, the minerals and the surrounding bulk soil were collected to determine mass loss and to perform soil analyses, enzymatic assays, and cultivation-dependent and -independent analyses. Notably, our 16S rRNA gene pyrosequencing analyses revealed that after the 2.5-year incubation period, the mineral-associated bacterial communities strongly differed from those of the surrounding bulk soil for all tree stands considered. When focusing only on minerals, our analyses showed that the bacterial communities associated with calcite, the less recalcitrant mineral type, significantly differed from those that colonized obsidian and apatite minerals. The cultivation-dependent analysis revealed significantly higher abundances of effective mineral-weathering bacteria on the most recalcitrant minerals (i.e., apatite and obsidian). Together, our data showed an enrichment of Betaproteobacteria and effective mineral-weathering bacteria related to the Burkholderia and Collimonas genera on the minerals, suggesting a key role for these taxa in mineral weathering and nutrient cycling in nutrient-poor forest ecosystems. IMPORTANCE Forests are usually developed on nutrient-poor and rocky soils, while nutrient-rich soils have been dedicated to agriculture. In this context, nutrient recycling and nutrient access are key processes in such environments. Deciphering how soil mineralogy influences the diversity, structure, and function of soil bacterial communities in relation to the soil conditions is crucial to better understanding the relative role of the soil bacterial communities in nutrient cycling and plant nutrition in nutrient-poor environments. The present study determined in detail the diversity and structure of bacterial communities associated with different mineral types incubated for 2.5 years in the soil under different tree species using cultivation-dependent and -independent analyses. Our data showed an enrichment of specific bacterial taxa on the minerals, specifically on the most weathered minerals, suggesting that they play key roles in mineral weathering and nutrient cycling in nutrient-poor forest ecosystems. PMID:28003192

[Organic carbon and carbon mineralization characteristics in nature forestry soil].

PubMed

Yang, Tian; Dai, Wei; An, Xiao-Juan; Pang, Huan; Zou, Jian-Mei; Zhang, Rui

2014-03-01

Through field investigation and indoor analysis, the organic carbon content and organic carbon mineralization characteristics of six kinds of natural forest soil were studied, including the pine forests, evergreen broad-leaved forest, deciduous broad-leaved forest, mixed needle leaf and Korean pine and Chinese pine forest. The results showed that the organic carbon content in the forest soil showed trends of gradual decrease with the increase of soil depth; Double exponential equation fitted well with the organic carbon mineralization process in natural forest soil, accurately reflecting the mineralization reaction characteristics of the natural forest soil. Natural forest soil in each layer had the same mineralization reaction trend, but different intensity. Among them, the reaction intensity in the 0-10 cm soil of the Korean pine forest was the highest, and the intensities of mineralization reaction in its lower layers were also significantly higher than those in the same layers of other natural forest soil; comparison of soil mineralization characteristics of the deciduous broad-leaved forest and coniferous and broad-leaved mixed forest found that the differences of litter species had a relatively strong impact on the active organic carbon content in soil, leading to different characteristics of mineralization reaction.

Clay mineral type effect on bacterial enteropathogen survival in soil.

PubMed

Brennan, Fiona P; Moynihan, Emma; Griffiths, Bryan S; Hillier, Stephen; Owen, Jason; Pendlowski, Helen; Avery, Lisa M

2014-01-15

Enteropathogens released into the environment can represent a serious risk to public health. Soil clay content has long been known to have an important effect on enteropathogen survival in soil, generally enhancing survival. However, clay mineral composition in soils varies, and different clay minerals have specific physiochemical properties that would be expected to impact differentially on survival. This work investigated the effect of clay materials, with a predominance of a particular mineral type (montmorillonite, kaolinite, or illite), on the survival in soil microcosms over 96 days of Listeria monocytogenes, Salmonella Dublin, and Escherichia coli O157. Clay mineral addition was found to alter a number of physicochemical parameters in soil, including cation exchange capacity and surface area, and this was specific to the mineral type. Clay mineral addition enhanced enteropathogen survival in soil. The type of clay mineral was found to differentially affect enteropathogen survival and the effect was enteropathogen-specific. © 2013.

Microbial biomass and basal respiration in Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

NASA Astrophysics Data System (ADS)

Abakumov, E.; Mukhametova, N.

2014-03-01

Antarctica is the unique place for pedological investigations. Soils of Antarctica have been studied intensively during the last century. Antarctic logistic provides the possibility to scientists access the terrestrial landscapes mainly in the places of polar stations. That is why the main and most detailed pedological investigations were conducted in Mc Murdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann hills and Schirmacher Oasis. Investigations were conducted during the 53rd and 55th Russian Antarctic expeditions on the base of soil pits and samples collected in Sub-Antarctic and Antarctic regions. Soils of diverse Antarctic landscapes were studied with aim to assess the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. The investigation conducted shows that soils of Antarctic are quite different in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as the upper organic layer. The most developed organic layers were revealed in peat soils of King-George Island, where its thickness reach even 80 cm. These soils as well as soils under guano are characterized by the highest amount of total organic carbon (TOC) 7.22-33.70%. Coastal and continental soils of Antarctic are presented by less developed Leptosols, Gleysols, Regolith and rare Ornhitosol with TOC levels about 0.37-4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones which can be interpreted as result of higher amounts of fresh organic remnants in organic and organo-mineral horizons. Also the soils of King-George island have higher portion of microbial biomass (max 1.54 mg g-1) than coastal (max 0.26 mg g-1) and continental (max 0.22 mg g-1) Antarctic soils. Sub-Antarctic soils mainly differ from Antarctic ones in increased organic layers thickness and total organic carbon content, higher microbial biomass carbon content, basal respiration and metabolic activity levels.

Priming effects and enzymatic activity in Israeli soils under treated wastewater and freshwater irrigation

NASA Astrophysics Data System (ADS)

Anissimova, Marina; Heinze, Stefanie; Chen, Yona; Tarchitzky, Jorge; Marschner, Bernd

2014-05-01

Irrigation of soils with treated wastewater (TWW) directly influences microbial processes of soil. TWW contains easily decomposable organic material, which can stimulate the activity of soil microorganisms and, as a result, lead to the excessive consumption of soil organic carbon pool. We investigated the effects of irrigation with TWW relative to those of irrigation with freshwater (FW) on the microbial parameters in soils with low (7%) and medium (13%) clay content in a lysimeter experiment. The objectives of our study were to (i) determine the impact of water quality on soil respiration and enzymatic activity influenced by clay content and depth, and (ii) work out the changes in the turnover of soil organic matter (PE, priming effects). Samples were taken from three soil depths (0-10, 10-20, and 40-60 cm). Soil respiration and PE were determined in a 21-days incubation experiment after addition of uniformly 14C-labeled fructose. Activity of 10 extracellular enzymes (EEA, from C-, N-, P-, and S-cycle), phenol oxidase and peroxidase activity (PO+PE), and dehydrogenase activity (DHA) were assayed. Microbial Community-Level Physiological Profiles (CLPP) using four substrates, and microbial biomass were determined. The results showed that the clay content acted as the main determinative factor. In the soil with low clay content the water quality had a greater impact: the highest PE (56%) was observed in the upper layer (0-10cm) under FW irrigation; EEA of C-, P-, and S-cycles was significantly higher in the upper soil layer under TWW irrigation. Microbial biomass was higher in the soil under TWW irrigation and decreased with increasing of depth (50 μg/g soil in the upper layer, 15 μg/g soil in the lowest layer). This tendency was also observed for DHA. Contrary to the low clay content, in the soil with medium clay content both irrigation types caused the highest PE in the lowest layer (65% under FW irrigation, 48% under TWW irrigation); the higher substrate mineralization (10%) and the highest phosphatase activity (in the case of FW irrigation) was observed. The PO+PE activity was two to three times higher than in the soil with low clay content and increased clearly with increasing of soil depth. The last tendency was also valid generally for the enzymes of C-, N-, and P-cycles under both types of irrigation. The upper layer in the soil under TWW irrigation was characterized by the highest microbial biomass value (74 μg/g soil). DHA in all soil depths under both types of irrigation was significantly higher than in the corresponding depths of soil with low clay content. CLPP data showed the highest consumption of ascorbic acid and D-glucosamine hydrochloride in comparison to consumption of D-glucose and L-glutamine in both irrigation types.

Who's on first? Part I: Influence of plant growth on C association with fresh soil minerals

NASA Astrophysics Data System (ADS)

Neurath, R.; Whitman, T.; Nico, P. S.; Pett-Ridge, J.; Firestone, M. K.

2015-12-01

Mineral surfaces provide sites for carbon stabilization in soils, protecting soil organic matter (SOM) from microbial degradation. SOM distributed across mineral surfaces is expected to be patchy and certain minerals undergo re-mineralization under dynamic soil conditions, such that soil minerals surfaces can range from fresh to thickly-coated with SOM. Our research investigates the intersection of microbiology and geochemistry, and aims to build a mechanistic understanding of plant-derived carbon (C) association with mineral surfaces and the factors that determine SOM fate in soil. Plants are the primary source of C in soil, with roots exuding low-molecular weight compounds during growth and contributing more complex litter compounds at senescence. We grew the annual grass, Avena barbata, (wild oat) in a 99 atom% 13CO2 atmosphere in soil microcosms incubated with three mineral types representing a spectrum of reactivity and surface area: quartz, kaolinite, and ferrihydrite. These minerals, isolated in mesh bags to exclude roots but not microorganisms, were extracted and analyzed for total C and 13C at multiple plant growth stages. At plant senescence, the quartz had the least mineral-bound C (0.40 mg-g-1) and ferrihydrite the most (0.78 mg-g-1). Ferrihydrite and kaolinite also accumulated more plant-derived C (3.0 and 3.1% 13C, respectively). The experiment was repeated with partially digested 13C-labled root litter to simulate litter decomposition during plant senescence. Thus, we are able evaluate contributions derived from living and dead root materials on soil minerals using FTIR and 13C-NMR. We find that mineral-associated C bears a distinct microbial signature, with soil microbes not only transforming SOM prior to mineral association, but also populating mineral surfaces over time. Our research shows that both soil mineralogy and the chemical character of plant-derived compounds are important controls of mineral protection of SOM.

[Soil organic carbon mineralization of Black Locust forest in the deep soil layer of the hilly region of the Loess Plateau, China].

PubMed

Ma, Xin-Xin; Xu, Ming-Xiang; Yang, Kai

2012-11-01

The deep soil layer (below 100 cm) stores considerable soil organic carbon (SOC). We can reveal its stability and provide the basis for certification of the deep soil carbon sinks by studying the SOC mineralization in the deep soil layer. With the shallow soil layer (0-100 cm) as control, the SOC mineralization under the condition (temperature 15 degrees C, the soil water content 8%) of Black Locust forest in the deep soil layer (100-400 cm) of the hilly region of the Loess Plateau was studied. The results showed that: (1) There was a downward trend in the total SOC mineralization with the increase of soil depth. The total SOC mineralization in the sub-deep soil (100-200 cm) and deep soil (200-400 cm) were equivalent to approximately 88.1% and 67.8% of that in the shallow layer (0-100 cm). (2) Throughout the carbon mineralization process, the same as the shallow soil, the sub-deep and deep soil can be divided into 3 stages. In the rapid decomposition phase, the ratio of the mineralization or organic carbon to the total mineralization in the sub-deep and deep layer (0-10 d) was approximately 50% of that in the shallow layer (0-17 d). In the slow decomposition phase, the ratio of organic carbon mineralization to total mineralization in the sub-deep, deep layer (11-45 d) was 150% of that in the shallow layer (18-45 d). There was no significant difference in this ratio among these three layers (46-62 d) in the relatively stable stage. (3) There was no significant difference (P > 0.05) in the mineralization rate of SOC among the shallow, sub-deep, deep layers. The stability of SOC in the deep soil layer (100-400 cm) was similar to that in the shallow soil layer and the SOC in the deep soil layer was also involved in the global carbon cycle. The change of SOC in the deep soil layer should be taken into account when estimating the effects of soil carbon sequestration in the Hilly Region of the Loess Plateau, China.

Development of bulk density, total C distribution and OC saturation in fine mineral fractions during paddy soil evolution

NASA Astrophysics Data System (ADS)

Wissing, Livia; Kölbl, Angelika; Cao, Zhi-Hong; Kögel-Knabner, Ingrid

2010-05-01

Paddy soils are described as important accumulator for OM (Zhang and He, 2004). In southeast China, paddy soils have the second highest OM stocks (Zhao et al, 1997) and thus a large proportion of the terrestrial carbon is conserved in wetland rice soils. The paddy soil management is believed to be favorable for accumulation of organic matter, as its content in paddy soils is statistically higher than that of non-paddy soils (Cai, 1996). However, the mechanism of OM storage and the development of OM distribution during paddy soil evolution is largely unknown. The aim of the project is to identify the role of organo-mineral complexes for the stabilization of organic carbon during management-induced paddy soil formation in a chronosequence ranging from 50 to 2000 years of paddy soil use. The soil samples were analysed for bulk density, total organic carbon (TOC) and total inorganic carbon (TIC) concentrations of bulk soils and the concentration of organic carbon as well as the organic carbon stocks of physical soil fractions. First results indicate distinctly different depth distributions between paddy and non-paddy (control) sites. The paddy soils are characterized by relatively low bulk densities in the puddled layer (between 0.9 and 1.3 g cm-3) and high values in the plough pan (1.4 to 1.6 g cm-3) and the non-paddy soils by relatively homogeneous values throughout the profiles (1.3 to 1.4 g cm-3). In contrast to the carbonate-rich non-paddy sites, we found a significant loss of carbonates during paddy soil formation, resulting in decalcification of the upper 20 cm after 100 yr of paddy soil use, and decalcification of the total soil profile in 700, 1000 and 2000 yr old paddy soils. The calculation of the organic carbon stocks of each horizon indicate that paddy sites always have higher values in topsoils compared to non-paddy sites, and show increasing values with increasing soil age. The capacity of fine mineral fractions to preserve OC was calculated according to Hassink (1997). The potential capacity of paddy soil fraction to preserve OC is independently from soil age between 30 and 35.4 g OC (kg soil)-1. However, the calculated saturation level increases from 11.7 to 19.9 g OC (kg soil)-1 from 50 to 2000 y old paddy sites respectively. With increasing duration of paddy soil use, the fine fractions indicate an increasing saturation level from 33.1% to 56.2% of the potential capacity to preserve OC. This underlines the importance of fine fractions for increasing OC storage during paddy soil evolution. Conclusively, paddy soil management leads to an accelerated soil development compared to non-irrigated cropland sites. In addition, increasing OC stocks, especially in the fine mineral associated OM fractions underline the relevance of paddy soil management for OC sequestration. References Cai Z. (1996). Effect of land use on organic carbon storage in soils in eastern China. Water Air Soil Pollut 91, 383-393. Hassink J. (1997). The capacity of soil to preserve organic C and N by their association with clay and silt particles. Plant and Soil 191, 77-87. Zhang M., He Z. (2004). Long-term changes in organic carbon and nutrients of an Ultisol under rice cropping in southeast China. Geoderma 118, 167-179. Zhao C. (1996). Effect of land use on organic carbon storage in soils in eastern China. Water Air Soil Pollut 91, 383-393.

Hydrogeomorphology influences soil nitrogen and phosphorus mineralization in floodplain wetlands

USGS Publications Warehouse

Noe, Gregory B.; Hupp, Cliff R.; Rybicki, Nancy B.

2013-01-01

Conceptual models of river–floodplain systems and biogeochemical theory predict that floodplain soil nitrogen (N) and phosphorus (P) mineralization should increase with hydrologic connectivity to the river and thus increase with distance downstream (longitudinal dimension) and in lower geomorphic units within the floodplain (lateral dimension). We measured rates of in situ soil net ammonification, nitrification, N, and P mineralization using monthly incubations of modified resin cores for a year in the forested floodplain wetlands of Difficult Run, a fifth order urban Piedmont river in Virginia, USA. Mineralization rates were then related to potentially controlling ecosystem attributes associated with hydrologic connectivity, soil characteristics, and vegetative inputs. Ammonification and P mineralization were greatest in the wet backswamps, nitrification was greatest in the dry levees, and net N mineralization was greatest in the intermediately wet toe-slopes. Nitrification also was greater in the headwater sites than downstream sites, whereas ammonification was greater in downstream sites. Annual net N mineralization increased with spatial gradients of greater ammonium loading to the soil surface associated with flooding, soil organic and nutrient content, and herbaceous nutrient inputs. Annual net P mineralization was associated negatively with soil pH and coarser soil texture, and positively with ammonium and phosphate loading to the soil surface associated with flooding. Within an intensively sampled low elevation flowpath at one site, sediment deposition during individual incubations stimulated mineralization of N and P. However, the amount of N and P mineralized in soil was substantially less than the amount deposited with sedimentation. In summary, greater inputs of nutrients and water and storage of soil nutrients along gradients of river–floodplain hydrologic connectivity increased floodplain soil nutrient mineralization rates.

[Nitrogen mineralization rate in different soil layers and its influence factors under plastic film mulched in Danjiangkou Reservoir area, China].

PubMed

Yu, Xing Xiu; Xui, Miao Miao; Zhao, Jin Hui; Zhang, Jia Peng; Wang, Wei; Guo, Ya Li; Xiao, Juan Hua

2018-04-01

The objective of this study was to investigate the rate of nitrogen mineralization in various soil layers (0-10, 10-20, and 20-30 cm) and its influencing factors under plastic film mulching ridge-furrow in a corn field of Wulongchi small watershed, Danjiangkou Reservoir Area. Results showed that the rate of soil ammonification decreased with soil depth during the entire maize growth period. The rate of nitrification in seedling, jointing, and heading stages decreased in the following order: 10-20 cm > 0-10 cm > 20-30 cm, while it increased with soil depth in maturation stage. The rate of soil nitrogen mineralization decreased with the increases in soil depth in the seedling, jointing and heading stages, whereas an opposite pattern was observed in maturation stage. Compared with non-filming, film mulching promoted the soil ammonification process in 0-10 cm and the soil nitrification and nitrogen mineralization processes in jointing, heading, and maturation stages in both 0-10 and 10-20 cm. However, the rates of soil nitrification and nitrogen mineralization under film mulching were much lower than those under non-filming in seedling stage. The stepwise regression analysis indicated that the main factors influencing soil nitrogen mineralization rate varied with soil depth. Soil moisture and total N content were the dominant controller for variation of soil nitrogen mineralization in 0-10 cm layer. Soil temperature, moisture, and total N content were dominant controller for that in 10-20 cm layer. Soil temperature drove the variation of soil nitrogen mineralization in 20-30 cm layer.

Redistribution of soil nitrogen, carbon and organic matter by mechanical disturbance during whole-tree harvesting in northern hardwoods

USGS Publications Warehouse

Ryan, D.F.; Huntington, T.G.; Wayne, Martin C.

1992-01-01

To investigate whether mechanical mixing during harvesting could account for losses observed from forest floor, we measured surface disturbance on a 22 ha watershed that was whole-tree harvested. Surface soil on each 10 cm interval along 81, randomly placed transects was classified immediately after harvesting as mineral or organic, and as undisturbed, depressed, rutted, mounded, scarified, or scalped (forest floor scraped away). We quantitatively sampled these surface categories to collect soil in which preharvest forest floor might reside after harvest. Mechanically mixed mineral and organic soil horizons were readily identified. Buried forest floor under mixed mineral soil occurred in 57% of mounds with mineral surface soil. Harvesting disturbed 65% of the watershed surface and removed forest floor from 25% of the area. Mechanically mixed soil under ruts with organic or mineral surface soil, and mounds with mineral surface soil contained organic carbon and nitrogen pools significantly greater than undisturbed forest floor. Mechanical mixing into underlying mineral soil could account for the loss of forest floor observed between the preharvest condition and the second growing season after whole-tree harvesting. ?? 1992.

Evaluating Mineral-Associated Soil Organic Matter Pools as Indicators of Forest Harvesting Disturbance

NASA Astrophysics Data System (ADS)

Kellman, L. M.; Gabriel, C. E.

2015-12-01

Soil organic matter (SOM) in northern forest soils is associated with a suite of minerals that can confer SOM stability, resulting in the potential for long-term storage of carbon. Increasingly, evidence is suggesting that SOM in certain mineral phases is dynamic and vulnerable to soil disturbance. The objective of this research was to investigate changes in a suite of mineral-associated pools of SOM through depth in a temperate forest soil to determine which mineral-associated carbon pools are most sensitive to forest harvesting disturbance. Sequential selective dissolutions representing increasingly stable SOM pools (soluble minerals (deionized water); humus-mineral complexes (Na-pyrophosphate); poorly crystalline minerals (HCl hydroxylamine); and crystalline secondary minerals (Na-dithionite + HCl)) of mineral soils through depth to 50 cm were carried out in podzolic soils sampled from temperate red spruce forests of contrasting stand age in Nova Scotia, Canada. Results of this analysis point to a loss of carbon from SOM within the B-horizon of the most recently harvested site from the pyrophosphate-extracted humus mineral complexed SOM, suggesting that it is this exchangeable pool that appears to be destabilized following clearcut harvesting at these study sites. This suggests that recovery from this landuse disturbance is dependent upon increasing storage of this SOM pool, and that mineral-associated pools, particularly pyrophosphate-extractable SOM, may be a useful indicator of changes to soil carbon storage following land use change.

Effects of plant cover on soil N mineralization during the growing season in a sandy soil

NASA Astrophysics Data System (ADS)

Yao, Y.; Shao, M.; Wei, X.; Fu, X.

2017-12-01

Soil nitrogen (N) mineralization and its availability plays a vital role in regulating ecosystem productivity and C cycling, particularly in semiarid and desertified ecosystems. To determine the effect of plant cover on N turnover in a sandy soil ecosystem, we measured soil N mineralization and inorganic N pools in soil solution during growing season in a sandy soil covered with various plant species (Artemisia desertorum, Salix psammophila, and Caragana korshinskii). A bare sandy soil without any plant was selected as control. Inorganic N pools and N mineralization rates decreased overtime during the growing season, and were not affected by soil depth in bare land soils, but were significantly higher at the 0-10 cm layer than those at the 10-20 cm soil layer under any plant species. Soil inorganic N pool was dominated by ammonium, and N mineralization was dominated by nitrification regardless of soil depth and plant cover. Soils under C. korshinskii have significant higher inorganic N pools and N mineralization rate than soils under bare land and A. desertorum and S. psammophila, and the effects of plant cover were greater at the 0-10 cm soil layer than at the 10-20 cm layer. The effects of C. korshinskii on soil inorganic N pools and mineralization rate varied with the stage of growing season, with greater effects on N pools in the middle growing season, and greater effects on mineralization rate at the last half of the growing season. The results from this study indicate that introduction of C. korshinskii has the potential to increase soil N turnover and availability in sandy soils, and thus to decrease N limitation. Caragana korshinskii is therefore recommend for the remediation of the desertified land.

The Place of Rock and Mineral Identification in Geoscience Programs

NASA Astrophysics Data System (ADS)

Nicholls, J.

2011-12-01

Geoscience programs traditionally required a significant amount of class and laboratory time for students to learn to identify Earth materials: minerals, rocks, soils, and fossils. Two decades ago, courses devoted to the mineral sciences, mineralogy and petrology, constituted approximately 20% of a geoscience program. Today, they make up between 5% and 10% of the courses in such a program. Two decades ago students spent their laboratory time learning to identify Earth materials. Today, they do the same thing, even though the time set aside for students to achieve proficiency is limited. A typical learning objective for a geoscience program reads: Identify common Earth materials and interpret their composition, origin and uses. The three underlined words convey the essence of the objective: We ask students to identify and interpret common Earth materials, which begs the questions: Do the common Earth materials provide adequate information for interpreting the composition, origin, and use of Earth materials? Do modern curricula contain enough laboratory time for students to learn to identify Earth materials? Do all geoscientists need to be able to identify Earth materials? The assemblage kyanite plus sillimanite is crucial for interpreting metamorphic history yet they are not common minerals. The IUGS classification contains 179 rock names yet we expect students to identify only a handful of them. The upper mantle is dominated by peridotite yet do geophysicists need to be able to identify peridotite in order to study the upper mantle? All geoscientists should be able to interpret Earth materials, at least at some level, and deduce the information Earth materials provide about Earth history and processes. Only a subset of geoscientists needs to learn how to identify them. Identification skills can be learned in upper level courses designed for those who will become mineral scientists. Many of the interpretations derived from Earth materials can be learned in the lower level courses required of all geoscience students.

Timescales of carbon turnover in soils with mixed crystalline mineralogies

NASA Astrophysics Data System (ADS)

Khomo, Lesego; Trumbore, Susan; Bern, Carleton R.; Chadwick, Oliver A.

2017-01-01

Organic matter-mineral associations stabilize much of the carbon (C) stored globally in soils. Metastable short-range-order (SRO) minerals such as allophane and ferrihydrite provide one mechanism for long-term stabilization of organic matter in young soil. However, in soils with few SRO minerals and a predominance of crystalline aluminosilicate or Fe (and Al) oxyhydroxide, C turnover should be governed by chemisorption with those minerals. Here, we correlate mineral composition from soils containing small amounts of SRO minerals with mean turnover time (TT) of C estimated from radiocarbon (14C) in bulk soil, free light fraction and mineral-associated organic matter. We varied the mineral amount and composition by sampling ancient soils formed on different lithologies in arid to subhumid climates in Kruger National Park (KNP), South Africa. Mineral contents in bulk soils were assessed using chemical extractions to quantify Fe oxyhydroxides and SRO minerals. Because of our interest in the role of silicate clay mineralogy, particularly smectite (2 : 1) and kaolinite (1 : 1), we separately quantified the mineralogy of the clay-sized fraction using X-ray diffraction (XRD) and measured 14C on the same fraction. Density separation demonstrated that mineral associated C accounted for 40-70 % of bulk soil organic C in A and B1 horizons for granite, nephelinite and arid-zone gabbro soils, and > 80 % in other soils. Organic matter strongly associated with the isolated clay-sized fraction represented only 9-47 % of the bulk soil C. The mean TT of C strongly associated with the clay-sized fraction increased with the amount of smectite (2 : 1 clays); in samples with > 40 % smectite it averaged 1020 ± 460 years. The C not strongly associated with clay-sized minerals, including a combination of low-density C, the C associated with minerals of sizes between 2 µm and 2 cm (including Fe oxyhydroxides as coatings), and C removed from clay-sized material by 2 % hydrogen peroxide had TTs averaging 190 ± 190 years in surface horizons. Summed over the bulk soil profile, we found that smectite content correlated with the mean TT of bulk soil C across varied lithologies. The SRO mineral content in KNP soils was generally very low, except for the soils developed on gabbros under more humid climate that also had very high Fe and C contents with a surprisingly short, mean C TTs. In younger landscapes, SRO minerals are metastable and sequester C for long timescales. We hypothesize that in the KNP, SRO minerals represent a transient stage of mineral evolution and therefore lock up C for a shorter time. Overall, we found crystalline Fe-oxyhydroxides (determined as the difference between Fe in dithionate citrate and oxalate extractions) to be the strongest predictor for soil C content, while the mean TT of soil C was best predicted from the amount of smectite, which was also related to more easily measured bulk properties such as cation exchange capacity or pH. Combined with previous research on C turnover times in 2 : 1 vs. 1 : 1 clays, our results hold promise for predicting C inventory and persistence based on intrinsic timescales of specific carbon-mineral interactions.

Spectroscopic Evidence of the Improvement of Reactive Iron Mineral Content in Red Soil by Long-Term Application of Swine Manure

PubMed Central

Huang, Chichao; Liu, Sha; Li, Ruizhi; Sun, Fusheng; Zhou, Ying; Yu, Guanghui

2016-01-01

Mineral elements in soil solutions are thought to be the precursor of the formation of reactive minerals, which play an important role in global carbon (C) cycling. However, information regarding the regulation of mineral elements release in soil is scarce. Here, we examined the long-term (i.e., 23 yrs) effects of fertilisation practices on Fe minerals in a red soil in Southern China. The results from chemical analysis and Fourier-transform infrared spectroscopy showed that long-term swine manure (M) treatment released greater amounts of minerals into soil solutions than chemical fertilisers (NPK) treatment, and Fe played a dominant role in the preservation of dissolved organic C. Furthermore, Fe K-edge X-ray absorption near-edge fine structure spectroscopy demonstrated that reactive Fe minerals were mainly composed of less crystalline ferrihydrite in the M-treated soil and more crystalline goethite in the NPK-treated soil. In conclusion, this study reported spectroscopic evidence of the improvement of reactive Femineral content in the M-treated soil colloids when compared to NPK-treated soil colloids. PMID:26752419

Mercury accumulation in upland acid forest ecosystems nearby a coal-fired power-plant in southwest Europe (Galicia, NW Spain).

PubMed

Nóvoa-Muñoz, J C; Pontevedra-Pombal, X; Martínez-Cortizas, A; García-Rodeja Gayoso, E

2008-05-15

This study was carried out to determine total Hg concentrations (HgT) in acid soils and main plant species in forest ecosystems located in the river Sor catchment, which is located 20 km to the NE of the biggest coal-fired power-plant in southwestern Europe (Galicia, NW Spain). Mercury enrichment factors and Hg inventories were also determined in the soils, which were regularly sampled between 1992 and 2001. The presence of elemental Hg was estimated by simple thermal desorption at 105 degrees C. The highest HgT concentrations occurred in upper soil layers (O and A horizons) with values up to 300 ng g(-1). HgT decreased with depth, achieving the lowest values in the bottommost horizons (i.e. the soil parent material, <6 ng g(-1)), except in podzolic soils. A similar trend occurred for Hg enrichment factors (HgEF) which showed values from 40 to 76 in topsoils. Upper soil mineral horizons (A or AB) made the largest contribution (>50%) to the HgT inventory despite showing lower concentrations than the organic horizons. The role of vegetation in capturing atmospheric Hg and subsequent deposition to soil agrees with the sequence of HgT in plant material: wood

Microbial activities related to C and N cycling and microbial community structure in the rhizospheres of Pinus sylvestris, Picea abies and Betula pendula seedlings in an organic and mineral soil.

PubMed

Priha; Grayston; Pennanen; Smolander

1999-10-01

The aim of this study was to determine whether Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) seedlings have a selective influence on the soil microbial community structure and activity and whether this varies in different soils. Seedlings of pine, spruce and birch were planted into pots of two soil types: an organic soil and a mineral soil. Pots without seedlings were also included. After one growing season, microbial biomass C (C(mic)) and N (N(mic)), C mineralization, net ammonification, net nitrification, denitrification potential, phospholipid fatty acid (PLFA) patterns and community level physiological profiles (CLPPs) were measured in the rhizosphere soil of the seedlings. In the organic soil, C(mic) and N(mic) were higher in the birch rhizosphere than in pine and spruce rhizosphere. The C mineralization rate was not affected by tree species. Unplanted soil contained the highest amount of mineral N and birch rhizosphere the lowest, but rates of net N mineralization and net nitrification did not differ between treatments. The microbial community structure, measured by PLFAs, had changed in the rhizospheres of all tree species compared to the unplanted soil. Birch rhizosphere was most clearly separated from the others. There was more of the fungal specific fatty acid 18:2omega6,9 and more branched fatty acids, common in Gram-positive bacteria, in this soil. CLPPs, done with Biolog GN plates and 30 additional substrates, separated only birch rhizosphere from the others. In the mineral soil, roots of all tree species stimulated C mineralization in soil and prevented nitrification, but did not affect C(mic) and N(mic), PLFA patterns or CLPPs. The effects of different tree species did not vary in the mineral soil. Thus, in the mineral soil, the strongest effect on soil microbes was the presence of a plant, regardless of the tree species, but in the organic soil, different tree species varied in their influence on soil microbes.

Applying transport-distance specific SOC distribution to calibrate soil erosion model WaTEM

NASA Astrophysics Data System (ADS)

Hu, Yaxian; Heckrath, Goswin J.; Kuhn, Nikolaus J.

2016-04-01

Slope-scale soil erosion, transport and deposition fundamentally decide the spatial redistribution of eroded sediments in terrestrial and aquatic systems, which further affect the burial and decomposition of eroded SOC. However, comparisons of SOC contents between upper eroding slope and lower depositional site cannot fully reflect the movement of eroded SOC in-transit along hillslopes. The actual transport distance of eroded SOC is decided by its settling velocity. So far, the settling velocity distribution of eroded SOC is mostly calculated from mineral particle specific SOC distribution. Yet, soil is mostly eroded in form of aggregates, and the movement of aggregates differs significantly from individual mineral particles. This urges a SOC erodibility parameter based on actual transport distance distribution of eroded fractions to better calibrate soil erosion models. Previous field investigation on a freshly seeded cropland in Denmark has shown immediate deposition of fast settling soil fractions and the associated SOC at footslopes, followed by a fining trend at the slope tail. To further quantify the long-term effects of topography on erosional redistribution of eroded SOC, the actual transport-distance specific SOC distribution observed on the field was applied to a soil erosion model WaTEM (based on USLE). After integrating with local DEM, our calibrated model succeeded in locating the hotspots of enrichment/depletion of eroded SOC on different topographic positions, much better corresponding to the real-world field observation. By extrapolating into repeated erosion events, our projected results on the spatial distribution of eroded SOC are also adequately consistent with the SOC properties in the consecutive sample profiles along the slope.

The Relationship Between DOC Partition Coefficient and Mineral Soil C:N Ratio

NASA Astrophysics Data System (ADS)

Aitkenhead-Peterson, J. A.; McDowell, W. H.

2001-12-01

Since our recent publication showing that soil C:N predicts DOC flux at local and global scales, an effort has been made to understand mechanisms controlling the relationship between the two variables. We have approached this at multiple scales, using soil batch experiments, soil column experiments, and long-term field manipulations. We present here the results from our batch adsorption experiment. Mineral soils from tropical (wet and moist) and temperate (coniferous and hardwood) forests were used to assess DOC adsorption by the initial mass isotherm approach. We found that the DOC partition co-efficient (m) which represents a soil's tendency to adsorb DOC is strongly and inversely related to mineral soil C:N ratio (R2 = 0.99 n = 10 p < 0.001). The intercept of the mass isotherm, or the desorption term, was positively related to mineral soil C:N ratio (R2 = 0.80 n = 10 p < 0.01), but we found that desorption of DOC was more closely correlated with equilibrium DOC concentration (R2 = 0.97 n = 10 p < 0.001) than with mineral soil C:N. The mass isotherm approach is also useful in calculating the reactive soil pool (RSP), the fraction of the soil pool of organic carbon that may be lost to leaching. The RSP was not significantly related to mineral soil C:N, but tropical soils tended to have a larger RSP than temperate soils. Although some of the tropical soils came from areas where the natural forest had been cleared, used for plantations and then abandoned, the relationship between DOC adsorption and mineral soil C:N was not compromised. Watershed soil C:N ratio is an excellent predictor of DOC export because soil C:N is related to physiochemical adsorption processes in mineral soils and biotic production of DOC in organic soil horizons. It appears that soil C:N is a relatively robust predictor of soil solution DOC concentration and surface water DOC export for ecosystems undergoing environmental stress.

Potential changes in arctic seasonality and plant communities may impact tundra soil chemistry and carbon dynamics

NASA Astrophysics Data System (ADS)

Crow, S.; Cooper, E.; Beilman, D.; Filley, T.; Reimer, P.

2009-04-01

On the Svalbard archipelago, as in other high Arctic regions, tundra soil organic matter (SOM) is primarily plant detritus that is largely stabilized by cold, moist conditions and low nitrogen availability. However, the resistance of SOM to decomposition is also influenced by the quality of organic matter inputs to soil. Different plant communities are likely to give different qualities to SOM, especially where lignin-rich woody species encroach into otherwise graminoid and bryophyte-dominated regions. Arctic woody plant species are particularly sensitive to changes in temperature, snow cover, and growing season length. In a changing environment, litter chemistry may emerge as an important control on tundra SOM stabilization. In summer 2007, we collected plant material and soil from the highly-organic upper horizon (appx. 0-5 cm) and the mineral-dominated lower horizon (appx. 5-10cm) from four locations in the southwest facing valleys of Svalbard, Norway. The central goal of the ongoing experiment is to determine whether a greater abundance of woody plants could provide a negative feedback to warming impacts on the carbon (C) balance of Arctic soils. Towards this, we used a combination of plant biopolymer analyses (cupric oxide oxidation and quantification of lignin-derived phenols and cutin/suberin-derived aliphatics) and radiocarbon-based estimates of C longevity and mean residence time (MRT) to characterize potential links between plant type and soil C pools. We found that graminoid species regenerate above- and belowground tissue each year, whereas woody species (Cassiope tetragona and Dryas octopetala) regenerated only leaves yearly. In contrast, C within live branches and roots persisted for 15-18 yr on average. Leaves from woody species remained nearly intact in surface litter for up to 20 yr without being incorporated into the upper soil horizon. Leaves from both graminoid and woody species were concentrated in lignin-derived phenols relative to roots, but were dominated by cinnamyl-lignin forms that are easily degraded and thus not likely to persist as SOM. In contrast, roots and branches were comprised of more decay-resistant vanillyl and syringyl forms of lignin-derived phenols. Leaves of woody species were 10 times more concentrated in cutin/suberin-derived aliphatics than roots (which could provide a direct source of potentially stabilized C into the mineral soil). In the upper soil horizon, the MRT of isolated roots and organic debris was about 50 yr and the ‘resistant' C (i.e., C resistant to digestion in 6N HCl acid) was about 500 yr. In the lower soil horizon, the MRT of the ‘resistant' C was about 3500 yr, indicating that long-term C storage occurs in the near-surface layers of Arctic soil where environmental changes are likely to have a strong impact. Observed warming in high latitudes is most pronounced over land and a series of positive feedbacks between climate and net primary productivity are developing. Litter input quality may provide a rare negative feedback within this system and whether these feedbacks will ultimately result in SOM accumulation or losses due to increases in decomposition of older, stabilized C is unknown.

Mechanistic roles of soil humus and minerals in the sorption of nonionic organic compounds from aqueous and organic solutions

USGS Publications Warehouse

Chiou, C.T.; Shoup, T.D.; Porter, P.E.

1985-01-01

Mechanistic roles of soil humus and soil minerals and their contributions to soil sorption of nonionic organic compounds from aqueous and organic solutions are illustrated. Parathion and lindane are used as model solutes on two soils that differ greatly in their humic and mineral contents. In aqueous systems, observed sorptive characteristics suggest that solute partitioning into the soil-humic phase is the primary mechanism of soil uptake. By contrast, data obtained from organic solutions on dehydrated soil partitioning into humic phase and adsorption by soil minerals is influenced by the soil-moisture content and by the solvent medium from which the solute is sorbed. ?? 1985.

Formation and Stability of Microbially Derived Soil Organic Matter

NASA Astrophysics Data System (ADS)

Waldrop, M. P.; Creamer, C.; Foster, A. L.; Lawrence, C. R.; Mcfarland, J. W.; Schulz, M. S.

2017-12-01

Soil carbon is vital to soil health, food security, and climate change mitigation, but the underlying mechanisms controlling the stabilization and destabilization of soil carbon are still poorly understood. There has been a conceptual paradigm shift in how soil organic matter is formed which now emphasizes the importance of microbial activity to build stable (i.e. long-lived) and mineral-associated soil organic matter. In this conceptual model, the consumption of plant carbon by microorganisms, followed by subsequent turnover of microbial bodies closely associated with mineral particles, produces a layering of amino acid and lipid residues on the surfaces of soil minerals that remains protected from destabilization by mineral-association and aggregation processes. We tested this new model by examining how isotopically labeled plant and microbial C differ in their fundamental stabilization and destabilization processes on soil minerals through a soil profile. We used a combination of laboratory and field-based approaches to bridge multiple spatial scales, and used soil depth as well as synthetic minerals to create gradients of soil mineralogy. We used Raman microscopy as a tool to probe organic matter association with mineral surfaces, as it allows for the simultaneous quantification and identification of living microbes, carbon, minerals, and isotopes through time. As expected, we found that the type of minerals present had a strong influence on the amount of C retained, but the stabilization of new C critically depends on growth, death, and turnover of microbial cells. Additionally, the destabilization of microbial residue C on mineral surfaces was little affected by flushes of DOC relative to wet-dry cycles alone. We believe this new insight into microbial mechanisms of C stabilization in soils will eventually lead to new avenues for measuring and modeling SOM dynamics in soils, and aid in the management of soil C to mediate global challenges.

[Effects of simulated nitrogen deposition on organic matter leaching in forest soil].

PubMed

Duan, Lei; ma, Xiao-Xiao; Yu, De-Xiang; Tan, Bing-Quan

2013-06-01

The impact of nitrogen deposition on the dynamics of carbon pool in forest soil was studied through a field experiment at Tieshanping, Chongqing in Southwest China. The changes of dissolved organic matter (DOM) concentration in soil water in different soil layers were monitored for five years after addition of ammonium nitrate (NH4NO3) or sodium nitrate (NaNO3) at the same dose as the current nitrogen deposition to the forest floor. The results indicated that the concentration and flux of dissolved organic carbon (DOC) were increased in the first two years and then decreased by fertilizing. Fertilizing also reduced the DOC/DON (dissolved organic nitrogen) ratio of soil water in the litter layer and the DOC concentration of soil water in the upper mineral layer, but had no significant effect on DOC flux in the lower soil layer. Although there was generally no effect of increasing nitrogen deposition on the forest carbon pool during the experimental period, the shift from C-rich to N-rich DOM might occur. In addition, the species of nitrogen deposition, i. e., NH4(+) and NO3(-), did not show difference in their effect on soil DOM with the same equivalence.

Minerals in soil select distinct bacterial communities in their microhabitats.

PubMed

Carson, Jennifer K; Campbell, Louise; Rooney, Deirdre; Clipson, Nicholas; Gleeson, Deirdre B

2009-03-01

We tested the hypothesis that different minerals in soil select distinct bacterial communities in their microhabitats. Mica (M), basalt (B) and rock phosphate (RP) were incubated separately in soil planted with Trifolium subterraneum, Lolium rigidum or left unplanted. After 70 days, the mineral and soil fractions were separated by sieving. Automated ribosomal intergenic spacer analysis was used to determine whether the bacterial community structure was affected by the mineral, fraction and plant treatments. Principal coordinate plots showed clustering of bacterial communities from different fraction and mineral treatments, but not from different plant treatments. Permutational multivariate anova (permanova) showed that the microhabitats of M, B and RP selected bacterial communities different from each other in unplanted and L. rigidum, and in T. subterraneum, bacterial communities from M and B differed (P<0.046). permanova also showed that each mineral fraction selected bacterial communities different from the surrounding soil fraction (P<0.05). This study shows that the structure of bacterial communities in soil is influenced by the mineral substrates in their microhabitat and that minerals in soil play a greater role in bacterial ecology than simply providing an inert matrix for bacterial growth. This study suggests that mineral heterogeneity in soil contributes to the spatial variation in bacterial communities.

[Runoff loss of soil mineral nitrogen and its relationship with grass coverage on Loess slope land].

PubMed

Zhang, Yali; Li, Huai'en; Zhang, Xingchang; Xiao, Bo

2006-12-01

In a simulated rainfall experiment on Loess slope land, this paper determined the rainfall, surface runoff and the effective depth of interaction (EDI) between rainfall and soil mineral nitrogen, and studied the effects of grass coverage on the EDI and the runoff loss of soil mineral nitrogen. The results showed that with the increase of EDI, soil nitrogen in deeper layers could be released into surface runoff through dissolution and desorption. The higher the grass coverage, the deeper the EDI was. Grass coverage promoted the interaction between surface runoff and surface soil. On the slope land with 60%, 80% and 100% of grass coverage, the mean content of runoff mineral nitrogen increased by 34.52%, 32.67% and 6.00%, while surface runoff decreased by 4.72%, 9.84% and 12.89%, and eroded sediment decreased by 83.55%, 87.11% and 89.01%, respectively, compared with bare slope land. The total runoff loss of soil mineral nitrogen on the lands with 60%, 80%, and 100% of grass coverage was 95.73%, 109.04%, and 84.05% of that on bare land, respectively. Grass cover had dual effects on the surface runoff of soil mineral nitrogen. On one hand, it enhanced the influx of soil mineral nitrogen to surface runoff, and on the other hand, it markedly decreased the runoff, resulting in the decrease of soil mineral nitrogen loss through runoff and sediment. These two distinct factors codetermined the total runoff loss of soil mineral nitrogen.

MECHANISTIC ROLES OF SOIL HUMUS AND MINERALS IN THE SORPTION OF NONIONIC ORGANIC COMPOUNDS FROM AQUEOUS AND ORGANIC SOLUTIONS

EPA Science Inventory

Mechanistic roles of soil humus and soil minerals and their contributions to soil sorption of nonionic organic compounds from aqueous and organic solutions are illustrated. Parathion and lindane are used as model solutes on two soils that differ greatly in their humic and mineral...

Exploration of geo-mineral compounds in granite mining soils using XRD pattern data analysis

NASA Astrophysics Data System (ADS)

Koteswara Reddy, G.; Yarakkula, Kiran

2017-11-01

The purpose of the study was to investigate the major minerals present in granite mining waste and agricultural soils near and away from mining areas. The mineral exploration of representative sub-soil samples are identified by X-Ray Diffractometer (XRD) pattern data analysis. The morphological features and quantitative elementary analysis was performed by Scanning Electron Microscopy-Energy Dispersed Spectroscopy (SEM-EDS).The XRD pattern data revealed that the major minerals are identified as Quartz, Albite, Anorthite, K-Feldspars, Muscovite, Annite, Lepidolite, Illite, Enstatite and Ferrosilite in granite waste. However, in case of agricultural farm soils the major minerals are identified as Gypsum, Calcite, Magnetite, Hematite, Muscovite, K-Feldspars and Quartz. Moreover, the agricultural soils neighbouring mining areas, the minerals are found that, the enriched Mica group minerals (Lepidolite and Illite) the enriched Orthopyroxene group minerals (Ferrosilite and Enstatite). It is observed that the Mica and Orthopyroxene group minerals are present in agricultural farm soils neighbouring mining areas and absent in agricultural farm soils away from mining areas. The study demonstrated that the chemical migration takes place at agricultural farm lands in the vicinity of the granite mining areas.

Soil Organic Matter Stabilization via Mineral Interactions in Forest Soils with Varying Saturation Frequency

NASA Astrophysics Data System (ADS)

Possinger, A. R.; Inagaki, T.; Bailey, S. W.; Kogel-Knabner, I.; Lehmann, J.

2017-12-01

Soil carbon (C) interaction with minerals and metals through surface adsorption and co-precipitation processes is important for soil organic C (SOC) stabilization. Co-precipitation (i.e., the incorporation of C as an "impurity" in metal precipitates as they form) may increase the potential quantity of mineral-associated C per unit mineral surface compared to surface adsorption: a potentially important and as yet unaccounted for mechanism of C stabilization in soil. However, chemical, physical, and biological characterization of co-precipitated SOM as such in natural soils is limited, and the relative persistence of co-precipitated C is unknown, particularly under dynamic environmental conditions. To better understand the relationships between SOM stabilization via organometallic co-precipitation and environmental variables, this study compares mineral-SOM characteristics across a forest soil (Spodosol) hydrological gradient with expected differences in co-precipitation of SOM with iron (Fe) and aluminum (Al) due to variable saturation frequency. Soils were collected from a steep, well-drained forest soil transect with low, medium, and high frequency of water table intrusion into surface soils (Hubbard Brook Experimental Forest, Woodstock, NH). Lower saturation frequency soils generally had higher C content, C/Fe, C/Al, and other indicators of co-precipitation interactions resulting from SOM complexation, transport, and precipitation, an important process of Spodosol formation. Preliminary Fe X-ray Absorption Spectroscopic (XAS) characterization of SOM and metal chemistry in low frequency profiles suggest co-precipitation of SOM in the fine fraction (<20 µm). Short-term (10d) aerobic incubation of high and low saturation frequency soils showed greater SOC mineralization per unit soil C for low saturation frequency (i.e., higher co-precipitation) soils; however, increased mineralization may be attributed to non-mineral associated fractions of SOM. Further work to identify the component of SOM contributing to rapid mineralization using 13C-labeled substrates will link the observed chemical characteristics (13C-NMR, C K-edge XANES, and Fe XAS) of mineral-organic associations resulting from varying saturation frequency with mechanisms driving mineralization processes.

Timescales of carbon turnover in soils with mixed crystalline mineralogies

USGS Publications Warehouse

Khomo, Lesego; Trumbore, Susan E.; Bern, Carleton R.; Chadwick, Oliver A.

2017-01-01

Organic matter–mineral associations stabilize much of the carbon (C) stored globally in soils. Metastable short-range-order (SRO) minerals such as allophane and ferrihydrite provide one mechanism for long-term stabilization of organic matter in young soil. However, in soils with few SRO minerals and a predominance of crystalline aluminosilicate or Fe (and Al) oxyhydroxide, C turnover should be governed by chemisorption with those minerals. Here, we correlate mineral composition from soils containing small amounts of SRO minerals with mean turnover time (TT) of C estimated from radiocarbon (14C) in bulk soil, free light fraction and mineral-associated organic matter. We varied the mineral amount and composition by sampling ancient soils formed on different lithologies in arid to subhumid climates in Kruger National Park (KNP), South Africa. Mineral contents in bulk soils were assessed using chemical extractions to quantify Fe oxyhydroxides and SRO minerals. Because of our interest in the role of silicate clay mineralogy, particularly smectite (2 : 1) and kaolinite (1 : 1), we separately quantified the mineralogy of the clay-sized fraction using X-ray diffraction (XRD) and measured 14C on the same fraction. Density separation demonstrated that mineral associated C accounted for 40–70 % of bulk soil organic C in A and B1 horizons for granite, nephelinite and arid-zone gabbro soils, and > 80 % in other soils. Organic matter strongly associated with the isolated clay-sized fraction represented only 9–47 % of the bulk soil C. The mean TT of C strongly associated with the clay-sized fraction increased with the amount of smectite (2 : 1 clays); in samples with > 40 % smectite it averaged 1020 ± 460 years. The C not strongly associated with clay-sized minerals, including a combination of low-density C, the C associated with minerals of sizes between 2 µm and 2 cm (including Fe oxyhydroxides as coatings), and C removed from clay-sized material by 2 % hydrogen peroxide had TTs averaging 190 ± 190 years in surface horizons. Summed over the bulk soil profile, we found that smectite content correlated with the mean TT of bulk soil C across varied lithologies. The SRO mineral content in KNP soils was generally very low, except for the soils developed on gabbros under more humid climate that also had very high Fe and C contents with a surprisingly short, mean C TTs. In younger landscapes, SRO minerals are metastable and sequester C for long timescales. We hypothesize that in the KNP, SRO minerals represent a transient stage of mineral evolution and therefore lock up C for a shorter time. Overall, we found crystalline Fe-oxyhydroxides (determined as the difference between Fe in dithionate citrate and oxalate extractions) to be the strongest predictor for soil C content, while the mean TT of soil C was best predicted from the amount of smectite, which was also related to more easily measured bulk properties such as cation exchange capacity or pH. Combined with previous research on C turnover times in 2 : 1 vs. 1 : 1 clays, our results hold promise for predicting C inventory and persistence based on intrinsic timescales of specific carbon–mineral interactions.

Thermomagnetic properties of peat-soil layers from Sag pond near Lembang Fault, West Java, Indonesia

NASA Astrophysics Data System (ADS)

Iryanti, Mimin; Wibowo, Dimas Maulana; Bijaksana, Satria

2015-09-01

Sag pond is a body of water near fault system as water flows blocked by the fault. Sag pond is a special type of environment for peat formation as peat layers in were deposited as the fault moves in episodic fashion. Depending on the history of the fault, peat layers are often interrupted by soil layers. In this study, core of peat-soil layers from a Sag pond in Karyawangi Village near Lembang Fault was obtained and analyzed for its magnetic properties. The 5 m core was obtained using a hand auger. Individual samples were obtained every cm and measured for their magnetic susceptibility. In general, there are three distinct magnetic susceptibility layers that were associated with peat and soil layers. The upper first 1 m is unconsolidated mud layer with its relatively high magnetic susceptibility. Between 1-2.81 m, there is consolidated mud layer and the lowest part (2.82-5) m is basically peat layer. Six samples were then measured for their thermomagnetic properties by measuring their susceptibility during heating and cooling from room temperature to 700°C. The thermomagnetic profiles provide Curie temperatures for various magnetic minerals in the cores. It was found that the upper part (unconsolidated mud) contains predominantly iron-oxides, such as magnetite while the lowest part (peat layer) contains significant amount of iron-sulphides, presumably greigite.

Microbiomes structure and diversity in different horizons of full soil profiles

NASA Astrophysics Data System (ADS)

Chernov, Timofey; Tkhakakhova, Azida; Zhelezova, Alena; Semenov, Mikhail; Kutovaya, Olga

2017-04-01

Topsoil is a most common object for soil metagenomic studies; sometimes soil profile is being formally split in layers by depth. However, Russian Soil Science School formulated the idea of soil profile as a complex of soil horizons, which can differ in their properties and genesis. In this research we analyzed 57 genetic soil horizons of 8 different soils from European part of Russia: Albeluvisol, Greyzemic Phaeozem, three Chermozems (different land use - till, fallow, wind-protecting tree line), Rhodic Cambisol, Haplic Kastanozem and Salic Solonetz (WRB classification). Sampling was performed from all genetic horizons in each soil profile starting from topsoil until subsoil. Total DNA was extracted and 16S rRNA sequencing was provided together with chemical analysis of soil (pH measurement, C and N contents, etc.). Structure and diversity of prokaryotic community are significantly different in those soil horizons, which chemical properties and processes of origin are contrasting with nearest horizons: Na-enriched horizon of Solonetz, eluvial horizon of Albeluvisol, plough pan of Agrochernozem. Actinobacteria were abundant in top horizons of soils in warm and dry climate, while Acidobacteria had the highest frequency in soils of moist and cold regions. Concerning Archaea, Thaumarchaeota prevailed in all studied soils. Their rate was higher in microbiomes of upper horizons of steppe soils and it was reducing with depth down the profile. Prokaryotic communities in Chernozems were clustered by soil horizons types: microbiomes of A (organic topsoil) and B (mineral) horizons formed non-overlapping clusters by principal component analysis, cluster formed by prokaryotic communities of transitional soil horizons (AB) take place between clusters of A and B horizons. Moreover, prokaryotic communities of A horizons differ from each other strongly, while microbiomes of B horizons formed a narrow small cluster. It must be explaned by more diverse conditions in upper A horizons. Thus, ecological differences between soil horizons are important factor of differentiation of prokaryotic communities in soil profile; their structure can be specific for horizon type. This study was supported by Russian Science Foundation, project no. 14-26-00079

Long-term carbon exclusion alters soil microbial function but not community structure across forests of contrasting productivity

NASA Astrophysics Data System (ADS)

Hart, S. C.; Dove, N. C.; Stark, J.

2017-12-01

While it is well-documented that distinct heterotrophic microbial communities emerge under different conditions of carbon (C) availability, the response of soil microbial communities and their function to long-term conditions of C exclusion in situ has yet to be investigated. We evaluated the role of C in controlling soil microbial communities and function by experimentally excluding plant C inputs for nine years at four forest sites along a productivity gradient in Oregon, USA. Carbon exclusion treatments were implemented by root trenching to a depth of 30 cm using 25-cm diameter steel pipe, and minimizing aboveground inputs as plant litter by covering the pipe with a 1-mm mesh screen. After nine years, we measured rates of gross and net nitrogen (N) transformations and microbial respiration in situ in the upper 15-cm of mineral soil in both C excluded plots and undisturbed control soils. We measured the soil total C and N concentration and potential extracellular enzyme activities. We used phospholipid fatty acid (PLFA) analysis to determine potential changes in the microbial community structure. Nine years of C exclusion reduced soil total C by about 20%, except at the highest productivity site where no statistically significant change was observed. Although PLFA community structure and microbial C were unchanged, microbial respiration was reduced by 15-45% at all sites. Similarly, specific extracellular enzyme activities for all enzymes increased at these sites with C exclusion, suggesting that the microbial communities were substrate-limited. Although gross N mineralization decreased under C exclusion, decreases in gross N immobilization were greater, resulting in increased net N mineralization rates in all but the lowest productivity site. Furthermore, C exclusion only increased net nitrification in the highest productivity site. Although these field-based results are largely consistent with previous laboratory studies indicating a strong coupling between C and N biogeochemical cycles, they build upon this earlier research by suggesting that the "C connection" to the N cycle depends on the rate of C cycling within the ecosystem.

Fungal and bacterial contributions to nitrogen cycling in cheatgrass-invaded and uninvaded native sagebrush soils of the western USA

USGS Publications Warehouse

DeCrappeo, Nicole; DeLorenze, Elizabeth J.; Giguere, Andrew T; Pyke, David A.; Bottomley, Peter J.

2017-01-01

AimThere is interest in determining how cheatgrass (Bromus tectorum L.) modifies N cycling in sagebrush (Artemisia tridentata Nutt.) soils of the western USA.MethodsTo gain insight into the roles of fungi and bacteria in N cycling of cheatgrass-invaded and uninvaded sagebrush soils, the fungal protein synthesis inhibitor, cycloheximide (CHX), and the bacteriocidal compound, bronopol (BRO) were combined with a 15NH4+ isotope pool dilution approach.ResultsCHX reduced gross N mineralization to the same rate in both sagebrush and cheatgrass soils indicating a role for fungi in N mineralization in both soil types. In cheatgrass soils BRO completely inhibited gross N mineralization, whereas, in sagebrush soils a BRO-resistant gross N mineralization rate was detected that was slower than CHX sensitive gross N mineralization, suggesting that the microbial drivers of gross N mineralization were different in sagebrush and cheatgrass soils. Net N mineralization was stimulated to a higher rate in sagebrush than in cheatgrass soils by CHX, implying that a CHX inhibited N sink was larger in the former than the latter soils. Initial gross NH4+ consumption rates were reduced significantly by both CHX and BRO in both soil types, yet, consumption rates recovered significantly between 24 and 48 h in CHX-treated sagebrush soils. The recovery of NH4+ consumption in sagebrush soils corresponded with an increase in the rate of net nitrification.ConclusionsThese results suggest that cheatgrass invasion of sagebrush soils of the northern Great Basin reduces the capacity of the fungal N consumption sink, enhances the capacity of a CHX resistant N sink and alters the contributions of bacteria and fungi to gross N mineralization.

Spatial distribution of microbial biomass, activity, community structure, and the biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) in the subsurface.

PubMed

Federle, T W; Ventullo, R M; White, D C

1990-12-01

The vertical distribution of microbial biomass, activity, community structure and the mineralization of xenobiotic chemicals was examined in two soil profiles in northern Wisconsin. One profile was impacted by infiltrating wastewater from a laundromat, while the other served as a control. An unconfined aquifer was present 14 meters below the surface at both sites. Biomass and community structure were determined by acridine orange direct counts and measuring concentrations of phospholipid-derived fatty acids (PLFA). Microbial activity was estimated by measuring fluorescein diacetate (FDA) hydrolysis, thymidine incorporation into DNA, and mixed amino acid (MAA) mineralization. Mineralization kinetics of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) were determined at each depth. Except for MAA mineralization rates, measures of microbial biomass and activity exhibited similar patterns with depth. PLFA concentration and rates of FDA hydrolysis and thymidine incorporation decreased 10-100 fold below 3 m and then exhibited little variation with depth. Fungal fatty acid markers were found at all depths and represented from 1 to 15% of the total PLFAs. The relative proportion of tuberculostearic acid (TBS), an actinomycete marker, declined with depth and was not detected in the saturated zone. The profile impacted by wastewater exhibited higher levels of PLFA but a lower proportion of TBS than the control profile. This profile also exhibited faster rates of FDA hydrolysis and amino acid mineralization at most depths. LAS was mineralized in the upper 2 m of the vadose zone and in the saturated zone of both profiles. Little or no LAS biodegradation occurred at depths between 2 and 14 m. LAE was mineralized at all depths in both profiles, and the mineralization rate exhibited a similar pattern with depth as biomass and activity measurements. In general, biomass and biodegradative activities were much lower in groundwater than in soil samples obtained from the same depth.

Agricultural management impact on physical and chemical functions of European peat soils.

NASA Astrophysics Data System (ADS)

Piayda, Arndt; Tiemeyer, Bärbel; Dettmann, Ullrich; Bechtold, Michel; Buschmann, Christoph

2017-04-01

Peat soils offer numerous functions from the global to the local scale: they constitute the biggest terrestrial carbon storage on the globe, form important nutrient filters for catchments and provide hydrological buffer capacities for local ecosystems. Peat soils represent a large share of soils suitable for agriculture in temperate and boreal Europe, pressurized by increasing demands for production. Cultivated peat soils, however, show extreme mineralization rates of the organic substance and turn into hotspots for green house gas emissions, are highly vulnerable to land surface subsidence, soil and water quality deterioration and thus crop failure. The aim of this study is to analyse the impact of past agricultural management on soil physical and chemical functions of peat soils in six European countries. We conducted standardized soil mapping, soil physical/chemical analysis, ground water table monitoring and farm business surveys across 7 to 10 sites in Germany, The Netherlands, Denmark, Estonia, Finland and Sweden. The results show a strong impact of past agricultural management on peat soil functions across Europe. Peat soil under intensive arable land use consistently offer lowest bearing capacities in the upper 10 cm compared to extensive and intensive grassland use, which is a major limiting factor for successful agricultural practice on peat soils. The difference can be explained by root mat stabilization solely, since soil compaction in the upper 25cm is highest under arable land use. A strong decrease of available water capacity and saturated hydraulic conductivity is consequently observed under arable land use, further intensifying hydrological problems like ponding, drought stress and reductions of hydrological buffer capacities frequently present on cultivated peat soils. Soil carbon stocks clearly decrease with increasing land use intensity, showing highest carbon stocks on extensive grassland. This is supported by the degree of decomposition, which is lowest for extensive grass land. Both findings indicate a strong impact of land use intensity and management on soil carbon losses and peat conservation on the European scale. This study provides evidence how functions of peat soils, valuable for successful agricultural production and relevant for climate change mitigation, are impacted by agricultural management.

A comparison of in situ methods for measuring net nitrogen mineralization rates of organic soil amendments.

PubMed

Hanselman, Travis A; Graetz, Donald A; Obreza, Thomas A

2004-01-01

In situ incubation methods may help provide site-specific estimates of N mineralization from land-applied wastes. However, there are concerns about the reliability of the data generated by the various methods due to containment artifacts. We amended a sandy soil with either poultry manure, biosolids, or yard-waste compost and incubated the mixtures using four in situ methods (buried bags, covered cylinders, standard resin traps, and "new" soil-resin traps) and a conventional laboratory technique in plastic bags. Each incubation device was destructively sampled at 45-d intervals for 180 d and net N mineralization was determined by measuring the amount of inorganic N that accumulated in the soil or soil plus resin traps. Containment effects were evaluated by comparing water content of the containerized soil to a field-reference soil column. In situ incubation methods provided reasonable estimates of short-term (< 45 d) N mineralization, but long-term (> 45 d) mineralization data were not accurate due to a variety of problems specific to each technique. Buried bags and covered cylinders did not retain mineralized N due to water movement into and out of the containers. Neither resin method captured all of the mineralized N that leached through the soil columns, but the new soil-resin trap method tracked field soil water content better than all other in situ methods evaluated. With further refinement and validation, the new soil-resin trap method may be a useful in situ incubation technique for measuring net N mineralization rates of organic soil amendments.

Methane Emissions from Natural Gas Vehicles in Beijing, Baoding, and Shijiazhuang, China during CAREBEIJING Field Campaign

NASA Astrophysics Data System (ADS)

Pérez García-Pando, C.; Miller, R. L.; Perlwitz, J. P.; Kok, J. F.; Scanza, R.; Mahowald, N. M.

2014-12-01

Mineral dust created by wind erosion of soil particles is the dominant aerosol by mass in the atmosphere. It exerts significant effects on radiative fluxes, clouds, ocean biogeochemistry, and human health. Models that predict the lifecycle of mineral dust aerosols generally assume a globally uniform mineral composition. However, this simplification limits our understanding of the role of dust in the Earth system, since the effects of dust strongly depend on the particles' physical and chemical properties, which vary with their mineral composition. Hence, not only a detailed understanding of the processes determining the dust emission flux is needed, but also information about its size dependent mineral composition. Determining the mineral composition of dust aerosols is complicated. The largest uncertainty derives from the current atlases of soil mineral composition. These atlases provide global estimates of soil mineral fractions, but they are based upon massive extrapolation of a limited number of soil samples assuming that mineral composition is related to soil type. This disregards the potentially large variability of soil properties within each defined soil type. In addition, the analysis of these soil samples is based on wet sieving, a technique that breaks the aggregates found in the undisturbed parent soil. During wind erosion, these aggregates are subject to partial fragmentation, which generates differences on the size distribution and composition between the undisturbed parent soil and the emitted dust aerosols. We review recent progress on the representation of the mineral and chemical composition of dust in climate models. We discuss extensions of brittle fragmentation theory to prescribe the emitted size-resolved dust composition, and we identify key processes and uncertainties based upon model simulations and an unprecedented compilation of observations.

Dust Composition in Climate Models: Current Status and Prospects

NASA Astrophysics Data System (ADS)

Pérez García-Pando, C.; Miller, R. L.; Perlwitz, J. P.; Kok, J. F.; Scanza, R.; Mahowald, N. M.

2015-12-01

Mineral dust created by wind erosion of soil particles is the dominant aerosol by mass in the atmosphere. It exerts significant effects on radiative fluxes, clouds, ocean biogeochemistry, and human health. Models that predict the lifecycle of mineral dust aerosols generally assume a globally uniform mineral composition. However, this simplification limits our understanding of the role of dust in the Earth system, since the effects of dust strongly depend on the particles' physical and chemical properties, which vary with their mineral composition. Hence, not only a detailed understanding of the processes determining the dust emission flux is needed, but also information about its size dependent mineral composition. Determining the mineral composition of dust aerosols is complicated. The largest uncertainty derives from the current atlases of soil mineral composition. These atlases provide global estimates of soil mineral fractions, but they are based upon massive extrapolation of a limited number of soil samples assuming that mineral composition is related to soil type. This disregards the potentially large variability of soil properties within each defined soil type. In addition, the analysis of these soil samples is based on wet sieving, a technique that breaks the aggregates found in the undisturbed parent soil. During wind erosion, these aggregates are subject to partial fragmentation, which generates differences on the size distribution and composition between the undisturbed parent soil and the emitted dust aerosols. We review recent progress on the representation of the mineral and chemical composition of dust in climate models. We discuss extensions of brittle fragmentation theory to prescribe the emitted size-resolved dust composition, and we identify key processes and uncertainties based upon model simulations and an unprecedented compilation of observations.

Effect of aluminium on dissolved organic matter mineralization in an allophanic and kaolinitic temperate rain forest soil

NASA Astrophysics Data System (ADS)

Merino, Carolina; Matus, Francisco; Fontaine, Sebastien

2016-04-01

Aluminium (Al) and it influence on the mineralization of dissolved organic matter (DOM) and thus on carbon (C) sequestration in forest soils is poorly understood. We hypothesized that an addition of Al to the soil solution beyond a molar Al:C ratio of 0.1, induces precipitation of the organic matter which leads to an excess Al in the soil solution causing an inhibitory effect for growing microorganisms. We investigated the effect of Al concentrations for the potential of C biodegradation at different Al:C ratios from DOM and Ah mineral soil horizons from two temperate rain forest soils from southern Chile. Dissolved organic matter and surface mineral horizons were incubated with initial molar Al:C ratio from 0.08 to 1.38 found under at field conditions. Mineralization was quantified by measurement of C-CO2 evolved during 15 days. Increasing the initial Al:C ratio > 0.12, led to a considerable reduction in mineralization (up to 70%). For Al:C ratio < 0.12, the mineralization rates from DOM and mineral soils were unaffected. Consequently, there would be a considerable reduction in the biodegradation of DOM and thus an increased in the C sequestration in mineral soils with molar Al:C ratio > 0.12. The observed DOM losses in the stream water of pristine southern forests can be explained by increasing the bioavailability of organic C for Al:C ratio < 0.12. Aluminium concentration had a marked effect at the spectral ART-FTIR bands assigned to cellulose-like and aromatic compounds in Ah mineral soil, diminishing the mineralization. The present results were also confirmed by the Al fluorescence using a confocal microscopy.

Soils of Sub-Antarctic tundras: diversity and basic chemical characteristics

NASA Astrophysics Data System (ADS)

Abakumov, Evgeny; Vlasov, Dmitry; Mukhametova, Nadezhda

2014-05-01

Antarctic peninsula is known as specific part of Antarctica, which is characterizes by humid and relatively warm climate of so-called sub Antarctic (maritime) zone. Annual precipitation and long above zero period provides the possibility of sustainable tundra's ecosystem formation. Therefore, the soil diversity of these tundra landscapes is maximal in the whole Antarctic. Moreover, the thickness of parent material debris's is also highest and achieves a 1 or 2 meters as highest. The presence of higher vascular plants Deshampsia antarctica which is considered as one of the main edificators provides the development of humus accumulation in upper solum. Penguins activity provides an intensive soil fertilization and development of plant communities with increased density. All these factors leads to formation of specific and quite diverse soil cover in sub Antarctic tundra's. These ecosystems are presented by following permafrost affected soils: Leptosols, Lithoosols, Crysols, Gleysols, Peats and Ornhitosols. Also the post Ornhitosols are widely spreaded in subantarcic ecosystems, they forms on the penguin rockeries during the plant succession development, leaching of nutrients and organic matter mineralization. "Amphibious" soils are specific for seasonal lakes, which evaporates in the end if Australian summer. These soils have specific features of bio sediments and soils as well. Soil chemical characteristic as well as organic matter features discussed in comparison with Antacrtic continental soil in presentation.

Mineralogy of a perudic Andosol in central Java, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Ranst, Eric; Utami, S. R.; Verdoodt, A.

2008-02-15

We studied the mineralogy of a perudic Andosol developed on the Dieng Tephra Sequence in central Java, Indonesia. The objective was to confirm the presence and determine the origin and stability of 2:1 and interlayered 2:1 phyllosilicates in well-drained Andosols. This was and still is a debated topic in the literature. Total elemental and selective dissolution, as well as microscopic and X-ray diffraction analyses, were performed on the soil samples collected from this site. These analyses confirmed that andic properties were present in the soil samples. The allophane content determined by selective dissolution was 3-4% in the A horizons, andmore » increased to 12-18% in the deeper subsoil horizons. In addition, the clay fraction contained dioctahedral smectite, hydroxy-Al-interlayered 2:1 minerals (HIS), Al-chlorite, kaolinite, pyrophyllite, mica, cristobalite and some gibbsite. The silt and sand fractions were rich in plagioclase and pyroxene. The 2:1 minerals (smectite and pyrophyllite), as well as chlorite and kaolinite were of hydrothermal origin and were incorporated in the tephra during volcanic eruption. Besides desilication during dissolution of unstable minerals, Al interlayering of 2:1 layer silicates was most likely the most prominent pedogenic process. Although hydroxy-Al polymeric interlayers would normally stabilize the 2:1 clay phases, the strong weakening, and even disappearance of the characteristic XRD peaks, indicated instability of these minerals in the upper A horizons due to the perudic and intensive leaching conditions.« less

Nutrient transport and transformation beneath an infiltration basin

USGS Publications Warehouse

Sumner, D.M.; Rolston, D.E.; Bradner, L.A.

1998-01-01

Field experiments were conducted to examine nutrient transport and transformation beneath an infiltration basin used for the disposal of treated wastewater. Removal of nitrogen from infiltrating water by denitrification was negligible beneath the basin, probably because of subsurface aeration as a result of daily interruptions in basin loading. Retention of organic nitrogen in the upper 4.6 m of the unsaturated zone (water table depth of approximately 11 m) during basin loading resulted in concentrations of nitrate as much as 10 times that of the applied treated wastewater, following basin 'rest' periods of several weeks, which allowed time for mineralization and nitrification. Approximately 90% of the phosphorus in treated wastewater was removed within the upper 4.6 m of the subsurface, primarily by adsorption reactions, with abundant iron and aluminum oxyhydroxides occurring as soil coatings. A reduction in the flow rate of infiltrating water arriving at the water table may explain the accumulation of relatively coarse (>0.45 ??m), organic forms of nitrogen and phosphorus slightly below the water table. Mineralization and nitrification reactions at this second location of organic nitrogen accumulation contributed to concentrations of nitrate as much as three times that of the applied treated wastewater. Phosphorus, which accumulated below the water table, was immobilized by adsorption or precipitation reactions during basin rest periods.Field experiments were conducted to examine nutrient transport and transformation beneath an infiltration basin used for the disposal of treated wastewater. Removal of nitrogen from infiltrating water by denitrification was negligible beneath the basin, probably because of subsurface aeration as a result of daily interruptions in basin loading. Retention of organic nitrogen in the upper 4.6 m of the unsaturated zone (water table depth of approximately 11 m) during basin loading resulted in concentrations of nitrate as much as 10 times that of the applied treated wastewater, following basin 'rest' periods of several weeks, which allowed time for mineralization and nitrification. Approximately 90% of the phosphorus in treated wastewater was removed within the upper 4.6 m of the subsurface, primarily by adsorption reactions, with abundant iron and aluminum oxyhydroxides occurring as soil coatings. A reduction in the flow rate of infiltrating water arriving at the water table may explain the accumulation of relatively coarse (>0.45 ??m), organic forms of nitrogen and phosphorus slightly below the water table. Mineralization and nitrification reactions at this second location of organic nitrogen accumulation contributed to concentrations of nitrate as much as three times that of the applied treated wastewater. Phosphorus, which accumulated below the water table, was immobilized by adsorption or precipitation reactions during basin rest periods.

Fe-C interactions and soil organic matter stability in two tropical soils of contrasting parent materials

NASA Astrophysics Data System (ADS)

Coward, E.; Thompson, A.; Plante, A. F.

2014-12-01

The long residence time of soil organic matter (SOM) is a dynamic property, reflecting the diversity of stabilization mechanisms active within the soil matrix. Climate and ecosystem properties act at the broadest scale, while biochemical recalcitrance, physical occlusion and mineral association drive stability at the microscale. Increasing evidence suggests that the stability of SOM is dominated by organo-mineral interactions. However, the 2:1 clays that provide much of the stabilization capacity in temperate soils are typically absent in tropical soils due to weathering. In contrast, these soils may contain an abundance of iron and aluminium oxides and oxyhydroxides, known as short-range-order (SRO) minerals. These SRO minerals are capable of SOM stabilization through adsorption or co-precipitation, a faculty largely enabled by their high specific surface area (SSA). As such, despite their relatively small mass, SRO minerals may contribute substantially to the SOM stabilization capacity of tropical soils. The objective of this work is to characterize and quantify these Fe-C interactions. Surface (0-20 cm) soil samples were taken from 20 quantitative soil pits dug within the Luquillo Critical Zone Observatory in northeast Puerto Rico. Soils were stratified across granodiorite and volcaniclastic parent materials. Four extraction procedures were used to isolate three different forms of Fe-C interactions: sodium pyrophosphate to isolate organo-metallic complexes, hydroxylamine and oxalate to isolate SRO Fe- and Al-hydroxides, and dithionite to isolate crystalline Fe-oxyhydroxides. Extracts were analysed for DOC and Fe and Al concentrations to estimate the amount of SOM associated with each mineral type. Soils were subjected to SSA and solid-phase C analyses before and after extraction to determine the contribution of the various Fe mineral types to soil SSA, and therefore to potential stabilization capacity through organo-mineral complexation. Preliminary results suggest that extracts from granodiorite parent material contain on average twice the Fe than those from volcaniclastic parent material. The removal of SRO minerals reduced SSA in both soil types, and appear to contribute substantially to SOM stabilization compared to the bulk mineral matrix.

Linking annual N2O emission in organic soils to mineral nitrogen input as estimated by heterotrophic respiration and soil C/N ratio.

PubMed

Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

2014-01-01

Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted.

Adsorption of Trametes versicolor laccase to soil iron and aluminum minerals: enzyme activity, kinetics and stability studies.

PubMed

Wu, Yue; Jiang, Ying; Jiao, Jiaguo; Liu, Manqiang; Hu, Feng; Griffiths, Bryan S; Li, Huixin

2014-02-01

Laccases play an important role in the degradation of soil phenol or phenol-like substance and can be potentially used in soil remediation through immobilization. Iron and aluminum minerals can adsorb extracellular enzymes in soil environment. In the present study, we investigated the adsorptive interaction of laccase, from the white-rot fungus Trametes versicolor, with soil iron and aluminum minerals and characterized the properties of the enzyme after adsorption to minerals. Results showed that both soil iron and aluminum minerals adsorbed great amount of laccase, independent of the mineral specific surface areas. Adsorbed laccases retained 26-64% of the activity of the free enzyme. Compared to the free laccase, all adsorbed laccases showed higher Km values and lower Vmax values, indicating a reduced enzyme-substrate affinity and a lower rate of substrate conversion in reactions catalyzed by the adsorbed laccase. Adsorbed laccases exhibited increased catalytic activities compared to the free laccase at low pH, implying the suitable application of iron and aluminum mineral-adsorbed T. versicolor laccase in soil bioremediation, especially in acid soils. In terms of the thermal profiles, adsorbed laccases showed decreased thermal stability and higher temperature sensitivity relative to the free laccase. Moreover, adsorption improved the resistance of laccase to proteolysis and extended the lifespan of laccase. Our results implied that adsorbed T. versicolor laccase on soil iron and aluminum minerals had promising potential in soil remediation. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Soil Minerals Affect Extracellular Enzyme Activities in Cold and Warm Environments

NASA Astrophysics Data System (ADS)

Yang, Z.; Morin, M. M.; Graham, D. E.; Wullschleger, S. D.; Gu, B.

2017-12-01

Extracellular enzymes are mainly responsible for degrading and cycling soil organic matter (SOM) in both cold and warm terrestrial ecosystems. Minerals can play important roles in affecting soil enzyme activities, however, the interactions between enzyme and soil minerals remain poorly understood. In this study, we developed a model soil-enzyme system to examine the mineral effects on a hydrolytic enzyme (i.e., β-glucosidase) under both cold (4°C) and relatively warm (20 and 30°C) conditions. Minerals including iron oxides and clays (e.g., kaolinite and montmorillonite) were used to mimic different types of soils, and enzyme adsorption experiments were conducted to determine the enzyme interactions with different mineral surfaces. Time-series experiments were also carried out to measure enzymatic degradation of the organic substrates, such as cellobiose and indican. We observed that fractions of adsorbed enzyme and the hydrolytic activity were higher on iron oxides (e.g., hematite) compared to kaolinite and montmorillonite at given experimental conditions. The degradation of cellobiose was significantly faster than that of indican in the presence of minerals. We also found that the adsorption of enzyme was not dependent on the mineral surface areas, but was controlled by the mineral surface charge. In addition, temperature increase from 4 to 30°C enhanced mineral-assisted glucosidase hydrolysis by 2 to 4 fold, suggesting greater degradation under warmer environments. The present work demonstrates that the enzyme activity is influenced not only by the soil temperature but also by the surface chemistry of soil minerals. Our results highlight the need to consider the physical and chemical properties of minerals in biogeochemical models, which could provide a better prediction for enzyme-facilitated SOM transformations in terrestrial ecosystems.

Magnetic minerals in soils across the forest-prairie ecotone in NW Minnesota

NASA Astrophysics Data System (ADS)

Maxbauer, D.; Feinberg, J. M.; Fox, D. L.; Nater, E. A.

2016-12-01

Soil pedogenesis results in a complex assemblage of iron oxide minerals that can be disentangled successfully using sensitive magnetic techniques to better delineate specific soil processes. Here, we evaluate the variability in soil processes within forest, prairie, and transitional soils along an 11 km transect of anthropogenically unaltered soils that span the forest-to-prairie ecotone in NW Minnesota. All soils in this study developed on relatively uniform topography, similar glacial till parent material, under a uniform climate, and presumably over similar time intervals. The forest-to-prairie transition zone in this region is controlled by naturally occurring fires, affording the opportunity to evaluate differences in soil processes related to vegetation (forest versus prairie) and burning (prairie and transitional soils). Results suggest that the pedeogenic fraction of magnetite/maghemite in soils is similar in all specimens and is independent of soil type, vegetation, and any effects of burning. Magnetically enhanced horizons have 45% of remanence held by a low-coercivity pedogenic component (likely magnetite/maghemite) regardless of vegetation cover and soil type. Enhancement ratios for magnetic susceptibility and low-field remanences, often used as indicators of pedogenic magnetic minerals, are more variable but remain statistically equivalent across the transect. These results support the hypothesis that pedogenic magnetic minerals in soils mostly reflect ambient climatic conditions regardless of the variability in soil processes related to vegetation and soil type. The non-pedogenic magnetic mineral assemblage shows clear distinctions between the forest, prairie, and transitional soils in hysteresis properties (remanence and coercivity ratios; Mr/Ms and Bc/Bcr, respectively), suggesting that variable processes in these settings influence the local magnetic mineral assemblage, and that it may be possible to use magnetic minerals in paleosols to constrain these processes. This work highlights the importance of isolating the magnetic behavior of pedogenic and non-pedogenic minerals in environmental magnetism studies in order to provide the most rigorous interpretation of past environmental conditions.

Mineral Soil Carbon in Managed Hardwood Forests of the Northeastern US

NASA Astrophysics Data System (ADS)

Vario, C.; Friedland, A.; Hornig, C.

2013-12-01

New England is characterized by extensive forest cover and large reservoirs of soil carbon (C). In northern hardwood forests, mineral soil C can account for up to 50% of total ecosystem C. There has been an increasing demand for forests to serve both as a C sink and a renewable energy source, and effective management of the ecosystem C balance relies on accurate modeling of each compartment of the ecosystem. However, the dynamics of soil C storage with respect to forest use are variable and poorly understood, particularly in mineral soils. For example, current regional models assume C pools after forest harvesting do not change, while some studies suggest that belowground mineral soil C pools can be affected by disturbances at the soil surface. We quantified mineral soil C pools in previously clear-cut stands in seven research or protected forests across New York, New Hampshire, Massachusetts, and Vermont. The ages of the sites sampled ranged from recently cleared to those with no disturbance history, with 21 forest stands represented in the study. Within each research forest studied, physical parameters such as soil type, forest type, slope and land-use history (aside from forest harvest) did not vary between the stands of different ages. Soil samples were collected to a depth of 60 cm below the mineral-organic boundary using a gas-powered augur and 9.5-cm diameter drill bit. Samples were collected in 10-cm increments in shallow mineral soil and 15-cm increments from 30-60 cm depth. Carbon, nitrogen (N), pH, texture and soil mineralogy were measured across the regional sites. At Bartlett Experimental Forest (BEF) in New Hampshire, mineral soil biogeochemistry in cut and uncut sites was studied at a finer scale. Measurements included soil temperature to 55 cm depth, carbon compound analyses using Py-GCMS and soil microbial messenger RNA extractions from mineral soil. Finally, we simulated C dynamics after harvesting by building a model in Stella, with a particular interest in the role that priming effects may play if C is transported from organic to mineral soil layers after forest harvest. Laboratory analyses were conducted at Dartmouth College and at the University of New Hampshire. For the regional study, mineral soil C and N concentrations, and in some cases, pools were highest at locations that had never been harvested. Although sites represented different stages of succession after clearing, there were no significant patterns over time since harvest. At BEF, soil temperature at 55 cm depth in a recently cleared stand was on average 1.5° C higher than surrounding forested sites between June and September, and shallower depths had greater temperature discrepancies. Our model, which was parameterized using published field data from Bartlett and Hubbard Brook forests, showed that inputs of labile C to mineral soil after harvest could prime the decomposition of preexisting mineral soil C and account for up to 40% of the observed difference in C pools between harvested and undisturbed sites.

2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils.

PubMed

Boivin, Arnaud; Amellal, Samira; Schiavon, Michel; van Genuchten, Martinus Th

2005-11-01

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.

Relationship between carbon and nitrogen mineralization in a subtropical soil

NASA Astrophysics Data System (ADS)

Li, Qianru; Sun, Yue; Zhang, Xinyu; Xu, Xingliang; Kuzyakov, Yakov

2014-05-01

In most soils, more than 90% nitrogen is bonded with carbon in organic forms. This indicates that carbon mineralization should be closely coupled with nitrogen mineralization, showing a positive correlation between carbon and nitrogen mineralization. To test this hypothesis above, we conducted an incubation using a subtropical soil for 10 days at 15 °C and 25 °C. 13C-labeled glucose and 15N-labeled ammonium or nitrate was used to separate CO2 and mineral N released from mineralization of soil organic matter and added glucose or inorganic nitrogen. Phospholipid fatty acid (PLFA) and four exoenzymes (i.e. β-1,4- Glucosaminidase, chitinase, acid phosphatase, β-1,4-N- acetyl glucosamine glycosidase) were also analyzed to detect change in microbial activities during the incubation. Our results showed that CO2 release decreased with increasing nitrogen mineralization rates. Temperature did not change this relationship between carbon and nitrogen mineralization. Although some changes in PLFA and the four exoenzymes were observed, these changes did not contribute to changes in carbon and nitrogen mineralization. These findings indicates that carbon and nitrogen mineralization in soil are more complicated than as previously expected. Future investigation should focus on why carbon and nitrogen mineralization are coupled in a negative correlation not in a positive correlation in many soils for a better understanding of carbon and nitrogen transformation during their mineralization.

Response of Microbial Soil Carbon Mineralization Rates to Oxygen Limitations

NASA Astrophysics Data System (ADS)

Keiluweit, M.; Denney, A.; Nico, P. S.; Fendorf, S. E.

2014-12-01

The rate of soil organic matter (SOM) mineralization is known to be controlled by climatic factors as well as molecular structure, mineral-organic associations, and physical protection. What remains elusive is to what extent oxygen (O2) limitations impact overall rates of microbial SOM mineralization (oxidation) in soils. Even within upland soils that are aerobic in bulk, factors limiting O2 diffusion such as texture and soil moisture can result in an abundance of anaerobic microsites in the interior of soil aggregates. Variation in ensuing anaerobic respiration pathways can further impact SOM mineralization rates. Using a combination of (first) aggregate model systems and (second) manipulations of intact field samples, we show how limitations on diffusion and carbon bioavailability interact to impose anaerobic conditions and associated respiration constraints on SOM mineralization rates. In model aggregates, we examined how particle size (soil texture) and amount of dissolved organic carbon (bioavailable carbon) affect O2 availability and distribution. Monitoring electron acceptor profiles (O2, NO3-, Mn and Fe) and SOM transformations (dissolved, particulate, mineral-associated pools) across the resulting redox gradients, we then determined the distribution of operative microbial metabolisms and their cumulative impact on SOM mineralization rates. Our results show that anaerobic conditions decrease SOM mineralization rates overall, but those are partially offset by the concurrent increases in SOM bioavailability due to transformations of protective mineral phases. In intact soil aggregates collected from soils varying in texture and SOM content, we mapped the spatial distribution of anaerobic microsites. Optode imaging, microsensor profiling and 3D tomography revealed that soil texture regulates overall O2 availability in aggregate interiors, while particulate SOM in biopores appears to control the fine-scale distribution of anaerobic microsites. Collectively, our results suggest that texture and particulate organic matter content are useful predictors for the impact of O2 limitations on SOM mineralization rates.

Changes in mineral-associated soil organic carbon pools across a harvested temperate forest chronosequence

NASA Astrophysics Data System (ADS)

MacIntyre, S.; Kellman, L. M.; Gabriel, C. E.; Diochon, A.

2016-12-01

Due to their substantial pool size, changes in mineral soil carbon (C) stores have the potential to generate significant changes in forest soil C budgets. Harvesting represents a significant land use disturbance that can alter soil organic carbon (SOC) stores, with a number of field studies documenting large losses of SOC following clearcut harvesting. However, little is known about how the distribution of SOC changes amongst mineral-associated pools of differing crystallinity following this disturbance. The objective of this study was to quantify changes in mineral-associated SOC pool sizes through depth and time for podzol soils (mineral soil depths of 0-5, 5-10, 10-15, 15-20, 20-35, and 35-50 cm) of a temperate red spruce harvest chronosequence (representing stand ages of 1yr, 15yr, 45yr, 80yr, and 125+yr) in Nova Scotia, Canada. Samples were subjected to a 4-step sequential chemical dissolution to selectively extract C from mineral pools of increasing crystallinity: soluble minerals (deionized water), organo-metal complexes (Na-pyrophosphate), poorly crystalline minerals (hydroxylamine), and crystalline minerals (Na-dithionite HCl). Carbon concentrations were calculated for the solutions acquired during each stage of the selective dissolution process, providing a time series of changes in mineral-associated C through depth and time following harvesting. A loss of SOC from the organo-metal complexed pool following harvesting was observed, particularly in the deeper mineral soil (20-50cm), with this pool dominating the results. In the soluble and poorly crystalline pools, losses of C were also observed from the deeper mineral soil. Of the 5 sites, the 125+yr age class had the highest concentration of SOC associated with crystalline minerals, with the 0-5cm depth stratum holding a large portion of this C. This study may be useful as a model system for understanding how harvesting disturbance alters mineral pool SOM dynamics in humid temperate forest ecosystems.

Sorption-desorption behavior of PCP on soil organic matter and clay minerals.

PubMed

Pu, Xunchi; Cutright, Teresa J

2006-08-01

Pentachlorophenol (PCP) contamination is a severe environmental problem due to its widespread occurrence, toxicity and recalcitrance. In order to gain a better understanding of the fate of PCP in soils, the role of the soil organic matter (SOM) and clay minerals in the PCP sorption-desorption was studied on two bulk field soils, two subsoils (i.e., SOM or clay-removed soil) and two artificial soils. The two field soils used were a silty loam from New Mexico (NM) containing 10% clay and a sandy-clay-loam from Colombia (CO) South America comprised of 18% clay minerals. The bulk CO soil containing kaolinite sorbed significantly less PCP than the NM soil. All soils depicted an apparent hysteresis during sorption. The CO bulk and subsoils desorbed 14-20% and 15-26% of the sorbed PCP respectively whereas the NM bulk and subsoils desorbed only 4-12% and 5-16%, respectively. Experiments conducted with pure clay and artificial soils indicated that the expandable clay minerals were key sorbent material. Additional studies to investigate the interaction between SOM and clay minerals are needed to fully understand sorptive phenomena.

What shapes edaphic communities in mineral and ornithogenic soils of Cierva Point, Antarctic Peninsula?

NASA Astrophysics Data System (ADS)

Mataloni, G.; Garraza, G. González; Bölter, M.; Convey, P.; Fermani, P.

2010-08-01

Three mineral soil and four ornithogenic soil sites were sampled during summer 2006 at Cierva Point (Antarctic Peninsula) to study their bacterial, microalgal and faunal communities in relation to abiotic and biotic features. Soil moisture, pH, conductivity, organic matter and nutrient contents were consistently lower and more homogeneous in mineral soils. Ornithogenic soils supported larger and more variable bacterial abundances than mineral ones. Algal communities from mineral soils were more diverse than those from ornithogenic soils, although chlorophyll- a concentrations were significantly higher in the latter. This parameter and bacterial abundance were correlated with nutrient and organic matter contents. The meiofauna obtained from mineral soils was homogeneous, with one nematode species dominating all samples. The fauna of ornithogenic soils varied widely in composition and abundance. Tardigrades and rotifers dominated the meiofauna at eutrophic O2, where they supported a large population of the predatory nematode Coomansus gerlachei. At site O3, high bacterial abundance was consistent with high densities of the bacterivorous nematodes Plectus spp. This study provides evidence that Antarctic soils are complex and diverse systems, and suggests that biotic interactions (e.g. competition and predation) may have a stronger and more direct influence on community variability in space and time than previously thought.

Microbial community responses in forest mineral soil to compaction, organic matter removal, and vegetation control

Treesearch

Matt D. Busse; Samual E. Beattie; Robert F. Powers; Felipe G. Sanchez; Allan E. Tiarks

2006-01-01

We tested three disturbance hypotheses in young conifer plantations: H1: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity...

Hyperspectral analysis of clay minerals

NASA Astrophysics Data System (ADS)

Janaki Rama Suresh, G.; Sreenivas, K.; Sivasamy, R.

2014-11-01

A study was carried out by collecting soil samples from parts of Gwalior and Shivpuri district, Madhya Pradesh in order to assess the dominant clay mineral of these soils using hyperspectral data, as 0.4 to 2.5 μm spectral range provides abundant and unique information about many important earth-surface minerals. Understanding the spectral response along with the soil chemical properties can provide important clues for retrieval of mineralogical soil properties. The soil samples were collected based on stratified random sampling approach and dominant clay minerals were identified through XRD analysis. The absorption feature parameters like depth, width, area and asymmetry of the absorption peaks were derived from spectral profile of soil samples through DISPEC tool. The derived absorption feature parameters were used as inputs for modelling the dominant soil clay mineral present in the unknown samples using Random forest approach which resulted in kappa accuracy of 0.795. Besides, an attempt was made to classify the Hyperion data using Spectral Angle Mapper (SAM) algorithm with an overall accuracy of 68.43 %. Results showed that kaolinite was the dominant mineral present in the soils followed by montmorillonite in the study area.

Development and application of a soil organic matter-based soil quality index in mineralized terrane of the Western US

USGS Publications Warehouse

Blecker, S.W.; Stillings, Lisa L.; Amacher, M.C.; Ippolito, J.A.; DeCrappeo, N.M.

2013-01-01

Soil quality indices provide a means of distilling large amounts of data into a single metric that evaluates the soil’s ability to carry out key ecosystem functions. Primarily developed in agroecosytems, then forested ecosystems, an index using the relation between soil organic matter and other key soil properties in more semi-arid systems of the Western US impacted by different geologic mineralization was developed. Three different sites in two different mineralization types, acid sulfate and Cu/Mo porphyry in California and Nevada, were studied. Soil samples were collected from undisturbed soils in both mineralized and nearby unmineralized terrane as well as waste rock and tailings. Eight different microbial parameters (carbon substrate utilization, microbial biomass-C, mineralized-C, mineralized-N and enzyme activities of acid phosphatase, alkaline phosphatase, arylsulfatase, and fluorescein diacetate) along with a number of physicochemical parameters were measured. Multiple linear regression models between these parameters and both total organic carbon and total nitrogen were developed, using the ratio of predicted to measured values as the soil quality index. In most instances, pooling unmineralized and mineralized soil data within a given study site resulted in lower model correlations. Enzyme activity was a consistent explanatory variable in the models across the study sites. Though similar indicators were significant in models across different mineralization types, pooling data across sites inhibited model differentiation of undisturbed and disturbed sites. This procedure could be used to monitor recovery of disturbed systems in mineralized terrane and help link scientific and management disciplines.

Modeling of Phenoxy Acid Herbicide Mineralization and Growth of Microbial Degraders in 15 Soils Monitored by Quantitative Real-Time PCR of the Functional tfdA Gene

PubMed Central

Bælum, Jacob; Prestat, Emmanuel; David, Maude M.; Strobel, Bjarne W.

2012-01-01

Mineralization potentials, rates, and kinetics of the three phenoxy acid (PA) herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), and 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), were investigated and compared in 15 soils collected from five continents. The mineralization patterns were fitted by zero/linear or exponential growth forms of the three-half-order models and by logarithmic (log), first-order, or zero-order kinetic models. Prior and subsequent to the mineralization event, tfdA genes were quantified using real-time PCR to estimate the genetic potential for degrading PA in the soils. In 25 of the 45 mineralization scenarios, ∼60% mineralization was observed within 118 days. Elevated concentrations of tfdA in the range 1 × 105 to 5 × 107 gene copies g−1 of soil were observed in soils where mineralization could be described by using growth-linked kinetic models. A clear trend was observed that the mineralization rates of the three PAs occurred in the order 2,4-D > MCPA > MCPP, and a correlation was observed between rapid mineralization and soils exposed to PA previously. Finally, for 2,4-D mineralization, all seven mineralization patterns which were best fitted by the exponential model yielded a higher tfdA gene potential after mineralization had occurred than the three mineralization patterns best fitted by the Lin model. PMID:22635998

Global distribution of minerals in arid soils as lower boundary condition in dust models

NASA Astrophysics Data System (ADS)

Nickovic, Slobodan

2010-05-01

Mineral dust eroded from arid soils affects the radiation budget of the Earth system, modifies ocean bioproductivity and influences human health. Dust aerosol is a complex mixture of minerals. Dust mineral composition has several potentially important impacts to environment and society. Iron and phosphorus embedded in mineral aerosol are essential for the primary marine productivity when dust deposits over the open ocean. Dust also acts as efficient agent for heterogeneous ice nucleation and this process is dependent on mineralogical structure of dust. Recent findings in medical geology indicate possible role of minerals to human health. In this study, a new 1-km global database was developed for several minerals (Illite, Kaolinite, Smectite, Calcite, Quartz, Feldspar, Hematite and Gypsum) embedded in clay and silt populations of arid soils. For the database generation, high-resolution data sets on soil textures, soil types and land cover was used. Tin addition to the selected minerals, phosphorus was also added whose geographical distribution was specified from compiled literature and data on soil types. The developed global database was used to specify sources of mineral fractions in the DREAM dust model and to simulate atmospheric paths of minerals and their potential impacts on marine biochemistry and tropospheric ice nucleation.

[Response of mineralization of dissolved organic carbon to soil moisture in paddy and upland soils in hilly red soil region].

PubMed

Chen, Xiang-Bi; Wang, Ai-Hua; Hu, Le-Ning; Huang, Yuan; Li, Yang; He, Xun-Yang; Su, Yi-Rong

2014-03-01

Typical paddy and upland soils were collected from a hilly subtropical red-soil region. 14C-labeled dissolved organic carbon (14C-DOC) was extracted from the paddy and upland soils incorporated with 14C-labeled straw after a 30-day (d) incubation period under simulated field conditions. A 100-d incubation experiment (25 degrees C) with the addition of 14C-DOC to paddy and upland soils was conducted to monitor the dynamics of 14C-DOC mineralization under different soil moisture conditions [45%, 60%, 75%, 90%, and 105% of the field water holding capacity (WHC)]. The results showed that after 100 days, 28.7%-61.4% of the labeled DOC in the two types of soils was mineralized to CO2. The mineralization rates of DOC in the paddy soils were significantly higher than in the upland soils under all soil moisture conditions, owing to the less complex composition of DOC in the paddy soils. The aerobic condition was beneficial for DOC mineralization in both soils, and the anaerobic condition was beneficial for DOC accumulation. The biodegradability and the proportion of the labile fraction of the added DOC increased with the increase of soil moisture (45% -90% WHC). Within 100 days, the labile DOC fraction accounted for 80.5%-91.1% (paddy soil) and 66.3%-72.4% (upland soil) of the cumulative mineralization of DOC, implying that the biodegradation rate of DOC was controlled by the percentage of labile DOC fraction.

Understanding the eruption mechanisms of the explosive Bellecombe Eruptions on Piton de la Fournaise, La Réunion

NASA Astrophysics Data System (ADS)

Morgan, K.; Ort, M. H.; Di Muro, A.; Parnell, R. A.; Huff, W. D.

2017-12-01

Piton de la Fournaise (PdF) is an active basaltic volcano on La Réunion island. The Bellecombe Tephra was deposited from at least three unusually explosive eruptions between 3000-5000 ka. The Bellecombe eruptions were interpreted recently to have been due to rapid depressurization of the hydrothermal system when a deep fracture opened after lateral, seaward-directed sliding of the eastern flank, late in a large effusive eruption. This project tests this hypothesis by physically, mineralogically, and chemically characterizing the Bellecombe Tephra to look for evidence of the involvement of the PdF hydrothermal system in the eruptions and understand where the eruptions initiated. The Bellecombe tephra consists of three units separated by incipient soils. Both the Upper and Lower Bellecombe deposits are mostly medium to very fine ash. Lower Bellecombe deposits, from the first two eruptions, are mostly beds of glassy ash containing minor lithic grains and olivine crystals. Hydrothermal minerals, mostly smectite, are present in a few Lower Bellecombe beds. Since these minerals are only present in some beds, the smectite formed before deposition rather than as a product of surficial alteration. The Upper Bellecombe deposits record a third eruption and vary between clast-supported crystal- and lithic-rich lapilli beds and ash beds with abundant ash pellets. The crystals are mostly olivine, with lesser pyroxene and plagioclase and sparse hydrothermal quartz. Gabbro and oceanite clasts are abundant and trachytic pumice rare in these deposits. Hydrothermal minerals are common in most Upper Bellecombe beds. The presence of smectite in some of the Lower Bellecombe beds suggests these deposits came from a system below 200 ºC. Clays in the Upper Bellecombe beds - smectite and mixed layer R0 illite/smectite - imply a system at 40-140 ºC. The hydrothermal system was involved, but might not have been the primary impetus for these eruptions, since hydrothermal minerals are not present in all of the beds, but we find no evidence of high temperatures. The lower Bellecombe vent was near the active summit whereas the Upper Bellecombe vent was from a previously more active area, and this may be reflected in the temperatures of the hydrothermal system. The abundant olivine crystals confirm a relation to a large effusive oceanite eruption.

Mineralogy of parent rock and peaty-podzolic soil of Iremel Ridge, Southern Urals

NASA Astrophysics Data System (ADS)

Khalitov, R. M.; Perova, E. N.; Abakumov, E. V.; Suleimanov, R. R.

2017-08-01

The mineralogy of soils and parent rocks of the Iremel Ridge has been studied by the methods of micromorphology, laser diffraction, computed X-ray microtomography, and X-ray fluorescence analysis. In hard rock and soil, the major minerals have been identified: quartz, illite, and a chlorite-group mineral (Fe analogue of sudoite), as well as accessory minerals: monazite, xenotime, rutile, zircon, and florencite. It has been found that chlorite, illite, and quartz are present in all horizons of the studied peaty-podzolic soil. Insignificant amounts of mixed-layered mineral and kaolinite could be suggested in the T and EL horizons of peaty-podzolic soil. The mixed-layered mineral is most probably of soil origin, which is related to the transformation of illites inherited from the parent rock under acidic conditions.

Linking Annual N2O Emission in Organic Soils to Mineral Nitrogen Input as Estimated by Heterotrophic Respiration and Soil C/N Ratio

PubMed Central

Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

2014-01-01

Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted. PMID:24798347

X-ray digital imaging petrography of lunar mare soils: modal analyses of minerals and glasses

NASA Technical Reports Server (NTRS)

Taylor, L. A.; Patchen, A.; Taylor, D. H.; Chambers, J. G.; McKay, D. S.

1996-01-01

It is essential that accurate modal (i.e., volume) percentages of the various mineral and glass phases in lunar soils be used for addressing and resolving the effects of space weathering upon reflectance spectra, as well as for their calibration such data are also required for evaluating the resource potential of lunar minerals for use at a lunar base. However, these data are largely lacking. Particle-counting information for lunar soils, originally obtained to study formational processes, does not provide these necessary data, including the percentages of minerals locked in multi-phase lithic fragments and fused-soil particles, such as agglutinates. We have developed a technique for modal analyses, sensu stricto, of lunar soils, using digital imaging of X-ray maps obtained with an energy-dispersive spectrometer mounted on an electron microprobe. A suite of nine soils (90 to 150 micrometers size fraction) from the Apollo 11, 12, 15, and 17 mare sites was used for this study. This is the first collection of such modal data on soils from all Apollo mare sites. The abundances of free-mineral fragments in the mare soils are greater for immature and submature soils than for mature soils, largely because of the formation of agglutinitic glass as maturity progresses. In considerations of resource utilization at a lunar base, the best lunar soils to use for mineral beneficiation (i.e., most free-mineral fragments) have maturities near the immature/submature boundary (Is/FeO approximately or = 30), not the mature soils with their complications due to extensive agglutination. The particle data obtained from the nine mare soils confirm the generalizations for lunar soils predicted by L.A. Taylor and D.S. McKay (1992, Lunar Planet Sci. Conf. 23rd, pp. 1411-1412 [Abstract]).

Interactive priming of biochar and labile organic matter mineralization in a smectite-rich soil.

PubMed

Keith, Alexandra; Singh, Balwant; Singh, Bhupinder Pal

2011-11-15

Biochar is considered as an attractive tool for long-term carbon (C) storage in soil. However, there is limited knowledge about the effect of labile organic matter (LOM) on biochar-C mineralization in soil or the vice versa. An incubation experiment (20 °C) was conducted for 120 days to quantify the interactive priming effects of biochar-C and LOM-C mineralization in a smectitic clayey soil. Sugar cane residue (source of LOM) at a rate of 0, 1, 2, and 4% (w/w) in combination with two wood biochars (450 and 550 °C) at a rate of 2% (w/w) were applied to the soil. The use of biochars (~ -36‰) and LOM (-12.7‰) or soil (-14.3‰) with isotopically distinct δ(13)C values allowed the quantification of C mineralized from biochar and LOM/soil. A small fraction (0.4-1.1%) of the applied biochar-C was mineralized, and the mineralization of biochar-C increased significantly with increasing application rates of LOM, especially during the early stages of incubation. Concurrently, biochar application reduced the mineralization of LOM-C, and the magnitude of this effect increased with increasing rate of LOM addition. Over time, the interactive priming of biochar-C and LOM-C mineralization was stabilized. Biochar application possesses a considerable merit for long-term soil C-sequestration, and it has a stabilizing effect on LOM in soil.

Spatial distribution of soil properties on a landslide in Taiwan: effects of movement types and vegetation

NASA Astrophysics Data System (ADS)

Lee, Pei-Chen; Cheng, Chih-Hsin

2017-04-01

Landslides are critical natural disturbances in tropical and temperate areas and exert immense impacts on forest ecosystems and soil properties. The impacts of landslides on soil properties not only vary with their movement type, scale, or location but also have great spatial variation inside landslide. In this study, the effects of movement type (erosion and deposition) and succeeding vegetation on soil properties inside a landslide scar were evaluated. The study site was located in Chiufenernshan, central Taiwan. The landslide was triggered by the Chi-Chi Earthquake (Ritch magnitude 7.3) in 1999. A huge amount of waste debris (30 million m3) was moved along the sliding slope (with a tipping degree at 26o) and deposited in the lower parts. Total area size of landslide scar was 200 ha and about 30 - 50 m depth waste material was eroded/deposited in the upper/lower scar areas. After 17 years, the succeeding vegetation varied inside landslide scar. The erosion areas were covered with grass (Miscanthus floridulus) or left barren in some slopes. In contrast, a secondary forest, dominated with Trema orientalis, Lithocarpus konishii, Mallotus paniculatus, and Smilax bracteata, developed in the deposition areas. We collected soil samples in different landscape areas including (i) erosion areas without vegetation, (ii) erosion areas with grass vegetation, (iii) deposition areas, and (iv) adjacent undisturbed areas. Our results indicated that the erosion areas had higher bulk density, rock fragment and pH value, but less soil organic carbon, total nitrogen, total phosphorus and N-mineralization rate than both deposition and adjacent undisturbed areas. The soil properties without vegetation even showed the extreme end compared to the soils with grass vegetation. Soils at the deposition zone had similar rock fragment, bulk density, soil pH, soil organic carbon and N-mineralization rate values to the undisturbed site (p > 0.05). We speculate that movement types could determine the initial establishment of vegetation types and then influence soil properties under vegetation succession. Therefore, both waste movement types and vegetation and their interactions play important roles on soil properties.

Different composition and distribution patterns of mineral-protected versus hydrolyzable lipids in shrubland soils

NASA Astrophysics Data System (ADS)

Cai, Yue; Tang, Zhiyao; Xiong, Gaoming; Xie, Zongqiang; Liu, Zongguang; Feng, Xiaojuan

2017-09-01

Mineral protection is known as an important mechanism stabilizing soil organic carbon (SOC). However, the composition, sources, and variations of mineral-protected SOC remain poorly constrained. To fill this knowledge gap, we used hydrofluoric acid to demineralize soil matrix and compared the sources and distribution of mineral-protected lipids (ML) versus hydrolyzable lipids (HL) of four typical Chinese shrubland soils. ML was found to represent a sizable fraction (9-32%) of total aliphatic lipids (including n-alkanols; n-alkanoic acids; α,ω-alkanedioic acids; hydroxyalkanoic acids; and midchain-substituted acids) in all soils. Based on carbon chain length and branch positions, microbe- and plant-derived lipids were distinguished. No significant difference was found in the ratio of microbe- to plant-derived lipids in ML versus HL, implying that plant and microbial inputs are equally important for the mineral-associated soil lipids. However, ML contained a higher proportion of nonspecific lipids, especially at depths. Furthermore, to evaluate key environmental variable(s) controlling the distribution of different lipid components, a multiple stepwise regression analysis was conducted. Notably, ML was mainly affected by SOC-to-nitrogen ratio instead of mineralogical properties, implying that the accrual of mineral-associated soil lipids relies strongly on organic matter properties. Collectively, our findings provide novel insights on sources and accumulation mechanisms of mineral-protected soil lipids. SOC decomposition and subsequent accretion of degradation products appear to be vital for the sequestration of mineral-associated soil lipids and warrant better recognition in the investigations of stable soil carbon accumulation mechanisms.

Amino acid and N mineralization dynamics in heathland soil after long-term warming and repetitive drought

NASA Astrophysics Data System (ADS)

Andresen, L. C.; Bode, S.; Tietema, A.; Boeckx, P.; Rütting, T.

2015-04-01

Monomeric organic nitrogen (N) compounds such as free amino acids (FAAs) are an important resource for both plants and soil microorganisms and a source of ammonium (NH4+) via microbial FAA mineralization. We compared gross FAA dynamics with gross N mineralization in a Dutch heathland soil using a 15N tracing technique. A special focus was made on the effects of climate change factors warming and drought, followed by rewetting. Our aims were to (1) compare FAA mineralization (NH4+ production from FAAs) with gross N mineralization, (2) assess gross FAA production rate (depolymerization) and turnover time relative to gross N mineralization rate, and (3) assess the effects of a 14 years of warming and drought treatment on these rates. The turnover of FAA in the soil was ca. 3 h, which is almost 2 orders of magnitude faster than that of NH4+ (i.e. ca. 4 days). This suggests that FAA is an extensively used resource by soil microorganisms. In control soil (i.e. no climatic treatment), the gross N mineralization rate (10 ± 2.9 μg N g-1 day-1) was 8 times smaller than the total gross FAA production rate of five AAs (alanine, valine, leucine, isoleucine, proline: 127.4 to 25.0 μg N g-1 day-1). Gross FAA mineralization (3.4 ± 0.2 μg N g-1 day-1) contributed 34% to the gross N mineralization rate and is therefore an important component of N mineralization. In the drought treatment, a 6-29% reduction in annual precipitation caused a decrease of gross FAA production by 65% and of gross FAA mineralization by 41% compared to control. On the other hand, gross N mineralization was unaffected by drought, indicating an increased mineralization of other soil organic nitrogen (SON) components. A 0.5-1.5 °C warming did not significantly affect N transformations, even though gross FAA production declined. Overall our results suggest that in heathland soil exposed to droughts a different type of SON pool is mineralized. Furthermore, compared to agricultural soils, FAA mineralization was relatively less important in the investigated heathland. This indicates more complex mineralization dynamics in semi-natural ecosystems.

Amino acid and N mineralization dynamics in heathland soil after long-term warming and repetitive drought

NASA Astrophysics Data System (ADS)

Andresen, L. C.; Bode, S.; Tietema, A.; Boeckx, P.; Rütting, T.

2014-11-01

Monomeric organic nitrogen (N) such as free amino acids (fAA) is an important resource for both plants and soil microorganisms and is, furthermore, a source of ammonium (NH4+) via microbial fAA mineralization. We compared gross fAA dynamics with gross N mineralization in a Dutch heathland soil using 15N labelling. A special focus was made on the effects of climate change factors warming and drought, followed by rewetting. Our aims were to: (1) compare fAA mineralization (NH4+ production from fAAs) with gross N mineralization, (2) assess gross fAA production rate (depolymerization) and turnover time relative to gross N mineralization rate, and (3) assess the effects of warming and drought on these rates. The turnover of fAA in the soil was ca. 3 h, which is almost two orders of magnitude faster than that of NH4+ (i.e. ca. 4 days). This suggests that fAAs is an extensively used resource by soil microorganisms. In control soil (i.e. no climatic treatment), the gross N mineralization rate (10 ± 2.9 μg N g-1 day-1) was eight-times smaller than the summed gross fAA production rate of five AAs (alanine, valine, leucine, isoleucine, proline: 127.4 to 25.0 μg N g-1 day-1). Gross fAA mineralization (3.4 ± 0.2 μg N g-1 day-1) contributed by 34% to the gross N mineralization rate and is, thus, an important component of N mineralization. In the drought treatment, gross fAA production was reduced by 65% and gross fAA mineralization by 41%, compared to control. On the other hand, gross N mineralization was unaffected by drought, indicating an increased mineralization of other soil organic nitrogen (SON) components. Warming did not significantly affect N transformations, even though that gross fAA production was more than halved. Overall our results suggest that heathland soil exposed to droughts has a shift in the composition of the SON being mineralized. Furthermore, compared to agricultural soils, fAA mineralization was relatively less important in the investigated heathland. This indicates a more complex mineralization dynamics in semi-natural ecosystems.

Monitoring aggregate disintegration with laser diffraction: A tool for studying soils as sediments

NASA Astrophysics Data System (ADS)

Mason, Joseph; Kasmerchak, Chase; Liang, Mengyu

2016-04-01

One of the more important characteristics of soil that becomes hillslope, fluvial, or aeolian sediment is the presences of aggregates, which disintegrate at varying rates and to varying degrees during transport. Laser diffraction particle size analyzers allow monitoring of aggregate disintegration as a sample of soil or sediment suspended in water is circulated continuously through the measurement cell (Bieganowski et al., 2010, Clay Minerals 45-23-34; Mason et al., Catena 87:107-118). Mason et al. (2011) applied this approach to aeolian sedimentary aggregates (e.g. clay pellets eroded from dry lakebeds), immersing dry samples in DI water and circulating them through a Malvern Mastersizer 2000 particle size analyzer for three hours while repeated size distribution (SD) measurements were made. A final measurement was made after sonication and treatment with Na-metaphosphate. In that study, most samples approached a steady SD within three hours, which included both primary mineral grains and persistent aggregates. The disintegration process could be modeled with a first-order rate law representing the disintegration of a single population of aggregates. A wide range of model parameters were observed among the samples studied, and it was suggested that they could be useful in predicting the behavior of these aggregates, under rainfall impact and during slopewash or fluvial transport. Addition of Ca++ to the suspension altered aggregate behavior in some but not all cases. We applied the same method to dry, unground material from upper horizons of soils sampled along a bioclimatic gradient in northern Minnesota, USA, all formed in lithologically similar glacigenic sediment. These ranged from Alfisols (Luvisols) formed under forest since the last deglaciation, to Alfisols under forest that more recently replaced grassland, and Mollisols (Chernozems) that formed entirely under grassland vegetation. Few of these soil samples approached a steady SD within three hours, and modeling aggregate disintegration required the assumption of at least two aggregate populations. Upper horizons of soils formed under grassland displayed relatively slow disintegration throughout the procedure, with a large proportion of aggregates remaining after three hours. E horizons from forest soils, with low organic matter (OM) and clay content, displayed rapid early distintegration of a large portion of the aggregates, followed by much slower breakdown of the remainder (i.e. the two populations modeled had very different rate constants). OM content is clearly the overriding control on aggregate behavior, but we are also exploring effects of clay content and mineralogy, cation chemistry, and other factors. The differences in aggregate behavior are likely to be relevant to transport and deposition of sediment eroded from these soils, and possibly to the transport of OM or nutrients with eroded soil. We hope to incorporate this method into ongoing field studies of soil erosion with colleagues at UW-Madison.

Spatial variation in microbial processes controlling carbon mineralization within soils and sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fendorf, Scott; Kleber, Markus; Nico, Peter

Soils have a defining role in global carbon cycling, having one of the largest dynamic stocks of C on earth—3300 Pg of C are stored in soils, which is three-times the amount stored in the atmosphere and more than the terrestrial land plants. An important control on soil organic matter (SOM) quantities is the mineralization rate. It is well recognized that the rate and extent of SOM mineralization is affected by climatic factors and mineral-organic matter associations. What remained elusive is to what extent constraints on microbial metabolism induced by the respiratory pathway, and specifically the electron acceptor in respiration,more » control overall rates of carbon mineralization in soils. Therefore, physical factors limiting oxygen diffusion such as soil texture and aggregate size (soil structure) may therefore be central controls on C mineralization rates. The goal of our research was therefore to determine if variations in microbial metabolic rates induced by anaerobic microsites in soils are a major control on SOM mineralization rates and thus storage. We performed a combination of laboratory experiments and field investigations will be performed to fulfill our research objectives. We used laboratory studies to examine fundamental factors of respiratory constraints (i.e., electron acceptor) on organic matter mineralization rates. We ground our laboratory studies with both manipulation of field samples and in-field measurements. Selection of the field sites is guided by variation in soil texture and structure while having (other environmental/soil factors constant. Our laboratory studies defined redox gradients and variations in microbial metabolism operating at the aggregate-scale (cm-scale) within soils using a novel constructed diffusion reactor. We further examined micro-scale variation in terminal electron accepting processes and resulting C mineralization rates within re-packed soils. A major outcome of our research is the ability to quantitatively place the importance of aggregate-based heterogeneity in microbial redox processes and the resulting lack of oxygen on the rate of carbon mineralization. Collectively, our research shows that anaerobic microsites are prevalent in soils and are important regulators of soil carbon persistence, shifting microbial metabolism to less efficient anaerobic respiration and selectively protecting otherwise bioavailable, reduced organic compounds such as lipids and waxes from decomposition. Further, shifting from anaerobic to aerobic conditions leads to a 10-fold increase in volume-specific mineralization rate, illustrating the sensitivity of anaerobically protected carbon to disturbance. Vulnerability of anaerobically protected carbon to future climate or land use change thus constitutes a yet unrecognized soil carbon-climate feedback that should be incorporated into terrestrial ecosystem models.« less

Soil carbon storage following road removal and timber harvesting in redwood forests

USGS Publications Warehouse

Seney, Joseph; Madej, Mary Ann

2015-01-01

Soil carbon storage plays a key role in the global carbon cycle and is important for sustaining forest productivity. Removal of unpaved forest roads has the potential for increasing carbon storage in soils on forested terrain as treated sites revegetate and soil properties improve on the previously compacted road surfaces. We compared soil organic carbon (SOC) content at several depths on treated roads to SOC in adjacent second-growth forests and old-growth redwood forests in California, determined whether SOC in the upper 50 cm of soil varies with the type of road treatment, and assessed the relative importance of site-scale and landscape-scale variables in predicting SOC accumulation in treated road prisms and second-growth redwood forests. Soils were sampled at 5, 20, and 50 cm depths on roads treated by two methods (decommissioning and full recontouring), and in adjacent second-growth and old-growth forests in north coastal California. Road treatments spanned a period of 32 years, and covered a range of geomorphic and vegetative conditions. SOC decreased with depth at all sites. Treated roads on convex sites exhibited higher SOC than on concave sites, and north aspect sites had higher SOC than south aspect sites. SOC at 5, 20, and 50 cm depths did not differ significantly between decommissioned roads (treated 18–32 years previous) and fully recontoured roads (treated 2–12 years previous). Nevertheless, stepwise multiple regression models project higher SOC developing on fully recontoured roads in the next few decades. The best predictors for SOC on treated roads and in second-growth forest incorporated aspect, vegetation type, soil depth, lithology, distance from the ocean, years since road treatment (for the road model) and years since harvest (for the forest model). The road model explained 48% of the variation in SOC in the upper 50 cm of mineral soils and the forest model, 54%

Estimation of Soil Erosion by Using Magnetic Method: A Case Study of an Agricultural Field in Southern Moravia (Czech Republic)

NASA Astrophysics Data System (ADS)

Petrovsky, E.; Grison, H.; Kapicka, A.; Dlouha, S.; Kodesova, R.; Jaksik, O.

2013-05-01

In this study we have applied magnetism of soils for estimation of erosion at an agricultural land. The testing site is situated in loess region in Southern Moravia (in Central Europe). The approach is based on well-established method of differentiation of magnetic parameters of the topsoil and the subsoil horizons as a result of in situ formation of strongly magnetic iron oxides. Our founding is established on a simple tillage homogenization model described by Royall (2001) using magnetic susceptibility and its frequency dependence to estimate soil loss caused by the tillage and subsequent erosion. The original dominant Soil Unit in the investigated area is Haplic Chernozem, which is due to intensive erosion progressively transformed into different Soil Units. The site is characterized by a flat upper part while the middle part, formed by a substantive side valley, is steeper (up to 15°). The side valley represents a major line of concentrated runoff emptying into a colluvial fan. Field measurements of the topsoil volume magnetic susceptibility were carried out by the Bartington MS2D probe. Data are resulting in regular grid of 101 data points, where the bulk soil material was gathered for further laboratory investigations. Moreover, vertical distribution of magnetic susceptibility (deep to 40 cm) was measured on selected transects using the SM400 kappameter. In the laboratory, after drying and sieving of collected soil samples, mass-specific magnetic susceptibility and its frequency-dependent susceptibility was measured. In order to identify magnetic minerals the thermomagnetic analyses were performed using the AGICO KLY-4S Kappabridge with CS-3 furnace. Hysteresis loops were carried out on vibrating magnetometer ADE EV9 to assess the grain-size distribution of ferrimagnetic particles. Hereafter, the isothermal remanent magnetization acqusition followed by D.C. demagnetization were done. All these laboratory magnetic measurements were performed in order to compare differences along soil profiles including A, B horizons and undisturbed soil, which is fundamental for magnetic estimation of soil loss. Regression analysis was used to evaluate correlations between magnetic parameters and some chemical properties of soil. For example, higher values of magnetic susceptibility and organic carbon content were measured at the flat upper part, where the original top horizon remained. On the steep valley side these values were much lower, because the original topsoil was eroded and mixed by tillage with the soil substrate (loess). The result confirm positive correlation (R2=0.89) between values of organic carbon content and volume magnetic susceptibility. This study was supported by NAZV Agency of the Ministry of Agriculture of the Czech Republic through grant NO. QJ1230319. References: Royall, D. (2001). Use of mineral magnetic measurements to investigate soil erosion and sediment delivery in a small agricultural catchment in limestone terrain. Catena, 46, 15-34.

A disconnect between O horizon and mineral soil carbon - Implications for soil C sequestration

NASA Astrophysics Data System (ADS)

Garten, Charles T., Jr.

2009-03-01

Changing inputs of carbon to soil is one means of potentially increasing carbon sequestration in soils for the purpose of mitigating projected increases in atmospheric CO 2 concentrations. The effect of manipulations of aboveground carbon input on soil carbon storage was tested in a temperate, deciduous forest in east Tennessee, USA. A 4.5-year experiment included exclusion of aboveground litterfall and supplemental litter additions (three times ambient) in an upland and a valley that differed in soil nitrogen availability. The estimated decomposition rate of the carbon stock in the O horizon was greater in the valley than in the upland due to higher litter quality (i.e., lower C/N ratios). Short-term litter exclusion or addition had no effect on carbon stock in the mineral soil, measured to a depth of 30 cm, or the partitioning of carbon in the mineral soil between particulate- and mineral-associated organic matter. A two-compartment model was used to interpret results from the field experiments. Field data and a sensitivity analysis of the model were consistent with little carbon transfer between the O horizon and the mineral soil. Increasing aboveground carbon input does not appear to be an effective means of promoting carbon sequestration in forest soil at the location of the present study because a disconnect exists in carbon dynamics between O horizon and mineral soil. Factors that directly increase inputs to belowground soil carbon, via roots, or reduce decomposition rates of organic matter are more likely to benefit efforts to increase carbon sequestration in forests where carbon dynamics in the O horizon are uncoupled from the mineral soil.

[Seasonal dynamics of soil organic carbon mineralization for two forest types in Xiaoxing'an Mountains, China].

PubMed

Gao, Fei; Lin, Wei; Cui, Xiao-yang

2016-01-01

To investigate the seasonal dynamics of soil organic carbon (SOC) mineralization in Xiaoxing'an Mountain, we incubated soil samples collected from virgin Korean pine forest and broad-leaved secondary forest in different seasons in the laboratory and measured the SOC mineralization rate and cumulative SOC mineralization (Cm). We employed simultaneous reaction model to describe C mineralization kinetics and estimated SOC mineralization parameters including soil easily mineralizable C (C1), potentially mineralizable C (C₀). We also analyzed the relations between Cm, C₁and their influencing factors. Results showed that the incubated SOC mineralization rate and Cm for 0-5 cm soil layer decreased from early spring to late autumn, while for 5-10 cm soil layer the seasonal variation was not statistically significant for both forest types. The C₁ in 0-5 and 5-10 cm soil layers varied from 42.92-92.18 and 19.23-32.95 mg kg⁻¹, respectively, while the C₀ in 0-5 and 5-10 cm soil layers varied from 863.92-3957.15 and 434.15-865.79 mg · kg⁻¹, respec- tively. Both C₁ and C₀ decreased from early spring to late autumn. The proportions of C₀ in SOC for two forest types were 0.74%-2.78% and 1.11%-1.84% in 0-5 and 5-10 cm soil layers, respectively, and decreased from early spring to late autumn, indicating that SOC tended to become more stable as a whole from spring to autumn. The Cm and C₀ were significantly positively correlated to in situ soil water content and hot water-extractable carbohydrate content, but were not correlated to in situ soil temperature and cool water-extractable carbohydrate content. We concluded that soil labile organic carbon, soil physical and chemical properties contributed to the seasonal dynamics of SOC mineralization in the forests.

Influence of redox fluctuations and rainfall on pedogenic iron alteration and soil magnetic properties (Invited)

NASA Astrophysics Data System (ADS)

Thompson, A.; Rancourt, D.; Chadwick, O.; Chorover, J. D.

2009-12-01

Soil iron mineral composition emerges from a dynamic interplay between processes causing selective mineral addition/removal (both physically and chemically-driven) and processes affecting in situ mineral transformation. Discerning the influence of these pedogenic processes in a temporally integrated manner is fundamentally relevant to many biogeochemical questions. Among them is to what extent the Fe-mineral system can be used to constrain paleo-interpretations of oceanic sediments and geological deposits. Here we describe results from field and laboratory experiments designed to explore the effects of variable redox conditions on soil iron mineral transformation. Our experimental systems include: (1) a climate gradient of basaltic soils from the island of Maui, HI (MCG) with a documented decrease in Eh. and (2) laboratory incubations where we subjected soil slurries to a series of bacterially-driven reduction-oxidation cycles. Our prior work in these systems examining the iron isotopic and mineral composition will be combined with in-progress analysis of magnetic susceptibility. Current results indicate that across the field gradient (MCG) we find average increases of 0.56‰±0.09‰ δ56Fe for the surface and subsurface soils that correlate very well (R2=0.88) with 57Fe Mössbauer-determined Fe-oxyhydroxide fraction. Such a correlation is difficult to explain on the basis of strict parameter co-variation with rainfall, and suggests isotopic and mineral composition may be coupled through in situ mineral transformation processes in these soils. In our soil slurry incubation experiments we reported previously that repeated redox oscillations generate a cumulative increase in Fe mineral crystallinity. Integration of these results with magnetic susceptibility measurements will provide the context for discussing how dynamic redox processes alter soil magnetic properties most often drawn on for paleoclimate interpretations.

Beryllium geochemistry in soils: Evaluation of 10Be/9Be ratios in authigenic minerals as a basis for age models

USGS Publications Warehouse

Barg, E.; Lal, D.; Pavich, M.J.; Caffee, M.W.; Southon, J.R.

1997-01-01

Soils contain a diverse and complex set of chemicals and minerals. Being an 'open system', both in the chemical and nuclear sense, soils have defied quantitative nuclear dating. However, based on the published studies of the cosmogenic atmospheric 10Be in soils, its relatively long half-life (1.5 Ma), and the fact that 10Be gets quickly incorporated in most soil minerals, this radionuclide appears to be potentially the most useful for soil dating. We therefore studied the natural variations in the specific activities of 10Be with respect to the isotope 9Be in mineral phases in eight profiles of diverse soils from temperate to tropical climatic regimes and evaluated the implications of the data for determining the time of formation of soil minerals, following an earlier suggestion [Lal et al., 1991. Development of cosmogenic nuclear methods for the study of soil erosion and formation rates. Current Sci. 61, 636-639.]. We find that the 10Be/9Be ratios in both bulk soils and in the authigenic mineral phases are confined within a narrower range than in 10Be concentrations. Also, the highest 10Be/9Be ratios in authigenic minerals are observed at the soil-rock interface as predicted by the model. We present model 10Be/9Be ages of the B-horizon and the corresponding soil formation rates for several soil profiles. The present study demonstrates that the 10Be/9Be ratios in the authigenic phases, e.g. clay and Fe-hydroxides, can indeed be used for obtaining useful model ages for soils younger than 10-15 Ma. However, the present work has to be pushed considerably further, to take into account more realistic age models in which, for instance, downward transport of 10Be and clays, and in-situ dissolution of clay minerals at depths, altering the 10Be/9Be ratios of the acidic solutions, are included. We show that in the case of younger soils (< 1 Ma) studied here, their 10Be inventories and 10Be/9Be ratios have been significantly disturbed possibly by mixing with transported soils. ?? 1997 Elsevier Science B.V.

Long term drainage alters plant biodiversity and soil C- and N-storage

NASA Astrophysics Data System (ADS)

Wolf, K.; Bol, R.; Dungait, J. A. J.; Dixon, L.; Dhanoa, D.; Beaumont, D.; Wiesenberg, G. L. B.

2012-04-01

Moisture and slope position can have a strong influence on soil properties and plant communities. In a long term permanent grassland experiment, sub-surface drainage was introduced in 1982 on some plots of Rowden Moor at North Wyke (SW UK). The soil is a Stagnic vertic Cambisol with a dense clay layer at shallow depth. After drainage the plant community had shifted from a Lolium perenne dominated grassland with patches of Juncus sp. towards a typical grassland plant community dominated by Lolium perenne and Trifolium sp. In addition, soil carbon and nitrogen concentrations significantly decreased. This is related to a smaller contribution of plant-derived organic matter to soil due to the change in plant community structure, and the enhanced mineralization of soil organic matter (SOM) under lower soil moisture. However, for C:N ratios neither plants nor soil did reveal any drainage related change arguing for an identical degradability of plant and soil organic matter. Furthermore the δ13C values tend to get more negative in soil, which could be related to the changing plant community. For δ15N no changes were observed, which was surprising as increase δ15N values were expected due to the increase in legumes on the drained plot. Changes in the chemical composition of SOM were also examined using compositional changes of soil n-alkanes. A shift in the alkane abundance occurs from the upper part of the slope (dominated by n-C31), to the bottom parts (n-C29 enriched). The carbon preference index and average chain length of alkanes correlated between undrained and drained plots and decreased down slope. Similarly, several alkane ratios like n-C27/n-C31 declined, due to the enhanced mineralization. Hence, the molecular pattern changed on the one hand due to changing contribution of plant derived organic matter and on the other hand because of changing preservation of organic matter in soil. The study showed that drainage has a long term effect on the plant community leading to depletion in C- and N-contents and a change in the chemical composition of SOM.

The relative abundance of predicted genes associated with ammonia-oxidation, nitrate reduction, and biomass decomposition in mineral soil are altered by intensive timber harvest.

NASA Astrophysics Data System (ADS)

Mushinski, R. M.; Zhou, Y.; Gentry, T. J.; Boutton, T. W.

2017-12-01

Forest ecosystems in the southern United States are substantially altered by anthropogenic disturbances such as timber harvest and land conversion, with effects being observed in carbon and nutrient pools as well as biogeochemical processes. Furthermore, the desire to develop renewable energy sources in the form of biomass extraction from logging residues may result in alterations in soil community structure and function. While the impact of forest management on soil physicochemical properties of the region has been studied, its' long-term effect on soil bacterial community composition and metagenomic potential is relatively unknown, especially at deeper soil depths. This study investigates how intensive organic matter removal intensities associated with timber harvest influence decadal-scale alterations in bacterial community structure and functional potential in the upper 1-m of the soil profile, 18 years post-harvest in a Pinus taeda L. forest of eastern Texas. Amplicon sequencing of the 16S rRNA gene was used in conjunction with soil chemical analyses to evaluate treatment-induced differences in community composition and potential environmental drivers of associated change. Furthermore, functional potential was assessed by using amplicon data to make metagenomic predictions. Results indicate that increasing organic matter removal intensity leads to altered community composition and the relative abundance of dominant OTUs annotated to Burkholderia and Aciditerrimonas. The relative abundance of predicted genes associated with dissimilatory nitrate reduction and denitrification were highest in the most intensively harvested treatment while genes involved in nitrification were significantly lower in the most intensively harvested treatment. Furthermore, genes associated with glycosyltransferases were significantly reduced with increasing harvest intensity while polysaccharide lyases increased. These results imply that intensive organic matter removal may create long-term alterations in bacterial community structure with concurrent alterations to mineral soil carbon and nutrient cycling which may have future consequences on forest regeneration and subsequent stand productivity.

Assessment of bioavailability of pesticides in soils and identification of pesticide degradation drivers using the in-situ Mass Distribution Quotient (iMDQ)

NASA Astrophysics Data System (ADS)

Folberth, Christian

2010-05-01

The in-situ Mass Distribution Quotient (iMDQ) has recently been shown to reliably describe the bioavailability and mineralization of the widely applied pesticide isoproturon in agricultural soils. It is determined by pore water extraction from previously incubated soil samples and subsequent assessment of the mass distribution between solid and liquid phase. The method was verified by comparing the bioavailability with co-metabolic mineralization in soils under optimum microbial soil conditions (water tension -15 kPa and bulk density 1.3 g cm-3). A comparison of the results with the chemical partitioning assessed by the Kd method has shown a higher accuracy of the new method. By combining the iMDQ/pore water extraction method with mineralization of the pesticide under optimum microbial conditions in the soils, further information about mineralization and degradation processes could be obtained or confirmed: a) Metabolically outstanding soils could be identified due to inconsistency between bioavailability and mineralization when compared to the co-metabolic soils. In a metabolically hampered soil, the mineralization was very low compared to the bioavailability and in a soil with metabolically IPU degrading microorganisms the mineralization was extremely high despite low bioavailability. b) Analysis of metabolite patterns in soil water fractions of a degradation experiment allowed for an additional identification of the metabolic status of the soil. In co-metabolic soils, the diversity of metabolites increased proportionally with the degree of mineralization of the parent compound, whereas in a metabolically hampered soil the metabolite pattern was very diverse despite low mineralization. c) A quite stable fractioning between total mineralization of the parent compound to CO2 and build-up of non-extractable bound residues was found. This is a hint that also during co-metabolic degradation that can up to now not be attributed to a certain group of microorganisms, very similar processes take place in different soils. d) It could be shown that soil parameters governing the bioavailability of the compound differ between soils. Although TOC and pH could again be identified as the most important factors for the sorption strength of soils towards isoproturon, the bioavailability itself was driven by a combination of water content and sorption strength that was unique for each soil sample. f) The partitioning of parent compound and primary metabolites remained quite stable during the degradation and mineralization. Further investigations focusing on the microbial side of co-metabolic degradation are in progress. In the future, the method could be used to investigate more compounds, the effectiveness of methods to increase bioavailability in-situ without the need for degradation experiments, and the identification and analysis of degradation pathways in-situ. Other processes that are important for risk assessment, like leaching, have already been investigated with similar methods.

Do Forest Age and Soil Depth Affect Carbon and Nitrogen Adsorption in Mineral Horizons?

NASA Astrophysics Data System (ADS)

Spina, P. G.; Lovett, G. M.; Fuss, C. B.; Goodale, C. L.; Lang, A.; Fahey, T.

2015-12-01

Mineral soils retain large amounts of organic matter through sorption on the surfaces of mineral soils, the largest pools of carbon (C) and nitrogen (N) in the forests of the northeastern U.S. In addition to determining organic matter storage, adsorption and desorption processes are important controllers of runoff chemistry. We are studying adsorption dynamics of mineral soils collected from a chronosequence of hardwood forest sites in the White Mountains, NH to determine how soils vary in their DOM adsorption capacities as a function of effective C and N saturation. We hypothesize that forest age determines proximity to saturation because young forests may need to mine soil organic matter (SOM) in mineral soils to obtain nitrogen to meet growth demands, while the soils of older forests have had time to reaccumulate SOM, eventually reaching C and N saturation. Consequently, we expect adsorption capacities to first increase with forest age in young forests, as the trees mine C and N from mineral surfaces. They will then decrease with forest age in older forests as mining slows and C and N begin to re-accumulate. Batch experiments were conducted with mineral soil samples and dilutions of forest floor leachate. However, preliminary results from a mature forest site (about 100 years old), which we predicted to be a low point of C and N saturation from decades of mining, contradict expectations. Dissolved organic carbon (DOC) adsorption in its shallow mineral soil layers (0-3 cm below E or A horizons) are lower than younger sites ranging from 20 to about 40 years old. In addition to forest age, soil depths also affect N retention dynamics in forest soils. We hypothesized that deeper mineral soils might have greater adsorption capacities due to the fact that they are exposed to less DOC and DON leaching from organic layers and therefore less saturated. Results from the same mature forest site confirm this. Soils from 3-10 cm depth have more potential to adsorb DOC and DON than soils from 0-3 cm depth. For example, at 80 mg/L DOC, the >3-10 layer adsorbed 11.37 mg total N (TN)/g dry soil whereas the 0-3 layer adsorbed 2.13 mg TN/g dry soil. This project will also consider the effects of soil texture, soil C and N content, and Al and Fe oxide and hydroxide content.

Effects of topographic features on postfire exposed mineral soil in small watersheds

Treesearch

Mariana Dobre; Joan Q. Wu; William J. Elliot; Ina S. Miller; Theresa B. Jain

2014-01-01

Exposed mineral soil is an immediate result of forest fires with direct relevance on surface runoff and soil erosion. The goal of this study was to determine which topographic features influence the distribution of exposed mineral soil following wildfire in forested watersheds. In a field investigation 2 months after a simulated wildfire, ground cover was measured and...

Soil nitrogen mineralization in a clearcutting chronosequence in a northern California conifer forest

Treesearch

D. W. Frazier; J. G. McColl; R. F. Powers

1990-01-01

Soil ammonification, nitrification, and N mobility were studied for 1 yr in three Sierra Nevada (USA) mixed-conifer stands to examine the long-term influence of timber harvesting on soil N dynamics. Clearcutting had a persistent effect on soil N mineralization, detectable by in situ incubation but not by conventional low-tension lysimetry. Mineralization rates were...

Influence of glutamic acid enantiomers on C-mineralization.

PubMed

Formánek, Pavel; Vranová, Valerie; Lojková, Lea

2015-02-01

Seasonal dynamics in the mineralization of glutamic acid enantiomers in soils from selected ecosystems was determined and subjected to a range of treatments: ambient x elevated CO2 level and meadow x dense x thinned forest environment. Mineralization of glutamic acid was determined by incubation of the soil with 2 mg L- or D-glutamic acid g(-1) of dry soil to induce the maximum respiration rate. Mineralization of glutamic acid enantiomers in soils fluctuates over the course of a vegetation season, following a similar trend across a range of ecosystems. Mineralization is affected by environmental changes and management practices, including elevated CO2 level and thinning intensity. L-glutamic acid metabolism is more dependent on soil type as compared to metabolism of its D-enantiomer. The results support the hypothesis that the slower rate of D- compared to L- amino acid mineralization is due to different roles in anabolism and catabolism of the soil microbial community. © 2014 Wiley Periodicals, Inc.

Chemical characterization of iron-mediated soil organic matter stabilization in tropical subsoils

NASA Astrophysics Data System (ADS)

Coward, E.; Plante, A. F.; Thompson, A.

2015-12-01

Tropical forest soils contribute disproportionately to the poorly-characterized and persistent deep soil carbon (C) pool. Highly-weathered and often extending one to two meters deep, these soils also contain an abundance of semicrystalline, Fe- and Al-containing short-range-order (SRO) minerals, metastable derivatives of framework silicate and ferromagnesian parent materials. SRO minerals are capable of soil organic matter (SOM) stabilization through sorption or co-precipitation, a faculty enhanced by their high specific surface area (SSA). As such, SRO-mediated organomineral associations may prove a critical, yet matrix-selective, driver of SOM stabilization capacity in tropical soils, particularly at depth. Surface (0-20 cm) and subsoil (50-80 cm) samples were taken from 20 quantitative soil pits dug in the Luquillo Critical Zone Observatory, located in northeast Puerto Rico. Soils were stratified across granodiorite and volcaniclastic parent materials, spanning primary mineral contents of 5 to 40%. Selective dissolution procedures were used to isolate distinct forms of Fe-C interactions: (1) sodium pyrophosphate to isolate organo-mineral complexes, (2) hydroxylamine and (3) oxalate to isolate SRO phases, and (4) inorganic dithionite to isolate crystalline Fe oxides. Extracts were analysed for dissolved organic C (DOC) and Fe and Al concentrations to estimate SOM associated with each mineral phase. Soils were also subjected to SSA analysis, 57Fe-Mössbauer spectroscopy and X-ray diffraction before and after extraction to determine the contribution of extracted mineral phases to SOM stabilization capacity. Preliminary results indicate a dominance of secondary (hydr)oxides and kaolin minerals in surface soils, strongly driven by parent material. With depth, however, we observe a marked shift towards SRO mineral phases across both parent materials, suggesting that SRO-mediated organomineral associations are significant contributors to observed C storage in tropical subsoils.

Calcic soils and calcretes in the southwestern United States

USGS Publications Warehouse

Bachman, George Odell; Machette, Michael N.

1977-01-01

Secondary calcium carbonate of diverse origins, 'caliche' of many authors, is widespread in the southwestern United States. 'Caliche' includes various carbonates such as calcic soils and products of groundwater cementation. The term 'caliche' is generally avoided in this report in favor of such terms as calcrete, calcic soils, and pervasively cemented deposits. Criteria for the recognition of various types of calcrete of diverse origins include field relations and laboratory data. Calcic soils provide a comprehensive set of characteristics that aid in their recognition in the field. These characteristics include a distinctive morphology that is zoned horizontally and can frequently be traced over tens to hundreds of square kilometers. The major process in the formation of pedogenic calcrete and calic soils is the leaching of calcium carbonate from upper soil horizons by downward percolating soil solutions and reprecipitation of the carbonate in alluvial horizons near the base of the soil profile. The formation of pedogenic calcrete involves many factors including climate, source of carbonate, and tectonic stability of the geomorphic surface on which the calcrete is deposited. Most of the carbonate in pedogenic calcrete is probably derived from windblown sand, dust, and rain. Calcic soils and pedogenic calcretes follow a six-stage sequence morphologic development and is based on a classification devised by Gile, Peterson and Grossman in 1966. The .six morphologic stages of carbonate deposition in soils are related to the relative age of the soil and are as follows: I. The first or youngest stage includes filamentous or faint coatings of carbonate on detrital grains. II. The second stage includes pebble coatings which are continuous; firm carbonate nodules are few to common. III. The third stage includes coalesced nodules which occur in a friable or disseminated carbonate matrix. IV. The fourth stage includes platy, firmly cemented matrix which engulfs nodules; horizon is plugged to downward moving solutions. V. The fifth stage includes soils which are platy to tabular, dense, strongly cemented. A well-developed laminar layer occurs on the upper surface. VI. The sixth and most advanced stage is massive, multilaminar, and strongly cemented calcrete with abundant pisoliths, the upper surface of which may be brecciated. Pisoliths may indicate many generations of brecciation and reformation. In general calcic soils include stages I through III and are friable to moderately indurated; whereas pedogenic calcretes include stages IV through VI and are dense and strongly indurated. In a single pedon the morphologic stage of carbonate deposition decreases downward in the profile. The stage of development may be used in local regions for correlation and determination of relative ages of soils and geomorphic surfaces. Some structures observed in pedogenic calcretes may be present in other types of calcrete but the horizontal zonation typical of deposits of soil processes is absent. Laminar structure in particular is not restricted to pedogenic deposits and is common in many varieties of calcrete. Very little chemical change occurs in the noncalcareous nonclayey fractions of calcretes with age; but clay minerals within calcretes undergo a complex history of authigenesis. There is a depletion of magnesium in the calcareous portion and an enrichment of magnesium in the clayey portion of a calcrete with age. In keeping with this relationship, montmorillonite, or mixed layer montmorillonite-illite, is common in younger calcretes; whereas the high magnesium-silicate clays, sepiolite and palygorskite, are common in older calcretes. This indicates that the magnesium depleted from the carbonate is redistributed authigenically in clay minerals. The mobility of carbonate introduces many problems in attempts to date calcretes directly. Although the relative ages of soils within a province may be determined by quant

Zinc oxide nanoparticles affect carbon and nitrogen mineralization of Phoenix dactylifera leaf litter in a sandy soil.

PubMed

Rashid, Muhammad Imtiaz; Shahzad, Tanvir; Shahid, Muhammad; Ismail, Iqbal M I; Shah, Ghulam Mustafa; Almeelbi, Talal

2017-02-15

We investigated the impact of zinc oxide nanoparticles (ZnO NPs; 1000mgkg -1 soil) on soil microbes and their associated soil functions such as date palm (Phoenix dactylifera) leaf litter (5gkg -1 soil) carbon and nitrogen mineralization in mesocosms containing sandy soil. Nanoparticles application in litter-amended soil significantly decreased the cultivable heterotrophic bacterial and fungal colony forming units (cfu) compared to only litter-amended soil. The decrease in cfu could be related to lower microbial biomass carbon in nanoparticles-litter amended soil. Likewise, ZnO NPs also reduced CO 2 emission by 10% in aforementioned treatment but this was higher than control (soil only). Labile Zn was only detected in the microbial biomass of nanoparticles-litter applied soil indicating that microorganisms consumed this element from freely available nutrients in the soil. In this treatment, dissolved organic carbon and mineral nitrogen were 25 and 34% lower respectively compared to litter-amended soil. Such toxic effects of nanoparticles on litter decomposition resulted in 130 and 122% lower carbon and nitrogen mineralization efficiency respectively. Hence, our results entail that ZnO NPs are toxic to soil microbes and affect their function i.e., carbon and nitrogen mineralization of applied litter thus confirming their toxicity to microbial associated soil functions. Copyright © 2016 Elsevier B.V. All rights reserved.

Short-term responses of soil nitrogen mineralization, nitrification and denitrification to prescribed burning in a suburban forest ecosystem of subtropical Australia.

PubMed

Zhang, Manyun; Wang, Weijin; Wang, Dianjie; Heenan, Marijke; Xu, Zhihong

2018-06-17

As an anthropogenic disturbance, prescribed burning may alter the biogeochemistries of nutrients, including nitrogen (N) cycling, in forest ecosystems. This study aimed to examine the changes in N mineralization, nitrification and denitrification rates following prescribed burning in a suburban forest located in subtropical Australia and assess the interactive relationships among soil properties, functional gene abundances and N transformation rates. After a prescribed burning event, soil pH value increased, but soil labile carbon and mineral N contents decreased. Net N mineralization rates, potential nitrification rates and ammonium-oxidizing archaea and bacteria (AOA and AOB) amoA gene abundances in the soils all increased after 3 months of the prescribed burning. However, the abundances of different functional genes related to denitrification changed differently after the prescribed burning. The net N mineralization rates could be best described by soil abiotic properties, rather than functional gene abundances. In contrast, potential denitrification rates were positively related to soil nirK gene abundances. Potential nitrification rates could be influenced by both soil chemical and microbial properties. The results revealed that the prescribed burning might increase N mineralization and nitrification rates in the forest soil. Copyright © 2018 Elsevier B.V. All rights reserved.

Enhanced degradation of isoproturon in an agricultural soil by a Sphingomonas sp. strain and a microbial consortium.

PubMed

Li, Renyi; Dörfler, Ulrike; Munch, Jean Charles; Schroll, Reiner

2017-02-01

Isoproturon (IPU) degradation in an agricultural soil inoculated with an isolated IPU-degrader strain (Sphingomonas sp. strain AK1, IS) or a microbial consortium (MC) harboring this strain, with or without carrier material, were investigated in soil microcosm experiments during 46 days. Effect of the carrier material and inoculation size on IPU-degradation efficacy of the inoculants were studied. Mineralization, extractable residues and non-extractable residues of 14 C-labeled IPU were analyzed. The low IPU mineralization in untreated soil (7.0%) was enhanced to different extents by inoculation of IS (17.4%-46.0%) or MC (58.9%-67.5%). Concentrations of IPU residues in soils amended with MC (0.002-0.095 μg g dry soil -1 ) were significantly lower than in soils amended with IS (0.02-0.67 μg g dry soil -1 ) and approximately 10 times lower than in the uninoculated soil (0.06-0.80 μg g dry soil -1 ). Less extractable residues and non-extractable residues were detected in soil with higher IPU mineralization. Inoculation size (as indicated by the volume of liquid cultures or by the number of carrier particles) determined the IPU-removal efficacy of IS in soil, but this effect was less pronounced for MC. The low sorption of IPU to soil and the decreasing IPU-mineralizing rates suggested incapability of IS to establish the IPU-mineralizing function in the soil. The thorough removal of IPU and persistent IPU-mineralizing activity of soil inoculated with MC indicated a high persistence of IPU-metabolic trait. Our results showed that microbial consortia might be more efficient than single degrader strains to enhance clean-up of organic chemicals in soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Chemistry, mineralogy and origin of the clay-hill nitrate deposits, Amargosa River valley, Death Valley region, California, U.S.A.

USGS Publications Warehouse

Ericksen, G.E.; Hosterman, J.W.; St., Amand

1988-01-01

The clay-hill nitrate deposits of the Amargosa River valley, California, are caliche-type accumulations of water-soluble saline minerals in clay-rich soils on saline lake beds of Miocene, Pliocene(?) and Pleistocene age. The soils have a maximum thickness of ??? 50 cm, and commonly consist of three layers: (1) an upper 5-10 cm of saline-free soil; (2) an underlying 15-20 cm of rubbly saline soil; and (3) a hard nitrate-rich caliche, 10-20 cm thick, at the bottom of the soil profile. The saline constituents, which make up as much as 50% of the caliche, are chiefly Cl-, NO-3, SO2-4 and Na+. In addition are minor amounts of K+, Mg2+ and Ca2+, varying, though generally minor, amounts of B2O3 and CO2-3, and trace amounts of I (probably as IO-3), NO-2, CrO2-4 and Mo (probably as MoO2-4). The water-soluble saline materials have an I/Br ratio of ??? 1, which is much higher than nearly all other saline depostis. The principal saline minerals of the caliche are halite (NaCl), nitratite (NaNO3), darapskite (Na3(SO4)(NO3)??H2O), glauberite (Na2Ca(SO4)2), gypsum (CaSO4??2H2O) and anhydrite (CaSO4). Borax (Na2B4O5(OH)4??8H2O), tincalconite (Na2B4O5(OH)4??3H2O) and trona (Na3(CO3)(HCO3)??2H2O) are abundant locally. The clay-hill nitrate deposits are analogous to the well-known Chilean nitrate deposits, and probably are of similar origin. Whereas the Chilean deposits are in permeable soils of the nearly rainless Atacama Desert, the clay-hill deposits are in relatively impervious clay-rich soils that inhibited leaching by rain water. The annual rainfall in the Death Valley region of ??? 5 cm is sufficient to leach water-soluble minerals from the more permeable soils. The clay-hill deposits contain saline materials from the lake beds beneath the nitrate deposits are well as wind-transported materials from nearby clay-hill soils, playas and salt marshes. The nitrate is probably of organic origin, consisting of atmospheric nitrogen fixed as protein by photoautotrophic blue-green algae, which are thought to form crusts on soils at the sites of the deposits when moistened by rainfall. The protein is subsequently transformed to nitrate by autotophic bacteria. ?? 1988.

Laboratory and greenhouse assessment of phytoremediation of petroleum contaminated soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banks, M.K.; Schwab, A.P.; Wang, X.

Phytoremediation of soils contaminated with petroleum and associated priority pollutants was evaluated in greenhouse and laboratory experiments. Mineralization of several PAHs was measured in rhizosphere soil, non-rhizosphere soil, and sterile soil amended with simulated root exudates. The least amount of mineralization was observed in sterile soil, but there were no differences among all other soils. Mineralization of 14 C-benzo[a]pyrene was determined in chambers to determine the effects of tall fescue on dissipation of this compound. After 180 days, the soils with fescue had more than twice the mineralization than soils without plants. In the soils with plants, evolution of 14CO2more » from the soil was five times greater than from the plant biomass. These experiments demonstrate that the presence of plants is a necessary part of the phytoremediation process. There appears to be no residual rhizosphere effect, and the simple exudation of organic compounds does not mimic fully the presence of roots.« less

Net nitrogen mineralization and net nitrification rates in soils following deforestation for pasture across the southwestern Brazilian Amazon Basin landscape.

PubMed

Neill, Christopher; Piccolo, Marisa C; Cerri, Carlos C; Steudler, Paul A; Melillo, Jerry M; Brito, Marciano

1997-04-01

Previous studies of the effect of tropical forest conversion to cattle pasture on soil N dynamics showed that rates of net N mineralization and net nitrification were lower in pastures compared with the original forest. In this study, we sought to determine the generality of these patterns by examining soil inorganic N concentrations, net mineralization and nitrification rates in 6 forests and 11 pastures 3 years old or older on ultisols and oxisols that encompassed a wide variety of soil textures and spanned a 700-km geographical range in the southwestern Brazilian Amazon Basin state of Rondônia. We sampled each site during October-November and April-May. Forest soils had higher extractable NO 3 - -N and total inorganic N concentrations than pasture soils, but substantial NO 3 - -N occurred in both forest and pasture soils. Rates of net N mineralization and net nitrification were higher in forest soils. Greater concentrations of soil organic matter in finer textured soils were associated with greater rates of net N mineralization and net nitrification, but this relationship was true only under native forest vegetation; rates were uniformly low in pastures, regardless of soil type or texture. Net N mineralization and net nitrification rates per unit of total soil organic matter showed no pattern across the different forest sites, suggesting that controls of net N mineralization may be broadly similar across a wide range of soil types. Similar reductions in rates of net N transformations in pastures 3 years old or older across a range of textures on these soils suggest that changes to soil N cycling caused by deforestation for pasture may be Basin-wide in extent. Lower net N mineralization and net nitrification rates in established pastures suggest that annual N losses from largely deforested landscapes may be lower than losses from the original forest. Total ecosystem N losses since deforestation are likely to depend on the balance between lower N loss rates from established pastures and the magnitude and duration of N losses that occur in the years immediately following forest clearing.

Impact of exotic earthworms on organic carbon sorption on mineral surfaces and soil carbon inventories in a northern hardwood forest

Treesearch

Amy Lyttle; Kyungsoo Yoo; Cindy Hale; Anthony Aufdenkampe; Stephen D. Sebestyen; Kathryn Resner; Alex Blum

2015-01-01

Exotic earthworms are invading forests in North America where native earthworms have been absent since the last glaciation. These earthworms bioturbate soils and may enhance physical interactions between minerals and organic matter (OM), thus affecting mineral sorption of carbon (C) which may affect C cycling. We quantitatively show how OM-mineral sorption and soil C...

Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

NASA Astrophysics Data System (ADS)

Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

2015-04-01

Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

30 CFR 823.14 - Soil replacement.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Soil replacement. 823.14 Section 823.14 Mineral... Soil replacement. (a) Soil reconstruction specifications established by the U.S. Soil Conservation Service shall be based upon the standards of the National Cooperative Soil Survey and shall include, as a...

30 CFR 823.14 - Soil replacement.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Soil replacement. 823.14 Section 823.14 Mineral... Soil replacement. (a) Soil reconstruction specifications established by the U.S. Soil Conservation Service shall be based upon the standards of the National Cooperative Soil Survey and shall include, as a...

30 CFR 823.14 - Soil replacement.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Soil replacement. 823.14 Section 823.14 Mineral... Soil replacement. (a) Soil reconstruction specifications established by the U.S. Soil Conservation Service shall be based upon the standards of the National Cooperative Soil Survey and shall include, as a...

30 CFR 823.14 - Soil replacement.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Soil replacement. 823.14 Section 823.14 Mineral... Soil replacement. (a) Soil reconstruction specifications established by the U.S. Soil Conservation Service shall be based upon the standards of the National Cooperative Soil Survey and shall include, as a...

30 CFR 823.14 - Soil replacement.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Soil replacement. 823.14 Section 823.14 Mineral... Soil replacement. (a) Soil reconstruction specifications established by the U.S. Soil Conservation Service shall be based upon the standards of the National Cooperative Soil Survey and shall include, as a...

Effects of biochar and the geophagous earthworm Metaphire guillelmi on fate of (14)C-catechol in an agricultural soil.

PubMed

Shan, Jun; Wang, Yongfeng; Gu, Jianqiang; Zhou, Wenqiang; Ji, Rong; Yan, Xiaoyuan

2014-07-01

Both biochar and earthworms can exert influence on behaviors of soil-borne monomeric phenols in soil; however, little was known about the combined effects of biochar and earthworm activities on fate of these chemicals in soil. Using (14)C-catechol as a representative, the mineralization, transformation and residue distribution of phenolic humus monomer in soil amended with different amounts of biochar (0%, 0.05%, 0.5%, and 5%) without/with the geophagous earthworm Metaphire guillelmi were investigated. The results showed biochar at amendment rate <0.5% did not affect (14)C-catechol mineralization, whereas 5% biochar amendment significantly inhibited the mineralization. Earthworms did not affect the mineralization of (14)C-catechol in soil amended with <0.5% biochar, but significantly enhanced the mineralization in 5% biochar amended soil when they were present in soil for 9 d. When earthworms were removed from the soil, the mineralization of (14)C-catechol was significantly lower than that of in earthworm-free soil indicating that (14)C-catecholic residues were stabilized during their passage through earthworm gut. The assimilation of (14)C by earthworms was low (1.2%), and was significantly enhanced by biochar amendment, which was attributed to the release of biochar-associated (14)C-catecholic residues during gut passage of earthworm. Copyright © 2014 Elsevier Ltd. All rights reserved.

Spatial variability of isoproturon mineralizing activity within an agricultural field: geostatistical analysis of simple physicochemical and microbiological soil parameters.

PubMed

El Sebai, T; Lagacherie, B; Soulas, G; Martin-Laurent, F

2007-02-01

We assessed the spatial variability of isoproturon mineralization in relation to that of physicochemical and biological parameters in fifty soil samples regularly collected along a sampling grid delimited across a 0.36 ha field plot (40 x 90 m). Only faint relationships were observed between isoproturon mineralization and the soil pH, microbial C biomass, and organic nitrogen. Considerable spatial variability was observed for six of the nine parameters tested (isoproturon mineralization rates, organic nitrogen, genetic structure of the microbial communities, soil pH, microbial biomass and equivalent humidity). The map of isoproturon mineralization rates distribution was similar to that of soil pH, microbial biomass, and organic nitrogen but different from those of structure of the microbial communities and equivalent humidity. Geostatistics revealed that the spatial heterogeneity in the rate of degradation of isoproturon corresponded to that of soil pH and microbial biomass.

Sand and clay mineralogy of sal forest soils of the Doon Siwalik Himalayas

NASA Astrophysics Data System (ADS)

Mukesh; Manhas, R. K.; Tripathi, A. K.; Raina, A. K.; Gupta, M. K.; Kamboj, S. K.

2011-02-01

The peteromineralogical characterization of the soil was carried out for the 12 soil profiles exposed in the Shorea robusta dominated forests of the Siwalik forest division, Dehradun. The quartz was observed as the dominating light mineral fraction (64-80%) in all the profiles studied. Biotite, hornblende, zircon, tourmaline, rutile and opaques comprising of iron minerals constituted the heavy mineral fraction (20%). The mineralogy of both the sand and clay fractions revealed a mixed mineralogy. The clay minerals in the order of their dominance were vermiculite, illite, kaolinite and mixed layer minerals. The presence of vermiculite and illite in appreciable quantities indicates that these were synthesized from the K-rich soil solution, as orthoclase and micas were present in significant quantities in the sand minerals. The mineral suites identified in the study shows that the geological, climatological and topographical factors of the region collectively played a dominant role in their formation and transformation. After critical appraisal of the results, it may be deduced that the mineralogical composition, physicochemical properties and total elemental analysis of the soils do not show any deficiency of the bases and other plant nutrients in general. The inherent fertility of the soil is good as indicated by the sand and clay mineralogy of the soil and the biotite and feldspar together with the mica is an important source of nutrients for the vegetation in the soils of the Doon valley.

Agricultural management and labile carbon additions affect soil microbial community structure and interact with carbon and nitrogen cycling.

PubMed

Berthrong, Sean T; Buckley, Daniel H; Drinkwater, Laurie E

2013-07-01

We investigated how conversion from conventional agriculture to organic management affected the structure and biogeochemical function of soil microbial communities. We hypothesized the following. (1) Changing agricultural management practices will alter soil microbial community structure driven by increasing microbial diversity in organic management. (2) Organically managed soil microbial communities will mineralize more N and will also mineralize more N in response to substrate addition than conventionally managed soil communities. (3) Microbial communities under organic management will be more efficient and respire less added C. Soils from organically and conventionally managed agroecosystems were incubated with and without glucose ((13)C) additions at constant soil moisture. We extracted soil genomic DNA before and after incubation for TRFLP community fingerprinting of soil bacteria and fungi. We measured soil C and N pools before and after incubation, and we tracked total C respired and N mineralized at several points during the incubation. Twenty years of organic management altered soil bacterial and fungal community structure compared to continuous conventional management with the bacterial differences caused primarily by a large increase in diversity. Organically managed soils mineralized twice as much NO3 (-) as conventionally managed ones (44 vs. 23 μg N/g soil, respectively) and increased mineralization when labile C was added. There was no difference in respiration, but organically managed soils had larger pools of C suggesting greater efficiency in terms of respiration per unit soil C. These results indicate that the organic management induced a change in community composition resulting in a more diverse community with enhanced activity towards labile substrates and greater capacity to mineralize N.

Persulfate activation by subsurface minerals.

PubMed

Ahmad, Mushtaque; Teel, Amy L; Watts, Richard J

2010-06-25

Persulfate dynamics in the presence of subsurface minerals was investigated as a basis for understanding persulfate activation for in situ chemical oxidation (ISCO). The mineral-mediated decomposition of persulfate and generation of oxidants and reductants was investigated with four iron and manganese oxides and two clay minerals at both low pH (<7) and high pH (>12). The manganese oxide birnessite was the most effective initiator of persulfate for degrading the oxidant probe nitrobenzene, indicating that oxidants are generated at both low and high pH regimes. The iron oxide goethite was the most effective mineral for degrading the reductant probe hexachloroethane. A natural soil and two soil fractions were used to confirm persulfate activation by synthetic minerals. The soil and soil fractions did not effectively promote the generation of oxidants or reductants. However, soil organic matter was found to promote reductant generation at high pH. The results of this research demonstrate that synthetic iron and manganese oxides can activate persulfate to generate reductants and oxidants; however, iron and manganese oxides in the natural soil studied do not show the same reactivity, most likely due to the lower masses of the metal oxides in the soil relative to the masses studied in isolated mineral systems. 2010. Published by Elsevier B.V.

Probing the rhizosphere to define mineral organic relationships

NASA Astrophysics Data System (ADS)

Schulz, M. S.; Dohnalkova, A.; Stonestrom, D. A.

2016-12-01

Soil organic matter (SOM) accumulation and stabilization over time is an important process as soils are a large carbon reservoir in which feedbacks under changing climates are unclear. The association of SOM with poorly crystalline or short-range-ordered secondary minerals has been shown to be important for carbon stabilization. Commonly used soil extraction techniques display correlations of SOM with secondary phases but do not show causation. The fate of root exudates in soils and processes controlling exudate associations with mineral phases are as yet structurally undefined. Sub-micron exploration of in-situ relations provides valuable information on SOM-mineral interactions. Soils of the Santa Cruz (California) marine terrace chronosequence are used to illustrate changes in deep (> 1 m) rhizosphere through time. Cracks and soil ped faces are sites of high root density and organic matter (biofilm or mucilage) deposition. We employ a variety of scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) techniques for high resolution imaging and elemental analyses of deep rhizosphere and associated carbon mineral interactions. In these coastal prairie soils microscopy reveals secondary clay minerals associated with and possibly forming from organic-rich mucilage that occurs along the aforementioned rooting networks on fracture surfaces. We hypothesize that the production of secondary clays in the rhizosphere is an important mode of C incorporation into secondary minerals.

Mercury contamination in agricultural soils from abandoned metal mines classified by geology and mineralization.

PubMed

Kim, Han Sik; Jung, Myung Chae

2012-01-01

This survey aimed to compare mercury concentrations in soils related to geology and mineralization types of mines. A total of 16,386 surface soils (0~15 cm in depth) were taken from agricultural lands near 343 abandoned mines (within 2 km from each mine) and analyzed for Hg by AAS with a hydride-generation device. To meaningfully compare mercury levels in soils with geology and mineralization types, three subclassification criteria were adapted: (1) five mineralization types, (2) four valuable ore mineral types, and (3) four parent rock types. The average concentration of Hg in all soils was 0.204 mg kg(-1) with a range of 0.002-24.07 mg kg(-1). Based on the mineralization types, average Hg concentrations (mg kg(-1)) in the soils decreased in the order of pegmatite (0.250) > hydrothermal vein (0.208) > hydrothermal replacement (0.166) > skarn (0.121) > sedimentary deposits (0.045). In terms of the valuable ore mineral types, the concentrations decreased in the order of Au-Ag-base metal mines ≈ base metal mines > Au-Ag mines > Sn-W-Mo-Fe-Mn mines. For parent rock types, similar concentrations were found in the soils derived from sedimentary rocks and metamorphic rocks followed by heterogeneous rocks with igneous and metamorphic processes. Furthermore, farmland soils contained relatively higher Hg levels than paddy soils. Therefore, it can be concluded that soils in Au, Ag, and base metal mines derived from a hydrothermal vein type of metamorphic rocks and pegmatite deposits contained relatively higher concentrations of mercury in the surface environment.

Predicting the Mineral Composition of Dust Aerosols. Part 2; Model Evaluation and Identification of Key Processes with Observations

NASA Technical Reports Server (NTRS)

Perlwitz, J. P.; Garcia-Pando, C. Perez; Miller, R. L.

2015-01-01

A global compilation of nearly sixty measurement studies is used to evaluate two methods of simulating the mineral composition of dust aerosols in an Earth system model. Both methods are based upon a Mean Mineralogical Table (MMT) that relates the soil mineral fractions to a global atlas of arid soil type. The Soil Mineral Fraction (SMF) method assumes that the aerosol mineral fractions match the fractions of the soil. The MMT is based upon soil measurements after wet sieving, a process that destroys aggregates of soil particles that would have been emitted from the original, undisturbed soil. The second method approximately reconstructs the emitted aggregates. This model is referred to as the Aerosol Mineral Fraction (AMF) method because the mineral fractions of the aerosols differ from those of the wet-sieved parent soil, partly due to reaggregation. The AMF method remedies some of the deficiencies of the SMF method in comparison to observations. Only the AMF method exhibits phyllosilicate mass at silt sizes, where they are abundant according to observations. In addition, the AMF quartz fraction of silt particles is in better agreement with measured values, in contrast to the overestimated SMF fraction. Measurements at distinct clay and silt particle sizes are shown to be more useful for evaluation of the models, in contrast to the sum over all particles sizes that is susceptible to compensating errors, as illustrated by the SMF experiment. Model errors suggest that allocation of the emitted silt fraction of each mineral into the corresponding transported size categories is an important remaining source of uncertainty. Evaluation of both models and the MMT is hindered by the limited number of size-resolved measurements of mineral content that sparsely sample aerosols from the major dust sources. The importance of climate processes dependent upon aerosol mineral composition shows the need for global and routine mineral measurements.

Predicting the mineral composition of dust aerosols – Part 2: Model evaluation and identification of key processes with observations

DOE PAGES

Perlwitz, J. P.; Perez Garcia-Pando, C.; Miller, R. L.

2015-10-21

A global compilation of nearly sixty measurement studies is used to evaluate two methods of simulating the mineral composition of dust aerosols in an Earth system model. Both methods are based upon a Mean Mineralogical Table (MMT) that relates the soil mineral fractions to a global atlas of arid soil type. The Soil Mineral Fraction (SMF) method assumes that the aerosol mineral fractions match the fractions of the soil. The MMT is based upon soil measurements after wet sieving, a process that destroys aggregates of soil particles that would have been emitted from the original, undisturbed soil. The second methodmore » approximately reconstructs the emitted aggregates. This model is referred to as the Aerosol Mineral Fraction (AMF) method because the mineral fractions of the aerosols differ from those of the wet-sieved parent soil, partly due to reaggregation. The AMF method remedies some of the deficiencies of the SMF method in comparison to observations. Only the AMF method exhibits phyllosilicate mass at silt sizes, where they are abundant according to observations. In addition, the AMF quartz fraction of silt particles is in better agreement with measured values, in contrast to the overestimated SMF fraction. Measurements at distinct clay and silt particle sizes are shown to be more useful for evaluation of the models, in contrast to the sum over all particles sizes that is susceptible to compensating errors, as illustrated by the SMF experiment. Model errors suggest that allocation of the emitted silt fraction of each mineral into the corresponding transported size categories is an important remaining source of uncertainty. Evaluation of both models and the MMT is hindered by the limited number of size-resolved measurements of mineral content that sparsely sample aerosols from the major dust sources. In conclusion, the importance of climate processes dependent upon aerosol mineral composition shows the need for global and routine mineral measurements.« less

Soil mineral assemblage influences on microbial communities and carbon cycling under fresh organic matter input

NASA Astrophysics Data System (ADS)

Finley, B. K.; Schwartz, E.; Koch, B.; Dijkstra, P.; Hungate, B. A.

2017-12-01

The interactions between soil mineral assemblages and microbial communities are important drivers of soil organic carbon (SOC) cycling and storage, although the mechanisms driving these interactions remain unclear. There is increasing evidence supporting the importance of associations with poorly crystalline, short-range order (SRO) minerals in protection of SOC from microbial utilization. However, how the microbial processing of SRO-associated SOC may be influenced by fresh organic matter inputs (priming) remains poorly understood. The influence on SRO minerals on soil microbial community dynamics is uncertain as well. Therefore, we conducted a priming incubation by adding either a simulated root exudate mixture or conifer needle litter to three soils from a mixed-conifer ecosystem. The parent material of the soils were andesite, basalt, and granite and decreased in SRO mineral content, respectively. We also conducted a parallel quantitative stable isotope probing incubation by adding 18O-labelled water to the soils to isotopically label microbial DNA in situ. This allowed us to characterize and identify the active bacterial and archaeal community and taxon-specific growth under fresh organic matter input. While the granite soil (lowest SRO content), had the largest total mineralization, the least priming occurred. The andesite and basalt soils (greater SRO content) had lower total respiration, but greater priming. Across all treatments, the granite soil, while having the lowest species richness of the entire community (249 taxa, both active and inactive), had a larger active community (90%) in response to new SOC input. The andesite and basalt soils, while having greater total species richness of the entire community at 333 and 325 taxa, respectively, had fewer active taxa in response to new C compared to the granite soil (30% and 49% taxa, respectively). These findings suggest that the soil mineral assemblage is an important driver on SOC cycling under fresh organic matter inputs, as well as on the activity and diversity of the microbial community. Often, microbial diversity is associated with function. Our results suggest that the soil environment, in this case SRO mineral content, may be more important on SOC cycling and storage than microbial diversity alone.

Natural attenuation is enhanced in previously contaminated and coniferous forest soils.

PubMed

Kauppi, Sari; Romantschuk, Martin; Strömmer, Rauni; Sinkkonen, Aki

2012-01-01

Prevalence of organic pollutants or their natural analogs in soil is often assumed to lead to adaptation in the bacterial community, which results in enhanced bioremediation if the soil is later contaminated. In this study, the effects of soil type and contamination history on diesel oil degradation and bacterial adaptation were studied. Mesocosms of mineral and organic forest soil (humus) were artificially treated with diesel oil, and oil hydrocarbon concentrations (GC-FID), bacterial community composition (denaturing gradient gel electrophoresis, DGGE), and oil hydrocarbon degraders (DGGE + sequencing of 16S rRNA genes) were monitored for 20 weeks at 16°C. Degradation was advanced in previously contaminated soils as compared with pristine soils and in coniferous organic forest soil as compared with mineral soil. Contamination affected bacterial community composition especially in the pristine mineral soil, where diesel addition increased the number of strong bands in the DGGE gel. Sequencing of cloned 16S rRNA gene fragments and DGGE bands showed that potential oil-degrading bacteria were found in mineral and organic soils and in both pristine and previously contaminated mesocosms. Fast oil degradation was not associated with the presence of any particular bacterial strain in soil. We demonstrate at the mesocosm scale that previously contaminated and coniferous organic soils are superior environments for fast oil degradation as compared with pristine and mineral soil environments. These results may be utilized in preventing soil pollution and planning soil remediation.

Microbes Persist: Using a Systems Biology Approach to Reveal How the Soil Microbiome Shapes Soil Organic Matter

NASA Astrophysics Data System (ADS)

Pett-Ridge, J.

2017-12-01

Soils store more carbon than the atmosphere and terrestrial vegetation combined, yet the factors that control its persistence remain elusive. Recent insights have overturned the long-held assumption that carbon stability depends mostly on chemical `recalcitrance' of soil organic matter (SOM). Instead, an emerging paradigm emphasizes how environmental drivers like temperature and moisture, soil minerals, and microbial ecology interact to control SOM formation, stabilization, and turnover. Detailed spectroscopic and isotopic (14C) analyses of mineral-associated SOM show that the oldest carbon in soil may be easily broken down and respired in the laboratory, and that it biochemically resembles microbial cells and metabolites far more than plant material. This places microbial ecophysiology at the center of the soil carbon persistence question. Microbial cells likely interact with mineral surfaces as part of an ecological strategy to condition their environment (e.g. biofilm formation or extracellular enzyme production), and their diverse cellular components likely associate with minerals after cells die. Collectively, these microbial characteristics - metabolic activities, population growth strategies, and cellular biochemistry - can be thought of as `soil ecophysiological traits'. This presentation will explore potential traits that may be fruitful targets for studies evaluating the persistence and importance of microbial products as SOM precursors, and will highlight results showing that soil mineral type influences the microbial communities that colonize mineral surfaces, as well as the quantity and type of mineral-associated carbon that accumulates. I will propose a series of integrated approaches that used together can examine how genomic capacity and activities of soil microbiomes are shaped by edaphic conditions (moisture, temperature, redox regimes) and fundamentally affect the terrestrial soil C pool.

Redox Fluctuations Increase the Contribution of Lignin to Soil Respiration

NASA Astrophysics Data System (ADS)

Hall, S. J.; Silver, W. L.; Timokhin, V.; Hammel, K.

2014-12-01

Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia has long been thought to suppress lignin decomposition, yet variation in oxygen (O2) availability in surface soils accompanying moisture fluctuations could potentially stimulate this process by generating reactive oxygen species via coupled biotic and abiotic iron (Fe) redox cycling. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl and propyl Cβ) to provide highly sensitive and specific measures of lignin mineralization not previously employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration, and cumulative methoxyl C mineralization was equivalent under static aerobic and fluctuating redox conditions despite lower total C mineralization in the latter treatment. Contributions of the highly stable Cβ to mineralization were also equivalent in static aerobic and fluctuating redox treatments during periods of O2 exposure, and nearly doubled in the fluctuating treatment after normalizing to cumulative O2 exposure. Oxygen fluctuations drove substantial net Fe reduction and oxidation, implying that reactive oxygen species generated during abiotic Fe oxidation likely contributed to the elevated contribution of lignin to C mineralization. Iron redox cycling provides a mechanism for lignin breakdown in soils that experience conditions unfavorable for canonical lignin-degrading organisms, and provides a potential mechanism for lignin depletion in soil organic matter during late-stage decomposition. Thus, close couplings between soil moisture, redox fluctuations, and lignin breakdown provide potential a link between climate variability and the biochemical composition of soil organic matter with important implications for soil C budgets.

Soil gas studies along the Trans-Challis fault system near Idaho City, Boise County, Idaho

USGS Publications Warehouse

McCarthy, J.H.; Kiilsgaard, T.H.

2001-01-01

Soil gases were sampled along several traverses that cross the Trans-Challis fault system in central Idaho. Anomalous carbon dioxide, hydrogen, oxygen, hydrocarbon, and sulfur gas concentrations coincide with faults and known mineralized areas. Anomalies in areas not known to be mineralized may reflect undiscovered mineral deposits or concealed faults. Soil gases may be a useful exploration guide for mineral deposits in this terrane.

Microbial biomass and basal respiration of selected Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

NASA Astrophysics Data System (ADS)

Abakumov, E.; Mukhametova, N.

2014-07-01

Antarctica is a unique place for soil, biological, and ecological investigations. Soils of Antarctica have been studied intensively during the last century, when different national Antarctic expeditions visited the sixth continent with the aim of investigating nature and the environment. Antarctic investigations are comprised of field surveys mainly in the terrestrial landscapes, where the polar stations of different countries are situated. That is why the main and most detailed soil surveys were conducted in the McMurdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann Hills and the Schirmacher Oasis. Our investigations were conducted during the 53rd and 55th Russian Antarctic expeditions in the base of soil pits, and samples were collected in Sub-Antarctic and Antarctic regions. Sub-Antarctic or maritime landscapes are considered to be very different from Antarctic landscapes due to differing climatic and geogenic conditions. Soils of diverse zonal landscapes were studied with the aim of assessing the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. This investigation shows that Antarctic soils are quite diverse in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as by an upper organic layer. The most developed organic layers were revealed in peat soils of King George Island, where its thickness reach, in some cases, was 80 cm. These soils as well as soils formed under guano are characterized by the highest amount of total organic carbon (TOC), between 7.22 and 33.70%. Coastal and continental Antarctic soils exhibit less developed Leptosols, Gleysols, Regolith and rare Ornhitosol, with TOC levels between 0.37 and 4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones, which can be interpreted as a result of higher amounts of fresh organic remnants in organic and organo-mineral horizons. The soils of King George Island also have higher portions of microbial biomass (max 1.54 mg g-1) compared to coastal (max 0.26 mg g-1) and continental (max 0.22 mg g-1) Antarctic soils. Sub-Antarctic soils differ from Antarctic ones mainly by having increased organic layer thickness and total organic carbon content, higher microbial biomass carbon content, basal respiration, and metabolic activity levels.

Thresholds in Soil Mineral Weathering and Relation to Streamwater Chemistry in Glaciated Catchments of the Northeastern USA

NASA Astrophysics Data System (ADS)

Bailey, S. W.; Ross, D. S.

2015-12-01

Primary mineral dissolution (i.e. weathering) is a critical process in forested catchments as an important consumer of acidity and CO2, the principle source of nutrients such as Ca, K, and P, as well as the source of toxic cations such as Al. Two common limitations of weathering studies are inadequate determination of mineralogic composition and insufficient sampling depth to determine location and advancement of weathering reactions. We determined mineral stocks through EPMA mapping of Al, Ca, Fe, P, and Si content of soil samples and development of an image analysis routine that assigned mineral composition based on the content of these five elements. Portions of the classified maps were confirmed by optical petrography and full elemental analysis by SEM-EDS. Samples were analyzed for soil profiles >2m depth (~1.5m past the upper boundary of the "unweathered" C horizon). Study sites spanned a range of weatherability found in catchments in glaciated northeastern USA including Winnisook, NY (sandstone parent material, 100 ppm Ca), Hubbard Brook, NH (granite, 0.9% Ca), and Sleepers River, VT (calcareous granulite, 3.5% Ca). All profiles exhibited a weathering front, or threshold above which the most reactive minerals (calcite, apatite) have been depleted. However, in all cases this threshold was below the rooting zone, and in many profiles, it was well below the C horizon interface. Catchment scale Ca exports reflect this deeper weathering source while rooting zone exchangeable Ca was highly variable, probably reflecting spatial patterns of hydrologic flowpaths which bring deeper weathering products to the surface only in certain landscape positions. These results suggest that nutrient cycling and critical loads models, which assume that ecologically relevant weathering is confined to the rooting zone, need to be refined to account for deeper weathering and spatial patterns of lateral and upward hydrologic fluxes. Similarly, recovery from cultural acidification may be limited in portions of catchments where hydrologic connections do not provide a vehicle for weathering products to recharge the biologically active portion of the subsurface.

Characteristics of mineral licks used by white-tailed deer (Odocoileus virginianus)

USGS Publications Warehouse

Kennedy, John F.; Jenks, Jonathan A.; Jones, Robert L.; Jenkins, Kurt J.

1995-01-01

Characteristics of mineral licks used by white-tailed deer (Odocoileus virginianus) were examined in the northern Black Hills of South Dakota in May 1992. Concentrations of sodium, nitrogen, phosphorus, potassium, calcium, chloride and magnesium, and soil texture, organic matter and pH for licks and nonlick soils were compared. Black Hills lick and nonlick samples also were compared to 67 other North American licks characterized by Jones and Hanson (1985). Degree of use (high or low), and vegetative and topographic characteristics also were determined. Use of mineral licks by deer was highest in spring and early summer; mineral licks were not used by deer in winter. Mostly adult females, and on a few occasions fawns visited licks. Soil texture was finer and organic matter was lower (P < 0.05) in lick than nonlick soils. Soil pH, soluble salts, sodium and nitrate nitrogen were higher (P < 0.05) in lick than in nonlick soils. Chloride was the only mineral that differed (P = 0.03) between high-use and low-use licks but was not considered important in lick selection. Sodium was the primary mineral sought by white-tailed deer using mineral licks.

Chemical Denudation and Cation Depletion in a Semi-Arid Catchment of the Long-Term Agroecological Research Observatory

NASA Astrophysics Data System (ADS)

Shaljian, M.; Keller, C. K.; Jones, K. B.; Brooks, E. S.; Huggins, D. R.

2016-12-01

The Long-Term Agroecosystem Research (LTAR) network of the USDA is a nationwide observatory and decadal-timescale field-experimental study of sustainable food production. The LTAR thus supports investigation of hydroecological and biogeochemical processes that could affect agricultural sustainability over the course of the 21st century. Mineral-derived nutrient cations are essential to fertility, and acidification of soils due to chemical fertilization may result in unsustainable chemical denudation of the soil exchange pool. Mineral weathering also contributes to base cation denudation. This study investigated base cation losses for one year in drainage from a semi-arid, rain-fed catchment at the Cook Agronomy Farm (CAF) LTAR site in southeastern Washington. We measured flows, analyzed drainage samples and estimated hydrologic effluxes of base cations from the catchment. The total dissolved base cation denudation rate at CAF-LTAR is about 40 kg ha-1 yr-1, which is comparable to other catchments on silicate terranes. The 2.1keq ha-1 yr-1 of denuded cationic charge is dominated by Ca2+ (61%) and Mg2+ (35%). Principal counter-ions are HCO3- (43%), NO3- (38%) and SO42- (16%), suggesting that both H2CO3 and HNO3 are important acids. Comparing 2008 soil pH and base saturation at CAF-LTAR to a nearby native prairie site, we preliminarily estimate a loss of 120 keq ha-1 of base cations from the upper 1.5m of the soil exchangeable cation pool. Dividing this depletion by the estimated denudation flux returns 60 years, which is approximately the interval of chemically intensive agriculture here. This may suggest that the source of exported base cations in drainage is primarily cation exchange rather than mineral weathering. The LTAR observatory will support ongoing monitoring and experimentation necessary to better understand base cation depletion and how it interacts with agroecological changes over the next several decades.

Weathering of primary minerals and mobility of major elements in soils affected by an accidental spill of pyrite tailing.

PubMed

Martín, Francisco; Diez, María; García, Inés; Simón, Mariano; Dorronsoro, Carlos; Iriarte, Angel; Aguilar, José

2007-05-25

In the present work, soil profiles were sampled 40 days and three years after an accidental pyrite tailing spill from the Aznalcóllar mine (S Spain) in order to figure out the effects of the acidic solution draining from the tailing. The composition of the acidic solution, the mineralogy, and the total and soluble content of the major elements were analysed at varying depths. The results show a weathering process of carbonates and of primary silicates. Calcium released is leached or reacts with the sulphate ions to form gypsum. Magnesium, aluminium and potassium tend to leach from the uppermost millimetres of the soil, accumulating where the pH>/=5.0; also the iron, probably forming more or less complex hydroxysulphates, precipitate in the upper 5 cm. The strong releasing of soluble salts increases the electrical conductivity, while the soluble potassium tends to decrease in the uppermost part of the soil due to the neoformation of jarosite. Iron is soluble only where the pH

Effect of N and P addition on soil organic C potential mineralization in forest soils in South China.

PubMed

Ouyang, Xuejun; Zhou, Guoyi; Huang, Zhongliang; Zhou, Cunyu; Li, Jiong; Shi, Junhui; Zhang, Deqiang

2008-01-01

Atmospheric nitrogen deposition is at a high level in some forests of South China. The effects of addition of exogenous N and P on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0-10 cm) was sampled from monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana forest (PMF) in Dinghushan Biosphere Reserve (located in Guangdong Province, China). The soils were incubated at 25 degrees C for 45 weeks, with addition of N (NH4NO3 solution) or P (KH2PO4 solution). CO2-C emission and the inorganic N (NH4(+)-N and NO3(-)-N) of the soils were determined during the incubation. The results showed that CO2-C emission decreased with the N addition. The addition of P led to a short-term sharp increase in CO2 emission after P application, and the responses of CO2-C evolution to P addition in the later period of incubation related to forest types. Strong P inhibition to CO2 emission occurred in both PMF and CBMF soils in the later incubation. The two-pool kinetic model was fitted well to the data for C turnover in this experiment. The model analysis demonstrated that the addition of N and P changed the distribution of soil organic C between the labile and recalcitrant pool, as well as their mineralization rates. In our experiment, soil pH can not completely explain the negative effect of N addition on CO2-C emission. The changes of soil inorganic N during incubation seemed to support the hypothesis that the polymerization of added nitrogen with soil organic compound by abiotic reactions during incubation made the added nitrogen retard the soil organic carbon mineralization. We conclude that atmospheric N deposition contributes to soil C accretion in the three subtropical forest ecosystems, however, the shortage of soil available P in CBMF and PMF may also retard soil organic C mineralization.

Long-term controls of soil organic carbon with depth and time: a case study from the Cowlitz River Chronosequence, WA USA

USGS Publications Warehouse

Lawrence, Corey R.; Harden, Jennifer W.; Xu, Xiaomei; Schulz, Marjorie S.; Trumbore, Susan E.

2015-01-01

Over timescales of soil development (millennia), the capacity of soils to stabilize soil organic carbon (SOC) is linked to soil development through changes in soil mineralogy and other soil properties. In this study, an extensive dataset of soil profile chemistry and mineralogy is compiled from the Cowlitz River Chronosequence (CRC), WA USA. The CRC soils range in age from 0.25 to 1200 kyr, spanning a developmental gradient encompassing clear changes in soil mineralogy, chemistry, and surface area. Comparison of these and other metrics of soil development with SOC properties reveal several relationships that may be diagnostic of the long-term coupling of soil development and C cycling. Specifically, SOC content was significantly correlated with sodium pyrophosphate extractable metals emphasizing the relevance of organo-metal complexes in volcanic soils. The depth distributions of organo-metals and other secondary weathering products, including the kaolin and short-range order (SRO) minerals, support the so-called “binary composition” of volcanic soils. The formation of organo-metal complexes limits the accumulation of secondary minerals in shallow soils, whereas in deep soils with lower SOC content, secondary minerals accumulate. In the CRC soils, secondary minerals formed in deep soils (below 50 cm) including smectite, allophane, Fe-oxides and dominated by the kaolin mineral halloysite. The abundance of halloysite was significantly correlated with bulk soil surface area and 14C content (a proxy for the mean age of SOC), implying enhanced stability of C in deep soils. Allophane, an SRO mineral commonly associated with SOC storage, was not correlated with SOC content or 14C values in CRC soils. We propose conceptual framework to describe these observations based on a general understanding of pedogenesis in volcanic soils, where SOC cycling is coupled with soil development through the formation of and fate of organo-metal or other mobile weathering products. This framework highlights interactions between SOC and soil development, which may be applicable to other soils where organic inputs interact with the products of chemical weathering.

Carbon mineralization in surface and subsurface soils in a subtropical mixed forest in central China

NASA Astrophysics Data System (ADS)

Liu, F.; Tian, Q.

2014-12-01

About a half of soil carbon is stored in subsurface soil horizons, their dynamics have the potential to significantly affect carbon balancing in terrestrial ecosystems. However, the main factors regulating subsurface soil carbon mineralization are poorly understood. As affected by mountain humid monsoon, the subtropical mountains in central China has an annual precipitation of about 2000 mm, which causes strong leaching of ions and nutrition. The objectives of this study were to monitor subsurface soil carbon mineralization and to determine if it is affected by nutrient limitation. We collected soil samples (up to 1 m deep) at three locations in a small watershed with three soil layers (0-10 cm, 10-30 cm, below 30 cm). For the three layers, soil organic carbon (SOC) ranged from 35.8 to 94.4 mg g-1, total nitrogen ranged from 3.51 to 8.03 mg g-1, microbial biomass carbon (MBC) ranged from 170.6 to 718.4 μg g-1 soil. We measured carbon mineralization with the addition of N (100 μg N/g soil), P (50 μg P/g soil), and liable carbon (glucose labeled by 5 atom% 13C, at five levels: control, 10% MBC, 50% MBC, 100% MBC, 200% MBC). The addition of N and P had negligible effects on CO2 production in surface soil layers; in the deepest soil layer, the addition of N and P decreased CO2 production from 4.32 to 3.20 μg C g-1 soil carbon h-1. Glucose addition stimulated both surface and subsurface microbial mineralization of SOC, causing priming effects. With the increase of glucose addition rate from 10% to 200% MBC, the primed mineralization rate increased from 0.19 to 3.20 μg C g-1 soil carbon h-1 (fifth day of glucose addition). The magnitude of priming effect increased from 28% to 120% as soil layers go deep compare to the basal CO2 production (fifth day of 200% MBC glucose addition, basal CO2 production rate for the surface and the deepest soil was 11.17 and 2.88 μg C g-1 soil carbon h-1). These results suggested that the mineralization of subsurface carbon is more sensitive to nutrient addition, and carbon mineralization in this layer is likely limited by carbon availability. Thus, any changes in environment conditions (global warming, nitrogen deposition, precipitation pattern change etc.) that affect the distribution of fresh carbon in soil profiles could then stimulate the release of deep soil carbon.

Migration of trace elements from pyrite tailings in carbonate soils.

PubMed

Dorronsoro, C; Martin, F; Ortiz, I; García, I; Simón, M; Fernández, E; Aguilar, J; Fernández, J

2002-01-01

In the carbonate soils contaminated by a toxic spill from a pyrite mine (Aznalcóllar, southern Spain), a study was made of a thin layer (thickness = 4 mm) of polluted soil located between the pyrite tailings and the underlying soil. This layer, reddish-yellow in color due to a high Fe content, formed when sulfates (from the oxidation of sulfides) infiltrated the soil, causing acidification (to pH 5.6 as opposed to 8.0 of unaffected soil) and pollution (in Zn, Cu, As, Pb, Co, Cd, Sb, Bi, Tl, and In). The less mobile elements (As, Bi, In, Pb, Sb, and Tl) concentrated in the uppermost part of the reddish-yellow layer, with concentration decreasing downward. The more mobile elements (Co, Cd, Zn, and Cu) tended to precipitate where the pH was basic, toward the bottom of the layer or in the upper part of the underlying soil. The greatest accumulations occurred within the first 6 mm in overall soil depth, and were negligible below 15 mm. In addition, the acidity of the solution from the tailings degraded the minerals of the clay fraction of the soils, both the phyllosilicates as well as the carbonates. Also, within the reddish-yellow layer, gypsum formed autigenically, together with complex salts of sulfates of Fe, Al, Zn, Ca, and Mn, jarosite, and oxihydroxides of Fe.

Hyperspectral Analysis of Soil Nitrogen, Carbon, Carbonate, and Organic Matter Using Regression Trees

PubMed Central

Gmur, Stephan; Vogt, Daniel; Zabowski, Darlene; Moskal, L. Monika

2012-01-01

The characterization of soil attributes using hyperspectral sensors has revealed patterns in soil spectra that are known to respond to mineral composition, organic matter, soil moisture and particle size distribution. Soil samples from different soil horizons of replicated soil series from sites located within Washington and Oregon were analyzed with the FieldSpec Spectroradiometer to measure their spectral signatures across the electromagnetic range of 400 to 1,000 nm. Similarity rankings of individual soil samples reveal differences between replicate series as well as samples within the same replicate series. Using classification and regression tree statistical methods, regression trees were fitted to each spectral response using concentrations of nitrogen, carbon, carbonate and organic matter as the response variables. Statistics resulting from fitted trees were: nitrogen R2 0.91 (p < 0.01) at 403, 470, 687, and 846 nm spectral band widths, carbonate R2 0.95 (p < 0.01) at 531 and 898 nm band widths, total carbon R2 0.93 (p < 0.01) at 400, 409, 441 and 907 nm band widths, and organic matter R2 0.98 (p < 0.01) at 300, 400, 441, 832 and 907 nm band widths. Use of the 400 to 1,000 nm electromagnetic range utilizing regression trees provided a powerful, rapid and inexpensive method for assessing nitrogen, carbon, carbonate and organic matter for upper soil horizons in a nondestructive method. PMID:23112620

Aided Phytostabilization of Copper Contaminated Soils with L. Perenne and Mineral Sorbents as Soil Amendments

NASA Astrophysics Data System (ADS)

Radziemska, Maja

2017-09-01

The present study was designed to assess phytostabilization strategies for the treatment of soil co-contaminated by increasing levels of copper with the application mineral amendments (chalcedonite, zeolite, dolomite). From the results it will be possible to further elucidate the benefits or potential risks derived from the application of different types of mineral amendments in the remediation of a copper contaminated soil. A glasshouse pot experiment was designed to evaluate the potential use of different amendments as immobilizing agents in the aided phytostabilization of Cu-contaminated soil using ryegrass (Lolium perenne L.). The content of trace elements in plants and total in soil, were determined using the method of spectrophotometry. All of the investigated element contents in the tested parts of L. perenne were significantly different in the case of applying mineral amendments to the soil, as well as increasing concentrations of copper. The greatest average above-ground biomass was observed for soil amended with chalcedonite. In this experiment, all analyzed metals accumulated predominantly in the roots of the tested plant. In general, applying mineral amendments to soil contributed to decreased levels of copper concentrations.

Chemical and Physical Interactions of Martian Surface Material

NASA Astrophysics Data System (ADS)

Bishop, J. L.

1999-09-01

A model of alteration and maturation of the Martian surface material is described involving both chemical and physical interactions. Physical processes involve distribution and mixing of the fine-grained soil particles across the surface and into the atmosphere. Chemical processes include reaction of sulfate, salt and oxidizing components of the soil particles; these agents in the soils deposited on rocks will chew through the rock minerals forming coatings and will bind surface soils together to form duricrust deposits. Formation of crystalline iron oxide/oxyhydroxide minerals through hydrothermal processes and of poorly crystalline and amorphous phases through palagonitic processes both contribute to formation of the soil particles. Chemical and physical alteration of these soil minerals and phases contribute to producing the chemical, magnetic and spectroscopic character of the Martian soil as observed by Mars Pathfinder and Mars Global Surveyor. Minerals such as maghemite/magnetite and jarosite/alunite have been observed in terrestrial volcanic soils near steam vents and may be important components of the Martian surface material. The spectroscopic properties of several terrestrial volcanic soils containing these minerals have been analyzed and evaluated in terms of the spectroscopic character of the surface material on Mars.

Soil Organic Matter and Soil Productivity: Searching for the Missing Link

Treesearch

Felipe G. Sanchez

1998-01-01

Soil-organic matter (SOM) is a complex array of components including soil fauna and flora at different stages of decomposition (Berg et al., 1982). Its concentration in soils can vary from 0.5% in mineral soils to almost 100% in peat soils (Brady, 1974). Organic matter (OM) in the surface mineral soil is considered a major determinant of forest ecosystem productivity...

Determination of Martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS)

NASA Technical Reports Server (NTRS)

Gooding, James L.; Ming, Douglas W.; Allton, Judith H.; Byers, Terry B.; Dunn, Robert P.; Gibbons, Frank L.; Pate, Daniel B.; Polette, Thomas M.

1992-01-01

Physical and chemical interactions between the surface and atmosphere of Mars can be expected to embody a strong cause-and-effect relationship with the minerals comprising the martian regolith. Many of the minerals in soils and sediments are probably products of chemical weathering (involving surface/atmosphere or surface/hydrosphere reactions) that could be expected to subsequently influence the sorption of atmospheric gases and water vapor. Therefore, identification of the minerals in martian surface soils and sediments is essential for understanding both past and present interactions between the Mars surface and atmosphere. Clearly, the most definitive mineral analyses would be achieved with well-preserved samples returned to Earth-based laboratories. In advance of a Mars sample return mission, however, significant progress could be made with in situ experiments that fill current voids in knowledge about the presence or abundance of key soil minerals such as clays (layered-structured silicates), zeolites, and various salts, including carbonates. TAPS is intended to answer that challenge by providing first-order identification of soil and sediment minerals.

Improving the Representation of Soluble Iron in Climate Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez Garcia-Pando, Carlos

2016-03-13

Mineral dust produced in the arid and semi-arid regions of the world is the dominant source of iron (Fe) in atmospheric aerosol inputs to the open ocean. The bioavailable Fe fraction of atmospheric dust is thought to regulate and occasionally limit the primary productivity in large oceanic regions, which influences the CO2 uptake from the atmosphere affecting the Earth’s climate. Because Fe bioavailability cannot be directly measured, it is assumed that the dissolved Fe or highly reactive Fe in the dust is bioavailable. The fraction of soluble Fe in dust is mainly controlled by: (1) the mineral composition of themore » soils and the emitted dust from the source areas; (2) the atmospheric processing that converts the Fe in Fe-bearing minerals into highly soluble forms of Fe. The project has mainly focused on constraining the mineral composition of dust aerosols (1), a previously neglected, yet a key issue to constrain the deposition of soluble iron. Deriving aerosol mineral composition requires global knowledge of the soil mineral content, which is available from poorly constrained global atlases. In addition, the mineral content of the emitted aerosol differs from that of the parent soil. Measurements of soil mineral fractions are based upon wet sedimentation (or ’wet sieving’) techniques that disturb the soil sample, breaking aggregates that are found in the original, undispersed soil that is subject to wind erosion. Wet sieving alters the soil size distribution, replacing aggregates that are potentially mobilized as aerosols with a collection of smaller particles. A major challenge is to derive the size-distributed mineral fractions of the emitted dust based upon their fractions measured from wet-sieved soils. Finally, representations of dust mineral composition need to account for mixtures of minerals. Examination of individual particles shows that iron, an element that is central to many climate processes, is often found as trace impurities of iron oxide attached to aggregates of other minerals. This is another challenge that has been tackled by the project. The project has produced a major step forward on our understanding of the key processes needed to predict the mineral composition of dust aerosols by connecting theory, modeling and observations. The project has produced novel semi-empirical and theoretical methods to estimate the emitted size distribution and mineral composition of dust aerosols. These methods account for soil aggregates that are potentially emitted from the original undisturbed soil but are destroyed during wet sieving. The methods construct the emitted size distribution of individual minerals building upon brittle fragmentation theory, reconstructions of wet-sieved soil mineral size distributions, and/or characteristic mineral size distributions estimated from observations at times of high concentration. Based on an unprecedented evaluation with a new global compilation of observations produced with the project support, we showed that the new methods remedy some key deficiencies compared to the previous state-of-the-art. This includes the correct representation of Fe-bearing phyllosilicates at silt sizes, where they are abundant according to observations. In addition, the quartz fraction of silt particles is in better agreement with measured values. In addition, we represent an additional class of iron oxide aerosol that is a small impurity embedded within other minerals, allowing it to travel farther than in its pure crystalline state. We assume that these impurities are least frequent in soils rich in iron oxides (as a result of the assumed effect of weathering that creates pure iron oxide crystals). The mineral composition of dust is also important to other interaction with climate - through shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, and the heterogeneous formation of sulfates and nitrates - and to its impacts upon human health. Despite the importance of mineral composition, models have typically assumed that soil dust aerosols have globally uniform composition. The results of this project will allow an improved estimation of the dust effects upon climate and health.« less

Assessing Soil Organic Carbon Stocks in Fire-Affected Pinus Palustris Forests

NASA Astrophysics Data System (ADS)

Butnor, J. R.; Johnsen, K. H.; Jackson, J. A.; Anderson, P. H.; Samuelson, L. J.; Lorenz, K.

2014-12-01

This study aimed to quantify the vertical distribution of soil organic carbon (SOC) and its biochemically resistant fraction (SOCR; defined as residual SOC following H2O2 treatment and dilute HNO3 digestion) in managed longleaf pine (LLP) stands located at Fort Benning, Georgia, USA (32.38 N., 84.88 W.). Although it is unclear how to increase SOCR via land management, it is a relatively stable carbon (C) pool that is important for terrestrial C sequestration. SOC concentration declines with soil depth on upland soils without a spodic horizon; however, the portion that is SOCR and the residence time of this fraction on LLP stands is unknown. Soils were collected by depth at five sites with common land use history, present use for active military training and a three-year prescribed fire return cycle. Soils were treated with H2O2 and dilute HNO3 to isolate SOCR. In the upper 1-m of soil SOC stocks averaged 72.1 ± 6.6 Mg C ha-1 and SOCR averaged 25.8 ± 3.2 Mg C ha-1. Depending on the site, the ratio of SOCR:SOC ranged from 0.25 to 0.50 in the upper 1-m of soil. On clayey soils the ratio of SOCR:SOC increased with soil depth. One site containing 33% clay at 50 to 100 cm depth had a SOCR:SOC ratio of 0.68. The radiocarbon age of SOCR increased with soil depth, ranging from approximately 2,000 years before present (YBP) at 0 to 10 cm to over 5,500 YBP at 50 to 100 cm depth. Across all sites, SOCR makes up a considerable portion of SOC. What isn't clear is the proportion of SOCR that is of pyrogenic origin (black carbon), versus SOCR that is stabilized by association with the mineral phase. Ongoing analysis with 13C nuclear magnetic resonance spectroscopy will provide data on the degree of aromaticity of the SOCR and some indication of the nature of its biochemical stability.

Soil Organic Carbon Loss: An Overlooked Factor in the Carbon Sequestration Potential of Enhanced Mineral Weathering

NASA Astrophysics Data System (ADS)

Dietzen, Christiana; Harrison, Robert

2016-04-01

Weathering of silicate minerals regulates the global carbon cycle on geologic timescales. Several authors have proposed that applying finely ground silicate minerals to soils, where organic acids would enhance the rate of weathering, could increase carbon uptake and mitigate anthropogenic CO2 emissions. Silicate minerals such as olivine could replace lime, which is commonly used to remediate soil acidification, thereby sequestering CO2 while achieving the same increase in soil pH. However, the effect of adding this material on soil organic matter, the largest terrestrial pool of carbon, has yet to be considered. Microbial biomass and respiration have been observed to increase with decreasing acidity, but it is unclear how long the effect lasts. If the addition of silicate minerals promotes the loss of soil organic carbon through decomposition, it could significantly reduce the efficiency of this process or even create a net carbon source. However, it is possible that this initial flush of microbial activity may be compensated for by additional organic matter inputs to soil pools due to increases in plant productivity under less acidic conditions. This study aimed to examine the effects of olivine amendments on soil CO2 flux. A liming treatment representative of typical agricultural practices was also included for comparison. Samples from two highly acidic soils were split into groups amended with olivine or lime and a control group. These samples were incubated at 22°C and constant soil moisture in jars with airtight septa lids. Gas samples were extracted periodically over the course of 2 months and change in headspace CO2 concentration was determined. The effects of enhanced mineral weathering on soil organic matter have yet to be addressed by those promoting this method of carbon sequestration. This project provides the first data on the potential effects of enhanced mineral weathering in the soil environment on soil organic carbon pools.

Soft X-ray spectromicroscopy study of mineral-organic matter associations in pasture soil clay fractions.

PubMed

Chen, Chunmei; Dynes, James J; Wang, Jian; Karunakaran, Chithra; Sparks, Donald L

2014-06-17

There is a growing acceptance that associations with soil minerals may be the most important overarching stabilization mechanism for soil organic matter. However, direct investigation of organo-mineral associations has been hampered by a lack of methods that can simultaneously characterize organic matter (OM) and soil minerals. In this study, STXM-NEXAFS spectroscopy at the C 1s, Ca 2p, Fe 2p, Al 1s, and Si 1s edges was used to investigate C associations with Ca, Fe, Al, and Si species in soil clay fractions from an upland pasture hillslope. Bulk techniques including C and N NEXAFS, Fe K-edge EXAFS spectroscopy, and XRD were applied to provide additional information. Results demonstrated that C was associated with Ca, Fe, Al, and Si with no separate phase in soil clay particles. In soil clay particles, the pervasive C forms were aromatic C, carboxyl C, and polysaccharides with the relative abundance of carboxyl C and polysaccharides varying spatially at the submicrometer scale. Only limited regions in the soil clay particles had aliphatic C. Good C-Ca spatial correlations were found for soil clay particles with no CaCO3, suggesting a strong role of Ca in organo-mineral assemblage formation. Fe EXAFS showed that about 50% of the total Fe in soils was contained in Fe oxides, whereas Fe-bearing aluminosilicates (vermiculite and Illite) accounted for another 50%. Fe oxides in the soil were mainly crystalline goethite and hematite, with lesser amounts of poorly crystalline ferrihydrite. XRD revealed that soil clay aluminosilicates were hydroxy-interlayered vermiculite, Illite, and kaolinite. C showed similar correlation with Fe to Al and Si, implying a similar association of Fe oxides and aluminosilicates with organic matter in organo-mineral associations. These direct microscopic determinations can help improve understanding of organo-mineral interactions in soils.

A hydrological tracer study of water uptake depth in a Scots pine forest under two different water regimes.

PubMed

Plamboeck, A H; Grip, H; Nygren, U

1999-05-01

Little is known about the vertical distribution of water uptake by trees under different water supply regimes, the subject of this study, conducted in a Scots pine stand on sandy loam in northern Sweden. The objective was to determine the water uptake distribution in pines under two different water regimes, desiccation (no precipitation) and irrigation (2 mm day -1 in July and 1 mm day -1 in August), and to relate the uptake to water content, root and soil texture distributions. The natural 18 O gradient in soil water was exploited, in combination with two added tracers, 2 H at 10 cm and 3 H at 20 cm depth. Extraction of xylem sap and water from the soil profile then enabled evaluation of relative water uptake from four different soil depths (humus layer, 0-10, 10-25 and 25-55 cm) in each of two 50-m 2 plots per treatment. In addition, water content, root biomass and soil texture were determined. There were differences in vertical water uptake distribution between treatments. In July, the pines at the irrigated and desiccated plots took up 50% and 30%, respectively, of their water from the upper layers, down to 25 cm depth. In August, the pines on the irrigated plots took up a greater proportion of their water from layers below 25 cm deep than they did in July. In a linear regression, the mean hydraulic conductivity for each mineral soil horizon explained a large part of the variation in relative water uptake. No systematic variation in the residual water uptake correlated to the root distribution. It was therefore concluded that the distribution of water uptake by the pines at Åheden was not a function of root density in the mineral soil, but was largely determined by the unsaturated hydraulic conductivity.

Changes in soil carbon and nutrients following 6 years of litter removal and addition in a tropical semi-evergreen rain forest

NASA Astrophysics Data System (ADS)

Tanner, Edmund Vincent John; Sheldrake, Merlin W. A.; Turner, Benjamin L.

2016-11-01

Increasing atmospheric CO2 and temperature may increase forest productivity, including litterfall, but the consequences for soil organic matter remain poorly understood. To address this, we measured soil carbon and nutrient concentrations at nine depths to 2 m after 6 years of continuous litter removal and litter addition in a semi-evergreen rain forest in Panama. Soils in litter addition plots, compared to litter removal plots, had higher pH and contained greater concentrations of KCl-extractable nitrate (both to 30 cm); Mehlich-III extractable phosphorus and total carbon (both to 20 cm); total nitrogen (to 15 cm); Mehlich-III calcium (to 10 cm); and Mehlich-III magnesium and lower bulk density (both to 5 cm). In contrast, litter manipulation did not affect ammonium, manganese, potassium or zinc, and soils deeper than 30 cm did not differ for any nutrient. Comparison with previous analyses in the experiment indicates that the effect of litter manipulation on nutrient concentrations and the depth to which the effects are significant are increasing with time. To allow for changes in bulk density in calculation of changes in carbon stocks, we standardized total carbon and nitrogen on the basis of a constant mineral mass. For 200 kg m-2 of mineral soil (approximately the upper 20 cm of the profile) about 0.5 kg C m-2 was "missing" from the litter removal plots, with a similar amount accumulated in the litter addition plots. There was an additional 0.4 kg C m-2 extra in the litter standing crop of the litter addition plots compared to the control. This increase in carbon in surface soil and the litter standing crop can be interpreted as a potential partial mitigation of the effects of increasing CO2 concentrations in the atmosphere.

Predicting isoproturon long-term mineralization from short-term experiment: Can this be a suitable approach?

PubMed

Wang, Fang; Dörfler, Ulrike; Jiang, Xin; Schroll, Reiner

2016-02-01

A worldwide used pesticide - isoproturon (IPU) - was selected to test whether short-term experiments can be used to predict long-term mineralization of IPU in soil. IPU-mineralization was measured for 39 and 265 days in four different agricultural soils with a low mineralization dynamic. Additionally, in one soil IPU dissipation, formation and dissipation of metabolites, formation of non-extractable residues (NER) and (14)C-microbial biomass from (14)C-IPU were monitored for 39 and 265 days. The data from short-term and long-term experiments were used for model fitting. The long-term dynamics of IPU mineralization were considerably overestimated by the short-term experiments in two soils with neutral pH, while in two other soils with low pH and lower mineralization, the long-term mineralization of IPU could be sufficiently predicted. Additional investigations in one of the soils with neutral pH showed that dissipation of IPU and metabolites could be correctly predicted by the short-term experiment. However, the formation of NER and (14)C-microbial biomass were remarkably overestimated by the short-term experiment. Further, it could be shown that the released NER and (14)C-microbial biomass were the main contributors of (14)CO2 formation at later incubation stages. Taken together, our results indicate that in soils with neutral pH short-term experiments were inadequate to predict the long-term mineralization of IPU. Copyright © 2015 Elsevier Ltd. All rights reserved.

Temperature sensitivity of soil organic carbon mineralization along an elevation gradient in the Wuyi Mountains, China.

PubMed

Wang, Guobing; Zhou, Yan; Xu, Xia; Ruan, Honghua; Wang, Jiashe

2013-01-01

Soil organic carbon (SOC) actively participates in the global carbon (C) cycle. Despite much research, however, our understanding of the temperature sensitivity of soil organic carbon (SOC) mineralization is still very limited. To investigate the responses of SOC mineralization to temperature, we sampled surface soils (0-10 cm) from evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (SDF), and alpine meadow (AM) along an elevational gradient in the Wuyi Mountains, China. The soil samples were incubated at 5, 15, 25, and 35°C with constant soil moisture for 360 days. The temperature sensitivity of SOC mineralization (Q(10)) was calculated by comparing the time needed to mineralize the same amount of C at any two adjacent incubation temperatures. Results showed that the rates of SOC mineralization and the cumulative SOC mineralized during the entire incubation significantly increased with increasing incubation temperatures across the four sites. With the increasing extent of SOC being mineralized (increasing incubation time), the Q(10) values increased. Moreover, we found that both the elevational gradient and incubation temperature intervals significantly impacted Q(10) values. Q(10) values of the labile and recalcitrant organic C linearly increased with elevation. For the 5-15, 15-25, and 25-35°C intervals, surprisingly, the overall Q(10) values for the labile C did not decrease as the recalcitrant C did. Generally, our results suggest that subtropical forest soils may release more carbon than expected in a warmer climate.

The response of soil solution chemistry in European forests to decreasing acid deposition.

PubMed

Johnson, James; Graf Pannatier, Elisabeth; Carnicelli, Stefano; Cecchini, Guia; Clarke, Nicholas; Cools, Nathalie; Hansen, Karin; Meesenburg, Henning; Nieminen, Tiina M; Pihl-Karlsson, Gunilla; Titeux, Hugues; Vanguelova, Elena; Verstraeten, Arne; Vesterdal, Lars; Waldner, Peter; Jonard, Mathieu

2018-03-31

Acid deposition arising from sulphur (S) and nitrogen (N) emissions from fossil fuel combustion and agriculture has contributed to the acidification of terrestrial ecosystems in many regions globally. However, in Europe and North America, S deposition has greatly decreased in recent decades due to emissions controls. In this study, we assessed the response of soil solution chemistry in mineral horizons of European forests to these changes. Trends in pH, acid neutralizing capacity (ANC), major ions, total aluminium (Al tot ) and dissolved organic carbon were determined for the period 1995-2012. Plots with at least 10 years of observations from the ICP Forests monitoring network were used. Trends were assessed for the upper mineral soil (10-20 cm, 104 plots) and subsoil (40-80 cm, 162 plots). There was a large decrease in the concentration of sulphate (SO42-) in soil solution; over a 10-year period (2000-2010), SO42- decreased by 52% at 10-20 cm and 40% at 40-80 cm. Nitrate was unchanged at 10-20 cm but decreased at 40-80 cm. The decrease in acid anions was accompanied by a large and significant decrease in the concentration of the nutrient base cations: calcium, magnesium and potassium (Bc = Ca 2+  + Mg 2+  + K + ) and Al tot over the entire dataset. The response of soil solution acidity was nonuniform. At 10-20 cm, ANC increased in acid-sensitive soils (base saturation ≤10%) indicating a recovery, but ANC decreased in soils with base saturation >10%. At 40-80 cm, ANC remained unchanged in acid-sensitive soils (base saturation ≤20%, pHCaCl2 ≤ 4.5) and decreased in better-buffered soils (base saturation >20%, pHCaCl2 > 4.5). In addition, the molar ratio of Bc to Al tot either did not change or decreased. The results suggest a long-time lag between emission abatement and changes in soil solution acidity and underline the importance of long-term monitoring in evaluating ecosystem response to decreases in deposition. © 2018 John Wiley & Sons Ltd.

The Effects of Warming and Nitrogen Addition on Soil Nitrogen Cycling in a Temperate Grassland, Northeastern China

PubMed Central

Ma, Lin-Na; Lü, Xiao-Tao; Liu, Yang; Guo, Ji-Xun; Zhang, Nan-Yi; Yang, Jian-Qin; Wang, Ren-Zhong

2011-01-01

Background Both climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood. Methodology/Principal Findings A field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland. Conclusions/Significance Interactions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem. PMID:22096609

Coexisting bacterial populations responsible for multiphasic mineralization kinetics in soil. [Janthinobacterium sp. Rhodococcus sp

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, S.K.; Gier, M.J.

1990-09-01

Experiments were conducted to study populations of indigenous microorganisms capable of mineralizing 2,4-dinitrophenol (DNP) in two soils. Previous kinetic analyses indicated the presence of two coexisting populations of DNP-mineralizing microorganisms in a forest soil (soil 1). Studies in which eucaryotic and procaryotic inhibitors were added to this soil indicated that both populations were bacterial. Most-probable-number counts with media containing different concentrations of DNP indicated that more bacteria could mineralize low concentrations of DNP than could metabolize high concentrations of it. Enrichments with varying concentrations of DNP and various combinations of inhibitors consistently resulted in the isolation of the same twomore » species of bacteria from soil 1. This soil contained a large number and variety of fungi, but no fungi capable of mineralizing DNP were isolated. The two bacterial isolates were identified as a Janthinobacterium sp. and a Rhodococcus sp. The Janthinobacterium sp. had a low {mu}{sub max} and a low K{sub m} for DNP mineralization, whereas the Rhodococcus sp. had much higher values for both parameters. These differences between the two species of bacteria were similar to differences seen when soil was incubated with different concentrations of DNP. Values for {mu}{sub max} from soil incubations were similar to {mu}{sub max} values obtained in pure culture studies. In contrast, K{sub s} and K{sub m} values showed greater variation between soil and pure culture studies.« less

Fire recurrence effects on aboveground plant and soil carbon stocks in Mediterranean shrublands with Aleppo pine

NASA Astrophysics Data System (ADS)

Herman, J.; den Ouden, J.; Mohren, G. M. J.; Retana, J.; Serrasolses, I.

2009-04-01

Changes in fire regime due to intensification of human influence during the last decades led to changes in vegetation structure and composition, productivity and carbon sink strength of Mediterranean shrublands and forests. It is anticipated that further climate warming and lower precipitation will enhance fire frequency, having consequences for the carbon budget and carbon storage in Mediterranean ecosystems. The purpose of this study was to determine whether fire recurrence modifies aboveground plant and soil carbon stocks, soil organic carbon content and total soil nitrogen content in shrublands with Aleppo pine on the Garraf Massif in Catalonia (Spain). Stands differing in fire frequency (1, 2 and 3 fires since 1957) were examined 13 years after the stand-replacing fire of 1994 and compared with control stands which were free of fire since 1957. Recurrent fires led to a decrease in total ecosystem carbon stocks. Control sites stored 12203 g m-2C which was 3.5, 5.0 and 5.5 times more than sites that burned 1, 2 and 3 times respectively. Carbon stored in the aboveground biomass exceeded soil carbon stocks in control plots, while soils were the dominant carbon pool in burned plots. An increasing fire frequency from 1 to 2 fires decreased total soil carbon stock. Control soils stored 3551 g m-2C, of which 70 % was recovered over 13 years in once burned soils and approximately 50 % in soils that had 2 or 3 fires. The soil litter (LF) layer carbon stock decreased with increasing fire frequency from 1 to 2 fires, whereas humus (H) layer and upper mineral soil carbon stocks did not change consistently with fire frequency. Fire decreased the organic carbon content in LF and H horizons, however no significant effect of fire frequency was found. Increasing fire frequency from 1 to 2 fires caused a decrease in the organic carbon content in the upper mineral soil. Total soil N content and C/N ratios were not significantly impacted by fire frequency. Recurrent fires had the greatest impact on aboveground plant carbon stocks. Aboveground plants in control plots amounted to 8652 g m-2C, of which 93 % was stored in trees, while carbon storage in the most frequently burned sites was only 509 g m-2C. Shrub carbon varied barely between fire frequencies, corroborating the high resilience of resprouting shrub species to fire recurrence. The most striking result was the immense decrease in Aleppo pine carbon stock which varied between 7770 g m-2in control plots and 25.6 g m-2in 3-fires plots. Differences between control and burned plots are principally explained by the age of the plots. The decrease in Aleppo pine carbon stock within burned plots was not associated with a growth reduction, but was due to a decrease in stem density. The results indeed indicate that the recruitment of Aleppo pine on more frequently burned plots is obstructed due to cumulative effects of short fire return-intervals (

Predicting the Mineral Composition of Dust Aerosols. Part 1; Representing Key Processes

NASA Technical Reports Server (NTRS)

Perlwitz, J. P.; Garcia-Pando, C. Perez; Miller, R. L.

2015-01-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wetsieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.

Predicting the mineral composition of dust aerosols - Part 1: Representing key processes

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Pérez García-Pando, C.; Miller, R. L.

2015-10-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.

Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems

PubMed Central

Bu, Rongyan; Lu, Jianwei; Ren, Tao; Liu, Bo; Li, Xiaokun; Cong, Rihuan

2015-01-01

Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N) mineralization. The quantity and quality of particulate organic matter (POM) and potentially mineralizable-N (PMN) contents were measured in soils from 16 paired rice-rapeseed (RR)/cotton-rapeseed (CR) rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile), intermediate (25th and 75th percentiles), and high (90th percentile) levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C) and N (POM-N) contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN) contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively) than CR rotations (45.6% and 19.5%, respectively). Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials) in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils. PMID:26647157

Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems.

PubMed

Bu, Rongyan; Lu, Jianwei; Ren, Tao; Liu, Bo; Li, Xiaokun; Cong, Rihuan

2015-01-01

Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N) mineralization. The quantity and quality of particulate organic matter (POM) and potentially mineralizable-N (PMN) contents were measured in soils from 16 paired rice-rapeseed (RR)/cotton-rapeseed (CR) rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile), intermediate (25th and 75th percentiles), and high (90th percentile) levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C) and N (POM-N) contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN) contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively) than CR rotations (45.6% and 19.5%, respectively). Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials) in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils.

AmeriFlux US-Snd Sherman Island

DOE Data Explorer

Baldocchi, Dennis [University of California, Berkeley

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-Snd Sherman Island. Site Description - The Sherman Island site is a 38-ha peatland pasture, west of the Delta, that is owned by the state and managed by the California Department of Water Resources. The site is degraded and heavily grazed with ~100 cattle in the area that circumscribes the main field and fetch. The island has been drained and farmed since the late 1800s. The soils of the Delta overlay deep peat that was sequestered over the Holocene period as sea-level rose and flooding of archaic wetlands prevented decomposition of roots and stems. Hence, the upper 10 m of peatland has been lost to decomposition, compaction, and subsidence. Today a mineral soil overlays a peat layer, which coincides with the general depth of the water table.

Patterns of Mineral Soil Nitrate Retention with Forest Age

NASA Astrophysics Data System (ADS)

Fuss, C. B.; Lovett, G. M.; Goodale, C. L.; Ollinger, S. V.; Lang, A.; Ouimette, A.

2016-12-01

Atmospheric deposition of nitrogen (N) has been elevated in the northeastern U.S. for decades and many of the region's forests have reached mature biomass and no longer have net N demands, leading biogeochemical models to predict increasing nitrate (NO3-) losses from forested watersheds. However, long-term monitoring at the Hubbard Brook Experimental Forest in New Hampshire shows an unexpected decline in stream NO3- concentrations in recent years, and suggests that poorly understood processes of retention in mineral soils may contribute to this pattern. The mineral soil is a large and heterogeneous pool of N, making changes with time difficult to quantify. We hypothesized that a reaccumulation of N in mineral soil organic matter in successional and recently matured forests is in part leading to current low NO3- losses. We used a chronosequence of four replicated forest age classes, ranging from young ( 25 y) to old growth (>200 y since disturbance) in the White Mountain region of New Hampshire to study how site age affects NO3- retention in mineral soil. We applied a 15NO3- tracer to the surface of the mineral soil beneath the forest floor and tracked the total recovery of 15N, as well as its distribution between particulate and mineral-associated (<53 mm) organic matter fractions, in the top 10 cm of mineral soil over the course of five weeks. We found the highest retention of 15N in the recently matured forests ( 100 y old), consistent with our hypothesis. Retention in the soil pool was lower in younger forests, likely due to greater root uptake to supply growth demands. The soils of the old growth forests retained low amounts of the tracer, suggesting that they are closer to N saturation. We found 15N in the mineral-associated fraction after 2 days, indicating that some NO3- is either abiotically incorporated into stabilized organic matter, or immobilized by microbes associated with mineral surfaces. We seek to combine these results with more detailed organic matter analyses to better understand these processes. Overall, our results indicate that retention of N in mineral soil layers is an important process dependent on forest age and can better inform biogeochemical models and consequently our ability to predict nutrient retention and water quality in forested watersheds.

[Responses of rhizosphere nitrogen and phosphorus transformations to different acid rain intensities in a hilly red soil tea plantation].

PubMed

Chen, Xi; Chen, Fu-sheng; Ye, Su-qiong; Yu, Su-qin; Fang, Xiang-min; Hu, Xiao-fei

2015-01-01

Tea (Camellia sinensis) plantation in hilly red soil region has been long impacted by acid deposition, however its effects on nitrogen (N) and phosphorus (P) transformations in rhizosphere soils remain unclear. A 25-year old tea plantation in a typical hilly red soil region was selected for an in situ simulation experiment treated by pH 4.5, pH 3.5, pH 2.5 and control. Rhizosihere and bulk soils were collected in the third year from the simulated acid deposition experiment. Soil mineral N, available P contents and major enzyme activities were analyzed using the chemical extraction and biochemical methods, and N and P mineralization rates were estimated using the indoor aerobic incubation methods. Our results showed that compared to the control, the treatments of pH 4.5, pH 3.5 and pH 2.5, respectively decreased 7.1%, 42.1% and 49.9% NO3(-)-N, 6.4%, 35.9% and 40.3% mineral N, 10.5%, 41.1% and 46.9% available P, 18.7%, 30.1% and 44.7% ammonification rate, 3.6%, 12.7% and 38.8% net N-mineralization rate, and 31.5%, 41.8% and 63.0% P mineralization rate in rhizosphere soils; however, among the 4 treatments, rhizosphere soil nitrification rate was not significantly different, the rhizosphere soil urease and acid phosphatase activities generally increased with the increasing intensity of acid rain (P<0.05). In bulk soil, compared with the control, the treatments of pH 4.5, pH 3.5 and pH 2.5 did not cause significant changes in NO3(-)-N, mineral N, available P as well as in the rates of nitrification, ammonification, net N-mineralization and P mineralization. With increasing the acid intensity, the rhizosphere effects of NH4+-N, NO3(-)-N, mineral N, ammonification and net N-mineralization rates were altered from positive to negative effects, those of urease and acid phosphatease showed the opposite trends, those of available P and P mineralization were negative and that of nitrification was positive. In sum, prolonged elevated acid rain could reduce N and P transformation rates, decrease their availability, alter their rhizosphere effects, and have impact on nutrient cycling in tea plantation.

Organic carbon and reducing conditions lead to cadmium immobilization by secondary Fe mineral formation in a pH-neutral soil.

PubMed

Muehe, E Marie; Adaktylou, Irini J; Obst, Martin; Zeitvogel, Fabian; Behrens, Sebastian; Planer-Friedrich, Britta; Kraemer, Ute; Kappler, Andreas

2013-01-01

Cadmium (Cd) is of environmental relevance as it enters soils via Cd-containing phosphate fertilizers and endangers human health when taken up by crops. Cd is known to associate with Fe(III) (oxyhydr)oxides in pH-neutral to slightly acidic soils, though it is not well understood how the interrelation of Fe and Cd changes under Fe(III)-reducing conditions. Therefore, we investigated how the mobility of Cd changes when a Cd-bearing soil is faced with organic carbon input and reducing conditions. Using fatty acid profiles and quantitative PCR, we found that both fermenting and Fe(III)-reducing bacteria were stimulated by organic carbon-rich conditions, leading to significant Fe(III) reduction. The reduction of Fe(III) minerals was accompanied by increasing soil pH, increasing dissolved inorganic carbon, and decreasing Cd mobility. SEM-EDX mapping of soil particles showed that a minor fraction of Cd was transferred to Ca- and S-bearing minerals, probably carbonates and sulfides. Most of the Cd, however, correlated with a secondary iron mineral phase that was formed during microbial Fe(III) mineral reduction and contained mostly Fe, suggesting an iron oxide mineral such as magnetite (Fe3O4). Our data thus provide evidence that secondary Fe(II) and Fe(II)/Fe(III) mixed minerals could be a sink for Cd in soils under reducing conditions, thus decreasing the mobility of Cd in the soil.

[Spatial heterogeneity of surface soil mineral components in a small catchment in Karst peak-cluster depression area, South China].

PubMed

Gao, Peng; Fu, Tong-Gang; Wang, Ke-Lin; Chen, Hong-Song; Zeng, Fu-Ping

2013-11-01

A total of 163 soil samples (0-20 cm layer) were collected from the grid sampling plots (80 m x 80 m) in Huanjiang Observation and Research Station of Karst Ecosystem in a small catchment in Karst cluster-peak depression area, South China. By using classical statistics and geostatistics, the spatial heterogeneity of mineral components (SiO2, Fe2O3, CaO, MgO, Al2O3, MnO, and TiO2) in the soils were studied. The contents of the seven soil mineral components in the study area differed greatly, being in the order of SiO2 > Al2O3 > CaO > MgO > Fe2O3 > TiO2 > MnO, and the variance coefficients also varied obviously, in the order of CaO > MgO > Fe2O3 > TiO2 > SiO2 > Al2O3 > MnO. The seven mineral components accounted for 69.4% of the total soil mass. The spatial patterns and the fittest models of the seven soil mineral components differed from each other. All the seven soil mineral components had a strong spatial autocorrelation, with shorter variation ranges and stronger spatial dependence. The Kriging contour maps indicated that the distribution patterns of soil SiO2, Fe2O3, Al2O3, MnO, and TiO2 were similar, being higher in south and east, lower in north and west, higher in depression, and lower in slope, while the distribution patterns of soil CaO and MgO were in adverse. Natural conditions (vegetation, bare rock rate, slope degree, and slope aspect, etc. ) and human disturbance were the most important factors affecting the spatial patterns of the soil mineral components.

Biological Control on Mineral Transformation in Soils ?

NASA Astrophysics Data System (ADS)

Ziegler, K.; Hsieh, J. C.; Chadwick, O. A.; Kelly, E. F.

2001-12-01

Weathering of primary minerals is commonly linked to biological processes through the production of carbonic and organic acids. Plants can also play a role in weathering by removing soluble constituents and enhancing diffusion gradients within the soil. Here we investigate the synthesis of secondary minerals and the role of plants in removing elements that act as building blocks for these minerals. In order to minimize losses from leaching, we have sampled a chronosequence of soils forming on lava flows on Hawaii Island that receive about 200 mm of rain annually and have never been subjected to high levels of rainfall. The P concentration in the soils drops from almost 3000 mg/kg on a 1.5 ky lava flow to around 1000 mg/kg on a 350 ky lava flow. This loss of P can only be ascribed to P-uptake by plants with subsequent removal through the loss of above ground biomass through fire and/or wind removal. Over the same time frame the amount of plagioclase in the soils drops from around 22% of the <2 mm soil fraction on the youngest lava flow to virtually 0% on the 350 ky flow, suggesting a substantial release of Si. Elevated silicon in arid, basaltic soil environments often leads to formation of smectite, a feature not observed along the chronosequence. In fact, plagioclase is replaced by the kaolin mineral halloysite with allophane as an apparent precursor. Kaolin minerals are associated with moderate to intense leaching environments rather than the mild leaching conditions that influence these soils. We selected an intermediate age soil profile (170 ky lava flow) to conduct an in-depth investigation of the soil mineral composition. We detected a strong dominance of halloysite, the presence of gibbsite, but no smectite. Secondary halloysite formation is preferred over smectite formation when Si activities are relatively low, and the pH is acidic rather than alkaline. Although this mineral assemblage seems to imply formation under a wetter climatic regime, the oxygen isotopic composition of the halloysite suggests formation under soil environmental conditions similar to the present. The Si concentration in grass and tree leaves in the vicinity of the soil contain between 3 and 8% Si. Loss of these leaves to the nearby ocean (either as dried or burned residue) could be responsible for considerable Si removal in a manner similar to the P-removal. The resulting Si-deficient soil-water favors the formation of halloysite over smectite as is demonstrated by construction of mineral stability diagrams using the soil-water data from the soils along the chronosequence.

Elevated moisture stimulates carbon loss from mineral soils by releasing protected organic matter.

PubMed

Huang, Wenjuan; Hall, Steven J

2017-11-24

Moisture response functions for soil microbial carbon (C) mineralization remain a critical uncertainty for predicting ecosystem-climate feedbacks. Theory and models posit that C mineralization declines under elevated moisture and associated anaerobic conditions, leading to soil C accumulation. Yet, iron (Fe) reduction potentially releases protected C, providing an under-appreciated mechanism for C destabilization under elevated moisture. Here we incubate Mollisols from ecosystems under C 3 /C 4 plant rotations at moisture levels at and above field capacity over 5 months. Increased moisture and anaerobiosis initially suppress soil C mineralization, consistent with theory. However, after 25 days, elevated moisture stimulates cumulative gaseous C-loss as CO 2 and CH 4 to >150% of the control. Stable C isotopes show that mineralization of older C 3 -derived C released following Fe reduction dominates C losses. Counter to theory, elevated moisture may significantly accelerate C losses from mineral soils over weeks to months-a critical mechanistic deficiency of current Earth system models.

A simple method to determine mineralization of (14) C-labeled compounds in soil.

PubMed

Myung, Kyung; Madary, Michael W; Satchivi, Norbert M

2014-06-01

Degradation of organic compounds in soil is often determined by measuring the decrease of the parent compound and analyzing the occurrence of its metabolites. However, determining carbon species as end products of parent compound dissipation requires using labeled materials that allow more accurate determination of the environmental fate of the compound of interest. The current conventional closed system widely used to monitor degradation of (14) C-labeled compounds in soil is complex and expensive and requires a specialized apparatus and facility. In the present study, the authors describe a simple system that facilitates measurement of mineralization of (14) C-labeled compounds applied to soil samples. In the system, soda lime pellets to trap mineralized (14) C-carbon species, including carbon dioxide, were placed in a cup, which was then inserted above the treated soil sample in a tube. Mineralization of [(14) C]2,4-D applied to soil samples in the simple system was compared with that in the conventional system. The simple system provided an equivalent detection of (14) C-carbon species mineralized from the parent compound. The results demonstrate that this cost- and space-effective simple system is suitable for examining degradation and mineralization of (14) C-labeled compounds in soil and could potentially be used to investigate their mineralization in other biological matrices. © 2014 SETAC.

Influence of crop residues on trifluralin mineralization in a silty clay loam soil.

PubMed

Farenhorst, Annemieke

2007-01-01

Trifluralin is typically applied onto crop residues (trash, stubble) at the soil surface, or onto the bare soil surface after the incorporation of crop residues into the soil. The objective of this study was to quantify the effect of the type and amount of crop residues in soil on trifluralin mineralization in a Wellwood silty clay loam soil. Leaves and stubble of Potato (Solanum tuberosum) (P); Canola (Brassica napus) (C), Wheat (Triticum aestivum) (W), Oats (Avena sativa), (O), and Alfalfa (Medicago sativa) (A) were added to soil microcosms at rates of 2%, 4%, 8% and 16% of the total soil weight (25 g). The type and amount of crop residues in soil had little influence on the trifluralin first-order mineralization rate constant, which ranged from 3.57E-03 day(-1) in soil with 16% A to 2.89E-02 day(-1) in soil with 8% W. The cumulative trifluralin mineralization at 113 days ranged from 1.15% in soil with 16% P to 3.21% in soil with 4% C, again demonstrating that the observed differences across the treatments are not of agronomic or environmental importance.

Origin and Reactivity of the Martian Soil: A 2003 Micromission

NASA Astrophysics Data System (ADS)

Yen, Albert S.; Kim, S. Sam; Marshall, John; Murray, Bruce C.

1999-09-01

The role of water in the development of the martian surface remains a fundamental scientific question. Did Mars have one or more "warm and wet" climatic episodes where liquid water was stable at the surface? If so, the mineral phases present in the soils should be consistent with a history of aqueous weathering. More generally, the formation of hydrated mineral phases on Mars is a strong indicator of past habitable surface environments. The primary purpose of this investigation is to help resolve the question of whether such aqueous indicators are present on Mars by probing the upper meter for diagnostic mineral species. According to Burns [1993], the formation of the ferric oxides responsible for the visible color of Mars are the result of dissolution of Fe (+2) phases from basalts followed by aqueous oxidation and precipitation of Fe" mineral assemblages. These precipitates likely included iron oxyhydroxides such as goethite (a-FeOOH) and lepidocrocite (g-FeOOH), but convincing evidence for these phases at the surface is still absent. The stability of these minerals is enhanced beneath the surface, and thus we propose a subsurface search for hydroxylated iron species as a test for a large-scale chemical weathering process based on interactions with liquid water. It is also possible that the ferric minerals on Mars are not aqueous alteration products of the rocks. A chemical study of the Pathfinder landing site concluded that the soils are not directly derived from the surrounding rocks and are enhanced in Mg and Fe. The additional source of these elements might be from other regions of Mars and transported by winds, or alternatively, from exogenic sources. Gibson [1970] proposed that the spectral reflectivity of Mars is consistent with oxidized meteoritic material. Yen and Murray [1998] further extend Gibson's idea and show, in the laboratory, that metallic iron can be readily oxidized to maghemite and hematite under present-day martian surface conditions (in the absence of liquid water). A test for a meteoritic component of the soil can be conducted, as described below, by searching for the presence of Ni at the martian surface. The average abundance of nickel in an Fe-Ni meteorite is about 7% and, if present at measurable levels in the soil, would be indicative of an exogenic contribution. In addition, it may be possible to directly search for mineral phases common in meteorites. An understanding of the formation and evolution of the martian soil would not be complete without addressing the unusual reactivity discovered by the Viking Landers The presence of an inorganic oxidant, possibly one produced as a results of photochemical processes, is the most widely accepted explanation of the Viking results. Are these chemical species simply adsorbed on soil grains, or have they reacted with the metal oxide substrates and altered the mineral structures? Could a completely different (non-photochemical) process be responsible for the soil reactivity? The various ideas for the nature of this putative oxidant could be constrained by a measurement of the change in reactivity with depth. Different compositions will have different lifetimes and mobilities and thus will have different vertical profiles. Because the oxidizing compounds are believed to actively destroy organic molecules, determination of the reactivity gradient also has significant implications for the search for life on Mars. A DS2-based microprobe system can be instrumented for a 2003 micromission to investigate the origin and reactivity of the martian soil. These measurements would provide invaluable information regarding the climate history and exobiological potential of the planet. The NMR, X ray and chemiresistor measurement approach described embodies a highly synergistic and general set of soil interrogation methods for elements, compounds, and crystal structures and can also be applied to other geologic questions of interest. For example, if the capability for precise targeting of the probes is available, then in-situ investigations of suspected evaporite and hydrothermal deposits would be possible with the same set of instruments. Additional information is contained in the original.

Origin and Reactivity of the Martian Soil: A 2003 Micromission

NASA Technical Reports Server (NTRS)

Yen, Albert S.; Kim, S. Sam; Marshall, John; Murray, Bruce C.

1999-01-01

The role of water in the development of the martian surface remains a fundamental scientific question. Did Mars have one or more "warm and wet" climatic episodes where liquid water was stable at the surface? If so, the mineral phases present in the soils should be consistent with a history of aqueous weathering. More generally, the formation of hydrated mineral phases on Mars is a strong indicator of past habitable surface environments. The primary purpose of this investigation is to help resolve the question of whether such aqueous indicators are present on Mars by probing the upper meter for diagnostic mineral species. According to Burns [1993], the formation of the ferric oxides responsible for the visible color of Mars are the result of dissolution of Fe (+2) phases from basalts followed by aqueous oxidation and precipitation of Fe" mineral assemblages. These precipitates likely included iron oxyhydroxides such as goethite (a-FeOOH) and lepidocrocite (g-FeOOH), but convincing evidence for these phases at the surface is still absent. The stability of these minerals is enhanced beneath the surface, and thus we propose a subsurface search for hydroxylated iron species as a test for a large-scale chemical weathering process based on interactions with liquid water. It is also possible that the ferric minerals on Mars are not aqueous alteration products of the rocks. A chemical study of the Pathfinder landing site concluded that the soils are not directly derived from the surrounding rocks and are enhanced in Mg and Fe. The additional source of these elements might be from other regions of Mars and transported by winds, or alternatively, from exogenic sources. Gibson [1970] proposed that the spectral reflectivity of Mars is consistent with oxidized meteoritic material. Yen and Murray [1998] further extend Gibson's idea and show, in the laboratory, that metallic iron can be readily oxidized to maghemite and hematite under present-day martian surface conditions (in the absence of liquid water). A test for a meteoritic component of the soil can be conducted, as described below, by searching for the presence of Ni at the martian surface. The average abundance of nickel in an Fe-Ni meteorite is about 7% and, if present at measurable levels in the soil, would be indicative of an exogenic contribution. In addition, it may be possible to directly search for mineral phases common in meteorites. An understanding of the formation and evolution of the martian soil would not be complete without addressing the unusual reactivity discovered by the Viking Landers The presence of an inorganic oxidant, possibly one produced as a results of photochemical processes, is the most widely accepted explanation of the Viking results. Are these chemical species simply adsorbed on soil grains, or have they reacted with the metal oxide substrates and altered the mineral structures? Could a completely different (non-photochemical) process be responsible for the soil reactivity? The various ideas for the nature of this putative oxidant could be constrained by a measurement of the change in reactivity with depth. Different compositions will have different lifetimes and mobilities and thus will have different vertical profiles. Because the oxidizing compounds are believed to actively destroy organic molecules, determination of the reactivity gradient also has significant implications for the search for life on Mars. A DS2-based microprobe system can be instrumented for a 2003 micromission to investigate the origin and reactivity of the martian soil. These measurements would provide invaluable information regarding the climate history and exobiological potential of the planet. The NMR, X ray and chemiresistor measurement approach described embodies a highly synergistic and general set of soil interrogation methods for elements, compounds, and crystal structures and can also be applied to other geologic questions of interest. For example, if the capability for precise targeting of the probes is available, then in-situ investigations of suspected evaporite and hydrothermal deposits would be possible with the same set of instruments. Additional information is contained in the original.

The effects of more extreme rainfall patterns on nitrogen leaching from a field crop system in the upper Midwest, USA

NASA Astrophysics Data System (ADS)

Hess, L.; Hinckley, E. L. S.; Robertson, G. P.; Matson, P. A.

2016-12-01

As global surface temperatures rise, the proportion of total rainfall that falls in heavy storm events is increasing in many areas, in particular the US Midwest, a major agricultural region. These changes in rainfall patterns may have consequences for ecosystem nutrient losses, especially from agricultural ecosystems. We conducted a multi-year rainfall manipulation experiment to examine how more extreme rainfall patterns affect nitrogen (N) leaching from row-crop ecosystems in the upper Midwest, and to what extent tillage may moderate these effects. 5x5m rainout shelters were installed in April 2015 to impose control and extreme rainfall patterns in replicated plots under conventional tillage and no-till management at the Kellogg Biological Station LTER site. Plots exposed to the control rainfall treatment received ambient rainfall, and those exposed to the extreme rainfall treatment received the same total amount of water but applied once every 2 weeks, to simulate larger, less frequent storms. N leaching was calculated as the product of measured soil water N concentrations and modeled soil water drainage at 1.2m depth using HYDRUS-1D. Based on data to date, more N has been leached from both tilled and no-till soils exposed to the extreme rainfall treatment compared to the control rainfall treatment. Results thus far suggest that greater soil water drainage is a primary driver of this increase, and changes in within-system nitrogen cycling - such as net N mineralization and crop N uptake - may also play a role. The experiment is ongoing, and our results so far suggest that intensifying precipitation patterns may exacerbate N leaching from agricultural soils, with potentially negative consequences for receiving ground- and surface waters, as well as for farmers.

Temperature response of permafrost soil carbon is attenuated by mineral protection.

PubMed

Gentsch, Norman; Wild, Birgit; Mikutta, Robert; Čapek, Petr; Diáková, Katka; Schrumpf, Marion; Turner, Stephanie; Minnich, Cynthia; Schaarschmidt, Frank; Shibistova, Olga; Schnecker, Jörg; Urich, Tim; Gittel, Antje; Šantrůčková, Hana; Bárta, Jiři; Lashchinskiy, Nikolay; Fuß, Roland; Richter, Andreas; Guggenberger, Georg

2018-05-18

Climate change in Arctic ecosystems fosters permafrost thaw and makes massive amounts of ancient soil organic carbon (OC) available to microbial breakdown. However, fractions of the organic matter (OM) may be protected from rapid decomposition by their association with minerals. Little is known about the effects of mineral-organic associations (MOA) on the microbial accessibility of OM in permafrost soils and it is not clear which factors control its temperature sensitivity. In order to investigate if and how permafrost soil OC turnover is affected by mineral controls, the heavy fraction (HF) representing mostly MOA was obtained by density fractionation from 27 permafrost soil profiles of the Siberian Arctic. In parallel laboratory incubations, the unfractionated soils (bulk) and their HF were comparatively incubated for 175 days at 5 and 15°C. The HF was equivalent to 70 ± 9% of the bulk CO 2 respiration as compared to a share of 63 ± 1% of bulk OC that was stored in the HF. Significant reduction of OC mineralization was found in all treatments with increasing OC content of the HF (HF-OC), clay-size minerals and Fe or Al oxyhydroxides. Temperature sensitivity (Q10) decreased with increasing soil depth from 2.4 to 1.4 in the bulk soil and from 2.9 to 1.5 in the HF. A concurrent increase in the metal-to-HF-OC ratios with soil depth suggests a stronger bonding of OM to minerals in the subsoil. There, the younger 14 C signature in CO 2 than that of the OC indicates a preferential decomposition of the more recent OM and the existence of a MOA fraction with limited access of OM to decomposers. These results indicate strong mineral controls on the decomposability of OM after permafrost thaw and on its temperature sensitivity. Thus, we here provide evidence that OM temperature sensitivity can be attenuated by MOA in permafrost soils. © 2018 John Wiley & Sons Ltd.

Reconciling drainage and receiving basin signatures of the Godavari River system

NASA Astrophysics Data System (ADS)

Ojoshogu Usman, Muhammed; Kirkels, Frédérique Marie Sophie Anne; Zwart, Huub Michel; Basu, Sayak; Ponton, Camilo; Blattmann, Thomas Michael; Ploetze, Michael; Haghipour, Negar; McIntyre, Cameron; Peterse, Francien; Lupker, Maarten; Giosan, Liviu; Eglinton, Timothy Ian

2018-06-01

The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OCterr; 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OCterr is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFAs), sedimentological properties (e.g. grain size, mineral surface area, etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e. mineral surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in the preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ13C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more 13C enriched carbon than the lower stream, resulting from the regional vegetation gradient and/or net balance between the upper (C4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ14COC) in deep soils and eroding riverbanks suggests these are likely sources of old or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. While changes in water flow and sediment transport resulting from recent dam construction have drastically impacted the flux, loci, and composition of OC exported from the modern Godavari basin, complicating reconciliation of modern-day river basin geochemistry with that recorded in continental margin sediments, such investigations provide important insights into climatic and anthropogenic controls on OC cycling and burial.

Phytoavailability and extractability of potassium, magnesium and manganese in calcareous soil amended with olive oil wastewater.

PubMed

Gallardo-Lara, F; Azcón, M; Polo, A

2000-09-01

Land disposal of olive oil wastewater using it as a soil amendment requires a knowledge of the effects that its application may produce on the status of the mineral nutrients in the plant-soil system. A pot experiment using calcareous soil was performed in a growth chamber to examine the effects of olive oil wastewater on the availability and postharvest soil extractability of K, Mg and Mn. The experiment included 6 treatments: two rates of olive oil wastewater, two mineral fertilizer treatments containing K (which supplied K in amounts equivalent to the K supplied by the olive oil wastewater treatments), a K-free mineral fertilizer treatment, and a control. The pots were sown with ryegrass as the test plant, harvesting 3 times at intervals of one month. Olive oil wastewater has demonstrated a considerable capacity for supplying K that can be assimilated by the plant, tending in fact to surpass the mineral potassium fertilizer tested. The application of olive oil wastewater tends to reduce the concentration of Mg in the plant, similarly to the effect of adding mineral potassium fertilizer. An enhancement of Mn availability takes place in the soil amended with olive oil wastewater, which on occasion has produced Mn concentrations in plant that could be considered phytotoxic or at least excessive. After harvesting, we observed an increase in the amount of exchangeable K in soil with added industrial wastewater. However, these increases are lower than those in soil treated with mineral potassium fertilizer. The levels of exchangeable, carbonate-bound, organic-bound and residual Mg in soil were higher in treatments incorporating olive oil wastewater than in those with added mineral K, with the opposite tendency occurring in the amount of Fe-Mn oxides-bound Mg in soil. Treatments based on olive oil wastewater, especially in high doses, increased the amount of exchangeable and carbonate-bound Mn in soil, in comparison with treatments adding mineral fertilizers with or without K. In contrast, the addition of industrial wastewater caused a drop in the amount of Fe-Mn oxides-bound and organic-bound Mn in soil.

Petrographic characterization of lunar soils: Application of x ray digital-imaging to quantitative and automated analysis

NASA Technical Reports Server (NTRS)

Higgins, Stefan J.; Patchen, Allan; Chambers, John G.; Taylor, Lawrence A.; Mckay, David S.

1994-01-01

The rocks and soils of the moon will be the raw materials for various engineering needs at a lunar base, such as sources of hydrogen, oxygen, metals, etc. The material of choice for most of the bulk needs is the regolith and its less than 1 cm fraction, the soil. For specific mineral resources it may be necessary to concentrate minerals from either rocks or soils. Therefore, quantitative characterizations of these rocks and soils are necessary in order to better define their mineral resource potential. However, using standard point-counting microscopic procedures, it is difficult to quantitatively determine mineral abundances and virtually impossible to obtain data on mineral distributions within grains. As a start to fulfilling these needs, Taylor et al. and Chambers et al. have developed a procedure for characterization of crushed lunar rocks using x ray digital imaging. The development of a similar digital imaging procedure for lunar soils as obtained from a spectrometer is described.

Impact of clay mineral on air oxidation of PAH-contaminated soils.

PubMed

Biache, Coralie; Kouadio, Olivier; Lorgeoux, Catherine; Faure, Pierre

2014-09-01

This work investigated the impact of a clay mineral (bentonite) on the air oxidation of the solvent extractable organic matters (EOMs) and the PAHs from contaminated soils. EOMs were isolated from two coking plant soils and mixed with silica sand or bentonite. These samples, as well as raw soils and bentonite/soil mixtures, were oxidized in air at 60 and 100 °C for 160 days. Mineralization was followed by measuring the CO2 produced over the experiments. EOM, polycyclic aromatic compound (PAC), including PAH, contents were also determined. Oxidation led to a decrease in EOM contents and PAH concentrations, these diminutions were enhanced by the presence of bentonite. Transfer of carbon from EOM to insoluble organic matter pointed out a condensation phenomenon leading to a stabilization of the contamination. Higher mineralization rates, observed during the oxidation of the soil/bentonite mixtures, seem to indicate that this clay mineral had a positive influence on the transformation of PAC into CO2.

Mapping field spatial distribution patterns of isoproturon-mineralizing activity over a three-year winter wheat/rape seed/barley rotation.

PubMed

Hussain, S; Devers-Lamrani, M; Spor, A; Rouard, N; Porcherot, M; Beguet, J; Martin-Laurent, F

2013-03-01

The temporal and spatial variability of the activity of soil microorganisms able to mineralize the herbicide isoproturon (IPU) pesticide was investigated over a three-year long crop rotation between 2008 and 2010. Isoproturon mineralization was higher in 2008, when winter wheat was treated with this herbicide, than in 2009 and 2010, when rape seed and barley were treated with different herbicides. Under laboratory conditions, we showed that isoproturon mineralization was not promoted by sulfonylurea herbicide applied on barley crop in 2010. IPU mineralization was shown to be highly variable at the field scale in years 2009 and 2010. Principal component analyses and analyses of similarities revealed that soil pH and equivalent humidity, and to a lesser extent soil organic matter content and cation exchange capacity (CEC) were the main drivers of isoproturon-mineralizing activity variance. Using a rather simple model that yields the rate of isoproturon mineralization as a function of soil pH and equivalent humidity, we explained up to 85% of the variance observed. Mapping field-scale distribution of isoproturon mineralization over the three-year survey indicated higher variability in 2009 and in 2010 as compared to 2008, suggesting that isoproturon treatment applied to winter wheat promoted isoproturon mineralization activity and reduced its spatial variability. Field-scale distribution of isoproturon mineralization showed important similarity to the distribution of soil pH, equivalent humidity and to a lesser extent to soil organic matter and cation exchange capacity (CEC) thereby confirming our model. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biodegradation of 1,2,3- and 1,2,4-Trichlorobenzene in Soil and in Liquid Enrichment Culture †

PubMed Central

Marinucci, A. C.; Bartha, R.

1979-01-01

The biodegradation of radiochemically pure (99%) 1,2,3- and 1,2,4-trichlorobenzene (TCB) in soil was investigated. Experimental difficulties posed by the high volatility and slow biodegradation rate of the TCBs were partially overcome by using a specially designed incubation and trapping apparatus. Evolution of 14CO2 from active versus poisoned soil dosed with 50 μg of the individual TCBs per g gave conclusive proof that both isomers are biodegradable. At 20°C, 1,2,4-TCB was mineralized at an approximate rate of 1 nmol/day per 20 g of soil sample, and 1,2,3-TCB was mineralized at one-half to one-third that rate. Mineral fertilizers or cosubstrates failed to increase TCB mineralization rates in soil. Anaerobic conditions had a negative effect on mineralization, and increased temperatures had a positive effect. With increasing 1,2,4-TCB concentrations, 14CO2 evolution exhibited saturation kinetics with an apparent Km of 55.5 nmol per g of soil. Recovery of total radioactivity was good from soil containing high organic matter concentrations. From low-organic-matter soil, some of the radioactivity was recovered only on combustion, and overall recovery was lower. In soil-inoculated liquid culture, the cosubstrates glucose and benzene caused a slight stimulation of 1,2,4-TCB mineralization. Cochromatography of known standards with the extracts of soil pretreated with [14C]TCBs indicated that 3,4,5-trichlorophenol, 2,6-dichlorophenol and, to a lesser degree, 2,3-dichlorophenol were present in soils incubated with 1,2,3-TCB. 2,4-, 2,5-, and 3,4-dichlorophenol were present in soils incubated with 1,2,4-TCB. PMID:120698

Nitrogen-rich microbial products provide new organo-mineral associations for the stabilization of soil organic matter.

PubMed

Kopittke, Peter M; Hernandez-Soriano, Maria C; Dalal, Ram C; Finn, Damien; Menzies, Neal W; Hoeschen, Carmen; Mueller, Carsten W

2018-04-01

Understanding the cycling of C and N in soils is important for maintaining soil fertility while also decreasing greenhouse gas emissions, but much remains unknown about how organic matter (OM) is stabilized in soils. We used nano-scale secondary ion mass spectrometry (NanoSIMS) to investigate the changes in C and N in a Vertisol and an Alfisol incubated for 365 days with 13 C and 15 N pulse labeled lucerne (Medicago sativa L.) to discriminate new inputs of OM from the existing soil OM. We found that almost all OM within the free stable microaggregates of the soil was associated with mineral particles, emphasizing the importance of organo-mineral interactions for the stabilization of C. Of particular importance, it was also found that 15 N-rich microbial products originating from decomposition often sorbed directly to mineral surfaces not previously associated with OM. Thus, we have shown that N-rich microbial products preferentially attach to distinct areas of mineral surfaces compared to C-dominated moieties, demonstrating the ability of soils to store additional OM in newly formed organo-mineral associations on previously OM-free mineral surfaces. Furthermore, differences in 15 N enrichment were observed between the Vertisol and Alfisol presumably due to differences in mineralogy (smectite-dominated compared to kaolinite-dominated), demonstrating the importance of mineralogy in regulating the sorption of microbial products. Overall, our findings have important implications for the fundamental understanding of OM cycling in soils, including the immobilization and storage of N-rich compounds derived from microbial decomposition and subsequent N mineralization to sustain plant growth. © 2017 John Wiley & Sons Ltd.

Soil carbon storages and erosional exports along a forested denudation gradient in the Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Yoo, K.; Wang, X.; Mudd, S. M.; Weinman, B.; Gutknecht, J.; Gabet, E. J.

2017-12-01

Eroding uplands not only provide physically mixed soil zones where OC and minerals actively interact but also are the significant sources of suspended sediments and organic carbon (OC) to rivers. Here our goal is to quantify the extents that erosion affects soils' capacities to store OC in different degrees of mineral-association and to facilitate the exports of minerals that might capture OC on their reactive surfaces. We examined a tributary basin to the Middle Folk Feather River in California, where knickpoint migration has created a series of hillslopes with erosion rates varying from 35 to 250 mm kyr-1. Other than erosion rates, the studied hillslopes within the tributary basin shared similar environmental factors. Soil samples were collected from select hillslopes that differ in their relative positions to knikpoints and were subject to size and density fractionation. Despite the substantial difference in erosion rates, concentrations of particulate OC (POC) and mineral-associated OC (MOC) and soil thickness varied little. Instead, considerable increase in coarse rock contents positively associated with erosion rate was responsible for the reduction of soil OC inventories by 37% with increasing erosion rate. In contrast to consistent MOC concentrations across the erosion gradient, clay contents in soils are negatively correlated with erosion rates. This seemingly contradictory result, however, is consistent with BET mineral specific surface area that remains insensitive to erosion rates. OC coverage on mineral surface was found to be less than < 50%, indicating that eroded minerals would have a significant, and currently unknown, capacity to adsorb additional OC during their transport to sediment sinks. This study thus reveals that mineral weathering acts as an important filter through which erosion affects the soil carbon cycle.

Impact of methylene chloride on microorganisms and phenanthrene mineralization in soil.

PubMed

Schwartz, Egbert; Trinh, Sinh V; Scow, Kate M

2002-01-01

This study investigated the effects of the quantity of methylene chloride, used as a carrier solvent for phenanthrene when added to soil, on phenanthrene mineralization kinetics, soil phospholipid fatty add profiles (PLFA), and phenanthrene distribution. Methylene chloride dosages of 25 microL/g soil or more resulted in an enrichment of saturated PLFAs, suggesting soil microorganisms had adjusted their cell membranes in response to the solvent. A greater fraction of phenanthrene mineralized when spiked in 5 microL/g than in 25 microL/g methylene chloride suggesting that the methylene chloride became toxic to phenanthrene-degrading organisms in soil. Phenanthrene was more equally distributed among 0.1 g soil subsamples if spiked in 25 than 5 or 1 microL methylene chloride per gram soil. Thus the amount of methylene chloride used to spike phenanthrene in soil strongly impacted the mineralization kinetics, phenanthrene distribution, and microbial community in soil. Because a variety of spiking methods are used in biodegradation research, scientists should consider the quantity of solvents used when comparing results among different studies.

Root-driven Weathering Impacts on Mineral-Organic Associations in Deep Soil

NASA Astrophysics Data System (ADS)

Keiluweit, M.; Garcia Arredondo, M.; Tfaily, M. M.; Kukkadapu, R. K.; Schulz, M. S.; Lawrence, C. R.

2017-12-01

Plant roots dramatically reshape the soil environments through the release of organic compounds. While root-derived organic compounds are recognized as an important source of soil C, their role in promoting weathering reactions has largely been overlooked. On the one hand, root-driven weathering may generate mineral-organic associations, which can protect soil C for centuries to millennia. On the other hand, root-driven weathering also transforms minerals, potentially disrupting protective mineral-organic associations in the process. Hence root-derived C may not only initiate C accumulation, but also diminish C stocks through disruption of mineral-organic associations. Here we determined the impact of rhizogenic weathering on mineral-organic associations, and associated changes in C storage, across the Santa Cruz Marine Terrace chronosequence (65ka-226ka). Using a combination of high-resolution mass spectrometry, Mössbauer, and X-ray (micro)spectroscopy, we examined mineral-organic associations of deep soil horizons characterized by intense rhizogenic weathering gradients. Initial rhizogenic weathering dramatically increased C stocks, which is directly linked to an increase of microbially-derived C bound to monomeric Fe and Al and nano-goethite. As weathering proceeded, the soil C stocks declined concurrent with an increasingly plant-derived C signature and decreasing crystallinity. X-ray spectromicroscopic analyses revealed strong spatial associations between C and Fe during initial weathering stages, indicative of protective mineral-organic associations. In contrast, later weathering stages showed weaker spatial relationships between C and Fe. We conclude that rhizogenic weathering enhance C storage by creating protective mineral-organic associations in the initial weathering stages. As root-driven weathering proceeds, minerals are transformed into more crystalline phases that retain lower amounts of C. Our results demonstrate that root-induced weathering reactions are primary drivers of the dynamics of mineral-organic associations, and are thus critical for future predictions of the vulnerability of deep soil carbon to climate change.

Soil organic carbon and total nitrogen gains in an old growth deciduous forest in Germany.

PubMed

Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

2014-01-01

Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0-20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323 ± 146 g m(-2) and TN stocks by 39 ± 10 g m(-2) at 0-20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65 ± 29 g OC m(-2) yr(-1) and 7.8 ± 2 g N m(-2) yr(-1). Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr(-1) of existing stocks) than OC (0.9% yr(-1)), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m(-2) yr(-1) accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6-13% of the estimated increase in net biome productivity.

Soil Organic Carbon and Total Nitrogen Gains in an Old Growth Deciduous Forest in Germany

PubMed Central

Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

2014-01-01

Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0–20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323±146 g m−2 and TN stocks by 39±10 g m−2 at 0–20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65±29 g OC m−2 yr−1 and 7.8±2 g N m−2 yr−1. Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr−1 of existing stocks) than OC (0.9% yr−1), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m−2 yr−1 accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6–13% of the estimated increase in net biome productivity. PMID:24586720

Effect of heavy metals on soil fungi

NASA Astrophysics Data System (ADS)

Sosak-Świderska, Bożena

2010-05-01

Fungi constitute a high proportion of the microbial biomass in soil.Being widespread in soil their large surface-to-volume ratio and high metabolic activity, fungi can contribute significantly to heavy metal dynamics in soil. At neutral pH heavy metals in soils tend to be immobilized to precipitation and/or absorption to cation exchange sites of clay minerals. In the acidic soils, metals are more mobile and enter food webs easier. Microbial production of acids and chelating agents can mobilize to toxic metals. Mobilization is often by uptake and intracellular accumulation of the heavy metlas, and in this way, the bioavailability of metals towards other organisms can be more reduced. Fungi were isolated from soils from Upper Silesia in Poland and belonged to widespread genera: Aspergillus, Cladosporium, Penicillium and Trichoderma. Fungi from different taxonomic groups differ greatly in their tolerance to heavy metals. This could be related to their wall structure and chemistry as well as biochemical and physiological characteristics of fungi. Localization of metals in fungal cells was studied using electron microscopy analysis. Metal biosorption in the cell wall can be complex as melanin granules. Fungal vacuoles have an important role in the regulation of the cytosolic concentration of metal ions, and may contribute to heavy metal tolerance.In polluted soils with heavy metals, fungal species composition can be changed and their physiological activity can be changed, too.

Weathering controls on mechanisms of carbon storage in grassland soils

USGS Publications Warehouse

Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

2004-01-01

On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought. Copyright 2004 by the American Geophysical Union.

Phosphorus Sorption Capacity of Gray Forest Soil as Dependent on Fertilization System

NASA Astrophysics Data System (ADS)

Rogova, O. B.; Kolobova, N. A.; Ivanov, A. L.

2018-05-01

In this paper, the results of the study of changes in the phosphorus sorption capacity of gray forest soils of Vladimir opolie under the impact of different fertilization systems are discussed. The quantitative parameters of the potential buffer capacity of soils for phosphorus (PBCP) and Langmuir sorption isotherms have been calculated. It is shown that the application of organic fertilizers results in a stronger decrease in PBCP than the application of mineral fertilizers. The portion of phosphorus of mineral compounds considerably increases, and the high content of available phosphates is maintained. In the variants with application of mineral phosphorus in combination with manure, the portions of organic and mineral phosphorus are at the level typical of unfertilized soils. The energy of phosphate bonds with the soil is minimal upon the application of a double rate of mineral phosphorus at the maximum capacity in relation to phosphate ions.

Factors affecting microbial 2,4,6-trinitrotoluene mineralization in contaminated soil

USGS Publications Warehouse

Bradley, P.M.; Chapelle, F.H.

1995-01-01

The influence of selected environmental factors on microbial TNT mineralization in soils collected from a TNT-contaminated site at Weldon Spring, MO, was examined using uniformly ring-labeled [14C]TNT. Microbial TNT mineralization was significantly inhibited by the addition of cellobiose and syringate. This response suggests that the indigenous microorganisms are capable of metabolizing TNT but preferentially utilize less recalcitrant substrates when available. The observed inhibition of TNT mineralization by TNT concentrations higher than 100 ??mol/kg of soil and by dry soil conditions suggests that toxic inhibition of microbial activity at high TNT concentrations and the periodic drying of these soils have contributed to the long-term persistence of TNT at Weldon Spring. In comparison to aerobic microcosms, mineralization was inhibited in anaerobic microcosms and in microcosms with a headspace of air amended with oxygen, suggesting that a mosaic of aerobic and anaerobic conditions may optimize TNT degradation at this site.

Differential controls on soil carbon density and mineralization among contrasting forest types in a temperate forest ecosystem.

PubMed

You, Ye-Ming; Wang, Juan; Sun, Xiao-Lu; Tang, Zuo-Xin; Zhou, Zhi-Yong; Sun, Osbert Jianxin

2016-03-01

Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models.

Differential controls on soil carbon density and mineralization among contrasting forest types in a temperate forest ecosystem

PubMed Central

You, Ye-Ming; Wang, Juan; Sun, Xiao-Lu; Tang, Zuo-Xin; Zhou, Zhi-Yong; Sun, Osbert Jianxin

2016-01-01

Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models. PMID:26925871

From where and how do plants and microbes get nitrogen? Revisiting paradigms of soil nitrogen availability

NASA Astrophysics Data System (ADS)

Grandy, S.

2017-12-01

Despite decades of research progress, soil biogeochemists are still debating in different ecosystems what pools and fluxes provide N to plants and microbes. Current concepts argue that N mineralization regulates the supply of N for plants and microorganisms, and is a `gatekeeper' for environmental N losses. The prevailing paradigm also argues that the chemistry of plant litter inputs (e.g. initial C:N ratio) primarily drives N mineralization rates, existing as a universal regulator of a switch between net N immobilization versus net N mineralization. However, decomposer community enzyme upregulation drives proteolysis, the exocellular first step in N mineralization; then, cellular carbon use efficiency and stoichiometry are internal microbial physiological processes driving ammonification rates. Further, N mineralization is only one of multiple, microbial-driven sequences in soils that regulate bioavailable N. Emerging evidence and new conceptual models from both the ecological and biogeoscience communities argue that while depolymerization is a critical first step, clay minerals may be an important and overlooked mediator of bioavailable N, and especially in the soil rhizosphere they are both a large source and sink for N. Mineral-associated organic matter (MAOM) can hold up to 20x more N than particulate fractions, is a rich reservoir of proteins, amino acids, and nucleic acids, and is mobilized by microbes and their interactions with plants. We use this and other emerging information to develop a new model of N availability in soils, highlighting: mineralization is strongly influenced by microbial physiological traits; the various steps in N mineralization have different drivers and can become decoupled; minerals are a strong sink and source for bioavailable N that is regulated by interactions between plants and microbial communities; and plants are a driving force in the soil N cycle for their ability to prime mineral N, and influence the structure and function of microbial communities. Plants and microbes are far from passive players in the cycling of N in soils, actively regulating N mineralization, interactions of bioavailable N with minerals, and ultimately plant N uptake.

Laboratory degradation studies of 14C-atrazine and -isoproturon in soil from sugarcane cultivated fields under Kenyan tropical conditions.

PubMed

Getenga, Z M; Dörfler, U; Schroll, R

2009-06-01

A study to compare the degradation rates of atrazine (6-chloro-N(2)-ethyl-N(4)-isopropyl-1,3,5-triazine-2,4-diammine) and isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] in soils from sugarcane fields with different practices of herbicides application was carried out. (14)C-atrazine was poorly mineralized to (14)CO(2) (1.10% +/- 0.22%) after 139 days of incubation in soil without previous exposure to atrazine. In the same soil also with no previous isoproturon exposure isoproturon was mineralized to (14)CO(2) by 7.70% +/- 0.94%. Atrazine mineralization after 98 days was 13.4% +/- 0.30% in soil which discontinued the use of atrazine in 1997 while it was 89.9% +/- 1.23% in soil in which atrazine is currently being used. The isoproturon mineralization values were 7.24% +/- 0.85% and 22.97% +/- 0.96% in soil which discontinued atrazine and soil currently using atrazine, respectively.

Results of mineral, chemical, and sulfate isotopic analyses of water, soil, rocks, and soil extracts from the Pariette Draw Watershed, Uinta Basin, Utah

USGS Publications Warehouse

Morrison, Jean M.; Tuttle, Michele L.W.; Fahy, Juli W.

2015-08-06

The goal of this study was to establish a process-based understanding of salt, Se, and B behavior to address whether these contaminants can be better managed, or if uncontrollable natural processes will overwhelm any attempts to bring Pariette Draw into compliance with respect to recently established total maximum daily limits (TMDLs). We collected data to refine our knowledge about the role of rock weathering and soil formation in the transport and storage of salt in the watershed and to show how salt is cycled under irrigated and natural conditions. Our approach was to sample rock, soils, and sediment on irrigated and natural terrain for mineralogical analysis to determine the residence of salt and associated Se and B, classify minerals as primary (related to rock formation) or secondary weathering products, and characterize mineral dissolution kinetics. Mineral and chemical analyses and selective extractions of rocks and soils provide useful information in understanding solute movement and mineral dissolution/ formation. The resulting data are critical in determining residence of salt, Se, and B in weathered rock and soil and understanding the mobility during water-rock-soil interactions. This report summarizes our methods for sample and data collection and tabulates the mineral, chemical, and isotopic data collected.

Role of root exudates in dissolution of Cd containing iron oxides

NASA Astrophysics Data System (ADS)

Rosenfeld, C.; Martinez, C. E.

2011-12-01

Dissolved organic matter (DOM) in the rhizosphere contains organic acids, amino acids and more complex organic molecules that can substantially impact the solubility of soil solid phases. Plant roots and soil microorganisms contribute a large fraction of these organic compounds to DOM, potentially accelerating the transfer of solid phase elements into solution. In highly contaminated soils, heavy metals such as Cd are commonly found coprecipitated with common minerals (e.g. iron oxides). Introducing or changing vegetation on these contaminated soils may increase DOM levels in the soil pore fluids and thus enhance the biological and chemical weathering of soil minerals. Here, we investigate the role of root exudates on mineral dissolution and Cd mobility in contaminated soils. We hypothesize that plant exudates containing nitrogen and sulfur functional groups will dissolve Cd-containing mineral phases to a greater extent than exudates containing only oxygen functional groups, resulting in higher Cd concentrations in solution. Two different iron oxide mineral phases were utilized in a laboratory-scale model study system investigating the effects of low molecular weight, oxygen-, nitrogen-, and sulfur-containing organic compounds on mineral dissolution. Goethite (α-FeOOH) was synthesized in the laboratory with 0, 2.4, 5, and 100 theoretical mol% Cd, and franklinite (ZnFe2O4) was prepared with 0, 10, and 25 theoretical mol% Cd. Phase identity of all minerals was verified with X-ray diffraction (XRD). All minerals were reacted with 0.01 mM solutions containing one of four different organic ligands (oxalic acid, citric acid, histidine or cysteine) and aliquots of these solutions were sampled periodically over 40 days. Results from solution samples suggest that oxalic acid, citric acid, and histidine consistently increase mineral dissolution relative to the control (no organic compound present) while cysteine consistently inhibits dissolution relative to the control in all minerals. Increasing Cd substitution in the franklinite resulted in increased release of Fe and Zn to solution in the presence of these organic compounds, while increasing Cd substitution in the goethite generally limited Fe release to solution. In the case of cysteine, sulfur concentrations in solution decrease over time in the presence of Cd-containing minerals, indicating strong binding of the cysteine compound to the mineral surface, inhibiting Cd dissolution from the minerals. Our work indicates that amino acids present in biological soil exudates, in addition to organic acids, may have substantial impacts on iron oxide dissolution in soils, altering the availability of both bioessential (e.g., Fe and Zn) and non-essential, or potentially toxic, (e.g., Cd) elements.

Anthropogenic acidification effects in primeval forests in the Transcarpathian Mts., western Ukraine.

PubMed

Oulehle, F; Hleb, R; Houska, J; Samonil, P; Hofmeister, J; Hruska, J

2010-01-15

The precipitation chemistry, deposition, nutrient pools and composition of soils and soil water, as well as an estimate of historical deposition of sulphur (S) and inorganic nitrogen (N) for the period 1860-2008, were determined in primeval deciduous and coniferous forests at the sites Javornik and Pop Ivan, respectively. Measured S throughfall inputs of 10 kg ha(-1)year(-1) in 2008 were similar to those estimated for the period 1900-1950 at both sites. The highest estimated S inputs were in the 1980s. Measured bulk deposition of N in 2008 was lower at Pop Ivan (5.6 kg ha(-1)year(-1)) compared to Javornik (12 kg ha(-1)year(-1)). Significantly lower NO(3) deposition was both estimated and measured at Pop Ivan. Higher soil base cation concentrations were observed at well-buffered Javornik underlain by flysch (Ca pool of 2046 kg ha(-1) and base saturation of 29%) compared to Pop Ivan underlain by crystalline schist (Ca pool of 186 kg ha(-1) and base saturation of 6.5%). The soil pool of organic carbon (C) was higher at Pop Ivan (212 t ha(-1)) compared to Javornik (127 t ha(-1)). The C concentration was positively correlated with organic N in the soil (p<0.001) at both sites, but the mass average C/N ratio in the forest floor was lower at Javornik (22) than at Pop Ivan (26). High N leaching of 17 kg ha(-1)year(-1) at the 90 cm depth was measured in the soil water at Javornik, suggesting high mineralization and nitrification rates in old growth deciduous forests in the area. Despite relatively low Al concentrations in the soil water, a low soil water Bc/Al ratio (0.9) (Bc=Ca+Mg+K) was found in the upper mineral soil at Pop Ivan. This suggests that the spruce forest ecosystems in the area are vulnerable to anthropogenic acidification and to the adverse effects of Al on forest root systems. Copyright 2009 Elsevier B.V. All rights reserved.

Soil abandonment in artificial soil terraces in marginal areas. Preliminary results of a case of water shortage effect in soils from Sultanate of Oman.

NASA Astrophysics Data System (ADS)

Saadi, Sara Kalifah Al; Kindi, Samaya Salim Al; Pracejus, Bernhard; Moraetis, Daniel

2016-04-01

Soil abandonment is taking place in marginal land areas in Sultanate of Oman. Artificial soil terraces in high elevation rocky mountainous areas left without agricultural activities due to water shortage. Soil terraces have been established approximately 700 years ago and constitute a significant part of the Oman cultural and natural heritage. The present study investigates the soil state in those areas and seeks the possible reasons for the land abandonment. Questionnaires were prepared to interview the opinion of the local people. In addition, meteorological data were gathered to analyze the rain patterns in the area and most importantly, six soil profiles in two different areas in marginal rocky areas of Oman were sampled. The soils are in artificial terraces in Wijma and Hadash villages with elevation of 1247 and 1469 m respectively at mountainous slopes of 20 to 45 degrees. Most of the land was abandoned the last 20 years, while one terrace had agriculture activity 3 years ago. The questioners and interviews showed that water shortage was the reason of land abandonment. The rain patterns show a reduction of annual precipitation at least the last 10 years of available metrological data in the area. The total soil depth in the six soil profiles was between 33 to 70 cm. The main horizons include AC and C and there was a characteristic hard soil horizon in most of the soil profiles with accumulation of carbonate minerals (caliche). The soil pH was mainly alkaline between 7.5 to 8.1 and the electrical conductivity range between 42 to 859 μS/cm. A horizonization in electrical conductivity showed more dissolved solids in lower horizons compare to the upper 10 cm of the soil and this was coinciding with the hard layers in lower soil profiles. It appeared that several hundred years (or maximum 1000 years) old soils showed the development of hard soil layers which are characteristic in arid areas. The upper soil layers showed low conductivity probably due to surface deflation and desert pavement development after the terraces abandonment. The water shortage has probably affected severely the soil characteristics (pavement development and strong wind erosion) and it has enforced the locals to search for alternative domestic income towards lower land areas. Hard soil horizons on those areas showed to have developed in relatively short time after soil terraces construction.

Fifteen-year patterns of soil carbon and nitrogen following biomass harvesting

USGS Publications Warehouse

Kurth, Valerie J.; D'Amato, Anthony W.; Palik, Brian J.; Bradford, John B.

2014-01-01

The substitution of forest-derived woody biofuels for fossil fuel energy has garnered increasing attention in recent years, but information regarding the mid- and long-term effects on soil productivity is limited. We investigated 15-yr temporal trends in forest floor and mineral soil (0–30 cm) C and N pools in response to organic matter removal treatments (OMR; stem-only harvest, SOH; whole-tree harvest, WTH; and whole-tree plus forest floor removal, FFR) at three edaphically distinct aspen (Populus tremuloides Michx. and P. grandidentata Michx.) forests in the Great Lakes region. The OMR and temporal effects were generally site specific, and both were most evident in the forest floor and combined profile (mineral soil and forest floor) compared with the mineral soil alone. Forest floor and combined profile C and N pools were generally similar in the SOH and WTH treatments, suggesting that slash retention has little impact on soil C and N in this time frame. Temporal changes in C and N at one of the three sites were consistent with patterns documented following exotic earthworm invasion, but mineral soil pools at the other two sites were stable over time. Power analyses demonstrated that significant effects were more likely to be detected for temporal differences than the effects of OMR and in the combined profile than in the mineral soil. Our findings are consistent with previous work demonstrating that OMR effects on soil C and N pools are site specific and more apparent in the forest floor than the mineral soil.

Modeling the influence of organic acids on soil weathering

NASA Astrophysics Data System (ADS)

Lawrence, Corey; Harden, Jennifer; Maher, Kate

2014-08-01

Biological inputs and organic matter cycling have long been regarded as important factors in the physical and chemical development of soils. In particular, the extent to which low molecular weight organic acids, such as oxalate, influence geochemical reactions has been widely studied. Although the effects of organic acids are diverse, there is strong evidence that organic acids accelerate the dissolution of some minerals. However, the influence of organic acids at the field-scale and over the timescales of soil development has not been evaluated in detail. In this study, a reactive-transport model of soil chemical weathering and pedogenic development was used to quantify the extent to which organic acid cycling controls mineral dissolution rates and long-term patterns of chemical weathering. Specifically, oxalic acid was added to simulations of soil development to investigate a well-studied chronosequence of soils near Santa Cruz, CA. The model formulation includes organic acid input, transport, decomposition, organic-metal aqueous complexation and mineral surface complexation in various combinations. Results suggest that although organic acid reactions accelerate mineral dissolution rates near the soil surface, the net response is an overall decrease in chemical weathering. Model results demonstrate the importance of organic acid input concentrations, fluid flow, decomposition and secondary mineral precipitation rates on the evolution of mineral weathering fronts. In particular, model soil profile evolution is sensitive to kaolinite precipitation and oxalate decomposition rates. The soil profile-scale modeling presented here provides insights into the influence of organic carbon cycling on soil weathering and pedogenesis and supports the need for further field-scale measurements of the flux and speciation of reactive organic compounds.

Modeling the influence of organic acids on soil weathering

USGS Publications Warehouse

Lawrence, Corey R.; Harden, Jennifer W.; Maher, Kate

2014-01-01

Biological inputs and organic matter cycling have long been regarded as important factors in the physical and chemical development of soils. In particular, the extent to which low molecular weight organic acids, such as oxalate, influence geochemical reactions has been widely studied. Although the effects of organic acids are diverse, there is strong evidence that organic acids accelerate the dissolution of some minerals. However, the influence of organic acids at the field-scale and over the timescales of soil development has not been evaluated in detail. In this study, a reactive-transport model of soil chemical weathering and pedogenic development was used to quantify the extent to which organic acid cycling controls mineral dissolution rates and long-term patterns of chemical weathering. Specifically, oxalic acid was added to simulations of soil development to investigate a well-studied chronosequence of soils near Santa Cruz, CA. The model formulation includes organic acid input, transport, decomposition, organic-metal aqueous complexation and mineral surface complexation in various combinations. Results suggest that although organic acid reactions accelerate mineral dissolution rates near the soil surface, the net response is an overall decrease in chemical weathering. Model results demonstrate the importance of organic acid input concentrations, fluid flow, decomposition and secondary mineral precipitation rates on the evolution of mineral weathering fronts. In particular, model soil profile evolution is sensitive to kaolinite precipitation and oxalate decomposition rates. The soil profile-scale modeling presented here provides insights into the influence of organic carbon cycling on soil weathering and pedogenesis and supports the need for further field-scale measurements of the flux and speciation of reactive organic compounds.

To what extent clay mineralogy affects soil aggregation? Consequences for soil organic matter stabilization

NASA Astrophysics Data System (ADS)

Fernandez-Ugalde, O.; Barré, P.; Hubert, F.; Virto, I.; Chenu, C.; Ferrage, E.; Caner, L.

2012-12-01

Aggregation is a key process for soil functioning as it influences C storage, vulnerability to erosion and water holding capacity. While the influence of soil organic C on aggregation has been documented, much less is known about the role of soil mineralogy. Soils usually contain a mixture of clay minerals with contrasted surface properties, which should result on different abilities of clay minerals to aggregation. We took advantage of the intrinsic mineral heterogeneity of a temperate Luvisol to compare the role of clay minerals (illite, smectite, kaolinite, and mixed-layer illite-smectite) in aggregation. In a first step, grassland and tilled soil samples were fractionated in water in aggregate-size classes according to the hierarchical model of aggregation (Tisdall and Oades, 1982). Clay mineralogy and organic C in the aggregate-size classes were analyzed. The results showed that interstratified minerals containing swelling phases accumulated in aggregated fractions (>2 μm) compared to free clay fractions (<2 μm) in the two land-uses. The accumulation increased from large macro-aggregates (>500 μm) to micro-aggregates (50-250 μm). C concentration and C/N ratio followed the opposite trend. These results constitute a clay mineral-based evidence for the hierarchical model of aggregation, which postulates an increasing importance of the reactivity of clay minerals in the formation of micro-aggregates compared to larger aggregates. In the latter aggregates, formation relies on the physical enmeshment of particles by fungal hyphae, and root and microbial exudates. In a second step, micro-aggregates from the tilled soil samples were submitted to increasingly disaggregating treatments by sonication to evaluate the link between their water stability and clay mineralogy. Micro-aggregates with increasing stability showed an increase of interstratified minerals containing swelling phases and C concentration for low intensities of disaggregation (from 0 to 5 J mL-1). This suggests that swelling phases promote their stability. Swelling phases and organic C decreased for greater intensities of disaggregation. These results and the SEM images taken at different disaggregation intensities indicate that when increasing disaggregation intensity above 5 J mL-1, the recovered material consists on sand particles covered by physical coatings of illite and kaolinite. Our results show that different clay minerals have different contribution to soil aggregation. Swelling phases are especially important for water-stable aggregates formation, whereas illite and kaolinite can either contribute to aggregation or been coated to sand grains in "mineral aggregates", without porosity and organic C protection capability. In conclusion, soils with large proportion of swelling clay minerals have greater potential for carbon storage by occlusion in aggregates and greater resistance to erosion. Tisdall JM, Oades JM (1982) Organic matter and water-stable aggregates in soils. J Soil Sci 62: 141-163.

Soil ingestion by dairy cattle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darwin, R.

1990-02-15

Ingested soil may be a source of minerals to grazing cattle; it may also be a source of radionuclides, heavy metals, and organic toxins. The importance of soil ingestion in the milk pathway depends on the amount of soil ingested, the ratio of the mineral concentration in soil to that in herbage, and the ability of the cattle to solubilize and absorb the soil-derived minerals. The amount of soil ingested by cattle on pasture, in turn, depends upon the stocking level, the quantity of forage available, and the soil ingesting propensity of individual cows. The objective of this note ismore » to summarize some of the information about soil ingestion by dairy cattle and to suggest methods for incorporating soil ingestion into the Hanford Environmental Dose Reconstruction (HEDR) Phase I milk model. 5 refs., 4 tabs.« less

Metal oxides, clay minerals and charcoal determine the composition of microbial communities in matured artificial soils and their response to phenanthrene.

PubMed

Babin, Doreen; Ding, Guo-Chun; Pronk, Geertje Johanna; Heister, Katja; Kögel-Knabner, Ingrid; Smalla, Kornelia

2013-10-01

Microbial communities in soil reside in a highly heterogeneous habitat where diverse mineral surfaces, complex organic matter and microorganisms interact with each other. This study aimed to elucidate the long-term effect of the soil mineral composition and charcoal on the microbial community composition established in matured artificial soils and their response to phenanthrene. One year after adding sterile manure to different artificial soils and inoculating microorganisms from a Cambisol, the matured soils were spiked with phenanthrene or not and incubated for another 70 days. 16S rRNA gene and internal transcribed spacer fragments amplified from total community DNA were analyzed by denaturing gradient gel electrophoresis. Metal oxides and clay minerals and to a lesser extent charcoal influenced the microbial community composition. Changes in the bacterial community composition in response to phenanthrene differed depending on the mineral composition and presence of charcoal, while no shifts in the fungal community composition were observed. The abundance of ring-hydroxylating dioxygenase genes was increased in phenanthrene-spiked soils except for charcoal-containing soils. Here we show that the formation of biogeochemical interfaces in soil is an ongoing process and that different properties present in artificial soils influenced the bacterial response to the phenanthrene spike. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Biogeochemistry of a temperate forest nitrogen gradient

USGS Publications Warehouse

Perakis, Steven S.; Sinkhorn, Emily R.

2011-01-01

Wide natural gradients of soil nitrogen (N) can be used to examine fundamental relationships between plant–soil–microbial N cycling and hydrologic N loss, and to test N-saturation theory as a general framework for understanding ecosystem N dynamics. We characterized plant production, N uptake and return in litterfall, soil gross and net N mineralization rates, and hydrologic N losses of nine Douglas-fir (Pseudotsuga menziesii) forests across a wide soil N gradient in the Oregon Coast Range (USA). Surface mineral soil N (0–10 cm) ranged nearly three-fold from 0.29% to 0.78% N, and in contrast to predictions of N-saturation theory, was linearly related to 10-fold variation in net N mineralization, from 8 to 82 kg N·ha−1·yr−1. Net N mineralization was unrelated to soil C:N, soil texture, precipitation, and temperature differences among sites. Net nitrification was negatively related to soil pH, and accounted for −1·yr−1. Aboveground net primary production per unit net N mineralization varied inversely with soil N, suggesting progressive saturation of plant N demands at high soil N. Hydrologic N losses were dominated by dissolved organic N at low-N sites, with increased nitrate loss causing a shift to dominance by nitrate at high-N sites, particularly where net nitrification exceeded plant N demands. With the exception of N mineralization patterns, our results broadly support the application of the N-saturation model developed from studies of anthropogenic N deposition to understand N cycling and saturation of plant and microbial sinks along natural soil N gradients. This convergence of behavior in unpolluted and polluted forest N cycles suggests that where future reductions in deposition to polluted sites do occur, symptoms of N saturation are most likely to persist where soil N content remains elevated.

Linkages between grazing history and herbivore exclusion on decomposition rates in mineral soils of subalpine grasslands

Treesearch

Alan G. Haynes; Martin Schutz; Nina Buchmann; Deborah S. Page-Dumroese; Matt D. Busse; Anita C. Risch

2014-01-01

Herbivore-driven changes to soil properties can influence the decomposition rate of organic material and therefore soil carbon cycling within grassland ecosystems. We investigated how aboveground foraging mammalian and invertebrate herbivores affect mineral soil decomposition rates and associated soil properties in two subalpine vegetation types (shortgrass and tall-...

Using soil temperature and moisture to predict forest soil nitrogen mineralization

Treesearch

Jennifer D. Knoepp; Wayne T. Swank

2002-01-01

Due to the importance of N in forest productivity ecosystem and nutrient cycling research often includes measurement of soil N transformation rates as indices of potential availability and ecosystem losses of N. We examined the feasibility of using soil temperature and moisture content to predict soil N mineralization rates (Nmin) at the Coweeta Hydrologic Laboratory...

Characteristics of streams and aquifers and processes affecting the salinity of water in the upper Colorado River basin, Texas

USGS Publications Warehouse

Slade, R.M.; Buszka, P.M.

1994-01-01

The chemical characteristics of the saline water in streams and shallow aquifers in the study area were compared to characteristics of water that would result from the probable processes affecting the salinity of water, such as evapotranspiration, mineral dissolution, and mixing of water from streams and shallow-aquifer water with brines from deep aquifers. Dissolution of halite or mixing with deep-aquifer water was the most common cause of increased salinity in 48.0 percent of 77 water samples from shallow aquifers, as classified using salt-norm analysis; the second most common cause was the weathering and dissolution of sulfur-bearing minerals. Mixing with water from soil-mineral dissolution was classified as the principal source of chloride in 28.4 percent of 67 water samples from shallow aquifers with nitrate determinations. Trace-species/chloride ratios indicated that mixing with water from deep aquifers in rocks of the Pennsylvanian System was the principal source of chloride in 24.4 percent of 45 shallow-aquifer samples lacking nitrate determinations.

Response of hydrolytic enzyme activities and nitrogen mineralization to fertilizer and organic matter application in subtropical paddy soils

NASA Astrophysics Data System (ADS)

Kader, Mohammed Abdul; Yeasmin, Sabina; Akter, Masuda; Sleutel, Steven

2016-04-01

Driving controllers of nitrogen (N) mineralization in paddy soils, especially under anaerobic soil conditions, remain elusive. The influence of exogenous organic matter (OM) and fertilizer application on the activities of five relevant enzymes (β-glucosaminidase, β-glucosidase, L-glutaminase, urease and arylamidase) was measured in two long-term field experiments. One 18-years field experiment was established on a weathered terrace soil with a rice-wheat crop rotation at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) having five OM treatments combined with two mineral N fertilizer levels. Another 30-years experiment was established on a young floodplain soil with rice-rice crop rotation at the Bangladesh Agricultural University (BAU) having eight mineral fertilizer treatments combined with organic manure. At BSMRAU, N fertilizer and OM amendments significantly increased all enzyme activities, suggesting them to be primarily determined by substrate availability. At BAU, non-responsiveness of β-glucosidase activity suggested little effect of the studied fertilizer and OM amendments on general soil microbial activity. Notwithstanding probably equal microbial demand for N, β-glucosaminidase and L-glutaminase activities differed significantly among the treatments (P>0.05) and followed strikingly opposite trends and correlations with soil organic N mineralization. So enzymatic pathways to acquire N differed by treatment at BAU, indicating differences in soil N quality and bio-availability. L-glutaminase activity was significantly positively correlated to the aerobic and anaerobic N mineralization rates at both field experiments. Combined with negative correlations between β-glucosaminidase activity and N mineralization rates, it appears that terminal amino acid NH2 hydrolysis was a rate-limiting step for soil N mineralization at BAU. Future investigations with joint quantification of polyphenol accumulation and binding of N, alongside an array of extracellular enzymes including oxidases and peroxidases for (poly)phenols and hydrolases for N-compounds, would enable verifying the hypothesized binding and stabilization of N onto accumulating polyphenols at BAU site under SOM accumulating management.

Organomineral Complexation at the Nanoscale: Iron Speciation and Soil Carbon Stabilization

NASA Astrophysics Data System (ADS)

Coward, E.; Thompson, A.; Plante, A. F.

2016-12-01

Much of the uncertainty in the biogeochemical behavior of soil carbon (C) in tropical ecosystems derives from an incomplete understanding of soil C stabilization processes. The 2:1 phyllosilicate clays often associated with temperate organomineral complexation are largely absent in tropical soils due to extensive weathering. In contrast, these soils contain an abundance of Fe- and Al-containing short-range-order (SRO) mineral phases capable of C stabilization through sorption or co-precipitation, largely enabled by high specific surface area (SSA). SRO-mediated organomineral associations may thus prove a critical, yet matrix-selective, driver of the long-term C stabilization capacity observed in tropical soils. Characterizing the interactions between inherently heterogeneous organic matter and amorphous mineralogy presses the limits of current analytical techniques. This work pairs inorganic selective dissolution with high-resolution assessment of Fe speciation to determine the contribution of extracted mineral phases to the mineral matrix, and to C stabilization capacity. Surface (0-20 cm) samples were taken from 20 quantitative soil pits within the Luquillo Critical Zone Observatory in northeast Puerto Rico stratified across granodioritic and volcaniclastic parent materials. 57Fe-Mössbauer spectroscopy (MBS) and x-ray diffraction (XRD) before and after Fe-SOM extraction were used to assess changes in the mineralogical matrix associated with SOM dissolution, while N2-BET sorption was used to determine the contributions of the extractable phases to SSA. Results indicate (1) selective extraction of soil C produces significant shifts in Fe phase distribution, (2) SRO minerals contribute substantially to SSA, and (3) SRO minerals appear protected by more crystalline phases via physical mechanisms, rather than dissolution-dependent chemical bonds. This nanoscale characterization of Fe-C complexes thus provides evidence for both anticipated mineral-organic and unexpected mineral-mineral associations, which may dynamically impact the temporal fate of tropical soil C.

Differential Adsorption of Occluded and Nonoccluded Insect-Pathogenic Viruses to Soil-Forming Minerals

PubMed Central

Christian, Peter D.; Richards, Andrew R.; Williams, Trevor

2006-01-01

Soil represents the principal environmental reservoir of many insect-pathogenic viruses. We compared the adsorption and infectivity of one occluded and two nonoccluded viruses, Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) (Baculoviridae), Cricket paralysis virus (CrPV) (Dicistroviridae), and Invertebrate iridescent virus 6 (IIV-6) (Iridoviridae), respectively, in mixtures with a selection of soil-forming minerals. The relative infective titers of HaSNPV and CrPV were unchanged or slightly reduced in the presence of different minerals compared to their titers in the absence of the mineral. In contrast, the infective titer of IIV-6 varied according to the mineral being tested. In adsorption studies, over 98% of HaSNPV occlusion bodies were adsorbed by all the minerals, and a particularly high affinity was observed with ferric oxide, attapulgite, and kaolinite. In contrast, the adsorption of CrPV and IIV-6 differed markedly with mineral type, with low affinity to bentonites and high affinity to ferric oxide and kaolinite. We conclude that interactions between soil-forming minerals and insect viruses appear to be most important in nucleopolyhedroviruses, followed by invertebrate iridescent viruses, and least important in CrPV, which may reflect the ecology of these pathogens. Moreover, soils with a high content of iron oxides or kaolinite would likely represent highly effective reservoirs for insect-pathogenic viruses. PMID:16820456

Effect of sulfate and carbonate minerals on particle-size distributions in arid soils

USGS Publications Warehouse

Goossens, Dirk; Buck, Brenda J.; Teng, Yuazxin; Robins, Colin; Goldstein, Harland L.

2014-01-01

Arid soils pose unique problems during measurement and interpretation of particle-size distributions (PSDs) because they often contain high concentrations of water-soluble salts. This study investigates the effects of sulfate and carbonate minerals on grain-size analysis by comparing analyses in water, in which the minerals dissolve, and isopropanol (IPA), in which they do not. The presence of gypsum, in particular, substantially affects particle-size analysis once the concentration of gypsum in the sample exceeds the mineral’s solubility threshold. For smaller concentrations particle-size results are unaffected. This is because at concentrations above the solubility threshold fine particles cement together or bind to coarser particles or aggregates already present in the sample, or soluble mineral coatings enlarge grains. Formation of discrete crystallites exacerbates the problem. When soluble minerals are dissolved the original, insoluble grains will become partly or entirely liberated. Thus, removing soluble minerals will result in an increase in measured fine particles. Distortion of particle-size analysis is larger for sulfate minerals than for carbonate minerals because of the much higher solubility in water of the former. When possible, arid soils should be analyzed using a liquid in which the mineral grains do not dissolve, such as IPA, because the results will more accurately reflect the PSD under most arid soil field conditions. This is especially important when interpreting soil and environmental processes affected by particle size.

Phosphorus minerals in tonstein; coal seam 405 at Sośnica-Makoszowy coal mine, Upper Silesia, southern Poland

NASA Astrophysics Data System (ADS)

Kokowska-Pawłowska, Magdalena; Nowak, Jacek

2013-06-01

Kokowska-Pawłowska, M. and Nowak, J. 2013. Phosphorus minerals in tonstein; coal seam 405 at Sośnica- Makoszowy coal mine, Upper Silesia, southern Poland. Acta Geologica Polonica, 63 (2), 271-281. Warszawa. The paper presents results of research on tonstein, which constitutes an interburden in coal seam 405 at the Sośnica- Makoszowy coal mine, Makoszowy field (mining level 600 m), Upper Silesia, southern Poland. The mineral and chemical compositions of the tonstein differ from the typical compositions described earlier for tonsteins from Upper Silesia Coal Basin area. Additionally, minerals present in the tonsteins include kaolinite, quartz, kaolinitised biotite and feldspars. The presence of the phosphatic minerals apatite and goyazite has been recognized. The presence of gorceixite and crandallite is also possible. The contents of CaO (5.66 wt%) and P2O5 (6.2 wt%) are remarkably high. Analysis of selected trace elements demonstrated high contents of Sr (4937 ppm) and Ba (4300 ppm), related to the phosphatic minerals. On the basis of mineral composition the tonstein has been identified as a crystalline tonstein, transitional to a multiplied one.

Effects of forest conversion on soil microbial communities depend on soil layer on the eastern Tibetan Plateau of China.

PubMed

He, Ruoyang; Yang, Kaijun; Li, Zhijie; Schädler, Martin; Yang, Wanqin; Wu, Fuzhong; Tan, Bo; Zhang, Li; Xu, Zhenfeng

2017-01-01

Forest land-use changes have long been suggested to profoundly affect soil microbial communities. However, how forest type conversion influences soil microbial properties remains unclear in Tibetan boreal forests. The aim of this study was to explore variations of soil microbial profiles in the surface organic layer and subsurface mineral soil among three contrasting forests (natural coniferous forest, NF; secondary birch forest, SF and spruce plantation, PT). Soil microbial biomass, activity and community structure of the two layers were investigated by chloroform fumigation, substrate respiration and phospholipid fatty acid analysis (PLFA), respectively. In the organic layer, both NF and SF exhibited higher soil nutrient levels (carbon, nitrogen and phosphorus), microbial biomass carbon and nitrogen, microbial respiration, PLFA contents as compared to PT. However, the measured parameters in the mineral soils often did not differ following forest type conversion. Irrespective of forest types, the microbial indexes generally were greater in the organic layer than in the mineral soil. PLFAs biomarkers were significantly correlated with soil substrate pools. Taken together, forest land-use change remarkably altered microbial community in the organic layer but often did not affect them in the mineral soil. The microbial responses to forest land-use change depend on soil layer, with organic horizons being more sensitive to forest conversion.

Differential effects of lichens, mosses and grasses on respiration and nitrogen mineralization in soils of the New Jersey Pinelands.

PubMed

Sedia, Ekaterina G; Ehrenfeld, Joan G

2005-06-01

In the New Jersey Pinelands, severely disturbed areas often do not undergo a rapid succession to forest; rather, a patchy cover of lichens, mosses and grasses persists for decades. We hypothesized that these plant covers affect soil microbial processes in different ways, and that these effects may alter the successional dynamics of the patches. We predicted that the moss and grass covers stimulate soil microbial activity, whereas lichens inhibit it, which may in turn inhibit succession. We collected soil cores from beneath each type of cover plus bare soil within two types of highly disturbed areas--sites subjected to hot wildfires, and areas mined for sand. Organic matter (OM) content, soil respiration and potential N mineralization were measured in the cores. Soils under mosses were similar to those under grasses; they accumulated more OM and produced more mineral N, predominantly in the form of ammonium, than either the bare soils or the soils beneath lichens. Mineralization under lichens, like that of the bare soils but unlike the soils beneath mosses or grasses, was dominated by net nitrification. These patterns were reproduced in experimentally transplanted moss and lichen mats. Mosses appear to create high-nutrient microsites via high rates of OM accumulation and production of ammonium, whereas lichens maintain low-nutrient patches similar to bare soil via low OM accumulation rates and production of mineral N predominantly in the mobile nitrate form. These differences in soil properties may explain the lack of vascular plant invasion in lichen mats, in contrast to the moss-dominated areas.

Mineral oil residues in soil and apple under temperate conditions of Kashmir, India.

PubMed

Ahmad, Malik Mukhtar; Wani, Ashraf Alam; Sofi, Mubashir; Ara, Ishrat

2018-03-09

The study was undertaken to ascertain the persistence of Orchol-13, a mineral oil used against insect pests of horticultural fruit crops in soil and apple following the dormant and summer applications of 2 and 0.75% respectively. Soil samples were collected during dormant, while as both soil and apple samples were collected during summer season. Samples were collected at 0, 1, 3, and 5 days post treatment in both the seasons. Average recoveries of paraffinic constituents (which constitute about 60% of mineral oils by composition) from soil and apple at 1 μg ml -1 spiking level were found to be 74.18 and 76.81% respectively. The final quantification of paraffinic constituents was performed on gas chromatograph equipped with flame ionization detector (GC-FID). No paraffinic constituents of mineral oil could be detected in soil and apple at 0 day post treatment in both the seasons.

Influence of long-term fertilization on soil physicochemical properties in a brown soil

NASA Astrophysics Data System (ADS)

Li, Dongdong; Luo, Peiyu; Han, Xiaori; Yang, Jinfeng

2018-01-01

This study aims to explore the influence on soil physicochemical properties under a 38-y long-term fertilization in a brown soil. Soil samples (0-20 cm)were taken from the six treatments of the long-term fertilization trial in October 2016:no fertilizer (CK), N1(mineral nitrogen fertilizer), N1P (mineral nitrogen and phosphate fertilizer), N1PK (mineral nitrogen, phosphate and potassic fertilizer), pig manure (M2), M2N1P (pig manure, mineral nitrogen and phosphate fertilizer).The results showed thatthe long-term application of chemical fertilizers reduced soil pH value, while the application of organic fertilizers increased pH value. Fertilization significantly increased the content of AHN, TN and SOM. Compared with the CK treatment and chemical fertilizer treatments, organic fertilizer treatments significantly increased the content of AP and TP. The content of AK and TK were no significant difference in different treatment.

Mineral protection of soil carbon counteracted by root exudates [Root exudates counteract mineral control on soil carbon turnover

DOE PAGES

Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; ...

2015-03-30

Multiple lines of existing evidence suggest that climate change enhances root exudation of organic compounds into soils. Recent experimental studies show that increased exudate inputs may cause a net loss of soil carbon. This stimulation of microbial carbon mineralization (‘priming’) is commonly rationalized by the assumption that exudates provide a readily bioavailable supply of energy for the decomposition of native soil carbon (co-metabolism). Here we show that an alternate mechanism can cause carbon loss of equal or greater magnitude. We find that a common root exudate, oxalic acid, promotes carbon loss by liberating organic compounds from protective associations with minerals.more » By enhancing microbial access to previously mineral-protected compounds, this indirect mechanism accelerated carbon loss more than simply increasing the supply of energetically more favourable substrates. Lastly, our results provide insights into the coupled biotic–abiotic mechanisms underlying the ‘priming’ phenomenon and challenge the assumption that mineral-associated carbon is protected from microbial cycling over millennial timescales.« less

Predicting the mineral composition of dust aerosols – Part 1: Representing key processes

DOE PAGES

Perlwitz, J. P.; Perez Garcia-Pando, C.; Miller, R. L.

2015-10-21

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accountsmore » for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. Finally, a limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.« less

Carbon input increases microbial nitrogen demand, but not microbial nitrogen mining in boreal forest soils

NASA Astrophysics Data System (ADS)

Wild, Birgit; Alaei, Saeed; Bengtson, Per; Bodé, Samuel; Boeckx, Pascal; Schnecker, Jörg; Mayerhofer, Werner; Rütting, Tobias

2016-04-01

Plant primary production at mid and high latitudes is often limited by low soil N availability. It has been hypothesized that plants can indirectly increase soil N availability via root exudation, i.e., via the release of easily degradable organic compounds such as sugars into the soil. These compounds can stimulate microbial activity and extracellular enzyme synthesis, and thus promote soil organic matter (SOM) decomposition ("priming effect"). Even more, increased C availability in the rhizosphere might specifically stimulate the synthesis of enzymes targeting N-rich polymers such as proteins that store most of the soil N, but are too large for immediate uptake ("N mining"). This effect might be particularly important in boreal forests, where plants often maintain high primary production in spite of low soil N availability. We here tested the hypothesis that increased C availability promotes protein depolymerization, and thus soil N availability. In a laboratory incubation experiment, we added 13C-labeled glucose to a range of soil samples derived from boreal forests across Sweden, and monitored the release of CO2 by C mineralization, distinguishing between CO2 from the added glucose and from the native, unlabeled soil organic C (SOC). Using a set of 15N pool dilution assays, we further measured gross rates of protein depolymerization (the breakdown of proteins into amino acids) and N mineralization (the microbial release of excess N as ammonium). Comparing unamended control samples, we found a high variability in C and N mineralization rates, even when normalized by SOC content. Both C and N mineralization were significantly correlated to SOM C/N ratios, with high C mineralization at high C/N and high N mineralization at low C/N, suggesting that microorganisms adjusted C and N mineralization rates to the C/N ratio of their substrate and released C or N that was in excess. The addition of glucose significantly stimulated the mineralization of native SOC in soils where C availability was initially low, but this priming effect was not linked to increased gross protein depolymerization rates. Similarly, we found no connection to increased activities of enzymes targeting N-containing polymers such as proteins or chitin. Instead, glucose addition increased the microbial efficiency to use the N already available, as indicated by lower gross N mineralization rates and lower concentrations of inorganic N in the soil. We emphasize that these findings do not generally preclude that higher C availability can induce microbial N mining and thus enhance soil N availability in some soils, but that such an effect cannot be universally assumed. In contrast, the changes in microbial N dynamics observed across our range of boreal forest soils suggest that higher C availability can at least in some soils increase N storage within microbial bio- and necromass, thus reducing N availability for plants, but also constraining soil N losses, e.g., by nitrate leaching and denitrification.

Effect of variable soil texture, metal saturation of soil organic matter (SOM) and tree species composition on spatial distribution of SOM in forest soils in Poland.

PubMed

Gruba, Piotr; Socha, Jarosław; Błońska, Ewa; Lasota, Jarosław

2015-07-15

In this study we investigated the effect of fine (ϕ<0.05mm) fraction, i.e., silt+clay (FF) content in soils, site moisture, metal (Al and Fe) of soil organic matter (SOM) and forest species composition on the spatial distribution of carbon (C) pools in forest soils at the landscape scale. We established 275 plots in regular 200×200m grid in a forested area of 14.4km(2). Fieldwork included soil sampling of the organic horizon, mineral topsoil and subsoil down to 40cm deep. We analysed the vertical and horizontal distribution of soil organic carbon (SOC) stocks, as well as the quantity of physically separated fractions including the free light (fLF), occluded light (oLF) and mineral associated fractions (MAF) in the mineral topsoil (A, AE) horizons. Distribution of C in soils was predominantly affected by the variation in the FF content. In soils richer in the FF more SOC was accumulated in mineral horizons and less in the organic horizons. Accumulation of SOC in mineral soil was also positively affected by the degree of saturation of SOM with Al and Fe. The increasing share of beech influenced the distribution of C stock in soil profiles by reducing the depth of O horizon and increasing C stored in mineral soil. The content of FF was positively correlated with the content of C in MAF and fLF fractions. The content of oLF and MAF fractions was also positively influenced by a higher degree of metal saturation, particularly Al. Our results confirmed that Al plays an important role in the stabilization of SOM inside aggregates (CoLF) and as in CMAF fractions. We also found a significant, positive effect of beech on the CfLF and fir on the CoLF content. Copyright © 2015 Elsevier B.V. All rights reserved.

Global distribution of clay-size minerals on land surface for biogeochemical and climatological studies

PubMed Central

Ito, Akihiko; Wagai, Rota

2017-01-01

Clay-size minerals play important roles in terrestrial biogeochemistry and atmospheric physics, but their data have been only partially compiled at global scale. We present a global dataset of clay-size minerals in the topsoil and subsoil at different spatial resolutions. The data of soil clay and its mineralogical composition were gathered through a literature survey and aggregated by soil orders of the Soil Taxonomy for each of the ten groups: gibbsite, kaolinite, illite/mica, smectite, vermiculite, chlorite, iron oxide, quartz, non-crystalline, and others. Using a global soil map, a global dataset of soil clay-size mineral distribution was developed at resolutions of 2' to 2° grid cells. The data uncertainty associated with data variability and assumption was evaluated using a Monte Carlo method, and validity of the clay-size mineral distribution obtained in this study was examined by comparing with other datasets. The global soil clay data offer spatially explicit studies on terrestrial biogeochemical cycles, dust emission to the atmosphere, and other interdisciplinary earth sciences. PMID:28829435

Accelerated biodegradation of selected nematicides in tropical crop soils from Costa Rica.

PubMed

Chin-Pampillo, Juan Salvador; Carazo-Rojas, Elizabeth; Pérez-Rojas, Greivin; Castro-Gutiérrez, Víctor; Rodríguez-Rodríguez, Carlos E

2015-01-01

Degradation and mineralization behavior of selected nematicides was studied in soil samples from fields cultivated with banana, potato, and coffee. Degradation assays in most of the studied soils revealed shorter half-lives for carbofuran (CBF) and ethoprophos (ETP) in samples with a history of treatment with these compounds, which may have been caused by enhanced biodegradation. A short half-life value for CBF degradation was also observed in a banana field with no previous exposure to this pesticide, but with a recent application of the carbamate insecticide oxamyl, which supports the hypothesis that preexposure to oxamyl may cause microbial adaptation towards degradation of CBF, an observation of a phenomenon not yet tested according to the literature reviewed. Mineralization assays for CBF and terbufos (TBF) revealed that history of treatment with these nematicides did not cause higher mineralization rates in preexposed soils when compared to unexposed ones, except in the case of soils from coffee fields. Mineralization half-lives for soils unexposed to these pesticides were significantly shorter than most reports in the literature in the same conditions. Mineralization rates for soils with a previous exposure to these pesticides were also obtained, adding to the very few reports found. This paper contributes valuable data to the low number of reports dealing with pesticide fate in soils from tropical origin.

Effects of organic amendments on the mobility of Pb and Zn from mine tailings added to semi-arid soils.

PubMed

Barajas-Aceves, M; Rodríguez-Vázquez, R

2013-01-01

The effects of mine tailings and three organic amendments (compost, bokashi and vermicompost) on the mobility factor for Pb and Zn and on the potential C and N mineralization in semi-arid agricultural and rangeland soils were examined. During the experiment, soil samples were analyzed periodically for CO(2)-C evolution, inorganic N, dehydrogenase activity and percent Pb and Zn mobility during 169 d of incubation. The dehydrogenase activity and CO(2)-C evolved were strongly inhibited by mine tailings mixed with organic compost in both agricultural and rangeland soils (37 to 43 %), followed by N mineralization in treatments with mine tailings plus bokashi or compost (13 to 26.5 %) at 169 d incubation. The highest % mobility of Pb and Zn were observed in soils amended with mine tailings alone, while the lowest was observed in agricultural soils treated with vermicompost plus mine tailings. The CO(2)-C evolved was fitted to first order E, while the cumulative N mineralization was fitted to the linearized power function. Mine tailings were found to influence the potential C and N mineralization rate constants in both soils. The models for C and N mineralization could be used to evaluate the effects of mine tailings, which include intrinsic parameters in the soil.

Pattern of solute movement from snow into an upper Michigan stream

USGS Publications Warehouse

Stottlemyer, R.; Toczydlowski, D.

1990-01-01

Precipitation, snowpack, snowmelt, and streamwater samples were collected in a small gauged watershed draining into Lake Superior during winter 1987–88 to assess the importance of snowmelt pattern and meltwater pathways in the occurrence of solute pulses in streamwater. The snowpack along the south shore of Lake Superior can contain 50% of annual precipitation inputs and 38% of annual ionic inputs including moderate levels of strong acids. Throughout winter, thawed surface soils and small but steady snowpack moisture release promoted movement of snowpack solutes to surface mineral soils. Preferential elution of K+, NH4+, and H+ from the snowpack occurred with the initial thaw. Most ions exhibited pulses in snowmelt. Transport of snowpack solutes to the stream during snowmelt was through near-surface soil macropores and overland flow. For those ions with concentrations higher in the snowpack than in the premelt streamwater, K+, NH4+, and H+, the earliest snowmelt pulses had the greatest influence on streamwater chemistry. Unlike other portions of the region with resistant bedrock, the widespread presence of alkaline glacial till provides excess stream acid neutralization capacity (ANC) to buffer acidic inputs. Peak winter streamwater ANC reduction was caused principally by spring melt dilution of base cations and associated alkalinity, constant high SO42- levels, and an increase in NO3-. The maximum reduction in stream ANC was concurrent with overland flow. Relative to its snowmelt concentration, NO3- was highest in streamwater with some stream input likely the result of nitrification and N mineralization.

Carbon to organic matter ratios for soils in Rocky Mountain coniferous forests

Treesearch

Theresa B. Jain; Russell T. Graham; David L. Adams

1997-01-01

Vegetation type, soils, climate, and conversion ratios influence estimates of terrestrial C. Our objectives were to (i) determine carbon to organic matter (C/OM) ratios for brown cubical rotten wood, litter, surface humus, soil wood, and mineral soils; (ii) evaluate the validity of using 0.58 and 0.50 ratios for estimating C in mineral and organic soil components,...

[Nitrous oxide emission, nitrification, denitrification and nitrogen mineralization during rice growing season in 2 soils from Uruguay].

PubMed

Illarze, Gabriela; Del Pino, Amabelia; Riccetto, Sara; Irisarri, Pilar

Microbial processes such as mineralization, nitrification and denitrification regulate nitrogen dynamics in the soil. The last two processes may produce nitrous oxide (N 2 O). In this work N 2 O fluxes were quantified at four moments of the rice cycle, sowing, tillering, panicle initiation and maturity, in two sites that differed mainly in their soil organic matter (OM) content, Salto (higher OM) and Treinta y Tres. Potential net N mineralization, ammonium oxidation and denitrification as well as the most probable numbers (MPN) of ammonia oxidizers and denitrifiers were determined. Potential N mineralization did not vary with the soil type and increased at rice maturity. Neither ammonia oxidation potential nor MPN were different among the soils. However, the soil with higher OM exhibited higher activity and MPN of denitrifiers, irrespective of the rice stage. In turn, at the latest phases of the crop, the MPN of denitrifiers increased coinciding with the highest mineralization potential and mineral N content of the soil. Significant differences in N 2 O flux were observed in Salto, where the highest emissions were detected at rice maturity, after the soil was drained (44.2 vs 20.8g N-N 2 O/ha d in Treinta y Tres). This work shows the importance of considering the soil type and end-of-season drainage of the rice field to elaborate GHGs (greenhouse gases) inventories. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Utilization of forest slash to sequester carbon in loblolly pine plantations in the lower coastal plain

Treesearch

F. Sanchez; E.A. Carter; W. Edwards

2002-01-01

Soil-organic matter (SOM) is a complex array of components including soil fauna and flora at different stages of decomposition (Berg et al., 1982). Its concentration in soils can vary from 0.5% in mineral soils to almost 100% in peat soils (Brady, 1974). Organic matter (OM) in the surface mineral soil is considered a major determinant of forest ecosystem productivity...

Biodegradability of nonaqueous-phase liquids affects the mineralization of phenanthrene in soil because of microbial competition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, D.E.; Alexander, M.

1997-08-01

A study was conducted to determine the effects of biodegradability of nonaqueous-phase liquids (NAPLs) and microbial competition on the biodegradation in soil of a constituent of the NAPLs. The rates of mineralization of phenanthrene dissolved in 8 mg of 2,2,4,4,6,8,8-heptamethylnonane (HMN), di(2-ethylhexyl) phthalate (DEHP), or pristane per g of soil were faster than the rates when the compound was dissolved in hexadecane or dodecane. Addition of inorganic N and P to the soil increased the mineralization rate in the first two but not the last two NAPLs. N and P addition did not enhance mineralization of phenanthrene when added inmore » 500 {micro}g of hexadecane, pristane, or HMN per g of soil. Hexadecane was rapidly degraded, pristane was slowly metabolized, DEHP was still slower, and HMN was not mineralized in the test period. Mixing the soil stimulated mineralization of phenanthrene dissolved in HMN but not in hexadecane. Mineralization of phenanthrene dissolved in HMN was the same if the gas phase contained 21%, 2.1%, or traces of O{sub 2}. In contrast, the biodegradation of phenanthrene dissolved in hexadecane, although the same at 21 and 2.1% O{sub 2}, was not observed if traces of O{sub 2} were present. The mineralization was slower in unshaken soil-water mixtures if phenanthrene was added in hexadecane than in HMN or pristane, but the rates with the 3 NAPLs were increased by shaking the suspensions. The authors suggest that the biodegradability of major components of NAPLs and microbial competition for N, P, or O{sub 2} will have a major impact on the rate of transformation of minor constituents of NAPLs.« less

Predicting the mineral composition of dust aerosols - Part 1: Representing key processes

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Pérez García-Pando, C.; Miller, R. L.

2015-02-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, coating by heterogeneous uptake of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the resulting aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent in a soil whose aggregates are dispersed by wet sieving during analysis. We reconstruct the undispersed size distribution of the original soil that is subject to wind erosion. An empirical constraint upon the relative emission of clay and silt is applied that further differentiates the soil and aerosol mineral composition. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the extension brings the model into better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.

Mineral Abundances in Martian Soils

NASA Astrophysics Data System (ADS)

Martel, L. M. V.

2011-01-01

Using traditional geochemical calculations with in situ Martian cosmochemical data researchers Harry (Hap) McSween Jr. and Ian McGlynn (University of Tennessee) and Deanne Rogers (SUNY at Stony Brook) have developed a method for identifying the major and minor minerals in soils at the Mars Exploration Rovers (MER) landing sites. The team used information from the MER Athena instrument package operating on Mars since January, 2004. They created two models using MiniTES spectra, Alpha Particle X-ray Spectrometer (APXS) data, and Mossbauer spectrometer data to calculate the mineralogy of average dark soils on the Gusev crater plains and on Meridiani Planum, located on opposite sides of Mars. Soils at both locations are similarly composed of minerals derived from the comminution of basalts (about three quarters by weight) and other minerals derived from rocks altered by chemical weathering (about one quarter by weight). This mixture of possibly unrelated materials (primary and altered) might mean that the alteration of soil did not occur in place and that the basaltic and alteration suites of minerals came from different sources. The nearly identical modal mineralogy at two widely-separated locations on the planet supports a previous hypothesis based on comparable chemical compositions that soils have been homogenized, if not globally then at least over large areas of the Martian surface. Yet, global maps of orbital remote sensing data have not shown surface abundances of alteration minerals as high as those in the Martian soils.

Measurement of net nitrogen and phosphorus mineralization in wetland soils using a modification of the resin-core technique

USGS Publications Warehouse

Noe, Gregory B.

2011-01-01

A modification of the resin-core method was developed and tested for measuring in situ soil N and P net mineralization rates in wetland soils where temporal variation in bidirectional vertical water movement and saturation can complicate measurement. The modified design includes three mixed-bed ion-exchange resin bags located above and three resin bags located below soil incubating inside a core tube. The two inner resin bags adjacent to the soil capture NH4+, NO3-, and soluble reactive phosphorus (SRP) transported out of the soil during incubation; the two outer resin bags remove inorganic nutrients transported into the modified resin core; and the two middle resin bags serve as quality-control checks on the function of the inner and outer resin bags. Modified resin cores were incubated monthly for a year along the hydrogeomorphic gradient through a floodplain wetland. Only small amounts of NH4+, NO3-, and SRP were found in the two middle resin bags, indicating that the modified resin-core design was effective. Soil moisture and pH inside the modified resin cores typically tracked changes in the surrounding soil abiotic environment. In contrast, use of the closed polyethylene bag method provided substantially different net P and N mineralization rates than modified resin cores and did not track changes in soil moisture or pH. Net ammonification, nitrifi cation, N mineralization, and P mineralization rates measured using modified resin cores varied through space and time associated with hydrologic, geomorphic, and climatic gradients in the floodplain wetland. The modified resin-core technique successfully characterized spatiotemporal variation of net mineralization fluxes in situ and is a viable technique for assessing soil nutrient availability and developing ecosystem budgets.

May humic acids or mineral fertilisation mitigate arsenic mobility and availability to carrot plants (Daucus carota L.) in a volcanic soil polluted by As from irrigation water?

PubMed

Caporale, Antonio G; Adamo, Paola; Azam, Shah M G G; Rao, Maria A; Pigna, Massimo

2018-02-01

Carrot (Daucus carota L.) is a widely consumed root vegetable, whose growth and safety might be threatened by growing-medium arsenic (As) contamination. By this work, we evaluated the effects of humic acids from Leonardite and NPK mineral fertilisation on As mobility and availability to carrot plants grown for 60 days in a volcanic soil irrigated with As-contaminated water - representing the most common scenario occurring in As-affected Italian areas. As expected, the irrigation with As-contaminated water caused a serious toxic effect on plant growth and photosynthetic rate; the highest rate of As also inhibited soil enzymatic activity. In contrast, the organic and mineral fertilisation alleviated, at least partially, the toxicity of As, essentially by stimulating plant growth and promoting nutrient uptake. The mobility of As in the volcanic soil and thus its phytoavailability were differently affected by the organic and mineral fertilisers; the application of humic acids mitigated the availability of the contaminant, likely by its partial immobilisation on humic acid sorption sites - thus raising up the intrinsic anionic sorption capacity of the volcanic soil; the mineral fertilisation enhanced the mobility of As in soil, probably due to competition of P for the anionic sorption sites of the soil variable-charge minerals, very affine to available P. These findings hence suggest that a proper soil management of As-polluted volcanic soils and amendment by stable organic matter might mitigate the environmental risk of these soils, thus minimising the availability of As to biota. Copyright © 2017 Elsevier Ltd. All rights reserved.

Basaltic Soil of Gale Crater: Crystalline Component Compared to Martian Basalts and Meteorites

NASA Technical Reports Server (NTRS)

Treiman, A. H.; Bish, D. L.; Ming, D. W.; Morris, R. V.; Schmidt, M.; Downs, R. T.; Stolper, E. M.; Blake, D. F.; Vaniman, D. T.; Achilles, C. N.;

Interplay between physical movements of soils and mineral grains and chemical weathering

NASA Astrophysics Data System (ADS)

Yoo, K.

2007-12-01

Most soil biogeochemistry studies treat the soils and their inorganic and organic constituents as physically immobile. Those soil materials, however, are in perpetual motion due to the conversion of bedrock to soils, colluvial transport, and vertical mixing by various biophysical perturbations of the soils. Subsequently, a soil is continuously replaced by the materials from the neighboring soils and the underlying parent material, while its individual horizons are gradually mixed with the materials in the neighboring horizons. The movements of bulk soil materials are ultimately driven by moving individual mineral grains. While rarely appreciated, these physical movements of soil's mineral components operate in the presence of strong vertical and topographic gradients of the rates of mineral dissolution and leaching. The result is that the physical movement of soil constituents affects chemical weathering. The fluxes of soil materials (via physical movements and solute fluxes) in and out of a soil system defined by a researcher determine the time length that the materials reside in the system. The residence time, together with the system-specific rates of chemical weathering, determine the degree of weathering of the materials within the system. This presentation provides a new mathematical framework to consistently quantify the residence times of minerals, individual soil horizons, soil profiles, and an entire soil within a watershed boundary. Soil age, which is equivalent of the time length since the cessation of erosion or deposition on level grounds, becomes a special case of the residence time. The model is combined with empirical data to quantitatively illustrate the impacts that the physical motion of soil constituents have on the rates of chemical weathering. The data are drawn from ongoing field and laboratory studies focusing on the impact of river incision, colluvial flux, bioturbation, and agricultural tillage on the vertical and lateral variation of elemental composition within the soils.

Developing a molecular picture of soil organic matter–mineral interactions by quantifying organo–mineral binding

DOE PAGES

Newcomb, C. J.; Qafoku, N. P.; Grate, J. W.; ...

2017-08-30

Long residence times of soil organic matter have been attributed to reactive mineral surface sites that sorb organic species and cause inaccessibility due to isolation and chemical stabilization at the organic-mineral interface. Instrumentation for probing this interface is limited. As a result, much of the micron- and molecular-scale knowledge about organic-mineral interactions remains largely qualitative. We report the use of force spectroscopy to directly measure the binding between organic ligands with known chemical functionalities to soil minerals in aqueous environments. By systematically studying the role of organic functional group chemistry with model minerals, we demonstrate that the chemistry of bothmore » the organic ligand and mineral contribute to values of binding free energy and that changes in pH and ionic strength produce significant differences in binding energies. These direct measurements of molecular binding provide mechanistic insights into organo-mineral interactions, which could potentially inform land-carbon models that explicitly include mineral-bound C pools.« less

Developing a molecular picture of soil organic matter–mineral interactions by quantifying organo–mineral binding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newcomb, C. J.; Qafoku, N. P.; Grate, J. W.

Long residence times of soil organic matter have been attributed to reactive mineral surface sites that sorb organic species and cause inaccessibility due to isolation and chemical stabilization at the organic-mineral interface. Instrumentation for probing this interface is limited. As a result, much of the micron- and molecular-scale knowledge about organic-mineral interactions remains largely qualitative. We report the use of force spectroscopy to directly measure the binding between organic ligands with known chemical functionalities to soil minerals in aqueous environments. By systematically studying the role of organic functional group chemistry with model minerals, we demonstrate that the chemistry of bothmore » the organic ligand and mineral contribute to values of binding free energy and that changes in pH and ionic strength produce significant differences in binding energies. These direct measurements of molecular binding provide mechanistic insights into organo-mineral interactions, which could potentially inform land-carbon models that explicitly include mineral-bound C pools.« less

A structural equation model analysis of phosphorus transformations in global unfertilized and uncultivated soils

NASA Astrophysics Data System (ADS)

Hou, Enqing; Chen, Chengrong; Kuang, Yuanwen; Zhang, Yuguang; Heenan, Marijke; Wen, Dazhi

2016-09-01

Understanding the soil phosphorus (P) cycle is a prerequisite for predicting how environmental changes may influence the dynamics and availability of P in soil. We compiled a database of P fractions sequentially extracted by the Hedley procedure and its modification in 626 unfertilized and uncultivated soils worldwide. With this database, we applied structural equation modeling to test hypothetical soil P transformation models and to quantify the importance of different soil P pools and P transformation pathways in shaping soil P availability at a global scale. Our models revealed that soluble inorganic P (Pi, a readily available P pool) was positively and directly influenced by labile Pi, labile organic P (Po), and primary mineral P and negatively and directly influenced by secondary mineral P; soluble Pi was not directly influenced by moderately labile Po or occluded P. The overall effect on soluble Pi was greatest for labile Pi followed by the organic P pools, occluded P, and then primary mineral P; the overall influence from secondary mineral P was small. Labile Pi was directly linked to all other soil P pools and was more strongly linked than soluble Pi to labile Po and primary mineral P. Our study highlights the important roles of labile Pi in mediating P transformations and in determining overall P availability in soils throughout the world.

Mineral formation and organo-mineral controls on the bioavailability of carbon at the terrestrial-aquatic interface

NASA Astrophysics Data System (ADS)

Rod, K. A.; Smith, A. P.; Renslow, R.

2016-12-01

Recent evidence highlights the importance of organo-mineral interactions in regulating the source or sink capacity of soil. High surface area soils, such as allophane-rich or clay-rich soils, retain organic matter (OM) via sorption to mineral surfaces which can also contribute physical isolation in interlayer spaces. Despite the direct correlation between mineral surfaces and OM accumulation, the pedogenic processes controlling the abundance of reactive surface areas and their distribution in the mineral matrix remains unclear. As global soil temperatures rise, the dissolution of primary minerals and formation of new secondary minerals may be thermodynamically favored as part of soil weathering process. Newly formed minerals can supply surfaces for organo-metallic bonding and may, therefore, stabilize OM by surface bonding and physical exclusion. This is especially relevant in environments that intersect terrestrial and aquatic systems, such as the capillary fringe zone in riparian ecosystems. To test the mechanisms of mineral surface area protection of OM, we facilitated secondary precipitation of alumino-silicates in the presence of OM held at two different temperatures in natural Nisqually River sediments (Mt Rainier, WA). This was a three month reaction intended to simulate early pedogenesis. To tease out the influence of mineral surface area increase during pedogenesis, we incubated the sediments at two different soil moisture contents to induce biodegradation. We measured OM desorption, biodegradation, and the molecular composition of mineral-associated OM both prior to and following the temperature manipulation. To simulate the saturation of capillary fringe sediment and associated transport and reaction of OM, column experiments were conducted using the reacted sediments. More co-precipitation was observed in the 20°C solution compared to the 4°C reacted solution suggesting that warming trends alter mineral development and may remove more OM from solution. The results from the static experiments will be used to model and predict the impacts of mineral sorption and biological activity on OM persistence in the context of dynamic saturation conditions and heterogeneous material properties.

Magnetic Susceptibility and Mineral Zonations Controlled by Provenance in Loess along the Illinois and Central Mississippi River Valleys

USGS Publications Warehouse

Grimley, D.A.; Follmer, L.R.; McKay, E.D.

1998-01-01

Magnetic susceptibility (MS) patterns have proven useful for regional stratigraphic correlations of zones within thick, oxidized Peoria and Roxana Silts along the Illinois and Central Mississippi River valleys for more than 350 km. Variations in MS of C horizon loess are controlled by silt-sized magnetite content and are interpreted to reflect changes in sediment provenance due to fluctuations of the Superior and Lake Michigan glacier lobes and the diversion of the Mississippi River to its present course. Grain size distributions and scanning electron microscopic observations indicate that stratigraphic changes in MS are not significantly influenced by eolian sorting or diagenetic dissolution, respectively. Three compositional zones (lower, middle, and upper) are delineated within Peoria Silt which usually can be traced in the field by MS, the occurrence of clay beds, interstadial soils, and/or subtle color changes. These zones can be correlated with, but are generally of more practical use than, previously studied dolomite zones (McKay, 1977) or clay mineral zones (Frye et al., 1968). However, mineralogical analyses can help to substantiate zone boundaries when in question. MS and compositional zones may indirectly record a climatic signal, primarily through the effect that global cooling has had on ice lobe fluctuations in the Upper Mississippi drainage basin. ?? 1998 University of Washington.

Relative nitrogen mineralization and nitrification potentials in relation to soil chemistry in oak forest soils along a historical deposition gradient

Treesearch

Ralph E. J. Boerner; Elaine Kennedy Sutherland

1996-01-01

This study quantified soil nutrient status and N mineralization/nitrification potentials in soils of oak-dominated, unmanaged forest stands in seven USDA Forest Service experimental forests (EF) ranging along a historical and current acidic deposition gradient from southern Illinois to central West Virginia.

Effect of Soil Amendments on Cd accumulation by Spinach from a Cd-Mineralized Soil

USDA-ARS?s Scientific Manuscript database

Cadmium mineralized soils occur in many nations. When these soils are non-calcareous, crops and especially leafy vegetables such as lettuce and spinach accumulate levels of Cd which exceed international standards. Lockwood loam from Monterey Co., CA, has been found to cause excessive Cd in leafy veg...

Tracking plant-derived biomarkers from source to sink in the Miners River, Upper Peninsula of Michigan (USA)

NASA Astrophysics Data System (ADS)

Giri, S. J.; Diefendorf, A. F.; Lowell, T. V.

2012-12-01

Biogeochemical cycling of terrestrial organic matter and it subsequent burial plays a vital role in the global carbon cycle. Rivers provide a pathway for terrestrial organic carbon dispersal and integration into sediments. Terrestrial plant biomarkers are useful tools for studying carbon cycling because they can provide an indication of the source of organic carbon in both modern and ancient sediments. Biomarkers can also be used as paleovegetation proxies in geologic sediments where fossils are absent. However, limited information is available about the dispersal and deposition of plant biomarkers in modern river systems, especially for compounds that provide taxonomic specificity such as di- and triterpenoids (diagnostic for conifers and angiosperms, respectively). To better resolve the modes of biomarker transport within fluvial and riparian systems, we characterized plant biomarker transport in the Miners River, a small river basin within a mixed angiosperm-conifer forest at Pictured Rocks National Lakeshore (MI, USA). To assess the transport of biomarkers in river systems, we collected plants, soils, river sediments, and filtered particulate and dissolved organic carbon from seven sites from the headwaters to Lake Superior along the Miners River (~20 km pathway). All samples contained long-chain n-alkyl lipids, sterols, diterpenoids (abietane and pimarane classes), and triterpenoids (oleanane, ursane, and lupane classes). With the exception of a soil sample taken at a depth of 30 cm, triterpenoids are found in higher concentrations than diterpenoids in riparian soils and river sediments. Biomarker compositions in riparian soils, point bar, and overbank deposits are similar to the surrounding vegetation, albeit much lower in concentration. The composition of di- and triterpenoids in the river-suspended particulate organic carbon is similar in composition to the surrounding vegetation and soils. We developed a method to isolate biomarkers in the dissolved organic carbon fraction in river waters using solid-phase extraction and the preliminary data suggests that di- and triterpenoids are transported as dissolved organic carbon, however concentrations are lower than in the particulate organic carbon fraction. Results from the Miners River will help to better define terrestrial organic matter cycling in small river catchments. Characterizing how plant biomarkers are transported in river systems will enhance our interpretations of plant biomarkers in the geologic record. This will provide new insights into biomarker transport and potential source/sink biases in fluvial systems and thus identify potential complications for using plant-derived biomarkers as quantitative paleovegetation indicators and will enhance the use of biomarker-specific isotope analyses.

Growth of Dalbergia sissoo in desert regions of western India using municipal effluent and the subsequent changes in soil and plant chemistry.

PubMed

Singh, G; Bhati, M

2005-06-01

Increasing demand for fodder and fuelwood and the scarcity of a good quality water in arid areas has resulted in a search for an alternative source of water for biomass production. An experiment utilizing municipal effluent in growing Dalbergia sissoo was conducted. Five treatments included T1, municipal effluent at 1 PET (Potential evapo-transpiration) (without plant); T2, municipal effluent at 1/2 PET; T3, municipal effluent at 1PET; T4, municipal effluent at 2 PET; and T5, canal water at 1 PET. Observations included plant height, collar diameter at one-month intervals and plant mineral composition, mineral uptake and changes in soil properties at 24 months of plant age. Application of municipal effluent produced better growth in D. sissoo seedlings. Concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were greater in seedlings irrigated with municipal effluent than those of the seedlings irrigated by the treatment T5, and positively related with the quantity of irrigation. The concentrations were greatest in foliage compared to the other parts of seedling, with the exception of Cu concentration. Application of municipal effluents resulted in a 2- to 3-fold increase in the concentrations of soil K, Cu, Fe, Mn and Zn, whereas NH4-N and PO4-P availability increased by 8.1- and 4.5-fold, respectively. The increase in soil organic carbon was only observed in treatments T3 and T4. The accumulations of soil NO3-N, Na, Cu, Fe, Mn and Zn were more in lower soil layers but the other soil parameters showed their greatest values in the upper soil layer. Irrigation using municipal effluent did not result in toxicity to the seedlings before the age of 24 months. The results suggest that municipal effluent could be utilized, as an important source of water and nutrients in growing D. sissoo to increase biomass production in the needs of suburban dwellers. However, a preliminary treatment to reduce excess NH4-N and PO4-P will be required before application to the plantation.

Soil organic carbon and nitrogen pools drive soil C-CO2 emissions from selected soils in Maritime Antarctica.

PubMed

Pires, C V; Schaefer, C E R G; Hashigushi, A K; Thomazini, A; Filho, E I F; Mendonça, E S

2017-10-15

The ongoing trend of increasing air temperatures will potentially affect soil organic matter (SOM) turnover and soil C-CO 2 emissions in terrestrial ecosystems of Maritime Antarctica. The effects of SOM quality on this process remain little explored. We evaluated (i) the quantity and quality of soil organic matter and (ii) the potential of C release through CO 2 emissions in lab conditions in different soil types from Maritime Antarctica. Soil samples (0-10 and 10-20cm) were collected in Keller Peninsula and the vicinity of Arctowski station, to determine the quantity and quality of organic matter and the potential to emit CO 2 under different temperature scenarios (2, 5, 8 and 11°C) in lab. Soil organic matter mineralization is low, especially in soils with low organic C and N contents. Recalcitrant C form is predominant, especially in the passive pool, which is correlated with humic substances. Ornithogenic soils had greater C and N contents (reaching to 43.15gkg -1 and 5.22gkg -1 for total organic carbon and nitrogen, respectively). C and N were more present in the humic acid fraction. Lowest C mineralization was recorded from shallow soils on basaltic/andesites. C mineralization rates at 2°C were significant lower than at higher temperatures. Ornithogenic soils presented the lowest values of C-CO 2 mineralized by g of C. On the other hand, shallow soils on basaltic/andesites were the most sensitive sites to emit C-CO 2 by g of C. With permafrost degradation, soils on basaltic/andesites and sulfates are expected to release more C-CO 2 than ornithogenic soils. With greater clay contents, more protection was afforded to soil organic matter, with lower microbial activity and mineralization. The trend of soil temperature increases will favor C-CO 2 emissions, especially in the reduced pool of C stored and protected on permafrost, or in occasional Histosols. Copyright © 2016 Elsevier B.V. All rights reserved.

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

NASA Astrophysics Data System (ADS)

Xiao, Jian; He, Xinhua; Hao, Jialong; Zhou, Ying; Zheng, Lirong; Ran, Wei; Shen, Qirong; Yu, Guanghui

2016-06-01

Mineral binding is a major mechanism for soil carbon (C) stabilization. However, the submicron information about the in situ mechanisms of different fertilization practices affecting organo-mineral complexes and associated C preservation remains unclear. Here, we applied nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS) to examine differentiating effects of inorganic versus organic fertilization on interactions between highly reactive minerals and soil C preservation. To examine such interactions, soils and their extracted colloids were collected during a 24-year long-term fertilization period (1990-2014) (no fertilization, control; chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization, NPK; and NPK plus swine manure fertilization, NPKM). The results for different fertilization conditions showed a ranked soil organic matter concentration with NPKM > NPK > control. Meanwhile, oxalate-extracted Al (Alo), Fe (Feo), short-range ordered Al (Alxps), Fe (Fexps), and dissolved organic carbon (DOC) ranked with NPKM > control > NPK, but the ratios of DOC / Alxps and DOC / Fexps ranked with NPKM > NPK > control. Compared with the NPK treatment, the NPKM treatment enhanced the C-binding loadings of Al and Fe minerals in soil colloids at the submicron scale. Furthermore, a greater concentration of highly reactive Al and Fe minerals was presented under NPKM than under NPK. Together, these submicron-scale findings suggest that both the reactive mineral species and their associations with C are differentially affected by 24-year long-term inorganic and organic fertilization.

Soil Organic Carbon and Its interaction with Minerals in Two Hillslopes with Different Climates and Erosion Processes

NASA Astrophysics Data System (ADS)

Wang, X.; Yoo, K.; Wackett, A. A.; Gutknecht, J.; Amundson, R.; Heimsath, A. M.

2017-12-01

Climate and topography have been widely recognized as important factors regulating soil organic carbon (SOC) dynamics but their interactive effects on SOC storage and its pools remain poorly constrained. Here we aimed to evaluate SOC storages and carbon-mineral interactions along two hillslope transects with moderately different climates (MAP: 549 mm vs. 816 mm) in Southeastern Australia. We sampled soil along the convex (eroding)-to-convergent (depositional) continuum at each hillslope transect and conducted size and density fractionation of these samples. In responses to the difference in climate factor, SOC inventories of eroding soils were twice as large at the wetter site compared with the drier site but showed little difference between two sites in depositional soils. These trends in SOC inventories were primarily controlled by SOC concentrations and secondarily by soil thicknesses. Similar patterns were observed for mineral associated organic carbon (MOC), and the abundances of MOC were controlled by the two independently operating processes affecting MOC concentration and fine-heavy fraction minerals. The contents and species of secondary clay and iron oxide minerals, abundances of particulate organic carbon, and bioturbation affected MOC concentrations. In contrast, the abundances of fine-heavy fraction minerals were impacted by erosion mechanisms that uniquely responded to regional- and micro- climate conditions. Consequently, topographic influences on SOC inventories and carbon-mineral interactions were more strongly pronounced in the drier climate where vegetation and erosion mechanisms were sensitive to microclimate. Our results highlight the significance of understanding topography and erosional processes in capturing climatic effects on soil carbon dynamics.

The role of minerals and mean annual temperature on soil carbon accumulation: A modeling analysis

NASA Astrophysics Data System (ADS)

Abramoff, R. Z.; Georgiou, K.; Tang, J.; Torn, M. S.; Riley, W. J.

2016-12-01

Soil organic carbon (SOC) is the largest actively cycling terrestrial C pool with mean residence times that can exceed 10,000 years. There is strong evidence suggesting that SOC dynamics depend on soil temperature and C inputs to soil through net primary production (NPP), but it is unclear what the relative importance of these factors is relative to SOC protection by minerals. Recent empirical studies have suggested that mineral protection explains more variation in SOC stock sizes and C respiration fluxes than does NPP or climate. Our previous modeling has demonstrated that representing the chemistry of mineral sorption in a microbially-explicit model affects the temperature sensitivity of SOC dynamics. We apply this modeling framework to interpret observations of SOC stocks, mineral surface availability, mean annual temperature (MAT), and NPP collected along a 4,000 km transect in South America. We use a Random Forest machine learning algorithm and regression to analyze our model output and the empirical data. This analysis shows that mineral surface availability is the dominant control over C respiration and SOC stock, and is substantially larger than the effects of belowground NPP. We further show that minerals interact with MAT to determine the observed range of SOC stocks along this transect in the present day, as well as projected SOC stocks under long-term warming. Our model-data comparison suggests that soil mineralogy and MAT will explain the majority of the spatial variation in SOC stock over decadal-to-millennial timescales. We extend the analysis of these interactions using the ACME Land Model (ALM) coupled with an explicit representation of microbes, minerals, and vertical transport of solutes and gases. The model results confirm the dominant effects of minerals on organic matter decomposition throughout the soil column.

Organic matter compositions and loadings in soils and sediments along the Fly River, Papua New Guinea

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; Moore, Eric; Kurtz, Andrew; Portier, Evan; Alleau, Yvan; Merrell, David

2014-09-01

The compositions and loadings of organic matter in soils and sediments from a diverse range of environments along the Fly River system were determined to investigate carbon transport and sequestration in this region. Soil horizons from highland sites representative of upland sources have organic carbon contents (%OC) that range from 0.3 to 25 wt%, carbon:nitrogen ratios (OC/N) that range from 7 to 25 mol/mol, highly negative stable carbon isotopic compositions (δ13Corg < -26‰) and variable concentrations of lignin phenols (1 < LP < 5 mg/100 mg OC). These compositions reflect inputs from local vegetation, with contributions from bedrock carbon in the deeper mineral horizons. Soils developed on the levees of active floodplains receive inputs of allochthonous materials by overbank deposition as well as autochthonous inputs from local vegetation. In the forested upper floodplain reaches, %OC contents are lower than upland soils (0.8-1.5 wt%) as are OC/N ratios (9-15 mol/mol) while δ13Corg (-25 to -28‰) and LP (2-6 mg/100 mg OC) values are comparable to upland soils. These results indicate that organic matter present in these active floodplain soils reflect local (primarily C3) vegetation inputs mixed with allochthonous organic matter derived from eroded bedrock. In the lower reaches of the floodplain, which are dominated by swamp grass vegetation, isotopic compositions were less negative (δ13Corg > -25‰) and non-woody vegetation biomarkers (cinnamyl phenols and cutin acids) more abundant relative to upper floodplain sites. Soils developed on relict Pleistocene floodplain terraces, which are typically not flooded and receive little sediment from the river, were characterized by low %OC contents (<0.6 wt%), low OC/N ratios (<9 mol/mol), more positive δ13Corg signatures (>-21‰) and low LP concentrations (∼3 mg/100 mg OC). These relict floodplain soils contain modern carbon that reflects primarily local (C3 or C4) vegetation sources. Total suspended solids collected along the river varied widely in overall concentrations (1 < TSS < 9000 mg/L), %OC contents (0.1-60 wt%), OC/N ratios (7-17 mol/mol) and δ13Corg signatures (-26 to -32‰). These compositions reflect a mixture of C3 vascular plants and freshwater algae. However, little of this algal production appears to be preserved in floodplain soils. A comparison of organic carbon loadings of active floodplain soils (0.2 and 0.5 mg C/m2) with previous studies of actively depositing sediments in the adjacent delta-clinoform system (0.4-0.7 mg C/m2) indicates that Fly River floodplain sediments are less effective at sequestering organic carbon than deltaic sediments. Furthermore, relict Pleistocene floodplain sites with low or negligible modern sediment accumulation rates display significantly lower loadings (0.1-0.2 mg C/m2). This deficit in organic carbon likely reflects mineralization of sedimentary organic carbon during long term oxidative weathering, further reducing floodplain carbon storage.

The Mineralosphere Concept: Mineralogical Control of the Distribution and Function of Mineral-associated Bacterial Communities.

PubMed

Uroz, Stephane; Kelly, Laura Catherine; Turpault, Marie-Pierre; Lepleux, Cendrella; Frey-Klett, Pascale

2015-12-01

Soil is composed of a mosaic of different rocks and minerals, usually considered as an inert substrata for microbial colonization. However, recent findings suggest that minerals, in soils and elsewhere, favour the development of specific microbial communities according to their mineralogy, nutritive content, and weatherability. Based upon recent studies, we highlight how bacterial communities are distributed on the surface of, and in close proximity to, minerals. We also consider the potential role of the mineral-associated bacterial communities in mineral weathering and nutrient cycling in soils, with a specific focus on nutrient-poor and acidic forest ecosystems. We propose to define this microbial habitat as the mineralosphere, where key drivers of the microbial communities are the physicochemical properties of the minerals. Copyright © 2015 Elsevier Ltd. All rights reserved.

Species diversity and chemical properties of litter influence non-additive effects of litter mixtures on soil carbon and nitrogen cycling

PubMed Central

Mao, Bing; Mao, Rong; Zeng, De-Hui

2017-01-01

Decomposition of litter mixtures generally cannot be predicted from the component species incubated in isolation. Therefore, such non-additive effects of litter mixing on soil C and N dynamics remain poorly understood in terrestrial ecosystems. In this study, litters of Mongolian pine and three dominant understory species and soil were collected from a Mongolian pine plantation in Northeast China. In order to examine the effects of mixed-species litter on soil microbial biomass N, soil net N mineralization and soil respiration, four single litter species and their mixtures consisting of all possible 2-, 3- and 4-species combinations were added to soils, respectively. In most instances, species mixing produced synergistic non-additive effects on soil microbial biomass N and soil respiration, but antagonistic non-additive effects on net N mineralization. Species composition rather than species richness explained the non-additive effects of species mixing on soil microbial biomass N and net N mineralization, due to the interspecific differences in litter chemical composition. Both litter species composition and richness explained non-additive soil respiration responses to mixed-species litter, while litter chemical diversity and chemical composition did not. Our study indicated that litter mixtures promoted soil microbial biomass N and soil respiration, and inhibited net N mineralization. Soil N related processes rather than soil respiration were partly explained by litter chemical composition and chemical diversity, highlighting the importance of functional diversity of litter on soil N cycling. PMID:28686660

Species diversity and chemical properties of litter influence non-additive effects of litter mixtures on soil carbon and nitrogen cycling.

PubMed

Mao, Bing; Mao, Rong; Zeng, De-Hui

2017-01-01

Decomposition of litter mixtures generally cannot be predicted from the component species incubated in isolation. Therefore, such non-additive effects of litter mixing on soil C and N dynamics remain poorly understood in terrestrial ecosystems. In this study, litters of Mongolian pine and three dominant understory species and soil were collected from a Mongolian pine plantation in Northeast China. In order to examine the effects of mixed-species litter on soil microbial biomass N, soil net N mineralization and soil respiration, four single litter species and their mixtures consisting of all possible 2-, 3- and 4-species combinations were added to soils, respectively. In most instances, species mixing produced synergistic non-additive effects on soil microbial biomass N and soil respiration, but antagonistic non-additive effects on net N mineralization. Species composition rather than species richness explained the non-additive effects of species mixing on soil microbial biomass N and net N mineralization, due to the interspecific differences in litter chemical composition. Both litter species composition and richness explained non-additive soil respiration responses to mixed-species litter, while litter chemical diversity and chemical composition did not. Our study indicated that litter mixtures promoted soil microbial biomass N and soil respiration, and inhibited net N mineralization. Soil N related processes rather than soil respiration were partly explained by litter chemical composition and chemical diversity, highlighting the importance of functional diversity of litter on soil N cycling.

Organic layer serves as a hotspot of microbial activity and abundance in Arctic tundra soils.

PubMed

Lee, Seung-Hoon; Jang, Inyoung; Chae, Namyi; Choi, Taejin; Kang, Hojeong

2013-02-01

Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem.

[Nitrogen Fraction Distributions and Impacts on Soil Nitrogen Mineralization in Different Vegetation Restorations of Karst Rocky Desertification].

PubMed

Hu, Ning; Ma, Zhi-min; Lan, Jia-cheng; Wu, Yu-chun; Chen, Gao-qi; Fu, Wa-li; Wen, Zhi-lin; Wang, Wen-jing

2015-09-01

In order to illuminate the impact on soil nitrogen accumulation and supply in karst rocky desertification area, the distribution characteristics of soil nitrogen pool for each class of soil aggregates and the relationship between aggregates nitrogen pool and soil nitrogen mineralization were analyzed in this study. The results showed that the content of total nitrogen, light fraction nitrogen, available nitrogen and mineral nitrogen in soil aggregates had an increasing tendency along with the descending of aggregate-size, and the highest content was occurred in < 0. 25 mm. The content of nitrogen fractions for all aggregate-classes followed in the order of abandoned land < grass land < brush land < brush-arbor land < arbor land in different sample plots. Artificial forest lands had more effects on the improvement of the soil nitrogen than honeysuckle land. In this study it also showed the nitrogen stockpiling quantity of each aggregate-size class was differed in all aggregate-size classes, in which the content of nitrogen fraction in 5-10 mm and 2-5 mm classes of soil aggregate-size were the highest. And it meant that soil nutrient mainly was stored in large size aggregates. Large size aggregates were significant to the storage of soil nutrient. For each class of soil aggregate-size, the contribution of the nitrogen stockpiling quantity of 0. 25-1 mm class to soil net nitrogen mineralization quantity was the biggest, and following >5mm and 2-5 mm classes, and the others were the smallest. With the positive vegetation succession, the weight percentage of > 5 mm aggregate-size classes was improved and the nitrogen storage of macro-aggregates also was increased. Accordingly, the capacity of soil supply mineral nitrogen and storage organic nitrogen were intensified.

Mineralogical controls on microbial biomass accumulation on two tropical soils

NASA Astrophysics Data System (ADS)

Block, K. A.; Pena, S. A.; Katz, A.; Gottlieb, P.; Volta, A.

2017-12-01

The characteristics of soil organic matter (SOM) generated by microbes and associated with minerals are not well defined. This information is critical to reducing uncertainty in climate models related to C cycling and ecosystem feedbacks. The resistance to degradation of mineral-associated SOM is influenced by aggregate structure, mineral chemistry and microbial community. In this work we examine the influence of mineral composition, including amorphous coatings on the biomass yield and aggregate structure through thermogravimetric analysis, X-ray diffraction and electron microscopy. Two soil organisms, Pseudomonas phaseolicola, and Streptomyces griseosporus, were each incubated over a 72-hour period in minimal media with the < 63 µm fraction of two tropical soils of differing mineralogies: an Inceptisol and an Oxisol from the Luquillo Critical Zone Observatory in Puerto Rico. Aggregates were analyzed by thermogravimetric analysis to determine relative amount of biomass associated with the minerals and compared to planktonic (mineral-free) biomass cultured under the same conditions. In all samples, approximately half of the sample mass loss occurred between 175 ºC - 375 ºC, which we attribute to biomolecules accumulated on the mineral surfaces. We observed a slightly larger mass loss in the Inceptisol than in the Oxisol, most of which corresponded to compounds that underwent pyrolysis at 300 ºC. HRTEM micrographs and TEM-EDS image maps showing the spatial relationship of microbial necromass to soil minerals will be reported.

Soil organic carbon quality in forested mineral wetlands at different mean annual temperature.

Treesearch

Cinzia Fissore; Christian P. Giardina; Randall K. Kolka; Carl C. Trettin

2009-01-01

Forested mineral soil wetlands (FMSW) store large stocks of soil organic carbon (SOC), but little is known on: (i) whether the quality of SOC stored in these soils (proportion of active versus more resistant SOC compounds) differs from SOC in upland soils; (ii) how the quality of SOC in FMSW varies with mean annual temperature (MAT); and (iii) whether SOC decomposition...

Out of sight - Profiling soil characteristics, nutrients and microbial communities affected by organic amendments down to one meter in a long-term maize cultivation experiment

NASA Astrophysics Data System (ADS)

Lehtinen, Taru; Mikkonen, Anu; Zavattaro, Laura; Grignani, Carlo; Baumgarten, Andreas; Spiegel, Heide

2016-04-01

Soil characteristics, nutrients and microbial activity in the deeper soil layers are topics not of-ten covered in agricultural studies since the main interest lies within the most active topsoils and deep soils are more time-consuming to sample. Studies have shown that deep soil does matter, although biogeochemical cycles are not fully understood yet. The main aim of this study is to investigate the soil organic matter dynamics, nutrients and microbial community composition in the first meter of the soil profiles in the long-term maize cropping system ex-periment Tetto Frati, in the vicinity of the Po River in Northern Italy. The trial site lies on a deep, calcareous, free-draining soil with a loamy texture. The following treatments have been applied since 1992: 1) maize for silage with 250 kg mineral N ha-1 (crop residue removal, CRR), 2) maize for grain with 250 kg mineral N ha-1 (crop residue incorporation, CRI), 3) maize for silage with 250 kg bovine slurry N ha-1 (SLU), 4) maize for silage with 250 kg farm yard manure N ha-1 (FYM). Soil characteristics (pH, carbonate content, soil organic carbon (SOC), aggregate stability (WSA)), and nutrients (total nitrogen (Nt), CAL-extractable phos-phorous (P) and potassium (K), potential N mineralisation) were investigated. Bacteri-al community composition was investigated with Ion PGM high-throughput sequencing at the depth of 8000 sequences per sample. Soil pH was moderately alkaline in all soil samples, in-creasing with increasing soil depth, as the carbonate content increased. SOC was significantly higher in the treatments with organic amendments (CRI, SLU and FYM) compared to CRR in 0-25 cm (11.1, 11.6, 14.7 vs. 9.8 g kg-1, respectively), but not in the deeper soil. At 50-75 cm soil depth FYM treatment revealed higher WSA compared to CRR, as well as higher CAL-extractable K (25 and 15 mg kg-1, respectively) and potential N mineralisation (11.30 and 8.78 mg N kg-1 7d-1, respectively). At 75-100 cm soil depth, SLU and FYM had the highest poten-tial N mineralisation. Microbial biomass and bacterial diversity decreased downwards the soil profile. Incorporation of crop residues alone showed no positive impacts on either biomass or diversity, whereas fertilization by FYM instead of mineral fertilizer did. Microbial community composition showed depth-related shifts: Proteobacteria and Actinobacteria dominated the upper layer, whereas Gemmatimonadetes showed the highest relative abundance in the mid-layers and Chloroflexi deeper in the soil profile. The main factor determining soil bacterial community composition in the entire dataset was not the treatments but the layers. Interesting-ly, the surface layers that we expected to be most impacted by the treatments were much more similar to each other, regardless of treatment or block, than samples from the deeper layers were to each other. This means that agricultural practices strongly influence the soil bacterial composition and reduce its wide natural heterogeneity. This calls for continuous efforts to study the deeper soil layers in the numerous long-term field experiments, where mostly the topsoils are currently studied in detail.

Plant litter chemistry alters the content and composition of organic carbon associated with soil mineral and aggregate fractions in invaded ecosystems.

PubMed

Tamura, Mioko; Suseela, Vidya; Simpson, Myrna; Powell, Brian; Tharayil, Nishanth

2017-10-01

Through the input of disproportionate quantities of chemically distinct litter, invasive plants may potentially influence the fate of organic matter associated with soil mineral and aggregate fractions in some of the ecosystems they invade. Although context dependent, these native ecosystems subjected to prolonged invasion by exotic plants may be instrumental in distinguishing the role of plant-microbe-mineral interactions from the broader edaphic and climatic influences on the formation of soil organic matter (SOM). We hypothesized that the soils subjected to prolonged invasion by an exotic plant that input recalcitrant litter (Japanese knotweed, Polygonum cuspidatum) would have a greater proportion of plant-derived carbon (C) in the aggregate fractions, as compared with that in adjacent soil inhabited by native vegetation that input labile litter, whereas the soils under an invader that input labile litter (kudzu, Pueraria lobata) would have a greater proportion of microbial-derived C in the silt-clay fraction, as compared with that in adjacent soils that receive recalcitrant litter. At the knotweed site, the higher C content in soils under P. cuspidatum, compared with noninvaded soils inhabited by grasses and forbs, was limited to the macroaggregate fraction, which was abundant in plant biomarkers. The noninvaded soils at this site had a higher abundance of lignins in mineral and microaggregate fractions and suberin in the macroaggregate fraction, partly because of the greater root density of the native species, which might have had an overriding influence on the chemistry of the above-ground litter input. At the kudzu site, soils under P. lobata had lower C content across all size fractions at a 0-5 cm soil depth despite receiving similar amounts of Pinus litter. Contrary to our prediction, the noninvaded soils receiving recalcitrant Pinus litter had a similar abundance of plant biomarkers across both mineral and aggregate fractions, potentially because of the higher surface area of soil minerals at this site. The plant biomarkers were lower in the aggregate fractions of the P. lobata-invaded soils, compared with noninvaded pine stands, potentially suggesting a microbial co-metabolism of pine-derived compounds. These results highlight the complex interactions among litter chemistry, soil biota, and minerals in mediating soil C storage in unmanaged ecosystems; these interactions are particularly important under global changes that may alter plant species composition and hence the quantity and chemistry of litter inputs in terrestrial ecosystems. © 2017 John Wiley & Sons Ltd.

Effects of forest conversion on soil microbial communities depend on soil layer on the eastern Tibetan Plateau of China

PubMed Central

He, Ruoyang; Yang, Kaijun; Li, Zhijie; Schädler, Martin; Yang, Wanqin; Wu, Fuzhong; Tan, Bo; Zhang, Li

2017-01-01

Forest land-use changes have long been suggested to profoundly affect soil microbial communities. However, how forest type conversion influences soil microbial properties remains unclear in Tibetan boreal forests. The aim of this study was to explore variations of soil microbial profiles in the surface organic layer and subsurface mineral soil among three contrasting forests (natural coniferous forest, NF; secondary birch forest, SF and spruce plantation, PT). Soil microbial biomass, activity and community structure of the two layers were investigated by chloroform fumigation, substrate respiration and phospholipid fatty acid analysis (PLFA), respectively. In the organic layer, both NF and SF exhibited higher soil nutrient levels (carbon, nitrogen and phosphorus), microbial biomass carbon and nitrogen, microbial respiration, PLFA contents as compared to PT. However, the measured parameters in the mineral soils often did not differ following forest type conversion. Irrespective of forest types, the microbial indexes generally were greater in the organic layer than in the mineral soil. PLFAs biomarkers were significantly correlated with soil substrate pools. Taken together, forest land-use change remarkably altered microbial community in the organic layer but often did not affect them in the mineral soil. The microbial responses to forest land-use change depend on soil layer, with organic horizons being more sensitive to forest conversion. PMID:28982191

Kinetics of mineralization of organic compounds at low concentrations in soil.

PubMed Central

Scow, K M; Simkins, S; Alexander, M

1986-01-01

The kinetics of mineralization of 14C-labeled phenol and aniline were measured at initial concentrations ranging from 0.32 to 5,000 ng and 0.30 ng to 500 micrograms/g of soil, respectively. Mineralization of phenol at concentrations less than or equal to 32 ng/g of soil and of aniline at all concentrations began immediately, and the curves for the evolution of labeled CO2 were biphasic. The patterns of mineralization of 4.0 ng of 2,4-dichlorophenol per g of soil and 20 ng of nitrilotriacetic acid per g of soil were similar to the patterns for phenol and aniline. The patterns of mineralization of 1.0 to 100 ng of p-nitrophenol and 6.0 ng of benzylamine per g of soil were also biphasic but after a short apparent lag period. The curves of CO2 evolution from higher concentrations of phenol and p-nitrophenol had increasing apparent lag phases and were S-shaped or linear. Cumulative plots of the percentage of substrate converted to CO2 were fit by nonlinear regression to first-order, integrated Monod, logistic, logarithmic, zero-order, three-half-order, and two-compartment models. None of the models of the Monod family provided the curve of best fit to any of the patterns of mineralization. The linear growth form of the three-half-order model provided the best fit for the mineralization of p-nitrophenol, with the exception of the lowest concentrations, and of benzylamine. The two-compartment model provided the best fit for the mineralization of concentrations of phenol below 100 ng/g, of several concentrations of aniline, and of nitrilotriacetic acid. It is concluded that models derived from the Monod equation, including the first-order model, do not adequately describe the kinetics of mineralization of low concentrations of chemicals added to soil. PMID:3729388

In situ visualisation and characterisation of the capacity of highly reactive minerals to preserve soil organic matter (SOM) in colloids at submicron scale.

PubMed

Xiao, Jian; Wen, Yongli; Li, Huan; Hao, Jialong; Shen, Qirong; Ran, Wei; Mei, Xinlan; He, Xinhua; Yu, Guanghui

2015-11-01

Mineral-organo associations (MOAs) are a mixture of identifiable biopolymers associated with highly reactive minerals and microorganisms. However, the in situ characterization and correlation between soil organic matter (SOM) and highly reactive Al and Fe minerals are still unclear for the lack of technologies, particularly in the long-term agricultural soil colloids at submicron scale. We combined several novel techniques, including nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray absorption near edge structure (XANES) and confocal laser scanning microscopy (CLSM) to characterise the capacity of highly reactive Al and Fe minerals to preserve SOM in Ferralic Cambisol in south China. Our results demonstrated that: (1) highly reactive minerals were strongly related to SOM preservation, while SOM had a more significant line correlation with the highly reactive Al minerals than the highly reactive Fe minerals, according to the regions of interest correlation analyses using NanoSIMS; (2) allophane and ferrihydrite were the potential mineral species to determine the SOM preservation capability, which was evaluated by the X-ray photoelectron spectroscopy (XPS) and Fe K-edge XANES spectroscopy techniques; and (3) soil organic biopolymers with dominant compounds, such as proteins, polysaccharides and lipids, were distributed at the rough and clustered surface of MOAs with high chemical and spatial heterogeneity according to the CLSM observation. Our results also promoted the understanding of the roles played by the highly reactive Al and Fe minerals in the spatial distribution of soil organic biopolymers and SOM sequestration. Copyright © 2015 Elsevier Ltd. All rights reserved.

Clay fractions from a soil chronosequence after glacier retreat reveal the initial evolution of organo-mineral associations

NASA Astrophysics Data System (ADS)

Dümig, Alexander; Häusler, Werner; Steffens, Markus; Kögel-Knabner, Ingrid

2012-05-01

Interactions between organic and mineral constituents prolong the residence time of organic matter in soils. However, the structural organization and mechanisms of organic coverage on mineral surfaces as well as their development with time are still unclear. We used clay fractions from a soil chronosequence (15, 75 and 120 years) in the foreland of the retreating Damma glacier (Switzerland) and from mature soils outside the proglacial area (>700 and <3000 years) to elucidate the evolution of organo-mineral associations during initial soil formation. The chemical composition of the clay-bound organic matter (OM) was assessed by solid-state 13C NMR spectroscopy while the quantities of amino acids and neutral sugar monomers were determined after acid hydrolysis. The mineral phase was characterized by X-ray diffraction, oxalate extraction, specific surface area by N2 adsorption (BET approach), and cation exchange capacity at pH 7 (CECpH7). The last two methods were applied before and after H2O2 treatment. We found pronounced shifts in quantity and quality of OM during aging of the clay fractions, especially within the first one hundred years of soil formation. The strongly increasing organic carbon (OC) loading of clay-sized particles resulted in decreasing specific surface areas (SSA) of the mineral phases and increasing CECpH7. Thus, OC accumulation was faster than the supply of mineral surfaces and cation exchange capacity was mainly determined by the OC content. Clay-bound OC of the 15-year-old soils showed high proportions of carboxyl C and aromatic C. This may point to remnants of ancient OC which were inherited from the recently exposed glacial till. With increasing age (75 and 120 years), the relative proportions of carboxyl and aromatic C decreased. This was associated with increasing O-alkyl C proportions, whereas accumulation of alkyl C was mainly detected in clay fractions from the mature soils. These findings from solid-state 13C NMR spectroscopy are in line with the increasing amounts of microbial-derived carbohydrates with soil age. The large accumulation of proteins, which was comparable to those of carbohydrates, and the very low C/N ratios of H2O2-resistant OM indicated strong and preferential associations between proteinaceous compounds and mineral surfaces. In the acid soils, poorly crystalline Fe oxides were the main providers of mineral surface area and important for the stabilization of OM during aging of the clay fractions. This was indicated by (I) the strong correlations between oxalate soluble Fe and both, SSA of H2O2-treated clay fractions and OC content, and (II) the low formation of expandable clays due to small extents of mineral weathering. Our chronosequence approach provided new insights into the evolution of organo-mineral interactions in acid soils. The formation of organo-mineral associations started with the sorption of proteinaceous compounds and microbial-derived carbohydrates on mineral surfaces which were mainly provided by ferrihydrite. The sequential accumulation of different organic compounds and the large OC loadings point to multiple accretion of OM in distinct zones or layers during the initial evolution of clay fractions.

Biotransformation of tetrabromobisphenol A (TBBPA) in anaerobic digester sludge, soils, and freshwater sediments.

PubMed

McAvoy, Drew C; Pittinger, Charles A; Willis, Alison M

2016-09-01

The biotransformation of tetrabromobisphenol A (TBBPA) was evaluated in anaerobic digester sludge, soils, and freshwater sediments. In anaerobic digester sludge, TBBPA biotransformed rapidly with a 50% disappearance time (DT50) of 19 days, though little mineralization (1.1%) was observed. In aerobic soils, mineralization of TBBPA ranged from 17.5% to 21.6% with 55.3-83.6% of the TBBPA incorporated into the soils as a non-extractable bound residue. The DT50 for TBBPA in aerobic soils ranged from 5.3 to 7.7 days. In anaerobic soils, 48.3-100% of the TBBPA was incorporated into the soils as non-extractable bound residue with <4% mineralized. The soil fate studies demonstrated extensive incorporation of TBBPA into the solid matrix and this association was related to the amount of organic carbon in the soils (i.e., greater association of TBBPA with soil at higher organic carbon content). In anaerobic sediments the DT50 for TBBPA ranged from 28 to 42 days, whereas in aerobic sediments the DT50 for TBBPA ranged from 48 to 84 days and depended on the initial dose concentration. Most of the TBBPA in the sediment studies was incorporated as a non-extractable bound residue with little mineralization observed. Sediment extracts revealed three unknown biotransformation products and bisphenol A (BPA). These results were consistent with previously published studies where TBBPA biotransformed in anaerobic environments (digester sludge and sediments) by debromination and slowly mineralized in the test environments (anaerobic digester sludge, soils, and freshwater sediments). Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Spatial arrangement of organic compounds on a model mineral surface: implications for soil organic matter stabilization.

PubMed

Petridis, Loukas; Ambaye, Haile; Jagadamma, Sindhu; Kilbey, S Michael; Lokitz, Bradley S; Lauter, Valeria; Mayes, Melanie A

2014-01-01

The complexity of the mineral-organic carbon interface may influence the extent of stabilization of organic carbon compounds in soils, which is important for global climate futures. The nanoscale structure of a model interface was examined here by depositing films of organic carbon compounds of contrasting chemical character, hydrophilic glucose and amphiphilic stearic acid, onto a soil mineral analogue (Al2O3). Neutron reflectometry, a technique which provides depth-sensitive insight into the organization of the thin films, indicates that glucose molecules reside in a layer between Al2O3 and stearic acid, a result that was verified by water contact angle measurements. Molecular dynamics simulations reveal the thermodynamic driving force behind glucose partitioning on the mineral interface: The entropic penalty of confining the less mobile glucose on the mineral surface is lower than for stearic acid. The fundamental information obtained here helps rationalize how complex arrangements of organic carbon on soil mineral surfaces may arise.

Estructura y química del suelo en un bosque de Castilla elastica en el carso del norte de Puerto Rico: resultados de una calicata

Treesearch

Christian A. Viera Martinez; Oscar Abelleira; Ariel E. Lugo

2008-01-01

We dug a soil pit of 1m x 1m x 1m in a forest dominated by Castilla elastica, a tree for shade coffee introduced in the karst of northern Puerto Rico. We found four soil horizons (designation notes in parenthesis) (A) organic soil matter (E) mineral soil leachate (B) aerobic mineral soil, and (C) saturated soil. The total storage of soil organic matter was 143 Mg/ha....

Soil processes at Emerald Lake Watershed. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lund, L.J.; Brown, A.D.; Lueking, M.A.

1987-04-20

The objectives of the Soils Processes research at Emerald Lake Watershed (ELW) were to assess physical, chemical and biological processes contributing to the production or consumption of acidity in soils and to assess the net effect of soil processes on surface-water quality in an alpine watershed. Most of the N and S in ELW soils is stored in organic forms. Most of the soil P is present in nearly insoluble mineral forms. The ELW soils can adsorb only small quantities of sulfate, thus their capacity for buffering acid additions by sulfate adsorption is low. Concentrations of Al, Ca, Mg, K,more » and Na in both soil solution and stream samples reflected patterns of mineral weathering in the watershed. Summer CO/sub 2/ concentrations in the soils were high enough to increase soil solution acidity and influence the speciation of dissolved elements. The overall chemistry of stream waters reflects the mineral composition of soils and rocks at ELW.« less

Lunar soil evolution processes and Apollo 16 core 60013/60014

NASA Astrophysics Data System (ADS)

Basu, A.; McKay, D. S.

1995-03-01

Soils of the 62-cm deep Apollo 16 double drive tube 60013/14 are mature at the top and submature at the bottom. Modal analyses of 5529 grains from the 90-150 um and the 500-1000 m fractions from 12 levels of the core show that, in general, agglutinate abundance increases somewhat monotonically to the top and mimics the Is/FeO profile. There is a general decrease in the modal abundance of monomineralic fragments towards the top, suggesting that agglutinates were formed in part at the expense of monomineralic grains, especially feldspars, which are by far the most abundant mineral in these soils. In detail, the top 27 cm of the core differs from the bottom 21 cm, and the middle 14 cm is intermediate in its properties. In the upper segment, variations in the abundances of feldspars correspond with those of feldspathic fragmental breccias and cataclastic anorthosites; in the bottom segment, a similar but weak correspondence between feldspars and crystalline matrix breccias is observed. Mixing of the comminuted products of these three rock types likely produced the bulk of the core material. Many single feldspars in all size fractions are remarkably fresh, show no damage from shock, and are similar in appearance to the large feldspars in anorthosites and feldspathic fragmental breccias, which we consider to be the primary sources of single feldspars in this core. Major (Na, Al, Si, K, Ca) and minor (Fe, Ba) element analyses of 198 single feldspar grains indicate the presence of only one population of feldspars, which is consistent with our interpretation of feldspar provenance. Classification of 890 monomineralic feldspar, olivine, pyroxene, and glass spherules on the basis of the presence or absence of thin brownish coating related to reworking at the surface-shows that coated grains are much more abundant in the top segment than in the bottom segment. A comparison with the mixing and maturation model (McKay et al., 1977) of soils in the core 60009/10, some 60 m away from 60013/14, shows that mixtures of an immature, nearly pure plagioclase soil (dominant in 60009/10) and another immature, crystalline breccia-rich soil (dominant in 60013/14) may have matured through in situ reworking to produce the soils under investigation. We conclude that the soils in this core are products of mixing along soil evolution Path 2 of McKay et al. (1974). Superimposed on that soil column is the reworking of the upper part, which has evolved more recently along Path 1. This core thus represents a consanguineous column of the lunar regolith with an upper reworked segment.

Lunar soil evolution processes and Apollo 16 core 60013/60014

NASA Technical Reports Server (NTRS)

Basu, A.; McKay, D. S.

1995-01-01

Soils of the 62-cm deep Apollo 16 double drive tube 60013/14 are mature at the top and submature at the bottom. Modal analyses of 5529 grains from the 90-150 micrometers and the 500-1000 micrometers fractions from 12 levels of the core show that, in general, agglutinate abundance increases somewhat monotonically to the top and mimics the Is/FeO profile. There is a general decrease in the modal abundance of monomineralic fragments towards the top, suggesting that agglutinates were formed in part at the expense of monomineralic grains, especially feldspars, which are by far the most abundant mineral in these soils. In detail, the top 27 cm of the core differs from the bottom 21 cm, and the middle 14 cm is intermediate in its properties. In the upper segment, variations in the abundances of feldspars correspond with those of feldspathic fragmental breccias and cataclastic anorthosites; in the bottom segment, a similar but weak correspondence between feldspars and crystalline matrix breccias is observed. Mixing of the comminuted products of these three rock types likely produced the bulk of the core material. Many single feldspars in all size fractions are remarkably fresh, show no damage from shock, and are similar in appearance to the large feldspars in anorthosites and feldspathic fragmental breccias, which we consider to be the primary sources of single feldspars in this core. Major (Na, Al, Si, K, Ca) and minor (Fe, Ba) element analyses of 198 single feldspar grains indicate the presence of only one population of feldspars, which is consistent with our interpretation of feldspar provenance. Classification of 890 monomineralic feldspar, olivine, pyroxene, and glass spherules on the basis of the presence or absence of thin brownish coating--related to reworking at the surface--shows that coated grains are much more abundant in the top segment than in the bottom segment. A comparison with the mixing and maturation model (McKay et al., 1977) of soils in the core 60009/10, some 60 m away from 60013/14, shows that mixtures of an immature, nearly pure plagioclase soil (dominant in 60009/10) and another immature, crystalline breccia-rich soil (dominant in 60013/14) may have matured through in situ reworking to produce the soils under investigation. We conclude that the soils in this core are products of mixing along soil evolution Path 2 of McKay et al. (1974). Superimposed on that soil column is the reworking of the upper part, which has evolved more recently along Path 1. This core thus represents a consanguineous column of the lunar regolith with an upper reworked segment.

Lunar soil evolution processes and Apollo 16 core 60013/60014.

PubMed

Basu, A; McKay, D S

1995-03-01

Soils of the 62-cm deep Apollo 16 double drive tube 60013/14 are mature at the top and submature at the bottom. Modal analyses of 5529 grains from the 90-150 micrometers and the 500-1000 micrometers fractions from 12 levels of the core show that, in general, agglutinate abundance increases somewhat monotonically to the top and mimics the Is/FeO profile. There is a general decrease in the modal abundance of monomineralic fragments towards the top, suggesting that agglutinates were formed in part at the expense of monomineralic grains, especially feldspars, which are by far the most abundant mineral in these soils. In detail, the top 27 cm of the core differs from the bottom 21 cm, and the middle 14 cm is intermediate in its properties. In the upper segment, variations in the abundances of feldspars correspond with those of feldspathic fragmental breccias and cataclastic anorthosites; in the bottom segment, a similar but weak correspondence between feldspars and crystalline matrix breccias is observed. Mixing of the comminuted products of these three rock types likely produced the bulk of the core material. Many single feldspars in all size fractions are remarkably fresh, show no damage from shock, and are similar in appearance to the large feldspars in anorthosites and feldspathic fragmental breccias, which we consider to be the primary sources of single feldspars in this core. Major (Na, Al, Si, K, Ca) and minor (Fe, Ba) element analyses of 198 single feldspar grains indicate the presence of only one population of feldspars, which is consistent with our interpretation of feldspar provenance. Classification of 890 monomineralic feldspar, olivine, pyroxene, and glass spherules on the basis of the presence or absence of thin brownish coating--related to reworking at the surface--shows that coated grains are much more abundant in the top segment than in the bottom segment. A comparison with the mixing and maturation model (McKay et al., 1977) of soils in the core 60009/10, some 60 m away from 60013/14, shows that mixtures of an immature, nearly pure plagioclase soil (dominant in 60009/10) and another immature, crystalline breccia-rich soil (dominant in 60013/14) may have matured through in situ reworking to produce the soils under investigation. We conclude that the soils in this core are products of mixing along soil evolution Path 2 of McKay et al. (1974). Superimposed on that soil column is the reworking of the upper part, which has evolved more recently along Path 1. This core thus represents a consanguineous column of the lunar regolith with an upper reworked segment.

Mineralizable soil nitrogen as an index of nitrogen availability to forest trees

Treesearch

Robert F. Powers

1980-01-01

Soil N mineralized during 14-day anaerobic incubation at 30°C is evaluated as an index of forest soil fertility and site productivity. Mineralizable soil N determined under standard conditions correlates significantly with N mineralized anaerobically for 6 months in the field, with site index and yield potential of Pinus ponderosa L....

Hydrologic and water quality effects of thinning Loblolly Pine

Treesearch

Johnny M. Grace; R. W. Skaggs; G. M. Chescheir

2006-01-01

Forest operations such as harvesting, thinning, and site preparation can affect the hydrologic behavior of watersheds on poorly drained soils. The influence of these operations conducted on organic soil sites can be more pronounced than on mineral soil sites due to the differences in bulk density and soil moisture relationships that exist between mineral and organic...

Comparing Methods for Assessing Forest Soil Net Nitrogen Mineralization and Net Nitrification

Treesearch

S. S. Jefts; I. J. Fernandez; L.E. Rustad; D. B. Dail

2004-01-01

A variety of analytical techniques are used to evaluate rates of nitrogen (N) mineralization and nitrification in soils. The diversity of methods takes on added significance in forest ecosystem research where high soil heterogeneity and multiple soil horizons can make comparisons over time and space even more complex than in agricultural Ap horizons. This study...

Flood quantiles scaling with upper soil hydraulic properties for different land uses at catchment scale

NASA Astrophysics Data System (ADS)

Peña, Luis E.; Barrios, Miguel; Francés, Félix

2016-10-01

Changes in land use within a catchment are among the causes of non-stationarity in the flood regime, as they modify the upper soil physical structure and its runoff production capacity. This paper analyzes the relation between the variation of the upper soil hydraulic properties due to changes in land use and its effect on the magnitude of peak flows: (1) incorporating fractal scaling properties to relate the effect of the static storage capacity (the sum of capillary water storage capacity in the root zone, canopy interception and surface puddles) and the upper soil vertical saturated hydraulic conductivity on the flood regime; (2) describing the effect of the spatial organization of the upper soil hydraulic properties at catchment scale; (3) examining the scale properties in the parameters of the Generalized Extreme Value (GEV) probability distribution function, in relation to the upper soil hydraulic properties. This study considered the historical changes of land use in the Combeima River catchment in South America, between 1991 and 2007, using distributed hydrological modeling of daily discharges to describe the hydrological response. Through simulation of land cover scenarios, it was demonstrated that it is possible to quantify the magnitude of peak flows in scenarios of land cover changes through its Wide-Sense Simple Scaling with the upper soil hydraulic properties.

Combined use of microbial consortia isolated from different agricultural soils and cyclodextrin as a bioremediation technique for herbicide contaminated soils.

PubMed

Villaverde, J; Rubio-Bellido, M; Lara-Moreno, A; Merchan, F; Morillo, E

2018-02-01

The phenylurea herbicide diuron is persistent in soil, water and groundwater and is considered to be a highly toxic molecule. The principal product of its biodegradation, 3,4-dichloroaniline, exhibits greater toxicity than diuron and is persistent in the environment. Five diuron degrading microbial consortia (C1C5), isolated from different agricultural soils, were investigated for diuron mineralization activity. The C2 consortium was able to mineralize 81.6% of the diuron in solution, while consortium C3 was only able to mineralize 22.9%. Isolated consortia were also tested in soil slurries and in all cases, except consortium C4, DT 50 (the time required for the diuron concentration to decline to half of its initial value) was drastically reduced, from 700 days (non-inoculated control) to 546, 351, and 171 days for the consortia C5, C2, and C1, respectively. In order to test the effectiveness of the isolated consortium C1 in a more realistic scenario, soil diuron mineralization assays were performed under static conditions (40% of the soil water-holding capacity). A significant enhancement of diuron mineralization was observed after C1 inoculation, with 23.2% of the herbicide being mineralized in comparison to 13.1% for the control experiment. Hydroxypropyl-β-cyclodextrin, a biodegradable organic enhancer of pollutant bioavailability, used in combination with C1 bioaugmentation in static conditions, resulted in a significant decrease in the DT 50 (214 days; 881 days, control experiment). To the best of our knowledge, this is the first report of the use of soil-isolated microbial consortia in combination with cyclodextrins proposed as a bioremediation technique for pesticide contaminated soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessing the use of composts from multiple sources based on the characteristics of carbon mineralization in soil.

PubMed

Zhang, Xu; Zhao, Yue; Zhu, Longji; Cui, Hongyang; Jia, Liming; Xie, Xinyu; Li, Jiming; Wei, Zimin

2017-12-01

In order to improve soil quality, reduce wastes and mitigate climate change, it is necessary to understand the balance between soil organic carbon (SOC) accumulation and depletion under different organic waste compost amended soils. The effects of proportion (5%, 15%, 30%), compost type (sewage sludge (SS), tomato stem waste (TSW), municipal solid waste (MSW), kitchen waste (KW), cabbage waste (CW), peat (P), chicken manure (CM), dairy cattle manure (DCM)) and the black soil (CK). Their initial biochemical composition (carbon, nitrogen, C:N ratio) on carbon (C) mineralization in soil amended compost have been investigated. The CO 2 -C production of different treatments were measured to indicate the levels of carbon (C) mineralization during 50d of laboratory incubation. And the one order E model (M1E) was used to quantify C mineralization kinetics. The results demonstrated that the respiration and C mineralization of soil were promoted by amending composts. The C mineralization ability increased when the percentage of compost added to the soil also increased and affected by compost type in the order CM>KW, CW>SS, DCM, TSW>MSW, P>CK at the same amended level. Based on the values of C 0 and k 1 from M1E model, a management method in agronomic application of compost products to the precise fertilization was proposed. The SS, DCM and TSW composts were more suitable in supplying fertilizer to the plant. Otherwise, The P and MSW composts can serve the purpose of long-term nutrient retention, whereas the CW and KW composts could be used as soil remediation agent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Variations in the patterns of soil organic carbon mineralization and microbial communities in response to exogenous application of rice straw and calcium carbonate.

PubMed

Feng, Shuzhen; Huang, Yuan; Ge, Yunhui; Su, Yirong; Xu, Xinwen; Wang, Yongdong; He, Xunyang

2016-11-15

The addition of exogenous inorganic carbon (CaCO3) and organic carbon has an important influence on soil organic carbon (SOC) mineralization in karst soil, but the microbial mechanisms underlying the SOC priming effect are poorly understood. We conducted a 100-day incubation experiment involving four treatments of the calcareous soil in southwestern China's karst region: control, (14)C-labeled rice straw addition, (14)C-labeled CaCO3 addition, and a combination of (14)C-labeled rice straw and CaCO3. Changes in soil microbial communities were characterized using denaturing gradient gel electrophoresis with polymerase chain reaction (PCR-DGGE) and real-time quantitative PCR (q-PCR). Both (14)C-rice straw and Ca(14)CO3 addition stimulated SOC mineralization, suggesting that organic and inorganic C affected SOC stability. Addition of straw alone had no significant effect on bacterial diversity; however, when the straw was added in combination with calcium carbonate, it had an inhibitory effect on bacterial and fungal diversity. At the beginning of the experimental period, exogenous additives increased bacterial abundance, although at the end of the 100-day incubation bacterial community abundance had gradually declined. Incubation time, exogenous input, and their interaction significantly affected SOC mineralization (in terms of priming and the cumulative amount of mineralization), microbial biomass carbon (MBC), and microbial community abundance and diversity. Moreover, the key factors influencing SOC mineralization were MBC, bacterial diversity, and soil pH. Overall, these findings support the view that inorganic C is involved in soil C turnover with the participation of soil microbial communities, promoting soil C cycling in the karst region. Copyright © 2016 Elsevier B.V. All rights reserved.

Vadose Zone Nitrate Transport Dynamics Resulting from Agricultural Groundwater Banking

NASA Astrophysics Data System (ADS)

Murphy, N. P.; McLaughlin, S.; Dahlke, H. E.

2017-12-01

In recent years, California's increased reliance on groundwater resources to meet agricultural and municipal demands has resulted in significant overdraft and water quality issues. Agricultural groundwater banking (AGB) has emerged as a promising groundwater replenishment opportunity in California; AGB is a form of managed aquifer recharge where farmland is flooded during the winter using excess surface water in order to recharge the underlying groundwater. Suitable farmland that is connected to water delivery systems is available for AGB throughout the Central Valley. However, questions remain how AGB could be implemented on fertilized agricultural fields such that nitrate leaching from the root zone is minimized. Here, we present results from field and soil column studies that investigate the transport dynamics of nitrogen in the root and deeper vadose zone during flooding events. We are specifically interested in estimating how timing and duration of flooding events affect percolation rates, leaching and nitrification/denitrification processes in three soil types within the Central Valley. Laboratory and field measurements include nitrogen (NO3-, NH4+, NO2-, N2O), redox potentials, total organic carbon, dissolved oxygen, moisture content and EC. Soil cores are collected in the field before and after recharge events up to a depth of 4m, while other sensors monitor field conditions continuously. Preliminary results from the three field sites show that significant portions of the applied floodwater (12-62 cm) infiltrated below the root zone: 96.1% (Delhi), 88.6% (Modesto) and 76.8% (Orland). Analysis of the soil cores indicate that 70% of the residual nitrate was flushed from the sandy soil, while the fine sandy loam showed only a 5% loss and in some cores even an increase in soil nitrate (in the upper 20cm). Column experiments support these trends and indicate that increases in soil nitrate in the upper root zone might be due to organic nitrogen mineralization and nitrification, facilitated by the added water. The next step will be to use field and laboratory data for the parameterization of the HP1 (Coupled Hydrus-1D and PHREEQC) model to develop an understanding of nitrogen transport in differing soil textures, and develop best management practices for future AGB projects.

Bioavailable Carbon and the Relative Degradation State of Organic Matter in Active Layer and Permafrost Soils

NASA Astrophysics Data System (ADS)

Jastrow, J. D.; Burke, V. J.; Vugteveen, T. W.; Fan, Z.; Hofmann, S. M.; Lederhouse, J. S.; Matamala, R.; Michaelson, G. J.; Mishra, U.; Ping, C. L.

2015-12-01

The decomposability of soil organic carbon (SOC) in permafrost regions is a key uncertainty in efforts to predict carbon release from thawing permafrost and its impacts. The cold and often wet environment is the dominant factor limiting decomposer activity, and soil organic matter is often preserved in a relatively undecomposed and uncomplexed state. Thus, the impacts of soil warming and permafrost thaw are likely to depend at least initially on the genesis and past history of organic matter degradation before its stabilization in permafrost. We compared the bioavailability and relative degradation state of SOC in active layer and permafrost soils from Arctic tundra in Alaska. To assess readily bioavailable SOC, we quantified salt (0.5 M K2SO4) extractable organic matter (SEOM), which correlates well with carbon mineralization rates in short-term soil incubations. To assess the relative degradation state of SOC, we used particle size fractionation to isolate fibric (coarse) from more degraded (fine) particulate organic matter (POM) and separated mineral-associated organic matter into silt- and clay-sized fractions. On average, bulk SOC concentrations in permafrost were lower than in comparable active layer horizons. Although SEOM represented a very small proportion of the bulk SOC, this proportion was greater in permafrost than in comparable active layer soils. A large proportion of bulk SOC was found in POM for all horizons. Even for mineral soils, about 40% of bulk SOC was in POM pools, indicating that organic matter in both active layer and permafrost mineral soils was relatively undecomposed compared to typical temperate soils. Not surprisingly, organic soils had a greater proportion of POM and mineral soils had greater silt- and clay-sized carbon pools, while cryoturbated soils were intermediate. For organic horizons, permafrost organic matter was generally more degraded than in comparable active layer horizons. However, in mineral and cryoturbated horizons, the presence of permafrost appeared to have little effect on SOC distribution among size fractions. Future studies will investigate the utility of using organic matter pools defined by SEOM and particle size to predict the bioavailable pools characterized through more time-consuming long-term incubation studies of permafrost region soils.

Complementary models of tree species-soil relationships in old-growth temperate forests

USGS Publications Warehouse

Cross, Alison; Perakis, Steven S.

2011-01-01

Ecosystem level studies identify plant soil feed backs as important controls on soil nutrient availability,particularly for nitrogen and phosphorus. Although site and species specific studies of tree species soil relationships are relatively common,comparatively fewer studies consider multiple coexisting speciesin old-growth forests across a range of sites that vary underlying soil fertility. We characterized patterns in forest floor and mineral soil nutrients associated with four common tree species across eight undisturbed old-growth forests in Oregon, USA, and used two complementary conceptual models to assess tree species soil relationships. Plant soil feedbacks that could reinforce sitelevel differences in nutrient availability were assessed using the context dependent relationships model, where by relative species based differences in each soil nutrient divergedorconvergedas nutrient status changed across sites. Tree species soil relationships that did not reflect strong feedbacks were evaluated using a site independent relationships model, where by forest floor and surface mineral soil nutrient tools differed consistently by tree species across sites,without variation in deeper mineral soils. We found that theorganically cycled elements carbon, nitrogen, and phosphorus exhibited context-dependent differences among species in both forest floor and mineral soil, and most of ten followed adivergence model,where by species differences were greatest at high-nutrient sites. These patterns are consistent with the oryemphasizing biotic control of these elements through plant soil feedback mechanisms. Site independent species differences were strongest for pool so if the weather able cations calcium, magnesium, potassium,as well as phosphorus, in mineral soils. Site independent species differences in forest floor nutrients we reattributable too nespecies that displayed significant greater forest floor mass accumulation. Our finding confirmed that site-independent and context-dependent tree species-soil relationships occur simultaneouslyinold-grow the temperate forests, with context-dependent relationships strongest for organically cycled elements, and site-independent relationships strongest for weather able elements with in organic cycling phases. These models provide complementary explanations for patterns of nutrient accumulation and cycling in mixed species old-growth temperate forests.

DEVELOPMENT OF MULTI-PHASE AND MULTI-COMPONENT FLOW MODEL WITH REACTION IN POROUS MEDIA FOR RISK ASSESSMENT ON SOIL CONTAMINATION DUE TO MINERAL OIL

NASA Astrophysics Data System (ADS)

Sakamoto, Yasuhide; Nishiwaki, Junko; Hara, Junko; Kawabe, Yoshishige; Sugai, Yuichi; Komai, Takeshi

In late years, soil contamination due to mineral oil in vacant lots of oil factory and oil field has become obvious. Measure for soil contamina tion and risk assessment are neces sary for sustainable development of industrial activity. Especially, in addition to contaminated sites, various exposure paths for human body such as well water, soil and farm crop are supposed. So it is very important to comprehend the transport phenomena of contaminated material under the environments of soil and ground water. In this study, mineral oil as c ontaminated material consisting of mu lti-component such as aliphatic and aromatic series was modeled. Then numerical mode l for transport phenomena in surface soil and aquifer was constructed. On the basis of modeling for mineral oil, our numerical model consists of three-phase (oil, water and gas) forty three-component. This numerical model becomes base program for risk assessment system on soil contamination due to mineral oil. Using this numerical model, we carried out some numerical simulation for a laboratory-scale experiment on oil-water multi-phase flow. Relative permeability that dominate flow behavior in multi-phase condition was formulated and the validity of the numerical model developed in this study was considered.

A kinetic approach to evaluate salinity effects on carbon mineralization in a plant residue-amended soil*

PubMed Central

Nourbakhsh, Farshid; Sheikh-Hosseini, Ahmad R.

2006-01-01

The interaction of salinity stress and plant residue quality on C mineralization kinetics in soil is not well understood. A laboratory experiment was conducted to study the effects of salinity stress on C mineralization kinetics in a soil amended with alfalfa, wheat and corn residues. A factorial combination of two salinity levels (0.97 and 18.2 dS/m) and four levels of plant residues (control, alfalfa, wheat and corn) with three replications was performed. A first order kinetic model was used to describe the C mineralization and to calculate the potentially mineralizable C. The CO2-C evolved under non-saline condition, ranged from 814.6 to 4842.4 mg CO2-C/kg in control and alfalfa residue-amended soils, respectively. Salinization reduced the rates of CO2 evolution by 18.7%, 6.2% and 5.2% in alfalfa, wheat and corn residue-amended soils, respectively. Potentially mineralizable C (C 0) was reduced significantly in salinized alfalfa residue-treated soils whereas, no significant difference was observed for control treatments as well as wheat and corn residue-treated soils. We concluded that the response pattern of C mineralization to salinity stress depended on the plant residue quality and duration of incubation. PMID:16972320

Schwertmannite stability in acidified coastal environments

NASA Astrophysics Data System (ADS)

Collins, Richard N.; Jones, Adele M.; Waite, T. David

2010-01-01

A combination of analytical and field measurements has been used to probe the speciation and cycling of iron in coastal lowland acid sulfate soils. Iron K-edge EXAFS spectroscopy demonstrated that schwertmannite dominated (43-77%) secondary iron mineralization throughout the oxidized and acidified soil profile, while pyrite and illite were the major iron-bearing minerals in the reduced potential acid sulfate soil layers. Analyses of contemporary precipitates from shallow acid sulfate soil groundwaters indicated that 2-line ferrihydrite, in addition to schwertmannite, is presently controlling secondary Fe(III) mineralization. Although aqueous pH values and concentrations of Fe(II) were seasonally high, no evidence was obtained for the Fe(II)-catalyzed crystallization of either mineral to goethite. The results of this study indicate that: (a) schwertmannite is likely to persist in coastal lowland acid sulfate soils on a much longer time-scale than predicted by laboratory experiments; (b) this mineral is less reactive in these types of soils due to surface-site coverage by components such as silicate and possibly, to a lesser extent, natural organic matter and phosphate and; (c) active water table management to promote oxic/anoxic cycles around the Fe(II)-Fe(III) redox couple, or reflooding of these soils, will be ineffective in promoting the Fe(II)-catalyzed transformation of either schwertmannite or 2-line ferrihydrite to crystalline iron oxyhydroxides.

Soil moisture influenced the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

NASA Astrophysics Data System (ADS)

Zhang, Y.; Guo, S.; Zhao, M.; Du, L.; Li, R.; Jiang, J.; Wang, R.; Li, N.

2015-01-01

Temperature sensitivity of SOC mineralization (Q10) determines how strong the feedback from global warming may be on the atmospheric CO2 concentration, thus understanding the factors influencing the interannual variation in Q10 is important to accurately estimate the local soil carbon cycle. In situ SOC mineralization was measured using an automated CO2 flux system (Li-8100) in long-term bare fallow soil in the Loess Plateau (35° 12' N, 107° 40' E) in Changwu, Shaanxi, China form 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m-2 y-1 (mean =253 g C m-2 y-1; CV =13%), annual Q10 ranged from 1.48 to 1.94 (mean =1.70; CV =10%), and annual soil moisture content ranged from 38.6 to 50.7% WFPS (mean =43.8% WFPS; CV =11%), which were mainly affected by the frequency and distribution of precipitation. Annual Q10 showed a negative quadratic correlation with soil moisture. In conclusion, understanding of the relationships between interannual variation in Q10 of SOC mineralization, soil moisture and precipitation is important to accurately estimate the local carbon cycle, especially under the changing climate.

Directing Traffic in the Rhizosphere: Using Isotopes and Imaging to Track Root-Microbe-Mineral Interactions in Soil

NASA Astrophysics Data System (ADS)

Pett-Ridge, J.; Neurath, R.; Whitman, T.; Zhang, P.; Yuan, T.; Zhou, J.; Nico, P. S.; Lipton, A.; Weber, P. K.; Firestone, M.

2016-12-01

Stimulated by exudates and root decay, rhizosphere organisms control the critical pathways that move C from root tissues to mineral surfaces, and ultimately regulate how soil C is sequestered and stabilized. Yet we have a poor understanding of how roots affect the molecular ecology of microbial decomposers, and how this affects rates of organic matter breakdown or long-term OM association with minerals. In an isotope-enabled incubation experiment, we studied SOM-mineral interactions and the colonization of fresh minerals by soil microbes asking: (1) How does mineralogy impact SOM association? (2) who is there (which microbial taxa), (3) what chemical form the C is in, and (4) where C is associated within the soil physical environment. We followed the fate of 13C-labeled plant-derived C in Avena barbata (wild oat) California grassland soil microcosms incubated with three minerals representing a spectrum of structure and reactivity: quartz, kaolinite, and ferrihydrite-coated quartz. These minerals (isolated in mesh bags to exclude plant roots but not microorganisms) were extracted and measured for total C and 13C atom% after 1, 2, and 2.5 months incubation. We used sequencing of 16S and ITS2 genes and qPCR to characterize the microbial communities colonizing the minerals. At plant senescence, quartz had the least mineral-bound C and ferrihydrite the most. Ferrihydrite and kaolinite also accumulated more plant-derived C. Fourier Transform Infrared Spectroscopy and 13C-Nuclear Magnetic Resonance Spectroscopy analysis of the mineral-associated SOM indicated differences in the SOM composition with mineralogy. Bacterial and fungal communities associated with different minerals differed, with more arbuscular mycorrhial fungi found on ferrihydrite and quartz. Nanoscale secondary ion mass spectrometry (NanoSIMS) imaging of these minerals suggested that fungal hyphae moved C directly from roots to mineral surfaces. Additionally, mineral-associated microbes had an enriched capacity for traits such as predation, N-fixation, faunal symbiosis, parasitism, and fast growth. Our findings suggest that roots impact organic C interactions with minerals, resulting in distinct microbe-SOM-mineral associations as well as differing chemical characteristics of SOM-mineral interactions.

Microfluidic Leaching of Soil Minerals: Release of K+ from K Feldspar

PubMed Central

Ciceri, Davide; Allanore, Antoine

2015-01-01

The rate of K+ leaching from soil minerals such as K-feldspar is believed to be too slow to provide agronomic benefit. Currently, theories and methods available to interpret kinetics of mineral processes in soil fail to consider its microfluidic nature. In this study, we measure the leaching rate of K+ ions from a K-feldspar-bearing rock (syenite) in a microfluidic environment, and demonstrate that at the spatial and temporal scales experienced by crop roots, K+ is available at a faster rate than that measured with conventional apparatuses. We present a device to investigate kinetics of mineral leaching at an unprecedented simultaneous resolution of space (~101-102 μm), time (~101-102 min) and fluid volume (~100-101 mL). Results obtained from such a device challenge the notion that silicate minerals cannot be used as alternative fertilizers for tropical soils. PMID:26485160

ForCent model development and testing using the Enriched Background Isotope Study experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parton, W.J.; Hanson, P. J.; Swanston, C.

The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool {sup 14}C signature ({Delta} {sup 14}C) data from the Enriched Background Isotope Study {sup 14}C experiment (1999-2006) shows that the model correctly simulatesmore » the temporal dynamics of the {sup 14}C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass {Delta} {sup 14}C data, and with soil respiration {Delta} {sup 14}C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study {sup 14}C experimental treatments on soil respiration {Delta} {sup 14}C values for the different soil organic matter pools. Model results suggest that a two-pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.« less

ForCent Model Development and Testing using the Enriched Background Isotope Study (EBIS) Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parton, William; Hanson, Paul J; Swanston, Chris

The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool 14C signature (? 14C) data from the Enriched Background Isotope Study 14C experiment (1999-2006) shows that the model correctly simulates the temporal dynamicsmore » of the 14C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass ? 14C data, and with soil respiration ? 14C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study 14C experimental treatments on soil respiration ? 14C values for the different soil organic matter pools. Model results suggest that a two-pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.« less

Carbon and nitrogen pools and mineralization rates in boreal forest soil after stump harvesting

NASA Astrophysics Data System (ADS)

Kaarakka, Lilli; Hyvönen, Riitta; Strömgren, Monika; Palviainen, Marjo; Persson, Tryggve; Olsson, Bengt A.; Helmisaari, Heljä-Sisko

2016-04-01

The use of forest-derived biomass has steadily increased in the Finland and Sweden during the past decades. Thus, more intensive forest management practices are becoming more common in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting causes a direct removal of carbon (C) in the form of biomass from the stand and can cause extensive soil disturbance, which in turn can result in increased C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied at two different clear-felled Norway spruce (Picea abies) stands in Central Finland. The treatments were conventional stem-only harvesting combined with mounding (WTH) and stump harvesting (i.e. complete tree harvesting) combined with mounding (WTH+S). Logging residues were removed from all study sites. Soil samples down to a depth of 20 cm were systematically collected from the different soil disturbance surfaces (undisturbed soil, the mounds and the pits) 12-13 years after final harvest. Soil samples were incubated in the laboratory to determine the C and N mineralization rates. In addition, total C and N pools were estimated for each disturbance class and soil layer. Soil C and N pools were lower following stump harvesting, however, no statistically significant treatment effect was detected. Instead, C mineralization responses to treatment intensity was site-specific. C/N-ratio and organic matter content were significantly affected by harvest intensity. The observed changes in C and N pools appear to be related to the intrinsic variation of the surface disturbance and soil characteristics, and harvesting per se, rather than treatment intensity. Long-term studies are however needed to draw long-term conclusions whether stump harvesting significantly changes soil C and nutrient dynamics.

Effects of carbon-based nanoparticles (CNPs) on the fate of endocrine disrupting chemicals (EDCs) in different agricultural soils.

NASA Astrophysics Data System (ADS)

Stumpe, Britta; Wolski, Sabrina; Marschner, Bernd

2013-04-01

Nanotechnology is a major innovative scientific and economic growth area. To date there is a lack about possible adverse effects that may be associated with manufactured nanomaterial in terrestrial environments. Since it is known that on the one hand carbon-based nanoparticles (CNPs) and endocrine disrupting chemicals (EDCs) strongly interact in wastewater and that on the other hand CNPs and EDCs are released together via wastewater irrigation to agricultural soils, knowledge of CNP effects on the EDC fate in the soil environment is needed for further risk assessments. The overall goal of this project is to gain a better understanding of interaction of CNPs with EDCs within the soil system. Three different soil samples were applied with different CNPs, EDCs and CNP-EDC complexes and incubated over a period of 6 weeks. The EDC mineralization as well as their uptake by soil microorganisms was monitored to describe impacts of the nanomaterial on the EDC fate. As quality control for the biological soil activity soil respiration, enzyme activities and the soil microbial biomass were monitored in all incubated soil samples. Clearly, EDCs bound in CNP complexes showed a decrease in mineralization. While the free EDCs showed a total mineralization of 34 to 45 %, the nano complexed EDCs were only mineralized to 12 to 15 %. Since no effects of the nanomaterial on the biological soil activity were observed, we conclude that the reduced EDC mineralization is directly linked to their interaction with the CNPs. Since additionally the EDC adsorption to CNPs reduced the EDC uptake by soil microorganism, we assume that CNPs generally form more or less recalcitrant aggregates which likely protect the associated EDCs from degradation.

Increased Calcium Availability Leads to Greater Forest Floor Accumulation in an Adirondack Forest

NASA Astrophysics Data System (ADS)

Melvin, A.; Goodale, C. L.

2010-12-01

Nutrient availability in Northeastern US forests has been dramatically altered by anthropogenic activities. Acid deposition has not only increased nitrogen (N) availability, but has also been linked to soil acidification and a loss of base cations, largely calcium (Ca). We are studying the long-term effects of a Ca addition on carbon (C) and N cycling in a forested catchment in the Adirondack Park, New York. In 1989, calcium carbonate (lime) was added to two subcatchments within the Woods Lake Watershed to ameliorate the effects of soil Ca depletion. Two additional subcatchments were left as controls. Eighteen years after the Ca application, both soil pH and exchangeable Ca concentrations remain elevated in the organic horizons and upper mineral soils of the treated subcatchments. The forest floor mass in this watershed is very large and measurements show that the organic layer in the limed subcatchments is significantly larger than in the controls (212 t/ha vs. 116 t/ha), resulting in greater C and N stocks in the Ca-amended soils. This finding suggests that Ca may stabilize soil organic matter (SOM), resulting in greater C storage under high soil Ca conditions. We are investigating potential drivers of this SOM accumulation in the limed subcatchments, including rates of leaf litter production and the decomposition rate of forest floor material. This work will provide important insights into how long-term changes in soil Ca availability influence SOM stabilization, retention and nutrient cycling.

Turnover and storage of C and N in five density fractions from California annual grassland surface soils

NASA Astrophysics Data System (ADS)

Baisden, W. T.; Amundson, R.; Cook, A. C.; Brenner, D. L.

2002-12-01

We measured 14C/12C in density fractions from soils collected before and after atmospheric thermonuclear weapons testing to examine soil organic matter (SOM) dynamics along a 3 million year California soil chronosequence. The mineral-free particulate organic matter (FPOM; <1.6 g cm-3) mainly contains recognizable plant material, fungal hyphae, and charcoal. Mineral-associated light fractions (1.6-2.2 g cm-3) display partially or completely humified fine POM, while the dense fraction (>2.2 g cm-3) consists of relatively OM-free sand and OM-rich clays. Three indicators of decomposition (C:N, δ13C, and δ15N) all suggest increasing SOM decomposition with increasing fraction density. The Δ14C-derived SOM turnover rates suggest that ≥90% of FPOM turns over in <10 years. The four mineral-associated fractions contain 69-86% "stabilized" (decadal) SOM with the remainder assumed to be "passive" (millenial) SOM. Within each soil, the four mineral-associated fractions display approximately the same residence time (34-42 years in 200 kyr soil, 29-37 years in 600 kyr soil, and 18-26 years in 1-3 Myr soils), indicating that a single stabilized SOM "pool" exists in these soils and may turn over primarily as a result of soil disruption.

Impact of soil water regime on degradation and plant uptake behaviour of the herbicide isoproturon in different soil types.

PubMed

Grundmann, Sabine; Doerfler, Ulrike; Munch, Jean Charles; Ruth, Bernhard; Schroll, Reiner

2011-03-01

The environmental fate of the worldwide used herbicide isoproturon was studied in four different, undisturbed lysimeters in the temperate zone of Middle Europe. To exclude climatic effects due to location, soils were collected at different regions in southern Germany and analyzed at a lysimeter station under identical environmental conditions. (14)C-isoproturon mineralization varied between 2.59% and 57.95% in the different soils. Barley plants grown on these lysimeters accumulated (14)C-pesticide residues from soil in partially high amounts and emitted (14)CO(2) in an extent between 2.01% and 13.65% of the applied (14)C-pesticide. Plant uptake and (14)CO(2) emissions from plants were inversely linked to the mineralization of the pesticide in the various soils: High isoproturon mineralization in soil resulted in low plant uptake whereas low isoproturon mineralization in soil resulted in high uptake of isoproturon residues in crop plants and high (14)CO(2) emission from plant surfaces. The soil water regime was identified as an essential factor that regulates degradation and plant uptake of isoproturon whereby the intensity of the impact of this factor is strongly dependent on the soil type. Copyright © 2010 Elsevier Ltd. All rights reserved.

Activation of Peroxymonosulfate by Subsurface Minerals.

PubMed

Yu, Miao; Teel, Amy L; Watts, Richard J

2016-08-01

In situ chemical oxidation (ISCO) has become a widely used technology for the remediation of soil and groundwater. Although peroxymonosulfate is not a common oxidant source for ISCO, its chemical structure is similar to the ISCO reagents hydrogen peroxide and persulfate, suggesting that peroxymonosulfate may have the beneficial properties of each of these oxidants. Peroxymonosulfate activation in the presence of subsurface minerals was examined as a basis for ISCO, and possible reactive species (hydroxyl radical, sulfate radical, and reductants+nucleophiles) generated in the mineral-activated peroxymonosulfate systems were investigated. Rates of peroxymonosulfate decomposition and generation rates of reactive species were studied in the presence of three iron oxides, one manganese oxide, and three soil fractions. The iron oxide hematite-activated peroxymonosulfate system most effectively degraded the hydroxyl radical probe nitrobenzene. Reductants+nucleophiles were not generated in mineral-activated peroxymonosulfate systems. Use of the probe compound anisole in conjunction with scavengers demonstrated that both sulfate radical and hydroxyl radical are generated in mineral-activated peroxymonosulfate systems. In order to confirm the activation of peroxymonosulfate by subsurface minerals, one natural soil and associated two soil fractions were evaluated as peroxymonosulfate catalysts. The natural soil did not effectively promote the generation of oxidants; however, the soil organic matter was found to promote the generation of reductants + nucleophiles. The results of this research show that peroxymonosulfate has potential as an oxidant source for ISCO applications, and would be most effective in treating halogenated contaminants when soil organic matter is present in the subsurface. Copyright © 2016. Published by Elsevier B.V.

Resources for a lunar base: Rocks, minerals, and soil of the Moon

NASA Technical Reports Server (NTRS)

Taylor, Lawrence A.

1992-01-01

The rocks and minerals of the Moon will be included among the raw materials used to construct a lunar base. The lunar regolith, the fragmental material present on the surface of the Moon, is composed mostly of disaggregated rocks and minerals, but also includes glassy fragments fused together by meteorite impacts. The finer fraction of the regolith (i.e., less than 1 cm) is informally referred to as soil. The soil is probably the most important portion of the regolith for use at a lunar base. For example, soil can be used as insulation against cosmic rays, for lunar ceramics and abodes, or for growing plants. The soil contains abundant solar-wind-implanted elements as well as various minerals, particularly oxide phases, that are of potential economic importance. For example, these components of the soil are sources of oxygen and hydrogen for rocket fuel, helium for nuclear energy, and metals such as Fe, Al, Si, and Ti.

Carbon Footprint of Biofuel Sugarcane Produced in Mineral and Organic Soils in Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izursa, Jose-Luis; Hanlon, Edward; Amponsah, Nana

2013-02-06

Ethanol produced from sugarcane is an existing and accessible form of renewable energy. In this study, we applied the Life Cycle Assessment (LCA) approach to estimate the Carbon Footprint (CFP) of biofuel sugarcane produced on mineral (sandy) and organic (muck) soils in Florida. CFP was estimated from greenhouse gas (GHG) emissions (CO2, CH4, and N2O) during the biofuel sugarcane cultivation. The data for the energy (fossil fuels and electricity), equipment, and chemical fertilizers were taken from enterprise budgets prepared by the University of Florida based on surveys and interviews obtained from local growers during the cropping years 2007/2008 and 2009/2010more » for mineral soils and 2008/2009 for organic soils. Emissions from biomass burning and organic land use were calculated based on the IPCC guidelines. The results show that the CFP for biofuel sugarcane production is 0.04 kg CO2e kg-1y-1 when produced in mineral soils and 0.46 kg CO2e kg-1y-1 when produced in organic soils. Most of the GHG emissions from production of biofuel sugarcane in mineral soils come from equipment (33%), fertilizers (28%), and biomass burning (27%); whereas GHG emissions from production in organic soils come predominantly from the soil (93%). This difference should be considered to adopt new practices for a more sustainable farming system if biofuel feedstocks are to be considered.« less

Effects of low-level radioactive soil contamination and sterilization on the degradation of radiolabeled wheat straw.

PubMed

Niedrée, Bastian; Vereecken, Harry; Burauel, Peter

2012-07-01

After the explosion of reactor 4 in the nuclear power plant near Chernobyl, huge agricultural areas became contaminated with radionuclides. In this study, we want to elucidate whether (137)Cs and (90)Sr affect microorganisms and their community structure and functions in agricultural soil. For this purpose, the mineralization of radiolabeled wheat straw was examined in lab-scale microcosms. Native soils and autoclaved and reinoculated soils were incubated for 70 days at 20 °C. After incubation, the microbial community structure was compared via 16S and 18S rDNA denaturing gradient gel electrophoresis (DGGE). The radioactive contamination with (137)Cs and (90)Sr was found to have little effect on community structure and no effect on the straw mineralization. The autoclaving and reinoculation of soil had a strong influence on the mineralization and the community structure. Additionally we analyzed the effect of soil treatment on mineralization and community composition. It can be concluded that other environmental factors (such as changing content of dissolved organic carbon) are much stronger regulating factors in the mineralization of wheat straw and that low-level radiation only plays a minor role. Copyright © 2011 Elsevier Ltd. All rights reserved.

Influence of soil properties on the toxicity of TiO₂ nanoparticles on carbon mineralization and bacterial abundance.

PubMed

Simonin, Marie; Guyonnet, Julien P; Martins, Jean M F; Ginot, Morgane; Richaume, Agnès

2015-01-01

Information regarding the impact of low concentration of engineered nanoparticles on soil microbial communities is currently limited and the importance of soil characteristics is often neglected in ecological risk assessment. To evaluate the impact of TiO2 nanoparticles (NPs) on soil microbial communities (measured on bacterial abundance and carbon mineralization activity), 6 agricultural soils exhibiting contrasted textures and organic matter contents were exposed for 90 days to a low environmentally relevant concentration or to an accidental spiking of TiO2-NPs (1 and 500mgkg(-1) dry soil, respectively) in microcosms. In most soils, TiO2-NPs did not impact the activity and abundance of microbial communities, except in the silty-clay soil (high OM) where C-mineralization was significantly lowered, even with the low NPs concentration. Our results suggest that TiO2-NPs toxicity does not depend on soil texture but likely on pH and OM content. We characterized TiO2-NPs aggregation and zeta potential in soil solutions, in order to explain the difference of TiO2-NPs effects on soil C-mineralization. Zeta potential and aggregation of TiO2-NPs in the silty-clay (high OM) soil solution lead to a lower stability of TiO2-NP-aggregates than in the other soils. Further experiments would be necessary to evaluate the relationship between TiO2-NPs stability and toxicity in the soil. Copyright © 2014 Elsevier B.V. All rights reserved.

Climate response of the soil nitrogen cycle in three forest types of a headwater Mediterranean catchment

NASA Astrophysics Data System (ADS)

Lupon, Anna; Gerber, Stefan; Sabater, Francesc; Bernal, Susana

2015-05-01

Future changes in climate may affect soil nitrogen (N) transformations, and consequently, plant nutrition and N losses from terrestrial to stream ecosystems. We investigated the response of soil N cycling to changes in soil moisture, soil temperature, and precipitation across three Mediterranean forest types (evergreen oak, beech, and riparian) by fusing a simple process-based model (which included climate modifiers for key soil N processes) with measurements of soil organic N content, mineralization, nitrification, and concentration of ammonium and nitrate. The model describes sources (atmospheric deposition and net N mineralization) and sinks (plant uptake and hydrological losses) of inorganic N from and to the 0-10 cm soil pool as well as net nitrification. For the three forest types, the model successfully recreated the magnitude and temporal pattern of soil N processes and N concentrations (Nash-Sutcliffe coefficient = 0.49-0.96). Changes in soil water availability drove net N mineralization and net nitrification at the oak and beech forests, while temperature and precipitation were the strongest climatic factors for riparian soil N processes. In most cases, net N mineralization and net nitrification showed a different sensitivity to climatic drivers (temperature, soil moisture, and precipitation). Our model suggests that future climate change may have a minimal effect on the soil N cycle of these forests (<10% change in mean annual rates) because positive warming and negative drying effects on the soil N cycle may counterbalance each other.

Geologic Controls on Geophysics for Tunnel Detection

NASA Astrophysics Data System (ADS)

Kelley, J. R.; Wakeley, L. D.; McKenna, J. R.; Ketcham, S. A.; Weiss, C. A.; Curtis, J. O.

2006-05-01

Properties of soils are critical to using near-surface geophysical techniques to search for clandestine tunnels. We have constructed a database of soils sampled at sites on the northern (N) and southern (S) US borders and at sites in Iraq in conjunction with tunnel searches. Geologic materials at these sites consist of glacial gravels (N), volcanic tuff (S), and alluvial sands interbedded with marine clays (Iraq). The depth of interest for detecting clandestine tunneling is < 30m, and as shallow as 2m at some locations. Mineral composition, grain size, moisture content, conductivity, permittivity, and magnetic susceptibility are critical for assessing the effectiveness of near-surface geophysical techniques. Values for these properties are consistent with soil stratigraphy and with vertical and lateral geologic variability. In some environments, in situ moisture content and the arrangement of conductive and resistive materials in the upper few meters limit significantly the depth of investigation using traditional near-surface techniques (electromagnetic induction, ground-penetrating radar). Geologic factors plus the small physical size of the targets limit the usefulness of commercial off-the-shelf techniques, and warrant an investment in new approaches.

Lunar mineral feedstocks from rocks and soils: X-ray digital imaging in resource evaluation

NASA Technical Reports Server (NTRS)

Chambers, John G.; Patchen, Allan; Taylor, Lawrence A.; Higgins, Stefan J.; Mckay, David S.

1994-01-01

The rocks and soils of the Moon provide raw materials essential to the successful establishment of a lunar base. Efficient exploitation of these resources requires accurate characterization of mineral abundances, sizes/shapes, and association of 'ore' and 'gangue' phases, as well as the technology to generate high-yield/high-grade feedstocks. Only recently have x-ray mapping and digital imaging techniques been applied to lunar resource evaluation. The topics covered include inherent differences between lunar basalts and soils and quantitative comparison of rock-derived and soil-derived ilmenite concentrates. It is concluded that x-ray digital-imaging characterization of lunar raw materials provides a quantitative comparison that is unattainable by traditional petrographic techniques. These data are necessary for accurately determining mineral distributions of soil and crushed rock material. Application of these techniques will provide an important link to choosing the best raw material for mineral beneficiation.

Geology of uranium in the Chadron area, Nebraska and South Dakota

USGS Publications Warehouse

Dunham, Robert Jacob

1961-01-01

The Chadron area covers 375 square miles about 25 miles southeast of the Black Hills. Recurrent mild tectonic activity and erosion on the Chadron arch, a compound anticlinal uplift of regional extent, exposed 1900 feet of Upper Cretaceous rocks, mostly marine shale containing pyrite and organic matter, and 600 feet of Oligocene and Miocene rocks, mostly terrestrial fine-grained sediment containing volcanic ash. Each Cretaceous formation truncated by the sub-Oligocene unconformity is stained yellow and red, leached, kaolinized, and otherwise altered to depths as great as 55 feet. The composition and profile of the altered material indicate lateritic soil; indirect evidence indicates Eocene(?) age. In a belt through the central part of the area, the Brule formation of Oligocene age is a sequence of bedded gypsum, clay, dolomite, and limestone more than 300 feet thick. Uranium in Cretaceous shale in 58 samples averages 0.002 percent, ten times the average for the earths crust. Association with pyrite and organic matter indicates low valency. The uranium probably is syngenetic or nearly so. Uranium in Eocene(?) soil in 43 samples averages 0.054 percent, ranging up to 1.12 percent. The upper part of the soil is depleted in uranium; enriched masses in the basal part of the soil consist of remnants of bedrock shale and are restricted to the highest reaches of the ancient oxidation-reduction interface. The uranium is probably in the from of a low-valent mineral, perhaps uraninite. Modern weathering of Cretaceous shale is capable of releasing as much as 0.780 ppm uranium to water. Eocene(?) weathering probably caused enrichment of the ancient soil through 1) leaching of Cretaceous shale, 2) downward migration of uranyl complex ions, and 3) reduction of hydrogen sulfide at the water table. Uranium minerals occur in the basal 25 feet of the gypsum facies of the Brule formation at the two localities where the gypsum is carbonaceous; 16 samples average 0.066 percent uranium and range up to 0.43 percent. Elsewhere uranium in dolomite and limestone in the basal 25 feet of the gypsum facies in 10 samples averages 0.007 percent, ranging up to 0.12 percent. Localization of the uranium at the base of the gypsum facies suggests downward moving waters; indirect evidence that the water from which the gypsum was deposited was highly alkaline suggests that the uranium was leached from volcanic ash in Oligocene time.

Geochemical evidence for airborne dust additions to soils in Channel Islands National Park, California

USGS Publications Warehouse

Muhs, D.R.; Budahn, J.R.; Johnson, D.L.; Reheis, M.; Beann, J.; Skipp, G.; Fisher, E.; Jones, J.A.

2008-01-01

There is an increasing awareness that dust plays important roles in climate change, biogeochemical cycles, nutrient supply to ecosystems, and soil formation. In Channel Islands National Park, California, soils are clay-rich Vertisols or Alfisols and Mollisols with vertic properties. The soils are overlain by silt-rich mantles that contrast sharply with the underlying clay-rich horizons. Silt mantles contain minerals that are rare or absent in the volcanic rocks that dominate these islands. Immobile trace elements (Sc-Th-La and Ta-Nd-Cr) and rare-earth elements show that the basalt and andesite on the islands have a composition intermediate between upper-continental crust and oceanic crust. In contrast, the silt fractions and, to a lesser extent, clay fractions of the silt mantle have compositions closer to average upper-continental crust and very similar to Mojave Desert dust. Island shelves, exposed during the last glacial period, could have provided a source of eolian sediment for the silt mantles, but this is not supported by mineralogical data. We hypothesize that a more likely source for the silt-rich mantles is airborne dust from mainland California and Baja California, either from the Mojave Desert or from the continental shelf during glacial low stands of sea. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. The eolian silt mantles constitute an important medium of plant growth and provide evidence that abundant eolian silt and clay may be delivered to the eastern Pacific Ocean from inland desert sources. ?? 2007 Geological Society of America.

Crown condition dynamics of oak in southern Sweden 1988-1999.

PubMed

Drobyshev, Igor; Anderson, Stefan; Sonesson, Kerstin

2007-11-01

Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20-30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (> or =4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees > or =100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988-99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.

Characterization of Minerals: From the Classroom to Soils to Talc Deposits

ERIC Educational Resources Information Center

McNamee, Brittani D.

2013-01-01

This dissertation addresses different methods and challenges surrounding characterizing and identifying minerals in three environments: in the classroom, in soils, and in talc deposits. A lab manual for a mineralogy and optical mineralogy course prepares students for mineral characterization and identification by giving them the methods and tools…

Soil CO2 emissions from Northern Andean páramo ecosystems: effects of fallow agriculture.

PubMed

Cabaneiro, Ana; Fernandez, Irene; Pérez-Ventura, Luis; Carballas, Tarsy

2008-03-01

The effects of fallow agriculture on soil organic matter (SOM) dynamics and CO2 emissions were assessed in the tropical Andean páramo ecosystem. Possible changes during the cultivation-fallow cycle were monitored in four areas of the Quebrada Piñuelas valley (Venezuela). Uncultivated soils and plots at different stages of a complete cultivation--fallow cycle were incubated, and SOM mineralization kinetics was determined. Soils exhibited a low SOM mineralization activity, total CO2 evolved never reaching 3% of soil carbon, pointing to a stabilized SOM. Potential soil CO2 effluxes differed significantly according to their plot aspect: northeast (NE)-aspect soils presented higher CO2 effluxes than southwest (SW)-aspect soils. Soil CO2 emissions decreased after ploughing as compared to virgin páramo; low CO2 effluxes were still observed during cropping periods, increasing progressively to reach the highest values after 4-5 y of fallow. In all cases, experimental C mineralization data was fitted to a double exponential kinetic model. High soil labile C pool variability was observed, and two different trends were identified: NE-oriented soils showed more labile C and a wider range of values than SW-facing soils. Labile C positively correlated with CO2 effluxes and negatively with its instantaneous mineralization rate. The instantaneous mineralization rate of the recalcitrant C pool positively correlated with %C evolved as CO2 and negatively with soil C and Al2O3 contents, suggesting the importance of aluminum on SOM stability. The CO2 effluxes from these ecosystems, as well as the proportion of soil C released to the atmosphere, seem to depend not only on the size of the labile C pool but also on the accessibility of the more stabilized SOM. Therefore, fallow agriculture produces moderate changes in SOM quality and temporarily alters the CO2 emission capacity of these soils.

Study of the acid-base properties of mineral soil horizons using pK spectroscopy

NASA Astrophysics Data System (ADS)

Shamrikova, E. V.; Vanchikova, E. V.; Ryazanov, M. A.

2007-11-01

The presence of groups 4 and 5 participating in acid-base equilibria was revealed in samples from mineral horizons of the gley-podzolic soil of the Komi Republic using pK spectroscopy (the mathematical processing of potentiometric titration curves for plotting the distribution of acid groups according to their pK values). The specific quantity of acid-base sites in soil samples was calculated. The contribution of organic and mineral soil components to the groups of acid-base sites was estimated. The pK values of groups determining the potential, exchangeable, and unexchangeable acidities were found. The heterogeneity of acid components determining different types of soil acidity was revealed.

Nitrogen mineralization in aspen/conifer soils after a natural fire

Treesearch

Michael C. Amacher; Dale L. Bartos; Tracy Christopherson; Amber D. Johnson; Debra E. Kutterer

2001-01-01

We measured the effects of the 1996 Pole Creek fire, Fishlake National Forest, Utah, on available soil N and net N mineralization for three summers after the fire using an ion exchange membrane (IEM) soil core incubation method. Fire in mixed aspen/conifer increased the amount of available NH4, and a subsequent net increase in soil nitrification was observed. Release...

[Fine root dynamics and its relationship with soil fertility in tropical rainforests of Chocó].

PubMed

Quinto, Harley; Caicedo, Haylin; Thelis Perez, May; Moreno, Flavio

2016-12-01

The fine roots play an important role in the acquisition of water and minerals from the soil, the global carbon balance and mitigation of climate change. The dynamics (productivity and turnover) of fine roots is essential for nutrient cycling and carbon balance of forest ecosystems. The availability of soil water and nutrients has significantly determined the productivity and turnover of fine roots. It has been hypothesized that fine roots dynamics increases with the availability of soil resources in tropical forest ecosystems. To test this hypothesis in tropical rainforests of Chocó (ecosystems with the highest rainfall in the world), five one-ha permanent plots were established in the localities of Opogodó and Pacurita, where the productivity and turnover of fine roots were measured at 0-10 cm and 10-20 cm depth. The measurement of the fine root production was realized by the Ingrowth core method. The fine root turnover was measured like fine roots production divided mean annual biomass. In addition, soil fertility parameters (pH, nutrients, and texture) were measured and their association with productivity and turnover of fine roots was evaluated. It was found that the sites had nutrient-poor soils. The localities also differ in soil; Opogodó has sandy soils and flat topography, and Pacurita has clay soils, rich in aluminum and mountainous topography. In Opogodó fine root production was 6.50 ± 2.62 t/ha.yr (mean ± SD). In Pacurita, fine root production was 3.61 ± 0.88 t/ha.yr. Also in Opogodó, the fine root turnover was higher than in Pacurita (1.17 /y and 0.62 /y, respectively). Fine root turnover and production in the upper soil layers (10 cm upper soil) was considerably higher. Productivity and turnover of fine roots showed positive correlation with pH and contents of organic matter, total N, K, Mg, and sand; whereas correlations were negative with ECEC and contents of Al, silt, and clay. The percentage of sand was the parameter that best explained the variations of fine root production. The fine root turnover was negatively explained by soil Al availability. Results suggested the increase of fine root dynamics with soil fertility at a local scale, which also indicates that under the oligotrophic conditions of soils in tropical rainforests, fine roots tend to proliferate rapidly in small patches of soil rich in sand and nutrients.

Limited protection of macro-aggregate-occluded organic carbon in Siberian steppe soils

NASA Astrophysics Data System (ADS)

Bischoff, Norbert; Mikutta, Robert; Shibistova, Olga; Puzanov, Alexander; Silanteva, Marina; Grebennikova, Anna; Fuß, Roland; Guggenberger, Georg

2017-05-01

Macro-aggregates especially in agricultural steppe soils are supposed to play a vital role for soil organic carbon (OC) stabilization at a decadal timescale. While most research on soil OC stabilization in steppes focused on North American prairie soils of the Great Plains with information mainly provided by short-term incubation experiments, little is known about the agricultural steppes in southwestern Siberia, though they belong to the greatest conversion areas in the world and occupy an area larger than that in the Great Plains. To quantify the proportion of macro-aggregate-protected OC under different land use as function of land use intensity and time since land use change (LUC) from pasture to arable land in Siberian steppe soils, we determined OC mineralization rates of intact (250-2000 µm) and crushed (< 250 µm) macro-aggregates in long-term incubations over 401 days (20 °C; 60 % water holding capacity) along two agricultural chronosequences in the Siberian Kulunda steppe. Additionally, we incubated bulk soil (< 2000 µm) to determine the effect of LUC and subsequent agricultural use on a fast and a slow soil OC pool (labile vs. more stable OC), as derived from fitting exponential-decay models to incubation data. We hypothesized that (i) macro-aggregate crushing leads to increased OC mineralization due to an increasing microbial accessibility of a previously occluded labile macro-aggregate OC fraction, and (ii) bulk soil OC mineralization rates and the size of the fast OC pool are higher in pasture than in arable soils with decreasing bulk soil OC mineralization rates and size of the fast OC pool as land use intensity and time since LUC increase. Against our hypothesis, OC mineralization rates of crushed macro-aggregates were similar to those of intact macro-aggregates under all land use regimes. Macro-aggregate-protected OC was almost absent and accounted for < 1 % of the total macro-aggregate OC content and to a maximum of 8 ± 4 % of mineralized OC. In accordance to our second hypothesis, highest bulk soil OC mineralization rates and sizes of the fast OC pool were determined under pasture, but mineralization rates and pool sizes were unaffected by land use intensity and time since LUC. However, at one chronosequence mean residence times of the fast and slow OC pool tended to decrease with increasing time since establishment of arable use. We conclude that the tillage-induced breakdown of macro-aggregates has not reduced the OC contents in the soils under study. The decline of OC after LUC is probably attributed to the faster soil OC turnover under arable land as compared to pasture at a reduced plant residue input.

The effects of worms, clay and biochar on CO2 emissions during production and soil application of co-composts

NASA Astrophysics Data System (ADS)

Barthod, Justine; Rumpel, Cornélia; Paradelo, Remigio; Dignac, Marie-France

2016-12-01

In this study we evaluated CO2 emissions during composting of green wastes with clay and/or biochar in the presence and absence of worms (species of the genus Eisenia), as well as the effect of those amendments on carbon mineralization after application to soil. We added two different doses of clay, biochar or their mixture to pre-composted green wastes and monitored carbon mineralization over 21 days in the absence or presence of worms. The resulting co-composts and vermicomposts were then added to a loamy Cambisol and the CO2 emissions were monitored over 30 days in a laboratory incubation. Our results indicated that the addition of clay or clay/biochar mixture reduced carbon mineralization during co-composting without worms by up to 44 %. In the presence of worms, CO2 emissions during composting increased for all treatments except for the low clay dose. The effect of the amendments on carbon mineralization after addition to soil was small in the short term. Overall, composts increased OM mineralization, whereas vermicomposts had no effect. The presence of biochar reduced OM mineralization in soil with respect to compost and vermicompost without additives, whereas clay reduced mineralization only in the composts. Our study indicates a significant role of the conditions of composting on mineralization in soil. Therefore, the production of a low CO2 emission amendment requires optimization of feedstocks, co-composting agents and worm species.

Development and application of screening tools for biodegradation in water-sediment systems and soil.

PubMed

Junker, Thomas; Coors, Anja; Schüürmann, Gerrit

2016-02-15

Two new screening-test systems for biodegradation in water-sediment systems (WSST; Water-Sediment Screening Tool) and soil (SST; Soil Screening Tool) were developed in analogy with the water-only test system OECD 301C (MITI-test). The test systems could be applied successfully to determine reproducible experimental mineralization rates and kinetics on the screening-test level for fifteen organic chemicals in water (MITI), water-sediment (WSST) and soil (SST). Substance-specific differences were observed for mineralization compared among the three test systems. Based on mineralization rate and mineralization half-life, the fifteen compounds could be grouped into four biodegradation categories: substances with high mineralization and a half-life <28 days in (1) all three test systems, (2) only in the MITI test and in the WSST, (3) only in the SST, and (4) none of the test systems. The observed differences between the MITI results and the WSST and SST biodegradation rates of the compounds do not reflect their (reversible) sorption into organic matter in terms of experimental K(oc) values and log D values for the relevant pH range. Regarding mineralization kinetics we recommend to determine the lag-phase, mineralization half-life and mineralization rate using a 5-parameter logistic regression for degradation curves with and without lag-phase. Experimental data obtained with the WSST and the SST could be verified by showing good agreement with biodegradation data from databases and literature for the majority of compounds tested. Thus, these new screening-tools for water-sediment and soil are considered suitable to determine sound and reliable quantitative mineralization data including mineralization kinetics in addition to the water-only ready biodegradability tests according to OECD 301. Copyright © 2015 Elsevier B.V. All rights reserved.

Mineral Control of Soil Carbon Dynamics in Forest Soils: A Lithosequence Under Ponderosa Pine

NASA Astrophysics Data System (ADS)

Heckman, K. A.; Welty-Bernard, A.; Rasmussen, C.; Schwartz, E.; Chorover, J.

2008-12-01

The role of soil organic carbon in regulating atmospheric CO2 concentration has spurred interest in both quantifying existing soil C stocks and modeling the behavior of soil C under climate change scenarios. Soil parent material exerts direct control over soil organic carbon content through its influence on soil pH and mineral composition. Soil acidity and mineral composition also influence soil microbial community composition and activity, thereby controlling soil respiration rates and microbial biomass size. We sampled a lithosequence of four parent materials (rhyolite, granite, basalt, limestone) under Pinus ponderosa to examine the effects of soil mineralogy and acidity on soil organic carbon content and soil microbial community. Three soil profiles were examined on each parent material and analyzed by X-ray diffraction, pH, selective dissolution, C and N content, and 13C signature. Soils from each of the four parent materials were incubated for 40 days, and microbial communities were compared on the basis of community composition (as determined through T-RFLP analysis), specific metabolic activity, biomass, δ13C of respired CO2, and cumulative amount of C mineralized over the course of the incubation. Soil C content varied significantly among soils of different parent material, and was strongly and positively associated with the abundance of Al-humus complexes r2 = 0.71; P < 0.0001, Fe-humus complexes r2 = 0.74; P = 0.0003, and crystalline Fe-oxide content r2 = 0.63; P = 0.0023. Microbial community composition varied significantly among soils and showed strong associations with soil pH 1:1 in KCl; r2 = 0.87; P < 0.0001, concentration of exchangeable Al r2 = 0.81; P < 0.0001, amorphous Fe oxide content r2 = 0.59; P < 0.004, and Al-humus content r2 = 0.35; P < 0.04. Mineralization rates, biomass and δ13C of respired CO2 differed among parent materials, and also varied with incubation time as substrate quality and N availability changed. The results demonstrate that within a specific ecosystem type, soil parent material exerts significant control over the lability and bioavailability of soil C and soil microbial community composition. We suggest that soil parent material and mineralogy are critical parameters for predicting soil C dynamics and recalcitrance of soil C stocks.

Dissipation of bentazone, pyrimethanil and boscalid in biochar and digestate based soil mixtures for biopurification systems.

PubMed

Mukherjee, Santanu; Tappe, Wolfgang; Weihermueller, Lutz; Hofmann, Diana; Köppchen, Stephan; Laabs, Volker; Schroeder, Tom; Vereecken, Harry; Burauel, Peter

2016-02-15

Biopurification systems, such as biofilters, are biotechnological tools to prevent point sources of pesticide pollution stemming from on-farm operations. For the purification processes pesticide sorption and mineralization and/or dissipation are essential and both largely depend on the type of filling materials and the pesticide in use. In this paper the mineralization and dissipation of three contrasting (14)C-labeled pesticides (bentazone, boscalid, and pyrimethanil) were investigated in laboratory incubation experiments using sandy soil, biochar produced from Pine woodchips, and/or digestate obtained from anaerobic digestion process using maize silage, chicken manure, beef and pig urine as feedstock. The results indicate that the addition of digestate increased pesticide mineralization, whereby the mineralization was not proportional to the digestate loads in the mixture, indicating a saturation effect in the turnover rate of pesticides. This effect was in correlation with the amount of water extractable DOC, obtained from the digestate based mixtures. Mixing biochar into the soil generally reduced total mineralization and led to larger sorption/sequestration of the pesticides, resulting in faster decrease of the extractable fraction. Also the addition of biochar to the soil/digestate mixtures reduced mineralization compared to the digestate alone mixture but mineralization rates were still higher as for the biochar/soil alone. In consequence, the addition of biochar to the soil generally decreased pesticide dissipation times and larger amounts of biochar led to high amounts of non-extractable residues of pesticide in the substrates. Among the mixtures tested, a mixture of digestate (5%) and biochar (5%) gave optimal results with respect to mineralization and simultaneous sorption for all three pesticides. Copyright © 2015 Elsevier B.V. All rights reserved.

Rainwater as a chemical agent of geologic processes; a review

USGS Publications Warehouse

Carroll, Dorothy

1962-01-01

Chemical analyses of the rainwater collected at several localities are given to show the variations of the principal constitutents. In rock weathering and soil-forming processes, the chemical composition of rainwater has an important effect which has been evaluated for only a few arid areas. In humid regions the important amounts of calcium, magnesium, sodium, and potassium added yearly by rain may be expected to influence the composition of the soil water and thereby the cations in the exchange positions of soil clay minerals. The acquisition of cations by clay minerals may slow down chemical weathering. The stability of soil clay minerals is influenced by the constant accession of cations from rainwater. Conversely, the clay minerals modify the amounts and kinds of cations that are leached out by drainage waters. The stability of micaceous minerals in soils may be partly due to accessions of K +1 ions from rainwater. The pH of rainwater in any area varies considerably and seems to form a seasonal and regional pattern. The recorded pH values range from 3.0 to 9.8.

Distribution and Degradation State of Soil Organic Carbon Stocks in Ice Wedge Polygons of the Arctic Coastal Plain, Alaska

NASA Astrophysics Data System (ADS)

Jastrow, J. D.; Ping, C. L.; Deck, C. B.; Matamala, R.; Vugteveen, T. W.; Lederhouse, J. S.; Michaelson, G. J.

2016-12-01

Estimates of the amount of organic carbon (C) stored in permafrost-region soils and its susceptibility to mobilization with changing climate are improving but remain high, affecting the ability to reliably predict regional C-climate feedbacks. In lowland permafrost soils, much of the organic matter exists in a poorly degraded state and is often weakly associated with soil minerals due to the cold, wet environment and cryoturbation. Thus, the impacts of warming and permafrost thaw likely will depend, at least initially, on the past history of soil organic matter (SOM) degradation. Ice wedge polygons are ubiquitous, patterned ground features throughout Arctic coastal plain regions and are large enough (5-30 m across) that a better three-dimensional understanding of their C stocks and relative degradation state could improve geospatial upscaling of observational data and contribute benchmarks for constraining model parameters. We investigated the distribution and existing degradation state of SOM to a depth of 2 meters across three polygon types on the Arctic Coastal Plain of Alaska: flat-centered (FCP), low-centered (LCP), and high-centered (HCP) polygons, with each type replicated 3 times. To assess the relative degradation state of SOM, we used particle size fractionation to isolate fibric (coarse) from more degraded (fine) particulate organic matter and separated mineral-associated organic matter into silt- and clay-sized fractions. We found variations in the thickness and quality of surface organic layers for different polygon types. Below the active layer, organic-rich cryoturbated layers were located in the transition zone and fingered down into the upper permafrost. Soil organic C stocks varied across individual polygons and differed among polygon types, with HCPs generally having the largest C stocks. The relative degradation state of SOM also varied spatially and vertically within polygons and differed among polygon types. Our findings suggest that accounting for polygon-scale (wedge to center to wedge) and landscape-scale (polygon type) variations could help reduce the uncertainties in observational estimates of soil C stocks and their degradation state for areas dominated by ice wedge polygons.

Plant-available and water-soluble phosphorus in soils amended with separated manure solids.

PubMed

Gasser, M-O; Chantigny, M H; Angers, D A; Bittman, S; Buckley, K E; Rochette, P; Massé, D

2012-01-01

Physical, chemical, or biological treatment of animal liquid manure generally produces a dry-matter rich fraction (DMF) that contains most of the initial phosphorus (P). Our objective was to assess the solubility and plant availability of P from various DMFs as a function of soil P status. Eight different DMFs were obtained from liquid swine (LSM) and dairy cattle (LDC) manures treated by natural decantation, anaerobic digestion, chemical flocculation, composting, or mechanical separation. The DMFs were compared with mineral P fertilizer in a pot experiment with oat ( L.) grown in four soils with varied P-fixing capacities and P saturation levels. The DMFs were added at a rate of 50 mg P kg soil and incubated 14 d before seeding. Soil water-extractable P (P) at all water:soil extraction ratios (2:1, 20:1, and 200:1) was slightly higher when DMFs were derived from LDC rather than LSM. Soil P at the 2:1 ratio was lower with anaerobically digested LSM. At the 2:1 extraction ratio, DMF P was less soluble than mineral P as P saturation in soils increased. In soils with a lower P-fixing capacity, DMF P appeared less water soluble than mineral P under 20:1 and 200:1 extraction ratios. After 72 d of plant growth, DMFs produced yields comparable to mineral P fertilizer. Although the plant availability of P from DMFs was comparable to mineral P fertilizer, P from DMFs could be less vulnerable to leaching or runoff losses in soils with a high P saturation level or low P-fixing capacity. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils.

PubMed

Zhang, Mingkui; Pu, Jincheng

2011-01-01

Four minerals, agricultural limestone (AL), rock phosphate (RP), palygorskite (PG), and calcium magnesium phosphate (CMP), were evaluated by means of chemical fractions of heavy metals in soils and concentrations of heavy metals in leachates from columns to determine their ability to stabilize heavy metals in polluted urban soils. Two urban soils (calcareous soil and acidic soil) polluted with cadmium, copper, zinc and lead were selected and amended in the laboratory with the mineral materials) for 12 months. Results indicated that application of the mineral materials reduced exchangeable metals in the sequence of Pb, Cd > Cu > Zn. The reduction of exchangeable fraction of heavy metals in the soils amended with different mineral materials followed the sequence of CMP, PG > AL > RP. Reductions of heavy metals leached were based on comparison with cumulative totals of heavy metals eluted through 12 pore volumes from an untreated soil. The reductions of the metals eluted from the calcareous soil amended with the RP, AL, PG and CMP were 1.98%, 38.89%, 64.81% and 75.93% for Cd, 8.51%, 40.42%, 60.64% and 55.32% for Cu, 1.76%, 52.94%, 70.00% and 74.12% for Pb, and 28.42%, 52.74%, 64.38% and 49.66% for Zn. Those from the acidic soil amended with the CMP, PG, AL, and RP were 25.65%, 68.06%, 78.01% and 79.06% for Cd, 26.56%, 49.64%, 43.40% and 34.68% for Cu, 44.44%, 33.32%, 61.11% and 69.44% for Pb, and 18.46%, 43.77%, 41.98% and 40.68% for Zn. The CMP and PG treatments were superior to the AL and RP for stabilizing heavy metals in the polluted urban soils.

Long-term fertilization of a boreal Norway spruce forest increases the temperature sensitivity of soil organic carbon mineralization

PubMed Central

Coucheney, Elsa; Strömgren, Monika; Lerch, Thomas Z; Herrmann, Anke M

2013-01-01

Boreal ecosystems store one-third of global soil organic carbon (SOC) and are particularly sensitive to climate warming and higher nutrient inputs. Thus, a better description of how forest managements such as nutrient fertilization impact soil carbon (C) and its temperature sensitivity is needed to better predict feedbacks between C cycling and climate. The temperature sensitivity of in situ soil C respiration was investigated in a boreal forest, which has received long-term nutrient fertilization (22 years), and compared with the temperature sensitivity of C mineralization measured in the laboratory. We found that the fertilization treatment increased both the response of soil in situ CO2 effluxes to a warming treatment and the temperature sensitivity of C mineralization measured in the laboratory (Q10). These results suggested that soil C may be more sensitive to an increase in temperature in long-term fertilized in comparison with nutrient poor boreal ecosystems. Furthermore, the fertilization treatment modified the SOC content and the microbial community composition, but we found no direct relationship between either SOC or microbial changes and the temperature sensitivity of C mineralization. However, the relation between the soil C:N ratio and the fungal/bacterial ratio was changed in the combined warmed and fertilized treatment compared with the other treatments, which suggest that strong interaction mechanisms may occur between nutrient input and warming in boreal soils. Further research is needed to unravel into more details in how far soil organic matter and microbial community composition changes are responsible for the change in the temperature sensitivity of soil C under increasing mineral N inputs. Such research would help to take into account the effect of fertilization managements on soil C storage in C cycling numerical models. PMID:24455147

Anthropic changes to the biotic factor of soil formation from forests to managed grasslands along summits of the western Pyrenees Mountains, France

NASA Astrophysics Data System (ADS)

Leigh, David; Gragson, Theodore

2017-04-01

Mounting evidence indicates that highland pastures of the humid-temperate western Pyrenees were converted from mixed forests to managed grasslands thousands of years ago, as early as during the late Neolithic and Bronze age by human actions including use of fire. We observe pronounced differences between soil profiles of ancient pastures and old-growth forests in otherwise similar landscape positions. In order to test physical and chemical differences, we collected paired samples of forest versus grassland soils at four separate hillslope sites where there was a clear boundary between the two vegetation types. Animal trails were excluded from sampling. Factors of climate, topography, parent material, and time of soil formation were essentially identical in the forests and pastures of each site, but the time of soil under grassland vegetation may have varied. Each paired hillslope site included five core samples (7.6 cm diameter) from the upper 7.6 cm of the mineral soil within each vegetation type, and the A horizon thickness was recorded at each core hole site. In addition, one complete soil profile was sampled in each vegetation type at each site, making a total of 20 core samples and 4 complete profiles from each respective vegetation type. In addition, we measured the magnetic susceptibility of the mineral soil surface on two transects crossing the vegetation boundary. Core samples have been measured for bulk density, pH, plant-available nutrients, and organic matter; and tests for total carbon and nitrogen, amorphous silica, charcoal, and other forms of black carbon are ongoing. Preliminary results indicate pastured A horizons are about three times as thick as forested soils, contain more organic matter, have lower soil bulk densities, have much finer and stronger structural development of soil aggregates. These traits favor much greater infiltration and water holding capacities of the pastured soils, which we have validated with saturated hydraulic conductivity tests. Pedogenically, the pastured soils indicate that melanization processes have been much more pronounced than in the forested soils. Distinct changes in soil materials result from conversion to pasture. Significantly more black carbon (including macro-charcoal) appears to be present in the pastured soils, indicating that it plays an important role in melanization, in addition to long-term sequestration of carbon. Pastured soils contain greater contents of amorphous silica due to more rapid phytolith production from grasses as opposed to trees. Pastures register significantly higher soil magnetic susceptibility than forests, presumably from past use of fire. In essence, anthropic manipulation of the biotic factor of pedogenesis has created new soil materials, processes, and functions. Our current research involves radiocarbon and chronostratigraphy to establish rates of this anthropisation of the biotic factor.

A rapid and cost effective method for soil carbon mineralization under static incubations

USDA-ARS?s Scientific Manuscript database

Soil incubations with subsequent determination of carbon dioxide (CO2) are common soil assays used to estimate C mineralization rates and active organic C pools. Two common methods used to detect CO2 in laboratory incubations are gas chromatography (GC) and alkali absorption followed by titration (...

BORON RELEASE FROM WEATHERING ILLITES, SERPENTINE, SHALES, AND ILLITIC/PALYGORSKITIC SOILS

EPA Science Inventory

Despite extensive research on B adsorption and release from soils, mineral sources of B within natively high B soils remain poorly under- stood. The objectives of this study were to identify source minerals contributing to the continued B release after extraction of soluble B and...

Picloram and Aminopyralid Sorption to Soil and Clay Minerals

USDA-ARS?s Scientific Manuscript database

Aminopyralid sorption data are lacking, and these data are needed to predict off-target transport and plant available herbicide in soil solution. The objective of this research was to determine the sorption of picloram and aminopyralid to five soils and three clay minerals and determine if the pote...

Water Storage and Related Physical Characteristics of Four Mineral Soils in North Central Minnesota

Treesearch

E. S. Verry

1969-01-01

Soil water storage in a 7.5 foot profile varied nearly 100 percent (7.9 to 15.5 inches) among four mineral soils ranging from a sand to sandy loam. Bulk density, size fractions, and four water retention values are tabulated for each horizon.

Physicochemical properties and stability of thousand-year-old soil organic matter in boreal paleopodzols

NASA Astrophysics Data System (ADS)

Feng, Wen-Ting; Klaminder, Jonatan; Boily, Jean-Francois

2013-04-01

Soil organic matter (SOM) stabilization mechanisms are key to predict carbon (C) cycle responses to climate change, especially in critically sensitive ecosystems, such as the arctic and boreal ecosystems of Scandinavia (IPCC 2007). Interactions between organic matter and soil mineral components can be of particular importance. Their impacts on SOM stability are however not fully resolved. In this study, we present an exhaustive physicochemical characterization of SOM and soil mineral components of boreal paleopodzols formed over several thousands of years in northern Sweden. We also test the hypothesis that old SOM in these environments is strongly associated to mineral surfaces. This work was specifically focused on two relict podzolic profiles capped by more recently developed podzolic profile. Each of the three profiles consisted of a well developed E-horizon and of an underlying B-horizon enriched in secondary weathering products. Soil C age was greater with increasing depth, with the deepest horizon dating from the mid-Holocene. Organic C loadings, expressed in terms of C mass per mineral surface area, decreased from 0.52 to 0.31 mg C m-2 from deep to the deepest B horizons. A monolayer coating model could thus be used to suggest that C was mainly bonded to unsaturated mineral surfaces. Scanning electron microscopy and energy dispersive X-ray spectroscopy showed that, unlike in younger B-horizon, the oldest C of the deepest B-horizon did not accumulate in clusters. It was instead distributed more homogenously at the micrometer scale with soil mineral particles. X-ray photoelectron spectroscopy moreover showed that the top 1-10 nm of the mineral surfaces contained proportions of aliphatic-C, ether/alcohol-C, and amide-C that varied greatly amongst the three B horizons but not among the three E horizons. Different composition of SOM remained in deep E and B horizons, thereby suggesting a selective SOM preservation process that is controlled by the properties of the mineral matrix. Our findings therefore support the concept that soil mineral surfaces impact SOM stability. The importance of SOM-mineral surfaces complexation was demonstrated further through combined temperature-programmed desorption mass spectrometric Fourier transform infrared (TPD-MS-FTIR) experiments pointing to highly resilient forms of SOM associated to mineral particle surfaces. In summary, our study suggests organic matter sorption on mineral surfaces is important for SOM preservation at the millennial scale. Predicting the long-term fate of C in boreal regions should consequently account for such types of organo-mineral associations.

Cd Mobility in Anoxic Fe-Mineral-Rich Environments - Potential Use of Fe(III)-Reducing Bacteria in Soil Remediation

NASA Astrophysics Data System (ADS)

Muehe, E. M.; Adaktylou, I. J.; Obst, M.; Schröder, C.; Behrens, S.; Hitchcock, A. P.; Tylsizczak, T.; Michel, F. M.; Krämer, U.; Kappler, A.

2014-12-01

Agricultural soils are increasingly burdened with heavy metals such as Cd from industrial sources and impure fertilizers. Metal contaminants enter the food chain via plant uptake from soil and negatively affect human and environmental health. New remediation approaches are needed to lower soil metal contents. To apply these remediation techniques successfully, it is necessary to understand how soil microbes and minerals interact with toxic metals. Here we show that microbial Fe(III) reduction initially mobilizes Cd before its immobilization under anoxic conditions. To study how microbial Fe(III) reduction influences Cd mobility, we isolated a new Cd-tolerant, Fe(III)-reducing Geobacter sp. from a heavily Cd-contaminated soil. In lab experiments, this Geobacter strain first mobilized Cd from Cd-loaded Fe(III) hydroxides followed by precipitation of Cd-bearing mineral phases. Using Mössbauer spectroscopy and scanning electron microscopy, the original and newly formed Cd-containing Fe(II) and Fe(III) mineral phases, including Cd-Fe-carbonates, Fe-phosphates and Fe-(oxyhydr)oxides, were identified and characterized. Using energy-dispersive X-ray spectroscopy and synchrotron-based scanning transmission X-ray microscopy, Cd was mapped in the Fe(II) mineral aggregates formed during microbial Fe(III) reduction. Microbial Fe(III) reduction mobilizes Cd prior to its precipitation in Cd-bearing mineral phases. The mobilized Cd could be taken up by phytoremediating plants, resulting in a net removal of Cd from contaminated sites. Alternatively, Cd precipitation could reduce Cd bioavailability in the environment, causing less toxic effects to crops and soil microbiota. However, the stability and thus bioavailability of these newly formed Fe-Cd mineral phases needs to be assessed thoroughly. Whether phytoremediation or immobilization of Cd in a mineral with reduced Cd bioavailability are feasible mechanisms to reduce toxic effects of Cd in the environment remains to be determined.

Soil Minerals: AN Overlooked Mediator of Plant-Microbe Competition for Organic Nitrogen in the Rhizosphere

NASA Astrophysics Data System (ADS)

Grandy, S.; Jilling, A.; Keiluweit, M.

2016-12-01

Recent research on the rate limiting steps in soil nitrogen (N) availability have shifted in focus from mineralization to soil organic matter (SOM) depolymerization. To that end, Schimel and Bennett (2004) argued that together with enzymatic breakdown of polymers to monomers, microsite processes and plant-microbial competition collectively drive N cycling. Here we present new conceptual models arguing that while depolymerization is a critical first step, mineral-organic associations may ultimately regulate the provisioning of bioavailable organic N, especially in the rhizosphere. Mineral-associated organic matter (MAOM) is a rich reservoir for N in soils and often holds 5-7x more N than particulate or labile fractions. However, MAOM is considered largely unavailable to plants as a source of N due to the physicochemical forces on mineral surfaces that stabilize organic matter. We argue that in rhizosphere hotspots, MAOM is in fact a potentially mineralizable and important source of nitrogen for plants. Several biochemical strategies enable plants and microbes to compete with mineral-organic interactions and effectively access MAOM. In particular, root-deposited low molecular weight compounds in the form of root exudates facilitate the biotic and abiotic destabilization and subsequent bioavailability of MAOM. We believe that the competitive balance between the potential fates of assimilable organic N — bound to mineral surfaces or dissolved and available for assimilation — depends on the specific interaction between and properties of the clay, soil solution, mineral-bound organic matter, and microbial community. For this reason, the plant-soil-MAOM interplay is enhanced in rhizosphere hotspots relative to non-rhizosphere environments, and likely strongly regulates plant-microbe competition for N. If these hypotheses are true, we need to reconsider potential soil N cycle responses to changes in climate and land use intensity, focusing on the processes by which management and other anthropogenic stressors can alter MAOM's N-supplying capacity.

Physical access for residue-mineral interactions controls organic carbon retention in an Oxisol soil.

PubMed

Ye, Chenglong; Bai, Tongshuo; Yang, Yi; Zhang, Hao; Guo, Hui; Li, Zhen; Li, Huixin; Hu, Shuijin

2017-07-24

Oxisol soils are widely distributed in the humid tropical and subtropical regions and are generally characterized with high contents of metal oxides. High metal oxides are believed to facilitate organic carbon (C) accumulation via mineral-organic C interactions but Oxisols often have low organic C. Yet, the causes that constrain organic C accumulation in Oxisol soil are not exactly clear. Here we report results from a microcosm experiment that evaluated how the quantity and size of crop residue fragments affect soil C retention in a typical Oxisol soil in southeast China. We found that there were significantly higher levels of dissolved organic C (DOC), microbial biomass C (MBC) and C accumulation in the heavy soil fraction in soil amended with fine-sized (<0.2 mm) compared with coarse-sized (5.0 mm) fragments. Attenuated total reflectance-Fourier transform infrared spectroscopy analysis further showed that fine-sized residues promoted stabilization of aliphatic C-H and carboxylic C=O compounds associated with mineral phases. In addition, correlation analysis revealed that the increased content of organic C in the heavy soil fraction was positively correlated with increased DOC and MBC. Together, these results suggest that enhancement of contact between organic materials and soil minerals may promote C stabilization in Oxisols.

Distinct temperature sensitivity of soil carbon decomposition in forest organic layer and mineral soil

PubMed Central

Xu, Wenhua; Li, Wei; Jiang, Ping; Wang, Hui; Bai, Edith

2014-01-01

The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Here we determined Q10 in surface organic layer and subsurface mineral soil along an elevation gradient in a temperate forest ecosystem. Q10 was calculated by comparing the times required to respire a given amount of soil C at 15 and 25°C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.22–0.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation. This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. No clear trend of Q10 was found along the elevation gradient. Because the soil organic C pool of the organic layer in temperate forests is large, its higher temperature sensitivity highlights its importance in C cycling under global warming. PMID:25270905

Influence of the Amino Acid Sequence on Protein-Mineral Interactions in Soil

NASA Astrophysics Data System (ADS)

Chacon, S. S.; Reardon, P. N.; Purvine, S.; Lipton, M. S.; Washton, N.; Kleber, M.

2017-12-01

The intimate associations between protein and mineral surfaces have profound impacts on nutrient cycling in soil. Proteins are an important source of organic C and N, and a subset of proteins, extracellular enzymes (EE), can catalyze the depolymerization of soil organic matter (SOM). Our goal was to determine how variation in the amino acid sequence could influence a protein's susceptibility to become chemically altered by mineral surfaces to infer the fate of adsorbed EE function in soil. We hypothesized that (1) addition of charged amino acids would enhance the adsorption onto oppositely charged mineral surfaces (2) addition of aromatic amino acids would increase adsorption onto zero charged surfaces (3) Increase adsorption of modified proteins would enhance their susceptibility to alterations by redox active minerals. To test these hypotheses, we generated three engineered proxies of a model protein Gb1 (IEP 4.0, 6.2 kDA) by inserting either negatively charged, positively charged or aromatic amino acids in the second loop. These modified proteins were allowed to interact with functionally different mineral surfaces (goethite, montmorillonite, kaolinite and birnessite) at pH 5 and 7. We used LC-MS/MS and solution-state Heteronuclear Single Quantum Coherence Spectroscopy NMR to observe modifications on engineered proteins as a consequence to mineral interactions. Preliminary results indicate that addition of any amino acids to a protein increase its susceptibility to fragmentation and oxidation by redox active mineral surfaces, and alter adsorption to the other mineral surfaces. This suggest that not all mineral surfaces in soil may act as sorbents for EEs and chemical modification of their structure should also be considered as an explanation for decrease in EE activity. Fragmentation of proteins by minerals can bypass the need to produce proteases, but microbial acquisition of other nutrients that require enzymes such as cellulases, ligninases or phosphatases may be hampered by mineral association.

Microbial Composition in Decomposing Pine Litter Shifts in Response to Common Soil Secondary Minerals

NASA Astrophysics Data System (ADS)

Welty-Bernard, A. T.; Heckman, K.; Vazquez, A.; Rasmussen, C.; Chorover, J.; Schwartz, E.

2011-12-01

A range of environmental and biotic factors have been identified that drive microbial community structure in soils - carbon substrates, redox conditions, mineral nutrients, salinity, pH, and species interactions. However, soil mineralogy has been largely ignored as a candidate in spite of recent studies that indicate that minerals have a substantial impact on soil organic matter stores and subsequent fluxes from soils. Given that secondary minerals and organic colloids govern a soil's biogeochemical activity due to surface area and electromagnetic charge, we propose that secondary minerals are a strong determinant of the communities that are responsible for process rates. To test this, we created three microcosms to study communities during decomposition using pine forest litter mixed with two common secondary minerals in soils (goethite and gibbsite) and with quartz as a control. Changes in bacterial and fungal communities were tracked over the 154-day incubation by pyrosequencing fragments of the bacterial 16S and fungal 18S rRNA genes. Ordination using nonmetric multidimensional scaling showed that bacterial communities separated on the basis of minerals. Overall, a single generalist - identified as an Acidobacteriaceae isolate - dominated all treatments over the course of the experiment, representing roughly 25% of all communities. Fungal communities discriminated between the quartz control alone and mineral treatments as a whole. Again, several generalists dominated the community. Coniochaeta ligniaria dominated communities with abundances ranging from 29 to 40%. The general stability of generalist populations may explain the similarities between treatment respiration rates. Variation between molecular fingerprints, then, were largely a function of unique minor members with abundances ranging from 0.01 to 8%. Carbon availability did not surface as a possible mechanism responsible for shifts in fingerprints due to the relatively large mass of needles in the incubation. Other possible mechanisms include the presence of soluble Fe as an alternative energy source in the goethite treatment, the presence of toxic soluble Al in the gibbsite treatment, the loss of available phosphorus in the secondary mineral treatments due to sorption by secondary mineral surfaces, and variations in mineral surfaces as microhabitats. These findings suggest that Al and Fe oxides, such as goethite or gibbsite, are a factor in determining microbial community structure.

Assessment of bioavailability of soil-sorbed atrazine.

PubMed

Park, Jeong-Hun; Feng, Yucheng; Ji, Pingsheng; Voice, Thomas C; Boyd, Stephen A

2003-06-01

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO(2) production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.

Carbon mineralization in acidic, xeric forest soils: induction of new activities.

PubMed

Tate, R L

1985-08-01

Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon.

Carbon Mineralization in Acidic, Xeric Forest Soils: Induction of New Activities †

PubMed Central

Tate, Robert L.

1985-01-01

Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of 14C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon. PMID:16346862

Assessment of Bioavailability of Soil-Sorbed Atrazine

PubMed Central

Park, Jeong-Hun; Feng, Yucheng; Ji, Pingsheng; Voice, Thomas C.; Boyd, Stephen A.

2003-01-01

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO2 production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine. PMID:12788728

Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes.

PubMed

Li, Junxia; Zhou, Hailing; Wang, Yanxin; Xie, Xianjun; Qian, Kun

2017-06-01

Characterizing the properties of main host of iodine in soil/sediment and the geochemical behaviors of iodine species are critical to understand the mechanisms of iodine mobilization in groundwater systems. Four surface soil and six subsurface sediment samples were collected from the iodine-affected area of Datong basin in northern China to conduct batch experiments and to evaluate the effects of NOM and/or organic-mineral complexes on iodide/iodate geochemical behaviors. The results showed that both iodine contents and k f -iodate values had positive correlations with solid TOC contents, implying the potential host of NOM for iodine in soil/sediment samples. The results of chemical removal of easily extracted NOM indicated that the NOM of surface soils is mainly composed of surface embedded organic matter, while sediment NOM mainly occurs in the form of organic-mineral complexes. After the removal of surface sorbed NOM, the decrease in k f -iodate value of treated surface soils indicates that surface sorbed NOM enhances iodate adsorption onto surface soil. By contrast, k f -iodate value increases in several H 2 O 2 -treated sediment samples, which was considered to result from exposed rod-like minerals rich in Fe/Al oxyhydroxide/oxides. After chemical removal of organic-mineral complexes, the lowest k f -iodate value for both treated surface soils and sediments suggests the dominant role of organic-mineral complexes on controlling the iodate geochemical behavior. In comparison with iodate, iodide exhibited lower affinities on all (un)treated soil/sediment samples. The understanding of different geochemical behaviors of iodine species helps to explain the occurrence of high iodine groundwater with iodate and iodide as the main species in shallow (oxidizing conditions) and deep (reducing conditions) groundwater. Copyright © 2017 Elsevier B.V. All rights reserved.

Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes

NASA Astrophysics Data System (ADS)

Li, Junxia; Zhou, Hailing; Wang, Yanxin; Xie, Xianjun; Qian, Kun

2017-06-01

Characterizing the properties of main host of iodine in soil/sediment and the geochemical behaviors of iodine species are critical to understand the mechanisms of iodine mobilization in groundwater systems. Four surface soil and six subsurface sediment samples were collected from the iodine-affected area of Datong basin in northern China to conduct batch experiments and to evaluate the effects of NOM and/or organic-mineral complexes on iodide/iodate geochemical behaviors. The results showed that both iodine contents and kf-iodate values had positive correlations with solid TOC contents, implying the potential host of NOM for iodine in soil/sediment samples. The results of chemical removal of easily extracted NOM indicated that the NOM of surface soils is mainly composed of surface embedded organic matter, while sediment NOM mainly occurs in the form of organic-mineral complexes. After the removal of surface sorbed NOM, the decrease in kf-iodate value of treated surface soils indicates that surface sorbed NOM enhances iodate adsorption onto surface soil. By contrast, kf-iodate value increases in several H2O2-treated sediment samples, which was considered to result from exposed rod-like minerals rich in Fe/Al oxyhydroxide/oxides. After chemical removal of organic-mineral complexes, the lowest kf-iodate value for both treated surface soils and sediments suggests the dominant role of organic-mineral complexes on controlling the iodate geochemical behavior. In comparison with iodate, iodide exhibited lower affinities on all (un)treated soil/sediment samples. The understanding of different geochemical behaviors of iodine species helps to explain the occurrence of high iodine groundwater with iodate and iodide as the main species in shallow (oxidizing conditions) and deep (reducing conditions) groundwater.

Assessing the dynamics of the upper soil layer relative to soil management practices

USDA-ARS?s Scientific Manuscript database

The upper layer of the soil is the critical interface between the soil and the atmosphere and is the most dynamic in response to management practices. One of the soil properties is the stability of the aggregates because this property controls infiltration of water and exchange of gases. An aggregat...

The distribution of soil phosphorus for global biogeochemical modeling

DOE PAGES

Yang, Xiaojuan; Post, Wilfred M.; Thornton, Peter E.; ...

2013-04-16

We discuss that phosphorus (P) is a major element required for biological activity in terrestrial ecosystems. Although the total P content in most soils can be large, only a small fraction is available or in an organic form for biological utilization because it is bound either in incompletely weathered mineral particles, adsorbed on mineral surfaces, or, over the time of soil formation, made unavailable by secondary mineral formation (occluded). In order to adequately represent phosphorus availability in global biogeochemistry–climate models, a representation of the amount and form of P in soils globally is required. We develop an approach that buildsmore » on existing knowledge of soil P processes and databases of parent material and soil P measurements to provide spatially explicit estimates of different forms of naturally occurring soil P on the global scale. We assembled data on the various forms of phosphorus in soils globally, chronosequence information, and several global spatial databases to develop a map of total soil P and the distribution among mineral bound, labile, organic, occluded, and secondary P forms in soils globally. The amount of P, to 50cm soil depth, in soil labile, organic, occluded, and secondary pools is 3.6 ± 3, 8.6 ± 6, 12.2 ± 8, and 3.2 ± 2 Pg P (Petagrams of P, 1 Pg = 1 × 10 15g) respectively. The amount in soil mineral particles to the same depth is estimated at 13.0 ± 8 Pg P for a global soil total of 40.6 ± 18 Pg P. The large uncertainty in our estimates reflects our limited understanding of the processes controlling soil P transformations during pedogenesis and a deficiency in the number of soil P measurements. In spite of the large uncertainty, the estimated global spatial variation and distribution of different soil P forms presented in this study will be useful for global biogeochemistry models that include P as a limiting element in biological production by providing initial estimates of the available soil P for plant uptake and microbial utilization.« less

Effects of adjacent land-use types on the distribution of soil organic carbon stocks in the montane area of central Taiwan.

PubMed

Chen, Chiou-Pin; Juang, Kai-Wei; Cheng, Chih-Hsin; Pai, Chuang-Wen

2016-12-01

Soil organic carbon (SOC) stocks can be altered through reforestation and cropping. We estimated the effects of land use on SOC stocks after natural deciduous forests replaced by crops and coniferous plantations by examining the vertical distribution of SOC stocks at different depth intervals in an adjacent Oolong tea (Camellia sinensis L.) plantation, Moso bamboo (Phyllostachys pubescens) forest, Japanese cedar (Cryptomeria japonica) forest, and Taiwania (Taiwania cryptomerioides) forest in central Taiwan. The main soil characteristics, soil nitrogen (N) content, and soil carbon to nitrogen (C/N) ratio were also determined. Different land uses resulted in significantly higher bulk density, lower cation exchange capacity, SOC, soil N, soil C/N ratio, and SOC stocks in croplands compared to forestlands. Due to the long-term application of chemical fertilizers, a significantly lower soil pH was found in the tea plantation. Croplands had a lower soil C/N ratio because of less C input into the soil and a higher mineralization rate of organic carbon during cultivation. Similar SOC stocks were found in Taiwania and Japanese cedar forests (148.5 and 151.8 Mg C ha -1 , respectively), while the tea plantation had comparable SOC stocks to the bamboo forest (101.8 and 100.5 Mg C ha -1 , respectively). Over 40% of SOC stocks was stored in croplands and over 56% was stored in forestland within the upper 10 cm of soil. Coniferous plantations can contribute to a higher SOC stock than croplands, and a significant difference can be found in the top 0-5 cm of soil.

Soil mixing and transport increase inventories of mineral surface area and organic carbon, with systematic shifts in C/N, δ13C, and δ15N, along a forested hillslope transect

NASA Astrophysics Data System (ADS)

Fisher, B.; Yoo, K.; Aufdenkampe, A. K.; Nater, E. A.; Aalto, R. E.; Marquard, J.

2017-12-01

The quantity of organic carbon (OC) per unit of mineral surface area (OC/SA) and the inventory of organic carbon increased by a factor of 2-3 as result of soil mixing due to soil creep, erosional movement, and in situ mixing process in a soil transect in a first-order forested watershed in the Christina River Basin Critical Zone Observatory. In the uppermost 5 meters, 50-75% of mineral specific surface area was contributed by citrate-dithionate extractable forms of iron and aluminum that comprised less than 2.5% of the total sample mass. As soils were redistributed to depositional landscape positions, mixing processes systematically decreased C/N and enriched stable isotopes of C ( δ13C) and N ( δ15N). Radiocarbon (14C) concentration of light and dense fraction OC (divided at 2.0 g cm-3), increased with depth, but results of light fraction radiocarbon were obscured by 3000-year-old charcoal. Short range order Fe- and Al-bearing minerals contributed the vast majority of specific surface area, and this finding has implications for the stability and longevity of organomineral complexes. We identified a strong correlation between C/N and the ratio of OC to mineral surface area (OC/SA), indicating that the processes that associate organic matter and minerals are fundamentally linked with organic matter composition, and both properties may provide a proxy for organic matter stabilization by soil minerals.

Robust Linuron Degradation in On-Farm Biopurification Systems Exposed to Sequential Environmental Changes▿

PubMed Central

Sniegowski, Kristel; Bers, Karolien; Ryckeboer, Jaak; Jaeken, Peter; Spanoghe, Pieter; Springael, Dirk

2011-01-01

On-farm biopurification systems (BPS) treat pesticide-contaminated wastewater of farms through biodegradation. Adding pesticide-primed soil has been shown to be beneficial for the establishment of pesticide-degrading populations in BPS. However, no data exist on the response of pesticide-degrading microbiota, either endogenous or introduced with pesticide-primed soil, when BPS are exposed to expected less favorable environmental conditions like cold periods, drought periods, and periods without a pesticide supply. Therefore, the response of microbiota mineralizing the herbicide linuron in BPS microcosm setups inoculated either with a linuron-primed soil or a nonprimed soil to a sequence of such less favorable conditions was examined. A period without linuron supply or a drought period reduced the size of the linuron-mineralizing community in both setups. The most severe effect was recorded for the setup containing nonprimed soil, in which stopping the linuron supply decreased the linuron degradation capacity to nondetectable levels. In both systems, linuron mineralization rapidly reestablished after conventional operation conditions were restored. A cold period and feeding with a pesticide mixture did not affect linuron mineralization. The changes in the linuron-mineralizing capacity in microcosms containing primed soil were associated with the dynamics of a particular Variovorax phylotype that previously had been associated with linuron mineralization. This study suggests that the pesticide-mineralizing community in BPS is robust in stress situations imposed by changes in environmental conditions expected to occur on farms. Moreover, it suggests that, in cases where effects do occur, recovery is rapid after restoring conventional operation conditions. PMID:21803897

A study of contaminated soils near Crucea-Botus, ana uranium mine (East Carpathians, Romania): metal distribution and partitioning of natural actinides with implications for vegetation uptake

NASA Astrophysics Data System (ADS)

Petrescu, L.; Bilal, E.

2012-04-01

Between 1962 and 2009, National Company of Uranium - CNU, the former Romanian Rare Metals Mining Company, mined over 1,200,000 tones of pitchblende ore in the East Carpathians (Crucea-Botušana area, Bistrita Mountains). The exploration and mining facilities include 32 adits, situated between 780 and 1040 m above sea level. Radioactive waste resulted from mining are disposed next to the mining facilities. Mine dumps (32) cover an area of 364,000 square meters and consist of waste rock (rocks with sub-economic mineralization) and gangue minerals. Older dumps (18) have been already naturally reclaimed by forest vegetation, which played an important role in stabilizing the waste dump cover and in slowing down the uranium migration processes. The soils samples have been collected from different mine dumps in the Crucea-Botušana uranium deposit, mainly from 1, 4, 5, 6, 8, 9, 1/30 and 950 mine waste galleries. Soil samples were collected from the upper part and slope at each mine dump, from the vegetation root zones. Total uranium concentration in soils collected from Crucea-Botušana site ranged from 6.10 to 680.70 ppm, with a mean of 52.48 ppm (dry wt.). Total thorium varies between 7.70 and 115.30 ppm (dry wt.). This indicates that the adsorption of the radioactive elements by the soils is high and variable, influenced by the ore dump - sample relationship. The sequential extraction has emphasized the fact that the uranium is associated with all the mineral fractions present in the soil samples. A great percentage of U can be found in the carbonate (21.77%), organic (15.04%) and oxides fractions (15.88%) - in accordance with the high absorbed/adsorbed properties of this element. The percentage of uranium detected in the exchangeable fraction is rather small - 2.16%. It is also to be expected that the uranium should be irreversible adsorbed by the organic matter and by the clay minerals due to its ionic radius and to its positive charge. The fact that 21.77% of the total uranium can be found in the specifically absorbed and carbonate bound fraction, indicated the important role played by the carbonates in the retention of U; one the other hand this fraction is liable to release the uranium if the pH should happen to change. Thorium appear in high-enough concentration in the soil is scarcely available because 70.29% is present in residual fraction, and about 21.78% in the crystalline iron oxides occluded fraction and organically and secondary sulfide bound fraction. This is certainly due to the fact that this naturally occurring radionuclide can be associated with relatively insoluble mineral phases like alumino-silicates and refractory oxides. Its association with the organic matter (10.93%) suggests that it can form soluble organic complexes that can facilitate its removal by the stream waters. Grounded on these results, we were able to prove that the examined mine dumps can represent an impact on the environment, which constitute an argument in favor of the initiation of a program of remedying the quality of the environment from this mining zone. Although from our research it resulted that the natural actinides does not concentrate in the exchangeable fraction (Th) or it concentrates very little in it (U), the isolation of the mineral fraction of soil rich in U and Th helps us in the future identification of the links between the bioavailability and the pedogenesis, connections which control the cycle of the radioactive metals.

Effect of herbicide concentration and organic and inorganic nutrient amendment on the mineralization of mecoprop, 2,4-D and 2,4,5-T in soil and aquifer samples.

PubMed

de Lipthay, Julia R; Sørensen, Sebastian R; Aamand, Jens

2007-07-01

The impact of the herbicide concentration (0.10-10,000 microg kg(-1)) and addition of organic and inorganic nutrients on mecoprop, 2,4-D and 2,4,5-T mineralization in aquifer and soil samples was studied in laboratory experiments. Generally, 2,4-D was most rapidly mineralized followed by mecoprop and 2,4,5-T. A shift from non-growth to growth-linked mineralization kinetics was observed in aquifer sediment with 2,4-D concentrations >0.10 microg kg(-1) and mecoprop concentrations >10.0 microg kg(-1). The shift was apparent at higher herbicide concentrations in soil coinciding with a lower bioavailable fraction and a higher herbicide sorption to soil. Herbicide addition did not affect the bacterial density, although 2,4-D and mecoprop applied at 10,000 microg kg(-1) stimulated growth of specific degraders. Generally, nutrient amendments did not stimulate mineralization at the lowest herbicide concentrations. In contrast, the mineralization rate of higher herbicide concentrations was significantly stimulated by the amendment of inorganic nutrients.

Particle size and X-ray analysis of Feldspar, Calvert, Ball, and Jordan soils

NASA Technical Reports Server (NTRS)

Chapman, R. S.

1977-01-01

Pipette analysis and X-ray diffraction techniques were employed to characterize the particle size distribution and clay mineral content of the feldspar, calvert, ball, and jordan soils. In general, the ball, calvert, and jordan soils were primarily clay size particles composed of kaolinite and illite whereas the feldspar soil was primarily silt-size particles composed of quartz and feldspar minerals.

Soil variability along a nitrogen mineralization and nitrification gradient in a nitrogen-saturated hardwood forest

Treesearch

Frank S. Gilliam; Nikki L. Lyttle; Ashley Thomas; Mary Beth Adams

2005-01-01

Some N-saturated watersheds of the Fernow Experimental Forest (FEF), West Virginia, exhibit a high degree of spatial heterogeneity in soil N processing. We used soils from four sites at FEF representing a gradient in net N mineralization and nitrification to consider the causes and consequences of such spatial heterogeneity. We collected soils with extremely high vs....

Relationship among Phosphorus Circulation Activity, Bacterial Biomass, pH, and Mineral Concentration in Agricultural Soil.

PubMed

Adhikari, Dinesh; Jiang, Tianyi; Kawagoe, Taiki; Kai, Takamitsu; Kubota, Kenzo; Araki, Kiwako S; Kubo, Motoki

2017-12-04

Improvement of phosphorus circulation in the soil is necessary to enhance phosphorus availability to plants. Phosphorus circulation activity is an index of soil's ability to supply soluble phosphorus from organic phosphorus in the soil solution. To understand the relationship among phosphorus circulation activity; bacterial biomass; pH; and Fe, Al, and Ca concentrations (described as mineral concentration in this paper) in agricultural soil, 232 soil samples from various agricultural fields were collected and analyzed. A weak relationship between phosphorus circulation activity and bacterial biomass was observed in all soil samples ( R ² = 0.25), and this relationship became significantly stronger at near-neutral pH (6.0-7.3; R ² = 0.67). No relationship between phosphorus circulation activity and bacterial biomass was observed at acidic (pH < 6.0) or alkaline (pH > 7.3) pH. A negative correlation between Fe and Al concentrations and phosphorus circulation activity was observed at acidic pH ( R ² = 0.72 and 0.73, respectively), as well as for Ca at alkaline pH ( R ² = 0.64). Therefore, bacterial biomass, pH, and mineral concentration should be considered together for activation of phosphorus circulation activity in the soil. A relationship model was proposed based on the effects of bacterial biomass and mineral concentration on phosphorus circulation activity. The suitable conditions of bacterial biomass, pH, and mineral concentration for phosphorus circulation activity could be estimated from the relationship model.

Sorption of Hydrophobic Organic Compounds on Natural Sorbents and Organoclays from Aqueous and Non-Aqueous Solutions: A Mini-Review

PubMed Central

Moyo, Francis; Tandlich, Roman; Wilhelmi, Brendan S.; Balaz, Stefan

2014-01-01

Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the context of the sorption of HOCs onto clay minerals from aqueous and non-aqueous solutions. PMID:24821385

Changes in substrate availability drive carbon cycle response to chronic warming

DOE PAGES

Pold, Grace; Grandy, A. Stuart; Melillo, Jerry M.; ...

2017-03-22

As earth's climate continues to warm, it is important to understand how the capacity of terrestrial ecosystems to retain carbon (C) will be affected. We combined measurements of microbial activity with the concentration, quality, and physical accessibility of soil carbon to microorganisms to evaluate the mechanisms by which more than two decades of experimental warming has altered the carbon cycle in a Northeast US temperate deciduous forest. We have found that concentrations of soil organic matter were reduced in both the organic and mineral soil horizons. The molecular composition of the carbon was altered in the mineral soil with significantmore » reductions in the relative abundance of polysaccharides and lignin, and an increase in lipids. Mineral-associated organic matter was preferentially depleted by warming in the top 3 cm of mineral soil. We found that potential extracellular enzyme activity per gram of soil at a common temperature was generally unaffected by warming treatment. However, by measuring potential extracellular enzyme activities between 4 and 30 °C, we found that activity per unit microbial biomass at in-situ temperatures was increased by warming. This was associated with a tendency for microbial biomass to decrease with warming. These results indicate that chronic warming has reduced soil organic matter concentrations, selecting for a smaller but more active microbial community increasingly dependent on mineral-associated organic matter.« less

Microbial activity in Alaskan taiga soils contaminated by crude oil in 1976

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monroe, E.M.; Lindstrom, J.E.; Brown, E.J.

1995-12-31

Biodegradation, often measured via microbial activity, includes destruction of environmental pollutants by living microorganisms and is dependent upon many physical and chemical factors. Effects of mineral nutrients and organic matter on biodegradation of Prudhoe Bay crude oil were investigated at a nineteen-year-old oil spill site in Alaskan taiga. Microcosms of two different soil types from the spill site; one undeveloped soil with forest litter and detritus (O horizon) and one more developed with lower organic content (A horizon), were treated with various nitrogen and phosphorus amendments, and incubated for up to six weeks. Each microcosm was sampled periodically and assayedmore » for hydrocarbon mineralization potential using radiorespirometry, for total carbon dioxide respired using gas chromatography, and for numbers of hydrocarbon-degrading bacteria and heterotrophic bacteria using most probable number counting techniques. Organic matter in the O horizon soil along with combinations of mineral nutrients were found to stimulate microbial activity. No combination of mineral nutrient additions to the A horizon soil stimulated any of the parameters above those measured in control microcosms. The results of this study indicate that adding mineral nutrients and tilling the O horizon into the A horizon of subarctic soils contaminated with crude oil, would stimulate microbial activity, and therefore the biodegradation potential, ultimately increasing the rate of destruction of crude oil in these soils.« less

Changes in substrate availability drive carbon cycle response to chronic warming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pold, Grace; Grandy, A. Stuart; Melillo, Jerry M.

As earth's climate continues to warm, it is important to understand how the capacity of terrestrial ecosystems to retain carbon (C) will be affected. We combined measurements of microbial activity with the concentration, quality, and physical accessibility of soil carbon to microorganisms to evaluate the mechanisms by which more than two decades of experimental warming has altered the carbon cycle in a Northeast US temperate deciduous forest. We have found that concentrations of soil organic matter were reduced in both the organic and mineral soil horizons. The molecular composition of the carbon was altered in the mineral soil with significantmore » reductions in the relative abundance of polysaccharides and lignin, and an increase in lipids. Mineral-associated organic matter was preferentially depleted by warming in the top 3 cm of mineral soil. We found that potential extracellular enzyme activity per gram of soil at a common temperature was generally unaffected by warming treatment. However, by measuring potential extracellular enzyme activities between 4 and 30 °C, we found that activity per unit microbial biomass at in-situ temperatures was increased by warming. This was associated with a tendency for microbial biomass to decrease with warming. These results indicate that chronic warming has reduced soil organic matter concentrations, selecting for a smaller but more active microbial community increasingly dependent on mineral-associated organic matter.« less

Effect of irrigation water salinity on the organic carbon mineralization in soil (laboratory incubation)

NASA Astrophysics Data System (ADS)

Mancer, Halima; Bouhoun, Mustapha Daddi

2018-05-01

In a laboratory study, the impact of salts on mineralization of organic carbon of soil was examined through the monitoring of the amount of CO2-C released from soil. The soil used was classified as a nonsaline soil which has been irrigated with artificially salinized water, a factorial combination of three types of salts (NaCl, MgCl2, CaCl2) with three levels of electrical conductivities (3, 6, and 9 dS.m-1) was used to assess the Carbon mineralization. The incubation was carried out under aerobic conditions and at a constant temperature of 28 °C during 70 days with moisture adjusted to 2/3 of the field capacity. No significant (P > 0.05) variation in the amount of CO2-C release from soil was observed until day 56 of the incubation, but it was significantly different due to the irrigation with salt solutions during the days: 70 (p ≤ 0.05). The results suggest that the rate of C-CO2 evolution decreased with the increase in water salinity compared to the control. Also this decrease of C-mineralization in the soils irrigated by the salts solutions of NaCl was the greatest compared to the other two salts (CaCl2, and MgCl2). These results suggest that C mineralization depended on the type of salts as well as the duration of incubation.

Observations and modelling of thoron and its progeny in the soil-atmosphere-plant system.

PubMed

Baldacci, A E; Gattavecchia, E; Kirchner, G

2010-11-01

Samples of pasture vegetation, mainly Trifolium pratensis, were collected at the Botanic Garden of the University of Bologna during the period 1998-2000 and measured by gamma-spectrometry for determining thoron progeny. Concentrations of (212)Pb were between 1.5 and 20 Bq m(-2), with individual peaks up to 70 Bq m(-2). Soil samples were collected at the same location and physically characterised. Their chemical composition (particularly Th and U) was determined by X-ray fluorescence spectroscopy. Lead-212 on plants mainly originates from dry and wet deposition of this isotope generated in the lower atmosphere by the decay of its short-lived precursor (220)Rn, which is produced in the upper soil layers as a member of the natural thorium decay chain and exhales into the atmosphere. Concentrations of (220)Rn in the atmosphere depend on (1) the amount of Th present in soil, (2) the radon fraction which escapes from the soil minerals into the soil pore space, (3) its transport into the atmosphere, and (4) its redistribution within the atmosphere. The mobility of radon in soil pore space can vary by orders of magnitude depending on the soil water content, thus being the main factor for varying concentrations of (220)Rn and (212)Pb in the atmosphere. We present a simple model to predict concentrations of thoron in air and its progeny deposited from the atmosphere, which takes into account varying soil moisture contents calculated by the OPUS code. Results of this model show close agreement with our observations.

Gone or just out of sight? The apparent disappearance of aromatic litter components in soils

NASA Astrophysics Data System (ADS)

Klotzbücher, Thimo; Kalbitz, Karsten; Cerli, Chiara; Hernes, Peter J.; Kaiser, Klaus

2016-07-01

Uncertainties concerning stabilization of organic compounds in soil limit our basic understanding on soil organic matter (SOM) formation and our ability to model and manage effects of global change on SOM stocks. One controversially debated aspect is the contribution of aromatic litter components, such as lignin and tannins, to stable SOM forms. In the present opinion paper, we summarize and discuss the inconsistencies and propose research options to clear them. Lignin degradation takes place stepwise, starting with (i) depolymerization and followed by (ii) transformation of the water-soluble depolymerization products. The long-term fate of the depolymerization products and other soluble aromatics, e.g., tannins, in the mineral soils is still a mystery. Research on dissolved organic matter (DOM) composition and fluxes indicates dissolved aromatics are important precursors of stable SOM attached to mineral surfaces and persist in soils for centuries to millennia. Evidence comes from flux analyses in soil profiles, biodegradation assays, and sorption experiments. In contrast, studies on composition of mineral-associated SOM indicate the prevalence of non-aromatic microbial-derived compounds. Other studies suggest the turnover of lignin in soil can be faster than the turnover of bulk SOM. Mechanisms that can explain the apparent fast disappearance of lignin in mineral soils are, however, not yet identified. The contradictions might be explained by analytical problems. Commonly used methods probably detect only a fraction of the aromatics stored in the mineral soil. Careful data interpretation, critical assessment of analytical limitations, and combined studies on DOM and solid-phase SOM could thus be ways to unveil the issues.

Gone or just out of sight? The apparent disappearance of aromatic litter components in soils

NASA Astrophysics Data System (ADS)

Klotzbücher, Thimo; Kalbitz, Karsten; Cerli, Chiara; Hernes, Peter; Kaiser, Klaus

2016-04-01

Uncertainties concerning stabilization of organic compounds in soil limit our basic understanding on soil organic matter (SOM) formation and our ability to model and manage effects of global change on SOM stocks. One controversially debated aspect is the contribution of aromatic litter components, such as lignin and tannins, to stable SOM forms. Here we summarize and discuss the inconsistencies and propose research options to clear them. Lignin degradation takes place step-wise, starting with (i) depolymerisation, followed by (ii) transformation of the water-soluble depolymerization products. The long-term fate of the depolymerization products and other soluble aromatics, e.g., tannins, in the mineral soils is still a mystery. Research on dissolved organic matter (DOM) composition and fluxes indicates dissolved aromatics are important precursors of stable SOM attached to mineral surfaces and persist in soils for centuries to millennia. Evidence comes from flux analyses in soil profiles, biodegradation assays, and sorption experiments. In contrast, studies on composition of mineral-associated SOM indicate the prevalence of non-aromatic microbial-derived compounds. Other studies suggest the turnover of lignin in soil can be faster than the turnover of bulk SOM. Mechanisms that can explain the apparent fast disappearance of lignin in mineral soils are, however, not yet identified. The contradictions might be explained by analytical problems. Commonly used methods probably detect only a fraction of the aromatics stored in the mineral soil. Careful data interpretation, critical assessment of analytical limitations, and combined studies on DOM and solid-phase SOM could thus be ways to unveil the issues.

Soil mineral alters the effect of Cd on the alkaline phosphatase activity.

PubMed

Tan, Xiangping; He, Yike; Wang, Ziquan; Li, Chenghui; Kong, Long; Tian, Haixia; Shen, Weijun; Megharaj, Mallavarapu; He, Wenxiang

2018-05-30

The toxicity of heavy metals (HMs) to soil enzymes is directly influenced by the status of the enzyme (free vs. immobilized on minerals) and the duration of exposure. However, little information is available on the interaction effect of HMs, mineral, and exposure time on soil enzyme activities. We investigated the interaction mechanism of alkaline phosphatase (ALP) with minerals (montmorillonite and goethite) and the response of free and immobilized ALP to cadmium (Cd) toxicity under different exposure times. The adsorption isotherms of ALP on both minerals were L-type. The maximum adsorption capacity of goethite for ALP was 3.96 times than montmorillonite, although both had similar adsorption constant (K). Goethite showed a greater inhibitory effect on ALP activity than montmorillonite. The toxicity of Cd to free- and goethite-ALP was enhanced with increasing exposure time, indicating a time-dependent inhibition. However, Cd toxicity to montmorillonite-ALP was not affected by the exposure time. The inhibition of Cd to soil enzyme activity is influenced by the properties of mineral complexes and the duration of exposure. A further understanding of the time pattern of HMs toxicity is helpful for accurately assessing the hazards of HMs to soil enzyme activity. Copyright © 2018 Elsevier Inc. All rights reserved.

Nitrogen stabilization in organo-mineral fractions from soils with different land uses

NASA Astrophysics Data System (ADS)

Giannetta, Beatrice; Zaccone, Claudio; Rovira, Pere; Vischetti, Costantino; Plaza, César

2017-04-01

Understanding the processes that control quantity and quality of soil organic matter (SOM) interacting with mineral surfaces is of paramount importance. Although several physical fractionation methods have been proposed to date to obtain fractions that mirror SOM degree of stability and protection, a detailed quantification of stabilisation modes through which SOM bounds to the mineral matrix is still lacking. In this research we determined C and N distribution in several soils including coniferous and broadleaved forest soils, grassland soils, technosols and an agricultural soil amended with biochar at rates of 0 and 20 t/ha in a factorial combination with two types of organic amendment (municipal solid waste compost and sewage sludge). We performed a physical size fractionation by ultrasonic dispersion and wet sieving, splitting particles into four different size fractions: coarse sand (2000-200 µm diameter), fine sand (200-50 µm), coarse silt (50-20 µm) and fine silt plus clay (<20 µm). The fraction <20 µm, that includes organo-mineral complexes, was then subjected to the organo-mineral fractionation method (SOF) proposed by Lopez-Sangil and Rovira (2013), in order to define the importance of different stabilization modes. This method, in fact, allows resolving the nature of different bonds between mineral and organic components by the use of sequential extractions with chemical reagents (potassium sulphate, sodium tetraborate, sodium pyrophosphate, sodium hydroxide, sodium hydroxide after weak acid attack, sodium hydroxide after sodium dithionite pretreatment, and sodium hydroxide after hydrofluoric acid pretreatments). Elemental analysis (CHN) was then carried out on SOM pools isolated from different fractions. Preliminary data show that, for all land uses in general, and for grassland soils in particular, most of the total N is found in organo-mineral complexes (fraction <20 µm). The total N content of the size fractions, especially of the <20um fraction, was highly correlated with whole soil N content. Although a small N loss was observed during the fractionation procedure, especially in N-rich samples, and data analysis is still ongoing, these preliminary results could already represent a valuable insight into organic N stabilization by mineral matrix.

Response to elevated CO2 in the temperate C3 grass Festuca arundinaceae across a wide range of soils

PubMed Central

Nord, Eric A.; Jaramillo, Raúl E.; Lynch, Jonathan P.

2015-01-01

Soils vary widely in mineral nutrient availability and physical characteristics, but the influence of this variability on plant responses to elevated CO2 remains poorly understood. As a first approximation of the effect of global soil variability on plant growth response to CO2, we evaluated the effect of CO2 on tall fescue (Festuca arundinacea) grown in soils representing 10 of the 12 global soil orders plus a high-fertility control. Plants were grown in small pots in continuously stirred reactor tanks in a greenhouse. Elevated CO2 (800 ppm) increased plant biomass in the high-fertility control and in two of the more fertile soils. Elevated CO2 had variable effects on foliar mineral concentration—nitrogen was not altered by elevated CO2, and phosphorus and potassium were only affected by CO2 in a small number of soils. While leaf photosynthesis was stimulated by elevated CO2 in six soils, canopy photosynthesis was not stimulated. Four principle components were identified; the first was associated with foliar minerals and soil clay, and the second with soil acidity and foliar manganese concentration. The third principle component was associated with gas exchange, and the fourth with plant biomass and soil minerals. Soils in which tall fescue did not respond to elevated CO2 account for 83% of global land area. These results show that variation in soil physical and chemical properties have important implications for plant responses to global change, and highlight the need to consider soil variability in models of vegetation response to global change. PMID:25774160

From bulk soil to intracrystalline investigation of plant-mineral interaction

NASA Astrophysics Data System (ADS)

Lemarchand, D.; Voinot, A.; Chabaux, F.; Turpault, M.

2011-12-01

Understanding the controls and feedbacks regulating the flux of matter between bio-geochemical reservoirs in forest ecosystems receives a fast growing interest for the last decades. A complex question is to understand how minerals and vegetation interact in soils to sustain life and, to a broader scope, how forest ecosystems may respond to human activity (acid rain, harvesting,...) and climate perturbations (temperature, precipitation,...). Many mineralogical and biogeochemical approaches have longtime been developed, and occasionally coupled, in order to investigate the mechanisms by which chemical elements either are exchanged between soil particles and solutions, or are transferred to plants or to deeper soil layers and finally leave the system. But the characterization of particular processes like the contribution of minor reactive minerals to plant nutrition and global fluxes or the mechanisms by which biology can modify reaction rates and balance the bioavailability of nutrients in response to environmental perturbation sometimes fails because of the lack of suitable tracers. Recent analytical and conceptual advances have opened new perspectives for the use of light "non traditional" stable isotopes. Showing a wild range of concentrations and isotopic compositions between biogeochemical reservoirs in forest ecosystem, boron has physico-chemical properties particularly relevant to the investigation of water/rock interactions even when evolving biologically-mediated reactions. In this study, we focused on the distribution of boron isotopes from intracrystalline to bulk soil scales. An overview of the boron distribution and annual fluxes in the soil-plant system clearly indicates that the vegetation cycling largely controls the mobility of boron. We also observe that the mineral and biological B pools have drastically different isotopic signature that makes the transfer of B between them very easy to follow. In particular, the podzol soil we analyzed shows a clear contribution of vegetation-recycled B to neoformed mineral phases, whereas B in minerals from the brown acidic soil rather indicates predominant mineral dissolution with little or even no B supply from the soil solution. If B isotopes thus proved their sensitivity to the soil forming conditions, a simple isotopic budget also demonstrates that the isotopic signature shown by the vegetation cannot result from fractionation during boron absorption. Analyses of B isotopes within intracrystalline phyllosilicate minerals further identify the interfoliar layers as the major source of B during plant nutrition. Additionally, weathering experiments placing phyllosilicates in contact with various alteration agents (protons, organic acid or siderophore) point to the role of the latters as likely responsible for the boron liberation from the phyllosilicate interfoliar layers. This scenario gives the phyllosilicate interfoliar layers a central function in the plant nutrition in context studied here of soils developed on granitic bedrocks. It also implies a very dynamic system in which plants and minerals can exchange matter over very short periods of time.

Humus and nitrogen in soddy-podzolic soils of different agricultural lands in Perm region

NASA Astrophysics Data System (ADS)

Zav'yalova, N. E.

2016-11-01

Heavy loamy soddy-podzolic soils (Eutric Albic Retisols (Abruptic, Loamic, Cutanic)) under a mixed forest, a grass-herb meadow, a perennial legume crop (fodder galega, Galéga orientalis), and an eightcourse crop rotation (treatment without fertilization) have been characterized by the main fertility parameters. Differences have been revealed in the contents of humus and essential nutrients in the 0- to 20- and 20- to 40-cm layers of soils of the studied agricultural lands. The medium acid reaction and the high content of ash elements and nitrogen in stubble-root residues of legume grasses favor the accumulation of humic acids in the humus of soil under fodder galega; the CHA/CFA ratio is 0.95 in the 0- to 20-cm layer and 0.81 in the 20- to 40-cm layer (under forest, 0.61 and 0.41, respectively). The nitrogen pool in the upper horizon of the studied soddy-podzolic soil includes 61-76% nonhydrolyzable nitrogen and 17-25% difficultly hydrolyzable nitrogen. The content of easily hydrolyzable nitrogen varies depending on the type of agricultural land from 6% in the soil under mixed forest to 10% under crop rotation; the content of mineral nitrogen varies from 0.9 to 1.9%, respectively. The long-term use of plowland in crop rotation and the cultivation of perennial legume crop have increased the content of hydrolyzable nitrogen forms but have not changed the proportions of nitrogen fractions characteristic of this soil type.

A Fourier-Transform Infrared Study of Biochar Aging in Soils

PubMed Central

Singh, B.; Fang, Y.; Johnston, C.T.

2018-01-01

We used diffuse reflectance Fourier-transform infrared (DR-FTIR) spectroscopy, X-ray diffraction (XRD), and chemical and isotopic analyses to characterize the light fraction of four contrasting soils (control and biocharamended soils) to determine changes in biochar properties after aging. Two Eucalyptus saligna Sm. wood biochars, produced at 450°C (B450) and 550°C (B550), were incubated separately in each of the four soils for up to 12 mo at 20, 40, and 60°C. Total C and isotopic (δ13C) methods were used to quantify the amounts of biochar C and native C mineralized during incubation. The DR-FTIR spectra of the light fraction showed distinct absorption bands representing native soil organic C, biochar C, and mineral constituents present in the soils; the mineral bands were consistent with XRD data of the clay fraction of the four soils. Analysis of the DR-FTIR spectra in the ν(C–H) bands showed that the ratio of the aromatic ν(C–H) bands systematically increased relative to the aliphatic ν(C–H) bands with increasing mineralization of biochar C in the B550 amended soils, and this relationship was unique for each soil type. In contrast, this relationship was not observed for the B450 amended soils that contained a relatively smaller proportion of aromatic C. PMID:29657354

Magnetism of soils applied for estimation of erosion at an agricultural land

NASA Astrophysics Data System (ADS)

Kapicka, Ales; Dlouha, Sarka; Grison, Hana; Jaksik, Ondrej; Kodesova, Radka; Petrovsky, Eduard

2013-04-01

A detailed field study on small test site of agricultural land situated in loess region in Southern Moravia (Czech Republic), followed by laboratory analyses, has been carried out in order to test the applicability of magnetic methods in soil erosion estimation. The approach is based on the well-established differentiation in magnetic signature of topsoil from subsoil horizons as a result of "in situ" formation of strongly magnetic iron oxides e.g. (Maher 1986). Introducing a simple tillage homogenization model for predicting magnetic signal after uniform mixing of soil material as a result of tillage and subsequent erosion, Royall (2001) showed that magnetic susceptibility and its frequency dependence can be used to estimate soil loss. Haplic Chernozem is an original dominant soil unit in the wider area, nowadays progressively transformed into different soil units along with intensive soil erosion. The site was characterized by a flat upper part while the middle part, formed by a substantive side valley, is steeper (up to 15°). The side valley represented a major line of concentrated runoff emptying into a colluvial fan (Zadorova et al., 2011; Jaksik et al., 2011). Field measurements of magnetic susceptibility were carried out on regular grid, resulting in 101 data points. Bulk soil material for laboratory investigation was gathered from all grid points. Mass specific magnetic susceptibility χ and its frequency dependence kFD was used to estimate the significance of SP ferrimagnetic particles of pedogenic origin. Thermomagnetic analyses, hysteresis measurement and SEM were used in order to determine dominant ferrimagnetic carriers in top-soil and sub-soil layers. Strong correlation was found between the volume magnetic susceptibility (field measurement) and mass specific magnetic susceptibility measured in the laboratory (R2 = 0.80). At the same time, no correlations were found between the values of kFD and mass specific susceptibility. Values of organic carbon content, pHKCl and magnetic susceptibly are spatially distributed depending on terrain position. Higher values of magnetic susceptibly and organic carbon content were measured at the flat upper part (where the original top horizon remained). The lowest values of organic carbon content and magnetic susceptibly were obtained on the steep valley sides. Here the original topsoil was eroded and mixed by tillage with the soil substrate (loess). Regression analysis showed positive correlation between the organic carbon content and volume magnetic susceptibility (R2= 0.89). Vertical distribution of magnetic susceptibility along the selected transect was measured using SM400 soil kappameter (Petrovský et al., 2004). Differences between susceptibility values in undisturbed soil profiles and magnetic signal after uniform mixing of soil material as a result of tillage and erosion are fundamental for estimation of soil loss in studied test field. Acknowledgement: This study was supported by NAZV Agency of the Ministry of Agriculture of the Czech Republic through grant No QJ1230319. References. Jakšík, O., Kodešová, R., Stehlíková, I., Kapička, A. (2011). Mapování změn půdních vlastností v důsledku eroze. In: Sb. Konf. Hydrologie malého povodí 2011, (M. Šír, M. Tesař, Eds.), 183-188. Maher, B. (1986). Characterization of soils by mineral magnetic measurements. Phys Earth Planet. Int. 42, 76-92. Petrovský, E., Hůlka, Z., Kapička, A. (2004). A new tool for in situ measurements of the vertical distribution of magnetic susceptibility in soils as basis for mapping deposited dust. Environ. Tech., 25, 1021-1029. Royall, D. (2001). Use of mineral magnetic measurements to investigate soil erosion and sediment delivery in a small agricultural catchment in limestone terrain. Catena 46, 15-34. Zadorova, T., Penizek, V., Sefrna, L., Rohoskova, M., Boruvka, L. (2011). Spatial delineation of organic carbon-rich Colluvial soils in Chernozem regions by Terrain analysis and fuzzy classification, Catena, 85, 22-33

Reducing conditions can alter the source of respired carbon and stimulate decomposition in mineral soils

NASA Astrophysics Data System (ADS)

Huang, W.; Hall, S. J.

2016-12-01

Soil organic matter decomposition is widely thought to be constrained by reducing conditions in flooded wetland ecosystems. However, the potential impact of periodic reducing conditions on carbon (C) mineralization in terrestrial mineral soils that experience transient moisture saturation has received less attention. Here we incubated three Mollisols amended with C4 leaf litter at three different soil moisture levels (field capacity for the control, intermediate, and saturation) over three months in the laboratory. Soil CO2 and CH4 production and isotope ratios of CO2 (δ13CO2) were measured daily using a tunable diode laser for the first two weeks and weekly thereafter. Soil Eh dropped from 516 mV to -184 mV in the intermediate and saturated soils during the first seventeen days; iron (Fe) reduction occurred in both intermediate and saturated soils after the seventh day. Total CO2 production rate in the intermediate and saturated soils was initially lower than the control, but exceeded the control after the eleventh day. After three months, mean cumulative CO2 production was significantly higher in the intermediate soil moisture treatment (152 μmol CO2 g-1 soil, P < 0.01) and equivalent between the saturated and control soils (128 and 141 μmol CO2 g-1 soil, P = 0.11). The intermediate and saturated soils also induced substantial CH4 production. Differences in mean δ13CO2 (-14.0‰ for the control and -22.7‰ for the saturated soils) over the first two weeks (before CH4 production began) showed that CO2 production from the saturated soils was derived from different C source(s) compared to the control. These findings challenge traditional paradigms by showing that reducing conditions can enhance C mineralization, perhaps by facilitating microbial access to alternative or occluded C sources. We suggest that Fe reduction could be an important mechanism of C loss in mineral soils due to the release of adsorbed or co-precipitated organic matter during Fe solubilization.

Using (137)Cs to quantify the redistribution of soil organic carbon and total N affected by intensive soil erosion in the headwaters of the Yangtze River, China.

PubMed

Guoxiao, Wei; Yibo, Wang; Yan Lin, Wang

2008-12-01

Characteristics of soil organic carbon (SOC) and total nitrogen (total N) are important for determining the overall quality of soils. Studies on spatial and temporal variation in SOC and total N are of great importance because of global environmental concerns. Soil erosion is one of the major processes affecting the redistribution of SOC and total N in the test fields. To characterize the distribution and dynamics of SOC and N in the intensively eroded soil of the headwaters of the Yangtze River, China, we measured profiles of soil organic C, total N stocks, and (137)Cs in a control plot and a treatment plot. The amounts of SOC, (137)Cs of sampling soil profiles increased in the following order, lower>middle>upper portions on the control plot, and the amounts of total N of sampling soil profile increase in the following order: upper>middle>lower on the control plot. Intensive soil erosion resulted in a significant decrease of SOC amounts by 34.9%, 28.3% and 52.6% for 0-30cm soil layer at upper, middle and lower portions and (137)Cs inventory decreased by 68%, 11% and 85% at upper, middle and lower portions, respectively. On the treatment plot total N decreased by 50.2% and 14.6% at the upper and middle portions and increased by 48.9% at the lower portion. Coefficients of variation (CVs) of SOC decreased by 31%, 37% and 30% in the upper, middle and lower slope portions, respectively. Similar to the variational trend of SOC, CVs of (137)Cs decreased by 19.2%, 0.5% and 36.5%; and total N decreased by 45.7%, 65.1% and 19% in the upper, middle and lower slope portions, respectively. The results showed that (137)Cs, SOC and total N moved on the sloping land almost in the same physical mechanism during the soil erosion procedure, indicating that fallout of (137)Cs could be used directly for quantifying dynamic SOC and total N redistribution as the soil was affected by intensive soil erosion.

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils

NASA Astrophysics Data System (ADS)

Sauerwein, Meike; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

2010-05-01

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils Meike Sauerwein1, Alexander Hanke2, Klaus Kaiser3, Karsten Kalbitz2 1) Dept. of Soil Ecology, Bayreuth Centre of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany, meike.sauerwein@gmail.com 2) Institute of ecosystem dynamics and biodiversity, University of Amsterdam, 1018 WV, Netherlands, a.hanke@uva.nl, k.kalbitz@uva.nl 3) Soil Sciences, Martin Luther University Halle, 06099 Halle, Germany, klaus.kaiser@landw.uni-halle.de Current knowledge on dissolved organic matter (DOM) in soils is based mainly on observations and experiments in aerobic environments. Adsorption to soil minerals is an important mechanism of DOM retention and stabilization against microbial decay under oxic conditions. Under anoxic conditions where hydrous iron oxides, the potential main adsorbents of DOM, possibly dissolve, the importance of adsorption seems questionable. Therefore, we studied the adsorption of DOM to selected soil minerals and to mineral soils under oxic and anoxic conditions. In detail, we tested the following hypotheses: 1. Minerals and soils adsorb less DOM under anoxic conditions than under oxic ones. 2. The reduced adsorption under anoxic conditions is result of the smaller adsorption to hydrous Fe oxides whereas adsorption to clay minerals and Al hydroxides is not sensitive to changes in redox conditions 3. DOM adsorption will increase with the number of redox cycles, thus time of soil formation, due to increasing contents of poorly crystalline Fe oxides. This will, however, cause a stronger sensitivity to redox changes as poor crystalline Fe oxides are more reactive. 4. Aromatic compounds, being preferentially adsorbed under oxic conditions, will be less strongly adsorbed under anoxic conditions. We chose paddy soils as models because their periodically and regular exposure to changing redox cycles, with anoxic conditions during the rice growing period and oxic conditions during harvest and growth of other crops. Soils of a unique chronosequence of paddy soils (50, 300, 700 and 2000 years) in China were studied in direct comparison to non-paddy soils of the same age. In additions, selected soil minerals (goethite, ferrihydrite, amorphous Al hydroxide, hydrobiotite, nontronite and ripodolite), differing in their response to changes in redox conditions, were studied in order to indentify those mineral constituents responsible for redox-induced changes in DOM adsorption to the test soils. The DOM for the adsorption was extracted from composted rice straw as a surrogate for DOM percolating in paddy soils. Batch adsorption experiments were carried out with DOM pre-incubated to give oxic and anoxic conditions and maintaining these redox conditions during the whole procedure. The redox potential resulting from anoxic pre-incubation was about 100 mV, thus in the range of Fe reduction. Besides of dissolved organic carbon (DOC), we determined changes in the composition of DOM by the specific UV absorbance. We also analyzed main cations, anions and redox-sensitive elements to give a comprehensive picture of the effects of changing redox conditions on the dynamics of organic C, N, P, S, Fe and Al. First results indicated indeed less adsorption of DOM to Fe oxides under anoxic than under oxic conditions, with a more pronounced effect for ferrihydrite than for goethite. Maximum adsorption of DOM was more than 50% larger under oxic than under anoxic conditions. The effect was less pronounced but still detectable for clay minerals such as hydrobiotite, nontronite, and ripodolite. The specific UV absorbance of DOM contact with minerals was 20-50% stronger under anoxic than under oxic conditions. These changes in DOM composition indicated that preferential adsorption of aromatic compounds might be limited to aerated soils. We conclude that adsorption, although less strong than under oxic conditions, is an important mechanism of DOM retention also under anoxic conditions. Decreasing amounts of adsorbed DOM and changes in its composition might result in a less effective sorptive stabilization against microbial decay under anoxic than under oxic conditions.

A Comparative Analyses of Granulometry, Mineral Composition and Major and Trace Element Concentrations in Soils Commonly Ingested by Humans

PubMed Central

Ngole-Jeme, Veronica M.; Ekosse, Georges-Ivo E.

2015-01-01

This study compared the granulometric properties, mineralogical composition and concentrations of major and trace element oxides of commonly ingested soils (geophagic soil) collected from different countries with a view of understanding how varied they may be in these properties and to understand the possible health implications of ingesting them. Soil samples were collected from three different countries (South Africa, Swaziland and Democratic Republic of Congo (DRC)) and their granulometric properties, concentrations of major and trace element oxides as well as mineralogical composition determined. Differences were observed in the granulometric properties of geophagic soil from the three different countries with most of them having <20% clay content. The soils also showed varied degrees of weathering with values of Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) being between 60% and 99.9% respectively. The mineral assemblages of the soils from South Africa and Swaziland were dominated by the primary minerals quartz and feldspar whereas soils from DRC had more of kaolinite, a secondary mineral than primary minerals. Soils from DRC were associated with silt, clay, Al2O3, and CIA unlike most samples from South Africa which were associated with SiO2, sand, K2O, CaO, and MgO. The soils from Swaziland were closely associated with silt, H2O and Fe2O3(t). These associations reflect the mineralogy of the samples. These soils are not likely to serve as nutrient supplements because of the low concentrations of the nutrient elements contained. The coarse texture of the samples may also result in dental destruction during mastication. Sieving of the soils before ingestion to remove coarse particles is recommended to reduce the potential health threat associated with the ingestion of coarse-textured soils. PMID:26264010

Different low-molecular-mass organic acids specifically control leaching of arsenic and lead from contaminated soil.

PubMed

Ash, Christopher; Tejnecký, Václav; Borůvka, Luboš; Drábek, Ondřej

2016-04-01

Low-molecular-mass organic acids (LMMOA) are of key importance for mobilisation and fate of metals in soil, by functioning as ligands that increase the amount of dissolved metal in solution or by dissociation of metal binding minerals. Column leaching experiments were performed on soil polluted with As and Pb, in order to determine the specificity of LMMOA related release for individual elements, at varying organic acid concentrations. Acetic, citric and oxalic acids were applied in 12h leaching experiments over a concentration range (0.5-25 mM) to soil samples that represent organic and mineral horizons. The leaching of As followed the order: oxalic>citric>acetic acid in both soils. Arsenic leaching was attributed primarily to ligand-enhanced dissolution of mineral oxides followed by As released into solution, as shown by significant correlation between oxalic and citric acids and content of Al and Fe in leaching solutions. Results suggest that subsurface mineral soil layers are more vulnerable to As toxicity. Leaching of Pb from both soils followed the order: citric>oxalic>acetic acid. Mineral soil samples were shown to be more susceptible to leaching of Pb than samples characterised by a high content of organic matter. The leaching efficiency of citric acid was attributed to formation of stable complexes with Pb ions, which other acids are not capable of. Results obtained in the study are evidence that the extent of As and Pb leaching in contaminated surface and subsurface soil depends significantly on the types of carboxylic acid involved. The implications of the type of acid and the specific element that can be mobilised become increasingly significant where LMMOA concentrations are highest, such as in rhizosphere soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Characteristics and influencing factors of tetrachloroethylene sorption-desorption on soil and its components.

PubMed

Qiu, Zhaofu; Yang, Weiwei; He, Long; Zhao, Zhexuan; Lu, Shuguang; Sui, Qian

2016-02-01

To investigate the effects of soil structure, soil organic carbon (SOC), minerals, initial tetrachloroethylene (PCE) concentration (C0), and ionic strength (Ci) on PCE sorption-desorption, six types of soil were adopted as adsorbents, including two types of natural soil and four types of soil with most of the "soft carbon" pre-treated by H2O2 or with all SOC removed from the original soil by 600 °C ignition. The results showed that all of the sorption-desorption isotherms of PCE were non-linear within the experimental range, and the H2O2-treated samples exhibited higher non-linear sorption isotherms than those of the original soils. The hysteresis index of PCE sorption to original soil is less pronounced than that of the H2O2-treated and 600 °C-heated samples due to the entrapment of sorbate molecules in the "hard carbon" domain, together with the meso- and microporous structures within the 600 °C-heated samples. Both SOC and minerals have impacts on the sorption-desorption of PCE, and the sorption-desorption contribution rate of minerals increased with decreasing SOC content. C0 has almost no influence on the sorption to minerals of the soils, but the contribution rate of minerals decreased with increasing C0 in the desorption stage. As a result of the salting-out effect, PCE sorption capacity was increased by increasing Ci, especially when Ci ≥ 0.1 M. Moreover, desorption increased and hysteresis weakened with increasing Ci, except for the 600 °C-heated samples. In addition, no significant effect of Ci on desorption of PCE and no hysteresis was observed in this experimental range for the 600 °C-heated samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hycrest crested wheatgrass accelerates the degradation of pentachlorophenol in soil

NASA Technical Reports Server (NTRS)

Ferro, A. M.; Sims, R. C.; Bugbee, B.

1994-01-01

We investigated the effects of vegetation on the fate of pentachlorophenol (PCP) in soil using a novel high-flow sealed test system. Pentachlorophenol has been widely used as a wood preservative, and this highly toxic biocide contaminates soil and ground water at many sites. Although plants are known to accelerate the rates of degradation of certain soil contaminants, this approach has not been thoroughly investigated for PCP. The fate of [14C]PCP, added to soil at a concentration of 100 mg/kg, was compared in three unplanted and three planted systems. The plant used was Hycrest, a perennial, drought-tolerant cultivar of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. The flow-through test system allowed us to maintain a budget for 14C-label as well as monitor mineralization (breakdown to 14CO2) and volatilization of the test compound in a 155-d trial. In the unplanted systems, an average of 88% of the total radiolabel remained in the soil and leachate and only 6% was mineralized. In the planted system, 33% of the radiolabel remained in the soil plus leachate, 22% was mineralized, and 36% was associated with plant tissue (21% with the root fraction and 15% with shoots). Mineralization rates were 23.1 mg PCP mineralized kg-1 soil in 20 wk in the planted system, and for the unplanted system 6.6 mg PCP kg-1 soil for the same time period. Similar amounts of volatile organic material were generated in the two systems (1.5%). Results indicated that establishing crested wheatgrass on PCP-contaminated surface soils may accelerate the removal of the contaminant.

Different low-molecular-mass organic acids specifically control leaching of arsenic and lead from contaminated soil

NASA Astrophysics Data System (ADS)

Ash, Christopher; Tejnecký, Václav; Borůvka, Luboš; Drábek, Ondřej

2016-04-01

Low-molecular-mass organic acids (LMMOA) are of key importance for mobilisation and fate of metals in soil, by functioning as ligands that increase the amount of dissolved metal in solution or by dissociation of metal binding minerals. Column leaching experiments were performed on soil polluted with As and Pb, in order to determine the specificity of LMMOA related release for individual elements, at varying organic acid concentrations. Acetic, citric and oxalic acids were applied in 12 h leaching experiments over a concentration range (0.5-25 mM) to soil samples that represent organic and mineral horizons. The leaching of As followed the order: oxalic > citric > acetic acid in both soils. Arsenic leaching was attributed primarily to ligand-enhanced dissolution of mineral oxides followed by As released into solution, as shown by significant correlation between oxalic and citric acids and content of Al and Fe in leaching solutions. Results suggest that subsurface mineral soil layers are more vulnerable to As toxicity. Leaching of Pb from both soils followed the order: citric > oxalic > acetic acid. Mineral soil samples were shown to be more susceptible to leaching of Pb than samples characterised by a high content of organic matter. The leaching efficiency of citric acid was attributed to formation of stable complexes with Pb ions, which other acids are not capable of. Results obtained in the study are evidence that the extent of As and Pb leaching in contaminated surface and subsurface soil depends significantly on the types of carboxylic acid involved. The implications of the type of acid and the specific element that can be mobilised become increasingly significant where LMMOA concentrations are highest, such as in rhizosphere soil.

Rhizosphere priming effects on soil carbon and nitrogen dynamics among tree species with and without intraspecific competition.

PubMed

Yin, Liming; Dijkstra, Feike A; Wang, Peng; Zhu, Biao; Cheng, Weixin

2018-05-01

Rhizosphere priming effects (RPEs) play a central role in modifying soil organic matter mineralization. However, effects of tree species and intraspecific competition on RPEs are poorly understood. We investigated RPEs of three tree species (larch, ash and Chinese fir) and the impact of intraspecific competition of these species on the RPE by growing them at two planting densities for 140 d. We determined the RPE on soil organic carbon (C) decomposition, gross and net nitrogen (N) mineralization and net plant N acquisition. Differences in the RPE among species were associated with differences in plant biomass. Gross N mineralization and net plant N acquisition increased, but net N mineralization decreased, as the RPE on soil organic C decomposition increased. Intraspecific competition reduced the RPE on soil organic C decomposition, gross and net N mineralization, and net plant N acquisition, especially for ash and Chinese fir. Microbial N mining may explain the overall positive RPEs across species, whereas intensified plant-microbe competition for N may have reduced the RPE with intraspecific competition. Overall, the species-specific effects of tree species play an important role in modulating the magnitude and mechanisms of RPEs and the intraspecific competition on soil C and N dynamics. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Biochar, activated carbon, and carbon nanotubes have different effects on fate of (14)C-catechol and microbial community in soil.

PubMed

Shan, Jun; Ji, Rong; Yu, Yongjie; Xie, Zubin; Yan, Xiaoyuan

2015-10-30

This study investigated the effects of biochar, activated carbon (AC)-, and single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) in various concentrations (0, 0.2, 20, and 2,000 mg/kg dry soil) on the fate of (14)C-catechol and microbial community in soil. The results showed that biochar had no effect on the mineralization of (14)C-catechol, whereas AC at all amendment rates and SWCNTs at 2,000 mg/kg significantly reduced mineralization. Particularly, MWCNTs at 0.2 mg/kg significantly stimulated mineralization compared with the control soil. The inhibitory effects of AC and SWCNTs on the mineralization were attributed to the inhibited soil microbial activities and the shifts in microbial communities, as suggested by the reduced microbial biomass C and the separated phylogenetic distance. In contrast, the stimulatory effects of MWCNTs on the mineralization were attributed to the selective stimulation of specific catechol-degraders by MWCNTs at 0.2 mg/kg. Only MWCNTs amendments and AC at 2,000 mg/kg significantly changed the distribution of (14)C residues within the fractions of humic substances. Our findings suggest biochar, AC, SWCNTs and MWCNTs have different effects on the fate of (14)C-catechol and microbial community in soil.

Biochar, activated carbon, and carbon nanotubes have different effects on fate of 14C-catechol and microbial community in soil

PubMed Central

Shan, Jun; Ji, Rong; Yu, Yongjie; Xie, Zubin; Yan, Xiaoyuan

2015-01-01

This study investigated the effects of biochar, activated carbon (AC)-, and single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) in various concentrations (0, 0.2, 20, and 2,000 mg/kg dry soil) on the fate of 14C-catechol and microbial community in soil. The results showed that biochar had no effect on the mineralization of 14C-catechol, whereas AC at all amendment rates and SWCNTs at 2,000 mg/kg significantly reduced mineralization. Particularly, MWCNTs at 0.2 mg/kg significantly stimulated mineralization compared with the control soil. The inhibitory effects of AC and SWCNTs on the mineralization were attributed to the inhibited soil microbial activities and the shifts in microbial communities, as suggested by the reduced microbial biomass C and the separated phylogenetic distance. In contrast, the stimulatory effects of MWCNTs on the mineralization were attributed to the selective stimulation of specific catechol-degraders by MWCNTs at 0.2 mg/kg. Only MWCNTs amendments and AC at 2,000 mg/kg significantly changed the distribution of 14C residues within the fractions of humic substances. Our findings suggest biochar, AC, SWCNTs and MWCNTs have different effects on the fate of 14C-catechol and microbial community in soil. PMID:26515132

The nanophase iron mineral(s) in Mars soil

NASA Technical Reports Server (NTRS)

Banin, A.; Ben-Shlomo, T.; Margulies, L.; Blake, D. F.; Gehring, A. U.

1992-01-01

Iron-enriched smectites have been suggested as important mineral compounds of the Martian soil. They were shown to comply with the chemical analysis of the Martian soil, to simulate many of the findings of the Viking Labeled Release Experiments on Mars, to have spectral reflectance in the VIS-NIR strongly resembling the bright regions on Mars. The analogy with Mars soil is based, in a number of aspects, on the nature and behavior of the iron oxides and oxyhydroxides deposited on the surface of the clay particles. A summary of the properties of these iron phases and some recent findings are presented. Their potential relevance to Mars surface processes is discussed.

Microbial processes dominate P fluxes in a low-phosphorus temperate forest soil: insights provided by 33P and 18O in phosphate

NASA Astrophysics Data System (ADS)

Pistocchi, Chiara; Tamburini, Federica; Bünemann, Else; Mészáros, Éva; Frossard, Emmanuel

2016-04-01

The classical view of the P cycle in forests is that trees and mycorrhizal fungi associated with them take up most of their phosphorus as phosphate (P) from the soil solution. The soil solution is then replenished by the release of P from sorbed phases, by the dissolution of P containing minerals or by biological mineralization and/or enzymatic hydrolysis of organic P compounds. Direct insight into the processes phosphate goes through at the ecosystem level is, however, missing. Assessing the relevance of inorganic and biological processes controlling P cycling requires the use of appropriate approaches and tracers. Within the German Priority Program "Ecosystem Nutrition: Forest Strategies for limited Phosphorus Resources" we studied P forms and dynamics in organic horizons (Of/Oh) of temperate beech forest soils in Germany with contrasting soil P availability (P-poor and P-rich). We followed the fate of P from the litter into the soil pools, using isotopes as tracers (stable oxygen isotopes in water and phosphate and 33P) and relied on measurements in experimental forest sites and a three-months incubation experiment with litter addition. Using an isotopic dilution approach we were able to estimate gross (7 mg P kg-1 d-1 over the first month) and net mineralization rates (about 5 mg P kg-1 d-1 over the first 10 days) in the P-poor soil. In this soil the immobilization of P in the microbial biomass ranged from 20 to 40% of gross mineralization during the incubation, meaning that a considerable part of mineralized P contributed to replenish the available P pool. In the P-rich soil, physicochemical processes dominated exchangeable P to the point that the contribution of biological/biochemical processes was non-detectable. Oxygen isotopes in phosphate elucidated that organic P mineralization by enzymatic hydrolysis gains more importance with decreasing P availability, both under controlled and under field conditions. In summary, microbial processes dominated P fluxes (70 to 80%) in the P-poor soil, while in the P-rich soil microbial processes could not be detected because of the higher baseline of physicochemical processes. Our results support the hypothesis that organic P has a faster turnover under conditions of low P availability and that net mineralization is the most relevant process providing available P for plants under these conditions.

The effects of organic matter-mineral interactions and organic matter chemistry on diuron sorption across a diverse range of soils.

PubMed

Smernik, Ronald J; Kookana, Rai S

2015-01-01

Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC), because it is assumed that the main factor that influences the amount sorbed is the organic carbon content of the soil. However, KOC can vary by a factor of at least ten across a range of soils. We investigated two potential causes of variation in diuron KOC - organic matter-mineral interactions and organic matter chemistry - for a diverse set of 34 soils from Sri Lanka, representing a wide range of soil types. Treatment with hydrofluoric acid (HF-treatment) was used to concentrate soil organic matter. HF-treatment increased KOC for the majority of soils (average factor 2.4). We attribute this increase to the blocking of organic matter sorption sites in the whole soils by minerals. There was no significant correlation between KOC for the whole soils and KOC for the HF-treated soils, indicating that the importance of organic matter-mineral interactions varied greatly amongst these soils. There was as much variation in KOC across the HF-treated soils as there was across the whole soils, indicating that the nature of soil organic matter is also an important contributor to KOC variability. Organic matter chemistry, determined by solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, was correlated with KOC for the HF-treated soils. In particular, KOC increased with the aromatic C content (R=0.64, p=1×10(-6)), and decreased with O-alkyl C (R=-0.32, p=0.03) and alkyl C (R=-0.41, p=0.004) content. Copyright © 2014 Elsevier Ltd. All rights reserved.

Microbial weathering of apatite and wollastonite in a forest soil: Evidence from minerals buried in a root-free zone

NASA Astrophysics Data System (ADS)

Nezat, C. A.

2011-12-01

Mineral weathering is an important process in biogeochemical cycling because it releases nutrients from less labile pools (e.g., rocks) to the food chain. A field experiment was undertaken to determine the degree to which microbes - both fungi and bacteria - are responsible for weathering of Ca-bearing minerals. The experiment was performed at the Hubbard Brook Experimental Forest (HBEF) in the northeastern USA, where acid deposition has leached plant-available calcium from soils for decades. Trees obtain soil nutrients through root uptake as well as through mycorrhizal fungi with which they are symbiotically associated. These fungi extend their hyphae from the tree roots into the soil and exude organic acids that may enhance mineral dissolution. The two most common types of symbiotic fungal-tree associations are ectomycorrhizae, which are associated with spruce (Picea), fir (Abies), and beech (Fagus); and arbuscular mycorrhizae which are commonly associated with angiosperms, such as maples (Acer). To examine the role of fungi and bacteria in weathering of Ca- and/or P-bearing minerals, mesh bags containing sand-sized grains of quartz (as a control), quartz plus 1% wollastonite (CaSiO3), or quartz plus 1% apatite (Ca5(PO4)3F) were buried ~15 cm deep in mineral soil beneath American beech, sugar maple, and mixed spruce and balsam fir stands at the HBEF. Half of the bags were constructed of 50-μm mesh to exclude roots but allow fungal hyphae and bacteria to enter the bags; the remaining bags had 1-μm mesh to exclude fungi and roots but allow bacteria to enter. The bags were retrieved ~ 1, 2 or 4 years after burial. Microbial community composition and biomass in the mesh bags and surrounding soil were characterized and quantified using phospholipid fatty acid (PLFA) analysis. Fungal biomass in the soil and control bags did not differ significantly among stand types. In contrast, the degree of fungal colonization in apatite- and wollastonite-amended bags varied significantly, suggesting that microbial response was due to tree species, type of mycorrhizal fungi, nutrient status of the soils, and mineral composition of the mesh bags. Mineral surfaces were examined using scanning electron microscopy (SEM) to investigate the degree of mineral dissolution as a function of stand type, microbial composition, and time.

Biologically-Mediated Weathering of Minerals From Nanometre Scale to Environmental Systems

NASA Astrophysics Data System (ADS)

Brown, D. J.; Banwart, S. A.; Smits, M. M.; Leake, J. R.; Bonneville, S.; Benning, L. G.; Haward, S. J.; Ragnarsdottir, K.

2007-12-01

The Weathering Science Consortium is a multi-disciplinary project that aims to create a step change in understanding how biota control mineral weathering and soil formation (http://www.wun.ac.uk/wsc). Our hypothesis is that rates of biotic weathering are driven by the energy supply from plants to the organisms, controlling their biomass, surface area of contact with minerals and their capacity to interact chemically with minerals. Symbiotic fungal mycorrhiza of 90% of plant species are empowered with an available carbohydrate supply from plants that is unparalleled amongst soil microbes. They develop extensive mycelial networks that intimately contact minerals, which they weather aggressively. We hypothesise that mycorrhiza play a critical role through their focussing of photosynthate energy from plants into sub-surface weathering environments. Our work identifies how these fungal cells, and their secretions, interact with mineral surfaces and affect the rates of nutrient transfer from minerals to the organism. Investigating these living systems allows us to create new concepts and mathematical models that can describe biological weathering and be used in computer simulations of soil weathering dynamics. We are studying these biochemical interactions at 3 levels of observation: 1. At the molecular scale to understand interactions between living cells and minerals and to quantify the chemistry that breaks down the mineral structure; 2. At the soil grain scale to quantify the activity and spatial distribution of the fungi, roots and other organisms (e.g. bacteria) and their effects on the rates at which minerals are dissolved to release nutrients; 3. At soil profile scale to test models for the spatial distribution of active fungi and carbon energy and their seasonal variability and impact on mineral dissolution rates. Here we present early results from molecular and soil grain scale experiments. We have grown pure culture (Suillus bovinus, Paxillus involutus) mycorrhizal mycelial networks associated with pine trees in otherwise sterile (agar) and also non-sterile (peat) microcosms, which include mineral sections and powders of biotite, apatite and quartz. 14C labelling has been used to map C flux through the microcosms and to determine the transfer of photosynthate energy into the weathering arenas. We have used Vertical Scanning Interferometry (VSI) to assess volumetric alteration of mineral substrates in contact with fungi. Focused Ion Beam (FIB)- Transmission Electron Microscope (TEM) work provides evidence for increased mechanical forcing and possible alteration of biotite surfaces with greater fungi contact time. We also present real-time in situ observations of mineral-organic acid and mineral-exudate interactions using Atomic Force Microscopy (AFM).

A Simulation of the Interaction of Acid Rain with Soil Minerals

ERIC Educational Resources Information Center

Schilling, Amber L.; Hess, Kenneth R.; Leber, Phyllis A.; Yoder, Claude H.

2004-01-01

The atmospheric issue of acid rains is subjected to a five-part laboratory experiment by concentrating on the chemistry of the infiltration process of acid rainwater through soils. This procedure of quantitative scrutiny helps students realize the efficacy of soil minerals in the consumption of surplus acidity in rainwater.

A rapid and cost effective method for soil carbon mineralization under static incubations

USDA-ARS?s Scientific Manuscript database

Soil incubations with subsequent measurement of carbon dioxide (CO2) evolved are common soil assays to estimate C mineralization rates and active organic C. Two common methods used to detect CO2 in laboratory incubations are gas chromatography (GC) and alkali absorption followed by titration (NaOH)...

Phytoremediation and phytomining: Using plants to remediate contaminated or mineralized environments

USDA-ARS?s Scientific Manuscript database

One type of harsh environment for plants is metal and metalloid contaminated or mineralized soils which exist in most countries due to geological formations or to the history of mining and smelting. Depending on soil pH and fertility, metal-rich soils may be barren and eroding into wider areas. Some...

Effects of rooting and tree growth of selected woodland species on cap integrity in a mineral capped landfill site.

PubMed

Hutchings, T R; Moffat, A J; Kemp, R A

2001-06-01

The above and below ground growth of three tree species (Alnus glutinosa, Pinus nigra var. maritima and Acer pseudoplatanus) was studied on a containment landfill site at Waterford, Hertfordshire, UK. Tree root architecture was studied using soil inspection pits excavated next to 12 trees of each species and mapped in detail. Tree height was related to soil thickness over the compacted mineral cap. No roots entered the cap where soil thickness was 1.3 m, but a few roots, especially of alder, were observed within it when the soil cover was 1.0 m or less. Micromorphological analysis of undisturbed samples of the mineral cap suggested that roots exploited weaknesses in the cap rather than actively causing penetration into it. Alder roots were more tolerant of anaerobic conditions within the cap than the other species examined. The results confirm that mineral caps should be covered by 1.5 m of soil or soil-forming material if tree establishment is intended over a restored landfill site, unless protected by other parts of a composite capping system.

Influence of iron redox cycling on organo-mineral associations in arctic tundra soils

NASA Astrophysics Data System (ADS)

Herndon, E.; AlBashaireh, A.; Duroe, K.; Singer, D. M.

2016-12-01

Geochemical interactions between soil organic matter and minerals influence decomposition in many environments but remain poorly understood in arctic tundra systems. In tundra soils that are periodically to persistently saturated, the accumulation of iron oxyhydroxides and organo-iron precipitates at redox interfaces may inhibit decomposition by binding organic molecules and protecting them from microbial degradation. Here, we couple synchrotron-source spectroscopic techniques with chemical sequential extractions and physical density fractionations to evaluate the spatial distribution and speciation of Fe-bearing phases and associated organic matter in organic and mineral horizons of the seasonally thawed active layer in tundra soils from northern Alaska. Mineral-associated organic matter comprised 63 ± 9% of soil organic carbon stored in the active layer of ice wedge polygons. Ferrous iron produced in anoxic mineral horizons diffused upwards and precipitated as poorly-crystalline oxyhydroxides and organic-bound Fe(III) in the organic horizons. Ferrihydrite and goethite were present as coatings on mineral grains and plant debris and in aggregates with clays and particulate organic matter. Organic matter released through acid-dissolution of iron oxides may represent a small pool of readily-degradable organic molecules temporarily stabilized by sorption to iron oxyhydroxide surfaces, while larger quantities of particulate organic carbon and humic-like substances may be physically protected from decomposition by Fe-oxide coatings and aggregation. We conclude that formation of poorly-crystalline and crystalline iron oxides at redox interfaces contributes to mineral protection of organic matter through sorption, aggregation, and co-precipitation reactions. Further study of organo-mineral associations is necessary to determine the net impact of mineral-stabilization on carbon storage in rapidly warming arctic ecosystems.

Lead (II) removal from natural soils by enhanced electrokinetic remediation.

PubMed

Altin, Ahmet; Degirmenci, Mustafa

2005-01-20

Electrokinetic remediation is a very effective method to remove metal from fine-grained soils having low adsorption and buffering capacity. However, remediation of soil having high alkali and adsorption capacity via the electrokinetic method is a very difficult process. Therefore, enhancement techniques are required for use in these soil types. In this study, the effect of the presence of minerals having high alkali and cation exchange capacity in natural soil polluted with lead (II) was investigated by means of the efficiency of electrokinetic remediation method. Natural soil samples containing clinoptilolite, gypsum and calcite minerals were used in experimental studies. Moreover, a sample containing kaolinite minerals was studied to compare with the results obtained from other samples. Best results for soils bearing alkali and high sorption capacity minerals were obtained upon addition of 3 mol AcH and application of 20 V constant potential after a remediation period of 220 h. In these test conditions, lead (II) removal efficiencies for these samples varied between 60% and 70% up to 0.55 normalized distance. Under the same conditions, removal efficiencies in kaolinite sample varied between 50% and 95% up to 0.9 normalized distance.

Clay minerals and metal oxides strongly influence the structure of alkane-degrading microbial communities during soil maturation.

PubMed

Steinbach, Annelie; Schulz, Stefanie; Giebler, Julia; Schulz, Stephan; Pronk, Geertje J; Kögel-Knabner, Ingrid; Harms, Hauke; Wick, Lukas Y; Schloter, Michael

2015-07-01

Clay minerals, charcoal and metal oxides are essential parts of the soil matrix and strongly influence the formation of biogeochemical interfaces in soil. We investigated the role of these parental materials for the development of functional microbial guilds using the example of alkane-degrading bacteria harbouring the alkane monooxygenase gene (alkB) in artificial mixtures composed of different minerals and charcoal, sterile manure and a microbial inoculum extracted from an agricultural soil. We followed changes in abundance and community structure of alkane-degrading microbial communities after 3 and 12 months of soil maturation and in response to a subsequent 2-week plant litter addition. During maturation we observed an overall increasing divergence in community composition. The impact of metal oxides on alkane-degrading community structure increased during soil maturation, whereas the charcoal impact decreased from 3 to 12 months. Among the clay minerals illite influenced the community structure of alkB-harbouring bacteria significantly, but not montmorillonite. The litter application induced strong community shifts in soils, maturated for 12 months, towards functional guilds typical for younger maturation stages pointing to a resilience of the alkane-degradation function potentially fostered by an extant 'seed bank'.

Clay minerals and metal oxides strongly influence the structure of alkane-degrading microbial communities during soil maturation

PubMed Central

Steinbach, Annelie; Schulz, Stefanie; Giebler, Julia; Schulz, Stephan; Pronk, Geertje J; Kögel-Knabner, Ingrid; Harms, Hauke; Wick, Lukas Y; Schloter, Michael

2015-01-01

Clay minerals, charcoal and metal oxides are essential parts of the soil matrix and strongly influence the formation of biogeochemical interfaces in soil. We investigated the role of these parental materials for the development of functional microbial guilds using the example of alkane-degrading bacteria harbouring the alkane monooxygenase gene (alkB) in artificial mixtures composed of different minerals and charcoal, sterile manure and a microbial inoculum extracted from an agricultural soil. We followed changes in abundance and community structure of alkane-degrading microbial communities after 3 and 12 months of soil maturation and in response to a subsequent 2-week plant litter addition. During maturation we observed an overall increasing divergence in community composition. The impact of metal oxides on alkane-degrading community structure increased during soil maturation, whereas the charcoal impact decreased from 3 to 12 months. Among the clay minerals illite influenced the community structure of alkB-harbouring bacteria significantly, but not montmorillonite. The litter application induced strong community shifts in soils, maturated for 12 months, towards functional guilds typical for younger maturation stages pointing to a resilience of the alkane-degradation function potentially fostered by an extant ‘seed bank'. PMID:25535940

The Fate and Stability of Eroding Wetland Soil Carbon in a Subsiding Deltaic Coastal Plain

NASA Astrophysics Data System (ADS)

White, J. R.; Steinmuller, H.; Chambers, L. G.; Fontenot, A.

2017-12-01

Coastal wetlands can respond to rapid rates of relative sea level rise via wetland submergence and/or erosion, which occur when wetlands are unable to vertically accrete to keep pace with sea level rise. As coastal wetlands erode, previously sequestered organic carbon is exposed to oxygen-rich estuarine water. This transition in redox from anaerobic to aerobic condition can trigger increased mineralization rates of decades to centuries'-old soil carbon. Barataria Bay, Louisiana has one of the highest coastal wetland land loss rates in the United States, primarily due to eustatic sea level rise coupled with coastal subsidence. Marsh-edge erosion rates measured over the past two years are on the order of 1.5 meters per year. Meter long soil cores were obtained from vegetated wetland sites and sectioned into 11 intervals to investigate aerobic and anaerobic mineralization rates with depth. In surface soils, organic carbon mineralization rates averaged 16 times greater than anaerobic mineralization rates. In deeper, older soils, the aerobic mineralization rate was still an order of magnitude greater than the anaerobic rate, suggesting a significant portion of this older, soil carbon is readily cycling back to the atmosphere after erosion followed by mineralization by microorganisms. These results have consequences for increased atmospheric CO2 concentrations in the future, as stable coastlines worldwide will be subjected to Barataria-bay levels of sea level rise in the next 50-75 years.

Raman Spectroscopy for Mineral Identification and Quantification for in situ Planetary Surface Analysis: A Point Count Method

NASA Technical Reports Server (NTRS)

Haskin, Larry A.; Wang, Alian; Rockow, Kaylynn M.; Jolliff, Bradley L.; Korotev, Randy L.; Viskupic, Karen M.

1997-01-01

Quantification of mineral proportions in rocks and soils by Raman spectroscopy on a planetary surface is best done by taking many narrow-beam spectra from different locations on the rock or soil, with each spectrum yielding peaks from only one or two minerals. The proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks, in analogy with the standard petrographic technique of point counting. The method can also be used for nondestructive laboratory characterization of rock samples. Although Raman peaks for different minerals seldom overlap each other, it is impractical to obtain proportions of constituent minerals by Raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad-beam sensing of a representative area of the target material. That is because the Raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the Raman scattering cross section of that mineral to its proportion in the rock, and the signal-to-noise ratio of a Raman spectrum is poor when a sample is stimulated by a low-power laser beam of broad diameter. Results obtained by the Raman point-count method are demonstrated for a lunar thin section (14161,7062) and a rock fragment (15273,7039). Major minerals (plagioclase and pyroxene), minor minerals (cristobalite and K-feldspar), and accessory minerals (whitlockite, apatite, and baddeleyite) were easily identified. Identification of the rock types, KREEP basalt or melt rock, from the 100-location spectra was straightforward.

The CO2 emission in urbanic soils in the conditions of intensive technogenic pollution

NASA Astrophysics Data System (ADS)

Deviatova, Tatiana; Alaeva, Liliia; Negrobova, Elena; Kramareva, Tatiana

2017-04-01

Massive industrial pollution of the environment including soils leads to drastic changes in the vital activity of microorganisms, plants and animals. As objects of research was selected soils of the industrial and residential zones, farmland soils, forest soils. Comparative analysis showed that the emission of CO2 urbanizable increase compared to the suburban soils in recreational areas is 1.5 times, in the residential and industrial zones - in 3-5 times. In addition, identified a local point located in the vicinity of chemical plants, where soil CO2 emission increased up to 40 times compared to the suburban soils. Air technogenic pollution of soils by industrial emissions and transport enhances the mineralization of soil organic matter, increases its lability. These trends are associated with nonspecific adaptive reactions of the soil microbial complex in terms of pollution. Strengthening of the processes of mineralization may be due to the increase in the proportion of fungi in the microbial community. According to numerous reports they are more resistant to pollution compared to bacteria and actinomycetes. Admission to the soil organic matter of anthropogenic origin also increases the process of mineralization. According to the findings, low concentrations of petroleum products lead to increased "breathing" of the soil. Strengthening of the processes of mineralization and, consequently, of CO2 emissions, in the conditions of technogenic pollution of the soils identified in our studies, confirmed by numerous studies by other authors. According to reports in Russia the emission of CO2 from soils is 4.5 times higher than the industrial receipt of its atmosphere. The contribution of local anthropogenic CO2 emissions is not so significant compared to the indirect influence of soil pollution on increased CO2 emissions. Consequently, the expansion of technogenic contaminated soil is becoming a more significant factor adversely affecting the state of the atmosphere. Thus, the technogenic impact on the soil cover of the city greatly affects the emission of CO2 from the soil. Increasing in industrially polluted soils is associated with increased mineralization of organic matter and degradation of humus. You can put that in terms of pollution, increased carbon loss depends on changes in the metabolism of soil organisms.

Amelioration of nickel phytotoxicity in muck and mineral soils.

PubMed

Kukier, U; Chaney, R L

2001-01-01

In situ remediation (phytostabilization) is a cost-effective solution for restoring the productivity of metal-contaminated soils and protection of food chains. A pot experiment with wheat (Triticum aestivum L.), oat (Avena sativa L.), and redbeet (Beta vulgaris L.) was conducted to test the ability of limestone and hydrous ferric oxide (HFO) to ameliorate Ni phytotoxicity in two soils contaminated by particulate emissions from a nickel refinery. Quarry muck (Terric Haplohemist; 72% organic matter) contained 2210 mg kg(-1) of total Ni. The mineral soil, Welland silt loam (Typic Epiaquoll), was more contaminated (2930 mg Ni kg(-1)). Both soils were very strongly acidic, allowing the soil Ni to be soluble and phytotoxic. Nickel phytotoxicity of the untreated muck soil was not very pronounced and could be easily confused with symptoms of Mn deficiency that occurred in this soil even with Mn fertilization. Severe nickel phytotoxicity of the untreated mineral soil prevented any growth of redbeet, the most sensitive crop; even wheat, a relatively Ni-resistant species, was severely damaged. White banding indicative of Ni phytotoxicity was present on oat and wheat leaves grown on the acidic mineral soil. Soil Ni extracted with diethylenetriaminepentaacetic acid (DTPA) and 0.01 M Sr(NO3)2 was indicative of the ameliorative effect of amendments and correlated well with Ni concentrations in plant shoots. Making soils calcareous was an effective treatment to reduce plant-available Ni and remediate Ni phytotoxicity of these soils to all crops tested. The ameliorative effect of HFO was crop-specific and much less pronounced.

Thermal and chemical variations of the Nigerian Benue trough lead-zinc-barite-fluorite deposits

NASA Astrophysics Data System (ADS)

Ogundipe, Ibukun Emmanuel

2017-08-01

The Benue trough is an intra-continental rift initiated in the Cretaceous during the opening of the South Atlantic Ocean. Lead-zinc-barite-fluorite mineralization occurs along the 600 km axis of the trough in three discrete sub-basins which coincide with the lower, middle and upper mineral districts of the Benue Valley. Lithologically these sub-basins are dominated by black carbonaceous shale in the Lower Benue, platform carbonates in the Middle Benue and sandstones in the Upper Benue. Micro-thermometric analysis of fluid inclusions in sphalerite, fluorite, barite and quartz have shown that each mineral district has its own unique thermal and chemical imprint. For example, the temperature can be bracketed between 109 °C and 160 °C for lower Benue, 89 °C-144 °C for the Middle Benue and 176 °C-254 °C for the Upper Benue. Chemical differentiation also exists between each mineral district with the Lower Benue having 22 wt % equivalent NaCl while the Middle and Upper Benue have 18 and 16 wt % equivalent NaCl respectively. This study shows that inter-district thermal and chemical variations exist between the ore-stage sulfide and post-sulfide gangue minerals of the entire Benue Valley. Similarly, intra-district thermal and chemical variations have also been observed among all the paragenetic minerals of each district. The thermal variations may be as a result of variations in the geothermal gradient accompanying continental rifting from one district to the other. The variations in the chemistry between the Lower Benue and the Upper Benue paragenic minerals may be as a result of the distinct lithological differences across the Benue Trough.

Enhanced yields and soil quality in a wheat-maize rotation using buried straw mulch.

PubMed

Guo, Zhibin; Liu, Hui; Wan, Shuixia; Hua, Keke; Jiang, Chaoqiang; Wang, Daozhong; He, Chuanlong; Guo, Xisheng

2017-08-01

Straw return may improve soil quality and crop yields. In a 2-year field study, a straw return method (ditch-buried straw return, DB-SR) was used to investigate the soil quality and crop productivity effects on a wheat-corn rotation system. This study consisted of three treatments, each with three replicates: (1) mineral fertilisation alone (CK0); (2) mineral fertilisation + 7500 kg ha -1 wheat straw incorporated at depth of 0-15 cm (NPKWS); and (3) mineral fertilisation + 7500 kg ha -1 wheat straw ditch buried at 15-30 cm (NPKDW). NPKWS and NPKDW enhanced crop yield and improved soil biotical properties compared to mineral fertilisation alone. NPKDW contributed to greater crop yields and soil nutrient availability at 15-30 cm depths, compared to NPKWS treatment. NPKDW enhanced soil microbial activity and bacteria species richness and diversity in the 0-15 cm layer. NPKWS increased soil microbial biomass, bacteria species richness and diversity at 15-30 cm. The comparison of the CK0 and NPKWS treatments indicates that a straw ditch buried by digging to the depth of 15-30 cm can improve crop yields and soil quality in a wheat-maize rotation system. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

MINERALIZATION OF A SORBED POLYCYCLIC AROMATIC HYDROCARBON IN TWO SOILS USING CATALYZED HYDROGEN PEROXIDE. (R826163)

EPA Science Inventory

Hydrogen peroxide (H₂O₂) catalyzed by soluble iron or naturally occurring soil minerals, (i.e., modified Fenton's reagent) was investigated as a basis for mineralizing sorbed and NAPL-phase benzo[a]pyrene (BaP), a hydrophobic and toxic polycyclic a...

Soil respiration and net N mineralization along a climate gradient in Maine

Treesearch

Jeffery A. Simmons; Ivan J. Fernandez; Russell D. Briggs

1996-01-01

Our objective was to determine the influence of temperature and moisture on soil respiration and net N mineralization in northeastern forests. The study consisted of sixteen deciduous stands located along a regional climate gradient within Maine. A significant portion of the variance in net N mineralization (41 percent) and respiration (33 percent) was predicted by...

Iron Redox Cycling Drives Decomposition of Mineral-Associated C in Humid Tropical Forest Soils

NASA Astrophysics Data System (ADS)

Hall, S. J.; Mcnicol, G.; Silver, W. L.

2013-12-01

The stabilization of soil carbon (C) by reactive minerals and an inhibition of decomposition due to oxygen (O2) limitation (reducing conditions) have been proposed as drivers of the high soil C concentrations characteristic of humid tropical forests, which constitute a major terrestrial C reservoir. Here, we examined relationships between these factors and spatial patterns of C concentrations and C turnover (using radiocarbon modeling) in surface soils of the Luquillo Experimental Forest, Puerto Rico. We used concentrations of reduced iron (Fe(II)) as an index of reducing conditions given the importance of Fe reduction to anaerobic metabolism in these soils. Concentrations of Fe(II), reactive iron and aluminum (Al) minerals, interactions between Fe(II) and Al, and live fine root biomass explained most variation in C concentrations across the landscape (pseudo R2 = 0.84). Carbon increased with chelatable "poorly crystalline" Fe, in agreement with previous research, but C decreased with citrate/ascorbate extractable Fe, an index of Fe oxides susceptible to microbial reduction. We suggest that availability of Fe oxides to sustain anaerobic respiration partially offsets soil C accumulation in these ecosystems, despite the role of a subset of reactive Fe in promoting C stabilization. We estimated decomposition rates of mineral-associated C using 14C content of the heavy soil density fraction from a subset of samples. Turnover times averaged 108 years but decreased with Fe(II) concentrations. Thus, our data suggest that Fe redox cycling in soil microsites is associated with increased turnover of mineral-associated C in this fluctuating-oxygen environment, implying that the capacity of reactive metals to stabilize C may be partially contingent on O2 dynamics. Our results suggest a multifaceted role for reactive minerals in soil C cycling, emphasizing the importance of ecosystem-scale interactions among geochemical, physical, and biological factors.

Pedogenic Magnetic Minerals in Soils: Some Tests of Current Models

NASA Astrophysics Data System (ADS)

Egli, R.

2008-12-01

The magnetic enhancement of soils is increasingly used as a proxy for continental climate, since it is related to the formation of pedogenic iron minerals under warm, humid conditions. Ultrafine magnetite is believed to be the major responsible of the magnetic enhancement, however, very little is known on the detailed formation mechanism, ant its relation to the soil iron cycle. Furthermore, the 'textbook' case of the Chinese Loess Plateau is not well replicated around the World: Loessic soils from the Midwestern US are systematically less enhanced than their Chinese counterpart under similar climatic conditions, and many loessic soils in Argentina are not enhanced at all. In trying to find a rationale behind these differences, I will address three main questions that need to be answered in a bottom-up approach to the problem. The first question is whether susceptibility is indeed controlled by fine magnetite, excluding any significant role of other minerals such as ferrihydrite, goethite, and hematite. This is a rock magnetic problem addressing the interpretation of magnetic measurements: is susceptibility an adequate proxy for the concentration of magnetic minerals in soils? Answering this question allows us to think directly in terms of abundance specific magnetic minerals, which is fundamental for any subsequent interpretation. The second question is directed to understanding the role of magnetic minerals in the soil iron cycle and how they are formed. This brings us to a discussion of the transfer function linking magnetic enhancement with climate. Is indeed rainfall the only parameter controlling pedogenesis? Why is rainfall apparently related with the logarithm of susceptibility in enhanced soils? Can we test current pedogenetic models against this empirical transfer function? The third question points to the role of parent material and later dust inputs. Midwestern US and Argentinian loesses are different from Chinese loess. Is this a reason for the differences observed in the magnetic enhancement of the respective soils? Enough material is now available to test current models and hypotheses with respect to the first two questions.

Improvement of nitrogen utilization and soil properties by addition of a mineral soil conditioner: mechanism and performance.

PubMed

Yan, Xiaodan; Shi, Lin; Cai, Rumeng

2018-01-01

A mineral soil conditioner (MSC) composed of activated potash feldspar, gypsum, and calcium carbonate and containing an amount of available mineral nutrients, is shown to be effective for plant growth and acidic soil amelioration. In this study, a field test was conducted over four rice seasons by examining treatment with control check (CK), MSC, biological active carbon, and lime to investigate the nitrogen-use efficiency and mechanism of soil characteristic variations due to the desilicification and allitization of soil as well as the unrestrained use of nitrogen (N) fertilizer in recent years. Influences of MSC on the xylem sap intensity and mean rice yields were evaluated, and the soil type was also analyzed using the FactSage 6.1 Reaction, phase diagram, and Equilib modules. The results of the field trial showed that MSC application increased the xylem sap intensity and nitrogen export intensity by 37.33-39.85% and 31.40-51.20%, respectively. A significant increase (5.63-15.48%) in mean grain yields was achieved with MSC application over that with biological active carbon and lime application. The effects of MSC had a tendency to increase with time in the field experiment results, and grain yields increased after the initial application. The new formation of clay minerals exhibits a significant influence on [Formula: see text] fixation, especially for 2:1 phyllosilicates with illite, owing to the interlayers of the clay minerals. Our preliminary results showed that kaolinite, the main 1:1 phyllosilicate clay mineral in ferralsol, transformed to illite at room temperature as a consequence of the presence of H 4 SiO 4 and available K + supplied by MSC. This indicated that improving the soil quality combined with reducing N losses from soils is an efficient way to control non-point source pollution from agriculture without the risk of decreased in grain yield.

Response of soil organic carbon mineralization in typical Karst soils following the addition of 14C-labeled rice straw and CaCO3.

PubMed

Hu, Lening; Su, Yirong; He, Xunyang; Wu, Jinshui; Zheng, Hua; Li, Yang; Wang, Aihua

2012-03-30

Organic substrates and calcium are important factors controlling organic matter turnover in Karst soils. To understand their effects on soil organic carbon (SOC) mineralization, an incubation experiment was conducted involving a control treatment (CK), the addition of a (14)C-labeled rice straw (T1), CaCO(3) (T2), and both (14)C-labeled rice straw and CaCO(3) (T3) to two types of Karst soils (terra fusca and rendzina) and a red soil from southwestern China. Cumulative mineralization of the rice straw over 100 days in rendzina (22.96 mg kg(-1)) and terra fusca (23.19 mg kg(-1)) was higher than in the red soil (15.48 mg kg(-1); P < 0.05). Cumulative mineralization of native SOC decreased following addition of (14)C-labeled rice straw in the rendzina and terra fusca but increased in the red soil (negative and positive priming effects on native SOC). The turnover times of (14)C-labeled microbial biomass C (MBC) in the red soil, terra fusca and rendzina were 71 ± 2, 243 ± 20 and 254 ± 45 days, respectively. By adding CaCO(3), the accumulation of SOC was greater in the Karst soils than in the red soil. Although the interactions between rice straw decomposition and priming effects on native SOC are not yet understood, there was considerable variation between Karst and red soils. Soil calcium was a positive factor in maintaining SOC stability. MBC from rice straws was stable in terra fusca and rendzina, whereas it was active in the red soil. The Karst soils (terra fusca and rendzina) used in this study benefited SOC accumulation. Copyright © 2011 Society of Chemical Industry.

Soil carbon and nitrogen pools in mid- to late-successional forest stands of the northwestern United States: Potential impact of fire

Treesearch

Deborah S. Page-Dumroese; Martin F. Jurgensen

2006-01-01

When sampling woody residue (WR) and organic matter (OM) present in forest floor, soil wood, and surface mineral soil (0­30 cm) in 14 mid- to late-successional stands across a wide variety of soil types and climatic regimes in the northwestern USA, we found that 44%-84% of carbon (C) was in WR and surface OM, whereas >80% of nitrogen (N) was in the mineral soil. In...

Metal dispersion and mobility in soils from the Lik Zn-Pb-Ag massive sulphide deposit, NW Alaska: Environmental and exploration implications

USGS Publications Warehouse

Kelley, K.D.; Kelley, D.L.

2003-01-01

The Lik deposit in northern Alaska is a largely unexposed shale-hosted Zn-Pb-Ag massive sulphide deposit that is underlain by continuous permafrost. Residual soils overlying the mineralized zone have element enrichments that are two to six times greater than baseline values. The most prominent elements are Ag, Mo, P, Se, Sr, V by total 4-acid digestion and Tl by a weak partial digestion (Enzyme Leach or EL) because they show multi-point anomalies that extend across the entire mineralized zone, concentration ranges are 0.5-2.6 ppm Ag, 4-26 ppm Mo, 0.1-0.3% P, 3-22 ppm Se, 90-230 ppm Sr, 170-406 ppm V, and 1.6-30 ppb Tl. Lead, Sb, and Hg are also anomalous (up to 178 ppm, 30 ppm, and 1.9 ppm, respectively), but all are characterized by single point anomalies directly over the mineralized zone, with only slightly elevated concentrations over the lower mineralized section. Zinc (total) has a consistent baseline response of 200 ppm, but it is not elevated in soils overlying the mineralized zone. However, Zn by EL shows a distinct single-point anomaly over the ore zone that suggests it was highly mobile and partly adsorbed on oxides or other secondary phases during weathering. In situ analyses (by laser ablation ICP-MS) of pyrite and sphalerite from drill core suggest that sphalerite is the primary residence for Ag, Cd, and Hg in addition to Zn, and pyrite contains As, Fe, Sb, and Tl. The level and degree of oxidation, and the proportion of reacting pyrite and carbonate minerals are two factors that affected the mobility and transport of metals. In oxidizing conditions, Zn is highly mobile relative to Hg and Ag, perhaps explaining the decoupling of Zn from the other sphalerite-hosted elements in the soils. Soils are acidic (to 3.9 pH) directly over the deposit due to the presence of acid-producing pyrite, but acid-neutralizing carbonate away from the mineralized zone yield soils that are near neutral. The soils therefore formed in a complex system involving oxidation and weathering (mechanical and chemical) of sulphide minerals, dissolution of carbonate minerals, and precipitation of iron and manganese oxide minerals.

Soil solid-phase controls lead activity in soil solution.

PubMed

Badawy, S H; Helal, M I D; Chaudri, A M; Lawlor, K; McGrath, S P

2002-01-01

Lead pollution of the environment is synonymous with civilization. It has no known biological function, and is naturally present in soil, but its presence in food crops is deemed undesirable. The concern regarding Pb is mostly due to chronic human and animal health effects, rather then phytotoxicity. However, not much is known about the chemistry and speciation of Pb in soils. We determined the activity of Pb2+, in near neutral and alkaline soils, representative of alluvial, desertic and calcareous soils of Egypt, using the competitive chelation method. Lead activity ranged from 10(-6.73) to 10(-4.83) M, and was negatively correlated with soil and soil solution pH (R2 = -0.92, P < 0.01 and R2 = -0.89, P < 0.01, respectively). It could be predicted in soil solution from the equation: log(Pb2+) = 9.9 - 2pH. A solubility diagram for the various Pb minerals found in soil was constructed using published thermodynamic data obtained from the literature, and our measured Pb2+ activities compared with this information. The measured Pb2+ activities were undersaturated with regard to the solubility of PbSiO3 in equilibrium with SiO2 (soil). However, they were supersaturated with regard to the solubilities of the Pb carbonate minerals PbCO3 (cerussite) and Pb3(CO3)2(OH)2 in equilibrium with atmospheric CO2 and hydroxide Pb(OH)2. They were also supersaturated with regard to the solubilities of the Pb phosphate minerals Pb3(PO4)2, Pb5(PO4)3OH, and Pb4O(PO4)2 in equilibrium with tricalcium phosphate and CaCO3. The activity of Pb2+ was not regulated by any mineral of known solubility in our soils, but possibly by a mixture of Pb carbonate and phosphate minerals.

High Temperature and Salinity Enhance Soil Nitrogen Mineralization in a Tidal Freshwater Marsh

PubMed Central

Gao, Haifeng; Bai, Junhong; He, Xinhua; Zhao, Qingqing; Lu, Qiongqiong; Wang, Junjing

2014-01-01

Soil nitrogen (N) mineralization in wetlands is sensitive to various environmental factors. To compare the effects of salinity and temperature on N mineralization, wetland soils from a tidal freshwater marsh locating in the Yellow River Delta was incubated over a 48-d anaerobic incubation period under four salinity concentrations (0, 10, 20 and 35‰) and four temperature levels (10, 20, 30 and 40°C). The results suggested that accumulated ammonium nitrogen (NH4 +-N) increased with increasing incubation time under all salinity concentrations. Higher temperatures and salinities significantly enhanced soil N mineralization except for a short-term (≈10 days) inhibiting effect found under 35‰ salinity. The incubation time, temperature, salinity and their interactions exhibited significant effects on N mineralization (P<0.001) except the interactive effect of salinity and temperature (P>0.05), while temperature exhibited the greatest effect (P<0.001). Meanwhile, N mineralization processes were simulated using both an effective accumulated temperature model and a one-pool model. Both models fit well with the simulation of soil N mineralization process in the coastal freshwater wetlands under a range of 30 to 40°C (R2 = 0.88–0.99, P<0.01). Our results indicated that an enhanced NH4 +-N release with increasing temperature and salinity deriving from the projected global warming could have profound effects on nutrient cycling in coastal wetland ecosystems. PMID:24733366

Lateral weathering gradients in glaciated catchments

NASA Astrophysics Data System (ADS)

McGuire, K. J.; Bailey, S. W.; Ross, D. S.; Strahm, B. D.; Schreiber, M. E.

2016-12-01

Mineral dissolution and the distribution of weathering products are fundamental processes that drive development and habitability of the Earth's critical zone; yet, the spatial configuration of these processes in some systems is not well understood. Feedbacks between hydrologic flows and weathering fluxes are necessary to understanding how the critical zone develops. In upland glaciated catchments of the northeastern USA, primary mineral dissolution and the distribution of weathering products are spatially distinct and predictable over short distances. Hillslopes, where shallow soils force lateral hydrologic fluxes through accumulated organic matter, produce downslope gradients in mineral depletion, weathering product accumulation, soil development, and solute chemistry. We propose that linked gradients in hydrologic flow paths, soil depth, and vegetation lead to predictable differences in the location and extent of mineral dissolution in regolith (soil, subsoil, and rock fragments) and bedrock, and that headwater catchments within the upland glaciated northeast show a common architecture across hillslopes as a result. Examples of these patterns and processes will be illustrated using observations from the Hubbard Brook Experimental Forest in New Hampshire where laterally distinct soils with strong morphological and biogeochemical gradients have been documented. Patterns in mineral depletion and product accumulation are essential in predicting how ecosystems will respond to stresses, disturbance, and management.

Soil microbiological composition and its evolution along with forest succession in West Siberia

NASA Astrophysics Data System (ADS)

Naplekova, Nadezhda N.; Malakhova, Nataliya A.; Maksyutov, Shamil

2015-04-01

Natural forest succession process in West Siberia is mostly initiated by fire disturbance and involves changing tree species composition from pioneer species to late succession trees. Along with forest aging, litter and forest biomass accumulate. Changes of the soil nitrogen cycle between succession stages, important for plant functioning, have been reported in a number of studies. To help understanding the mechanism of the changes in the soil nitrogen cycle we analyzed soil microbiological composition for soil profiles (0-160 cm) taken at sites corresponding to three forest succession stages: (1) young pine, age 18-20 years, (2) mid age, dark coniferous, age 50-70 years, (3) mature, fir-spruce, age 170-180 years. Soil samples were taken from each soil horizon and analyzed in the laboratory for quantity and species composition of algae and other microorganisms. Algae community at all stages of succession is dominated by species typical for forest (pp. Chlorhormidium, Chlamydomonas, Chloroccocum, Pleurochloris, Stichococcus). Algae species composition is summarized by formulas: young forest C14X10Ch9H2P4Cf1B2amph4, mid age X16C15Ch10H4P4Cf1B2amph4, mature X24C22Ch17H10P2amph5Cf1, with designations C -- Cyanophyta, X -- Xantophyta, Ch -- Chlorophyta, B -- Bacillariophyta. Diversity is highest in upper two horizons and declines with depth. Microorganism composition on upper 20 cm was analyzed in three types of forests separately for consumers of protein (ammonifiers) and mineral nitrogen, fungi, azotobacter, Clostridium pasteurianum, oligonitrophylic (eg diazotrophs), nitrifiers and denitrifiers. Nitrogen biologic fixation in the mature forest soils is done mostly by oligonitrophyls and microorganisms of the genus Clostridium as well as сyanobacteria of sp. Nostoc, but the production rate appears low. Concentrations (count in gram soil) of nitrogen consumers (eg ammonifiers), oligonitrophyls, Clostridium and denitrifiers increase several fold from young forest to mid age, and from mid age to mature forest. On the contrary, azotobacter disappears in mature forest while nitrifiers decline by several times from young to mid age forest. Large variation in microbiological activity was observed between sites reaching different succession stage, however further studies are needed to discriminate between effects of the site productivity and forest age.

Nitrogen losses, uptake and abundance of ammonia oxidizers in soil under mineral and organo-mineral fertilization regimes.

PubMed

Florio, Alessandro; Felici, Barbara; Migliore, Melania; Dell'Abate, Maria Teresa; Benedetti, Anna

2016-05-01

A laboratory incubation experiment and greenhouse studies investigated the impact of organo-mineral (OM) fertilization as an alternative practice to conventional mineral (M) fertilization on nitrogen (N) uptake and losses in perennial ryegrass (Lolium perenne) as well as on soil microbial biomass and ammonia oxidizers. While no significant difference in plant productivity and ammonia emissions between treatments could be detected, an increase in soil total N content and an average 17.9% decrease in nitrates leached were observed in OM fertilization compared with M fertilization. The microbial community responded differentially to treatments, suggesting that the organic matter fraction of the OM fertilizer might have influenced N immobilization in the microbial biomass in the short-medium term. Furthermore, nitrate contents in fertilized soils were significantly related to bacterial but not archaeal amoA gene copies, whereas in non-fertilized soils a significant relationship between soil nitrates and archaeal but not bacterial amoA copies was found. The application of OM fertilizer to soil maintained sufficient productivity and in turn increased N use efficiency and noticeably reduced N losses. Furthermore, in this experiment, ammonia-oxidizing bacteria drove nitrification when an N source was added to the soil, whereas ammonia-oxidizing archaea were responsible for ammonia oxidation in non-fertilized soil. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Soil-plant-animal continuum in relation to macro and micro mineral status of dairy cattle in subtropical hill agro ecosystem.

PubMed

Kumaresan, A; Bujarbaruah, K M; Pathak, K A; Brajendra; Ramesh, T

2010-04-01

The purpose of the present study was to study the soil-plant-animal continuum in subtropical hilly areas. Soil (n = 96), fodder (n = 96), and blood serum samples from dairy cattle (n = 120) were collected from eight districts of Mizoram, a hilly state in India. The samples were digested using diacid mixture (HNO(3):HClO(4); 10:4) and analyzed for macro (Ca, P, Mg, Na, and K) and micro (Cu, Co, Mn, Fe, and Zn) mineral concentrations. The macro and micro mineral concentrations varied among the different districts. The correlation values between fodder and cattle were significant for all the minerals studied except for P and K. The correlation value between fodder and cattle was highly significant (P < 0.01) for Ca (0.878), Mg (0.88), Cu (0.885), and Zn (0.928). However, such correlations were not observed between the mineral levels in cattle and mineral levels in soil except for Ca (0.782). Equations developed in the present study for prediction of Ca (R(2) = 0.797), Mg (R(2) = 0.777), Zn (R(2) = 0.937), Fe (R(2) = 0.861), and Cu (R(2) = 0.794) had significant R(2) values. Further, it is inferred that dairy cattle reared under smallholder production system were deficient in most of the minerals and supplementation of required minerals is essential for optimum production.

Runoff sources and flowpaths in a partially burned, upland boreal catchment underlain by permafrost

USGS Publications Warehouse

Koch, Joshua C.; Kikuchi, Colin P.; Wickland, Kimberly P.; Schuster, Paul

2014-01-01

Boreal soils in permafrost regions contain vast quantities of frozen organic material that is released to terrestrial and aquatic environments via subsurface flowpaths as permafrost thaws. Longer flowpaths may allow chemical reduction of solutes, nutrients, and contaminants, with implications for greenhouse gas emissions and aqueous export. Predicting boreal catchment runoff is complicated by soil heterogeneities related to variability in active layer thickness, soil type, fire history, and preferential flow potential. By coupling measurements of permeability, infiltration potential, and water chemistry with a stream chemistry end member mixing model, we tested the hypothesis that organic soils and burned slopes are the primary sources of runoff, and that runoff from burned soils is greater due to increased hydraulic connectivity. Organic soils were more permeable than mineral soils, and 25% of infiltration moved laterally upon reaching the organic-mineral soil boundary on unburned hillslopes. A large portion of the remaining water infiltrated into deeper, less permeable soils. In contrast, burned hillslopes displayed poorly defined soil horizons, allowing rapid, mineral-rich runoff through preferential pathways at various depths. On the catchment scale, mineral/organic runoff ratios averaged 1.6 and were as high as 5.2 for an individual storm. Our results suggest that burned soils are the dominant source of water and solutes reaching the stream in summer, whereas unburned soils may provide longer term storage and residence times necessary for production of anaerobic compounds. These results are relevant to predicting how boreal catchment drainage networks and stream export will evolve given continued warming and altered fire regimes.

Moessbauer Spectroscopy for Lunar Resource Assessment: Measurement of Mineralogy and Soil Maturity

NASA Technical Reports Server (NTRS)

Morris, R. V.; Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Shen, M.-H.; Gibson, M. A.; Wills, E. L.

1992-01-01

First-order assessment of lunar soil as a resource includes measurement of its mineralogy and maturity. Soils in which the mineral ilmenite is present in high concentrations are desirable feedstock for the production of oxygen at a lunar base. The maturity of lunar soils is a measure of their relative residence time in the upper 1 mm of the lunar surface. Increasing maturity implies increasing load of solar wind species (e.g., N, H, and He-3), decreasing mean grain size, and increasing glass content. All these physicochemical properties that vary in a regular way with maturity are important parameters for assessing lunar soil as a resource. For example, He-3 can be extracted and potentially used for nuclear fusion. A commonly used index for lunar soil maturity is I(sub s)/FeO, which is the concentration of fine-grained metal determined by ferromagnetic resonance (I(sub s)) normalized to the total iron content (as FeO). I(sub s)/FeO has been measured for virtually every soil returned by the Apollo and Luna missions to the Moon. Because the technique is sensitive to both oxidation state and mineralogy, iron Moessbauer spectroscopy (FeMS) is a viable technique for in situ lunar resource assessment. Its utility for mineralogy is apparent from examination of published FeMS data for lunar samples. From the data published, it can be inferred that FeMS data can also be used to determine soil maturity. The use of FeMS to determine mineralogy and maturity and progress on development of a FeMS instrument for lunar surface use are discussed.

Volatilization of pesticides from the bare soil surface: evaluation of the humidity effect.

PubMed

Schneider, Martina; Endo, Satoshi; Goss, Kai-Uwe

2013-01-01

Volatilization of pesticides from soils under dry conditions (water content below the permanent wilting point) can be significantly influenced by sorption to hydrated mineral surfaces. This sorption process strongly depends on the water activity, expressed as equilibrium relative humidity in the pore space of the soil, and on the available surface area of the hydrated minerals. In this study, the influence of different humidity regimes on the volatilization of two pesticides (triallate and trifluralin) was demonstrated with a bench-scale wind tunnel system that allowed the establishment of well controlled humidity conditions within the soil. In the experiment starting with very dry conditions, increasing the relative humidity in the adjacent air from 60 to 85% resulted in an up to 8 times higher volatilization rate of the pesticides. An additional strong increase in volatilization (up to 3 times higher) was caused by a simulated rain event, which eliminates all sorption sites associated to mineral surfaces. In agreement with this interpretation, the comparison of two soils suggested that mineral surface area was the soil property that governs the volatilization under dry conditions, whereas soil organic matter was the controlling variable under wet conditions. In contrast to expectations, the use of a novel capsulated suspension for triallate showed the same humidity effects and no substantially lower volatilization rates in comparison to the regular formulation. This study demonstrated that humidity effects on pesticide volatilization can be interpreted via the mechanism of sorption to mineral surfaces under dry conditions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Effects of apple branch biochar on soil C mineralization and nutrient cycling under two levels of N.

PubMed

Li, Shuailin; Liang, Chutao; Shangguan, Zhouping

2017-12-31

The incorporation of biochar into soil has been proposed as a strategy for enhancing soil fertility and crop productivity. However, there is limited information regarding the responses of soil respiration and the C, N and P cycles to the addition of apple branch biochar at different rates to soil with different levels of N. A 108-day incubation experiment was conducted to investigate the effects of the rate of biochar addition (0, 1, 2 and 4% by mass) on soil respiration and nutrients and the activities of enzymes involved in C, N and P cycling under two levels of N. Our results showed that the application of apple branch biochar at rates of 2% and 4% increased the C-mineralization rate, while biochar amendment at 1% decreased the C-mineralization rate, regardless of the N level. The soil organic C and microbial biomass C and P contents increased as the rate of biochar addition was increased to 2%. The biochar had negative effects on β-glucosidase, N-acetyl-β-glucosaminidase and urease activity in N-poor soil but exerted a positive effect on all of these factors in N-rich soil. Alkaline phosphatase activity increased with an increase in the rate of biochar addition, but the available P contents after all biochar addition treatments were lower than those obtained in the treatments without biochar. Biochar application at rates of 2% and 4% reduced the soil nitrate content, particularly in N-rich soil. Thus, apple branch biochar has the potential to sequester C and improve soil fertility, but the responses of soil C mineralization and nutrient cycling depend on the rate of addition and soil N levels. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of Simulated Nitrogen Deposition on Soil Net Nitrogen Mineralization in the Meadow Steppe of Inner Mongolia, China

PubMed Central

Liu, Xing-ren; Ren, Jian-qiang; Li, Sheng-gong; Zhang, Qing-wen

2015-01-01

Effects of simulated nitrogen (N) deposition on soil net nitrogen mineralization (NNM) were examined in situ during two growing seasons, using the resin-core technique in the semiarid meadow steppe in Inner Mongolia, China. The aim of this study is to clarify the effect of N levels (0, 10, and 20 kg N ha−1yr−1) and forms (NH4 + and NO3 -) on soil mineral N and NNM. Our results showed that N levels had no significant differences on soil mineral N and NNM. In the first year, three N treatments ((NH4)2SO4, NH4Cl and KNO3) increased soil NH4 + concentrations but had no significant effects on soil NO3 - concentrations. In the second year, (NH4)2SO4 treatment increased soil NO3 - concentrations, NH4Cl and KNO3 treatments decreased them. Three N treatments significantly decreased soil NH4 + concentrations in the later stages of the second year. As for the soil NNM, three N treatments had no significant effects on the rates of soil NNM (R m) and net nitrification (R n) in the first year, but significantly decreased them in the second year. The contribution of N addition to Rm was higher from (NH4)2SO4 than from NH4Cl and KNO3. However, Soil R m was mainly affected by soil water content (SWC), accumulated temperature (Ta), and soil total N (TN). These results suggest that the short-term atmospheric N deposition may inhibit soil NNM in the meadow steppe of Inner Mongolia. PMID:26218275

Carbon dynamics under a maize-Faidherbia albida agroforestry system in Zambia

NASA Astrophysics Data System (ADS)

Yengwe, Jones; Chipatela, Floyd; Amalia, Okky; Lungu, Obed; De Neve, Stefaan

2017-04-01

Continued crop residue removal for other competing uses such as livestock or household has exacerbated the decline of soil organic matter. Foliar litter from indigenous agroforestry trees such as Faidherbia albida (F. albida) can be a source of organic matter input in resource constrained farmers' fields to mitigate the declining fertility status of many Zambian soils. A controlled incubation study was conducted to evaluate the short term degradability of F. albida litter and maize plant residue. Further, we assessed the effect of F. albida litter and maize residue amendments on microbial biomass carbon (MBC) and enzyme activity. Soils were collected from outside and under the canopies of F. albida trees from six sites with 8, 9, 11, 15, and two sites with > 35-year old trees. Soils from under the canopies were amended with F. albida+maize residue (FMU), F. albida litter (FU), maize residue (MU) and controls were not amended (CTRU). The soils from outside the canopy were amended with maize residue (MO) and controls were not amended (CTRO). These were adjusted to 50% WFPS and incubated for twelve weeks at 27°C to assess C mineralization, microbial biomass carbon (MBC) and enzyme activity (Dehydrogenase, β-glucosidase and β-glucosaminidase activity). The material used as amendment in the incubation experiment had two pools of carbon: a labile and a recalcitrant pool. The mixed amendment FMU had a significantly (p<0.05) higher C mineralization compared to the other amendments for all incubated soils. The treatment MU had a higher net C mineralized than FU. However, C mineralization from FU treatment was generally higher in the first 20 days of the incubation period but declined thereafter for all the soils. The net C mineralized from MU did not significantly differ with MO in all except soil from 11-year old trees. Enzyme activity and MBC consistently increased due to amendments for all soils. Enzyme activity was significantly (p<0.05) positively correlated with MBC in amended soils. Net C mineralized and microbial activity were high in FMU because of large C substrate added. Indicating a high C mineralization potential, MBC and enzyme activity for soils under the canopy compared with soils outside the canopy. F. albida trees therefore could be a source of labile C in F. albida-Maize systems nevertheless, in the long term, input from other crop residue such as maize and savanna grasses which have a large recalcitrant pool of C are important in sustaining SOC on these fields.

Soil Exometabolomics: An Approach to Investigate Adsorption of Metabolites on Soils and Minerals

NASA Astrophysics Data System (ADS)

Swenson, T.; Nico, P. S.; Northen, T.

2014-12-01

A large fraction of soil organic matter (SOM) is composed of small molecules of microbial origin resulting from lysed cells and released metabolites. However, the cycling of these nutrients by microorganisms, a critical component of the global carbon cycle, remains poorly understood. Although there are many biotic and abiotic factors affecting the accessibility of SOM to microbes, adsorption to mineral surfaces is among the most important. Here, we are developing exometabolomics methods to further understand the types of microbial metabolites remaining in the water extractable fraction of SOM (WEOM). To estimate which compounds adsorb to a sandy loam soil (obtained from the Angelo Coast Range Reserve in Mendocino, CA), an extract was prepared from the soil bacterium Pseudomonas stutzerii RCH2 grown on 13C acetate. This approach produced highly labeled metabolites that were easily discriminated from the endogenous soil metabolites by gas chromatography/ mass spectrometry. Comparison of the composition of the fresh bacteria extract with what was recovered following a 15 min incubation with soil revealed that only 26% of the metabolites showed >50% recovery in the WEOM. Most cations (polyamines) and anions showed <10% recovery. These represent metabolites that may be inaccessible to microbes in this environment and would be most likely to accumulate as SOM presumably due to binding with minerals and negatively-charged clay particles. Ongoing studies are focused on comparing the adsorption capacity of bacteria extract with several minerals (ferrihydrite, goethite, meghemite, lepidocrocite). Varying conditions such as metabolite-mineral contact time (ranging from hours to days) and temperature (4-37°C) will provide insight into how microbial metabolites behave in a given mineral-rich environment under certain climatic conditions.

Response of Soil Bulk Density and Mineral Nitrogen to Harvesting and Cultural Treatments

Treesearch

Minyi Zhou; Mason C. Carter; Thomas J. Dean

1998-01-01

The interactive effects of harvest intensity, site preparation, and fertilization on soil compaction and nitrogen mineralization were examined in a loblolly pine (Pinus taeda L.) stand growing on a sandy, well-drained soil in eastern Texas. The experimental design was 2 by 2 by 2 factorial, consisting of two harvesting treatments (mechanical whole-...

Lignin decomposition is sustained under fluctuating redox conditions in humid tropical forest soils

Treesearch

Steven J. Hall; Whendee L. Silver; Vitaliy I. Timokhin; Kenneth E. Hammel

2015-01-01

Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia is thought to suppress lignin decomposition, yet potential effects of oxygen (O2) variability in surface soils have not been explored. Here, we...

Estimating soil zinc concentrations using reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Sun, Weichao; Zhang, Xia

2017-06-01

Soil contamination by heavy metals has been an increasingly severe threat to nature environment and human health. Efficiently investigation of contamination status is essential to soil protection and remediation. Visible and near-infrared reflectance spectroscopy (VNIRS) has been regarded as an alternative for monitoring soil contamination by heavy metals. Generally, the entire VNIR spectral bands are employed to estimate heavy metal concentration, which lacks interpretability and requires much calculation. In this study, 74 soil samples were collected from Hunan Province, China and their reflectance spectra were used to estimate zinc (Zn) concentration in soil. Organic matter and clay minerals have strong adsorption for Zn in soil. Spectral bands associated with organic matter and clay minerals were used for estimation with genetic algorithm based partial least square regression (GA-PLSR). The entire VNIR spectral bands, the bands associated with organic matter and the bands associated with clay minerals were incorporated as comparisons. Root mean square error of prediction, residual prediction deviation, and coefficient of determination (R2) for the model developed using combined bands of organic matter and clay minerals were 329.65 mg kg-1, 1.96 and 0.73, which is better than 341.88 mg kg-1, 1.89 and 0.71 for the entire VNIR spectral bands, 492.65 mg kg-1, 1.31 and 0.40 for the organic matter, and 430.26 mg kg-1, 1.50 and 0.54 for the clay minerals. Additionally, in consideration of atmospheric water vapor absorption in field spectra measurement, combined bands of organic matter and absorption around 2200 nm were used for estimation and achieved high prediction accuracy with R2 reached 0.640. The results indicate huge potential of soil reflectance spectroscopy in estimating Zn concentrations in soil.

The repeated drying-wetting and freezing-thawing cycles affect only the active pool of soil organic matter

NASA Astrophysics Data System (ADS)

Semenov, Vyacheslav; Zinyakova, Natalya; Tulina, Anastasiya

2016-04-01

The decrease in the content of soil organic carbon, particularly in active form, is one of the major problems of the 21st century, which is closely related to the disturbance of the biogeochemical carbon cycle and to the increase in the emission of carbon dioxide into the atmosphere. The main reasons for the SOM losses are the surplus of the SOM active pool losses due to mineralization, erosion, and infiltration over the input of fresh organic matter to the soil, as well as the changes in the soil conditions and processes due to natural and anthropogenic disturbing impacts. Experiments were carried out with mixed samples from the upper layers of soddy-podzolic soil, gray forest soil, and typical chernozems. Soil samples as controls were incubated after wetting for 150 days. The dynamics and cumulative production of C-CO2 under stable temperature (22°C) and moisture conditions were determined; the initial content of potentially mineralizable organic matter (C0) in the soil at the beginning of the incubation was then calculated to use these data as the control. Other soil samples were exposed in flasks to the following successive treatments: wetting →incubation → freezing → thawing → incubation →drying. Six repeated cycles of disturbing impacts were performed for 140 days of the experiment. After six cycles, the soil samples were incubated under stable temperature and moisture conditions for 150 days. The wetting of dried soils and the thawing of frozen soils are accompanied by the pulsed dynamics of the C-CO2 production with an abrupt increase in the rate of the C-CO2 emission within several days by 2.7-12.4 and 1.6-2.7 times, respectively, compared to the stable incubation conditions. The rate of the C-CO2 production pulses under each subsequent impact decreased compared to the preceding one similarly for all studied soils, which could be due to the depletion in potentially mineralizable soil organic matter (C0). The cumulative extra C-CO2 production by soils of the natural lands during six cycles of disturbing impacts composed 21-40% of that by soils incubated under stable conditions; the corresponding values for the cultivated soils, including soil under the continuous bare fallow, were in the range of 45-82%. The structure of the active organic matter pool in uncultivated soils after six incubation cycles became similar to those for soils under the continuous bare fallow, as well as under farming agrocenoses. Following from the obtained results that the organic matter mobilized by disturbing impacts was predominantly mineralized in arable soils with an initially low C0 content, while a part of the mobilized organic matter was stabilized in untreated soils with the high initial C0 content. This work was supported by RSF. Project number 14-14-00625

Microscale soil structure development after glacial retreat - using machine-learning based segmentation of elemental distributions obtained by NanoSIMS

NASA Astrophysics Data System (ADS)

Schweizer, Steffen; Schlueter, Steffen; Hoeschen, Carmen; Koegel-Knabner, Ingrid; Mueller, Carsten W.

2017-04-01

Soil organic matter (SOM) is distributed on mineral surfaces depending on physicochemical soil properties that vary at the submicron scale. Nanoscale secondary ion mass spectrometry (NanoSIMS) can be used to visualize the spatial distribution of up to seven elements simultaneously at a lateral resolution of approximately 100 nm from which patterns of SOM coatings can be derived. Existing computational methods are mostly confined to visualization and lack spatial quantification measures of coverage and connectivity of organic matter coatings. This study proposes a methodology for the spatial analysis of SOM coatings based on supervised pixel classification and automatic image analysis of the 12C, 12C14N (indicative for SOM) and 16O (indicative for mineral surfaces) secondary ion distributions. The image segmentation of the secondary ion distributions into mineral particle surface and organic coating was done with a machine learning algorithm, which accounts for multiple features like size, color, intensity, edge and texture in all three ion distributions simultaneously. Our workflow allowed the spatial analysis of differences in the SOM coverage during soil development in the Damma glacier forefield (Switzerland) based on NanoSIMS measurements (n=121; containing ca. 4000 particles). The Damma chronosequence comprises several stages of soil development with increasing ice-free period (from ca. 15 to >700 years). To investigate mineral-associated SOM in the developing soil we obtained clay fractions (<2 μm) from two density fractions: light mineral (1.6 to 2.2 g cm3) and heavy mineral (>2.2 g cm3). We found increased coverage and a simultaneous development from patchy-distributed organic coatings to more connected coatings with increasing time after glacial retreat. The normalized N:C ratio (12C14N: (12C14N + 12C)) on the organic matter coatings was higher in the medium-aged soils than in the young and mature ones in both heavy and light mineral fraction. This reflects the sequential accumulation of proteinaceous SOM in the medium-aged soils and C-rich compounds in the mature soils. The results of our microscale image analysis correlated well with the SOM concentration of the fractions measured by elemental analyzer. Image analysis in combination with secondary ion distributions provides a powerful tool at the required microscale and enhances our mechanistic understanding of SOM stabilization in soil.

Response of soil organic carbon fractions, microbial community composition and carbon mineralization to high-input fertilizer practices under an intensive agricultural system

PubMed Central

Wu, Xueping; Gebremikael, Mesfin Tsegaye; Wu, Huijun; Cai, Dianxiong; Wang, Bisheng; Li, Baoguo; Zhang, Jiancheng; Li, Yongshan; Xi, Jilong

2018-01-01

Microbial mechanisms associated with soil organic carbon (SOC) decomposition are poorly understood. We aim to determine the effects of inorganic and organic fertilizers on soil labile carbon (C) pools, microbial community structure and C mineralization rate under an intensive wheat-maize double cropping system in Northern China. Soil samples in 0–10 cm layer were collected from a nine-year field trial involved four treatments: no fertilizer, CK; nitrogen (N) and phosphorus (P) fertilizers, NP; maize straw combined with NP fertilizers, NPS; and manure plus straw and NP fertilizers, NPSM. Soil samples were analyzed to determine labile C pools (including dissolved organic C, DOC; light free organic C, LFOC; and microbial biomass C, MBC), microbial community composition (using phospholipid fatty acid (PLFA) profiles) and SOC mineralization rate (from a 124-day incubation experiment). This study demonstrated that the application of chemical fertilizers (NP) alone did not alter labile C fractions, soil microbial communities and SOC mineralization rate from those observed in the CK treatment. Whereas the use of straw in conjunction with chemical fertilizers (NPS) became an additional labile substrate supply that decreased C limitation, stimulated growth of all PLFA-related microbial communities, and resulted in 53% higher cumulative mineralization of C compared to that of CK. The SOC and its labile fractions explained 78.7% of the variance of microbial community structure. Further addition of manure on the top of straw in the NPSM treatment did not significantly increase microbial community abundances, but it did alter microbial community structure by increasing G+/G- ratio compared to that of NPS. The cumulative mineralization of C was 85% higher under NPSM fertilization compared to that of CK. Particularly, the NPSM treatment increased the mineralization rate of the resistant pool. This has to be carefully taken into account when setting realistic and effective goals for long-term soil C stabilization. PMID:29668702

Response of soil organic carbon fractions, microbial community composition and carbon mineralization to high-input fertilizer practices under an intensive agricultural system.

PubMed

Li, Jing; Wu, Xueping; Gebremikael, Mesfin Tsegaye; Wu, Huijun; Cai, Dianxiong; Wang, Bisheng; Li, Baoguo; Zhang, Jiancheng; Li, Yongshan; Xi, Jilong

2018-01-01

Microbial mechanisms associated with soil organic carbon (SOC) decomposition are poorly understood. We aim to determine the effects of inorganic and organic fertilizers on soil labile carbon (C) pools, microbial community structure and C mineralization rate under an intensive wheat-maize double cropping system in Northern China. Soil samples in 0-10 cm layer were collected from a nine-year field trial involved four treatments: no fertilizer, CK; nitrogen (N) and phosphorus (P) fertilizers, NP; maize straw combined with NP fertilizers, NPS; and manure plus straw and NP fertilizers, NPSM. Soil samples were analyzed to determine labile C pools (including dissolved organic C, DOC; light free organic C, LFOC; and microbial biomass C, MBC), microbial community composition (using phospholipid fatty acid (PLFA) profiles) and SOC mineralization rate (from a 124-day incubation experiment). This study demonstrated that the application of chemical fertilizers (NP) alone did not alter labile C fractions, soil microbial communities and SOC mineralization rate from those observed in the CK treatment. Whereas the use of straw in conjunction with chemical fertilizers (NPS) became an additional labile substrate supply that decreased C limitation, stimulated growth of all PLFA-related microbial communities, and resulted in 53% higher cumulative mineralization of C compared to that of CK. The SOC and its labile fractions explained 78.7% of the variance of microbial community structure. Further addition of manure on the top of straw in the NPSM treatment did not significantly increase microbial community abundances, but it did alter microbial community structure by increasing G+/G- ratio compared to that of NPS. The cumulative mineralization of C was 85% higher under NPSM fertilization compared to that of CK. Particularly, the NPSM treatment increased the mineralization rate of the resistant pool. This has to be carefully taken into account when setting realistic and effective goals for long-term soil C stabilization.

Effects of organic matter removal and soil compaction on fifth-year mineral soil carbon and nitrogen contents for sites across the United States and Canada

Treesearch

Felipe G. Sanchez; Allan E. Tiarks; J. Marty Kranabetter; Deborah S. Page-Dumroese; Robert F. Powers; Paul T. Sanborn; William K. Chapman

2006-01-01

This study describes the main treatment effects of organic matter removal and compaction and a split-plot effect of competition control on mineral soil carbon (C) and nitrogen (N) pools. Treatment effects on soil C and N pools are discussed for 19 sites across five locations (British Columbia, Northern Rocky Mountains, Pacific Southwest, and Atlantic and Gulf coasts)...

Taking nature into lab: biomineralization by heavy metal resistant streptomycetes in soil

NASA Astrophysics Data System (ADS)

Schütze, E.; Weist, A.; Klose, M.; Wach, T.; Schumann, M.; Nietzsche, S.; Merten, D.; Baumert, J.; Majzlan, J.; Kothe, E.

2013-02-01

Biomineralization by heavy metal resistant streptomycetes was tested to evaluate the potential influence on metal mobilities in soil. Thus, we designed an experiment adopting conditions from classical laboratory methods to natural conditions prevailing in metal-rich soils with media spiked with heavy metals, soil agar, and nutrient enriched or unamended soil incubated with the bacteria. As a result, all strains were able to form struvite minerals on tryptic soy broth (TSB) media supplemented with AlCl2, MnCl2 and CuSO4, as well as on soil agar. Some strains additionally formed struvite on nutrient enriched contaminated and control soil, as well as on metal contaminated soil without addition of media components. In contrast, switzerite was exclusively formed on minimal media spiked with MnCl2 by four heavy metal resistant strains, and on nutrient enriched control soil by one strain. Hydrated nickel hydrogen phosphate was only crystallized on complex media supplemented with NiSO4 by most strains. Thus, mineralization is a~dominant property of streptomycetes, with different processes likely to occur under laboratory conditions and sub-natural to natural conditions. This new understanding may be transferred to formation of minerals in rock and sediment evolution, to ore deposit formation, and also might have implications for our understanding of biological metal resistance mechanisms. We assume that biogeochemical cycles, nutrient storage and metal resistance might be affected by formation and re-solubilization of minerals like struvite in soil at microscale.