Science.gov

Sample records for iron-oxyhydroxide soil minerals

  1. Iron oxyhydroxide mineralization on microbial extracellular polysaccharides

    SciTech Connect

    Chan, Clara S.; Fakra, Sirine C.; Edwards, David C.; Emerson, David; Banfield, Jillian F.

    2010-06-22

    Iron biominerals can form in neutral pH microaerophilic environments where microbes both catalyze iron oxidation and create polymers that localize mineral precipitation. In order to classify the microbial polymers that influence FeOOH mineralogy, we studied the organic and mineral components of biominerals using scanning transmission X-ray microscopy (STXM), micro X-ray fluorescence ({mu}XRF) microscopy, and high-resolution transmission electron microscopy (HRTEM). We focused on iron microbial mat samples from a creek and abandoned mine; these samples are dominated by iron oxyhydroxide-coated structures with sheath, stalk, and filament morphologies. In addition, we characterized the mineralized products of an iron-oxidizing, stalk-forming bacterial culture isolated from the mine. In both natural and cultured samples, microbial polymers were found to be acidic polysaccharides with carboxyl functional groups, strongly spatially correlated with iron oxyhydroxide distribution patterns. Organic fibrils collect FeOOH and control its recrystallization, in some cases resulting in oriented crystals with high aspect ratios. The impact of polymers is particularly pronounced as the materials age. Synthesis experiments designed to mimic the biomineralization processes show that the polysaccharide carboxyl groups bind dissolved iron strongly but release it as mineralization proceeds. Our results suggest that carboxyl groups of acidic polysaccharides are produced by different microorganisms to create a wide range of iron oxyhydroxide biomineral structures. The intimate and potentially long-term association controls the crystal growth, phase, and reactivity of iron oxyhydroxide nanoparticles in natural systems.

  2. Iron oxyhydroxide mineralization by microbes in terrestrial environments

    NASA Astrophysics Data System (ADS)

    Chan, C. S.; Fakra, S.; Banfield, J. F.

    2004-12-01

    Many microorganisms produce extracellular organic structures that become mineralized and thus preserved. As in higher organism mineralization (e.g. shells and bones), organics template mineral nucleation and control growth. However, polymer-mediated crystal growth is a more general phenomenon that can occur in extracellular, geochemically open systems. We have been studying microbial polymers mineralized by iron oxyhydroxides in a variety of natural environments, including a flooded mine in Wisconsin, creeks in Virginia and California, and cold springs in Oregon. Enrichment culturing showed that these environments are all populated by neutrophilic iron-oxidizers. We used scanning and transmission electron microscopy (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), and synchrotron-based scanning transmission X-ray microscopy (STXM) to investigate the mineralogy and organic polymer functional groups. Microscopic observations revealed that these samples, while often dominated by the sheaths and stalks generally attributed to Leptothrix spp. and Gallionella, actually contain mineralized structures with a wide range of morphologies. The extent of mineralization is variable, with some environments characterized by heavy encrustations that likely formed via abiotic precipitation. We focused on the lightly mineralized polymers as this allows us to more closely examine the organic-mineral interactions. STXM work shows that the organics in the flooded mine and Virginia creek have common functional groups, including carboxyls. However, the exact ratio of functional groups may be more dependent on environmental factors than species. Our previous work showed that organic polymer fibrils template unusually long akaganeite (beta FeOOH) crystals in biofilm samples from the flooded mine. Subsequent work has shown that polymers in other environments, including polymers contained in organized structures, also template iron oxyhydroxide mineralization. Thus, microbial polymer templation of iron oxide minerals appears to be a general phenomenon. We also examined polymer mineralization in culture and abiotic synthesis experiments. We combined alginate, a well-characterized microbial polymer with carboxylic functional groups, and Fe(III) in various forms and reproduced some of the simple structures found in nature. We used STXM (with C, N, O, and Fe NEXAFS) and Fe EXAFS to follow the influence of polymers during mineral formation. NEXAFS data collected to date clearly show an evolution in interactions between polymer functional groups as iron is bound and mineralization proceeds. An understanding of polymer-mediated formation of unique minerals will allow us to better establish these minerals as biosignatures.

  3. Magnetic Properties of Antiferromagnetic Iron Oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Guyodo, Y. J.; Till, J. L.; Lagroix, F.; Bonville, P.; Penn, R. L.; Sainctavit, P.; Carvallo, C.; ona-Nguema, G.; Morin, G.

    2013-12-01

    Weakly magnetic iron oxyhydroxides such as ferrihydrite, lepidocrocite or goethite are commonly found in diverse geological and environmental setting, including ground waters and streams, sediments, soils, or acid mine drainage. These minerals take part in multiple biological and abiological processes, and can evolve to more magnetic phases such as hematite, maghemite, or magnetite. Therefore, they represent key minerals with regard to paleoclimate, paleoenvironmental, and paleomagnetic studies. At this meeting, we will present low temperature magnetic properties acquired on fully characterized synthetic samples. The complex nature of the magnetism of these minerals is revealed by comparing magnetic data with other types of characterizations such as high-resolution transmission electron microscopy or synchrotron X-ray magnetic circular dichroism (XMCD), or by studying the early-stages of solid-state alteration (under oxidizing or reducing atmosphere). In particular, we will present recent results about the presence of ferri-magnetic nano-clusters in lepidocrocite, and about uncompensated magnetic moments in goethite nanoparticles.

  4. Linking selective chemical extraction of iron oxyhydroxides to arsenic bioaccessibility in soil.

    PubMed

    Palumbo-Roe, Barbara; Wragg, Joanna; Cave, Mark

    2015-12-01

    The relationship between As bioaccessibility using the physiologically based extraction test (PBET) and As extracted by hydroxylamine hydrochloride (HH), targeting the dissolution of amorphous Fe oxyhydroxides, is established in soils from the British Geological Survey Geochemical Baseline Survey of SW England, UK, to represent low As background and high As mineralised/mined soils. The HH-extracted As was of the same order of magnitude as the As extracted in the bioaccessibility test and proved to be a better estimate of bioaccessible As than total As (bioaccessible As - total As: r = 0.955; bioaccessible As - HH-extracted As: r = 0.974; p-values = 0.000). These results provide a means of estimating soil As bioaccessibility on the basis of the HH extraction. Further selective extraction data, using hydrochloride acid that seeks to dissolve both amorphous and crystalline Fe oxyhydroxides, indicates a decrease in the As bioaccessible fraction with the increase of the soil Fe oxyhydroxide crystallinity. PMID:26412265

  5. Modified composites based on mesostructured iron oxyhydroxide and synthetic minerals: a potential material for the treatment of various toxic heavy metals and its toxicity.

    PubMed

    Chung, Seung-Gun; Ryu, Jae-Chun; Song, Mi-Kyung; An, Byungryul; Kim, Song-Bae; Lee, Sang-Hyup; Choi, Jae-Woo

    2014-02-28

    The composites of mesostructured iron oxyhydroxide and/or commercial synthetic zeolite were investigated for use in the removal of toxic heavy metals, such as cadmium, copper, lead and arsenic, from aqueous solution. Four types of adsorbents, dried alginate beads (DABs), synthetic-zeolite impregnated beads (SZIBs), meso-iron-oxyhydroxide impregnated beads (MIOIBs) and synthetic-zeolite/meso-iron-oxyhydroxide composite beads (SZMIOIBs), were prepared for heavy metal adsorption tests. Laboratory experiments were conducted to investigate the removal efficiencies of cations and anions of heavy metals and the possibility of regenerating the adsorbents. Among these adsorbents, the MIOIBs can simultaneously remove cations and anions of heavy metals; they have high adsorption capacities for lead (60.1mgg(-1)) and arsenic (71.9mgg(-1)) compared with other adsorbents, such as DABs (158.1 and 0.0mgg(-1)), SZIB (42.9 and 0.0mgg(-1)) and SZMIOIB (54.0 and 5.9mgg(-1)) for lead and arsenic, respectively. Additionally, the removal efficiency was consistent at approximately 90%, notwithstanding repetitive regeneration. The characteristics of meso-iron-oxyhydroxide powder were confirmed by X-ray diffraction, Brunauer-Emmett-Teller and transmission electron microscopy. We also performed a comparative toxicity study that indicated that much lower concentrations of the powdered form of mesostructured iron oxyhydroxide had stronger cytotoxicity than the granular form. These results suggest that the granular form of meso iron oxyhydroxide is a more useful and safer adsorbent for heavy metal treatment than the powdered form. This research provides promising results for the application of MIOIBs as an adsorbent for various heavy metals from wastewater and sewage. PMID:24444456

  6. Assessing the utility of trace and rare earth elements as biosignatures in microbial iron oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Heim, Christine; Simon, Klaus; Ionescu, Danny; Reimer, Andreas; De Beer, Dirk; Quéric, Nadia-Valérie; Reitner, Joachim; Thiel, Volker

    2015-02-01

    Microbial iron oxyhydroxides are common deposits in natural waters, recent sediments and mine drainage systems and often contain significant accumulations of trace and rare earth elements (TREE). TREE patterns are widely used to characterize minerals and rocks, and to elucidate their evolution and origin. Whether and which characteristic TREE signatures distinguish between a biological and an abiological origin of iron minerals is still not well understood. Long-term flow reactor studies were performed in the Äspö Hard Rock Laboratory to investigate the development of microbial mats dominated by iron-oxidizing bacteria, namely Mariprofundus sp. and Gallionella sp. The experiments investigated the accumulation and fractionation of TREE under controlled conditions and enabled us to assess potential biosignatures evolving within the microbial iron oxyhydroxides. Concentrations of Be, Y, Zn, Zr, Hf, W, Th, Pb, and U in the microbial mats were 1e3- to 1e5-fold higher than in the feeder fluids whereas the rare earth elements and Y (REE+Y) contents were 1e4 and 1e6 fold enriched. Except for a hydrothermally induced Eu anomaly, the normalized REE+Y patterns of the microbial iron oxyhydroxides were very similar to published REE+Y distributions of Archaean Banded Iron Formations. The microbial iron oxyhydroxides from the flow reactors were compared to iron oxyhydroxides that were artificially precipitated from the same feeder fluid. These abiotic and inorganic iron oxyhydroxides show the same REE+Y distribution patterns. Our results indicate that the REE+Y mirror quite exactly the water chemistry, but they do not allow to distinguish microbially mediated from inorganic iron precipitates. All TREE studied showed an overall similar fractionation behavior in biogenic, abiotic and inorganic iron oxyhydroxides. Exceptions are Ni and Tl, which were only accumulated in the microbial iron oxyhydroxides and may point to a potential usage of these elements as microbial biosignatures.

  7. Microbial reduction of ferric iron oxyhydroxides as a way for remediation of grey forest soils heavily polluted with toxic metals by infiltration of acid mine drainage

    NASA Astrophysics Data System (ADS)

    Georgiev, Plamen; Groudev, Stoyan; Spasova, Irena; Nicolova, Marina

    2015-04-01

    The abandoned uranium mine Curilo is a permanent source of acid mine drainage (AMD) which steadily contaminated grey forest soils in the area. As a result, the soil pH was highly acidic and the concentration of copper, lead, arsenic, and uranium in the topsoil was higher than the relevant Maximum Admissible Concentration (MAC) for soils. The leaching test revealed that approximately half of each pollutant was presented as a reducible fraction as well as the ferric iron in horizon A was presented mainly as minerals with amorphous structure. So, the approach for remediation of the AMD-affected soils was based on the process of redoxolysis carried out by iron-reducing bacteria. Ferric iron hydroxides reduction and the heavy metals released into soil solutions was studied in the dependence on the source of organic (fresh or silage hay) which was used for growth and activity of soil microflora, initial soil pH (3.65; 4.2; and 5.1), and the ion content of irrigation solutions. The combination of limestone (2.0 g/ kg soil), silage addition (at rate of 45 g dry weight/ kg soil) in the beginning and reiterated at 6 month since the start of soil remediation, and periodical soil irrigation with slightly acidic solutions containing CaCl2 was sufficient the content of lead and arsenic in horizon A to be decreased to concentrations similar to the relevant MAC. The reducible, exchangeable, and carbonate mobile fractions were phases from which the pollutants was leached during the applied soil remediation. It determined the higher reduction of the pollutants bioavailability also as well as the process of ferric iron reduction was combined with neutralization of the soil acidity to pH (H2O) 6.2.

  8. XAS evidence of As(V) association with iron oxyhydroxides in a contaminated soil at a former arsenical pesticide processing plant.

    PubMed

    Cancs, B; Juillot, F; Morin, G; Laperche, V; Alvarez, L; Proux, O; Hazemann, J L; Brown, G E; Calas, G

    2005-12-15

    The molecular-level speciation of arsenic has been determined in a soil profile in the Massif Central near Auzon, France that was impacted by As-based pesticides by combining conventional techniques (XRD, selective chemical extractions) with X-ray absorption spectroscopy (XAS). The arsenic concentration is very high at the top (>7000 mg kg(-1)) and decreases rapidly downward to a few hundreds of milligrams per kilogram. A thin layer of schultenite (PbHAsO4), a lead arsenate commonly used as an insecticide until the middle of the 20th century, was found at 10 cm depth. Despite the occurrence of this As-bearing mineral, oxalate extraction indicated that more than 65% of the arsenic was released upon dissolution of amorphous iron oxides, suggesting a major association of arsenic with these phases within the soil profile. Since oxalate extraction cannot unambiguously distinguish among the various chemical forms of arsenic, these results were confirmed by a direct in situ determination of arsenic speciation using XAS analysis. XANES data indicate that arsenic occurs mainly as As(V) along the soil profile except for the topsoil sample where a minor amount (7%) of As(III) was detected. EXAFS spectra of soil samples were fit by linear combinations of model compounds spectra and by a shell-by-shell method. These procedures clearly confirmed that As(V) is mainly (at least 80 wt %) associated with amorphous Fe(III) oxides as coprecipitates within the soil profile. If any, the proportion of schultenite, which was evidenced by XRD in a separate thin white layer, does not account for more than 10 wt % of arsenic in soil samples. This study emphasizes the importance of iron oxides in restricting arsenic dispersal within soils following dissolution of primary As-bearing solids manufactured for use as pesticides and released into the soils. PMID:16475314

  9. Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: Roles of particle size and acid anion in iron dissolution

    PubMed Central

    Rubasinghege, Gayan; Lentz, Robert W.; Scherer, Michelle M.; Grassian, Vicki H.

    2010-01-01

    A number of recent studies have shown that iron dissolution in Fe-containing dust aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and iron speciation. All of these factors need to be incorporated into atmospheric chemistry models if these models are to accurately predict the impact of Fe-containing dusts into open ocean waters. In this report, we combine dissolution measurements along with spectroscopy and microscopy to focus on nanoscale size effects in the dissolution of Fe-containing minerals in low-pH environments and the importance of acid type, including HNO3, H2SO4, and HCl, on dissolution. All of these acids are present in the atmosphere, and dust particles have been shown to be associated with nitrate, sulfate, and/or chloride. These measurements are done under light and dark conditions so as to simulate and distinguish between daytime and nighttime atmospheric chemical processing. Both size (nano- versus micron-sized particles) and anion (nitrate, sulfate, and chloride) are found to play significant roles in the dissolution of ?-FeOOH under both light and dark conditions. The current study highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol. PMID:20360560

  10. Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: roles of particle size and acid anion in iron dissolution.

    PubMed

    Rubasinghege, Gayan; Lentz, Robert W; Scherer, Michelle M; Grassian, Vicki H

    2010-04-13

    A number of recent studies have shown that iron dissolution in Fe-containing dust aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and iron speciation. All of these factors need to be incorporated into atmospheric chemistry models if these models are to accurately predict the impact of Fe-containing dusts into open ocean waters. In this report, we combine dissolution measurements along with spectroscopy and microscopy to focus on nanoscale size effects in the dissolution of Fe-containing minerals in low-pH environments and the importance of acid type, including HNO(3), H(2)SO(4), and HCl, on dissolution. All of these acids are present in the atmosphere, and dust particles have been shown to be associated with nitrate, sulfate, and/or chloride. These measurements are done under light and dark conditions so as to simulate and distinguish between daytime and nighttime atmospheric chemical processing. Both size (nano- versus micron-sized particles) and anion (nitrate, sulfate, and chloride) are found to play significant roles in the dissolution of alpha-FeOOH under both light and dark conditions. The current study highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol. PMID:20360560

  11. Biomimetic lithography and deposition kinetics of iron oxyhydroxide thin films

    SciTech Connect

    Rieke, P.C.; Wood, L.L.; Marsh, B.M.; Fryxell, G.E.; Engelhard, M.H.; Baer, D.R.; Tarasevich, B.J. |; John, C.M.

    1993-12-01

    Heterogeneous nucleation and crystal growth on functionalized organic substrates is a critical step in biological hard tissue formation. Self assembled monolayers can be derivatized with various organic functional groups to mimic the ``nucleation proteins`` for induction of mineral growth. Studies of nucleation and growth on SAMs can provide a better understanding of biomineralization and can also form the basis of a superior thin film deposition process. We demonstrate that micron-scale, electron and ion beam, lithographic techniques can be used to pattern SAMs with functional organic groups that either inhibit or promote mineral deposition. Patterned films of iron oxyhydroxide were deposited on the areas patterned with nucleation sites. Studies of the deposition kinetic of these films show that indeed the surface induces heterogeneous nucleation and that film formation does not occur via absorption of polymers or colloidal material formed homogeneously in solution. The nucleus interfacial free energy was calculated to be 24 mJ/m2 on a SAM surface composed entirely of sulfonate groups.

  12. Adsorption of selenium by amorphous iron oxyhydroxide and manganese dioxide

    USGS Publications Warehouse

    Balistrieri, L.S.; Chao, T.T.

    1990-01-01

    This work compares and models the adsorption of selenium and other anions on a neutral to alkaline surface (amorphous iron oxyhydroxide) and an acidic surface (manganese dioxide). Selenium adsorption on these oxides is examined as a function of pH, particle concentration, oxidation state, and competing anion concentration in order to assess how these factors might influence the mobility of selenium in the environment. The data indicate that 1. 1) amorphous iron oxyhydroxide has a greater affinity for selenium than manganese dioxide, 2. 2) selenite [Se(IV)] adsorption increases with decreasing pH and increasing particle concentration and is stronger than selenate [Se(VI)] adsorption on both oxides, and 3. 3) selenate does not adsorb on manganese dioxide. The relative affinity of selenate and selenite for the oxides and the lack of adsorption of selenate on a strongly acidic surface suggests that selenate forms outer-sphere complexes while selenite forms inner-sphere complexes with the surfaces. The data also indicate that the competition sequence of other anions with respect to selenite adsorption at pH 7.0 is phosphate > silicate > molybdate > fluoride > sulfate on amorphous iron oxyhydroxide and molybdate ??? phosphate > silicate > fluoride > sulfate on manganese dioxide. The adsorption of phosphate, molybdate, and silicate on these oxides as a function of pH indicates that the competition sequences reflect the relative affinities of these anions for the surfaces. The Triple Layer surface complexation model is used to provide a quantitative description of these observations and to assess the importance of surface site heterogeneity on anion adsorption. The modeling results suggest that selenite forms binuclear, innersphere complexes with amorphous iron oxyhydroxide and monodentate, inner-sphere complexes with manganese dioxide and that selenate forms outer-sphere, monodentate complexes with amorphous iron oxyhydroxide. The heterogeneity of the oxide surface sites is reflected in decreasing equilibrium constants for selenite with increasing adsorption density and both experimental observations and modeling results suggest that manganese dioxide has fewer sites of higher energy for selenite adsorption than amorphous iron oxyhydroxide. Modeling and interpreting the adsorption of phosphate, molybdate, and silicate on the oxides are made difficult by the lack of constraint in choosing surface species and the fact that equally good fits can be obtained with different surface species. Finally, predictions of anion competition using the model results from single adsorbate systems are not very successful because the model does not account for surface site heterogeneity. Selenite adsorption data from a multi-adsorbate system could be fit if the equilibrium constant for selenite is decreased with increasing anion adsorption density. ?? 1990.

  13. Molecular Mechanisms of Iron Oxyhydroxide Biomineralization

    NASA Astrophysics Data System (ADS)

    Chan, C. S.; Fakra, S.; de Stasio, G.; Banfield, J. F.

    2003-12-01

    Neutrophilic iron-oxidizing microbes such as Gallionella and PV-1 (Emerson and Moyer, 1997) extrude polymers that become encrusted with iron oxides. Little is known about the identity of these polymers, their biological function and the roles they play in mineralization. To this end, we are investigating iron oxidizers in natural terrestrial iron-rich microbial mat communities, culturing and characterizing them in the laboratory and performing abiotic synthesis experiments based on the natural mineralization processes. Our sampling site is in a flooded former lead-zinc mine in Tennyson, WI, which is host to thick reddish-orange microbial mats. Scanning and transmission electron microscopy studies show that the mat is composed of iron oxide-covered stalks and sheaths (like those formed by Gallionella and Leptothrix spp.), as well as tangled masses of mineralized filaments. There is evidence of polymer influence on mineral phase and morphology in the form of extremely thin (few-unit cell wide), microns-long akaganeite (β -FeOOH) crystals at the center of these mineralized filaments. We are using synchrotron-based X-ray spectromicroscopy (PEEM-photoelectron emisson microscopy and STXM-scanning transmission X-ray microscopy), which has the ability to give chemical information on heterogenous samples at high spatial resolutions. Both PEEM and STXM show that these filaments contain polysaccharides, which are likely templating the akaganeite formation. Initial iron oxide synthesis experiments using model microbial polysaccharides support this hypothesis. Further synthesis and characterization by X-ray absorption and infrared spectroscopy methods is being performed in order to elucidate the molecular mechanisms of mineral nucleation and growth.

  14. Oxygen and hydrogen isotope compositions of pedogenic phyllosilicates and iron oxyhydroxides: Development of modern surface domain arrays and implications for paleotemperature reconstructions

    NASA Astrophysics Data System (ADS)

    Tabor, N. J.; Montanez, I. P.

    2002-12-01

    Mineralogic, chemical, and oxygen and hydrogen isotope compositions of 68 different modern soil and paleosol phyllosilicate and iron oxyhydroxide samples are presented. The chemical and mineralogic data are used in conjunction with published thermodynamic data to calculate hydrogen and oxygen isotope fractionation factors for each sample. These temperature-dependent fractionation values are then combined with modern global oxygen and hydrogen isotope compositions of meteoric water and temperature data from the IAEA database to construct modern surface domains (MSD) for each phyllosilicate and iron oxyhydroxide sample with the coordinates dD and d18O. The hydrogen isotopic compositions of the phyllosilicates range from -108S to -24S, whereas the oxygen isotopic compositions range from +10.2S to +22.7S. The hydrogen isotopic compositions of the iron oxyhydroxides range from -113S to -154S, whereas the oxygen isotopic compositions range from +3.1S to -3.2S. All of the phyllosilicate samples from modern soils plot within the MSD and yield equilibrium temperatures of formation similar to measured temperatures at each respective site. These results suggest that published thermodynamic data provide good estimates of natural systems. Paleo-equatorial Permo-Pennsylvanian phyllosilicates and iron oxyhydroxides plot within the MSD, or at slightly higher temperatures than MSD values (25 to 35 C). Eocene kaolinites plot within the MSD with equilibrium temperatures above modern temperatures (22). Late Triassic iron oxyhydroxides from Argentina plot within the modern surface domain at temperatures of 12 C. However, the phyllosilicate data points plot well outside their respective MSDs, suggesting the phyllosilicate ? D values of these Triassic samples have likely been altered by proton-diffusion.

  15. Sequestration of non-pure carbon dioxide streams in iron oxyhydroxide-containing saline repositories

    USGS Publications Warehouse

    Garcia, S.; Rosenbauer, Robert J.; Palandri, James L.; Maroto-Valer, M. Mercedes

    2012-01-01

    Iron oxyhydroxide, goethite (α-FeOOH), was evaluated as a potential formation mineral reactant for trapping CO2 in a mineral phase such as siderite (FeCO3), when a mixture of CO2-SO 2 flue gas is injected into a saline aquifer. Two thermodynamic simulations were conducted, equilibrating a CO2-SO2 fluid mixture with a NaCl-brine and Fe-rich rocks at 150 °C and 300 bar. The modeling studies evaluated mineral and fluid composition at equilibrium and the influence of pH buffering in the system. Results show siderite precipitates both in the buffered and unbuffered system; however, the presence of an alkaline pH buffer enhances the stability of the carbonate. Based on the model, an experiment was designed to compare with thermodynamic predictions. A CO2-SO2 gas mixture was reacted in 150 ml of NaCl-NaOH brine containing 10 g of goethite at 150 °C and 300 bar for 24 days. Mineralogical and brine chemistry confirmed siderite as the predominant reaction product in the system. Seventy-six mg of CO2 are sequestered in siderite per 10 g of goethite.

  16. Effect of Transport and Aging Processes on Metal Speciation in Iron Oxyhydroxide Aggregates, Tar Creek Superfund Site, Oklahoma

    NASA Astrophysics Data System (ADS)

    Estes, E. R.; Schaider, L. A.; Shine, J. P.; Brabander, D. J.

    2010-12-01

    Following the cessation of mining activity in the late 20th century, Tar Creek Superfund Site was left highly contaminated by Pb, Zn, and Cd. Tar Creek, which flows through the site and into the Neosho River, has been studied extensively because of its potential to transport metals from the mining site to downstream communities. Previous research identified aggregated iron oxyhydroxide material, which forms when mine seepage mixes with Tar Creek surface water, as a major transport vector of metals. Frequent flooding in Tar Creek deposits aggregates on downstream floodplains, where wetting and drying processes alter the speciation of iron and other metals. This study seeks to better quantify those changes and to determine how transport and aging affects the human and ecological health risk. Sequential extractions of aggregate samples collected from the creek demonstrate that Fe is present in both amorphous (10-35% of Fe extracted) and more crystalline (8-23% of Fe extracted) phases. Substantial portions of heavy metals sorb to amorphous iron oxyhydroxide phases (accounting for 10-30% of Pb and Zn extracted) but are not associated with more crystalline iron oxide phases (representing only 1% or less of the Pb and Zn extracted). Samples have a high organic matter content (18-25% mass loss on ignition), but only Fe was significantly extracted by the oxidizing step targeting organic matter (1-2% of Pb and Zn extracted, but 10-26% of Fe extracted). The majority of metals were extracted by the soluble or residual steps. If metals and organic matter inhibit transformation of amorphous iron oxyhydroxide material to nano and crystalline iron oxides, then a steady-state volume of amorphous iron oxyhydroxide material with a high total sorption capacity may exist within Tar Creek, enhancing the metal flux accommodated by this transport mechanism. Once transported downstream and deposited on floodplains, however, it is hypothesized that repeated changes in soil matrix composition and thermodynamic conditions could facilitate a transformation to more crystalline iron phases and increase metal bioavailability. While preliminary data from in-creek aggregates show no clear trend in mineralogical composition with downstream transport, only the furthest downstream samples have 2-line ferrihydrite in amounts detectable by XRD.

  17. The nanosphere iron mineral(s) in Mars soil

    NASA Technical Reports Server (NTRS)

    Banin, A.; Ben-Shlomo, T.; Margulies, L.; Blake, D. F.; Mancinelli, R. L.; Gehring, A. U.

    1993-01-01

    A series of surface-modified clays containing nanophase (np) iron/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these 'Mars-soil analogs' were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxyl mineral such as 'green rust', or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable meaghemite (gamma-Fe203) by mild heat treatment and then to nanophase hematite (aplha-Fe203) by extensive heat treatment. Their chemical reactivity offers a plausible mechanism for the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxide and silicate phase surfaces. The mode of formation of these (nanophase) iron oxides on Mars is still unknown.

  18. Associations between iron oxyhydroxide nanoparticle growth and metal adsorption/structural incorporation

    SciTech Connect

    Kim, C.S.; Lentini, C.J.; Waychunas, G.A.

    2008-09-15

    The interaction of metal ions and oxyanions with nanoscale mineral phases has not yet been extensively studied despite the increased recognition of their prevalence in natural systems as a significant component of geomedia. A combination of macroscopic uptake studies to investigate the adsorption behavior of As(V), Cu(II), Hg(II), and Zn(II) onto nanoparticulate goethite ({alpha}-FeOOH) as a function of aging time at elevated temperature (75 C) and synchrotron-based X-ray studies to track changes in both the sorption mode and the rate of nanoparticle growth reveal the effects that uptake has on particle growth. Metal(loid) species which sorb quickly to the iron oxyhydroxide particles (As(V), Cu(II)) appear to passivate the particle surface, impeding the growth of the nanoparticles with progressive aging; in contrast, species that sorb more slowly (Hg(II), Zn(II)) have considerably less impact on particle growth. Progressive changes in the speciation of these particular metals with time suggest shifts in the mode of metal uptake with time, possibly indicating structural incorporation of the metal(loid) into the nanoparticle; this is supported by the continued increase in uptake concomitant with particle growth, implying that metal species may transform from surface-sorbed species to more structurally incorporated forms. This type of incorporation would have implications for the long-term fate and mobility of metals in contaminated regions, and affect the strategy for potential remediation/modeling efforts.

  19. Biogenic iron oxyhydroxide formation at mid-ocean ridge hydrothermal vents: Juan de Fuca Ridge

    SciTech Connect

    Toner, Brandy M.; Santelli, Cara M.; Marcus, Matthew A.; Wirth, Richard; Chan, Clara S.; McCollom, Thomas; Bach, Wolfgang; Edwards, Katrina J.

    2008-05-22

    Here we examine Fe speciation within Fe-encrusted biofilms formed during 2-month seafloor incubations of sulfide mineral assemblages at the Main Endeavor Segment of the Juan de Fuca Ridge. The biofilms were distributed heterogeneously across the surface of the incubated sulfide and composed primarily of particles with a twisted stalk morphology resembling those produced by some aerobic Fe-oxidizing microorganisms. Our objectives were to determine the form of biofilm-associated Fe, and identify the sulfide minerals associated with microbial growth. We used micro-focused synchrotron-radiation X-ray fluorescence mapping (mu XRF), X-ray absorption spectroscopy (mu EXAFS), and X-ray diffraction (mu XRD) in conjunction with focused ion beam (FIB) sectioning, and highresolution transmission electron microscopy (HRTEM). The chemical and mineralogical composition of an Fe-encrusted biofilm was queried at different spatial scales, and the spatial relationship between primary sulfide and secondary oxyhydroxide minerals was resolved. The Fe-encrusted biofilms formed preferentially at pyrrhotite-rich (Fe1-xS, 0<_ x<_ 0.2) regions of the incubated chimney sulfide. At the nanometer spatial scale, particles within the biofilm exhibiting lattice fringing and diffraction patterns consistent with 2-line ferrihydrite were identified infrequently. At the micron spatial scale, Fe mu EXAFS spectroscopy and mu XRD measurements indicate that the dominant form of biofilm Fe is a short-range ordered Fe oxyhydroxide characterized by pervasive edge-sharing Fe-O6 octahedral linkages. Double corner-sharing Fe-O6 linkages, which are common to Fe oxyhydroxide mineral structures of 2-line ferrihydrite, 6-line ferrihydrite, and goethite, were not detected in the biogenic iron oxyhydroxide (BIO). The suspended development of the BIO mineral structure is consistent with Fe(III) hydrolysis and polymerization in the presence of high concentrations of Fe-complexing ligands. We hypothesize that microbiologically produced Fe-complexing ligands may play critical roles in both the delivery of Fe(II) to oxidases, and the limited Fe(III) oxyhydroxide crystallinity observed within the biofilm. Our research provides insight into the structure and formation of naturally occurring, microbiologically produced Fe oxyhydroxide minerals in the deep-sea. We describe the initiation of microbial seafloor weathering, and the morphological and mineralogical signals that result from that process. Our observations provide a starting point from which progressively older and more extensively weathered seafloor sulfide minerals may be examined, with the ultimate goal of improved interpretation of ancient microbial processes and associated biological signatures.

  20. Molecular-Scale Investigation with ESI-FT-ICR-MS on Fractionation of Dissolved Organic Matter Induced by Adsorption on Iron Oxyhydroxides.

    PubMed

    Lv, Jitao; Zhang, Shuzhen; Wang, Songshan; Luo, Lei; Cao, Dong; Christie, Peter

    2016-03-01

    Adsorption by minerals is a common geochemical process of dissolved organic matter (DOM) which may induce fractionation of DOM at the mineral-water interface. Here, we examine the molecular fractionation of DOM induced by adsorption onto three common iron oxyhydroxides using electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Ferrihydrite exhibited higher affinity to DOM and induced more pronounced molecular fractionation of DOM than did goethite or lepidocrocite. High molecular weight (>500 Da) compounds and compounds high in unsaturation or rich in oxygen including polycyclic aromatics, polyphenols and carboxylic compounds had higher affinity to iron oxyhydroxides and especially to ferrihydrite. Low molecular weight compounds and compounds low in unsaturation or containing few oxygenated groups (mainly alcohols and ethers) were preferentially maintained in solution. This study confirms that the double bond equivalence and the number of oxygen atoms are valuable parameters indicating the selective fractionation of DOM at mineral and water interfaces. The results of this study provide important information for further understanding the behavior of DOM in the natural environment. PMID:26815589

  1. The immobilization of U(vi) on iron oxyhydroxides under various physicochemical conditions.

    PubMed

    Ping, Li; Zhuoxin, Yin; Jianfeng, Lin; Qiang, Jin; Yaofang, Du; Qiaohui, Fan; Wangsuo, Wu

    2014-01-01

    The immobilization of U(vi) at the solid-water interface is an important process affecting its transportation and migration in the environment, and is predominantly controlled by the sorption behavior of U(vi). In this study, U(vi) sorption on Fe(ii) and Fe(iii) oxyhydroxides prepared by a coprecipitation method was studied under a range of physicochemical conditions, including pH, ionic strength, presence of humic acid (HA) and temperature. The results showed that the sorption of U(vi) on iron oxyhydroxides is chemical, and that the principal rate limitation is due to intraparticle diffusion. The sorption of U(vi) on iron oxyhydroxides is strongly dependent on pH, but only weakly dependent on ionic strength through the entire pH range studied. Under acidic conditions, the presence of HA increases U(vi) sorption to a large degree, but an inhibiting effect on the sorption of U(vi) can be observed under alkaline conditions, due to the formation of soluble U(vi)-HA complexes. The sorption of U(vi) on iron oxyhydroxides is an endothermic process and favors high temperatures. The surface complexation model suggests three dominant monodentate inner-sphere complexes of [triple bond, length as m-dash]Fe(s)OUO2(+) (log K = 1.65), [triple bond, length as m-dash]Fe(w)OUO2OH(0) (log K = -8.00), and [triple bond, length as m-dash]Fe(w)OUO2(CO3)2(3-) (log K = 17.50), contributing to U(vi) sorption on iron oxyhydroxides over the entire observed pH range. PMID:25043996

  2. Comparison study on transformation of iron oxyhydroxides: Based on theoretical and experimental data

    SciTech Connect

    Lu Bin; Guo Hui; Li Ping; Liu Hui; Wei Yu; Hou Denglu

    2011-08-15

    We have investigated the catalytic transformation of ferrihydrite, feroxyhyte, and lepidocrocite in the presence of Fe(II). In this paper, the transformation from akaganeite and goethite to hematite in the presence of trace Fe(II) was studied in detail. The result indicates that trace Fe(II) can accelerate the transformation of akaganeite and goethite. Compared with the transformation of other iron oxyhydroxides (e.g., ferrihydrite, feroxyhyte, lepidocrocite, and akaganeite), a complete transformation from goethite to hematite was not observed in the presence of Fe(II). On the basis of our earlier and present experimental results, the transformation of various iron oxyhydroxides was compared based on their thermodynamic stability, crystalline structure, transformation mechanism, and transformation time. - Graphical abstract: The transformation of various iron oxyhydroxides in the presence of trace Fe(II) was compared based on experimental results, thermodynamic stability, crystalline structure, and transformation mechanism. Highlights: > Fe(II) can accelerate the transformation from akaganeite to hematite. > Small particles of goethite can transform to hematite in the presence of Fe(II). > Some hematite particles were found to be embedded within the crystal of goethite. > The relationship between structure and transformation mechanism was revealed.

  3. To improve the performance of sediment microbial fuel cell through amending colloidal iron oxyhydroxide into freshwater sediments.

    PubMed

    Zhou, Yan-Li; Yang, Ying; Chen, Mo; Zhao, Zhi-Wei; Jiang, He-Long

    2014-05-01

    Effects of iron oxide amendment into freshwater sediments on performance of sediment microbial fuel cell (SMFC) were investigated. It was found that amending amorphous bulk ferric oxyhydroxide, and crystalline goethite and magnetite did not affect SMFC operation. However, amendment of the mixed solution including soluble ferric citrate and colloidal iron oxyhydroxide, stably improved SMFC performance with voltage outputs up to threefolds higher than those without amendment. The enhanced voltage production corresponded to lower anode potential, but was not related to organic matter removal in sediments. Further experiments demonstrated that colloidal iron oxyhydroxide instead of soluble ferric iron played an important role in voltage production through maintaining high-concentration ferrous iron in pore water of sediments as electron shuttle and for chemical oxidation on the anode. Thus, colloidal iron oxyhydroxide amendment was a promising strategy to improve power production from SMFC employed in sediments especially with low content of organic matters. PMID:24657753

  4. Electron transport in pure and substituted iron oxyhydroxides by small-polaron migration

    SciTech Connect

    Alexandrov, Vitaly Rosso, Kevin M.

    2014-06-21

    Iron oxyhydroxides (FeOOH) are common crystalline forms of iron that play a critical role in technology and the natural environment via a variety of important reduction-oxidation reactions, including electrical semiconduction as an aspect. However, a basic understanding of the electron transport properties of these systems is still lacking. We examine the electron mobility in goethite (α-FeOOH), akaganéite (β-FeOOH), and lepidocrocite (γ-FeOOH) polymorphs by means of density functional theory based (DFT+U) calculations. We show that room temperature charge transport should be dominated by the small-polaron hopping type, and that the attendant mobility should be highest for pure goethite and akaganéite. Hopping pathways through the various lattices are discussed in terms of individual electron exchange steps and rates for each. Given the usual occurrence of compositional impurities in natural iron oxyhydroxides, we also investigate the effect of common stoichiometric defects on the electron hopping activation energies such as Al and Cr substitutional cations in goethite, and Cl anions in the channels of akaganéite.

  5. Electron transport in pure and substituted iron oxyhydroxides by small-polaron migration

    SciTech Connect

    Alexandrov, Vitali Y.; Rosso, Kevin M.

    2014-08-12

    Iron oxyhydroxides (FeOOH) are common crystalline forms of iron that play a critical role in technology and the natural environment via a variety of important reduction-oxidation reactions, including electrical semiconduction as an aspect. However, a basic understanding of the electron transport properties of these systems is still lacking. We examine the electron mobility in goethite (α-FeOOH), akaganéite (β-FeOOH), and lepidocrocite (γ -FeOOH) polymorphs by means of density functional theory based (DFT+U) calculations.We show that room temperature charge transport should be dominated by the small-polaron hopping type, and that the attendant mobility should be highest for pure goethite and akaganéite. Hopping pathways through the various lattices are discussed in terms of individual electron exchange steps and rates for each. Given the usual occurrence of compositional impurities in natural iron oxyhydroxides, we also investigate the effect of common stoichiometric defects on the electron hopping activation energies such as Al and Cr substitutional cations in goethite, and Cl anions in the channels of akaganéite.

  6. Molecular Dynamics Simulation Study of the Early Stages of Nucleation of Iron Oxyhydroxide Nanoparticles in Aqueous Solutions.

    PubMed

    Zhang, Hengzhong; Waychunas, Glenn A; Banfield, Jillian F

    2015-08-20

    Nucleation is a fundamental step in crystal growth. Of environmental and materials relevance are reactions that lead to nucleation of iron oxyhydroxides in aqueous solutions. These reactions are difficult to study experimentally due to their rapid kinetics. Here, we used classical molecular dynamics simulations to investigate nucleation of iron hydroxide/oxyhydroxide nanoparticles in aqueous solutions. Results show that in a solution containing ferric ions and hydroxyl groups, iron-hydroxyl molecular clusters form by merging ferric monomers, dimers, and other oligomers, driven by strong affinity of ferric ions to hydroxyls. When deprotonation reactions are not considered in the simulations, these clusters aggregate to form small iron hydroxide nanocrystals with a six-membered ring-like layered structure allomeric to gibbsite. By comparison, in a solution containing iron chloride and sodium hydroxide, the presence of chlorine drives cluster assembly along a different direction to form long molecular chains (rather than rings) composed of Fe-O octahedra linked by edge sharing. Further, in chlorine-free solutions, when deprotonation reactions are considered, the simulations predict ultimate formation of amorphous iron oxyhydroxide nanoparticles with local atomic structure similar to that of ferrihydrite nanoparticles. Overall, our simulation results reveal that nucleation of iron oxyhydroxide nanoparticles proceeds via a cluster aggregation-based nonclassical pathway. PMID:26222332

  7. The Formation and Aggregation of Iron Oxyhydroxide Nanoparticles in the Aqueous Environment

    NASA Astrophysics Data System (ADS)

    Legg, Benjamin Adam

    This dissertation consists of four studies, which seek explain how iron oxyhydroxide nanoparticles nucleate and develop new structures via aggregation, within the aqueous environment. The aim of the first study is to determine the structure of ferrihydrite nanoparticle aggregates in aqua. This is achieved using complimentary cryo-TEM and SAXS methodologies. Ferrihydrite nanoparticles are known to form complex aggregate structures. Interpretation of SAXS data is difficult due to suspension polydispersity. Cryo-ET is used to obtain three-dimensional images of the nanoparticle suspensions. A variety of aggregate structures are observed, with branched networks of linear chains of particles being prevalent in most suspensions. The tomographic structural models are processed to determine aggregate fractal dimensions, using an autocorrelation function based approach. These results are combined with SAXS data to obtain a more comprehensive understanding of the suspension complexity. The networks of linear chains are shown to possess low fractal dimensions, between 1.0 and 1.4; significantly lower than would be expected from traditional models for aggregation. This has important consequences for the aggregate's physical behavior, and allows very large aggregates to exist in stable colloidal suspension without flocculation. The second study addresses how the ferrihydrite aggregate structure responds to changes in the ionic strength of the suspension, and how low-dimensional aggregate structures may influence nanoparticle transport through subsurface environments. Introducing ferrihydrite particle aggregates into solutions of 2 mM to 50 mM NaNO3 is shown to induce aggregate collapse, with more salt leading to the formation of denser aggregate structures and eventual flocculation. Complementary experiments show that millimolar quantities of NaNO3 induce a fundamental change in nanoparticle transport through a saturated quartz sand column. In deionized water, where low fractal dimension aggregates are stable, nanoparticles deposit evenly throughout the column, which soon saturates with particles so that subsequent injections are transported freely. When conditions favor aggregate collapse, dense localized accumulations occur and more nanoparticles can be deposited within the column. These deposits may be mechanically unstable, leading to irregular transport behavior. In the third study, the relationship between aggregation and iron oxyhydroxide phase transformations is explored. Previous researchers have found that akaganeite (beta-FeOOH) nanoparticles transform to create hematite (?-Fe2 O3) nano-spindles in response to hydrothermal aging, but the mechanism of transformation is unknown. Some researchers have proposed a process based on the aggregation of hematite precursors, while others advocated for dissolution and re-precipitation mechanisms. In this study, the kinetics of the phase transformation from akaganeite to hematite is studied, and cryo-TEM is used to characterize the aggregate structures in the transforming suspension. The hematite spindles are shown to be nanoporous, while akaganeite nanoparticles display a tendency for oriented aggregation. Hematite spindles are frequently found in intimate contact with akaganeite nanoparticle aggregates during the process of phase transformation, suggesting a model for phase transformation in which the dehydration of akaganeite to form hematite is enhanced by aggregation. In the final study, the nucleation and growth of akaganeite nanoparticles from acidic (pH 1.5-3) FeCl3 solutions is tracked with in situ small angle x-ray scattering (SAXS). The hydrothermal precipitation process studied can generate highly monodisperse particles, whose size, shape, and nucleation rate can be tuned by varying solution saturation and temperature. Classical nucleation modeling is applied to determine new values for the interfacial energy of ferric oxyhydroxide clusters. The interfacial energy (interfacial tension) of the nucleus is shown to be pH dependent and ranges from 0.06 to 0.12 J/m2 within the

  8. Zn(II) and Cu(II) adsorption and retention onto iron oxyhydroxide nanoparticles: effects of particle aggregation and salinity

    PubMed Central

    2014-01-01

    Background Iron oxyhydroxides are commonly found in natural aqueous systems as nanoscale particles, where they can act as effective sorbents for dissolved metals due to their natural surface reactivity, small size and high surface area. These properties make nanoscale iron oxyhydroxides a relevant option for the remediation of water supplies contaminated with dissolved metals. However, natural geochemical processes, such as changes in ionic strength, pH, and temperature, can cause these particles to aggregate, thus affecting their sorption capabilities and remediation potential. Other environmental parameters such as increasing salinity may also impact metal retention, e.g. when particles are transported from freshwater to seawater. Results After using synthetic iron oxyhydroxide nanoparticles and nanoparticle aggregates in batch Zn(II) adsorption experiments, the addition of increasing concentrations of chloride (from 0.1 M to 0.6 M) appears to initially reduce Zn(II) retention, likely due to the desorption of outer-sphere zinc surface complexes and subsequent formation of aqueous Zn-Cl complexes, before then promoting Zn(II) retention, possibly through the formation of ternary surface complexes (supported by EXAFS spectroscopy) which stabilize zinc on the surface of the nanoparticles/aggregates. In batch Cu(II) adsorption experiments, Cu(II) retention reaches a maximum at 0.4 M chloride. Copper-chloride surface complexes are not indicated by EXAFS spectroscopy, but there is an increase in the formation of stable aqueous copper-chloride complexes as chloride concentration rises (with CuCl+ becoming dominant in solution at ~0.5 M chloride) that would potentially inhibit further sorption or encourage desorption. Instead, the presence of bidentate edge-sharing and monodentate corner-sharing complexes is supported by EXAFS spectroscopy. Increasing chloride concentration has more of an impact on zinc retention than the mechanism of nanoparticle aggregation, whereas aggregation condition is a stronger determinant of copper retention. Conclusions Based on these model uptake/retention studies, iron oxyhydroxide nanoparticles show potential as a strategy to remediate zinc-contaminated waters that migrate towards the ocean. Copper retention, in contrast, appears to be optimized at an intermediate salinity consistent with brackish water, and therefore may release considerable fractions of retained copper at higher (e.g. seawater) salinity levels. PMID:24843322

  9. Soil organic matter mineralization in frozen soils

    NASA Astrophysics Data System (ADS)

    Harrysson Drotz, S.; Sparrman, T.; Schleucher, J.; Nilsson, M.; quist, M. G.

    2009-12-01

    Boreal forest soils are frozen for a large part of the year and soil organic matter mineralization during this period has been shown to significantly influence the C balance of boreal forest ecosystems. Mineralization proceeds through heterotrophic microbial activity, but the understanding of the environmental controls regulating soil organic matter mineralization under frozen conditions is poor. Through a series of investigations we have addressed this issue in order to elucidate to what extent a range of environmental factors control mineralization processes in frozen soils and also the microbial communities potential to oxidize organic substrates and grow under such conditions. The unfrozen water content in the frozen soils was shown to be an integral control on the temperature response of biogenic CO2 production across the freezing point of bulk soil water. We found that osmotic potential was an important contributor to the total water potential and, hence, the unfrozen water content of frozen soil. From being low and negligible in an unfrozen soil, the osmotic potential was found to contribute up to 70% of the total water potential in frozen soil, greatly influencing the volume of liquid water. The specific factors of how soil organic matter composition affected the unfrozen water content and CO2 production of frozen soil were studied by CP-MAS NMR. We concluded that abundance of aromatics and recalcitrant compounds showed a significant positive correlation with unfrozen water content and these were also the major soil organic fractions that similarly correlated with the microbial CO2 production of the frozen soils. Thus, the hierarchy of environmental factors controlling SOM mineralization changes as soils freeze and environmental controls elucidated from studies of unfrozen systems can not be added on frozen conditions. We have also investigated the potential activity of soil microbial communities under frozen conditions in order to elucidate temperature limitations on soil organic matter mineralization. The carbon mineralization was found to proceed down to -4C and the soil microbial communities were growing at this temperature. At -9C, the carbon mineralization was insignificant. 13C NMR revealed that the soil microorganisms were able to produce ethylene glycol (anti-freeze medium) under frozen conditions (-4C). The production of ethylene glycol coincided with an increase in CO2 production that took place after a lag-phase of ca. 41 days. 13C NMR also confirmed that soil microbial anabolic processes continued under frozen conditions. At -4C, 23% of the used substrate was respired as CO2 and 77% were converted and assimilated by the organisms as e.g. lipids and polysaccharides. This is contradicting to earlier studies that suggest that mainly processes yielding CO2 occurs in soils at <0C.

  10. Rapid sedimentation of iron oxyhydroxides in an active hydrothermal shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

    NASA Astrophysics Data System (ADS)

    Kiyokawa, Shoichi; Ueshiba, Takuya

    2015-04-01

    Hydrothermal activity is common in the fishing port of Nagahama Bay, a small semi-enclosed bay located on the southwest coast of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan). The bay contains red-brown iron oxyhydroxides and thick deposits of sediment. In this work, the high concentration and sedimentation rates of oxyhydroxide in this bay were studied and the sedimentary history was reconstructed. Since dredging work in 1998, a thickness of ~ 1.0-1.5 m of iron oxyhydroxide-rich sediments has accumulated on the floor of the bay. To estimate the volume of iron oxyhydroxide sediments and the amount discharged from hydrothermal vents, sediment traps were operated for several years and 13 sedimentary core samples were collected to reconstruct the 10-year sedimentary history of Nagahama Bay. To confirm the timing of sedimentary events, the core data were compared with meteorological records obtained on the island, and the ages of characteristic key beds were thus identified. The sedimentation rate of iron oxyhydroxide mud was calculated, after correcting for sediment input from other sources. The sediments in the 13 cores from Nagahama Bay consist mainly of iron oxyhydroxide mud, three thick tephra beds, and a topmost thick sandy mud bed. Heavy rainfall events in 2000, 2001, 2002, and 2004-2005 coincide with tephra beds, which were reworked from Iwo-Dake ash deposits to form tephra-rich sediment. Strong typhoon events with gigantic waves transported outer-ocean-floor sediments and supplied quartz, cristobalite, tridymite, and albite sands to Nagahama Bay. These materials were redeposited together with bay sediments as the sandy mud bed. Based on the results from the sediment traps and cores, it is estimated that the iron oxyhydroxide mud accumulated in the bay at the relatively rapid rate of 33.3 cm/year (from traps) and 2.8-4.9 cm/year (from cores). The pore water contents within the sediment trap and core sediments are 73%-82% and 47%-67%, respectively. The estimated production of iron oxyhydroxide for the whole fishing port from trap cores is 142.7-253.3 t/year/5000 m2. From sediment cores, however, the accumulation of iron oxyhydroxide sediments on the sea floor is 39-95 t/year/5000 m2. This finding indicates that the remaining 63%-73% of iron was transported out to sea from Nagahama Bay. Even with a high rate of iron oxyhydroxide production, the sedimentation rate of iron oxyhydroxides in the bay is considerably higher than that observed in modern deep-ocean sediments. This example of rapid and abundant oxyhydroxide sedimentation might provide a modern analog for the formation of iron deposits in the geological record, such as ironstones and banded iron formations.

  11. 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.

  12. The soils of Mars

    NASA Technical Reports Server (NTRS)

    Banin, A.

    1988-01-01

    A mineralogical model for the Mars fine soil that includes as major components smectite clays absorbed and coated with amorphous iron oxyhydroxides and perhaps mixed with small amounts of better-crystalized iron oxides as separate phases is proposed. Also present as accessory minerals are sulfate minerals such as kieserite (MgSO4.H2O) and/or anhydrite (CaSO4), rutile (TiO2), and maghemite (Fe2O3) or magnetite (Fe3O4), the last two as magnetic components. Carbonates may be present at low concentrations only (less than 1 to 2 pct). However, a prime question to be addressed by a Mars Sample Return Mission shall be related to the mineralogical composition of the soil, and its spatial variability.

  13. Ecophysiology of Zetaproteobacteria Associated with Shallow Hydrothermal Iron-Oxyhydroxide Deposits in Nagahama Bay of Satsuma Iwo-Jima, Japan.

    PubMed

    Hoshino, Tatsuhiko; Kuratomi, Takashi; Morono, Yuki; Hori, Tomoyuki; Oiwane, Hisashi; Kiyokawa, Shoichi; Inagaki, Fumio

    2015-01-01

    Previous studies of microbial communities in deep-sea hydrothermal ferric deposits have demonstrated that members of Zetaproteobacteria play significant ecological roles in biogeochemical iron-cycling. However, the ecophysiological characteristics and interaction between other microbial members in the habitat still remain largely unknown. In this study, we investigated microbial communities in a core sample obtained from shallow hydrothermal iron-oxyhydroxide deposits at Nagahama Bay of Satsuma Iwo-Jima, Japan. Scanning electron microscopic observation showed numerous helical stalk structures, suggesting the occurrence of iron-oxidizing bacteria. Analysis of 16S rRNA gene sequences indicated the co-occurrence of iron-oxidizing Zetaproteobacteria and iron-reducing bacteria such as the genera Deferrisoma and Desulfobulbus with strong correlations on the sequence abundance. CARD-FISH indicated that the numbers of Zetaproteobacteria were not always consistent to the frequency of stalk structures. In the stalk-abundant layers with relatively small numbers of Zetaproteobacteria cells, accumulation of polyphosphate was observed inside Zetaproteobacteria cells, whereas no polyphosphate grains were observed in the topmost layers with fewer stalks and abundant Zetaproteobacteria cells. These results suggest that Zetaproteobacteria store intracellular polyphosphates during active iron oxidation that contributes to the mineralogical growth and biogeochemical iron cycling. PMID:26793184

  14. Iron oxyhydroxide nanorods with high electrochemical reactivity as a sensitive and rapid determination platform for 4-chlorophenol.

    PubMed

    Zhang, Yuanyuan; Cheng, Qin; Zheng, Meng; Liu, Xin; Wu, Kangbing

    2016-04-15

    Iron oxyhydroxide (FeOOH) nanorods were prepared through solvothermal reaction, and characterized using Raman spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and scanning electron microscopy. Thereafter, the prepared FeOOH nanorods were used as sensing material to construct a novel detection platform for 4-chlorophenol (4-CP). The electrochemical behaviors of 4-CP were studied, and the oxidation peak currents increased greatly on the surface of FeOOH nanorods. The signal enhancement mechanism was studied for 4-CP, and it was found that the prepared FeOOH nanorods remarkably improved the electron transfer ability and surface adsorption efficiency of 4-CP. The influences of pH value, amount of FeOOH nanorods and accumulation time were examined. As a result, a highly-sensitive electrochemical method was developed for the rapid determination of 4-CP. The linear range was from 10 to 500nM, and the detection limit was 3.2nM. It was used in different water samples, and the results consisted with the values that obtained by high-performance liquid chromatography. PMID:26775105

  15. Ecophysiology of Zetaproteobacteria Associated with Shallow Hydrothermal Iron-Oxyhydroxide Deposits in Nagahama Bay of Satsuma Iwo-Jima, Japan

    PubMed Central

    Hoshino, Tatsuhiko; Kuratomi, Takashi; Morono, Yuki; Hori, Tomoyuki; Oiwane, Hisashi; Kiyokawa, Shoichi; Inagaki, Fumio

    2016-01-01

    Previous studies of microbial communities in deep-sea hydrothermal ferric deposits have demonstrated that members of Zetaproteobacteria play significant ecological roles in biogeochemical iron-cycling. However, the ecophysiological characteristics and interaction between other microbial members in the habitat still remain largely unknown. In this study, we investigated microbial communities in a core sample obtained from shallow hydrothermal iron-oxyhydroxide deposits at Nagahama Bay of Satsuma Iwo-Jima, Japan. Scanning electron microscopic observation showed numerous helical stalk structures, suggesting the occurrence of iron-oxidizing bacteria. Analysis of 16S rRNA gene sequences indicated the co-occurrence of iron-oxidizing Zetaproteobacteria and iron-reducing bacteria such as the genera Deferrisoma and Desulfobulbus with strong correlations on the sequence abundance. CARD-FISH indicated that the numbers of Zetaproteobacteria were not always consistent to the frequency of stalk structures. In the stalk-abundant layers with relatively small numbers of Zetaproteobacteria cells, accumulation of polyphosphate was observed inside Zetaproteobacteria cells, whereas no polyphosphate grains were observed in the topmost layers with fewer stalks and abundant Zetaproteobacteria cells. These results suggest that Zetaproteobacteria store intracellular polyphosphates during active iron oxidation that contributes to the mineralogical growth and biogeochemical iron cycling. PMID:26793184

  16. Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: II. Temperature and time

    NASA Astrophysics Data System (ADS)

    Stegemeier, J. P.; Reinsch, B. C.; Lentini, C. J.; Dale, J. G.; Kim, C. S.

    2015-01-01

    The aggregation and growth of nanosized particles can greatly impact their capacity to sorb and retain dissolved metals, thus affecting metal fate and transport in contaminated systems. Aqueous suspensions of synthesized nanoscale iron oxyhydroxides were exposed to dissolved Zn(II) or Cu(II) and aged at room temperature (∼20 °C), 50 °C, and 75 °C for timeframes ranging from 0 to 96 h before sorbed metal ions were desorbed by lowering the suspension pH. Atomic absorption spectroscopic analysis of supernatants both before and after the desorption step determined how temperature and time affect macroscopic metal uptake and retention capacities. Extended X-ray absorption fine structure (EXAFS) spectroscopy analysis described the local binding environment of the sorbed/retained metals on the solid phase. With increasing aging temperature and time, the initial ∼5-nm oblong nanoparticles formed dense aggregates, lost reactive surface area, and retained progressively larger fractions of the initially-introduced Zn(II) and Cu(II) following the desorption step, with the copper species inhibiting the oriented aggregation of the nanoparticles into nanorods. Based on EXAFS analysis, the speciation of the sorbed metal species evolves with increasing time and temperature from surface-sorbed metal ions, which readily desorb and return to solution, to more strongly-bound, structurally-incorporated metal ions. These retained metals appear to associate intimately with the nanoparticle aggregates by substituting for iron in the nanoparticle lattice or by binding within nanoparticle aggregate pore spaces.

  17. Phosphate binders for the treatment of chronic kidney disease: role of iron oxyhydroxide

    PubMed Central

    Cernaro, Valeria; Santoro, Domenico; Lacquaniti, Antonio; Costantino, Giuseppe; Visconti, Luca; Buemi, Antoine; Buemi, Michele

    2016-01-01

    Chronic kidney disease-mineral bone disorder is frequent in patients with renal failure. It is characterized by abnormalities in mineral and bone metabolism with resulting hyperphosphatemia, low serum vitamin D, secondary hyperparathyroidism, altered bone morphology and strength, higher risk of bone fractures, and development of vascular or other soft tissue calcifications. Besides the recommendation to reduce phosphorus dietary intake, many drugs are currently available for the treatment of calcium/phosphate imbalance. Among them, phosphate binders represent a milestone. Calcium-based binders (calcium carbonate, calcium acetate) are effective in lowering serum phosphate, but their use has been associated with an increased risk of hypercalcemia and calcifications. Calcium-free binders (sevelamer hydrochloride, sevelamer carbonate, and lanthanum carbonate) are equally or slightly less effective than calcium-containing compounds. They would not induce an increase in calcium levels but may have relevant side effects, including gastrointestinal symptoms for sevelamer and risk of tissue accumulation for lanthanum. Accordingly, new phosphate binders are under investigation and some of them have already been approved. A promising option is sucroferric oxyhydroxide (Velphoro®, PA21), an iron-based phosphate binder consisting of a mixture of polynuclear iron(III)-oxyhydroxide, sucrose, and starches. The present review is focused on pharmacology, mode of action, and pharmacokinetics of sucroferric oxyhydroxide, with a discussion on comparative efficacy, safety, and tolerability studies of this drug in chronic kidney disease and patient perspectives such as quality of life, satisfaction, and acceptability. Sucroferric oxyhydroxide has proven to be as effective as sevelamer in reducing phosphatemia with a similar safety profile and lower pill burden. Experimental and clinical studies have documented a minimal percentage of iron absorption without inducing toxicity. In conclusion, the overall benefit–risk balance of sucroferric oxyhydroxide is deemed to be positive, and this new drug may therefore represent a good alternative to traditional phosphate binders for the treatment of hyperphosphatemia in dialysis patients. PMID:26893577

  18. Phosphate binders for the treatment of chronic kidney disease: role of iron oxyhydroxide.

    PubMed

    Cernaro, Valeria; Santoro, Domenico; Lacquaniti, Antonio; Costantino, Giuseppe; Visconti, Luca; Buemi, Antoine; Buemi, Michele

    2016-01-01

    Chronic kidney disease-mineral bone disorder is frequent in patients with renal failure. It is characterized by abnormalities in mineral and bone metabolism with resulting hyperphosphatemia, low serum vitamin D, secondary hyperparathyroidism, altered bone morphology and strength, higher risk of bone fractures, and development of vascular or other soft tissue calcifications. Besides the recommendation to reduce phosphorus dietary intake, many drugs are currently available for the treatment of calcium/phosphate imbalance. Among them, phosphate binders represent a milestone. Calcium-based binders (calcium carbonate, calcium acetate) are effective in lowering serum phosphate, but their use has been associated with an increased risk of hypercalcemia and calcifications. Calcium-free binders (sevelamer hydrochloride, sevelamer carbonate, and lanthanum carbonate) are equally or slightly less effective than calcium-containing compounds. They would not induce an increase in calcium levels but may have relevant side effects, including gastrointestinal symptoms for sevelamer and risk of tissue accumulation for lanthanum. Accordingly, new phosphate binders are under investigation and some of them have already been approved. A promising option is sucroferric oxyhydroxide (Velphoro(), PA21), an iron-based phosphate binder consisting of a mixture of polynuclear iron(III)-oxyhydroxide, sucrose, and starches. The present review is focused on pharmacology, mode of action, and pharmacokinetics of sucroferric oxyhydroxide, with a discussion on comparative efficacy, safety, and tolerability studies of this drug in chronic kidney disease and patient perspectives such as quality of life, satisfaction, and acceptability. Sucroferric oxyhydroxide has proven to be as effective as sevelamer in reducing phosphatemia with a similar safety profile and lower pill burden. Experimental and clinical studies have documented a minimal percentage of iron absorption without inducing toxicity. In conclusion, the overall benefit-risk balance of sucroferric oxyhydroxide is deemed to be positive, and this new drug may therefore represent a good alternative to traditional phosphate binders for the treatment of hyperphosphatemia in dialysis patients. PMID:26893577

  19. Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

    PubMed

    Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

    2014-07-15

    Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO. PMID:24910911

  20. Transformations of mercury, iron, and sulfur during the reductive dissolution of iron oxyhydroxide by sulfide

    NASA Astrophysics Data System (ADS)

    Slowey, Aaron J.; Brown, Gordon E.

    2007-02-01

    Methylmercury can accumulate in fish to concentrations unhealthy for humans and other predatory mammals. Most sources of mercury (Hg) emit inorganic species to the environment. Therefore, ecological harm occurs when inorganic Hg is converted to methylmercury. Sulfate- and iron-reducing bacteria (SRB and FeRB) methylate Hg, but the effects of processes involving oxidized and reduced forms of sulfur and iron on the reactivity of Hg, including the propensity of inorganic Hg to be methylated, are poorly understood. Under abiotic conditions, using a laboratory flow reactor, bisulfide (HS -) was added at 40 to 250 μM h -1 to 5 g L -1 goethite (α-FeOOH) suspensions to which Hg(II) was adsorbed (30-100 nmol m -2) at pH 7.5. Dissolved Hg initially decreased from 10 3 or 10 4 nM (depending on initial conditions) to 10 -1 nM, during which the concentration of Hg(II) adsorbed to goethite decreased by 80% and metacinnabar (β-HgS (s)) formed, based on identification using Hg L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. The apparent coordination of oxygens surrounding Hg(II), measured with EXAFS spectroscopy, increased during one flow experiment, suggesting desorption of monodentate-bound Hg(II) while bidentate-bound Hg(II) persisted on the goethite surface. Further sulfidation increased dissolved Hg concentrations by one to two orders of magnitude (0.5 to 10 nM or 30 nM), suggesting that byproducts of bisulfide oxidation and Fe(III) reduction, primarily polysulfide and potentially Fe(II), enhanced the dissolution of β-HgS (s) and/or desorption of Hg(II). Rapid accumulation of Fe(II) in the solid phase (up to 40 μmol g -1) coincided with faster elevation of dissolved Hg concentrations. Fe(II) served as a proxy for elemental sulfur [S(0)], as S(0) was the dominant bisulfide oxidation product coupled to Fe(III) reduction, based on sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy. In one experiment, dissolved Hg concentrations tracked those of all sulfide species [S(-II)]. These results suggest that S(-II) reacted with S(0) to form polysulfide, which then caused the dissolution of β-HgS (s). A secondary Fe-bearing phase resembling poorly formed green rust was observed in sulfidized solids with scanning electron microscopy, although there was no clear evidence that either surface-bound or mineralized Fe(II) strongly affected Hg speciation. Examination of interrelated processes involving S(-II) and Fe(III) revealed new modes of Hg solubilization previously not considered in Hg reactivity models.

  1. Synthesis of iron oxyhydroxide-coated rice straw (IOC-RS) and its application in arsenic(V) removal from water.

    PubMed

    Ouédraogo, Igor W K; Pehlivan, Erol; Tran, Hien T; Bonzi-Coulibaly, Yvonne L; Zachmann, Dieter; Bahadir, Müfit

    2015-09-01

    Because of the recognition that arsenic (As) at low concentrations in drinking water causes severe health effects, the technologies of As removal have become increasingly important. In this study, a simplified and effective method was used to immobilize iron oxyhydroxide onto a pretreated naturally occurring rice straw (RS). The modified RS adsorbent was characterized, using scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analyzer, and surface area analyzer. Experimental batch data of As(V) adsorption were modeled by the isotherms and kinetics models. Although all isotherms, the Langmuir model fitted the equilibrium data better than Freundlich and Dubinin-Radushkevich models and confirmed the surface homogeneity of adsorbent. The iron oxyhydroxide-coated rice straw (IOC-RS) was found to be effective for the removal of As(V) with 98.5% sorption efficiency at a concentration of <50 mg/L of As(V) solution, and thus maximum uptake capacity is ∼22 and 20 mg As(V)/g of IOC-RS at pH 4 and 6, respectively. The present study might provide new avenues to achieve the As concentrations required for drinking water recommended by the World Health Organization. PMID:26322758

  2. Neptunium and Plutonium Sorption to Snake River Plain, Idaho Soil

    SciTech Connect

    Mincher, Bruce Jay; Fox, Robert Vincent; Cooper, David Craig; Groenewold, Gary Steven

    2003-07-01

    The behavior of Np and Pu on soil collected from the subsurface disposal area at the Idaho National Engineering and Environmental Laboratory was investigated by performing short-duration, sorption experiments to measure sorption isotherms. Neptunium sorption can be described with a Freundlich isotherm; however, Pu sorption can only be described in this fashion as a conservative estimate of minimum sorption. Geochemical modeling predictions suggest that initial sorption of Np is controlled predominantly by surface complexation on clay minerals, while Pu is controlled by a competition between complexation with iron oxyhydroxides and the precipitation of hydrolysis products. Longer-term sorption is governed by the transformation of these species to oxide minerals. Solution ionic strength and carbonate alkalinity did not significantly affect Np or Pu soil sorption.

  3. 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.

  4. Mineralization of cellulose in frozen boreal soils

    NASA Astrophysics Data System (ADS)

    Oquist, Mats G.; Segura, Javier; Sparrman, Tobias; Nilsson, Mats; Schleucher, Jurgen

    2015-04-01

    Soils of high-latitude ecosystems store a large fraction of the global soil carbon. In boreal forests, the microbial mineralization of soil organic matter (SOM) during winter can affect the ecosystems net carbon balance. Recent research has shown that microorganisms in the organic surface layer of boreal forest soil can mineralize and grow on simple, soluble monomeric substrates under frozen conditions. However, any substantial impacts of microbial activity in frozen soils on long-term soil carbon balances ultimately depends on whether soil microorganisms can utilize and grow the more complex, polymeric constituents of SOM. In order to evaluate the potential for soil microorganisms to metabolize carbon polymers at low temperatures, we incubated boreal forest soil samples amended with [13C]-cellulose and studied the microbial catabolic and anabolic utilization of the substrate under frozen and unfrozen conditions (-4 and +4C). Freezing of the soil markedly reduced microbial utilization of the cellulose. The [13C]-CO2 production rate in the samples at +4C were 0.52 mg CO2 SOM -1 day-1 while rates in the frozen samples (-4C) were 0.01 mg CO2 SOM -1 day-1. However, newly synthetized [13C]-enriched cell membrane lipids, PLFAs, were detected in soil samples incubated both above and below freezing, confirming that cellulose can sustain also anabolic activity of the microbial populations under frozen conditions. The reduced metabolic rates induced by freezing indicate constraints on exoenzymatic activity, as well as substrate diffusion rates that we can attribute to reduced liquid water content of the frozen soil. We conclude that the microbial population in boreal forest soil has the capacity to metabolize, and grow, on polymeric substrates at temperatures below zero, which involves maintaining exoenzymatic activity in frozen soils. This capacity manifests the importance of SOM mineralization during the winter season and its importance for the net carbon balance of soils of high-latitude ecosystems.

  5. 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.

  6. Soil Microbial Mineralization of Cellulose in Frozen Soils

    NASA Astrophysics Data System (ADS)

    Segura, J.; Haei, M.; Sparrman, T.; Nilsson, M. B.; Schleucher, J.; Oquist, M. G.

    2014-12-01

    Soils of high-latitude ecosystems store a large fraction of the global soil carbon pool. In boreal forests, the mineralization of soil organic matter (SOM) during winter by soil heterotrophic activity can affect the ecosystems net carbon balance. Recent research has shown that microorganisms in the organic surface layer of boreal forest soil can mineralize and grow on simple, monomeric substrates under frozen conditions. However, any substantial impacts of microbial activity in frozen soils on long-term soil carbon balances depend on whether soil microorganisms can utilize the more complex, polymeric substrates in SOM. In order to evaluate the potential for soil microorganisms to metabolize carbon polymers at low temperatures, we incubated boreal forest soil samples amended with [13C]-cellulose and studied the microbial catabolic and anabolic utilization of the substrate under frozen and unfrozen conditions (-4 and +4C). The [13C]-CO2 production rate in the samples at +4C were 0.524 mg CO2 SOM -1 day-1 while rates in the frozen samples (-4C) were 0.008 mg CO2 SOM -1 day-1. Thus, freezing of the soil markedly reduced microbial utilization of the cellulose. However, newly synthetized [13C]-enriched cell membrane lipids, PLFAs, were detected in soil samples incubated both above and below freezing, confirming microbial growth also in the frozen soil matrix. The reduced metabolic rates induced by freezing indicate constraints on exoenzymatic activity, as well as substrate diffusion rates that we can attribute to reduced liquid water content of the frozen soil. We conclude that the microbial population in boreal forest soil has the capacity to metabolize, and grow, on polymeric substrates at temperatures below zero. This also involves maintaining exoenzymatic activity in frozen soils. This capacity manifests the importance of SOM mineralization during the winter season and its importance for the net carbon balance of soils of high-latitude ecosystems.

  7. Soil pore structure and substrate C mineralization

    NASA Astrophysics Data System (ADS)

    Sleutel, Steven; Maenhout, Peter; Vanhoorebeke, Luc; Cnudde, Veerle; De Neve, Stefaan

    2014-05-01

    Our aim was to investigate the complex interactions between soil pore structure, soil biota and decomposition of added OM substrates. We report on a lab incubation experiment in which CO2 respiration from soil cores was monitored (headspace GC analysis) and an X-ray CT approach yielded soil pore size distributions. Such combined use of X-ray CT with soil incubation studies was obstructed, until now, by many practical constraints such as CT-volume quality, limited resolution, scanning time and complex soil pore network quantification, which have largely been overcome in this study. We incubated a sandy loam soil (with application of ground grass or sawdust) in 18 small aluminium rings (Ø 1 cm, h 1 cm). Bulk density was adjusted to 1.1 or 1.3 Mg m-3 (compaction) and 6 rings were filled at a coarser Coarse Sand:Fine Sand:Silt+Clay ratio. While compaction induced a strong reduction in the cumulative C mineralization for both grass and sawdust substrates, artificial change to a coarser soil texture only reduced net C mineralization from the added sawdust. There thus appears to be a strong interaction effect between soil pore structure and substrate type on substrate decomposition. Correlation coefficients between the C mineralization rates and volumes of 7 pore size classes (from the X-ray CT data) also showed an increasing positive correlation with increasing pore size. Since any particulate organic matter initially present in the soil was removed prior to the experiment (sieving, ashing the >53µm fraction and recombining with the <53µm fraction), the added OM can be localized by means of X-ray CT. Through on-going image analysis the surrounding porosity of the added grass or sawdust particles is being quantified to further study the interaction between the soil pore structure and substrate decomposition.

  8. Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

    NASA Astrophysics Data System (ADS)

    Dale, J. G.; Stegemeier, J. P.; Kim, C. S.

    2015-01-01

    The capacity of nanosized particles to adsorb and sequester dissolved metals can be significantly impacted by the mechanism and extent of aggregation the particles have undergone, which in turn can affect the long-term fate and transport of potentially toxic metals in natural aqueous systems. Suspensions of monodisperse nanoscale iron oxyhydroxides were synthesized and subjected to increased pH (pH 8.0, 10.0) or ionic strength (0.1, 1.0 M NaNO3) conditions to induce various states of aggregation prior to conducting macroscopic adsorption/desorption experiments with dissolved Cu(II) or Zn(II). The metal adsorption and retention capacities of the nanoparticle aggregates were compared to one another and to non-aggregated control nanoparticles, while the mode(s) of metal sorption to the nanoparticle surfaces were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. With increasing aggregation by both pH and ionic strength, the proportion of introduced zinc adsorbed to the iron oxyhydroxide nanoparticles progressively decreased from 45% on the monodispersed control particles to as low as 16% on the aggregates, while the proportion of introduced zinc retained upon desorption (obtained by lowering the suspension pH) increased from 7% on the control particles to as much as 17% on the aggregated particles. Copper exhibited a subtler trend of only slightly declining uptake (from 43% to 36%) and retention (from 35% to 30%) with increasing aggregation state. EXAFS analysis was consistent with the macroscopic results, showing relatively little change in Cu speciation between samples analyzed before and after the desorption step but significant increases in Zn-Fe interatomic distances and coordination numbers after desorption. This suggests the presence of both strongly- and weakly-bound zinc ions; the latter are likely affiliated with less stable, more distorted surface sorption sites and are thus more readily desorbed, resulting in the retention of zinc that is bound to more stable, less-distorted sorption sites. For both metals, inner-sphere bidentate sorption appears to dominate the sorption process to the nanoparticle aggregates, with potential structural incorporation into the aggregates themselves.

  9. Recycling Ni from Contaminated and Mineralized Soils.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rare plant species accumulate potentially valuable concentrations of some metals. Alyssum murale readily accumulates over 2% Ni in aboveground dry matter when grown on Ni-mineralized serpentine soils in Oregon, allowing production of “hay” biomass with at least 400 kg Ni ha-1 with low levels of fer...

  10. Mineralization of metsulfuron-methyl in Chinese paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory study was conducted to investigate the mineralization of metsulfuron-methyl (MSM) in paddy soils in response to soil moisture, temperature and soil properties. The results indicated that MSM mineralization was relatively limited in the paddy soils when soil temperature was low. Only 2.2...

  11. Mineral Soils as Carriers for Rhizobium Inoculants

    PubMed Central

    Chao, W.-L.; Alexander, Martin

    1984-01-01

    Mineral soil-based inoculants of Rhizobium meliloti and Rhizobium phaseoli survived better at 4C than at higher temperatures, but ca. 15% of the cells were viable at 37C after 27 days. Soil-based inoculants of R. meliloti, R. phaseoli, Rhizobium japonicum, and a cowpea Rhizobium sp. applied to seeds of their host legumes also survived better at low temperatures, but the percent survival of such inoculants was higher than peat-based inoculants at 35C. Survival of R. phaseoli, R. japonicum, and cowpea rhizobia was not markedly improved when the cells were suspended in sugar solutions before drying them in soil. Nodulation was abundant on Phaseolus vulgaris derived from seeds that had been coated with a soil-based inoculant and stored for 165 days at 25C. The increase in yield and nitrogen content of Phaseolus angularis grown in the greenhouse was the same with soil-and peat-based inoculants. We suggest that certain mineral soils can be useful and readily available carriers for legume inoculants containing desiccation-resistant Rhizobium strains. PMID:16346460

  12. Pentachlorophenol mineralization in an immobilized soil bioreactor

    SciTech Connect

    Karamanev, D.; Chavarie, C.; Samson, R.

    1996-12-31

    The biological degradation of pentachlorophenol (PCP) was conducted in a new type of reactor-the immobilized soil bioreactor. In this bioreactor soil particles having natural microbial activity in degrading the target pollutant are entrapped into a solid membrane with a large pore size distribution. The resulting {open_quotes}immobilized soil{close_quotes} system can be easily supplied with dissolved mineral salts, oxygen and target pollutant and as a result an active microbial consortium will be quickly established. This consortium is later used for treatment of aqueous solutions of the pollutant, for instance, contaminated ground water. We have studied the process of PCP biodegradation in both batch and continuous regime. our results showed that the volumetric effectiveness of the process of PCP mineralization in the immobilized soil bioreactor is between 7 and 4000 times higher than results reported in the literature. It has been found that both chlorine and carbon atoms of PCP are at least 99% mineralized. 7 refs., 4 figs., 1 tab.

  13. Humic acid facilitates the transport of ARS-labeled hydroxyapatite nanoparticles in iron oxyhydroxide-coated sand

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydroxyapatite nanoparticles (nHAP) have been widely used to remediate soil and wastewater contaminated with metals and radionuclides. However, our understanding of nHAP transport and fate is limited in natural environments that exhibit significant variability in solid and solution chemistry. The tr...

  14. Poliovirus Adsorption by 34 Minerals and Soils

    PubMed Central

    Moore, Rebecca S.; Taylor, Dene H.; Sturman, Lawrence S.; Reddy, Michael M.; Fuhs, G. Wolfgang

    1981-01-01

    The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl2 and 1.25 mM NaHCO3 at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 106 plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride. PMID:6274259

  15. The nanophase iron mineral(s) in Mars soil

    NASA Technical Reports Server (NTRS)

    Banin, A.; Ben-Shlomo, T.; Margulies, L.; Blake, D. F.; Mancinelli, R. L.; Gehring, A. U.

    1993-01-01

    A series of surface-modified clays containing nanophase (np) iron oxide/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these "Mars-soil analogs" were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging, specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The clay acted as an effective matrix, both chemically and sterically, preventing the major part of the synthesized iron oxides from ripening, i.e., growing and developing larger crystals. The precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1-10 nm, having large specific surface area. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxy mineral such as "green rust," or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable maghemite (gamma-Fe2O3) by mild heat treatment and then to nanophase hematite (alpha-Fe2O3) by extensive heat treatment. After mild heating, the iron-enriched clay became slightly magnetic, to the extent that it adheres to a hand-held magnet, as was observed with Mars soil. The chemical reactivity of the iron-enriched clays strongly resembles, and offers a plausible mechanism for, the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxides and silicate phase surfaces. The reflectance spectrum of the clay-iron preparations in the visible range is generally similar to the reflectance curves of bright regions on Mars. This strengthens the evidence for the predominance of nanophase iron oxides/oxyhydroxides in Mars soil. The mode of formation of these nanophase iron oxides on Mars is still unknown. It is puzzling that despite the long period of time since aqueous weathering took place on Mars, they have not developed from their transitory stage to well-crystallized end-members. The possibility is suggested that these phases represent a continuously on-going, extremely slow weathering process.

  16. The nanophase iron mineral(s) in Mars soil.

    PubMed

    Banin, A; Ben-Shlomo, T; Margulies, L; Blake, D F; Mancinelli, R L; Gehring, A U

    1993-11-25

    A series of surface-modified clays containing nanophase (np) iron oxide/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these "Mars-soil analogs" were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging, specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The clay acted as an effective matrix, both chemically and sterically, preventing the major part of the synthesized iron oxides from ripening, i.e., growing and developing larger crystals. The precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1-10 nm, having large specific surface area. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxy mineral such as "green rust," or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable maghemite (gamma-Fe2O3) by mild heat treatment and then to nanophase hematite (alpha-Fe2O3) by extensive heat treatment. After mild heating, the iron-enriched clay became slightly magnetic, to the extent that it adheres to a hand-held magnet, as was observed with Mars soil. The chemical reactivity of the iron-enriched clays strongly resembles, and offers a plausible mechanism for, the somewhat puzzling observations of the Viking biology experiments. Their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide/oxyhydroxides and silicate phase surfaces. The reflectance spectrum of the clay-iron preparations in the visible range is generally similar to the reflectance curves of bright regions on Mars. This strengthens the evidence for the predominance of nanophase iron oxides/oxyhydroxides in Mars soil. The mode of formation of these nanophase iron oxides on Mars is still unknown. It is puzzling that despite the long period of time since aqueous weathering took place on Mars, they have not developed from their transitory stage to well-crystallized end-members. The possibility is suggested that these phases represent a continuously on-going, extremely slow weathering process. PMID:11539182

  17. Potential anthropogenic mobilisation of mercury and arsenic from soils on mineralised rocks, Northland, New Zealand.

    PubMed

    Craw, D

    2005-02-01

    Eroded roots of hot spring systems in Northland, New Zealand consist of mineralised rocks containing sulfide minerals. Marcasite and cinnabar are the dominant sulfides with subordinate pyrite. Deep weathering and leached soil formation has occurred in a warm temperate to subtropical climate with up to 3 m/year rainfall. Decomposition of the iron sulfides in natural and anthropogenic rock exposures yields acid rock drainage with pH typically between 2 and 4, and locally down to pH 1. Soils and weathered rocks developed on basement greywacke have negligible acid neutralisation capacity. Natural rainforest soils have pH between 4 and 5 on unmineralised greywacke, and pH is as low as 3.5 in soils on mineralised rocks. Roads with aggregate made from mineralised rocks have pH near 3, and quarries from which the rock was extracted can have pH down to 1. Mineralised rocks are enriched in arsenic and mercury, both of which are environmentally available as solid solution impurities in iron sulfides and phosphate minerals. Base metals (Cu, Pb, Zn) are present at low levels in soils, at or below typical basement rock background. Decomposition of the iron sulfides releases the solid solution arsenic and mercury into the acid rock drainage solutions. Phosphate minerals release their impurities only under strongly acid conditions (pH<1). Arsenic and mercury are adsorbed on to iron oxyhydroxides in soils, concentrated in the C horizon, with up to 4000 ppm arsenic and 100 ppm mercury. Waters emanating from acid rock drainage areas have arsenic and mercury below drinking water limits. Leaching experiments and theoretical predictions indicate that both arsenic and mercury are least mobile in acid soils, at pH of c. 3-4. This optimum pH range for fixation of arsenic and mercury on iron oxyhydroxides in soils is similar to natural pH at the field site of this study. However, neutralisation of acid soils developed on mineralised rocks is likely to decrease adsorption and enhance mobility of arsenic and mercury. Hence, development of farmland by clearing forest and adding agricultural lime may mobilise arsenic and mercury from underlying soils on mineralised rocks. In addition, arsenic and mercury release into runoff water will be enhanced where sediment is washed off mineralised road aggregate (pH 3) on to farm land (pH>6). The naturally acid forest soils, or even lower pH of natural acid rock drainage, are the most desirable environmental conditions to restrict dissolution of arsenic and mercury from soils. This approach is only valid where mineralised soils have low base metal concentrations. PMID:15644268

  18. Eucalyptus obliqua seedling growth in organic vs. mineral soil horizons.

    PubMed

    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

  19. 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

  20. Study of mineralogical speciation of arsenic in soils using X ray microfluorescence and scanning electronic microscopy.

    PubMed

    Gmez-Parrales, Isidoro; Bellinfante, Nicols; Tejada, Manuel

    2011-05-15

    In this paper we studied the As content in natural contaminated soils, classified as Dystric Leptosol, Chromic Luvisol, Eutric Cambisol and Mollic Leptosol. In soil samples, sieved (<2mm), total As was determined by XRF and chemical speciation by sequential extraction. As-bearing minerals were concentrated from fine sand fraction of soil (200-20 ?m) using heavy liquid. In this fraction, mineralogical speciation was studied by X-ray microfluorescence, XRD with Gbbel mirror and SEM-BEI-EDX. Total As contents ranging from 61.00 to 131.00 mg kg(-1). The results of the sequential extraction showed that As was, mainly, in the residual fraction (52.51-98.76 mg kg(-1)) and in the fraction bound to iron oxyhydroxides (0-36.5 mg kg(-1)). Mapping of As with X-ray microfluorescence show strongly relationship between Fe and As. Iron (III) oxyhydroxides (FeOHs) (lepidocrocite and goethite), scorodite, angelellite, schultenite and dussertite were identified by XRD analysis as most likely mineral phases. The contents of As, Fe, Pb and Ba obtained with EDX-microprobe, confirmed the results of XRD. The results of sequential extraction and X-ray microfluorescence indicate that As is strongly bound to the soils because the identified As-bearing mineral phases are very stable at the pH conditions of studied soils. Consequently, a low mobility of As can be assumed in these soils. PMID:21482293

  1. 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.

  2. Sorption of copper, zinc and lead on soil mineral phases.

    PubMed

    Sipos, Pter; Nmeth, Tibor; Kis, Viktria Kovcs; Mohai, Ilona

    2008-09-01

    Soil mineral phases play a significant role in controlling heavy metal mobility in soils. The effective study of their relation needs the integrated use of several analytical methods. In this study, analytical electron microscopy analyses were combined with sequential chemical extractions on soils spiked with Cu, Zn and Pb. Our aims were to study the metal sorption capacity of soil mineral phases and the effect of presence of iron oxide and carbonate on this property of soil minerals. Copper and Pb were found to be characterized by higher and stronger sorption on the studied samples than Zn. Only the former two metals showed significant differences in their immobilized metal amounts on the studied samples and soil mineral particles. Highest metal amounts were sorbed on the swelling clay mineral particles (smectites and vermiculites), but iron-oxide phases may also have similar lead sorption capacity. Alkaline conditions due to the carbonate content of soils resulted both in increased sorption on the mineral particles for Cu and in enhanced role of precipitation for all the studied metals. On the other hand, the intimate association of phyllosilicates and iron resulted in significant increase in metal sorption capacity of the given particle. The results of sequential extractions could be successfully completed by the analytical electron microscopy analyses for studying the sorption capacity of discrete mineral particles. Their integrated use helps us in better understanding the heavy metal-mineral interactions in soils. PMID:18674797

  3. 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. ?-1,4- Glucosaminidase, chitinase, acid phosphatase, ?-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.

  4. In situ treatability of mineral oil in soils. Final report

    SciTech Connect

    Gauger, K.

    1998-06-01

    Mineral oil dielectric fluid (MODF) has replaced PCB oil as the insulating medium in electrical transformers. Although eliminating PCBs has reduced the environmental impact resulting from transformer leaks, soil contaminated with mineral oil still often requires remediation. This project presents the results of laboratory application of seven biological treatment regimes to soil contaminated with mineral oil. The results demonstrate the expected extent of mineral oil biodegradation, change in chemical composition of the mineral oil, rate of biodegradation, and key engineering requirements associated with the process.

  5. 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.

  6. Fractionation of Fe isotopes by soil microbes and organic acids

    USGS Publications Warehouse

    Brantley, Susan L.; Liermann, Laura; Bullen, Thomas D.

    2001-01-01

    Small natural variations in Fe isotopes have been attributed to biological cycling. However, without understanding the mechanism of fractionation, it is impossible to interpret such variations. Here we show that the ?56Fe of Fe dissolved from a silicate soil mineral by siderophore-producing bacteria is as much as 0.8% lighter than bulk Fe in the mineral. A smaller isotopic shift is observed for Fe released abiotically by two chelates, and the magnitude of the shift increases with affinity of the ligand for Fe, consistent with a kinetic isotope effect during hydrolysis of Fe at the mineral surface. Fe dissolved abiotically without chelates shows no isotopic shift. The ?56Fe of the exchange fraction on soil grains is also lighter by ~0.6%-1% than Fe from both hornblende and iron oxyhydroxides. The kinetic isotope effect is therefore preserved in open systems such as soils. when recorded in the rock record, Fe isotopic fractionation could document Fe transport by organic molecules or by microbes where such entities were present in the geologic past.

  7. Radon sources emanation in granitic soil and saprolite

    SciTech Connect

    Wollenberg, H.; Flexser, S.; Brimhall, G.; Lewis, C.

    1993-08-01

    Petrological and geochemical examinations of soil, saprolite, and quartz diorite protolith have been made at the Small Structures field site, Ben Lomond Mountain, California. Variations in Ra in soil and saprolite are mainly controlled by heterogeneities inherited from the parent quartz diorite. Fission-track radiography shows that U is concentrated in the primary accessory minerals, zircon and sphene. However, most importantly for Rn emanation, U is also concentrated in secondary sites: weathered sphene, biotite and plagioclase, grain coatings, and Fe-rich fracture linings which also contain a rare-earth phosphate mineral. This occurrence of U along permeable fracture zones suggests that soil-gas Rn from depth (> 2 m) is a significant contributor to Rn availability near the surface. Zones highest in emanation occur where fine pedogenic phases: gibbsite, amorphous silica, and iron oxyhydroxide are most abundant. Mass balance analyses of this soil-saprolite profile are in progress and preliminary indicate that a high-emanation zone corresponds to the upper portion of a zone of accumulation of U and Ba.

  8. [Soil net nitrogen mineralization in the typical temperate grassland].

    PubMed

    Liu, Xing-Ren; Dong, Yun-She; Qi, Yu-Chun; Domroes, Manfred

    2007-03-01

    Soil net nitrogen mineralization rate of three types temperate grassland in Inner Mongolia, China was studied using the resin-core technique. The major results include: the net nitrogen mineralization rate of the Stipa baicalensis meadow grassland, the Aneulolepidum Chinense grassland and the Stipa krylovii grassland were 0.333 kg x (hm2 x d)(-1), 0.316 kg x (hm2 x d)(-1) and 0.211 kg x (hm2 x d)(-1) respectively during the field incubation period of July to October, 2005; Soil net nitrogen mineralization accumulation and rates was remarkably different between phase incubation and continuous incubation during the same field incubation period; Rainfall was one of the main factors affecting nitrogen mineralization. The net nitrogen mineralization rate was correlated with the change of soil moisture in all of the measured sites, the correlation coefficient was 0.80, 0.61 and 0.56. PMID:17633647

  9. Effect of Mineral and Organic Soil Constituents on Microbial Mineralization of Organic Compounds in a Natural Soil

    PubMed Central

    Knaebel, David B.; Federle, Thomas W.; McAvoy, Drew C.; Vestal, J. Robie

    1994-01-01

    This research addressed the effect of mineral and organic soil constituents on the fate of organic compounds in soils. Specifically, it sought to determine how the associations between organic chemicals and different soil constituents affect their subsequent biodegradation in soil. Four 14C-labeled surfactants were aseptically adsorbed to montmorillonite, kaolinite, illite, sand, and humic acids. These complexes were mixed with a woodlot soil, and 14CO2 production was measured over time. The mineralization data were fitted to various production models by nonlinear regression, and a mixed (3/2)-order model was found to most accurately describe the mineralization patterns. Different mineralization patterns were observed as a function of the chemical and soil constituents. Surfactants that had been preadsorbed to sand or kaolinite usually showed similar mineralization kinetics to the control treatments, in which the surfactants were added to the soil as an aqueous solution. Surfactants that had been bound to illite or montmorillonite were typically degraded to lesser extents than the other forms, while surfactant-humic acid complexes were degraded more slowly than the other forms. The desorption coefficients (Kd) of the soil constituent-bound surfactants were negatively correlated with the initial rates of degradation (k1) and estimates of 14CO2 yield (Po) as well as actual total yields of 14CO2. However, there was no relationship between Kd and second-stage zero-order rates of mineralization (ko). Microbial community characteristics (biomass and activity) were not correlated with any of the mineralization kinetic parameters. Overall, this study showed that environmental form had a profound effect on the ultimate fate of biodegradable chemicals in soil. This form is defined by the physicochemical characteristics of the chemical, the composition and mineralogy of the soil, and the mode of entry of the chemical into the soil environment. PMID:16349465

  10. Relevance of mineral-organic associations in cryoturbated permafrost soils

    NASA Astrophysics Data System (ADS)

    Gentsch, Norman; Mikutta, Robert; Bárta, Jiří; Čapek, Petr; Gittel, Antje; Richter, Andreas; Šantrůčková, Hanna; Schnecker, Jörg; Shibistova, Olga; Urich, Tim; Wild, Birgit; Guggenberger, Georg

    2014-05-01

    Enhanced microbial decomposition of deep buried organic matter (OM) increase the release of CO2and CH4from high latitude ecosystems, thus being an uncertain but potentially crucial positive feedback to global warming. The role of soil minerals as stabilization agents of OM against microbial attack gain in importance as soon abiotic soil conditions will change in permafrost soils. We investigated changes in storage and turnover of soil organic carbon (OC) and total nitrogen (TN) associated with minerals in 27 cryoturbated permafrost soils from the west to the east Siberian Arctic. Furthermore, we studied the mineral composition and the potential of OM to interact with soil minerals via different binding mechanisms. Mineral-associated organic matter (MOM) was separated from particulate plant debris by density fractionation in sodium polytungstate (density cut-off 1.6 g cm-3). Their apparent 14C ages were determined by accelerator mass spectrometry and potential mineralization rates were analyzed in a 180 days incubation experiments at 5 and 15° C. The mineral composition was analyzed by X-ray diffraction and selective extractions. Desorption experiments (stepwise extraction with KCl and NaH2PO4) using the permafrost soils as well as reference soils from temperate regions (three Stagnolsols from Germany) were performed to study OM sorbed to mineral surfaces or complexed with polyvalent metal ions. The proportion of OC associated with minerals (MOC) ranged from 5.1 to 14.9 kg m-2 (average: 11.0 kg m-2), corresponding to ~55% from the total soil OC storage (average: 20.2 ± 8.0 kg m-2) in the first meter of the Cryosols. In contrast to temperate soils, where maximum MOC concentrations are present in topsoils, cambic, or spodic horizons, cryoturbation in permafrost soils leads to high MOC concentrations within the whole solum. Cryoturbated OM-rich pockets in the subsoil store 18% (2.0 ± 1.3 kg m-2) of the MOC while another 34% (3.8 ± 3.5 kg m-2) was located in the uppermost permafrost. In topsoil horizons, mineralization rates showed a similar pattern for MOM and the bulk soil controls. In contrast, even higher MOM respiration rates then the bulk control were found in the cryoturbated OM-rich pockets and permafrost horizons. These findings deviate from temperate soil environments where MOM is considered to contribute to a 'stabilized pool' with mean residence times from hundreds to thousands of years. Statistical analysis indicated that mineral-organic interactions primarily occurred with poorly crystalline Fe and Al phases and Fe/Al-OM complexes. However, the minor desorption of organic polyelectrolytes by NaH2PO4 in permafrost soils indicated that significantly lower amounts of OC were bound by ligand exchange to Fe and Al minerals or the edges of clay minerals in permafrost soils compared to the temperate reference soils. Therefore, stabilization of OM by mineral surfaces or polyvalent metal ions appears to be of minor relevance in arctic environments compared to temperate soils.

  11. Uranium Sequestration by Aluminum Phosphate Minerals in Unsaturated Soils

    SciTech Connect

    Jerden, James L. Jr.

    2007-07-01

    A mineralogical and geochemical study of soils developed from the unmined Coles Hill uranium deposit (Virginia) was undertaken to determine how phosphorous influences the speciation of uranium in an oxidizing soil/saprolite system typical of the eastern United States. This paper presents mineralogical and geochemical results that identify and quantify the processes by which uranium has been sequestered in these soils. It was found that uranium is not leached from the saturated soil zone (saprolites) overlying the deposit due to the formation of a sparingly soluble uranyl phosphate mineral of the meta-autunite group. The concentration of uranium in the saprolites is approximately 1000 mg uranium per kg of saprolite. It was also found that a significant amount of uranium was retained in the unsaturated soil zone overlying uranium-rich saprolites. The uranium concentration in the unsaturated soils is approximately 200 mg uranium per kg of soil (20 times higher than uranium concentrations in similar soils adjacent to the deposit). Mineralogical evidence indicates that uranium in this zone is sequestered by a barium-strontium-calcium aluminum phosphate mineral of the crandallite group (gorceixite). This mineral is intimately inter-grown with iron and manganese oxides that also contain uranium. The amount of uranium associated with both the aluminum phosphates (as much as 1.4 weight percent) has been measured by electron microprobe micro-analyses and the geochemical conditions under which these minerals formed has been studied using thermodynamic reaction path modeling. The geochemical data and modeling results suggest the meta-autunite group minerals present in the saprolites overlying the deposit are unstable in the unsaturated zone soils overlying the deposit due to a decrease in soil pH (down to a pH of 4.5) at depths less than 5 meters below the surface. Mineralogical observations suggest that, once exposed to the unsaturated environment, the meta-autunite group minerals react to form U(VI)- bearing aluminum phosphates. (author)

  12. Picloram and Aminopyralid Sorption to Soil and Clay Minerals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  13. Kinetics of methane oxidation in selected mineral soils

    NASA Astrophysics Data System (ADS)

    Walkiewicz, A.; Bulak, P.; Brzeziska, M.; W?odarczyk, T.; Polakowski, C.

    2012-10-01

    The kinetic parameters of methane oxidation in three mineral soils were measured under laboratory conditions. Incubationswere preceded by a 24-day preincubationwith 10%vol. of methane. All soils showed potential to the consumption of added methane. None of the soils, however, consumed atmospheric CH4. Methane oxidation followed the Michaelis-Menten kinetics, with relatively low values of parameters for Eutric Cambisol, while high values for Haplic Podzol, and especially for Mollic Gleysol which showed the highest methanotrophic activity and much lower affinity to methane. The high values of parameters for methane oxidation are typical for organic soils and mineral soils from landfill cover. The possibility of the involvement of nitrifying microorganisms, which inhabit the ammonia-fertilized agricultural soils should be verified.

  14. Soil mineral surfaces of paddy soils are accessible for organic carbon accumulation after decalcification

    NASA Astrophysics Data System (ADS)

    Wissing, Livia

    2013-04-01

    We studied organic carbon (OC) accumulation due to organo-mineral associations during soil development on calcareous parent material. Two chronosequences in Zhejiang Province, PR China, were investigated; one under paddy cultivation with a maximum soil age of 2000 years, and the other under upland crops where the oldest soil was 700 years old. Bulk soils and soil fractions of the uppermost A horizons were analyzed for OC concentrations and radio carbon contents. Total pedogenic iron (Fed) concentration was determined by dithionite extraction and the proportion of oxalate extractable iron (Feox) was extracted by using the method of Schwertmann (1964). The specific surface area (SSA) of soil minerals was measured by the BET-N2 method (Brunauer et al., 1938) under four conditions: untreated, after organic matter removal, after iron removal and after removal of both. Within 700/2000 years of pedogenesis, we observed no change in clay mineral composition and no additional formation of the SSA of soil minerals. But the soils differed in the degree of decalcification, OC accumulation and in the formation of iron. Paddy soil management led to an enhanced decalcification and larger OC accumulation. Management-induced redox cycles caused larger proportions of Feox in paddy soils. Their large SSA, added to the surface area of clay minerals, provided additional options for OC covering. Unexpectedly, there was no evidence of formation of secondary minerals during soil development, which could provide new surfaces for OC accumulation. However, the study revealed higher OC coverings of mineral surfaces after decalcification in paddy soils. As carbonate and Ca2+ ions seemed to interconnect clay minerals, making their surface accessible to OC, the faster dissolution of carbonate and leaching of Ca2+ ions in paddy soils made additional clay mineral surfaces available to OC. In contrast, the surface area of minerals in non-paddy soils, in which decalcification was much lower, seemed to be partly inaccessible for OC covering due to strong microaggregation by cementation with carbonate and Ca2+-bridging. The smaller accumulation of mineral-associated SOM in non-paddy soils was additionally confirmed by the retarded replacement of the inherited carbon. The accelerated decalcification of paddy soils led to enhanced accessibility of mineral surfaces for OC covering, which intensified OC accumulation from the early stages of soil formation onward. References Brunauer, S., Emmett, P.H., Teller, E., (1938). Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60 (2), 309-319. Schwertmann, U., 1964. Differenzierung der Eisenoxide des Bodens durch Extraktion mit Ammoniumoxalat-Lsung. Zeitschrift fr Pflanzenernhrung, Dngung, Bodenkunde 105 (3), 194-202.

  15. Adsorption coefficients for TNT on soil and clay minerals

    NASA Astrophysics Data System (ADS)

    Rivera, Rosngela; Pabn, Julissa; Prez, Omarie; Muoz, Miguel A.; Mina, Nairmen

    2007-04-01

    To understand the fate and transport mechanisms of TNT from buried landmines is it essential to determine the adsorption process of TNT on soil and clay minerals. In this research, soil samples from horizons Ap and A from Jobos Series at Isabela, Puerto Rico were studied. The clay fractions were separated from the other soil components by centrifugation. Using the hydrometer method the particle size distribution for the soil horizons was obtained. Physical and chemical characterization studies such as cation exchange capacity (CEC), surface area, percent of organic matter and pH were performed for the soil and clay samples. A complete mineralogical characterization of clay fractions using X-ray diffraction analysis reveals the presence of kaolinite, goethite, hematite, gibbsite and quartz. In order to obtain adsorption coefficients (K d values) for the TNT-soil and TNT-clay interactions high performance liquid chromatography (HPLC) was used. The adsorption process for TNT-soil was described by the Langmuir model. A higher adsorption was observed in the Ap horizon. The Freundlich model described the adsorption process for TNT-clay interactions. The affinity and relative adsorption capacity of the clay for TNT were higher in the A horizon. These results suggest that adsorption by soil organic matter predominates over adsorption on clay minerals when significant soil organic matter content is present. It was found that, properties like cation exchange capacity and surface area are important factors in the adsorption of clayey soils.

  16. 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. PMID:11790001

  17. The effect of soil horizon and mineral type on the distribution of siderophores in soil

    NASA Astrophysics Data System (ADS)

    Ahmed, Engy; Holmstrm, Sara J. M.

    2014-04-01

    Iron is a key component of the chemical architecture of the biosphere. Due to the low bioavailability of iron in the environment, microorganisms have developed specific uptake strategies like production of siderophores. Siderophores are operationally defined as low-molecular-mass biogenic Fe(III)-binding compounds, that can increase the bioavailability of iron by promoting the dissolution of iron-bearing minerals. In the present study, we investigated the composition of dissolved and adsorbed siderophores of the hydroxamate family in the soil horizons of podzol and the effect of specific mineral types on siderophores. Three polished mineral specimens of 3 cm 4 cm 3 mm (apatite, biotite and oligioclase) were inserted in the soil horizons (O (organic), E (eluvial) and B (upper illuvial)). After two years, soil samples were collected from both the bulk soil of the whole profile and from the soil attached to the mineral surfaces. The concentration of ten different fungal tri-hydroxamates within ferrichromes, fusigen and coprogens families, and five bacterial hydroxamates within the ferrioxamine family were detected. All hydroxamate types were determined in both soil water (dissolved) and soil methanol (adsorbed) extracts along the whole soil profile by high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS); hence, the study is the most extensive of its kind. We found that coprogens and fusigen were present in much higher concentrations in bulk soil than were ferrioxamines and ferrichromes. On the other hand, the presence of the polished mineral completely altered the distribution of siderophores. In addition, each mineral had a unique interaction with the dissolved and adsorbed hydroxamates in the different soil horizons. Thus siderophore composition in the soil environment is controlled by the chemical, physical and biological characteristics of each soil horizon and also by the available mineral types.

  18. Qualitative soil mineral analysis by EDXRF, XRD and AAS probes

    NASA Astrophysics Data System (ADS)

    Singh, Virendra; Agrawal, H. M.

    2012-12-01

    Soil minerals study is vital in terms of investigating the major soil forming compounds and to find out the fate of minor and trace elements, essential for the soil-plant interaction purpose. X-ray diffraction (XRD) has been a popular technique to search out the phases for different types of samples. For the soil samples, however, employing XRD is not so straightforward due to many practical problems. In the current approach, principal component analysis (PCA) has been used to have an idea of the minerals present, in qualitative manner, in the soil under study. PCA was used on the elemental concentrations data of 17 elements, determined by the energy dispersive X-ray fluorescence (EDXRF) technique. XRD analysis of soil samples has been done also to identify the minerals of major elements. Some prior treatments, like removal of silica by polytetrafluoroethylene (PTFE) slurry and grinding with alcohol, were given to samples to overcome the peak overlapping problems and to attain fine particle size which is important to minimize micro-absorption corrections, to give reproducible peak intensities and to minimize preferred orientation. A 2? step of 0.05/min and a longer dwell time than normal were used to reduce interferences from background noise and to increase the counting statistics. Finally, the sequential extraction procedure for metal speciation study has been applied on soil samples. Atomic absorption spectroscopy (AAS) was used to find the concentrations of metal fractions bound to various forms. Applying all the three probes, the minerals in the soils can be studied and identified, successfully.

  19. Characterizing regional soil mineral composition using spectroscopyand geostatistics

    USGS Publications Warehouse

    Mulder, V.L.; de Bruin, S.; Weyermann, J.; Kokaly, Raymond F.; Schaepman, M.E.

    2013-01-01

    This work aims at improving the mapping of major mineral variability at regional scale using scale-dependent spatial variability observed in remote sensing data. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and statistical methods were combined with laboratory-based mineral characterization of field samples to create maps of the distributions of clay, mica and carbonate minerals and their abundances. The Material Identification and Characterization Algorithm (MICA) was used to identify the spectrally-dominant minerals in field samples; these results were combined with ASTER data using multinomial logistic regression to map mineral distributions. X-ray diffraction (XRD)was used to quantify mineral composition in field samples. XRD results were combined with ASTER data using multiple linear regression to map mineral abundances. We testedwhether smoothing of the ASTER data to match the scale of variability of the target sample would improve model correlations. Smoothing was donewith Fixed Rank Kriging (FRK) to represent the mediumand long-range spatial variability in the ASTER data. Stronger correlations resulted using the smoothed data compared to results obtained with the original data. Highest model accuracies came from using both medium and long-range scaled ASTER data as input to the statistical models. High correlation coefficients were obtained for the abundances of calcite and mica (R2 = 0.71 and 0.70, respectively). Moderately-high correlation coefficients were found for smectite and kaolinite (R2 = 0.57 and 0.45, respectively). Maps of mineral distributions, obtained by relating ASTER data to MICA analysis of field samples, were found to characterize major soil mineral variability (overall accuracies for mica, smectite and kaolinite were 76%, 89% and 86% respectively). The results of this study suggest that the distributions of minerals and their abundances derived using FRK-smoothed ASTER data more closely match the spatial variability of soil and environmental properties at regional scale.

  20. Bromide Adsorption by Reference Minerals and Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bromide, Br-, adsorption behavior was investigated on amorphous Al and Fe oxide, montmorillonite, kaolinite, and temperate and tropical soils. Bromide adsorption decreased with increasing solution pH with minimal adsorption occurring above pH 7. Bromide adsorption was higher for amorphous oxides t...

  1. Active Layer Soil Carbon and Nutrient Mineralization, Barrow, Alaska, 2012

    DOE Data Explorer

    Stan D. Wullschleger; Holly M. Vander Stel; Colleen Iversen; Victoria L. Sloan; Richard J. Norby; Mallory P. Ladd; Jason K. Keller; Ariane Jong; Joanne Childs; Deanne J. Brice

    2015-10-29

    This data set consists of bulk soil characteristics as well as carbon and nutrient mineralization rates of active layer soils manually collected from the field in August, 2012, frozen, and then thawed and incubated across a range of temperatures in the laboratory for 28 day periods in 2013-2015. The soils were collected from four replicate polygons in each of the four Areas (A, B, C, and D) of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Soil samples were coincident with the established Vegetation Plots that are located in center, edge, and trough microtopography in each polygon. Data included are 1) bulk soil characteristics including carbon, nitrogen, gravimetric water content, bulk density, and pH in 5-cm depth increments and also by soil horizon, 2) carbon, nitrogen, and phosphorus mineralization rates for soil horizons incubated aerobically (and in one case both aerobically and anaerobically) for 28 days at temperatures that included 2, 4, 8, and 12 degrees C. Additional soil and incubation data are forthcoming. They will be available when published as part of another paper that includes additional replicate analyses.

  2. NATURAL ATTENUATION OF COPPER IN SOILS AND SOIL MINERALS - II

    EPA Science Inventory

    The bioabailability and toxicity of Cu in soils is controlled by a number of soil properties and processes. Some of these such as pH, adsorption/desorption and competition with beneficial cations have been extensively studied. However, the effects of natural attenuation (or aging...

  3. NATURAL ATTENUATION OF COPPER IN SOILS AND SOIL MINERALS - I

    EPA Science Inventory

    The bioavailability and toxicity of Cu in soils is controlled by a number of soil properties and processes. Some of these such as pH, adsorption/desorption and competition with beneficial cations have been extensively studied. However, the effects of natural attenuation (or aging...

  4. Rapid mineral differentiation among horizons of a meadow soil

    NASA Astrophysics Data System (ADS)

    Szalai, Zoltán; Ringer, Marianna; Kiss, Klaudia; Horváth Szabó, Kata; Németh, Tibor; Sipos, Péter; Madarász, Balázs; Jakab, Gergely

    2015-04-01

    Soil development under hydromorphic conditions may results intense mineral transformation and rapid vertical differentiation in the profile. Original papers refer more than hundreds of years for this kinds of mineral transformations. We suppose that this process could be more rapid. Present paper focuses on the profile development of a sandy meadow soil (calcic, gleyic Phaeozem ferric, arenic) from the soil mineralogical viewpoint. The main aim was to explore the degree of mineral phase alteration via soil formation during a half-century under hydromorphic conditions. The studied soil is located in a swampy area (near to Ceglédbercel, Hungary). The parent material deposited during an extremely heavy flood event in 1963. The reference (parent) material can be found near to the study site. We combined routine field tests (carbonate content, dipididil test) with laboratory measurements (selective extractions for the determination of amorphous and crystalline Fe, and Mn content; X-ray phase analysis; X-ray fluorescence spectroscopy; particle sizing by laser diffraction; NDIR and FT-IR and DRS spectrometry), whereas Eh and pH measured by field monitoring station. The most intense mineralogical transformations developed in the zone of the heaviest redox oscillation. Results show that well developed horizons have emerged during fifty years in the studied soil. This time was enough for bivalent and trivalent iron mineral crystallisation and smectite formation in this zone. The high proportion of amorphous and colloidal phases refers to very intensive recent processes. Soil formation under hydromorphic conditions proceeds at higher speeds contrariwise to the century time scale reported in sources (discussing non-waterlogged cases). Support of the Hungarian Research Fund OTKA under contracts K100180 (for Z. Szalai) and K100181 (for T Németh) are gratefully acknowledged.

  5. Spectroscopy and reactivity of mineral analogs of the Martian soil

    NASA Technical Reports Server (NTRS)

    Banin, A.; Orenberg, J.; Roush, T.

    1991-01-01

    To answer the question of why life occurred on Earth but not on Mars requires a study of the geochemical and physical aspects of the Martian soil. Some of the best Mars analog mineral models of the soil have been prepared and justified according to known constraints of chemical composition, reflectance spectroscopy, and chemical reactivity. Detailed laboratory reflectance spectra in the ultraviolet, visible, and near infrared (.30 to 2.5 microns) and the infrared (2.5 to 25 microns) regions have been obtained for the pure candidate minerals and some analog mixtures and compared to Mars reflectance spectra. Modeling of the reflectance spectra from optical constraints determined for the analog minerals has begun and will be interpreted in terms of the effects of particle size variation, component mixing, and soil packing upon remotely sensed reflectance spectra. This has implications not only for Mars, but for other planets and planetoids. The ratio of Fe(II)/Fe(III) in the Martian soil analog materials on spectral reflectance in the visible range has begun, and the results will be evaluated according to conformity with the visible Mars reflectance spectrum. Some initial LR and GEX data have been collected for the mineral samples and their mixtures, which can be compared with the Viking data and interpreted in terms of the redox (Fe(II)/Fe(III) environment.

  6. [Analysis of XRD spectral characteristics of soil clay mineral in two typical cultivated soils].

    PubMed

    Zhang, Zhi-Dan; Luo, Xiang-Li; Jiang, Hai-Chao; Li, Qiao; Shen, Cong-Ying; Liu, Hang; Zhou, Ya-Juan; Zhao, Lan-Po; Wang, Ji-Hong

    2014-07-01

    The present paper took black soil and chernozem, the typical cultivated soil in major grain producing area of Northeast, as the study object, and determinated the soil particle composition characteristics of two cultivated soils under the same climate and location. Then XRD was used to study the composition and difference of clay mineral in two kinds of soil and the evolutionary mechanism was explored. The results showed that the two kinds of soil particles were composed mainly of the sand, followed by clay and silt. When the particle accumulation rate reached 50%, the central particle size was in the 15-130 microm interval. Except for black soil profile of Shengli Xiang, the content of clay showed converse sequence to the central particle in two soils. Clay accumulated under upper layer (18.82%) in black soil profile while under caliche layer (17.41%) in chernozem profile. Clay content was the least in parent material horizon except in black profile of Quanyanling. Analysis of clay XRD atlas showed that the difference lied in not only the strength of diffraction peak, but also in the mineral composition. The main contents of black soil and chernozem were both 2 : 1 clay, the composition of black soil was smectite/illite mixed layer-illite-vermiculite and that of chernozem was S/I mixture-illite-montmorillonite, and both of them contained little kaolinite, chlorite, quartz and other primary mineral. This paper used XRD to determine the characteristics of clay minerals comprehensively, and analyzed two kinds of typical cultivated soil comparatively, and it was a new perspective of soil minerals study. PMID:25269317

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

    SciTech Connect

    Garten Jr, Charles T

    2009-01-01

    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{sub 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.

  8. Soil type influences crop mineral composition in Malawi.

    PubMed

    Joy, Edward J M; Broadley, Martin R; Young, Scott D; Black, Colin R; Chilimba, Allan D C; Ander, E Louise; Barlow, Thomas S; Watts, Michael J

    2015-02-01

    Food supply and composition data can be combined to estimate micronutrient intakes and deficiency risks among populations. These estimates can be improved by using local crop composition data that can capture environmental influences including soil type. This study aimed to provide spatially resolved crop composition data for Malawi, where information is currently limited. Six hundred and fifty-two plant samples, representing 97 edible food items, were sampled from >150 sites in Malawi between 2011 and 2013. Samples were analysed by ICP-MS for up to 58 elements, including the essential minerals calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), selenium (Se) and zinc (Zn). Maize grain Ca, Cu, Fe, Mg, Se and Zn concentrations were greater from plants grown on calcareous soils than those from the more widespread low-pH soils. Leafy vegetables from calcareous soils had elevated leaf Ca, Cu, Fe and Se concentrations, but lower Zn concentrations. Several foods were found to accumulate high levels of Se, including the leaves of Moringa, a crop not previously been reported in East African food composition data sets. New estimates of national dietary mineral supplies were obtained for non-calcareous and calcareous soils. High risks of Ca (100%), Se (100%) and Zn (57%) dietary deficiencies are likely on non-calcareous soils. Deficiency risks on calcareous soils are high for Ca (97%), but lower for Se (34%) and Zn (31%). Risks of Cu, Fe and Mg deficiencies appear to be low on the basis of dietary supply levels. PMID:25461061

  9. Dielectric Constant Measurements on Lunar Soils and Terrestrial Minerals

    NASA Technical Reports Server (NTRS)

    Anderson, R. C.; Buehler, M. G.; Seshardri, S.; Schaap, M. G.

    2004-01-01

    The return to the Moon has ignited the need to characterize the lunar regolith using in situ methods. An examination of the lunar regolith samples collected by the Apollo astronauts indicates that only a few minerals (silicates and oxides) need be considered for in situ resource utilization (ISRU). This simplifies the measurement requirements and allows a detailed analysis using simple methods. Characterizing the physical properties of the rocks and soils is difficult because of many complex parameters such as soil temperature, mineral type, grain size, porosity, and soil conductivity. In this presentation, we will show that the dielectric constant measurement can provide simple detection for oxides such as TiO2, FeO, and water. Their presence is manifest by an unusually large imaginary permittivity.

  10. Database of Polish arable mineral soils: a review

    NASA Astrophysics Data System (ADS)

    Bieganowski, A.; Witkowska-Walczak, B.; Gliski, J.; Soko?owska, Z.; S?awi?ski, C.; Brzezi?ska, M.; W?odarczyk, T.

    2013-09-01

    The database of Polish arable mineral soils is presented. The database includes a lot of information about the basic properties of soils and their dynamic characteristics. It was elaborated for about 1 000 representative profiles of soils in Poland The database concerns: particle size distribution, organic carbon content, acidity-pH, specific surface area, hydrophobicity - solidliquid contact angle, static and dynamic hydrophysical properties, oxidation-reduction properties and selected biological (microbiological) properties of soils. Knowledge about soil characteristics is indispensable for description, interpretation and prediction of the course of physical, chemical and biological processes, and modelling these processes requires representative data. The utility of simulation and prediction models describing phenomena which take place in the soil-plant-atmosphere system greatly depends on the precision of data concerning characteristics of soil. On the basis of this database, maps of chosen soil properties are constructed. The aim of maps is to provide specialists in agriculture, ecology, and environment protection with an opportunity to gain knowledge of soil properties and their spatial and seasonal variability.

  11. Anaerobic N mineralization in paddy soils in relation to inundation management, physicochemical soil fractions, mineralogy and soil properties

    NASA Astrophysics Data System (ADS)

    Sleutel, Steven; Kader, Mohammed Abdul; Ara Begum, Shamim; De Neve, Stefaan

    2013-04-01

    Anaerobic N mineralization measured from (saturated) repacked soil cores from 25 paddy fields in Bangladesh and was previously found to negatively related to soil N content on a relative basis. This suggests that other factors like soil organic matter (SOM) quality or abiotic factors instead control the anaerobic N mineralization process. We therefore assessed different physical and chemical fractions of SOM, management factors and various soil properties as predictors for the net anaerobic N mineralization. 1° First, we assessed routinely analyzed soil parameters (soil N and soil organic carbon, texture, pH, oxalate- and pyrophosphate-extractable Fe, Al, and Mn, fixed-NH4 content). We found no significant influences of neither soil mineralogy nor the annual length of inundation on soil N mineralization. The anaerobic N mineralization correlated positively with Na-pyrophosphate-extractable Fe and negatively with pH (both at P<0.01). At this stage it is, however, not known if these relations between net evolution of NH4 and pH and Fe content are causal or indirect. 2° Second, the 25 samples collected from farmers' fields were physically fractionated into particulate OM and silt and clay associated OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6%NaOCl to isolate an oxidation-resistant OM fraction, followed by extraction of mineral bound OM with 10%HF thereby isolating the HF-resistant OM. None of the physicochemical SOM fractions were found useful predictors anaerobic N mineralization. The linkage between these chemical soil N fractions and N supplying processes actually occurring in the soil thus appears to be weak. Regardless, we hypothesize that variation in strength of N-mineral and N-OM linkages is likely to explain variation in bio-availability of organic N and proneness to mineralization. Yet, in order to separate kinetically different soil N fractions we then postulated that an alternative approach would be required, which instead isolates soil N fractions on the basis of bonding strength. In this respect bonding strength should be seen as opposite of proneness to dissolution of released N into water, the habitat of soil microorganisms mediating soil N mineralization. We hypothesize that soil N extracted by water at increasing temperatures would reflect such N fractions with increasing bonding strength, in turn equivalent to decreasing bio-availability. Although water has frequently been used to extract labile SOM, its use has mostly been limited to 100°C. 3° Third we developed sub critical water extraction (SCWE) at 100°C, 150°C and 200°C to isolate SOM fractions from the set of 25 paddy soil samples. In all cases, SCWE organic carbon (SCWE-OC) and N (SCWE-N) increased exponentially with the increase of temperature. SCWE preferentially extracted N over OC with increasing temperature. The efficiency of SCWE and the selectivity towards N were both lower in soils with increasingly reactive clay mineralogy. No correlations were found between the SCWE fractions and anaerobic N mineralization rate. In conclusion, SOM quantity and SOM quality, here represented by C and N distribution over physicochemical fractions, don't seem to dominantly determine anaerobic N mineralization in primarily young floodplain paddy soils. Other factors with exceeding control (pH and pyrophosphate extractable Fe) appear to exist. Possibly, the specific young genesis stage of most of the soils included (termed 'floodplain' soils) results in a limited availability of readily reducible Fe. Being an important alternative electron acceptor under submerged conditions, the availability of Fe, which is also controlled by pH, may be a bottleneck in the anaerobic N mineralization process. This needs to be further investigated by controlled incubation experiments with detailed follow-up of pH, redox potential, Fe in solution and mineral N.

  12. Activities of N-Mineralization Enzymes Associated With Soil Aggregate Size Fractions of Three Tillage Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrogen mineralization occurring near the soil surface of agro-ecosystems determines the quantity of plant available N, and soil enzymes produced by microorganisms play significant roles in the N mineralization process. Tillage systems may influence soil microbial communities and N mineralization e...

  13. Experimental epithermal alteration of synthetic Los Angeles meteorite: Implications for the origin of Martian soils and identification of hydrothermal sites on Mars

    NASA Astrophysics Data System (ADS)

    Hurowitz, Joel A.; McLennan, Scott M.; Lindsley, Donald H.; Schoonen, Martin A. A.

    2005-07-01

    The dissolution behavior and secondary minerals generated by experimental alteration of a synthetic Los Angeles basaltic shergottite (LA) were evaluated at epithermal (75C) conditions. Starting pH values of 1.1 and 3.6 and water-rock ratios ranging from 100 to 2000 were studied using flow-through and batch reactor experimental apparatus. Dissolution of plagioclase dominates effluent solution chemistry under all experimental conditions. Little Mg is released to solution because nearly 100% of the Mg in unaltered LA is contained in pyroxene M1 sites, which are relatively resistant to dissolution. Secondary minerals generated include siliceous residue, amorphous SiO2, lepidocrocite and ferrihydrite, anhydrite, alunogen, rhomboclase, ferrinatrite, halite, and unidentified Ca and Na sulfates. The dominance of alteration products of plagioclase suggests that LA-type basalts have not contributed significantly to the Martian soils. The search for hydrothermal sites by remote sensing may be hampered by the general similarity of the alteration products found in the near-surface epithermal environment to those thought to exist in Martian soils (sulfates, iron oxyhydroxides, amorphous silica). However, the unique chemical composition of secondary products formed by LA alteration may make detection of recent hydrothermal alteration of evolved basaltic rocks more straightforward. In addition, alteration in terrestrial epithermal environments associated with mafic to intermediate volcanic rocks generally produces abundant sulfides and kaolinite, two potentially unique mineral phases which might also indicate the presence of active or extinct hydrothermal systems.

  14. Mineralization of N in Soils Amended with Dairy Manure as Affected by Wetting/Drying Cycles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Interest in manure management and its effects on nitrogen (N) mineralization has increased in recent years. The focus of this research was to investigate the N mineralization rates of different soil types in Coastal Plain soils and compare them to a soil from Illinois. Soils with and without dairy ...

  15. Activities of N-mineralization enzymes associated with soil aggregates in three different tillage systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil enzymes released by microorganisms play a significant role in N mineralization process that determines N availability for plant growth. Soil aggregates of different sizes provide diverse microhabitats for microorganisms and therefore influence soil enzyme activities. We hypothesize that enzyme ...

  16. Electromagnetic characteristics of Cambodian soil: implication for land mine detection in soil containing ferromagnetic minerals

    NASA Astrophysics Data System (ADS)

    Katsube, John; Klassen, Rod; Das, Yogadhish; Benn, Keith; Best, Mel; Ernst, Richard

    2002-08-01

    Electromagnetic (EM: Magnetic Susceptibility [MS], Electrical Conductivity) and soil texture characteristics were determined for a Cambodian soil from an area where landmine detection interference has been experienced. The purpose was to collect information for developing techniques to discriminate between EM signals from small metallic particles in landmines and from iron-oxides or ferromagnetic mineral grains in soil. Ferromagnetic minerals are iron-oxides with strong MS characteristics. Results indicate that this soil consisted of four textural components: clasts (2-10 mm), medium-coarse-sand (<2.0 mm), fine-sand (<0.25 mm) and clay-silt (<0.063 mm). The coarse-sand had high MS values (~550x10-8 SI/kg) due to high ferromagnetic mineral content (~20 wt.%). Some large rounded clasts, however, had considerably higher MS values (~11000x10-8 SI/kg) due to high ferromagnetic mineral concentrations (30-60 wt.%), a likely source of significant landmine detection interference. The finer components had smaller MS values and iron-oxide contents. Complex electrical conductivity (1-106 Hz) of iron-oxides showed significant frequency dependence due to capacitance effects of electrochemical double layers on their surfaces in contact with soil moisture. This frequency dependence of iron-oxides may provide opportunities for potential EM system's design to discriminate between soil and landmine responses.

  17. Mineral Dissolution and Precipitation due to Carbon Dioxide-Water-Rock Interactions: The Significance of Accessory Minerals in Carbonate Reservoirs (Invited)

    NASA Astrophysics Data System (ADS)

    Kaszuba, J. P.; Marcon, V.; Chopping, C.

    2013-12-01

    Accessory minerals in carbonate reservoirs, and in the caprocks that seal these reservoirs, can provide insight into multiphase fluid (CO2 + H2O)-rock interactions and the behavior of CO2 that resides in these water-rock systems. Our program integrates field data, hydrothermal experiments, and geochemical modeling to evaluate CO2-water-rock reactions and processes in a variety of carbonate reservoirs in the Rocky Mountain region of the US. These studies provide insights into a wide range of geologic environments, including natural CO2 reservoirs, geologic carbon sequestration, engineered geothermal systems, enhanced oil and gas recovery, and unconventional hydrocarbon resources. One suite of experiments evaluates the Madison Limestone on the Moxa Arch, Southwest Wyoming, a sulfur-rich natural CO2 reservoir. Mineral textures and geochemical features developed in the experiments suggest that carbonate minerals which constitute the natural reservoir will initially dissolve in response to emplacement of CO2. Euhedral, bladed anhydrite concomitantly precipitates in response to injected CO2. Analogous anhydrite is observed in drill core, suggesting that secondary anhydrite in the natural reservoir may be related to emplacement of CO2 into the Madison Limestone. Carbonate minerals ultimately re-precipitate, and anhydrite dissolves, as the rock buffers the acidity and reasserts geochemical control. Another suite of experiments emulates injection of CO2 for enhanced oil recovery in the Desert Creek Limestone (Paradox Formation), Paradox Basin, Southeast Utah. Euhedral iron oxyhydroxides (hematite) precipitate at pH 4.5 to 5 and low Eh (approximately -0.1 V) as a consequence of water-rock reaction. Injection of CO2 decreases pH to approximately 3.5 and increases Eh by approximately 0.1 V, yielding secondary mineralization of euhedral pyrite instead of iron oxyhydroxides. Carbonate minerals also dissolve and ultimately re-precipitate, as determined by experiments in the Madison Limestone, but pyrite will persist and iron oxyhydroxides will not recrystallize.

  18. 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 25C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.220.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.53.4) and the mineral soil (2.12.8) 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

  19. The structure of iron-oxyhydroxide mounds affected by iron-oxidizing bacteria at shallow submarine hydrothermal vent in Satsuma Iwo-Jima

    NASA Astrophysics Data System (ADS)

    Kuratomi, T.; Kiyokawa, S.; Ikehara, M.; Goto, S.; Hoshino, T.; Ikegami, F.; Minowa, Y.

    2014-12-01

    Satsuma Iwo-Jima, located 38km south of Kyusyu island, Japan, is preserved and identified on occurring iron precipitation at shallow ocean where can be recorded modern analogy of iron precipitation and sedimentation. This is a volcanic island in the northwestern rim of Kikai caldera. Iron- and silica-rich mounds (0.5-3m wide and 0.2-7m high) are developing with hydrothermal activity (pH=5.5, 50-60 degree Celsius), and there is high deposition rate of iron-oxides (33 cm/year). In this study, we analyzed samples (20-30 cm long) recovered from iron oxidized mounds at seafloor by the observation with CT scan, FE-SEM and thin-sectioned samples, and the chemical analysis with EDS, XRF, XRD and DNA, and found that the structure of mounds has unique information. Each mounds are formed two layers: blackish hard layer and brownish soft layer. The inside of samples is constructed from the aggregation of convex structure (3-4 cm) covered by hard layers as a rim. Petrographic observations indicate that both layers have filament-like forms, and the form in soft layer is perpendicular to that in the hard layer. The number of iron oxides particles observed on filament-like forms in soft layer increases toward hard layer. Hard layer consists of aggregation of bacillus-like form as the chain of particle (about 2 um). At soft layer, on the other hand, bacteria-like form with smaller particles (<0.5 um) is observed. Bacteria-like form could be classified into 3 types (helix, ribbon-like, twisted). Furthermore, hard layers consist of ferrihydrite and opal-A (Si: 26.8%, Fe: 56.0%) and soft one is composed by ferrihydrite, opal-A and silica mineral (Si: 36.5%, Fe: 43.5%). Mariprofundus ferrooxydansknown as iron-oxidizing bacteria belonging to Zeta-proteobacteria identified in this matter. Bacteria-like form is considered to be the stalk made by iron-oxidizing bacteria. Such neutrophilic iron-oxidizing bacteria prefers an environment of redox interface between hydrothermal water and seawater, and their activity made hard rim at outer soft layer. This high deposition rate of iron hydroxides probably derives from the chemical reaction of oxidizing ferrous to ferric around stalks of iron-oxidizing bacteria.

  20. Mineral exploration and soil analysis using in situ neutron activation

    USGS Publications Warehouse

    Senftle, F.E.; Hoyte, A.F.

    1966-01-01

    A feasibility study has been made to operate by remote control an unshielded portable positive-ion accelerator type neutron source to induce activities in the ground or rock by "in situ" neutron irradiation. Selective activation techniques make it possible to detect some thirty or more elements by irradiating the ground for periods of a few minutes with either 3-MeV or 14-MeV neutrons. The depth of penetration of neutrons, the effect of water content of the soil on neutron moderation, gamma ray attenuation in the soil and other problems are considered. The analysis shows that, when exploring for most elements of economic interest, the reaction 2H(d,n)3He yielding ??? 3-MeV neutrons is most practical to produce a relatively uniform flux of neutrons of less than 1 keV to a depth of 19???-20???. Irradiation with high energy neutrons (??? 14 MeV) can also be used and may be better suited for certain problems. However, due to higher background and lower sensitivity for the heavy minerals, it is not a recommended neutron source for general exploration use. Preliminary experiments have been made which indicate that neutron activation in situ is feasible for a mineral exploration or qualititative soil analysis. ?? 1976.

  1. GEMAS: Mineral magnetic properties of European agricultural soils

    NASA Astrophysics Data System (ADS)

    Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Fabian, Karl; Nourgaliev, Danis; Reimann, Clemens

    2015-04-01

    The GEMAS survey of European agricultural soil provides a unique opportunity to create the first comprehensive overview of mineral magnetic properties in agricultural soil on a continental scale. Samples from the upper 20 cm were taken in large agricultural fields (Ap-sample) at a density of 1 site/2500 km2. After air drying and sieving to < 2 mm, low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k was measured on 2500 samples using a Bartington MS2B sensor to obtain frequency dependence of magnetic susceptibility kfd. Hysteresis properties are determined using a J coercivity spectrometer, built in the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T, taking approximately 15 minutes. This allows to measure a wide range of magnetic parameters for large sample collections. Because the GEMAS geochemical atlas provides a comprehensive set of geochemical measurements characterizing the individual soil samples, the new data allow to study magnetic parameters in relation to chemical and geological parameters. The results show a clear large scale spatial distribution with e.g. broad distinct lows of k over sandy sediments of the last glaciation in central northern Europe and other sedimentary basins. More localized positive k anomalies occur near young volcanism, or old basalts exposed on the surface. On the other hand, frequency dependence of k displays a much more scattered behavior, indicating either high noise level, or large local variability. Clearly distinguishable, small-scale patterns in the randomized data set indicate that the latter is more likely. This indicates that local influences on soil magnetic properties, including anthropogenic effects, may be easier detected by frequency dependence than by k itself, which is largely controlled by geological and climatic background variability. Mapping the isothermal mineral magnetic properties shows again a clear relation to large scale European geology. Thereby, the GEMAS data set of magnetic parameters provides a continent wide reference of the natural background in Ap soil. For the first time the geological background variability of magnetic minerals for national and local soil studies is defined at the European scale.

  2. 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. PMID:24428735

  3. Solubilization of Iron-Containing Minerals by Soil Microorganisms

    PubMed Central

    Arrieta, Luis; Grez, Renato

    1971-01-01

    Eighty-eight strains of microorganisms were isolated from soils collected in northern and southern Chile, and 10 fungi which showed the highest solubilizing action upon the iron in granodiorite were then selected. These fungi were incubated with the following iron-containing minerals: augite, hornblende, biotite, magnetite, hematite, and the igneous rock granodiorite. The solubility of iron in these minerals depended on their nature, crystalline structure, the concentration of metabolic products, or all three. Complex formation could be the mechanism involved, as a strong cation-exchange resin was not able to extract Fe from culture solutions. This conclusion is also confirmed by the RF values obtained by thin-layer chromatography of iron-containing culture solutions. PMID:5167095

  4. Infrared spectra of lunar soil analogs. [spectral reflectance of minerals

    NASA Technical Reports Server (NTRS)

    Aronson, J. R.

    1977-01-01

    The infrared spectra of analogs of lunar soils were investigated to further the development of methodology for interpretation of remotely measured infrared spectra of the lunar surface. The optical constants of dunite, bytownite, augite, ilmenite, and a mare glass analog were obtained. The infrared emittance spectra of powdered minerals were measured and compared with spectra calculated by the reflectance theory using a catalog of optical constants. The results indicate that the predictions of the theory closely simulate the experimental measurements if the optical constants are properly derived.

  5. Interaction of root exudates with the mineral soil constituents and their effect on mineral weathering

    NASA Astrophysics Data System (ADS)

    Mimmo, T.; Terzano, R.; Medici, L.; Lettino, A.; Fiore, S.; Tomasi, N.; Pinton, R.; Cesco, S.

    2012-04-01

    Plants release significant amounts of high and low molecular weight organic compounds into the rhizosphere. Among these exudates organic acids (e.g. citric acid, malic acid, oxalic acid), phenolic compounds (e.g. flavonoids), amino acids and siderophores of microbial and/or plant origin strongly influence and modify the biogeochemical cycles of several elements, thus causing changes in their availability for plant nutrition. One class of these elements is composed by the trace elements; some of them are essential for plants even if in small concentrations and are considered micronutrients, such as Fe, Zn, Mn. Their solubility and bioavailability can be influenced, among other factors, by the presence in soil solution of low molecular weight root exudates acting as organic complexing agents that can contribute to the mineral weathering and therefore, to their mobilization in the soil solution. The mobilized elements, in function of the element and of its concentration, can be either important nutrients or toxic elements for plants. The objective of this study was to assess the influence of several root exudates (citric acid, malic acid, oxalic acid, genistein, quercetin and siderophores) on the mineralogy of two different soils (an agricultural calcareous soil and an acidic polluted soil) and to evaluate possible synergic or competitive behaviors. X-ray diffraction (XRD) coupled with Electron Probe Micro Analysis (EPMA) was used to identify the crystalline and amorphous phases which were subjected to mineral alteration when exposed to the action of root exudates. Solubilization of trace metals such as Cu, Zn, Ni, Cr, Pb, Cd as well as of major elements such as Si, Al, Fe and Mn was assessed by means of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Soil microorganisms have proven to decrease mineral weathering by reducing the concentration of active root exudates in solution. Results obtained are an important cornerstone to better understand the biogeochemical processes acting in the rhizosphere which can play an important role in the availability of trace elements (either nutrient or toxic) for plant uptake. Research is supported by MIUR - FIRB "Futuro in ricerca", internal grant of Unibz (TN5031 & TN5046) and the Autonomous Province of Bolzano (Rhizotyr TN5218).

  6. Soil Carbon and Nitrogen Mineralization with Flexible Soil and Microbial C:N Ratios

    NASA Astrophysics Data System (ADS)

    Wang, G.; Mayes, M. A.; Thornton, P. E.; Hoffman, F. M.

    2014-12-01

    Microbial assimilation of C-N and the physicochemical protection of soil organic matter (SOM) play fundamental roles in regulating land-atmosphere interactions. However, these microbial and physicochemical processes are not explicitly represented in current region/global terrestrial ecosystem models, e.g., the Community Land Model (CLM). The lack of explicit representation of microbial pools and functions results in unrealistic fixed-C:N ratios in SOM pools currently in CLM. Thus current soil C-N model configuration is inadequate to model the effects of litter inputs or fertilization on soil carbon and nitrogen mineralization and linkages between plant litter C:N ratios and soil or microbial C:N ratios. We propose a coupled C-N model that allows for flexible C:N ratios in microbe and SOM pools and thus the ability to represent the decomposition response to fertilization and/or litter inputs with various C:N ratios. Our preliminary analysis has shown that the C:N ratios in SOM, dissolved organic matter (DOM), and microbial pools can be well constrained by the new C-N model and microbes regulate the C:N ratios in SOM and DOM pools. We will use this new model framework to evaluate the soil carbon and nitrogen mineralization processes under conditions of excess organic C, excess organic N, or limited mineral N.

  7. 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.

  8. Changes in Soil Minerology Reduce Phosphorus Mobility During Anoxic Soil Conditions

    NASA Astrophysics Data System (ADS)

    Giri, S. K.; Geohring, L. D.; Richards, B. K.; Walter, M.; Steenhuis, T. S.

    2008-05-01

    Phosphorus (P) transfer from the landscape to receiving waters is an important environmental concern because these diffuse losses may cause widespread water quality impairments which can accelerate freshwater eutrophication. Phosphorus (P) mobilization from soil to surface and subsurface flow paths is controlled by numerous factors, and thus it can vary greatly with time and landscape scale. To determine whether P mobilization during soil saturation in the landscape was caused or controlled by complexation, iron reduction or ligand exchange, experiments were carried out to better characterize the interrelationships of varying P sources with dissolved organic carbon (DOC) and soil anoxic conditions. The soil incubation experiments consisted of treatments with distilled water, 5 mM acetic acid (HAc), 0.05% humic acid (HA) and glucose (40 mM) at 26 o C under anaerobic conditions to isolate effects of the various P exchange processes. The experimental results suggest that during soil saturation, the loosely bound P, which is primarily associated with iron oxyhydroxides, was mobilized by both reduction and complexation processes. Good correlations were observed between ferrous iron (Fe+2) and DOC, and between total dissolved phosphorus (TDP) and DOC, facilitating P desorption to the soil water. The anaerobic soil conditions with different P sources also indicated that mineralization facilitated P mobility, mainly due to chelation (humics and metabolites) and as a result of the bio-reduction of iron when fresh litter and grass were present. The organic P sources which are rich in carbohydrate and cellulose and that undergo fermentation due to the action of lactate forming organisms also caused a release of P. The easily metabolizable DOC sources lead to intensive bio-reduction of soil with the release of Fe, however this did not necessarily appear to cause more TDP in the soil solution. The varying P additions in soils with water, HAc and glucose (40mm) before and after soil incubation showed higher P sorption than aerobic soil due to reduced iron (Fe+2) - P mineral formation. Some of the readily available P in the soil solution tended to co-precipitate quickly with Fe, Al, Ca, and Mn, but it also resulted in the formation of earthy masses of vivianite [Fe2+3(PO4)2 . 8 H20], thus almost completely immobilizing P. These findings suggest that where conditions in the landscape are saturated, but remain stagnant for extended time periods, P additions may not necessarily enhance leaching once hydrological transport resumes. The temporal nature of P mobilization processes combined with rapid (i.e., preferential flow) hydrological transport appears to have a more important role in controlling P transport through the landscape.

  9. Does plant uptake or low soil mineral-N production limit mineral-N losses to surface waters and groundwater from soils under grass in summer?

    PubMed

    Bhatti, Ambreen; McClean, Colin J; Cresser, Malcolm S

    2013-07-01

    Summer minima and autumn/winter maxima in nitrate concentrations in rivers are reputedly due to high plant uptake of nitrate from soils in summer. A novel alternative hypothesis is tested here for soils under grass. By summer, residual readily mineralizable plant litter from the previous autumn/winter is negligible and fresh litter input low. Consequently little mineral-N is produced in the soil. Water-soluble and KCl-extractable mineral N in fresh soils and soils incubated outdoors for 7 days have been monitored over 12 months for soil transects at two permanent grassland sites near York, UK, using 6 replicates throughout. Vegetation-free soil is shown to produce very limited mineral-N in summer, despite the warm, moist conditions. Litter accumulates in autumn/winter and initially its high C:N ratio favours N accumulation in the soil. It is also shown that mineral-N generated monthly in situ in soil substantially exceeds the monthly mineral-N inputs via wet deposition at the sites. PMID:23562960

  10. COMPARISON OF NUTRIENT SOURCES OF MINERAL SOIL NUTRITION IN FLORIDA SUGARCANE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improving soil organic matter and soil fertility are important factors in the sustainability of sugarcane production on mineral soils. A trial was established in 2004 on a sandy Spodosol in Florida to compare the effect of organic and inorganic nutrient sources on soil fertility and sugarcane produ...

  11. Carbon mineralization and microbial biomass in soil aggregates from two tillage systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil quality is a concept of many interrelated factors that perform in concert to improve soil productivity. Few of the factors for soil quality are microbial biomass, soil aggregate fractions, and carbon mineralization in different aggregate fractions that are influenced by the agricultural practic...

  12. [Seasonal dynamics of soil net nitrogen mineralization under moss crust in Shapotou region, northern China].

    PubMed

    Hu, Rui; Wang, Xin-ping; Pan, Yan-xia; Zhang, Ya-feng; Zhang, Hao; Cheng, Ning

    2015-04-01

    Seasonal variations of soil inorganic nitrogen (N) pool and net N transformation rate in moss-covered soil and in the bare soil were comparatively observed by incubating intact soil columns with parafilm capping in the field in a natural vegetation area of Shapotou, southeastern fringe of the Tengger Desert. We found pronounced seasonal variations in soil available N content and net N transformation rate in both moss-covered soil and bare soil, with significant differences among different months. In non-growing season, soil available N content and net N transformation rate were significantly higher in March and October than in other months. Furthermore, immobilization was the dominant form of N mineralization, and no significant difference in net soil N mineralization rate was found between the two sampling soils. In growing season, soil available N content and net N transformation rate markedly increased and reached their peak values during June to August (17.18 mg x kg(-1) and 0.11 mg x kg(-1) x d(-1), respectively). Both soil net nitrification and N mineralization rates in moss-covered soil were significantly higher than in bare soil. Soil ammonium and nitrate N content in April and May were higher in moss-covered soil (2.66 and 3.16 mg x kg(-1), respectively) than in bare soil (1.02 and 2.37 mg x kg(-1), respectively); while the tendency was the converse in June and September, with 7.01 mg x kg(-1) for soil ammonium content and 7.40 mg x kg(-1) for nitrate N content in bare soil, and they were 6.39 and 6.36 mg x kg(-1) in moss-covered soil, respectively. Therefore, the existence and succession of moss crusts could be considered as one of the important biological factors affecting soil N cycling through regulating soil available N content and promoting soil N mineralization process. PMID:26259453

  13. Statistical analysis of mineral soils in the Odra valley

    NASA Astrophysics Data System (ADS)

    Hudak, Magda; Rojna, Arkadiusz

    2012-10-01

    The aim of this article is to present the results of statistical analyses of laboratory experiment results obtained from an ITB ZW-K2 apparatus, Kamieński tubes and grain-size distribution curves. Beside basic statistical parameters (mean, sum, minimum and maximum), correlation analysis and multivariate analysis of variance at significance levels α < 0.01 and α < 0.05 were taken into account, as well as calculations of LSD confidence half-intervals. The research material was collected from the valley of the Odra river near the town of Słubice in Lubuskie province. The research involved mineral, non-rock fine-grained, non-cohesive soils lying at the depth of 0.3-1.5 m.

  14. Kinetics of di-(2-ethylhexyl)phthalate mineralization in sludge-amended soil

    SciTech Connect

    Madsen, P.L.; Thyme, J.B.; Henriksen, K.; Moeldrup, P.; Roslev, P. . Environmental Engineering Lab.)

    1999-08-01

    Sewage sludge is frequently used as a soil fertilizer although it may contain elevated concentrations of priority pollutants including di-(2-ethylhexyl)phthalate (DEHP). In the present study, the kinetics of microbial [[sup 14]C]DEHP mineralization was studied in laboratory microcosms with sewage sludge and agricultural soil. A biphasic model with two independent kinetic expressions was used to fit the mineralization data. The initial mineralization activity was described well by first-order kinetics, whereas mineralization in long-term incubations was described better by fractional power kinetics. The mineralization activity was much lower in the late phase presumably due to a decline in the bioavailability of DEHP caused by diffusion-limited desorption. The initial DEHP mineralization rate in sludge-amended soil varied between 3.7 and 20.3 ng of DEHP (g dw)[sup [minus]1]d[sup [minus]1] depending on incubation conditions. Aerobic DEHP mineralization was 4--5 times faster than anaerobic mineralization, DEHP mineralization in sludge-amended soil was much more temperature sensitive than was DEHP mineralization in soil without sludge. Indigenous microorganisms in the sewage sludge appeared to dominate DEHP degradation in sludge-amended soil. It was estimated that > 41% of the DEHP in sludge-amended soil will have escaped mineralization after 1 year. In the absence of oxygen, > 68% of the DEHP will not be mineralized within 1 year. Collectively, the data suggest that a significant fraction of the DEHP in sludge-amended soils may escape mineralization under in situ conditions.

  15. Soil quality assessment for peat-mineral mix cover soil used in oil sands reclamation.

    PubMed

    Ojekanmi, A A; Chang, S X

    2014-09-01

    A soil quality (SQ) assessment and rating framework that is quantitative, iterative, and adaptable, with justifiable weighting for quality scores, is required for evaluating site-specific SQ at land reclamation sites. Such a framework needs to identify the minimum dataset that reflects the current knowledge regarding relationships between SQ indicators and relevant measures of ecosystem performance. Our objective was to develop nonlinear scoring functions for assessing the impact on SQ of peat-mineral mix (PMM) used as a cover soil at land reclamation sites. Soil functional indicators affected by PMM were extracted from existing databases and correlated with soil organic carbon (SOC). Based on defined objectives for SQ assessment, indicators with significant correlation ( < 0.05) to SOC were selected, normalized, and fitted to sigmoid functions using nonlinear regression procedure to establish SQ functions (SQFs) that can analyze changes in field capacity, permanent wilting point, soil nitrogen, and cation exchange capacity of PMM using SOC as input parameter. Application of the SQFs to an independent dataset produced ratings with mean differences similar to the treatment effects of mixing three levels of peat and mineral soil. These results show that derived ratings and weighing factors using SOC reflect the relationship between PMM treatment and other SQ indicators. Applying the developed SQFs to a long-term soil monitoring dataset shows that an increase or decrease in SOC from 10 to 20 g kg causes a significant change in SQ. This identifies the need for further nutrient and moisture management of PMM to support long-term SQ development in land reclamation. PMID:25603242

  16. LONG-TERM URANIUM MIGRATION IN AGRICULTURAL FIELD SOILS FOLLOWING MINERAL P FERTILIZATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To preserve soil fertility, organic and mineral fertilizers are often applied to agricultural fields. Mineral fertilizers such as phosphates and super phosphates contain a certain amount of long-lived alpha activity due to 238-U, 230-Th, amongst others. The fate of U in soil systems is quite complex...

  17. SIMULTANEOUS INHIBITION OF CARBON AND NITROGEN MINERALIZATION IN A FOREST SOIL BY SIMULATED ACID PRECIPITATION

    EPA Science Inventory

    Acid Precipitation may alter the rates of microbial processes in soil that are important for forest productivity. Acidification of soil can result in a depression of carbon mineralization. The present study was designed to determine whether the inhibition of carbon mineralization...

  18. Soil and plant minerals associated with rice straighthead disorder induced by arsenic

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Application of arsenic (As) as monosodium methanearsonate (MSMA) to soil has become the common practice for evaluation of rice straighthead, a physiological disorder. So far, no study has reported on soil mineral availability and plant mineral uptake as affected by the MSMA straighthead evaluation. ...

  19. Ex situ bioremediation of mineral oil in soils: Aerated pile treatment. Final report

    SciTech Connect

    Graves, D.

    1998-04-01

    Under a contract with Southern Company Services, a pilot-scale evaluation of mineral oil biodegradation was conducted at Plant Mitchell. The evaluation consisted of two demonstrations to examine land treatment and aerated pile treatment of soil contaminated with the mineral insulating oil used in electrical transformers. Treatment of mineral oil contaminated soil is problematic in the State of Georgia and throughout the US because current practice is to excavate and landfill the contaminated soil. In many cases, the cost associated with these activities far exceeds the environmental risk of mineral oil in soil. This project was designed to evaluate the performance of bioremediation for the treatment of mineral oil in soil. Testing was carried out in a demonstration facility prepared by Georgia Power Company. The facility consisted of 12 independent treatment cells constructed on a concrete pad and covered with a roof.

  20. Indigenous and enhanced mineralization of pyrene, benzo[a]pyrene, and carbazole in soils.

    PubMed Central

    Grosser, R J; Warshawsky, D; Vestal, J R

    1991-01-01

    We studied the mineralization of pyrene, carbazole, and benzo[a]pyrene in soils obtained from three abandoned coal gasification plants in southern Illinois. The soils had different histories of past exposure to hydrocarbon contamination and different amounts of total organic carbon, microbial biomass, and microbial activity. Mineralization was measured by using serum bottle radiorespirometry. The levels of indigenous mineralization of 14C-labeled compounds ranged from 10 to 48% for pyrene, from undetectable to 46% for carbazole, and from undetectable to 25% for benzo[a]pyrene following long-term (greater than 180-day) incubations. Pyrene and carbazole were degraded with short or no lag periods in all soils, but benzo[a]pyrene mineralization occurred after a 28-day lag period. Mineralization was not dependent on high levels of microbial biomass and activity in the soils. Bacterial cultures that were capable of degrading pyrene and carbazole were isolated by enrichment, grown in pure culture, and reintroduced into soils. Reintroduction of a pyrene-degrading bacterium enhanced mineralization to a level of 55% within 2 days, compared with a level of 1% for the indigenous population. The carbazole degrader enhanced mineralization to a level of 45% after 7 days in a soil that showed little indigenous carbazole mineralization. The pyrene and carbazole degraders which we isolated were identified as a Mycobacterium sp. and a Xanthamonas sp., respectively. Our results indicated that mineralization of aromatic hydrocarbons can be significantly enhanced by reintroducing isolated polycyclic aromatic hydrocarbon-degrading bacteria. PMID:1785924

  1. Adsorption and structural fractionation of dissolved organic matter (DOM) by soil mineral surfaces

    NASA Astrophysics Data System (ADS)

    Avneri, Shani; Polubesova, Tamara; Chefetz, Benny

    2015-04-01

    Dissolved organic matter (DOM) represents a small but highly reactive fraction of the soil organic matter (SOM). One of the important processes affecting the fate of DOM in soils is its interactions with mineral phases. Adsorptive fractionation of DOM by soils and minerals has been observed previously, however detailed changes in composition of DOM due to its interactions with mineral soils were not yet elucidated. In this research the adsorption and physico-chemical fractionation of DOM by soil poor with organic matter and rich with iron oxides and clay fraction was investigated. The changes in DOM structural composition were studied using separation with polymeric resins. The following fractions were obtained: hydrophobic acid (HoA), hydrophobic neutral (HoN), hydrophilic acid (HiA), hydrophilic base (HiB), and hydrophilic neutral (HiN). Two types of DOM were studied: DOM extracted from composted biosolids (compost DOM) and DOM from Suwanee River (SRNOM). Sorption affinity of DOM to soil mineral surfaces was source and chemistry dependent. SRNOM, which was characterized by higher content of aromatic and carboxylic groups demonstrated higher affinity to the studied soil than compost DOM. For both DOM samples preferential adsorption of HoA by soil (50-85% from adsorbed carbon) was observed. Desorption of both DOM types demonstrated significant hysteresis (up to 90-100% of dissolved organic carbon was retained by the soil after 3 cycles of desorption stages). This suggests that DOM desorption behavior was affected by HoA dominant adsorption to the soil mineral fraction, and not by DOM source. Results of this study indicate that interactions of different types of DOM with mineral soil may result in similar changes in composition and properties of DOM both in the supernatant as well as in the adsorbed phase. The change in DOM composition due to its interaction with soil minerals may influence the interactions of pollutants with DOM and soil particle surfaces.

  2. [Compositional characteristics and roles of soil mineral substances in depressions between hills in karst region].

    PubMed

    Han, Mei-Rong; Song, Tong-Qing; Peng, Wan-Xia; Huang, Guo-Qin; Du, Hu; Lu, Shi-Yang; Shi, Wei-Wei

    2012-03-01

    Based on the investigation and analysis of seven soil mineral substance variables, nine vegetation factors, four topographical factors, and ten soil physicochemical factors in the 200 m x 40 m dynamic monitoring plots in farmland, forest plantation, secondary forest, and primary forest in the depressions between hills in karst region, and by using traditional statistical analysis, principal component analysis (PCA), and canonical correlation analysis (CCA), this paper studied the compositional characteristics and roles of soil mineral substances as well as the coupling relationships between the mineral substances and the vegetation, topography, and other soil properties. In the depressions, soil mineral substances were mainly composed of SiO2, Al2O3, K2O, and Fe2O3, whose contents were obviously lower than the mean background values of the soils in the world and in the zonal red soils at the same latitudes. The soil CaO and MgO contents were at medium level, while the soil MnO content was very low. The composition of soil mineral substances and their variation degrees varied with the ecosystems, and the soil development degree also varied. There was a positive correlation between vegetation origin and soil origin, suggesting the potential risk of rock desertification. Due to the high landscape heterogeneity of the four ecosystems, PCA didn't show good effect in lowering dimension. In all of the four ecosystems, soil mineral substances were the main affecting factors, and had very close relationships with vegetation, topography, and other soil properties. Especially for SiO2, CaO, and MnO, they mainly affected the vegetation species diversity and the soil organic matter, total nitrogen, and total potassium. This study indicated that soil mineral substances were the one of the factors limiting the soil fertility and vegetation growth in the depressions between hills in karst region. To effectively use the soil mineral resources and rationally apply mineral nutrients would have significances in the restoration and reconstruction of karst degraded ecosystems. PMID:22720612

  3. Bioinduced weathering in Swedish boreal forest soil investigated by mineral amendment

    NASA Astrophysics Data System (ADS)

    Olofsson, Madelen; Ahmed, Engy; Bylund, Dan; Holmstrm, Sara

    2013-04-01

    The purpose of this study was to investigate how soil mineral amendment affects microbial composition and how different mineral composition and varied depth influence these changes. Apatite, biotite and oligoclase were placed at soil horizon interfaces in a podzole in Bispgrden, central Sweden (6307'N, 1670'E), between the summer of 2009 and 2011. Continuous measurement of soil chemistry; pH, dissolved organic carbon (DOC) and low molecular mass organic acids (LMMOAs) was performed for the surrounding soil during the frost free months of the two-year incubation period. Mineral sample surfaces were investigated using scanning electron microscopy (SEM) pre and post soil incubation to give a visual verification of weathering effects. Evaluating soil chemistry data and data received at the end of the incubation period, results show that the highest concentration of LMMOAs is found in the E horizon and that it corresponds with the highest total fungal activity in the bulk soil. Total microbial activity was found to be highest in the O horizon. Measurements on the soil of the mineral surfaces show that in all cases, apatite stimulates the microbial activity the most, followed by biotite and last oligoclase. Comparing the soil horizons, effects on total microbial activity are the highest in the E horizon, but when looking at total fungal activity the biggest changes are found in O and B horizon indicating that bacterial and fungal activities are affected differently by mineral amendment. Using ANOVA followed by pair wise comparisons according to Tukey, significant differences were found in microbial activity between the soil horizons and also between most of the different minerals, compared with the bulk soil. Looking at the SEM images taken before and after weathering, minerals placed in the O and E horizon are clearly the most affected, and the magnitude of weathering between the different minerals corresponds to the microbial activity found.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Fernndez-Calvio, David; Rodrguez-Salgado, Isabel; Prez-Rodrguez, Paula; Daz-Ravia, Montserrat; Nvoa-Muoz, Juan Carlos; Arias-Estvez, 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.

  6. [Characteristics of organic nitrogen mineralization in organic waste compost-amended soil].

    PubMed

    Zhang, Xu; Xi, Bei-Dou; Zhao, Yue; Wei, Zi-Min; Li, Yang; Zhao, Xin-Yu

    2013-06-01

    A laboratory aerobic incubation experiment was conducted under a constant temperature to investigate the differentiation rule of nitrogen form among soils amended with different organic wastes composted with food waste, chicken manure, cow manure, domestic waste, vegetable residue, sludge, turf and tomato residue. Experiment utilized soils amended with 0%, 5% and 50% (m/m) of eight organic waste composts. The purpose was to understand the effect of different organic wastes on nitrogen mineralization in soil. This study deals with eight organic waste compost treatments could rapidly increase NH4(+) -N concentrations, reduce the NO3(-)-N concentrations and promote nitrogen mineralization in soil after 3-4 weeks incubation. All parameter tended to be stable. The improved amplitude of the same compost-amended soil: 30% compost treatments > 15% compost treatments > 5% compost treatments. Within the same proportion, chicken manure compost, turf compost and sludge compost product treatments' relative N mineralization was higher than other compost product treatments, and the chicken manure compost treatment's relative N mineralization was significantly higher than other compost product treatments. Food waste compost and vegetable residue compost product treatments' mineralization was low, the lowest was domestic waste compost product treatment. All compost treatments could significantly improve the values of potentially mineralizable nitrogen(N(0)), mineralization rate (k), and promote nitrogen mineralization in soil. The results illustrated that the effect of organic waste compost on the mineralization of nitrogen varied with types of compost and the amount of input compost. PMID:23947069

  7. 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.

  8. 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.

  9. Minerals

    MedlinePLUS

    Minerals are important for your body to stay healthy. Your body uses minerals for many different jobs, including building bones, making ... regulating your heartbeat. There are two kinds of minerals: macrominerals and trace minerals. Macrominerals are minerals your ...

  10. Changes in mineral soil biogeochemical cycling and environmental conditions following tree harvest in the Northeast

    NASA Astrophysics Data System (ADS)

    Vario, C.; Friedland, A.

    2012-12-01

    In the northeastern United States, reductions in carbon dioxide emissions have been attempted by using local wood as a renewable alternative to oil. Although woody biomass products are readily available, recent findings suggest that forest disturbance may cause release of carbon from the deeper mineral soil. Worldwide, deep soils sequester more than half of soil carbon, making it critical in the global carbon cycle; however, most studies on the effect of harvesting have focused on the organic soil horizon. Our research aimed to uncover changes in biogeochemistry and environmental conditions in deeper, mineral soil after clear cutting forests. We quantified post-harvest mineral soil carbon pools through a regional study. We utilized stands of different ages to measure the recovery of soil carbon over time since harvest. Stands included in this study were cut approximately 5, 12, 25, 50, or 120 ybp, in order to identify changes in soil carbon over time since harvest. We sampled harvested stands in six research or protected forests across New York, New Hampshire, Massachusetts, and Vermont. Soil samples were collected to a depth of 60 cm below the surface of the mineral soil using a gas-powered augur and 9.5 cm diameter drill bit. Soil samples were analyzed at Dartmouth College. In order to understand specific changes in mineral soil carbon dynamics following harvest, measurements of carbon fluxes, such as soil respiration and DOC transport were conducted at five different-aged stands at Bartlett Experimental Forest, NH. While parameters that may influence carbon storagesuch as pH, clay content, tree cover and elevation did not vary across the different-aged stands in each forest, carbon pools did vary over time. We found changes in carbon pools in at least three experimental forests across the northeast. At Bartlett Experimental Forest, we found a gradual decline in mineral soil carbon storage from between 85-87 Mg ha-1 in 120 year old and primary forest stands to a minimum of 53 Mg ha-1 in the 75 year old stand. In our carbon flux measurements, we observed higher DOC concentrations in lysimeter samples collected at 30 cm at 12 years after harvest. We have also documented consistently higher soil temperatures across summer months at 50 cm below the mineral soil in the recently clear-cut site at Bartlett Experimental Forest. These changes in biogeochemical and environmental conditions suggest that forest clearing does affect mineral soil, and our findings may help identify a mechanism to explain the observed carbon loss from soils in clear-cut forests.

  11. 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]).

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

    PubMed

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

    1996-12-01

    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]). PMID:11539387

  13. Technical Note: Minerals in dust productive soils - impacts and global distribution

    NASA Astrophysics Data System (ADS)

    Nickovic, S.; Vukovic, A.; Vujadinovic, M.; Djurdjevic, V.; Pejanovic, G.

    2011-09-01

    Dust storms and associated mineral aerosol transport are mainly driven by meso and synoptic scale atmospheric processes. It is therefore essential that the dust aerosol process and background atmospheric conditions that drive the dust emission and atmospheric transport be represented with sufficiently well resolved spatial and temporal features. Effects of airborne dust interactions with the environment are determent by the mineral composition of dust particles. Fractions of various minerals in the aerosol are determined by the mineral composition of arid soils, therefore high-resolution specification of mineral and physical properties of dust sources is needed as well. Most current dust atmospheric models simulate/predict the evolution of dust concentration but in most cases they do not consider fractions of minerals in dust. Accumulated knowledge on impacts of mineral composition in dust on weather and climate processes emphasizes the importance of considering minerals in modelling systems. Following such needs, in this study we developed a global dataset on mineral composition of potentially dust productive soils. In our study (a) we mapped mineral data into a high-resolution 30-s grid, (b) we included mineral carrying soil types in dust productive regions that were not considered in previous studies, and (c) included phosphorus having in mind their importance for terrestrial and marine nutrition processes.

  14. Mineralization of polycyclic and n-heterocyclic aromatic compounds in hydrocarbon-contaminated soils

    SciTech Connect

    Grosser, R.J.; Warshawsky, D.; Vestal, J.R.

    1995-03-01

    The comparative mineralization of eight polycyclic aromatic compounds in five soils collected from an abandoned coal tar refinery in eastern Ohio was determined. The soils showed differences only in total extractable hydrocarbon content of the soil chemical characteristics measured. The compounds studied included five polycyclic aromatic hydrocarbons (phenanthrene, anthracene, pyrene, and carcinogenic benz[a]anthracene and benzo[a]pyrene) and three N-heterocyclic aromatics (9H-carbazole, and carcinogenic 7H-dibenzo[c,g]carbazole and dibenz[a,j]acridine). Mineralization was measured by serum bottle radiorespirometry. Only phenanthrene, anthracene, pyrene, benz[a]anthracene, and carbazole were mineralized in the soils after 64 d. Two of the soils with eight to 15 times the hexane -extractable hydrocarbon content consistently showed more rapid initial rates and higher overall extents of mineralization compared to the other three soils. Overall extents of mineralization ranged from 38 to 55% for phenanthrene, 10 to 60% for anthracene, 25 to 70% for pyrene, background to 40% for benz[a]anthracene, and 25 to 50% for carbazole after 64 d. Extents of mineralization by indigenous soil microbiota appear to be more dependent on the chemical characteristics of the soil and not soil total biomass and activity. Cultures capable of degrading phenanthrene, anthracene, and pyrene were obtained following enrichment techniques. A Mycobacterium sp. capable of degrading these three compounds was isolated and reintroduced into two of the soils, resulting in mineralization enhanced above that of the indigenous soil microbial population. These data indicate that the future success of bioremediation methods relies on the characterization of environmental parameters affecting microbial degradation as well as the isolation of microbial populations that can reduce toxicity in the environment.

  15. Magnetic beneficiation of highland and hi-Ti mare soils - Rock, mineral, and glassy components

    NASA Technical Reports Server (NTRS)

    Taylor, Lawrence A.; Oder, Robin R.

    1990-01-01

    The exploitation of lunar soil can provide valuable raw materials for in situ resource utilization at a lunar base. A study of magnetic characterization was undertaken of three mare and two highland soils obtained from NASA. Beneficiation of mare and highland soils by sizing and magnetic separation can effectively concentrate the important components of the soils (e.g., ilmenite, native Fe, plagioclase, and aggluminates). As a soil matures and the impact melts consume additional minerals and rocks, the modal percentage of the minerals will decrease. The 'normative' percentage will become much greater than the modal percentage. Therefore, greater efficiency of separation can be realized with the proper selection of maturity of the soil, as well as by secondary grinding to further liberate specific minerals from lithic fragments (e.g., ilmenite and plagioclase).

  16. 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.

  17. 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 35C 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 25-35C 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. PMID:23342038

  18. Depth-Dependent Mineral Soil CO2 Production Processes: Sensitivity to Harvesting-Induced Changes in Soil Climate.

    PubMed

    Kellman, Lisa; Myette, Amy; Beltrami, Hugo

    2015-01-01

    Forest harvesting induces a step change in the climatic variables (temperature and moisture), that control carbon dioxide (CO2) production arising from soil organic matter decomposition within soils. Efforts to examine these vertically complex relationships in situ within soil profiles are lacking. In this study we examined how the climatic controls on CO2 production change within vertically distinct layers of the soil profile in intact and clearcut forest soils of a humid temperate forest system of Atlantic Canada. We measured mineral soil temperature (0, 5, 10, 20, 50 and 100 cm depth) and moisture (0-15 cm and 30-60 cm depth), along with CO2 surface efflux and subsurface concentrations (0, 2.5, 5, 10, 20, 35, 50, 75 and 100 cm depth) in 1 m deep soil pits at 4 sites represented by two forest-clearcut pairs over a complete annual cycle. We examined relationships between surface efflux at each site, and soil heat, moisture, and mineral soil CO2 production. Following clearcut harvesting we observed increases in temperature through depth (1-2°C annually; often in excess of 4°C in summer and spring), alongside increases in soil moisture (30%). We observed a systematic breakdown in the expected exponential relationship between CO2 production and heat with mineral soil depth, consistent with an increase in the role moisture plays in constraining CO2 production. These findings should be considered in efforts to model and characterize mineral soil organic matter decomposition in harvested forest soils. PMID:26263510

  19. Depth-Dependent Mineral Soil CO2 Production Processes: Sensitivity to Harvesting-Induced Changes in Soil Climate

    PubMed Central

    Kellman, Lisa; Myette, Amy; Beltrami, Hugo

    2015-01-01

    Forest harvesting induces a step change in the climatic variables (temperature and moisture), that control carbon dioxide (CO2) production arising from soil organic matter decomposition within soils. Efforts to examine these vertically complex relationships in situ within soil profiles are lacking. In this study we examined how the climatic controls on CO2 production change within vertically distinct layers of the soil profile in intact and clearcut forest soils of a humid temperate forest system of Atlantic Canada. We measured mineral soil temperature (0, 5, 10, 20, 50 and 100 cm depth) and moisture (0–15 cm and 30–60 cm depth), along with CO2 surface efflux and subsurface concentrations (0, 2.5, 5, 10, 20, 35, 50, 75 and 100 cm depth) in 1 m deep soil pits at 4 sites represented by two forest-clearcut pairs over a complete annual cycle. We examined relationships between surface efflux at each site, and soil heat, moisture, and mineral soil CO2 production. Following clearcut harvesting we observed increases in temperature through depth (1–2°C annually; often in excess of 4°C in summer and spring), alongside increases in soil moisture (30%). We observed a systematic breakdown in the expected exponential relationship between CO2 production and heat with mineral soil depth, consistent with an increase in the role moisture plays in constraining CO2 production. These findings should be considered in efforts to model and characterize mineral soil organic matter decomposition in harvested forest soils. PMID:26263510

  20. [Effects of variable temperature on organic carbon mineralization in typical limestone soils].

    PubMed

    Wang, Lian-Ge; Gao, Yan-Hong; Ding, Chang-Huan; Ci, En; Xie, De-Ti

    2014-11-01

    Soil sampling in the field and incubation experiment in the laboratory were conducted to investigate the responses of soil organic carbon (SOC) mineralization to variable temperature regimes in the topsoil of limestone soils from forest land and dry land. Two incubated limestone soils were sampled from the 0-10 cm layers of typical forest land and dry land respectively, which were distributed in Tianlong Mountain area of Puding county, Guizhou province. The soils were incubated for 56 d under two different temperature regimes including variable temperature (range: 15-25 degrees C, interval: 12 h) and constant temperature (20 degrees C), and the cumulative temperature was the same in the two temperature treatments. In the entire incubation period (56 d), the SOC cumulative mineralization (63.32 mg x kg(-1)) in the limestone soil from dry land (SH) under the variable temperature was lower than that (63.96 mg x kg(-1)) at constant 20 degrees C, and there was no significant difference in the SOC cumulative mineralization between the variable and constant temperature treatments (P < 0.05). While the cumulative mineralization (169.46 mg x kg(-1)) of organic carbon in the limestone soil from forest land (SL) under the variable temperature was significantly lower than that (209.52 mg x kg(-1)) at constant 20 degrees C. The results indicated that the responses of SOC mineralization to the variable temperature were obviously different between SL and SH soils. The SOC content and composition were significantly different between SL and SH soils affected by vegetation and land use type, which suggested that SOC content and composition were important factors causing the different responses of SOC mineralization to variable temperature between SL and SH soils. In addition, the dissolved organic carbon (DOC) content of two limestone soils were highly (P < 0.01) positively correlated with daily mineralization of soil organic carbon in both temperature treatments, which implied that controlling DOC production was an important way for the temperature influence of SOC mineralization. During the incubation period, SOC mineralization was independent of microbial biomass carbon (MBC) content in both temperature treatments. Combined with mineralization kinetic data, the results showed that, compared to constant temperature 20 degrees C, variable temperature mainly influenced SOC mineralization by changing microbial community activity rather than by changing microbial quantity. PMID:25639108

  1. Spatial Arrangment of Organic Compounds on a Model Mineral Surface: Implications for Soil Organic Matter Stabilization

    SciTech Connect

    Petridis, Loukas; Ambaye, Haile Arena; Jagadamma, Sindhu; Kilbey, S. Michael; Lokitz, Bradley S; Lauter, Valeria; Mayes, Melanie

    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

  2. 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.

  3. DYNAMICS OF MINERAL STRUCTURES AND THE FATE OF METALS IN SOILS AND SEDIMENTS

    EPA Science Inventory

    Significant progress has been made in elucidating sorption reactions that control the partitioning of metals from solution to mineral surfaces in contaminated soil/sediment systems. Surface complexation models have been developed to quantify the forward reaction with reasonable ...

  4. Minerals

    MedlinePLUS

    ... Sledding, Skiing, Snowboarding, Skating Crushes What's a Booger? Minerals KidsHealth > For Kids > Minerals Print A A A Text Size What's in ... commercials for breakfast cereal always mention vitamins and minerals ? But when you think of minerals, food isn' ...

  5. Clay mineralogy of weathering rinds and possible implications concerning the sources of clay minerals in soils.

    USGS Publications Warehouse

    Colman, Steven M.

    1982-01-01

    Weathering rinds on volcanic clasts in Quaternary deposits in the western US contain only very fine-grained and poorly crystalline clay minerals. Rinds were sampled from soils containing well-developed argillic B horizons in deposits approx 105 yr old or more. The clay-size fraction of the rinds is dominated by allophane and iron hydroxy-oxides, whereas the B horizons contain abundant well-crystallized clay minerals. The contrast between the clay mineralogy of the weathering rinds, in which weathering is isolated from other soil processes, and that of the associated soil matrices suggests a need to reassess assumptions concerning the rates at which clay minerals form and the sources of clay minerals in argillic B horizons. It seems that crystalline clay minerals form more slowly in weathering rinds than is generally assumed for soil environments and that the weathering of primary minerals may not be the dominant source of crystalline clay minerals in Middle to Late Pleistocene soil.-A.P.

  6. 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.

  7. 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.

  8. 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…

  9. 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...

  10. 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

  11. 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.

  12. 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

  13. 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. PMID:26647157

  14. How relevant is chemical recalcitrance for predicting climatic effects on mineral soil carbon stocks?

    NASA Astrophysics Data System (ADS)

    Hopkins, F. M.; Torn, M. S.; Trumbore, S.

    2011-12-01

    The role of chemical recalcitrance in mediating the effect of warming on soil carbon stocks has been a focus of research efforts aimed toward the larger goal of prediction of carbon loss from soils in the 21st century. Arrhenius kinetics provides a theoretical basis for the prediction that reaction of chemically recalcitrant carbon compounds (those with higher activation energy) should be more temperature sensitive than compounds with faster turnover rates (lower activation energy). This relationship has even been integrated into models of soil carbon dynamics. However, since chemically recalcitrant compounds have, by definition, slower turnover rates, their response to warming should ultimately be far smaller than those of faster turnover compounds in terms of overall respiratory loss (Sierra 2011). Regardless of the relative temperature sensitivity of recalcitrant soil carbon, it remains an open question how important enhanced decomposition of chemically recalcitrant carbon in mineral soils is for potential feedbacks between warming and soil carbon stocks. To lend insight to this question, we present a series of incubation warming experiments with soils from two forest Free Air CO2 Enrichment (FACE) sites. Because of the distinct carbon isotope (radiocarbon free) signature of the CO2 fumigation gas, soil carbon in elevated CO2 plots has incorporated a decade of labeled carbon. By measuring the radiocarbon signature of flux, which reflects FACE label carbon in CO2 elevated plots, and the atmospheric history of radiocarbon in CO2 control plots, we attributed warming-induced increases in flux rates to soil carbon pools of different ages. Much of our knowledge about decomposition of recalcitrant compounds comes from litter decomposition, where chemical recalcitrance is the presumed control on decomposition rates. By comparing the response of litter and mineral soils to warming, we infer the role of chemical recalcitrance in mineral soils. Flux rates from both organic and mineral soils were initially stimulated by warming, but diminished in time for the organic soils, and not for mineral soils. These data suggest different long term decomposition controls on mineral soil carbon, which may be more temperature sensitive than those acting on litter carbon over the long term. In addition, the 14C signature of respiration suggests an increase in loss of older carbon with warming in mineral soils, but not in organic soils. The absence of change in ?14C respired by organic soils suggests that the change in mineral soils is likely due to a factor other than recalcitrance. While the effects of warming on chemically recalcitrant carbon may play a role in the short term response, it is not likely contributing to the long term stimulation of fluxes from mineral soils. Ultimately, to predict the response of carbon stocks to warming, we need a more detailed understanding of the processes controlling soil carbon stabilization in mineral soils. While chemical recalcitrance may play a limited role, we need to acknowledge and account for other stabilization pathways.

  15. Food Safety Issues: Mineral fertilizers and soil amendments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fertilizers and other soil amendments are required to maintain soil fertility, but some may be naturally rich in trace elements, or contaminated. Thus, as part of the overall consideration of using fertilizers and soil amendments, one should consider the levels of trace elements present in relation...

  16. Microbial Contribution to Organic Carbon Sequestration in Mineral Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil productivity and sustainability are dependent on soil organic matter (SOM). Our understanding on how organic inputs to soil from microbial processes become converted to SOM is still limited. This study aims to understand how microbes affect carbon (C) sequestration and the formation of recalcit...

  17. SULFUR DYNAMICS IN MINERAL HORIZONS OF TWO NORTHERN HARDWOOD SOILS A COLUMN STUDY WITH 35S

    EPA Science Inventory

    Sulfur dynamics of two Spodosols were ascertained using soil columns constructed from homogenized mineral soil from northern hardwood ecosystems at the Huntington Forest (HF) in the Adirondack Mountains of New York and Bear Brook Watershed in Maine (BBWM). olumns were leached for...

  18. 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.

  19. Nitrogen Mineralization Response to Tillage Practices on Low and High Nitrogen Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In strip tillage, crop residue is left on soil surface, decreasing the contact between soil and the residue, and therefore reducing decomposition rates compared to conventional tillage methods. Decomposition rates directly affect carbon and nitrogen ratios, which can affect nitrogen mineralization r...

  20. MINERALIZATION OF NITROGEN FROM BROILER LITTER AS AFFECTED BY SOIL TEXTURE IN THE SOUTHEASTERN COASTAL PLAIN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A field study was conducted during 2004-2005 to determine nitrogen (N) mineralization of broiler litter (BL) in two Coastal Plain soils of differing texture, sandy or clayey. The soils were a Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) and a Greenville sandy clay loam (...

  1. NATIONALLY COORDINATED EVALUATION OF SOIL NITROGEN MINERALIZATION RATE USING A STANDARDIZED AEROBIC INCUBATION PROTOCOL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aerobic incubation methods have been widely used to assess soil nitrogen (N) mineralization, but standardized protocols are lacking. A silt loam soil (Catlin silt loam; fine-silty, mixed, superactive, mesic, Oxyaquic Arguidoll) was subjected to aerobic incubation at six USDA-ARS locations using a ...

  2. Composition of structural fragments and the mineralization rate of organic matter in zonal soils

    NASA Astrophysics Data System (ADS)

    Larionova, A. A.; Zolotareva, B. N.; Kolyagin, Yu. G.; Kvitkina, A. K.; Kaganov, V. V.; Kudeyarov, V. N.

    2015-10-01

    Comparative analysis of the climatic characteristics and the recalcitrance against decomposition of organic matter in the zonal soil series of European Russia, from peat surface-gley tundra soil to brown semidesert soil, has assessed the relationships between the period of biological activity, the content of chemically stable functional groups, and the mineralization of humus. The stability of organic matter has been determined from the ratio of functional groups using the solid-state 13C NMR spectroscopy of soil samples and the direct measurements of organic matter mineralization from CO2 emission. A statistically significant correlation has been found between the period of biological activity and the humification indices: the CHA/CFA ratio, the aromaticity, and the alkyl/ O-alkyl ratio in organic matter. The closest correlation has been observed between the period of biological activity and the alkyl/ O-alkyl ratio; therefore, this parameter can be an important indicator of the soil humus status. A poor correlation between the mineralization rate and the content of chemically stable functional groups in soil organic matter has been revealed for the studied soil series. At the same time, the lowest rate of carbon mineralization has been observed in southern chernozem characterized by the maximum content of aromatic groups (21% Corg) and surface-gley peat tundra soil, where an extremely high content of unsubstituted CH2 and CH3 alkyl groups (41% Corg) has been noted.

  3. A rapid and cost effective method for soil carbon mineralization under static incubations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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)...

  4. A rapid and cost effective method for soil carbon mineralization under static incubations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 (...

  5. Factors Affecting Mineral Nitrogen Transformations by Soil Heating: A Laboratory Simulated Fire Study.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two forest soils from the Sierra Nevada Mountains of California were brought into the laboratory and subjected to simulated burning in a muffle furnace at several durations, oven temperatures, and water contents. Soils were analyzed for NO3-, NH4+, mineral N, total N, total C, and C:N responses to t...

  6. A Seasonal Nitrogen Mineralization Study as Influenced by Soil Properties and Landscape Position

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An in situ study was conducted to evaluate N mineralization patterns using three different soil types located in close proximity of each other during the summer and winter months. Three Coastal Plain soils investigated were Bama (Ultisol), Lynchburg (Ultisol) and Goldsboro (Ultisol). Dairy composted...

  7. INFLUENCE OF CRY1AC TOXIN ON MINERALIZATION AND BIOAVAILABILITY OF GLYPHOSATE IN SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The impact of transgenic plants containing Bacillus thuringiensis (Bt) toxin on soil processes has received recent attention. In these studies we examined the influence of the lepidopterean Bt Cry1Ac toxin on mineralization and bioavailability of the herbicide glyphosate in two different soils. The ...

  8. Nitrogen Mineralization of Broiler Litter Applied to Southeastern Coastal Plain Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A field study was conducted to determine nitrogen (N) mineralization of broiler litter (BL) in two Coastal Plain soils of differing texture, sandy or clayey. The soils were a Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) and a Greenville sandy clay loam (clayey, kaoliniti...

  9. 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. PMID:21814815

  10. Recovery of Minerals in Martian Soils Via Supercritical Fluid Extraction

    NASA Astrophysics Data System (ADS)

    Debelak, Kenneth A.; Roth, John A.

    2001-03-01

    We are investigating the use of supercritical fluids to extract mineral and/or carbonaceous material from Martian surface soils and its igneous crust. Two candidate supercritical fluids are carbon dioxide and water. The Martian atmosphere is composed mostly of carbon dioxide (approx. 95.3%) and could therefore provide an in-situ source of carbon dioxide. Water, although present in the Martian atmosphere at only approx. 0.03%, is also a candidate supercritical solvent. Previous work done with supercritical fluids has focused primarily on their solvating properties with organic compounds. Interestingly, the first work reported by Hannay and Hogarth at a meeting of the Royal Society of London in 1879 observed that increasing or decreasing the pressure caused several inorganic salts e.g., cobalt chloride, potassium iodide, and potassium bromide, to dissolve or precipitate in supercritical ethanol. In high-pressure boilers, silica, present in most boiler feed waters, is dissolved in supercritical steam and transported as dissolved silica to the turbine blades. As the pressure is reduced the silica precipitates onto the turbine blades eventually requiring the shutdown of the generator. In supercritical water oxidation processes for waste treatment, dissolved salts present a similar problem. The solubility of silicon dioxide (SiO2) in supercritical water is shown. The solubility curve has a shape characteristic of supercritical systems. At a high pressure (greater than 1750 atmospheres) increasing the temperature results in an increase in solubility of silica, while at low pressures, less than 400 atm., the solubility decreases as temperature increases. There are only a few studies in the literature where supercritical fluids are used in extractive metallurgy. Bolt modified the Mond process in which supercritical carbon monoxide was used to produce nickel carbonyl (Ni(CO)4). Tolley and Tester studied the solubility of titanium tetrachloride (TiCl4) in supercritical CO2. They reported complete miscibility of TiCl4 with supercritical CO2 (infinite solubility). At 1500 psig, TiCl4 and CO2 form a single liquid phase below 50 C. Tolley et al. also reported on the solubility and thermodynamics of tin tetrachloride in supercritical CO2. Some of their data for TiC14 are shown. Three criteria have been suggested to predict which materials are suitable for supercritical extraction: 1) Hydrocarbons or lipophilic compounds of low molecular weight and polarity are easily extracted with supercritical CO2. 2) Compounds with polar groups are not easily extracted with supercritical CO2. 3) Separation of mixtures is facilitated if components differing mass, vapor pressure, or polarity.

  11. 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

  12. Microfluidic Leaching of Soil Minerals: Release of K+ from K Feldspar.

    PubMed

    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

  13. 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

  14. Correlation of the Abundance of Betaproteobacteria on Mineral Surfaces with Mineral Weathering in Forest Soils

    PubMed Central

    Lepleux, C.; Turpault, M. P.; Oger, P.; Frey-Klett, P.

    2012-01-01

    Pyrosequencing-based analysis of 16S rRNA gene sequences revealed a significant correlation between apatite dissolution and the abundance of betaproteobacteria on apatite surfaces, suggesting a role for the bacteria belonging to this phylum in mineral weathering. Notably, the cultivation-dependent approach demonstrated that the most efficient mineral-weathering bacteria belonged to the betaproteobacterial genus Burhkolderia. PMID:22798365

  15. Mineral Contamination from Cemetery Soils: Case Study of Zandfontein Cemetery, South Africa

    PubMed Central

    Jonker, Cornelia; Olivier, Jana

    2012-01-01

    The burial of coffins may pose an environmental and health hazard since the metals that are used in coffin-making may corrode or degrade into harmful toxins. These may leach into the surrounding soils and groundwater. Very little research has been conducted world-wide on the mineral contamination potential of cemeteries, and virtually none in South Africa. The aim of the study is to determine whether burial practices affect the mineral content of soils in cemeteries. This was done by comparing the mineral concentrations of soils within the Zandfontein Cemetery in Tshwane (Gauteng, South Africa) to those off-site as well as those in zones with high burial loads with those zones with fewer burials. Twenty three soil samples were collected from various sites on- and off-site and analyzed for 31 minerals using ICP-AES. It was found that mineral concentrations of soils within the Zandfontein Cemetery were considerably higher than those off-site. Soil samples in multiple burials blocks also have elevated metal concentrations. These excess metals are probably of anthropogenic origin associated with burial practices and could pose an environmental and human health hazard. Strict monitoring of water quality in boreholes in the vicinity of the cemetery is recommended. PMID:22470306

  16. Mineral contamination from cemetery soils: case study of Zandfontein Cemetery, South Africa.

    PubMed

    Jonker, Cornelia; Olivier, Jana

    2012-02-01

    The burial of coffins may pose an environmental and health hazard since the metals that are used in coffin-making may corrode or degrade into harmful toxins. These may leach into the surrounding soils and groundwater. Very little research has been conducted world-wide on the mineral contamination potential of cemeteries, and virtually none in South Africa. The aim of the study is to determine whether burial practices affect the mineral content of soils in cemeteries. This was done by comparing the mineral concentrations of soils within the Zandfontein Cemetery in Tshwane (Gauteng, South Africa) to those off-site as well as those in zones with high burial loads with those zones with fewer burials. Twenty three soil samples were collected from various sites on- and off-site and analyzed for 31 minerals using ICP-AES. It was found that mineral concentrations of soils within the Zandfontein Cemetery were considerably higher than those off-site. Soil samples in multiple burials blocks also have elevated metal concentrations. These excess metals are probably of anthropogenic origin associated with burial practices and could pose an environmental and human health hazard. Strict monitoring of water quality in boreholes in the vicinity of the cemetery is recommended. PMID:22470306

  17. Carbon mineralization and soil fertility at high altitude grasslands in the Bolivian Andean

    NASA Astrophysics Data System (ADS)

    Zornoza, R.; Muoz, M. A.; Faz, A.

    2012-04-01

    The high grasslands of Apolobamba provide a natural habitat for a high number of wild and domestic camelids such as vicuna (Vicugna vicugna) and alpaca (Lama pacos) in Bolivia. Because of the importance of the camelid raising for the Apolobambs inhabitant economy, it is fundamental to determine the natural resources condition and their availability for the camelid support. The soil organic matter plays a crucial role in the maintenance of the soil fertility at high grasslands. On the other hand, soil respiration is the primary pathway for CO2 fixed by plants returning to the atmosphere and its study is essential to evaluate the soil organic matter mineralization and the global C cycle. Based on this, the objectives of this research were to: (i) evaluate the soil fertility and (ii) determine soil organic matter mineralization on the basis of CO2 releases in Apolobamba. Regarding the lastly vicuna censuses carried out in the studied area, eight representative zones with dissimilar vicuna densities were selected. Other characteristics were also considered to select the study zones: (1) alpaca densities, (2) vegetation communities (3) plant cover and (4) landscape and geo-morphological description. Soil samples from different samplings were collected. Soil respiration was determined at two temperatures: 15 C (based on the highest atmosphere temperature that was registered in the area) and 25 C, in order to monitor the increase in soil respiration (Q10). The physico-chemical soil results pointed out the good soil fertility. However, erosive processes could be taken place likely caused by the alpaca grazing. High total organic carbon contents were observed corresponding to the highest soil respiration at 15 C. This observation was supported by the relationship found between the total organic carbon and the soil respiration. A noticeable increase of the soil respiration when the temperature increased 10 C was reported (from 1083 47 g C m-2 yr-1 at 15 C to 2786 343 g C m-2 yr-1 at 25 C ) which indicated the organic matter mineralization increase and likely the high C reservoirs decrease. Additionally, high Q10 values were observed (13.8 1.5 in subsurface). This indicates that basically climate conditions are actually controlling organic matter mineralization and it is more evident in zones with high total organic carbon contents. Although no vicuna affection on the soil fertility was observed, the camelid grazing generally causes a reduction in the soil respiration rate in Apolobamba. Therefore, it should be undertaken some protection actions to prevent the biodiversity affection bringing camelid overexploitation under control in Bolivian Andean. Keywords: biodiversity, high grasslands, camelid grazing, carbon mineralization, soil respiration

  18. 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.

  19. Soil-specific response functions of organic matter mineralization to the availability of labile carbon.

    PubMed

    Paterson, Eric; Sim, Allan

    2013-05-01

    Soil organic matter (SOM) mineralization processes are central to the functioning of soils in relation to feedbacks with atmospheric CO2 concentration, to sustainable nutrient supply, to structural stability and in supporting biodiversity. Recognition that labile C-inputs to soil (e.g. plant-derived) can significantly affect mineralization of SOM ('priming effects') complicates prediction of environmental and land-use change effects on SOM dynamics and soil C-balance. The aim of this study is to construct response functions for SOM priming to labile C (glucose) addition rates, for four contrasting soils. Six rates of glucose (3atm% (13) C) addition (in the range 0-1mg glucose g(-1) soil day(-1) ) were applied for 8days. Soil CO2 efflux was partitioned into SOM- and glucose-derived components by isotopic mass balance, allowing quantification of SOM priming over time for each soil type. Priming effects resulting from pool substitution effects in the microbial biomass ('apparent priming') were accounted for by determining treatment effects on microbial biomass size and isotopic composition. In general, SOM priming increased with glucose addition rate, approaching maximum rates specific for each soil (up to 200%). Where glucose additions saturated microbial utilization capacity (>0.5mg glucose g(-1) soil), priming was a soil-specific function of glucose mineralization rate. At low to intermediate glucose addition rates, the magnitude (and direction) of priming effects was more variable. These results are consistent with the view that SOM priming is supported by the availability of labile C, that priming is not a ubiquitous function of all components of microbial communities and that soils differ in the extent to which labile C stimulates priming. That priming effects can be represented as response functions to labile C addition rates may be a means of their explicit representation in soil C-models. However, these response functions are soil-specific and may be affected by several interacting factors at lower addition rates. PMID:23505211

  20. Comparison of soil CO2 emission in poorly and well-drained mineral soil at a small agricultural hillside scale

    NASA Astrophysics Data System (ADS)

    TETE, Emmanuel; Viaud, Valerie; Flechard, Chris; Walter, Christian

    2014-05-01

    The increase of greenhouse gases (GHG) in the atmosphere and the climate change which results from it, will have major effects in the 21th century. In agricultural landscapes and others ecosystems, soil CO2 emissions are controlled by thermal and hydrological regimes, but their relative importance seems to be dependant of soil drainage conditions. The purpose of this study was to measure and model soil CO2 emissions at the scale of a hillslope presenting a gradient of soil drainage conditions. The studied hillslope is located in the Kervidy-Naizin headwater catchment (Brittany, France, 4800'N 250W) and corresponds to an agricultural field cropped in a maize / winter wheat rotation. Soil CO2 emissions were measured once per week from February 2013 to March 2014, in two locations contrasting by soil drainage condition: (1) well-drained mineral (WDM) soil classified as Cambisol in upslope position, (2) poorly-drained mineral (PDM) soil classified as Haplic Albeluvisol and which undergoes continuous or periodic saturation and reduction conditions in downslope position. The measurement sites of 9m2 were equipped for continuous measurement of soil water content (TDR probes) and soil temperature. Soil CO2 emissions were measured with the infrared gas analyzer (IRGA) Li-8100A (Li-Cor, Lincoln, USA) until now. Results showed that PDM soils were waterlogged in winter and autumn inducing a low CO2 emission (average of 1.10.2mol.m-2.s-1) which was two times lower than CO2 emissions in WDM soil. A shift of soil moisture to field capacity leading to an availability of oxygen in soil in the spring and summer induced an increase of soil CO2 emissions in PDM soil with a maximum of 5.030.5mol.m-2.s-1 at the end of July. In WDM soil, CO2 emissions were high at the end of spring (average of 7mol.m-2.s-1) and decreased of 65% at the end of summer because of the drought conditions. The modeling of temporal variability of soil CO2 emission by temperature and moisture empirical functions showed that the combined effect of soil temperature and soil moisture explained 77% (61% by T and 39% by SWC) of soil CO2 emission variability in PDM soil, against 63% (53% by T and 47% by SWC) in WDM soil. Others factors such as C input, and oxygen availability due to soil management may also controlled soil CO2 emission and mostly in WDM soil. The integration of these factors in model could help to well understand the difference in soil CO2 emission in Poorly-drained mineral soil compared with well-drained soil at agricultural hillside scale.

  1. Soil moisture influence on the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Guo, S. L.; Zhao, M.; Du, L. L.; Li, R. J.; Jiang, J. S.; Wang, R.; Li, N. N.

    2015-06-01

    Temperature sensitivity of soil organic carbon (SOC) mineralization (i.e., 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 for accurately estimating local soil carbon cycle. In situ SOC mineralization rate was measured using an automated CO2 flux system (Li-8100) in long-term bare fallow soil in the Loess Plateau (3512' N, 10740' E) in Changwu, Shaanxi, China from 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m-2 yr-1, with a mean of 253 g C m-2 yr-1 and a coefficient of variation (CV) of 13%, annual Q10 ranged from 1.48 to 1.94, with a mean of 1.70 and a CV of 10%, and annual soil moisture content ranged from 38.6 to 50.7% soil water-filled pore space (WFPS), with a mean of 43.8% WFPS and a CV of 11%, which were mainly affected by the frequency and distribution of precipitation. Annual Q10 showed a quadratic correlation with annual mean soil moisture content. In conclusion, understanding of the relationships between interannual variation in Q10, soil moisture, and precipitation are important to accurately estimate the local carbon cycle, especially under the changing climate.

  2. Soil microbial activity and structure in mineralized terranes of the Western US

    NASA Astrophysics Data System (ADS)

    Blecker, S. W.; Stillings, L. L.; Decrappeo, N.; Ippolito, J.

    2009-12-01

    Mineralized terranes (areas enriched in metal-bearing minerals) occur throughout the Western US, and are characterized by highly variable soil trace metal concentrations across small spatial scales. Assuming that non-lithologic (extrinsic) soil forming factors are relatively constant between mineralized and unmineralized zones, these mineralized areas allowed us to evaluate the effect of lithology on soil microbial activity. We established the following study sites: 1) sage-grassland on a Mo/Cu deposit (Battle Mountain, NV); 2) pine-chaparral on Ni/Cr bearing rocks (Chinese Camp, CA); and 3) two pine woodland sites on acid-sulfate altered rocks (Reno, NV; Bridgeport, CA). Microbial, physical and chemical measurements were performed on soils from undisturbed mineralized areas and adjacent unmineralized areas to determine baseline conditions for comparison to sites disturbed by mining. A host of abiotic soil parameters, along with bioavailable (diethylenetriaminepentaacetic acid (DTPA)-extractable) and total metals, were measured to examine their correlation with the following measures of microbial activity: enzyme assays (arylsulfatase, phosphatase, fluorescein diacetate hydrolysis), C/N mineralization potential, C substrate utilization (Biolog Ecoplate), and microbial biomass and community structure (phospholipid fatty acid analysis). Within the Battle Mountain study area, both microbial activity and structure were statistically similar between mineralized and unmineralized soils. Nutrient and metal concentrations were also similar; the only differences being higher Cu and lower P in the mineralized soils. Within the Chinese Camp study area, soil organic carbon and total nitrogen concentrations were similar between the serpentine (Ni/Cr bearing) and adjacent andesite soils, while differences were noted for other nutrients (S, P, Ca, Mg). For the serpentine soils, Co, Fe, Mn, and Ni showed the strongest correlations with microbial activity, where Cr, Mn showed the strongest correlations in the andesite soils. Measures of microbial activity were statistically similar, except for arylsulfatase and Biolog C substrate utilization, which were greater in the andesite soils. Biolog substrate utilization richness was greater for the andesite soils, which also showed greater fungal biomass compared to the serpentine soils. In the acid sulfate systems, most measures of microbial activity were reduced in the acid sulfate soils compared to the adjacent andesite soils. Lower pH and P, and greater Al concentrations in the acid sulfate soils are potential inhibitors of microbial activity, while greater concentrations of inorganic N suggest that N is not limiting in the acid sulfate soils. Biolog substrate utilization richness was much lower in the acid sulfate soils, which also exhibited a greater proportion of polymer and carbohydrate use compared to the andesite soils. Impacts on microbial activity and microbial community structure are depend on a combination of trace metal and nutrient concentrations within a given mineralization type. Improving our understanding of biotic/abiotic relationships in undisturbed systems should increase our understanding of these relationships in areas disturbed by mining.

  3. Effects of simulated acid rain on glucose mineralization and some physicochemical properties of forest soils

    SciTech Connect

    Strayer, R.F.; Alexander, M.

    1981-10-01

    To study the effects of acid rain, samples of forest soils were exposed to a continuous application of 100 cm of simulated acid rain (pH 3.2-4.1) at 5 cm/hour, or to intermittent 1-hour applications of 5 cm of simulated acid rain three times per week for 7 weeks. The major effects of the simulated acid rain were localized at the top of the soil and included lower pH values and glucose mineralization rates, and higher exchangeable Al and total and exchange acidity. The acidity penetrated further in the more acid soils. The mineralization of /sup 14/C-glucose was measured at concentrations of 1.5-54 ..mu..g glucose/g of soil. Glucose mineralization in the test soils (pH values of 4.4-7.1) was inhibited by the continuous exposure to simulated acid rain at pH 3.2 but not a pH 4.1. The extent of inhibition depended on the soil and the initial glucose concentration. Exposure of one soil to 7 weeks of intermittent applications of simulated acid rain at pH 3.2 reduced the mineralization rate at the three glucose concentrations tested. These data suggest that acid rain may have a significant impact on microbial activity.

  4. Microbes residing in young organic rich Alaskan soils contain older carbon than those residing in old mineral high Arctic soils

    NASA Astrophysics Data System (ADS)

    Ziolkowski, L. A.; Slater, G. F.; Onstott, T. C.; Whyte, L.; Townsend-Small, A.

    2013-12-01

    Arctic soils range from very organic rich to low carbon and mineral-dominated soils. At present, we do not yet fully understand if all carbon in the Arctic is equally vulnerable to mineralization in a warmer climate. Many studies have demonstrated that ancient carbon is respired when permafrost has thawed, yet our understanding of the active layer and permafrost carbon dynamics is still emerging. In an effort to remedy this disconnect between our knowledge of surface fluxes and below ground processes, we used radiocarbon to examine the microbial carbon dynamics in soil cores from organic rich soils near Barrow, Alaska and mineral soils from the Canadian high Arctic. Specifically, we compared the microbial community using lipid biomarkers, the inputs of carbon using n-alkanes and measured the 14C of both the bulk organic carbon and of the microbial lipids. In theory, the microbial lipids (phospholipid fatty acids, PLFA) represent the viable microbial community, as these lipids are hydrolyzed quickly after cell death. Variations in the PLFA distributions suggested that different microbial communities inhabit organic rich Alaskan soils and those of the Canadian high Arctic. When the PLFA concentrations were converted to cellular concentration, they were within the same order of magnitude (1 to 5 x 108 cells/g dry soil) with slightly higher cell concentrations in the organic rich Alaskan soils. When these cellular concentrations were normalized to the organic carbon content, the Canadian high Arctic soils contained a greater proportion of microbes. Although bulk organic carbon 14C of Alaskan soils indicated more recent carbon inputs into the soil than the Canadian high Arctic soils, the 14C of the PLFA revealed the opposite. For corresponding depth horizons, microbes in Alaskan soils were consuming carbon 1000 to 1500 years older than those in the Canadian high Arctic. Differences between the 14C content of bulk organic carbon and the microbial lipids were much smaller in Alaskan soil than that of the Canadian high Arctic soil, indicating that Alaskan microbes were interacting with the bulk organic carbon pool and Canadian high Arctic soil microbes were disconnected from the bulk organic carbon pool. Additionally, dissimilarities in the n-alkane distributions suggest vastly different carbon sources to these different soils. Collectively, these results suggest that (a) these Arctic soils contain a comparable abundance of microbes, (b) the organic carbon being accumulated in the Alaskan soil is likely from recent biomass, (c) mineral soil accumulation in the Canadian high Arctic is likely due to erosional inputs of ancient carbon and (d) the carbon stocks in Alaskan soils are more bioavailable to the microbes than those in mineral soils of the Canadian high Arctic. Incubation studies that incorporate gas fluxes and proteomics may tease apart if the observed differences in bioavailability are a function of temperature, substrate availability or some other variable.

  5. Bacteria-mineral interactions in soil and their effect on particle surface properties

    NASA Astrophysics Data System (ADS)

    Miltner, Anja; Achtenhagen, Jan; Goebel, Marc-Oliver; Bachmann, Jörg; Kästner, Matthias

    2015-04-01

    Interactions between bacteria or their residues and mineral surfaces play an important role for soil processes and properties. It is well known that bacteria tend to grow attached to surfaces and that they get more hydrophobic when grown under stress conditions. In addition, bacterial and fungal biomass residues have recently been shown to contribute to soil organic matter formation. The attachment of bacteria or their residues to soil minerals can be expected to modify the surface properties of these particles, in particular the wettability. We hypothesize that the extent of the effect depends on the surface properties of the bacteria, which change depending on environmental conditions. As the wettability of soil particles is crucial for the distribution and the availability of water, we investigated the effect of both living cells and bacterial residues (cell envelope fragments and cytosol) on the wettability of model mineral particles in a simplified laboratory system. We grew Pseudomonas putida cells in mineral medium either without (unstressed) or with additional 1.5 M NaCl (osmotically stressed). After 2 h of incubation, the cells were disintegrated by ultrasonic treatment. Different amounts of either intact cells, cell envelope fragments or cytosol (each corresponding to 108, 109, or 1010 cells per gram of mineral) were mixed with quartz sand, quartz silt or kaolinite. The bacteria-mineral associations were air-dried for 2 hours and analyzed for their contact angle. We found that the surfaces of osmotically stressed cells were more hydrophobic than the surfaces of unstressed cells and that the bacteria-mineral associations had higher contact angles than the pure minerals. A rather low surface coverage (~10%) of the mineral surfaces by bacteria was sufficient to increase the contact angle significantly, and the different wettabilities of stressed and unstressed cells were reflected in the contact angles of the bacteria-mineral associations. The increases in the contact angles were similar for intact cells and cell envelope fragments, whereas they were even more pronounced if the minerals interacted with the cytosol. Based on these results we conclude that bacterial cells and their residues play an important role in controlling soil particle surface properties, in particular wettability. This process can explain the development of water repellency in soils, which has a major impact on the distribution and availability of water in soils at the microscale.

  6. Soil Genesis and Development, Lesson 1 - Rocks and Minerals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    All soil ultimately forms from rocks or their weathering products. Geologists classify rocks according to their origins. General rock types can weather to give soils with distinctive properties. The objectives of this lesson are: 1. To be able to classify rocks based on visual characteristics accord...

  7. Improvement of pesticide mineralization in on-farm biopurification systems by bioaugmentation with pesticide-primed soil.

    PubMed

    Sniegowski, Kristel; Bers, Karolien; Van Goetem, Kris; Ryckeboer, Jaak; Jaeken, Peter; Spanoghe, Pieter; Springael, Dirk

    2011-04-01

    Microcosms were used to examine whether pesticide-primed soils could be preferentially used over nonprimed soils for bioaugmentation of on-farm biopurification systems (BPS) to improve pesticide mineralization. Microcosms containing a mixture of peat, straw and either linuron-primed soil or nonprimed soil were irrigated with clean or linuron-contaminated water. The lag time of linuron mineralization, recorded for microcosm samples, was indicative of the dynamics of the linuron-mineralizing biomass in the system. Bioaugmentation with linuron-primed soil immediately resulted in the establishment of a linuron-mineralizing capacity, which increased in size when fed with the pesticide. Also, microcosms containing nonprimed soil developed a linuron-mineralizing population, but after extended linuron feeding. Additional experiments showed that linuron-mineralization only developed with some nonprimed soils. Concomitant with the increase in linuron degradation capacity, targeted PCR-denaturing gradient gel electrophoresis showed the proliferation of a Variovorax phylotype related to the linuron-degrading Variovorax sp. SRS16 in microcosms containing linuron-primed soil, suggesting the involvement of Variovorax in linuron degradation. The correlation between the appearance of specific Variovorax phylotypes and linuron mineralization capacity was less clear in microcosms containing nonprimed soil. The data indicate that supplementation of pesticide-primed soil results in the establishment of pesticide-mineralizing populations in a BPS matrix with more certainty and more rapidly than the addition of nonprimed soil. PMID:21231937

  8. 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 40C). 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 40C (R2?=?0.880.99, 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

  9. High temperature and salinity enhance soil nitrogen mineralization in a tidal freshwater marsh.

    PubMed

    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 40C). 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 40C (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

  10. Carbon Mineralizability Determines Interactive Effects on Mineralization of Pyrogenic Organic Matter and Soil Organic Carbon

    SciTech Connect

    Whitman, Thea L.; Zhu, Zihua; Lehmann, Johannes C.

    2014-10-31

    Soil organic carbon (SOC) is a critical and active pool in the global C cycle, and the addition of pyrogenic organic matter (PyOM) has been shown to change SOC cycling, increasing or decreasing mineralization rates (often referred to as priming). We adjusted the amount of easily mineralizable C in the soil, through 1-day and 6-month pre-incubations, and in PyOM made from maple wood at 350°C, through extraction. We investigated the impact of these adjustments on C mineralization interactions, excluding pH and nutrient effects and minimizing physical effects. We found short-term increases (+20-30%) in SOC mineralization with PyOM additions in the soil pre-incubated for 6 months. Over the longer term, both the 6-month and 1-day pre-incubated soils experienced net ~10% decreases in SOC mineralization with PyOM additions. This was possibly due to stabilization of SOC on PyOM surfaces, suggested by nanoscale secondary ion mass spectrometry. Additionally, the duration of pre-incubation affected priming interactions, indicating that there may be no optimal pre-incubation time for SOC mineralization studies. We show conclusively that relative mineralizability of SOC in relation to PyOM-24 C is an important determinant of the effect of PyOM additions on SOC mineralization.

  11. On the origin of superparamagnetic minerals of tropical soils and their impact on landmine detection

    NASA Astrophysics Data System (ADS)

    Igel, Jan; Preetz, Holger; Altfelder, Sven

    2010-05-01

    Magnetic susceptibility of soils is mainly determined by their content of ferrimagnetic minerals whereas titanomagnetite, magnetite and maghemite being the most important ones. Titanomagnetite and magnetite are of magmatic origin, i.e. they crystallise during cooling of iron-rich magma and are part of many igneous rocks. Maghemite and sometimes magnetite are of pedogenic origin. They develop by crystallisation of dissolved iron during soil forming processes. Ferrimagnetic minerals that are smaller than some tens of nanometres are superparamagnetic (SP) and show frequency dependent susceptibility. SP minerals crystallise if magma cools down rapidly (e.g. volcanic magmas, glasses and ashes) and are frequently formed during pedogenesis. In order to investigate the origin and formation of SP minerals in tropical soils, we analyse magnetic properties of 594 samples from the entire tropics comprising the whole range of weathering states from unweathered rock to highly weathered soil. Tropical soils are subject to intense chemical weathering and are rich in ferrimagnetic and in particular SP minerals. The process leading to a high content of these minerals is either residual enrichment due to their weathering resistance or neo-formation. In this study we focus on the frequency dependent susceptibility (absolute and relative) of the samples and classify it according to the parent material and alteration. We observe that • within each parent-material group, rock material shows in general lower susceptibility and absolute frequency dependence than soil material • ultrabasic and basic/intermediate rocks and soils developed from these rocks show high absolute frequency dependent susceptibility and, in contrast, acid rocks and sediments show lower absolute frequency dependence • absolute frequency dependence increases from unweathered rock to weathered rock, and from subsoil to topsoil material within every group of parent material • relative frequency dependence rises successively with weathering for ultrabasic, basic/intermediate and acid igneous parent material, but, it tends to decrease for clay/clay slate and sandstone. Based on the above observations we conclude that the content of SP minerals depends on both: parent rock and alteration of the material. The total amount of SP minerals rises during weathering, regardless of the parent material. The process is either preferential accumulation of weathering resistant magnetic minerals, including the ultra-fine grained fraction, or neo-formation of new magnetic minerals. The increase of relative frequency dependence of igneous rocks is a clear indication that SP minerals are formed during soil genesis. However, for some sedimentary rocks, the amount of SP minerals is already high and is not subsequently increased further during weathering. Electromagnetic induction (EMI) based metal detectors are the most widely used sensing techniques in landmine clearance operations. They are negatively influenced by magnetic susceptibility and its frequency dependence. In particular tropical soils show to have a negative impact on EMI sensors. Besides, the tropics are the regions which are most affected by landmines where most of the humanitarian demining-activities concentrate. Currently, no soil classification system exists that helps to predict the influence of frequency dependent susceptibility on landmine detection. We deduce a system that can be used to predict the soil impact depending on parent material and weathering. Our system can be consulted by demining organisations to predict metal detector performance in tropical regions based on geologic and soil maps. Ultra-basic, basic and intermediate igneous rocks have a moderate influence on EMI detectors in average cases and a very severe influence in extreme cases. Soils developed from these rocks have a severe or very severe influence. In contrast, acid igneous rocks and sediments do not influence EMI detectors severely. Soils developed from these rocks have no influence in average cases; however, they may have a very severe influence in extreme cases.

  12. Ultrasonically aided mineral processing technique for remediation of soil contaminated by heavy metals.

    PubMed

    Kyllönen, Hanna; Pirkonen, Pentti; Hintikka, Väinö; Parvinen, Pekka; Grönroos, Antti; Sekki, Hannu

    2004-05-01

    In this study, power ultrasound was used as aiding method for the mineral processing technique, which have recently been developed for the remediation of soil contaminated by heavy metal containing bullets, their broken parts and alteration products. Power ultrasound was used to disperse the soil to remove metals and metal compounds from soil particle surfaces instead of attrition conditioning. The soil diluted with water was treated using 22 kHz ultrasound power of 100 W up to 500 W. The effect of different ultrasonic treatment time and pulsation of ultrasound were studied on the purity of sink and float fractions in heavy medium separation process, screen fractions, and mineral concentrates and tailings from flotation process. Ultrasound enhanced the remediation of soil fractions in all the studied cases. Optimisation of the ultrasonic power will be done in the continuation study. PMID:15081983

  13. Effects of flooding and warming on soil organic matter mineralization in Avicennia germinans mangrove forests and Juncus roemerianus salt marshes

    NASA Astrophysics Data System (ADS)

    Lewis, David Bruce; Brown, Jewel A.; Jimenez, Kristine L.

    2014-02-01

    Under a changing climate, coastal wetlands experience sea level rise, warming, and vegetation change, all of which may influence organic matter mineralization. In coastal wetlands of subtropical west-central Florida (USA), we investigated how soil carbon (C) and nitrogen (N) mineralization respond to soil water, temperature, and ecosystem type (Avicennia germinans mangrove forest vs. Juncus roemerianus salt marsh). We evaluated how soil respiration and mineral N concentration varied along a soil moisture gradient, and whether these relationships differed between ecosystem types. Then, we manipulated soils in a 28-d laboratory incubation to evaluate how potentially mineralizable C and N respond to temperature (23 vs. 27 °C), soil hydroperiod (inundated 4 vs. 20 h/d), and soil source. Soil saturation and inundation suppressed short-term (minutes to weeks) C mineralization from near-surface soils. Soil CO2 efflux declined by 65% as soil moisture increased from 75% to 85%, and potentially mineralizable C was 18% lower with a 20-h hydroperiod than with a 4-h hydroperiod. Organic C quality appears to be greater in A. germinans than in J. roemerianus soils, as A. germinans soils had higher field CO2 efflux rates and greater mineralizable C:N (despite lower total C:N). Increasing incubation temperature from 23 to 27 °C elevated potentially mineralizable C by 40%, indicating that two symptoms of climate change (increased inundation from sea level rise, and warming) may have opposing effects on soil C mineralization. Temperature sensitivity of C mineralization was high for long-hydroperiod soils, however, suggesting that protection of soil organic matter (SOM) due to prolonged inundation will be undermined by warming. Potentially mineralizable N was greater in J. roemerianus soils, although in situ mineral N was not different between ecosystems, instead correlating positively with SOM. These results indicate that models forecasting soil elevation responses to climate change might include inundation effects on mineralization rates.

  14. Nitrogen mineralization in soils under grasses and under trees in a protected Venezuelan savanna

    NASA Astrophysics Data System (ADS)

    Snchez, L. F.; Garca-Miragaya, J.; Chacn, N.

    Nitrogen mineralization was evaluated in soils beneath the most common woody species growing isolated within the grass matrix of a Venezuelan Trachypogon savanna, which has been protected from fire and cattle grazing since 1961. Adult trees of three evergreen species, Byrsonima crassifolia (L) H. B. K., Curatella americana L., and Bowdichia virgilioides H. B. K; and two deciduous, Godmania macrocarpa Hemsley and Cochlospermun vitifolium (Wild) Spreng were selected. The amount of N mineralized (NH 4+-N+NO 3--N) during 15 weeks of laboratory incubation of soils collected from beneath trees, was significantly higher ( p<0.01) than those from under grasses. Values of N mineralized on soil from under trees were from 21.28 to 82.65% greater than for soil from under grasses. A highly significant ( p<0.01) positive correlation, for all soils, was found between Nm and SOC, and between Nm and Nt. The higher N mineralization rates under trees would reflect a higher soil biological activity, due to higher SOC and Nt, of the soils under the tree canopies than those under grasses. The N availability values obtained under all species reveal the importance these trees have for creating enriched areas on generally oligotrophic soils. Nitrogen mineralized in the soil from beneath evergreen trees was significantly ( p<0.01) higher than from under deciduous trees, being 25.87% higher on average. Similarly to the relation found for all soils, a highly significant ( p<0.01) positive correlation between Nm and SOC and between Nm and Nt was also obtained for soils beneath all trees, indicating the importance of SOC and Nt for nitrogen mineralization processes in this savanna. The higher SOC and Nt contents found under evergreen trees are probably due to the longer time they have been established on the site as compared to the deciduous ones. The chemical quality of fresh fallen leaves (as measured by their lignin/nitrogen ratio) did not seem to influence the quality of the SOM (as measured by C/N ratio), since the C/N ratio was not statistically different for the soils under the two groups of trees. Apparently, whatever the chemical quality of the fresh fallen leaves (higher lignin/nitrogen ratio in evergreen trees), the humification processes in this savanna soil environment seems to homogenize the SOM beneath both types of trees.

  15. Redistribution of soil water by a saprotrophic fungus enhances carbon mineralization.

    PubMed

    Guhr, Alexander; Borken, Werner; Spohn, Marie; Matzner, Egbert

    2015-11-24

    The desiccation of upper soil horizons is a common phenomenon, leading to a decrease in soil microbial activity and mineralization. Recent studies have shown that fungal communities and fungal-based food webs are less sensitive and better adapted to soil desiccation than bacterial-based food webs. One reason for a better fungal adaptation to soil desiccation may be hydraulic redistribution of water by mycelia networks. Here we show that a saprotrophic fungus (Agaricus bisporus) redistributes water from moist (-0.03 MPa) into dry (-9.5 MPa) soil at about 0.3 cm?min(-1) in single hyphae, resulting in an increase in soil water potential after 72 h. The increase in soil moisture by hydraulic redistribution significantly enhanced carbon mineralization by 2,800% and enzymatic activity by 250-350% in the previously dry soil compartment within 168 h. Our results demonstrate that hydraulic redistribution can partly compensate water deficiency if water is available in other zones of the mycelia network. Hydraulic redistribution is likely one of the mechanisms behind higher drought resistance of soil fungi compared with bacteria. Moreover, hydraulic redistribution by saprotrophic fungi is an underrated pathway of water transport in soils and may lead to a transfer of water to zones of high fungal activity. PMID:26554004

  16. 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.

  17. Effects of amendment of different biochars on soil physical and biological properties related to carbon mineralization

    NASA Astrophysics Data System (ADS)

    Zhang, Renduo; Zhu, Shuzhi; Ouyang, Lei

    2014-05-01

    Biochar addition to soils potentially affects various soil properties, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and biological properties. Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700°C, respectively. Each biochar was mixed at 5% (w/w) with a forest soil and the mixture was incubated for 180 days, during which soil physical and biological properties, and soil respiration rates were measured. Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity and soil respiration rates at the early incubation stage. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than with the dairy manure biochars. Biochar addition significantly affected the soil physical and biological properties, which resulted in different soil carbon mineralization rates.

  18. Effect of cyclodextrins on surface and pore properties of soil clay minerals.

    PubMed

    Jozefaciuk, G; Muranyi, A; Fenyvesi, E

    2001-12-15

    Although cyclodextrins are increasingly used in soil decontamination, little is known about their effects on soil physicochemical properties. In this work, the surface and pore properties of randomly methylated beta-cyclodextrin (RAMEB) and three typical clay minerals were characterized, and the effects of RAMEB concentrations on clay minerals were studied using water vapor adsorption-desorption and mercury intrusion porosimetry techniques. As compared to clay minerals, for pure RAMEB very large surface area and volume of nanometer-size pores (micropores) were determined. Energy of interaction with water vapor, volume of micrometer-size pores (mesopores), and fractal dimensions in both pore size ranges of RAMEB were lower than those of the minerals. When increasing amounts of RAMEB were added to the minerals, the surface area and micropore volume decreased and adsorption energy increased. The volume of mesopores decreased after RAMEB treatments for bentonite and kaolin and increased for illite. As deduced from the fractal dimensions increase, the pore structure of the minerals became more complex with RAMEB addition. The observed changes were in general contrary to these expected when RAMEB and minerals coexist as separate, nonreactive phases and suggested strong interaction of RAMEB with clay minerals. PMID:11775177

  19. Forest type affects the coupled relationships of soil C and N mineralization in the temperate forests of northern China.

    PubMed

    Quan, Quan; Wang, Changhui; He, Nianpeng; Zhang, Zhen; Wen, Xuefa; Su, Hongxin; Wang, Qing; Xue, Jingyue

    2014-01-01

    Decomposition of soil organic matter (SOM) is sensitive to vegetation and climate change. Here, we investigated the influence of changes in forest types on the mineralization of soil carbon (C) and nitrogen (N), and their temperature sensitivity (Q10) and coupling relationships by using a laboratory soil incubation experiments. We sampled soils from four forest types, namely, a primary Quercus liaotungensis forest (QL), Larix principis-rupprechtii plantation (LP), Pinus tabulaeformis plantation (PT), and secondary shrub forest (SS) in temperate northern China. The results showed that soil C and N mineralization differed significantly among forest types. Soil C and N mineralization were closely coupled in all plots, and C:N ratios of mineralized SOM ranged from 2.54 to 4.12. Forest type significantly influenced the Q10 values of soil C and N mineralization. The activation energy (Ea) of soil C and N mineralization was negatively related to the SOM quality index in all forest types. The reverse relationships suggested that the carbon quality-temperature (CQT) hypothesis was simultaneously applicable to soil C and N mineralization. Our findings show that the coupled relationships of soil C and N mineralization can be affected by vegetation change. PMID:25322802

  20. Forest type affects the coupled relationships of soil C and N mineralization in the temperate forests of northern China

    PubMed Central

    Quan, Quan; Wang, Changhui; He, Nianpeng; Zhang, Zhen; Wen, Xuefa; Su, Hongxin; Wang, Qing; Xue, Jingyue

    2014-01-01

    Decomposition of soil organic matter (SOM) is sensitive to vegetation and climate change. Here, we investigated the influence of changes in forest types on the mineralization of soil carbon (C) and nitrogen (N), and their temperature sensitivity (Q10) and coupling relationships by using a laboratory soil incubation experiments. We sampled soils from four forest types, namely, a primary Quercus liaotungensis forest (QL), Larix principis-rupprechtii plantation (LP), Pinus tabulaeformis plantation (PT), and secondary shrub forest (SS) in temperate northern China. The results showed that soil C and N mineralization differed significantly among forest types. Soil C and N mineralization were closely coupled in all plots, and C:N ratios of mineralized SOM ranged from 2.54 to 4.12. Forest type significantly influenced the Q10 values of soil C and N mineralization. The activation energy (Ea) of soil C and N mineralization was negatively related to the SOM quality index in all forest types. The reverse relationships suggested that the carbon quality-temperature (CQT) hypothesis was simultaneously applicable to soil C and N mineralization. Our findings show that the coupled relationships of soil C and N mineralization can be affected by vegetation change. PMID:25322802

  1. ASSESSING CHANGES IN SOIL MICROBIAL COMMUNITIES AND CARBON MINERALIZATION IN BT AND NON-BT CORN RESIDUE-AMENDED SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of Bt corn (Zea mays L.) residue on soil microbial communities and rates of C mineralization were investigated. The Bt corn residue had a higher lignin content (12%) and lignin/N (9.9) ratio compared with its non-Bt near-isoline (10% lignin; lignin/N = 8.6). We examined the relationships...

  2. In situ observations of soil minerals and organic matter in the early phases of prescribed fires

    NASA Astrophysics Data System (ADS)

    Kavouras, Ilias G.; Nikolich, George; Etyemezian, Vic; Dubois, David W.; King, James; Shafer, David

    2012-06-01

    We examined the chemical composition of aerosol samples collected during a prescribed fire at a Great Basin Desert site in the context of samples collected from controlled combustion of vegetation clippings from the same site and resuspension of soil samples obtained prior to and after the burn event. We observed a distinct difference in the composition of organic carbon resuspended soil dust after the burn, reflecting changes caused by the heating of the soil. The relative abundances of minerals and organic carbon fractions in aerosols collected during the first period of the burn were identical to those measured in soil dust. For aerosol samples collected for the remaining two periods of the burn event, the profiles of both minerals and organic carbon matched quite well those observed for vegetation combustion. Reconstruction of aerosol samples collected during the burn event showed that vegetation combustion dominated emissions but mineral soil dust may account for about 10% of PM10emissions (reconstructed) during the early stages of the fire. A large fraction of emissions during the first two hours was also unaccounted mainly because of the insufficient conversion of organic carbon to organic mass. The abundance of heavier non-volatile organics in soil dust suggested the presence of humic/fulvic acids that exhibit higher OM-to-OC ratios and thus, account for a proportion of the unaccounted emissions. These findings indicated that soil dust may be released into the air during a fire event, probably due to the enhanced turbulent mixing near the burn front.

  3. Microbial nitrogen dynamics in organic and mineral soil horizons along a latitudinal transect in western Siberia

    PubMed Central

    Wild, Birgit; Schnecker, Jörg; Knoltsch, Anna; Takriti, Mounir; Mooshammer, Maria; Gentsch, Norman; Mikutta, Robert; Alves, Ricardo J Eloy; Gittel, Antje; Lashchinskiy, Nikolay; Richter, Andreas

    2015-01-01

    Soil N availability is constrained by the breakdown of N-containing polymers such as proteins to oligopeptides and amino acids that can be taken up by plants and microorganisms. Excess N is released from microbial cells as ammonium (N mineralization), which in turn can serve as substrate for nitrification. According to stoichiometric theory, N mineralization and nitrification are expected to increase in relation to protein depolymerization with decreasing N limitation, and thus from higher to lower latitudes and from topsoils to subsoils. To test these hypotheses, we compared gross rates of protein depolymerization, N mineralization and nitrification (determined using 15N pool dilution assays) in organic topsoil, mineral topsoil, and mineral subsoil of seven ecosystems along a latitudinal transect in western Siberia, from tundra (67°N) to steppe (54°N). The investigated ecosystems differed strongly in N transformation rates, with highest protein depolymerization and N mineralization rates in middle and southern taiga. All N transformation rates decreased with soil depth following the decrease in organic matter content. Related to protein depolymerization, N mineralization and nitrification were significantly higher in mineral than in organic horizons, supporting a decrease in microbial N limitation with depth. In contrast, we did not find indications for a decrease in microbial N limitation from arctic to temperate ecosystems along the transect. Our findings thus challenge the perception of ubiquitous N limitation at high latitudes, but suggest a transition from N to C limitation of microorganisms with soil depth, even in high-latitude systems such as tundra and boreal forest. Key Points We compared soil N dynamics of seven ecosystems along a latitudinal transectShifts in N dynamics suggest a decrease in microbial N limitation with depthWe found no decrease in microbial N limitation from arctic to temperate zones PMID:26693204

  4. The priming effect of soluble carbon inputs in organic and mineral soils from a temperate forest.

    PubMed

    Wang, Hui; Xu, Wenhua; Hu, Guoqing; Dai, Weiwei; Jiang, Ping; Bai, Edith

    2015-08-01

    The priming effect (PE) is one of the most important interactions between C input and output in soils. Here we aim to quantify patterns of PE in response to six addition rates of (13)C-labeled water-soluble C (WSC) and determine if these patterns are different between soil organic and mineral layers in a temperate forest. Isotope mass balance was used to distinguish WSC derived from SOC-derived CO2 respiration. The relative PE was 1.1-3.3 times stronger in the mineral layer than in the organic layer, indicating higher sensitivity of the mineral layer to WSC addition. However, the magnitude of cumulative PE was significantly higher in the organic layer than in the mineral layer due to higher SOC in the organic layer. With an increasing WSC addition rate, cumulative PE increased for both layers, but tended to level off when the addition rate was higher than 400 mg C kg(-1) soil. This saturation effect indicates that stimulation of soil C loss by exogenous substrate would not be as drastic as the increase of C input. In fact, we found that the mineral layer with an WSC addition rate of 160-800 mg C kg(-1) soil had net C storage although positive PE was observed. The addition of WSC basically caused net C loss in the organic layer due to the high magnitude of PE, pointing to the importance of the organic layer in C cycling of forest ecosystems. Our findings provide a fundamental understanding of PE on SOC mineralization of forest soils and warrant further in situ studies of PE in order to better understand C cycling under global climate change. PMID:25790803

  5. Effect of clay minerals and nanoparticles on chromium fractionation in soil contaminated with leather factory waste.

    PubMed

    Taghipour, Marzieh; Jalali, Mohsen

    2015-10-30

    This study was conducted to investigate the effect of time, clay minerals and nanoparticles (NPs) on chromium (Cr) fractionation in a soil contaminated with leather factory waste (LFW). Soil was mixed with LFW, then, the contaminated soils were treated with clay minerals (bentonite and zeolite) and nanoparticles (MgO, TiO2 and ZnO) at 5% and 1%, respectively. The samples were incubated for 15-180 days at 25 °C and constant moisture. After incubation, Cr in control and treated soils was fractionated by the sequential extraction procedure. The distribution of various Cr fractions in control soil indicated that the greatest amounts of Cr were found in the residual fraction (RES) followed by the carbonate (CAR), organic matter (OM) and exchangeable (EXC) fractions. The addition of LFW in soils increased Cr concentration in all fractions. The higher proportion of EXC fraction in the soil treated with LFW indicates its higher potential of leaching and runoff transport. In all treated soils, the RES fraction was increased, while EXC and OM fractions were decreased during incubation. The results indicated that NPs are effective adsorbent for the removal of Cr ions from LFW treated soil, and they could be useful in reducing their environment risk. PMID:25956643

  6. Spatial Arrangement of Organic Compounds on a Model Mineral Surface: Implications for Soil Organic Matter Stabilization

    NASA Astrophysics Data System (ADS)

    Ambaye, Haile; Petridis, Loukas; Jagadamma, Sindhu; Kilbey, Michael; Lauter, Valeria; Lokitz, Bradley; Mayes, Melanie

    2015-03-01

    Stability of organic carbon compounds in soil is important for global climate futures which could be affected by the complexity of the mineral-organic carbon interfaces. We examined the nanoscale structure of model interfaces by depositing films of organic carbon compounds of contrasting chemical character, hydrophilic glucose, deuterated-amphiphilic stearic acid (SA) and Natural Organic Matters (NOM) onto a soil mineral analogue (Al2O3) . The NOM was separated into its constituent components such as NOM-Philic and NOM-Phobic when it is deposited onto the soil mineral. We used Neutron Reflectivity technique to understand the depth organization of the thin films. The result indicates that glucose molecules reside in a layer between Al2O3 and stearic acid and SA self-assembles. No self-assembly of SA was observed when SA and NOM-Phobic was deposited on the mineral soil. Molecular dynamics simulations reveal the thermodynamic driving force behind glucose partitioning on the mineral interface. Funded by ORNL Director's Research and Development Program. Research at ORNL was sponsored by the BES, DOE.

  7. Importance of soil and vineyard management in the determination of grapevine mineral composition.

    PubMed

    Likar, M; Vogel-Miku, K; Potisek, M; Han?evi?, K; Radi?, T; Ne?emer, M; Regvar, M

    2015-02-01

    The spatial variability of the mineral composition of grapevines in production vineyards along the east Adriatic coast was determined and compared between conventional and sustainable vineyard management. Cluster analysis shows a high level of spatial variability even within the individual locations. Factor analysis reveals three factors with strong loading for the macronutrients K and P and the micronutrient Mn, which explain 67% of the total variance in the mineral composition. Here, 26% to 34% of the variance of these three elements can be explained by abiotic and biotic soil parameters, with soil concentrations of K, Fe and Cu, organic matter content, and vesicular colonisation showing the strongest effects on the mineral composition of the grapevines. In addition, analysis of the mineral composition data shows significant differences between differently managed vineyards, with increased bioaccumulation of P and K in sustainable vineyards, while Zn bioaccumulation was increased in conventional vineyards. Our data confirm the importance of soil and vineyard management in the concept of terroir, and demonstrate the effects of sustainable management practices on the mineral nutrition of grapevines that result from modified nutrient availability related to changes in the abiotic and biotic characteristics of the soil. PMID:25461075

  8. 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.

  9. Effects of temperature and amendments on nitrogen mineralization in selected Australian soils.

    PubMed

    Thangarajan, Ramya; Bolan, Nanthi S; Naidu, Ravi; Surapaneni, Aravind

    2015-06-01

    The effects of temperature (18, 24, and 37 C) and form of nitrogen (N) input from various sources (organic-green waste compost, biosolids, and chicken manure; inorganic-urea) on N transformation in three different Australian soils with varying pH (4.30, 7.09, and 9.15) were examined. Ammonification rate (ammonium concentration) increased with increase in temperature in all soil types. The effect of temperature on nitrification rate (nitrate concentration) followed 24?>?37?>?18 C. Nitrification rate was higher in neutral and alkaline soils than acidic soil. Mineral N (bioavailable N) concentration was high in urea treatments than in organic N source treatments in all soil types. Acidic soil lacked nitrification activity resulting in low nitrate (NO3) buildup in urea treatment, whereas a significant NO3 buildup was noticed in green waste compost treatment. In neutral and alkaline soils, the nitrification activity was low at 37 C in urea treatment but with a significant NO3 buildup in organic amendment added soils. Addition of organic N sources supplied ammonia oxidizing bacteria thereby triggering nitrification in the soils (even at 37 C). This study posits the following implications: (1) inorganic fertilizer accumulate high NO3 content in soils in a short period of incubation, thereby becoming a potential source of NO3 leaching; (2) organic N sources can serve as possible source of nitrifying bacteria, thereby increasing bioavailable N (NO3) in soils regardless of the soil properties and temperature. PMID:24114384

  10. Association of Growth Substrates and Bacterial Genera with Benzo[a]pyrene Mineralization in Contaminated Soil

    PubMed Central

    Jones, Maiysha D.; Rodgers-Vieira, Elyse A.; Hu, Jing; Aitken, Michael D.

    2014-01-01

    Abstract Benzo[a]pyrene (BaP) is a carcinogenic polycyclic aromatic hydrocarbon (PAH) that is not known to be a bacterial growth substrate. Organisms capable of cometabolizing BaP in complex field-contaminated systems have not previously been identified. We evaluated BaP mineralization by a bacterial community from a bioreactor treating PAH-contaminated soil during coincubation with or after pre-enrichment on various PAHs as growth substrates. Pyrosequence libraries of 16S rRNA genes were used to identify bacteria that were enriched on the added growth substrate as a means of associating specific organisms with BaP mineralization. Coincubating the bioreactor-treated soil with naphthalene, phenanthrene, or pyrene inhibited BaP mineralization, whereas pre-enriching the soil on the same three PAHs enhanced BaP mineralization. Combined, these results suggest that bacteria in the bioreactor community that are capable of growing on naphthalene, phenanthrene, and/or pyrene can metabolize BaP, with coincubation competitively inhibiting BaP metabolism. Anthracene, fluoranthene, and benz[a]anthracene had little effect on BaP mineralization compared to incubations without an added growth substrate under either coincubation or pre-enrichment conditions. Substantial increases in relative abundance after pre-enrichment with phenanthrene, naphthalene, or pyrene, but not the other PAHs, suggest that members of the genera Cupriavidus and Luteimonas may have been associated with BaP mineralization. PMID:25469077

  11. Kinetics of carbon mineralization of biochars compared with wheat straw in three soils.

    PubMed

    Qayyum, Muhammad Farooq; Steffens, Diedrich; Reisenauer, Hans Peter; Schubert, Sven

    2012-01-01

    Application of biochars to soils may stabilize soil organic matter and sequester carbon (C). The objectives of our research were to study in vitro C mineralization kinetics of various biochars in comparison with wheat straw in three soils and to study their contribution to C stabilization. Three soils (Oxisol, Alfisol topsoil, and Alfisol subsoil) were incubated at 25C with wheat straw, charcoal, hydrothermal carbonization coal (HTC), low-temperature conversion coal (LTC), and a control (natural organic matter). Carbon mineralization was analyzed by alkali absorption of CO released at regular intervals over 365 d. Soil samples taken after 5 and 365 d of incubation were analyzed for soluble organic C and inorganic N. Chemical characterization of biochars and straw for C and N bonds was performed with Fourier transformation spectroscopy and with the N fractionation method, respectively. The LTC treatment contained more N in the heterocyclic-bound N fraction as compared with the biochars and straw. Charcoal was highly carbonized when compared with the HTC and LTC. The results show higher C mineralization and a lower half-life of straw-C compared with biochars. Among biochars, HTC showed some C mineralization when compared with charcoal and LTC over 365 d. Carbon mineralization rates were different in the three soils. The half-life of charcoal-C was higher in the Oxisol than in the Alfisol topsoil and subsoil, possibly due to high Fe-oxides in the Oxisol. The LTC-C had a higher half-life, possibly due to N unavailability. We conclude that biochar stabilization can be influenced by soil type. PMID:22751064

  12. [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. PMID:25508755

  13. [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. PMID:25474976

  14. Organic matter mineralization in frozen boreal soils-environmental constraints on catabolic and anabolic microbial activity

    NASA Astrophysics Data System (ADS)

    Oquist, Mats G.; Sparrman, Tobias; Schleucher, Jürgen; Nilsson, Mats B.

    2014-05-01

    Heterotrophic microbial mineralization of soil organic matter (SOM) and associated production and emission of atmospheric trace gases proceed during the winter months in the frozen soils of high latitude ecosystems. However, in what ways this microbial activity is constrained by the environmental conditions prevailing in a frozen soil matrix is uncertain. This presentation will address how temperature, water availability and substrate availability combine to regulate rates of microbial activity at below freezing temperatures and the implications of this activity for SOM mineralization in the surface layers of boreal forest soils experiencing seasonal freezing. We show that the amount and availability of liquid water is an integral factor regulating rates of microbial activity in the frozen soil matrix and can also explain frequently observed deviations in the temperature responses of biogenic CO2 production in frozen soils, as compared to unfrozen soils. Using stable isotope labeling (13C) we also show that the partitioning of substrate carbon, in the form of monomeric sugar (glucose), for catabolic and anabolic metabolism remain constant in the temperature range of -4C to 9C. This confirms that microbial growth may proceed even when soils are frozen. In addition we present corresponding data for organisms metabolizing polymeric substrates (cellulose) requiring exoenzymatic activity prior to substrate uptake. We conclude that the metabolic response of soil microorganism to controlling factors may change substantially across the freezing point of soil water, and also the patterns of interaction among controlling factors are affected. Thus, it is evident that metabolic response functions derived from investigations of unfrozen soils cannot be superimposed on frozen soils. Nonetheless, the soil microbial population appear very adapted to seasonal freezing with respect to their metabolic performance.

  15. Clay mineral formation and transformation in rocks and soils

    USGS Publications Warehouse

    Eberl, D.D.

    1983-01-01

    Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for the origin of clay minerals in nature. Several of these possibilities are discussed in terms of the rock cycle. The mineralogy of clays neoformed in the weathering environment is a function of solution chemistry, with the most dilute solutions favoring formation of the least soluble clays. After erosion and transportation, these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size. Clays undergo little reaction in the ocean, except for ion exchange and the neoformation of smectite; therefore, most clays found on the ocean floor are inherited from adjacent continents. Upon burial and heating, however, dioctahedral smectite reacts in the diagenetic environment to yield mixed-layer illite-smectite, and finally illite. With uplift and weathering, the cycle begins again. Refs.

  16. Microbial carbon mineralization in tropical lowland and montane forest soils of Peru

    PubMed Central

    Whitaker, Jeanette; Ostle, Nicholas; McNamara, Niall P.; Nottingham, Andrew T.; Stott, Andrew W.; Bardgett, Richard D.; Salinas, Norma; Ccahuana, Adan J. Q.; Meir, Patrick

    2014-01-01

    Climate change is affecting the amount and complexity of plant inputs to tropical forest soils. This is likely to influence the carbon (C) balance of these ecosystems by altering decomposition processes e.g., “positive priming effects” that accelerate soil organic matter mineralization. However, the mechanisms determining the magnitude of priming effects are poorly understood. We investigated potential mechanisms by adding 13C labeled substrates, as surrogates of plant inputs, to soils from an elevation gradient of tropical lowland and montane forests. We hypothesized that priming effects would increase with elevation due to increasing microbial nitrogen limitation, and that microbial community composition would strongly influence the magnitude of priming effects. Quantifying the sources of respired C (substrate or soil organic matter) in response to substrate addition revealed no consistent patterns in priming effects with elevation. Instead we found that substrate quality (complexity and nitrogen content) was the dominant factor controlling priming effects. For example a nitrogenous substrate induced a large increase in soil organic matter mineralization whilst a complex C substrate caused negligible change. Differences in the functional capacity of specific microbial groups, rather than microbial community composition per se, were responsible for these substrate-driven differences in priming effects. Our findings suggest that the microbial pathways by which plant inputs and soil organic matter are mineralized are determined primarily by the quality of plant inputs and the functional capacity of microbial taxa, rather than the abiotic properties of the soil. Changes in the complexity and stoichiometry of plant inputs to soil in response to climate change may therefore be important in regulating soil C dynamics in tropical forest soils. PMID:25566230

  17. Microbial carbon mineralization in tropical lowland and montane forest soils of Peru.

    PubMed

    Whitaker, Jeanette; Ostle, Nicholas; McNamara, Niall P; Nottingham, Andrew T; Stott, Andrew W; Bardgett, Richard D; Salinas, Norma; Ccahuana, Adan J Q; Meir, Patrick

    2014-01-01

    Climate change is affecting the amount and complexity of plant inputs to tropical forest soils. This is likely to influence the carbon (C) balance of these ecosystems by altering decomposition processes e.g., "positive priming effects" that accelerate soil organic matter mineralization. However, the mechanisms determining the magnitude of priming effects are poorly understood. We investigated potential mechanisms by adding (13)C labeled substrates, as surrogates of plant inputs, to soils from an elevation gradient of tropical lowland and montane forests. We hypothesized that priming effects would increase with elevation due to increasing microbial nitrogen limitation, and that microbial community composition would strongly influence the magnitude of priming effects. Quantifying the sources of respired C (substrate or soil organic matter) in response to substrate addition revealed no consistent patterns in priming effects with elevation. Instead we found that substrate quality (complexity and nitrogen content) was the dominant factor controlling priming effects. For example a nitrogenous substrate induced a large increase in soil organic matter mineralization whilst a complex C substrate caused negligible change. Differences in the functional capacity of specific microbial groups, rather than microbial community composition per se, were responsible for these substrate-driven differences in priming effects. Our findings suggest that the microbial pathways by which plant inputs and soil organic matter are mineralized are determined primarily by the quality of plant inputs and the functional capacity of microbial taxa, rather than the abiotic properties of the soil. Changes in the complexity and stoichiometry of plant inputs to soil in response to climate change may therefore be important in regulating soil C dynamics in tropical forest soils. PMID:25566230

  18. Anaerobic mineralization of indigenous organic matters and methanogenesis in tropical wetland soils

    SciTech Connect

    Miyajima, Toshihiro; Wada, Eitaro; Hanba, Yuko T.; Vijarnsorn, P.

    1997-09-01

    Tropical wetlands are one of the largest natural sources in the global methane budget due to high biological activities and the anaerobiosis in soil. We studied mineralization and gas production during the early stage of anaerobic decomposition of indigenous organic matters in soils of Narathiwat, southern Thailand, to clarify the significance of the substrate quality in controlling decomposition and methanogenesis in some different tropical wetland soils. The optimal temperature of decomposition was around 35{degrees}C, while methanogenesis did not proceed at 45{degrees}C. During the first 50 days of anaerobic incubation, 5 {approximately} 63% (carbon basis) of indigeneous plant leaves were mineralized. The mineralization rate was strongly and negatively correlated with the lignin and/or fiber contents, but not the C/N ratio, of the substrate plant materials. Difference in {delta}{sup 13}C between the substrate, indicating that H{sub 2} as opposed to acetate becomes a more important metabolic intermediate in the anaerobic food web when the decomposition rate is limited by substrate recalcitrance. Thus, the CH{sub 4} isotope signature may be used to evaluate the importance of new vs. old organic matter as CH{sub 4} isotope signature may be used to evaluate the importance of new vs. old organic matter as CH{sub 4} source in natural soils. The mineralization rate was higher, and the isotopic difference between the substrate and CH{sub 4} was smaller when plant materials were incubated with sulfate-contaminated soils than with native peat soils. The isotopic difference between the substrate and CH{sub 4} was significantly different between native peat soils. Results of a tracer experiment using {sup 13}C-labeled substrates indicated that these differences could be ascribed to difference in the mode of acetate metabolism between soils. 49 refs., 8 figs., 7 tabs.

  19. Carbon delivery to deep mineral horizons in Hawaiian rain forest soils

    NASA Astrophysics Data System (ADS)

    Marin-Spiotta, Erika; Chadwick, Oliver A.; Kramer, Marc; Carbone, Mariah S.

    2011-09-01

    This study aimed to better understand the mechanisms for soil organic matter delivery to and accumulation in mineral horizons of tropical rain forest, volcanic soils. We used soil morphology, lysimetry, isotopes, and spectroscopy to investigate the role of preferential flow paths in the delivery of carbon (C) to the subsoil. High rainfall, high primary productivity, and the dominance of highly reactive, short-range-order minerals combine to sequester substantial stocks of soil C with long mean residence times. The soils have large peds, separated by wide cracks, which form a network of channels propagating downward through the top 40 to 60 cm, facilitating macropore flow. The channel infillings and crack surfaces were enriched in organic material (OM) with lower C:N ratios, and had higher ammonium oxalate-extractable Al, and lower ammonium oxalate-extractable Fe than the adjacent mineral bulk soil. CP MAS 13C-NMR spectra of OM accumulating at depth showed strong signal intensities in the carboxyl and carbonyl C regions, indicative of organic acids, while decaying roots showed greater contributions of aromatic and O-alkyl C. The ratios of alkyl-to-O-alkyl C in the organic infillings were more similar to those of the bulk Bh and to dissolved organic matter than to those of decaying roots. Radiocarbon-based ages of OM infillings at >50 cm depth were significantly younger than the mineral soil (2000 years versus 7000 years). Respired CO2 from incubated soils showed that OM accumulating at depth is a mixture of modern and much older C, providing further evidence for the downward movement of fresh C.

  20. Anaerobic mineralization of indigenous organic matters and methanogenesis in tropical wetland soils

    NASA Astrophysics Data System (ADS)

    Miyajima, Toshihiro; Wada, Eitaro; Hanba, Yuko T.; Vijarnsorn, Pisoot

    1997-09-01

    Tropical wetlands are one of the largest natural sources in the global methane budget due to high biological activities and the anaerobiosis in soil. We studied mineralization and gas production during the early stage of anaerobic decomposition of indigenous organic matters in soils of Narathiwat, southern Thailand, to clarify the significance of the substrate quality in controlling decomposition and methanogenesis in some different tropical wetland soils. The optimal temperature of decomposition was around 35C, while methanogenesis did not proceed at 45C. During the first 50 days of anaerobic incubation, 5 63% (carbon basis) of indigenous plant leaves were mineralized. The mineralization rate was strongly and negatively correlated with the lignin and/or fiber contents, but not theC/N ratio, of the substrate plant materials. Difference in ? 13C between the substrate and the produced CH 4 was generally greater (more negative in CH 4) for more recalcitrant substrates, indicating that H 2 as opposed to acetate becomes a more important metabolic intermediate in the anaerobic food web when the decomposition rate is limited by substrate recalcitrance. Thus, the CH 4 isotope signature may be used to evaluate the importance of new vs. old organic matter as CH 4 source in natural soils. The mineralization rate was higher, and the isotopic difference between the substrate and CH 4 was smaller when plant materials were incubated with sulfate-contaminated soils than with native peat soils. The isotopic difference between the substrate and CH 4 was significantly different between native peat soils. Results of a tracer experiment using 13C-labeled substrates indicated that these differences could be ascribed to difference in the mode of acetate metabolism between soils.

  1. Natural abundance measurements of 13C indicate increased deep soil carbon mineralization after forest disturbance

    NASA Astrophysics Data System (ADS)

    Diochon, Amanda; Kellman, Lisa

    2008-07-01

    Northern forest soils represent globally important stores of carbon (C), yet there is no consensus about how they are altered by the widespread practice of harvesting that dominates many forested landscapes. Here we present the first study to systematically investigate the utility of δ 13C and C content depth profiles to infer temporal changes in belowground carbon cycling processes following disturbance in a pure C3 ecosystem. We document carbon concentration and δ 13C depth profile enrichment trends consistent with a kinetic fractionation arising from soil organic carbon (SOC) humification across a northern forest chronosequence (1, 15, 45, 80 and 125+ yrs). Reduced soil C storage that coincided with observed soil profile δ 13C-enrichment patterns which intensified following clearcut harvesting, pointed to losses of SOC in the deeper (>20 cm) mineral soil. This study suggests the δ 13C approach may assist in identifying mechanisms responsible for soil C storage changes in disturbed C3 forest ecosystems.

  2. Why is Mineral-Associated Organic Matter Enriched in 15N? Evidence from Grazed Pasture Soil

    NASA Astrophysics Data System (ADS)

    Baisden, W. T.; Wells, N. S.; Mudge, P. L.; Clough, T. J.; Schipper, L. A.; Ghani, A.; Stevenson, B.

    2014-12-01

    Throughout the scientific literature, measurements across soil depth and density fractions suggest that, with few exceptions, mineral-associated organic matter (OM) has higher ?15N than non-mineral-associated OM. This implies that the ?15N difference between N inputs and mineral-stabilized OM may characterize the microbial processes involved in stabilization and mineral association. Yet current understanding of observed N isotope fractionation in terrestrial ecosystems suggests the large isotope effects are expressed during inorganic N transformations from NH4 to gaseous loss pathways of NH3 volatilization and denitrification. How can the relative importance of N isotope fractionation during OM stabilization versus loss pathways be resolved? We recently examined N isofluxes when a temporary nitrogen excess is created by urine deposition in a New Zealand dairy pasture. We found that the N isotopic composition of volatilized NH3, and NO3 available for leaching or denitrification could not be linked back to the added N using Rayleigh distillation models. Instead, the results imply that the added N was immobilized, and the N available for losses was increasingly derived from mineralization of organic matter during the course of the experiment. These results are consistent with recent evidence of enhanced OM mineralization in urine patches, understanding of N isotope mass balances and long-standing evidence that gross mineralization and immobilization fluxes greatly exceed net mineralization and nitrification, except at very high N saturation. These results suggest that where 15N enrichment occurs due to fractionating loss pathways, the isotope effects are primarily transmitted to immobilized N, forming 15N enriched stabilized OM. This further explains earlier findings that the ?15N of soil OM represents an integrated indicator of losses, reflecting the intensity and duration of pastoral agriculture. We suggest that development of an indicator based on ?15N in mineral-associated OM might relate mineralization rates to the ?15N of stabilized or immobilized N.

  3. ROLE OF SOIL ORGANIC ACIDS IN MINERAL WEATHERING PROCESSES

    EPA Science Inventory

    The soluble organic acids in soils consist largely of complex mixtures of polymeric compounds referred to collectively as fluvic and humic acids. These compounds are relatively refactory, and are broken down only slowly by bacteria. ow-molecular-mass acids (e.g., acetic, oxalic, ...

  4. Impact of soils minerals and properties with application of MSMA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Straighthead is a physiological disorder of rice and threatens rice production in southern states. It is know that arsenic (As) is closely associated with occurrence of straighthead, so soil application of MSMA (monosodium methanearsonate) is commonly used to study this disease. Analysis was conduct...

  5. Ethylene Dibromide Mineralization in Soils under Aerobic Conditions

    PubMed Central

    Pignatello, Joseph J.

    1986-01-01

    1,2-Dibromoethane (EDB), which is a groundwater contaminant in areas where it was once used as a soil fumigant, was shown to be degraded aerobically by microorganisms in two types of surface soils from an EDB-contaminated groundwater discharge area. At initial concentrations of 6 to 8 ?g/liter, EDB was degraded in a few days to near or below the detection limit of 0.02 ?g/liter. At 15 to 18 mg/liter, degradation was slower. Bromide ion release at the higher concentrations was 1.4 0.3 and 2.1 0.2 molar equivalents for the two soils. Experiments with [14C]EDB showed that EDB was converted to approximately equal amounts of CO2 and apparent cellular carbon; only small amounts of added 14C were not attributable to these products or unreacted EDB. These results are encouraging, because they indicate that groundwater bacteria may hasten the removal of EDB from contaminated aerobic groundwater supplies. This report also provides evidence for soil-mediated chemical transformations of EDB. PMID:16347020

  6. Characterization of minerals: From the classroom to soils to talc deposits

    NASA Astrophysics Data System (ADS)

    McNamee, Brittani D.

    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 to identify any mineral. Students begin with familiarizing themselves with the tools (e.g. Polarizing Light Microscope and refractive index liquids) and the methods (e.g. defining properties) needed to identify a mineral. Next, they work through characterizing the most common minerals to hone their skills. The students finish the semester with two projects: characterizing single mineral grains with a spindle stage and creating a mineral collection. Evaluation of mineralogical data from selected sand or silt fraction of soils from the USDA-NRCS National Cooperative Soil Survey database, show that soils in all states (except for Rhode Island) contain amphiboles. Forty-one of the fifty states had 10 % or more sampled pedons containing amphiboles. Overall, about 13 % of pedons sampled in the USA contained amphiboles. While amphibole asbestos deposits occur in mafic and ultramafic provinces, soil amphiboles occur evenly distributed across the USA. The majority of the amphiboles found in the soils would probably not meet the mineralogical definition of asbestos (i.e., they would not have been derived from asbestiform amphiboles); however, the majority would probably meet a commonly used regulatory definition to be considered a fiber (i.e., are over 5 microns in length with a greater that 3 to 1 aspect ratio). Furthermore, chemical and morphological characterization was done on minerals in talc deposits and R. T. Vanderbilt Co. processed talc products from the Gouverneur Mining District, New York. The main mineral phases detected within the samples are tremolite, anthophyllite, and talc. Compositional analyses were preformed by WDS via electron microprobe. Morphological analyses were done using the PLM and electron microprobe. Amounts of each mineralogical phase were calculated by the Reitveld method using X-ray diffraction scans.

  7. The influence of biological soil crusts on mineral uptake by associated vascular plants

    USGS Publications Warehouse

    Harper, K.T.; Belnap, Jayne

    2001-01-01

    Soil surfaces dominated by cyanobacteria and cyanolichens (such as Collema sp.) are widespread in deserts of the world. The influence of these biological soil crusts on the uptake of bioessential elements is reported for the first time for six seed plants of the deserts of Utah. This sample almost doubles the number of species for which the influence of biological soil crusts on mineral uptake of associated vascular plants is known. These new case studies, and others previously published, demonstrate that cyanobacterial or cyanobacteria- Collema crusts significantly alter uptake by plants of many bioessential elements. In studies now available, these crusts always increase the N content of associated seed plants. Uptake of Cu, K, Mg, and Zn is usually (>70% of reported cases) increased in the presence of the biological soil crusts. Soil crusts are generally negatively associated with Fe and P levels in associated seed plant tissue, while plant tissue levels of Ca, Mn, and Na are positively as often as negatively associated with the presence of soil crusts. Increases in bioessential elements in vascular plant tissue from biologically-crusted areas are greatest for short-lived herbs that are rooted primarily within the surface soil, the horizon most influenced by crustal organisms. The mineral content of a deeply rooted shrub (Coleogyne ramosissima) was less influenced by co-occurrence of biological soil crusts.

  8. The role of organic matter in controlling aluminum solubility in acidic mineral soil horizons

    NASA Astrophysics Data System (ADS)

    Berggren, Dan; Mulder, Jan

    1995-10-01

    Despite the ecological importance of potentially phytotoxic Al, its solubility control in acidic mineral soils remains unresolved. We examined the solubility of Al in mineral horizons of two acidic forest soils (Inceptisol and Spodosol) in southern Sweden using a series of batch experiments. Dissolution of Al was found to consist of a rapid solubilization of reactive solid phase Al, which quickly reached an equilibrium state, superimposed on a slow dissolution of less reactive Al-containing phases (e.g., primary Al-silicates). Titration experiments in the pH range 3.2-4.7 using an equilibration time of 5 days showed that at pH < 4.1, all suspensions were undersaturated with respect to gibbsite (Al(OH) 3; log ?K SO = 8.85 at 8 C) . Under such conditions, the Al solubility could be explained qualitatively by equilibrium complexation reactions with soil organic matter. Quantitatively, our results could be reproduced reasonably well using the mechanistic model WHAM, which describes the binding of Al by humic substances in organic soils. This suggests that the pool of organically bound soil Al controls the Al solubility in suspensions of strongly acidic soils. Due to the kinetically constrained release of Al from primary and secondary minerals, the amount of organically bound Al, and therefore the Al solubility in the suspensions, gradually increases with time. Consequently, a quantitative evaluation of Al solubility data from long-term batch experiments should consider both equilibrium and kinetic processes.

  9. Organic farming and cover crops as an alternative to mineral fertilizers to improve soil physical properties

    NASA Astrophysics Data System (ADS)

    Sánchez de Cima, Diego; Luik, Anne; Reintam, Endla

    2015-10-01

    For testing how cover crops and different fertilization managements affect the soil physical properties in a plough based tillage system, a five-year crop rotation experiment (field pea, white potato, common barley undersown with red clover, red clover, and winter wheat) was set. The rotation was managed under four different farming systems: two conventional: with and without mineral fertilizers and two organic, both with winter cover crops (later ploughed and used as green manure) and one where cattle manure was added yearly. The measurements conducted were penetration resistance, soil water content, porosity, water permeability, and organic carbon. Yearly variations were linked to the number of tillage operations, and a cumulative effect of soil organic carbon in the soil as a result of the different fertilization amendments, organic or mineral. All the systems showed similar tendencies along the three years of study and differences were only found between the control and the other systems. Mineral fertilizers enhanced the overall physical soil conditions due to the higher yield in the system. In the organic systems, cover crops and cattle manure did not have a significant effect on soil physical properties in comparison with the conventional ones, which were kept bare during the winter period. The extra organic matter boosted the positive effect of crop rotation, but the higher number of tillage operations in both organic systems counteracted this effect to a greater or lesser extent.

  10. Reversibility of soil forming clay mineral reactions induced by plant - clay interactions

    NASA Astrophysics Data System (ADS)

    Barr, P.; Velde, B.

    2012-04-01

    Recent data based upon observations of field experiments and laboratory experiments suggest that changes in phyllosilicate mineralogy, as seen by X-ray diffraction analysis, which is induced by plant action can be reversed in relatively short periods of time. Changes from diagenetic or metamorphic mineral structures (illite and chlorite) to those found in soils (mixed layered minerals in the smectite, hydroxy-interlayer mineral and illites) observed in Delaware Bay salt marsh sediments in periods of tens of years and observed under different biologic (mycorhize) actions in coniferous forests in the soil environment can be found to be reversed under other natural conditions. Reversal of this process (chloritisation of smectitic minerals in soils) has been observed in natural situations over a period of just 14 years under sequoia gigantia. Formation of smectite minerals from illite (potassic mica-like minerals) has been observed to occur under intensive agriculture conditions over periods of 80 years or so under intensive zea mais production. Laboratory experiments using rye grass show that this same process can be accomplished to a somewhat lesser extent after one growing season. However experiments using alfalfa for 30 year growing periods show that much of the illite content of a soil can be reconstituted or even increased. Observations on experiments using zea mais under various fertilizer and mycorhize treatments indicate that within a single growing season potassium can be extracted from the clay (illite layers) but at the end of the season the potassium can be restored to the clay structures and more replaced that extracted. Hence it is clear that the change in clay mineralogy normally considered to be irreversible, illite to smectite or chlorite to smectite observed in soils, is a reversible process where plant systems control the soil chemistry and the soil mineralogy. The changes in clay mineralogy concern mostly the chemical composition of the interlayer ion population of a 2:1 clay structure. However the differences in interlayer ion chemistry give us such mineral names as chloritic hydroxyinterlayered mineral (Mg, OH interlayer), illite (K interlayer), and smectite (essentially hydrated Ca interlayer ions). Extraction of these interlayer ions can be reversed by chemistry engendered by plant regimes.

  11. Minerals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fish require the same minerals or inorganic elements as terrestrial animals for tissue formation, osmoregulation and various metabolic functions. Those required in large quantities are termed macro- or major minerals and those required in small quantities are called micro- or trace minerals. Fish ca...

  12. Redistributed water by saprotrophic fungi triggers carbon mineralization in dry soils

    NASA Astrophysics Data System (ADS)

    Guhr, Alexander; Borken, Werner; Matzner, Egbert

    2015-04-01

    Summer droughts are common in temperate forests and especially the upper soil horizons experience soil drought. Drought events can be accompanied by negative effects for forest ecosystems but many plants can reduce drought stress by hydraulic redistribution (HR). Similar processes were recently described for ectomycorrhizal networks but no information is available for mycelia networks of saprotrophic fungi. They strongly contribute to belowground nutrient cycling, C and N mineralization. We hypothesize that redistributed water by saprotrophic fungi triggers mineralization of organic matter in soils under drought conditions. The impact of HR by saprotrophic fungi on mineralization was determined using mesocosms comprising two chambers, separated by a 2 mm air gap to prevent bulk flow of water. After inoculation with fungal cultures and a growth phase, both chambers were desiccated. Subsequently, only chamber I was rewetted while chamber II was treated with 13C labelled plant material. CO2 samples were collected over 7 days after rewetting and analyzed for stable isotope ratio. In addition, enzymatic activity of chitinases and cellobiohydrolases in chamber II was determined after 7 days using the soil zymographie method with fluorogenic 4-Methylumbelliferyl-substrates. A negative control was provided by mesocosms in which hyphal connections between the chambers were severed before rewetting. Intact fungal connections between the chambers led to a strong increase in volumetric water content in chamber II after rewetting of chamber I and the CO2 had a higher enrichment in 13C than in the control mescosms with severed connections. Enrichment started 48 h after rewetting and continued for the rest of the experiment. This resulted in a more than two fold higher total carbon mineralization after 7 days in chamber II of mesocosms with intact hyphal connections. In addition, enzyme activities were also strongly increased compared to controls. In conclusion, mycelia networks of saprotrophic fungi contribute to redistribution of water from wet to dry soil and the redistributed water triggers carbon mineralization in dry soils.

  13. [Effects of different types of litters on soil organic carbon mineralization].

    PubMed

    Shi, Xue-Jun; Pan, Jian-Jun; Chen, Jin-Ying; Yang, Zhi-Qiang; Zhang, Li-Ming; Sun, Bo; Li, Zhong-Pei

    2009-06-15

    Using litter incubation experiment in laboratory, decomposition discrepancies of four typical litters from Zijin Mountain were analyzed. The results show that organic carbon mineralization rates of soil with litters all involve fast and slow decomposition stages, and the differences are that the former has shorter duration,more daily decomposition quantity while the latter is opposite. Organic carbon mineralization rates of soil with litters rapidly reached maximum in the early days of incubation, and the order is soil with Cynodon dactylon litter (CK + BMD) (23.88 +/- 0.62) mg x d(-1), soil with Pinus massoniana litter (CK+ PML) (17.93 +/- 0.99) mg x d(-1), soil with Quercus acutissima litter (CK+ QAC) (15.39 +/- 0.16) mg x d(-1) and soil with Cyclobalanopsis glauca litter (CK + CGO) (7.26 +/- 0.34) mg x d(-1), and with significant difference between each other (p < 0.05). This order has not significant correlation to litter initial chemical elements. The amount of organic carbon mineralized accumulation within three months incubation is (CK + BMD) (338.21 +/- 6.99) mg, (CK + QAC) (323.48 +/- 13.68) mg, (CK + PML) (278.34 +/- 13.91) mg and (CK + CGO) (245.21 +/- 4.58) mg. 198.17-297.18 mg CO2-C are released during litter incubation, which occupies 20.29%-31.70% of the total litter organic carbon amounts. Power curve model can describe the trends of organic carbon mineralization rate and mineralized accumulation amount,which has a good correlation with their change. PMID:19662876

  14. Microbial nitrogen dynamics in organic and mineral soil horizons along a latitudinal transect in western Siberia

    NASA Astrophysics Data System (ADS)

    Wild, Birgit; Schnecker, Jörg; Knoltsch, Anna; Takriti, Mounir; Mooshammer, Maria; Gentsch, Norman; Mikutta, Robert; Alves, Ricardo J. Eloy; Gittel, Antje; Lashchinskiy, Nikolay; Richter, Andreas

    2015-05-01

    Soil N availability is constrained by the breakdown of N-containing polymers such as proteins to oligopeptides and amino acids that can be taken up by plants and microorganisms. Excess N is released from microbial cells as ammonium (N mineralization), which in turn can serve as substrate for nitrification. According to stoichiometric theory, N mineralization and nitrification are expected to increase in relation to protein depolymerization with decreasing N limitation, and thus from higher to lower latitudes and from topsoils to subsoils. To test these hypotheses, we compared gross rates of protein depolymerization, N mineralization and nitrification (determined using 15N pool dilution assays) in organic topsoil, mineral topsoil, and mineral subsoil of seven ecosystems along a latitudinal transect in western Siberia, from tundra (67°N) to steppe (54°N). The investigated ecosystems differed strongly in N transformation rates, with highest protein depolymerization and N mineralization rates in middle and southern taiga. All N transformation rates decreased with soil depth following the decrease in organic matter content. Related to protein depolymerization, N mineralization and nitrification were significantly higher in mineral than in organic horizons, supporting a decrease in microbial N limitation with depth. In contrast, we did not find indications for a decrease in microbial N limitation from arctic to temperate ecosystems along the transect. Our findings thus challenge the perception of ubiquitous N limitation at high latitudes, but suggest a transition from N to C limitation of microorganisms with soil depth, even in high-latitude systems such as tundra and boreal forest.

  15. Nitrogen mineralization and nitrate leaching of a sandy soil amended with different organic wastes.

    PubMed

    Burgos, Pilar; Madejn, Engracia; Cabrera, Francisco

    2006-04-01

    Organic wastes can be recycled as a source of plant nutrients, enhancing crop production by improving soil quality. However, the study of the dynamic of soil nutrient, especially the N dynamic, after soil application of any organic material is vital for assessing a correct and effective use of the material, minimizing the losses of nitrate in leachates and avoiding the negative environmental effects that it may cause in groundwater. To estimate the effect of three organic materials, a municipal solid waste compost (MWC), a non-composted paper mill sludge (PS), and an agroforest compost (AC) on the N dynamic of a sandy soil two experiments were carried out: an incubation experiment and a column experiment. The incubation experiment was conducted to estimate the N mineralization rate of the different soil-amendment mixtures. The soil was mixed with the organic amendments at a rate equivalent to 50,000 kg ha(-1) and incubated during 40 weeks at constant moisture content (70% of its water-holding capacity) and temperature (28 degrees C) under aerobic conditions. Organic amendment-soil samples showed an immobilization of N during the first weeks, which was more noticeable and longer in the case of PS-treated soil compared to the other two amendments due to its high C/N ratio. After this immobilization stage, a positive mineralization was observed for all treatment, especially in MWC treated soil. Contemporaneously a 1-year column (19 cm diameter and 60 cm height) experiment was carried out to estimate the nitrate losses from the soil amended with the same organic materials. Amendments were mixed with the top soil (0-15 cm) at a rate equivalent to 50,000 kg ha(-1). The columns were periodically irrigated simulating rainfall in the area of study, receiving in total 415 mm of water, and the water draining was collected during the experimental period and analysed for NO3-N. At the end of the experimental period NO3-N content in soil columns at three depths (0-20, 20-35 and 35-50 cm) was determined. The nitrate concentration in drainage water confirmed the results obtained in the incubation experiment: nitrate leaching was higher in soil treated with MWC due to its higher N-mineralization rate. Nevertheless, the nitrate losses represented a low amount compared with the total nitrogen added to soil. No clear signs of water-draining contamination were observed during the first year after the application of AC and PS; however, the nitrate leaching in soil treated with MWC slightly exceeded the limit allowed for the Drinking Water Directive 98/83/CE. PMID:16634232

  16. Reactive Clay Minerals in a land use sequence of disturbed soils of the Belgian Loam Belt

    NASA Astrophysics Data System (ADS)

    Barao, Lucia; Vandevenne, Floor; Ronchi, Benedicta; Meire, Patrick; Govers, Gerard; Struyf, Eric

    2014-05-01

    Clay minerals play a key role in soil biogeochemistry. They can stabilize organic matter, improve water storage, increase cation exchange capacity of the soil (CEC) and lower nutrient leaching. Phytoliths - the biogenic silica bodies (BSi) deposited in cell walls of plants - are important Si pools in soil horizons due to their higher solubility compared to minerals. They provide the source of Si for plant uptake in short time scales, as litter dissolves within soils. In a recent study, we analyzed the BSi pool differences across a set of different land uses (forests, pastures, croplands) in 6 long-term disturbed (multiple centuries) soil sites in the Belgium Loam Belt. Results from a simultaneous chemical extraction in 0.5M NaOH of Si and Al, showed that soils were depleted in the BSi pool while showing high levels of reactive secondary clay minerals, mainly in the deeper horizons and especially in the forests and the croplands. During the extraction, clays were similar in reactivity to the biogenic pool of phytoliths. In order to study the kinetics in a more natural environment, batch dissolution experiments were conducted. Samples from different soil depths for each land use site (0.5 g) were mixed with 0.5 L of demineralised water modified to pH 4, 7 and 10. Subsamples of 2 ml were taken during 3 months. In the end of the period, results for pH 7 showed that in the pastures, where reactive clays were almost absent, the ratio Si/RSi (defined as the Si concentration in the end of the batch experiment divided by the reactive silica extracted from the soil with the alkaline extraction) was lower than 0.005%. The same ratio was higher in the mineral horizons of forests (Si/RSi>0.01%) and croplands (0.005% < Si/RSi <0.01%) where clay minerals were the dominant fraction. These preliminary results highlight the clay minerals' strong potential for Si mobilization. More attention should be paid to this important fraction as it can contribute strongly to Si availability, in close competition with phytoliths and other soluble amorphous Si forms, strongly interfering with frequently applied methods to quantify biogenic Si in soils.

  17. Molecular-Level Analysis of Organic Matter Structure and Composition from Different Soil Mineral Fractions

    NASA Astrophysics Data System (ADS)

    Clemente, J. S.; Gregorich, E. G.; Simpson, A. J.; Simpson, M. J.

    2009-05-01

    The formation and turnover of soil organic matter (SOM) depends on the inherent chemical characteristics of biomolecular inputs (lignin, proteins, carbohydrates, macromolecular lipids, etc.) as well as the interactions between biomolecules and soil mineral fractions. The objective of this study is to characterize organic matter associated with the light, sand, silt and clay fractions of a Canadian agricultural soil. And, because lignin is believed to be a major contributor in SOM formation and preservation, the oxidation state of lignin in the different mineral fractions was measured using mild alkaline copper oxidation and gas chromatography - mass spectrometery which releases lignin phenols that are indicative of lignin sources and stage of degradation. For example, an increase in the acid/aldehyde (Ad/Al) ratio of lignin phenols has been observed with increased lignin degradation (and oxidation). In this study, lignin phenols from organic matter associated with the clay fraction had higher Ad/Al ratios for both syringyl and vanillyl lignin monomers when compared to that associated with silt, sand and the whole soil. These results suggest that either lignin degradation is enhanced by SOM association with clay surfaces or that oxidized lignin is preserved on clay mineral surfaces via sorption after partial degradation has occurred. The structural characteristics of organic matter from the soil fractions will also be examined by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Organic matter associated with each mineral fraction will be extracted with NaOH for high resolution solution-state NMR spectroscopy. Results from NMR analysis will determine the relative abundance of functional groups (alkane, aromatic, carbonyl, alkoxy) in each of the soil fractions. Relative intensities of the functional groups are indicative of relative contributions of biomolecular classes such as lipids, lignin, fatty acids, and sugars to the organic matter associated with each fraction. The study comprises our initial steps in characterizing protection mechanisms responsible for the long-term retention and stability of biomolecules and their degradation intermediates in soil.

  18. 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. PMID:24225344

  19. Mineral composition of native woody plants growing on a serpentine soil in California

    SciTech Connect

    Wallace, A.; Jones, M.B.; Alexander, G.V.

    1982-07-01

    Using optical emission spectrography, we analyzed leaves of five native plant species (Adenostoma fasciculatum, Arctostaphylos viscida, Cupressus macnabiana, Cupressus sargentii, and Quercus durata) for mineral elements. There were 112 plants in all. In these plants, which are reasonably adapted to serpentine soil conditions, the calcium:magnesium ratios were normal in contrast to plants not adapted to such soil conditions. The nickel concentrations in the leaves were low for serpentine soil conditions, and there was no tendency for accumulation of chromium or cobalt. Strontium varied, as did calcium.

  20. Toxicity of lead to soil respiration: mediation by clay minerals, humic acids, and compost

    SciTech Connect

    Debosz, K.; Babich, H.; Stotzky, G.

    1985-10-01

    Since Pb has no known biological function, elevated levels of Pb in soils and in other natural environments may adversely affect the indigenous biota, including the microbiota. Elevated levels of Pb in soil may also adversely affect microbemediated ecologic processes. There is, however, relatively little information on the mediating influence of the physicochemical factors of the recipient environment on the toxicity of Pb to microbe-mediated ecologic processes. This present study evaluated the influence of the clay minerals, kaolinite and montmorillonite, particulate humic acids, and compost on the degradation of glucose in soil.

  1. Modeling selenite adsorption envelopes on oxides, clay minerals, and soils using the triple layer model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenite adsorption behavior was investigated on amorphous aluminum and iron oxides, clay minerals: kaolinite, montmorillonite, and illite, and 45 surface and subsurface soil samples from the Southwestern and Midwestern regions of the USA as a function of solution pH. Selenite adsorption decreased ...

  2. Distinguishing boron desorption from mineral dissolution in arid-zone soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron release from six arid-zone soils from the San Joaquin Valley of California was investigated as a function of reaction time, solution pH, and suspension density. A multiple batch extraction experiment was carried out for 362 days to distinguish B desorption from mineral dissolution. Amounts o...

  3. MANURE PROPERTIES: EFFECT ON C AND N MINERALIZATION DURING LABORATORY INCUBATION OF MANURE AMENDED SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was carried out to examine C and N mineralization in soils amended with dairy manure. Our objectives were to study the relationship between manure properties, mineralizable N, nutrient pools, gas fluxes, and denitrification during laboratory incubation. Different dairy manures (n=107) were...

  4. Modeling selenate adsorption behavior on oxides, clay minerals, and soils using the triple layer model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenate adsorption behavior was investigated on amorphous aluminum oxide, amorphous iron oxide, goethite, clay minerals: kaolinites, montmorillonites, illite, and 18 soil samples from Hawaii, and the Southwestern and the Midwestern regions of the US as a function of solution pH. Selenate adsorpti...

  5. Long-Term Tillage and Poultry Litter Impacts Soil Carbon and Nitrogen Mineralization and Fertility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-term tillage and manure application are thought to alter the ability of the soil to sequester plant nutrients and mineralize carbon and nitrogen. Thus, a laboratory incubation study was conducted under aerobic conditions to evaluate the residual effect of long-term poultry litter (litter) appli...

  6. Sugarcane Genotype Selection Efficiency on Organic and Mineral Soils in Florida

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sugarcane (Saccharum spp.) genotype selection during the past 35 yrs has been more successful at developing cultivars for the organic (muck) than for the mineral (sand) soils in Florida, more likely a consequence of conducting the early and intermediate stages of selection exclusively on organic soi...

  7. Soil Property and Landscape Position Effects on Seasonal Nitrogen Mineralization of Composted Dairy Manure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To develop better management practices that optimize the amount of N derived from manure, more information is needed regarding the mineralization and dynamics of N under normal field conditions. Thus, an in situ field study, using three different soil types located in close proximity, was conducted ...

  8. 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 suspec

  9. The Accumulation of Organic Carbon in Mineral Soils by Afforestation of Abandoned Farmland

    PubMed Central

    Wei, Xiaorong; Qiu, Liping; Shao, Mingan; Zhang, Xingchang; Gale, William J.

    2012-01-01

    The afforestation of abandoned farmland significantly influences soil organic carbon (OC). However, the dynamics between OC inputs after afforestation and the original OC are not well understood. To learn more about soil OC dynamics after afforestation of farmland, we measured the soil OC content in paired forest and farmland plots in Shaanxi Province, China. The forest plots had been established on farmland 18, 24, 48, 100, and 200 yr previously. The natural 13C abundance of soil organic matter was also analyzed to distinguish between crop- and forest-derived C in the afforested soils. We observed a nonlinear accumulation of total OC in the 0–80 cm depth of the mineral soil across time. Total soil OC accumulated more rapidly under forest stands aged 18 to 48 yr than under forest stands aged 100 or 200 yrs. The rate of OC accumulation was also greater in the 0–10 cm depth than in the 10–80 cm depth. Forest-derived OC in afforested soils also accumulated nonlinearly across time, with the greatest increase in the 0–20 cm depth. Forest-derived OC in afforest soils accounted for 52–86% of the total OC in the 0–10 cm depth, 36–61% of the total OC in the 10–20 cm depth, and 11–50% of the total OC in the 20–80 cm depth. Crop-derived OC concentrations in the 0–20 cm depth decreased slightly after afforestation, but there was no change in crop-derived OC concentrations in the 20–80 cm depth. The results of our study support the claim that afforestation of farmland can sequester atmospheric CO2 by increasing soil OC stocks. Changes in the OC stocks of mineral soils after afforestation appear to be influenced mainly by the input of forest-derived C rather than by the loss of original OC. PMID:22412854

  10. 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.

  11. Disentangling controls on mineral-stabilized soil organic matter using a slurry incubation

    NASA Astrophysics Data System (ADS)

    Lavallee, J. M.; Cotrufo, M. F.; Paul, E. A.; Conant, R. T.

    2014-12-01

    Mineral-stabilized organic matter (OM) is the largest and oldest pool of soil carbon and nitrogen. Mineral stabilization limits OM availability to soil microbes, preventing its decomposition and prolonging its turnover. Thus, understanding controls on the decomposition of mineral-stabilized OM is key to understanding soil carbon and nitrogen dynamics. The very slow turnover of mineral-stabilized OM makes it challenging to study in a typical incubation, and as a result, many potential controls (temperature, OM chemistry, and mineralogy) on its turnover remain unclear. We aimed to better understand controls on decomposition of mineral-stabilized OM by employing a slurry incubation technique, which speeds up microbial processing of OM by maximizing OM accessibility to microbes. In a slurry incubation, we expect that any OM that is not stabilized on mineral surfaces will be available for decomposition and will be converted to CO2. Using this technique, we studied the interactive effects of incubation temperature, plant material type (aboveground vs. belowground), and soil fraction (silt vs. clay) on CO2 efflux and OM stabilization. We separated silt-sized and clay-sized fractions from an agricultural soil, added aboveground or belowground plant material to each, and incubated them at 15C, 25C and 35C. The added plant material was isotopically labeled (13C and 15N), which allowed us to trace it through the system and distinguish between the responses of the new (derived from the plant material) and old (derived from what was already present in the silt and clay) OM to warming. We measured CO2 efflux and 13CO2 efflux throughout the incubation. We performed one short-term harvest at day 6 and one final harvest at day 60. Initial results show higher cumulative CO2 efflux at warmer temperatures regardless of plant material type or soil fraction. A larger fraction of that CO2 came from OM that was initially present in the silt and clay, rather than from the plant material that we added, which suggests faster turnover of that "old" OM at warmer temperatures. We will present CO2 efflux data in addition to total [C] and [N] and the isotopic ratios of 13C and 15N in the silt and clay at each harvest to explain how the interactions between warming, plant material type and soil fraction affect turnover of mineral stabilized OM.

  12. Parameters of microbial respiration in soils of the impact zone of a mineral fertilizer factory

    NASA Astrophysics Data System (ADS)

    Zhukova, A. D.; Khomyakov, D. M.

    2015-08-01

    The carbon content in the microbial biomass and the microbial production of CO2 (the biological component of soil respiration) were determined in the upper layer (0-10 cm) of soils in the impact zone of the OJSC Voskresensk Mineral Fertilizers, one of the largest factories manufacturing mineral fertilizers in Russia. Statistical characteristics and schematic distribution of the biological parameters in the soil cover of the impact zone were analyzed. The degree of disturbance of microbial communities in the studied objects varied from weak to medium. The maximum value (0.44) was observed on the sampling plot 4 km away from the factory and 0.5 km away from the place of waste (phosphogypsum) storage. Significantly lower carbon content in the microbial biomass and its specific respiration were recorded in the agrosoddy-podzolic soil as compared with the alluvial soil sampled at the same distance from the plant. The effects of potential soil pollutants (fluorine, sulfur, cadmium, and stable strontium) on the characteristics of soil microbial communities were described with reliable regression equations.

  13. Endogeic earthworms shape bacterial functional communities and affect organic matter mineralization in a tropical soil

    PubMed Central

    Bernard, Laetitia; Chapuis-Lardy, Lydie; Razafimbelo, Tantely; Razafindrakoto, Malalatiana; Pablo, Anne-Laure; Legname, Elvire; Poulain, Julie; Brüls, Thomas; O'Donohue, Michael; Brauman, Alain; Chotte, Jean-Luc; Blanchart, Eric

    2012-01-01

    Priming effect (PE) is defined as a stimulation of the mineralization of soil organic matter (SOM) following a supply of fresh organic matter. This process can have important consequences on the fate of SOM and on the management of residues in agricultural soils, especially in tropical regions where soil fertility is essentially based on the management of organic matter. Earthworms are ecosystem engineers known to affect the dynamics of SOM. Endogeic earthworms ingest large amounts of soil and assimilate a part of organic matter it contains. During gut transit, microorganisms are transported to new substrates and their activity is stimulated by (i) the production of readily assimilable organic matter (mucus) and (ii) the possible presence of fresh organic residues in the ingested soil. The objective of our study was to see (i) whether earthworms impact the PE intensity when a fresh residue is added to a tropical soil and (ii) whether this impact is linked to a stimulation/inhibition of bacterial taxa, and which taxa are affected. A tropical soil from Madagascar was incubated in the laboratory, with a 13C wheat straw residue, in the presence or absence of a peregrine endogeic tropical earthworm, Pontoscolex corethrurus. Emissions of 12CO2 and 13CO2 were followed during 16 days. The coupling between DNA-SIP (stable isotope probing) and pyrosequencing showed that stimulation of both the mineralization of wheat residues and the PE can be linked to the stimulation of several groups especially belonging to the Bacteroidetes phylum. PMID:21753801

  14. Sorption of a nonionic surfactant Tween 80 by minerals and soils.

    PubMed

    Kang, Soyoung; Jeong, Hoon Young

    2015-03-01

    Batch experiments were conducted to evaluate Tween 80 sorption by oxides, aluminosilicates, and soils. For oxides, the sorption by silica and alumina follow linear isotherms, and that by hematite follows a Langmuir isotherm. Considering isotherm type and surface coverage, Tween 80 may partition into the silica/alumina-water interface, whereas it may bind to hematite surface sites. Among aluminosilicates, montmorillonite shows the greatest sorption due to the absorption of Tween 80 into interlayers. For other aluminosilicates, it sorbs to surfaces, with the sorption increasing as plagioclasesoils reveal that fine-grained clay minerals, difficult to separate by dry-sieving, contribute significantly to Tween 80 sorption. The greater sorption by untreated soils than H2O2-treated soils indicates that soil organic matter is a vital sorbent. The sorption hysteresis, contributed to by clay minerals and soil organic matter, is characterized by the greater sorption during the desorption than the sorption stages. This suggests the potential difficulty in removing surfactants from soils. Also, sorption of surfactants can adversely affect surfactant-enhanced remediation by decreasing the aquifer permeability and the availability of surfactants for micellar solubilization. PMID:25463228

  15. Calculating carbon mass balance from unsaturated soil columns treated with CaSO??minerals: test of soil carbon sequestration.

    PubMed

    Han, Young-Soo; Tokunaga, Tetsu K

    2014-12-01

    Renewed interest in managing C balance in soils is motivated by increasing atmospheric concentrations of CO2 and consequent climate change. Here, experiments were conducted in soil columns to determine C mass balances with and without addition of CaSO4-minerals (anhydrite and gypsum), which were hypothesized to promote soil organic carbon (SOC) retention and soil inorganic carbon (SIC) precipitation as calcite under slightly alkaline conditions. Changes in C contents in three phases (gas, liquid and solid) were measured in unsaturated soil columns tested for one year and comprehensive C mass balances were determined. The tested soil columns had no C inputs, and only C utilization by microbial activity and C transformations were assumed in the C chemistry. The measurements showed that changes in C inventories occurred through two processes, SOC loss and SIC gain. However, the measured SOC losses in the treated columns were lower than their corresponding control columns, indicating that the amendments promoted SOC retention. The SOC losses resulted mostly from microbial respiration and loss of CO2 to the atmosphere rather than from chemical leaching. Microbial oxidation of SOC appears to have been suppressed by increased Ca(2+) and SO4(2)(-) from dissolution of CaSO4 minerals. For the conditions tested, SIC accumulation per m(2) soil area under CaSO4-treatment ranged from 130 to 260 g C m(-1) infiltrated water (20-120 g C m(-1) infiltrated water as net C benefit). These results demonstrate the potential for increasing C sequestration in slightly alkaline soils via CaSO4-treatment. PMID:24974014

  16. Passive sequestration of atmospheric CO2 through coupled plant-mineral reactions in urban soils.

    PubMed

    Manning, David A C; Renforth, Phil

    2013-01-01

    Photosynthetic removal of CO(2) from the atmosphere is an important planetary carbon dioxide removal mechanism. Naturally, an amount equivalent to all atmospheric carbon passes through the coupled plant-soil system within 7 years. Plants cycle up to 40% of photosynthesized carbon through their roots, providing a flux of C at depth into the soil system. Root-exuded carboxylic acids have the potential to supply 4-5 micromoles C hr(-1)g(-1) fresh weight to the soil solution, and enhance silicate mineral weathering. Ultimately, the final product of these root-driven processes is CO(2), present in solution as bicarbonate. This combines with Ca liberated by corrosion associated with silicate mineral weathering to enter the soil-water system and to produce pedogenic calcium carbonate precipitates. Combining understanding of photosynthesis and plant root physiology with knowledge of mineral weathering provides an opportunity to design artificial soils or to plan land use in ways that maximize removal and sequestration of atmospheric CO(2) through artificially enhanced pedogenic carbonate precipitation. This process requires relatively low energy and infrastructure inputs. It offers a sustainable carbon dioxide removal mechanism analogous to the use of constructed wetlands for the passive remediation of contaminated waters, and is likely to achieve wide public acceptance. PMID:22616942

  17. The biological factors influence on the conversion of mineral components of Extremely Arid Desert Soils (Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Kutovaya, Olga; Vasilenko, Elena; Lebedeva, Marina; Tkhakakhova, Azida

    2013-04-01

    Extremely arid soils of stony deserts (hamadas) along the southern periphery of the Ili Depression are considered to be analogous to extremely arid soils of Mongolia, also named as "ultra-arid primitive gray-brown soils." In general, the morphology of extremely arid soils of hamadas in the Ili Depression is similar to that of the soils of stony deserts in other parts of the world, including the Gobi, Atacama, and Tarim deserts. The diagnostics of the active communities of microorganisms were performed according to the method of Rybalkina-Kononenko. The exact identification of the living forms of microorganisms to the species level is not always possible with the use of this method. However, it allows us to study the physiological role of the microorganisms and their ecological functions, including the relationships with the soil matrix and other organisms. In particular, it is possible to estimate the contribution of the microorganisms to the transformation of mineral soil components. The obtained materials allow us to conclude that the extremely arid desert soils are characterized by the very high biological activity during short periods of the increased soil moistening after rare and strong rains. The diversity of living forms is very considerable; both prokaryotes (cyanobacteria, actinomycetes, and iron bacteria) and protists (green algae, diatoms, and dinoflagellates) are developed in the soil. Thus, during a short period after the rains, these microorganisms pass from the stage of anabiosis to the stage of active growth and reproduction. Then, upon drying of the soil, the biotic activity of the soil slows down and, finally, terminates. The organisms remain in the state of anabiosis until the next rain. During the period of active growth, the microorganisms compose a specific consortium of different species and exert a profound impact on the soil properties. They participate in the transformation of the soil minerals with the formation of amorphous substances that are clearly seen in biofilms on the surface of gravels of the desert pavement and on the walls of vesicular pores in the crust and subcrust (AKL) horizons of the soil. The organomineral compounds are accumulated in the vesicular pores due to the synthesis and mineralization of the microbial biomass. This is a specific feature of the humus-accumulative process in the extremely arid desert soils. The biogenic transformation of iron-containing minerals, the mobility of iron, and its accumulation in films and coagulated microforms is largely due to the living activity of iron bacteria. These iron pedofeatures are specific of the extremely arid desert soils. We suppose that some part of vesicular pores in the AKL horizon has a microbiological origin, because separate bacterial cells may form intracellular gas vacuoles and extracellular gas bulbs, as well as membrane sacs and cell dilatations that can shape the vesicular pores. In general, our data indicate that soils, including extremely arid desert soils, serve as reservoirs of the microbial diversity and ensure the development and preservation of diverse microorganisms with specific mechanisms of adaptation to the sharp changes in the environmental conditions. This biota-protecting role of soils is particularly well pronounced during the climatic pessimum. This study was supported by the Russian Foundation for Basic Research, project no. 12-04-00990a.

  18. The Interfacial Behavior between Biochar and Soil Minerals and Its Effect on Biochar Stability.

    PubMed

    Yang, Fan; Zhao, Ling; Gao, Bin; Xu, Xiaoyun; Cao, Xinde

    2016-03-01

    In this study, FeCl3, AlCl3, CaCl2, and kaolinite were selected as model soil minerals and incubated with walnut shell derived biochar for 3 months and the incubated biochar was then separated for the investigation of biochar-mineral interfacial behavior using XRD and SEM-EDS. The XPS, TGA, and H2O2 oxidation were applied to evaluate effects of the interaction on the stability of biochar. Fe8O8(OH)8Cl1.35 and AlCl3·6H2O were newly formed on the biochar surface or inside of the biochar pores. At the biochar-mineral interface, organometallic complexes such as Fe-O-C were generated. All the 4 minerals enhanced the oxidation resistance of biochar surface by decreasing the relative contents of C-O, C═O, and COOH from 36.3% to 16.6-26.5%. Oxidation resistance of entire biochar particles was greatly increased with C losses in H2O2 oxidation decreasing by 13.4-79.6%, and the C recalcitrance index (R50,bicohar) in TGA analysis increasing from 44.6% to 45.9-49.6%. Enhanced oxidation resistance of biochar surface was likely due to the physical isolation from newly formed minerals, while organometallic complex formation was probably responsible for the increase in oxidation resistance of entire biochar particles. Results indicated that mineral-rich soils seemed to be a beneficial environment for biochar since soil minerals could increase biochar stability, which displays an important environmental significance of biochar for long-term carbon sequestration. PMID:26828311

  19. Low dissolved organic carbon input from fresh litter to deep mineral soils

    SciTech Connect

    Froeberg, Mats J; Jardine, Philip M; Hanson, Paul J; Swanston, Christopher; Todd Jr, Donald E; Phillips, Jana Randolph; Garten Jr, Charles T

    2007-01-01

    Dissolved organic carbon (DOC) leached from recent litter in the forest floor has been suggested to be an important source of C to the mineral soil of forest ecosystems. In order to determine the rate at which this flux of C occurs we have taken advantage of a local release of 14C at Oak Ridge National Laboratory Reservation, USA (latitude N 35 58'; longitude W 84 16'). Eight replicate 7x7 m plots were estab lished at four field sites on the reservation in an upland oak forest setting. Half of the plots were provided with 14C-enriched litter (?14C ?1000 ), and the other half with near-background litter (?14C ?220 ) over multiple years. Differences in the labeled leaf litter were used to quantify the movement of litter derived DOC through the soil profile. Soil solutions were collected over several years with tension lysimeters at 15 and 70 cm depth and measured for DOC concentration and 14C abundance. The net amount of DOC retained between 15 and 70 cm was 1.5-6 g m-2 y-1. There were significant effects of the litter additions on the 14C abundance in the DOC, but the net transport of 14C from the added litter was small. The difference in ?14C between the treatments with enriched and near-background litter was only about 130 at both depths, which is small compared with the difference in ?14C in the added litter. The primary source of DOC within the mineral soil must therefore have been either the Oe/Oa horizon or the organic matter in the mineral soil. Over a 2-year time frame, leaching of DOC from recent litter did not have a major impact on the C stock in the mineral soil below 15 cm in this ecosystem.

  20. Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)

    NASA Astrophysics Data System (ADS)

    Opolot, E.; Finke, P. A.

    2015-11-01

    Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic soil evolution models. This study applies a mechanistic soil evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other soil-forming processes and factors. The SoilGen soil evolution model is a 1-D model developed to simulate the time-depth evolution of soil properties as a function of various soil-forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling, and bioturbation) driven by soil-forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the soil solution composition play an equally important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates possibly due to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore a need to include secondary mineral precipitation mechanism in our formulation. In addition, there is a need for a more detailed study that is specific to field sites with detailed measurements of silicate mineral dissolution rates, climate, hydrology, and mineralogy to enable the calibration and validation of the model. Nevertheless, this study is another important step to demonstrate the critical need to couple different soil-forming processes with chemical weathering in order to explain differences observed between laboratory and field measured silicate mineral dissolution rates.

  1. Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)

    NASA Astrophysics Data System (ADS)

    Opolot, E.; Finke, P. A.

    2015-08-01

    Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic soil evolution models. This study applies a mechanistic soil evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other soil forming processes and factors. The SoilGen soil evolution model is a 1-D model developed to simulate the time-depth evolution of soil properties as a function of various soil forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling and bioturbation) driven by soil forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the soil solution composition equally play an important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates owing to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore need to include secondary mineral precipitation mechanism in our formulation. In addition, there is need for a more detailed study that is specific to field sites with detailed measurements of silicate mineral dissolution rates, climate, hydrology and mineralogy to enable the calibration and validation of the model. Nevertheless, this study is another important step to demonstrate the critical need to couple different soil forming processes with chemical weathering in order to explain differences observed between laboratory and field measured silicate mineral dissolution rates.

  2. Factors driving carbon mineralization priming effect in a soil amended with different types of biochar

    NASA Astrophysics Data System (ADS)

    Cely, P.; Tarquis, A. M.; Paz-Ferreiro, J.; Méndez, A.; Gascó, G.

    2014-03-01

    The effect of biochar on soil carbon mineralization priming effect depends on the characteristics of the raw materials, production method and pyrolysis conditions. The goal of the present study is to evaluate the impact of three different types of biochar on soil CO2 emissions and in different physicochemical properties. For this purpose, a sandy-loam soil was amended with the three biochars (BI, BII and BIII) at a rate of 8 wt % and soil CO2 emissions were measured for 45 days. BI is produced from a mixed wood sieving's from wood chip production, BII from a mixture of paper sludge and wheat husks and BIII from sewage sludge. Cumulative CO2 emissions of biochars, soil and amended soil were well fit to a simple first-order kinetic model with correlation coefficients (r2) greater than 0.97. Results shown a negative priming effect in the soil after addition of BI and a positive priming effect in the case of soil amended with BII and BIII. These results can be related with different biochar properties such as ash content, volatile matter, fixed carbon, organic carbon oxidised with dichromate, soluble carbon and metal and phenolic substances content in addition to surface biochar properties. Three biochars increased the values of soil field capacity and wilting point, while effects over pH and cation exchange capacity were not observed.

  3. Influence of edaphic factors on the mineralization of neem oil coated urea in four Indian soils.

    PubMed

    Kumar, Rajesh; Devakumar, C; Kumar, Dinesh; Panneerselvam, P; Kakkar, Garima; Arivalagan, T

    2008-11-12

    The utility of neem (Azadirachta indica A Juss) oil coated urea as a value-added nitrogenous fertilizer has been now widely accepted by Indian farmers and the fertilizer industry. In the present study, the expeller grade (EG) and hexane-extracted (HE) neem oils, the two most common commercial grades, were used to prepare neem oil coated urea (NOCU) of various oil doses, for which mineralization rates were assessed in four soils at three incubation temperatures (20, 27, and 35 degrees C). Neem oil dose-dependent conservation of ammonium N was observed in NOCU treatments in all of the soils. However, a longer incubation period and a higher soil temperature caused depletion of ammonium N. Overall, the nitrification in NOCU treatment averaged 56.6% against 77.3% for prilled urea in four soils. NOCU prepared from EG neem oil was consistently superior to that derived from hexane-extracted oil. The performance of NOCUs was best in coarse-textured soil and poorest in sodic soil. The nitrification rate (NR) of the NOCUs in the soils followed the order sodic > fine-textured > medium-textured > coarse-textured. The influence of edaphic factors on NR of NOCUs has been highlighted. The utility of the present study in predicting the performance of NOCU in diverse Indian soils was highlighted through the use of algorithms for computation of the optimum neem oil dose that would cause maximum inhibition of nitrification in any soil. PMID:18841982

  4. Microbial Mineralization of Soil Organic Matter: Role of Chemical Composition and Structural Organization

    NASA Astrophysics Data System (ADS)

    Khalaf, M. M. R.; Chilom, G.; Rice, J. A.

    2014-12-01

    The purpose of this study is to quantitatively assess the effect of organic matter self-assembly on its resistance to microbial mineralization. Humic acids isolated from leonardite, two peats and a mineral soil were used as organic matter samples because they provide a broad range of variability in terms of the origin and nature of their organic components. Using a solvent-based fractionation method, humic acid samples were disassembled into a humic-like component and a humic-lipid composite. The humic-lipid composite was further disassembled into an amphiphilic and a lipid component using an alkaline aqueous solution. Mixtures that reproduced the composition of self-assembled samples were prepared by mixing the solid individual fractions in the exact proportions that they were present in the original material. The original humic acids or their corresponding mixtures were added as the sole carbon source in separate aerobic cultures containing a microbial consortium isolated from a mineral soil. After incubation for 125 days mineralization of the self-assembled samples was shown to be higher by as much as 70% compared to their corresponding physical mixtures. The extent of mineralization of the self-assembled samples was not correlated to the material's chemical composition or hydrophobicity index obtained from their 13C solid-state NMR spectra. In contrast, mineralization of the physical mixtures and the individual fractions did vary with chemical composition and was accompanied by preferential mineralization of alkyl carbon. These results suggest the microbial mineralization of humic acids is related to their self-assembly.

  5. A general evaluation of the frequency distribution of clay and associated minerals in the alluvial soils of ceylon

    USGS Publications Warehouse

    Herath, J.W.; Grimshaw, R.W.

    1971-01-01

    Clay mineral analyses were made of several alluvial clay materials from Ceylon. These studies show that the soil materials can be divided into 3 clay mineral provinces on the basis of the frequency distribution of clay and associated minerals. The provinces closely follow the climatic divisions. The characteristic feature of this classification is the progressive development of gibbsite from Dry to Wet Zone areas. Gibbsite has been used as a reliable indicator mineral. ?? 1971.

  6. Organic nitrogen storage in mineral soil: Implications for policy and management.

    PubMed

    Bingham, Andrew H; Cotrufo, M Francesca

    2016-05-01

    Nitrogen is one of the most important ecosystem nutrients and often its availability limits net primary production as well as stabilization of soil organic matter. The long-term storage of nitrogen-containing organic matter in soils was classically attributed to chemical complexity of plant and microbial residues that retarded microbial degradation. Recent advances have revised this framework, with the understanding that persistent soil organic matter consists largely of chemically labile, microbially processed organic compounds. Chemical bonding to minerals and physical protection in aggregates are more important to long-term (i.e., centuries to millennia) preservation of these organic compounds that contain the bulk of soil nitrogen rather than molecular complexity, with the exception of nitrogen in pyrogenic organic matter. This review examines for the first time the factors and mechanisms at each stage of movement into long-term storage that influence the sequestration of organic nitrogen in the mineral soil of natural temperate ecosystems. Because the factors which govern persistence are different under this newly accepted paradigm we examine the policy and management implications that are altered, such as critical load considerations, nitrogen saturation and mitigation consequences. Finally, it emphasizes how essential it is for this important but underappreciated pool to be better quantified and incorporated into policy and management decisions, especially given the lack of evidence for many soils having a finite capacity to sequester nitrogen. PMID:26874768

  7. Effect of long-term application of biosolids on biological soil quality: C mineralization, and particulate and non-particulate soil organic C

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Assessment of C mineralization and fractions in biosolids-amended soil can increase our knowledge on the impact of biosolids application on soil nutrient availability and C sequestration. Soil samples were collected in 2006 from 20 strip-mined fields at Fulton County, Illinois, which received biosol...

  8. Ex situ bioremediation of mineral oil in soils: Land treatment and composting. Final report

    SciTech Connect

    Gauger, K.

    1998-06-01

    Mineral oil dielectric fluid (MODF) has replaced PCB oil as the insulating medium in electrical transformers. Although eliminating PCBs has reduced the environmental impact resulting from transformer leaks, soil contaminated with mineral oil still often requires remediation. This study evaluated the feasibility of ex situ biotreatment by land farming and composting for Southern Company Services/Georgia Power. Research results indicate that composting does not enhance the biodegradation of mineral oil compared to land treatment. Furthermore, while land treatment does degrade mineral oil, the process takes nearly a year and may not meet regulatory limits. Because the environmental impact of MODF spills into soil is not well understood, states regulate this fluid similarly to petroleum fuel oil for cleanup purposes. This has led to costly remedial efforts, with utilities excavating contaminated media and disposing it in landfills. However, landfills are becoming increasingly regulated, and their use leaves future liability issues unresolved. Southern Company Services/Georgia Power and EPRI sought to explore the effectiveness of ex situ treatment technologies of land farming and composting to decontaminate soil for on-site reuse.

  9. Ectomycorrhizal influence on particle size, surface structure, mineral crystallinity, functional groups, and elemental composition of soil colloids from different soil origins.

    PubMed

    Li, Yanhong; Wang, Huimei; Wang, Wenjie; Yang, Lei; Zu, Yuangang

    2013-01-01

    Limited data are available on the ectomycorrhizae-induced changes in surface structure and composition of soil colloids, the most active portion in soil matrix, although such data may benefit the understanding of mycorrhizal-aided soil improvements. By using ectomycorrhizae (Gomphidius viscidus) and soil colloids from dark brown forest soil (a good loam) and saline-alkali soil (heavily degraded soil), we tried to approach the changes here. For the good loam either from the surface or deep soils, the fungus treatment induced physical absorption of covering materials on colloid surface with nonsignificant increases in soil particle size (P > 0.05). These increased the amount of variable functional groups (O-H stretching and bending, C-H stretching, C=O stretching, etc.) by 3-26% and the crystallinity of variable soil minerals (kaolinite, hydromica, and quartz) by 40-300%. However, the fungus treatment of saline-alkali soil obviously differed from the dark brown forest soil. There were 12-35% decreases in most functional groups, 15-55% decreases in crystallinity of most soil minerals but general increases in their grain size, and significant increases in soil particle size (P < 0.05). These different responses sharply decreased element ratios (C:O, C:N, and C:Si) in soil colloids from saline-alkali soil, moving them close to those of the good loam of dark brown forest soil. PMID:23766704

  10. Ectomycorrhizal Influence on Particle Size, Surface Structure, Mineral Crystallinity, Functional Groups, and Elemental Composition of Soil Colloids from Different Soil Origins

    PubMed Central

    Li, Yanhong; Wang, Huimei; Wang, Wenjie; Yang, Lei; Zu, Yuangang

    2013-01-01

    Limited data are available on the ectomycorrhizae-induced changes in surface structure and composition of soil colloids, the most active portion in soil matrix, although such data may benefit the understanding of mycorrhizal-aided soil improvements. By using ectomycorrhizae (Gomphidius viscidus) and soil colloids from dark brown forest soil (a good loam) and saline-alkali soil (heavily degraded soil), we tried to approach the changes here. For the good loam either from the surface or deep soils, the fungus treatment induced physical absorption of covering materials on colloid surface with nonsignificant increases in soil particle size (P > 0.05). These increased the amount of variable functional groups (OH stretching and bending, CH stretching, C=O stretching, etc.) by 326% and the crystallinity of variable soil minerals (kaolinite, hydromica, and quartz) by 40300%. However, the fungus treatment of saline-alkali soil obviously differed from the dark brown forest soil. There were 1235% decreases in most functional groups, 1555% decreases in crystallinity of most soil minerals but general increases in their grain size, and significant increases in soil particle size (P < 0.05). These different responses sharply decreased element ratios (C?:?O, C?:?N, and C?:?Si) in soil colloids from saline-alkali soil, moving them close to those of the good loam of dark brown forest soil. PMID:23766704

  11. N Isotope Composition of the Soil Microbial Biomass Reflects N Mineralization and C and N Availability

    NASA Astrophysics Data System (ADS)

    Dijkstra, P.; Hungate, B. A.; Schwartz, E.; Hart, S. C.

    2009-04-01

    It has been an open question for several decades whether N mineralization is a fractionating process. This question is important for N cycling in terrestrial ecosystems because even a small fractionation during N mineralization could potentially have a large influence on the N isotope composition of other ecosystem N pools, since N mineralization represents the largest N flux in ecosystems. Fractionation during N mineralization should result in a difference between the N isotope composition of the soil microorganisms and that of its substrates. We analyzed the N isotope composition of the soil microbial biomass in a variety of ecosystems, and found that it was 15N enriched compared to that of other soil N pools, such as soil soluble, organic and inorganic N (Dijkstra et al. 2006a,b). We observed a negative correlation between the 15N enrichment of the microorganisms and the relative C and N availability for soil from ecosystems in Hawaii and Arizona, across a broad range of climates, grasslands and forests, and more than four million years of ecosystem development. This result suggests that during N dissimilation (and associated transaminations) and N export, the lighter 14N isotope is preferentially removed in a manner similar to that proposed for animals and ectomycorrhizae. This was further confirmed by the positive correlation between microbial 15N enrichment and net N mineralization rate (Dijkstra et al. 2008) and by culture experiments with Escherichia coli (Collins et al 2008). Since mineralization is the largest flux of N in ecosystems, fractionation during N mineralization has the potential to influence and even determine the N isotope composition of other N pools, such as inorganic N, plant N and soil organic matter N. We will show that the N isotope composition of these ecosystem N pools exhibit differences that are consistent with fractionation during N mineralization. Collins JG, Dijkstra P, Hart SC, Hungate BA, Flood NM and Schwartz E. 2008. Nitrogen source influences natural abundance 15N of Escherichia coli. FEMS Microbiol Lett 282: 246-250 Dijkstra, P, Ishizu A, Doucett RR, Hart SC, Schwartz E, Menyailo OV and Hungate BA 2006a. 13C and 15N natural abundances of soil microbial biomass. Soil Biol Biochem 38:3257-3266. Dijkstra, P, Menyailo OV, Doucett RR, Hart SC, Schwartz E and Hungate BA 2006b. C and N availability affects the 15N natural abundance of the soil microbial biomass across a cattle manure gradient. Eur J Soil Sci 57:468-475. Dijkstra P, LaViolette CM, Coyle JS, Doucett RR, Schwartz E, Hart SC and Hungate BA 2008. 15N enrichment as an integrator of the effects of C and N on microbial metabolism and ecosystem function. Ecol Lett 11: 389-397.

  12. 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.

  13. Reforestation in southern China: revisiting soil N mineralization and nitrification after 8 years restoration.

    PubMed

    Mo, Qifeng; Li, Zhi'an; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming

    2016-01-01

    Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China. PMID:26794649

  14. Reforestation in southern China: revisiting soil N mineralization and nitrification after 8 years restoration

    PubMed Central

    Mo, Qifeng; Li, Zhi’an; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming

    2016-01-01

    Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China. PMID:26794649

  15. Sorption and Transport of Pharmaceutical chemicals in Organic- and Mineral-rich Soils

    NASA Astrophysics Data System (ADS)

    Vulava, V. M.; Schwindaman, J.; Murphey, V.; Kuzma, S.; Cory, W.

    2011-12-01

    Pharmaceutical, active ingredients in personal care products (PhACs), and their derivative compounds are increasingly ubiquitous in surface waters across the world. Sorption and transport of four relatively common PhACs (naproxen, ibuprofen, cetirizine, and triclosan) in different natural soils was measured. All of these compounds are relatively hydrophobic (log KOW>2) and have acid/base functional groups, including one compound that is zwitterionic (cetirizine.) The main goal of this study was to correlate organic matter (OM) and clay content in natural soils and sediment with sorption and degradation of PhACs and ultimately their potential for transport within the subsurface environment. A- and B-horizon soils were collected from four sub-regions within a pristine managed forested watershed near Charleston, SC, with no apparent sources of anthropogenic contamination. These four soil series had varying OM content (fOC) between 0.4-9%, clay mineral content between 6-20%, and soil pH between 4.5-6. The A-horizon soils had higher fOC and lower clay content than the B-horizon soils. Sorption isotherms measured from batch sorption experimental data indicated a non-linear sorption relationship in all A- and B-horizon soils - stronger sorption was observed at lower PhAC concentrations and lower sorption at higher concentrations. Three PhACs (naproxen, ibuprofen, and triclosan) sorbed more strongly with higher fOC A-horizon soils compared with the B-horizon soils. These results show that soil OM had a significant role in strongly binding these three PhACs, which had the highest KOW values. In contrast, cetirizine, which is predominantly positively charged at pH below 8, strongly sorbed to soils with higher clay mineral content and least strongly to higher fOC soils. All sorption isotherms fitted well to the Freundlich model. For naproxen, ibuprofen, and triclosan, there was a strong and positive linear correlation between the Freundlich adsorption constant, Kf, and fOC, again indicating that these PhACs preferentially partition into the soil OM. Such a correlation was absent for cetirizine. Breakthrough curves of PhACs measured in homogeneous packed soil columns indicated that PhAC transport was affected by chemical nonequilibrium processes depending on the soil and PhAC chemistry. The shape of the breakthrough curves indicated that there were two distinct sorption sites - OM and clay minerals - which influence nonequilibrium transport of these compounds. The retardation factor estimated using the distribution coefficient, Kd, measured from the sorption experiments was very similar to the measured value. While the sorption and transport data do not provide mechanistic information regarding the nature of PhAC interaction with chemical reactive components within geological materials, they do provide important information regarding potential fate of such compounds in the environment. The results also show the role that soil OM and mineral surfaces play in sequestering or transporting these chemicals. These insights have implications to the quality of the water resources in our communities.

  16. Soil Phosphorus Stoichiometry Drives Carbon Turnover Along a Soil C Gradient Spanning Mineral and Organic Soils Under Rice Cultivation

    NASA Astrophysics Data System (ADS)

    Hartman, W.; Ye, R.; Horwath, W. R.; Tringe, S. G.

    2014-12-01

    Soil carbon (C) cycling is linked to the availability of nutrients like nitrogen (N) and phosphorus (P). However, the role of soil P in influencing soil C turnover and accumulation is poorly understood, with most models focusing on C:N ratios based on the assumption that terrestrial ecosystems are N limited. To determine the effects of N and P availability on soil C turnover, we compared soil respiration over the course of a growing season in four adjacent rice fields with 5%, 10%, 20% and 25% soil C. In each of these fields, plots were established to test the effect of N additions on plant growth, using control and N addition treatments (80 kg N/ha urea). Although soil P was not manipulated in parallel, prior work has shown soil P concentrations decline markedly with increasing soil C content. Soil CO2 flux was monitored using static chambers at biweekly intervals during the growing season, along with porewater dissolved organic C and ammonium. Soils were collected at the end of the growing season, and tested for total C, N, and P, extractable N and P, pH, base cations and trace metals. Soil DNA was also extracted for 16S rRNA sequencing to profile microbial communities. Soil N additions significantly increased CO2 flux and soil C turnover (seasonal CO2 flux per unit soil C) in 5% and 10% C fields, but not in 20% or 25% C fields. Soil C content was closely related to soil N:P stoichiometry, with N:P ratios of ca. 12, 16, 24, and 56 respectively in the 5, 10, 20 and 25% C fields. Seasonal CO2 fluxes (per m2) were highest in 10% C soils. However, soil C turnover was inversely related to soil C concentrations, with the greatest C turnover at the lowest values of soil C. Soil C turnover showed stronger relationships with soil chemical parameters than seasonal CO2 fluxes alone, and the best predictors of soil C turnover were soil total and extractable N:P ratios, along with extractable P alone. Our results show that soil P availability and stoichiometry influence the turnover of soil C, even where primary producers are clearly limited by N. Prior work has suggested these contrasting patterns in nutrient limitation may arise due to stoichiometric differences among plants and soil microbes. We hypothesize that differences in soil carbon turnover may in part reflect shifts in metabolism of microbial communities associated with stoichiometric variation in soils.

  17. Fire effects on peat and organo-mineral soils of Meshchera plain

    NASA Astrophysics Data System (ADS)

    Tsibart, Anna; Koshovskii, Timur; Gamova, Natalia; Kovach, Roman

    2015-04-01

    The fire effects the soil properties depend on soil type and on their vulnerability to fires. The most of available data is devoted to changes in organo-mineral soils. But the peat fires can cause deeper changes in soil profiles, especially in case of drained peat soils. Now the lack of information exists in the sphere of the comparison of these fire types on soil cover. Meshchera plain (Moscow and Ryazan Regions, Russia) has different soil types. Moreover peatlands were partly drained, and the plain was affected by numerous fires of different time. So there is a need of detailed post-fire soil investigations in this region. During current research the soils Meshchera plain subjected by wildfires of 2002, 2007, 2010 and 2012 were studied. A total of 32 profiles including background and post-fire histosols, histic and sod podzols were investigated. Moreover the detailed description of vegetation cover was conducted. The samples were taken from genetic horizons. The morfological properties of soil profiles were sudied and the samples were analysed on organic carbon, pH, macroelements, magnetic susceptibility. After the wildfires changes in morfological and physico-chemical properties of soils were detected in most cases. The formation of ash and charry horizons was observed only in cases of peat soils affecetd by intense fires, and all post-fire drained peat soils had thick ash horizons even after 10 years after the fires. The significant loss of organic matter took place after burning. But almost immediately after the fires new stage of humus formation usually started. For instance, in post-fire histosols in 2 years after the burning the content of organic carbon reached to 10-12 % in upper horizons. ph values in background histosols were approximately 4-5. After the fire pH increased in these soil type to 8, and two years after the fire event pH decreased to 6-7. In podzols pH values returned to the pre-fire level 4-5 in two years. The magnetic susceptibility of soil samples in background histosols was 2-40 10-6 cm3/g. After the fires it increased in ash horizons up to 250 10-6 cm3/g. In sod podzols the changes also occurred. Background podzols had 2- 510-6 cm3/g. Post-fire horizons had up to 50- 6010-6 cm3/g after the fires. And even 10 years later the differences between post-fire and background soils preserved. So this parameter could be used as an indicator of fire events in soil profiles. After the fire the significant changes occurred in horizon mineral composition. Ash horizons had elevated concentrations of Al2O3 (9-17%), Fe2O3 (4-11%), P2O3 (1-1,8 %), CaO (1,9-2,8 %) and K2O (0,1-1,9%). The observed trends were similar for histosols and for histic podzols. And the changes in horizon mineral composition remained 2 and 10 years after the fire. So the more significant morphological and chemical changes occurred in the profiles of histosols, especially fire altered the soils of drained peatlands. These soil type keeps changes even 10 years after the fires.

  18. Distribution and speciation of ambient selenium in contrasted soils, from mineral to organic rich.

    PubMed

    Tolu, Julie; Thiry, Yves; Bueno, Mat; Jolivet, Claudy; Potin-Gautier, Martine; Le Hcho, Isabelle

    2014-05-01

    Selenium adsorption onto oxy-hydroxides mainly controls its mobility in volcanic soils, red earths and soils poor in organic matter (OM) while the influence of OM was emphasized in podzol and peat soils. This work aims at deciphering how those solid phases influence ambient Se mobility and speciation under less contrasted conditions in 26 soils spanning extensive ranges of OM (1-32%), Fe/Al oxy-hydroxides (0.3-6.1%) contents and pH (4.0-8.3). The soil collection included agriculture, meadow and forest soils to assess the influence of OM quality as well. Trace concentrations of six ambient Se species (Se(IV), Se(VI) and 4 organo-Se compounds) were analyzed by HPLC-ICP-MS in three extractants (ultrapure water, phosphate and sodium hydroxide) targeting Se associated to different soil phases. The Kd values determined from ultrapure water extraction were higher than those reported in commonly used short-term experiments after Se-spiking. Correlations of ambient Se content and distribution with soil parameters explained this difference by an involvement of slow processes in Se retention in soils. The 26 Kd values determined here for a wide variety of soils thus represent a relevant database for long-term prediction of Se mobility. For soils containing less than 20% OM, ambient Se solubility is primarily controlled by its adsorption onto crystalline oxy-hydroxides. However, OM plays an important role in Se mobility by forming organo-mineral associations that may protect adsorbed Se from leaching and/or create anoxic zones (aggregates) where Se is immobilized after its reduction. Although for the first time, inorganic Se(IV), Se(VI) and organo-Se compounds were simultaneously investigated in a large soil collection, high Se proportions remain unidentified in each soil extract, most probably due to Se incorporation and/or binding to colloidal-sized OM. Variations of environmental factors regulating the extent of OM-mineral associations/aggregation may thus lead to changes in Se mobility and bio-availability. PMID:24548882

  19. Temperature effect on mineralization of SOM, plant litter and priming: modified by soil type?

    NASA Astrophysics Data System (ADS)

    Azzaroli Bleken, Marina; Berland Frøseth, Randi

    2015-04-01

    The purpose of this study was to provide improved temperature response functions to be used in models of soil organic carbon (SOC) and litter mineralization, with focus on the winter period. Our working hypothesis were: 1) decomposition of SOM and plant residue occurs also at temperature close to the freezing point; 2) the effect of temperature on SOC decomposition is stronger in clayey than in sandy soil; 3) decomposition and response to temperature of added plant litter is not affected by soil type. A silty clay loam (27% clay, 3% sand) and a sandy loam (6% clay, 51% sand) with similar weather and cultivation history were pre-incubated at about 15° C for about 4.5 months. Clover leaves labelled with 13C were added to half of the samples, and soil with and without clover was incubated for 142 days at 0, 4, 8.5 or 15 °C. Mineralization of SOC and clover leaves was observed also at 0° C. In the absence of added plant material, SOC decomposition followed a first order reaction which was twice as fast in the sandy soil as in the clay soil. The decomposition rate of clover leaves was also higher in the sandy soil than in the clay soil. However, the influence of temperature on SOC and on clover decomposition was the same in both soils. In presence of plant material, there was a positive priming effect on SOC, which initially correlated with decomposition of plant litter. There was a progressively lower priming effect at higher temperatures, particularly in the sandy soil, that could be understood as substrates exhaustion in a restricted volume of influence around the added clover leaves. We provide parameterised Arrhenius and alternative modifying linear temperature functions together with decay rates at reference temperature, which can be used for predicting decay rates of SOC per se and of the labile pool of clover leaves. We also show the superiority of these functions compared to the use of Q10 as temperature factor. Further, we suggest approaches for modelling the priming effect caused by plant litter. Reference: Frøseth RB, Bleken MA(2015) Effect of low temperature and soil type on the decomposition rate of soil organic carbon and clover leaves, and related priming effect. Soil Biology and Biochemistry 80:156-166.

  20. A new generator for mineral dust aerosol production from soil samples in the laboratory: GAMEL

    NASA Astrophysics Data System (ADS)

    Lafon, Sandra; Alfaro, Stphane C.; Chevaillier, Servanne; Rajot, Jean Louis

    2014-12-01

    A generator has been developed for producing mineral dust from small samples of desert soils. The objective is to perform a thorough characterization of this new tool and show that it is adapted to the future laboratory studies of the relationship between aerosols and their parent soils. This work describes the principles and operating protocol of the so-called GAMEL generator. A first series of detailed measurements was performed with a Niger soil. During these tests the aerosol size-distribution was monitored in real time with an optical counter and the particles collected on filters submitted to XRF analysis. This allowed characterizing the emission in terms of time evolution of the aerosol production, repeatability of the experiment, and assessing the influence of such generation parameters as the mass of soil and the frequency and duration of the shaking. For this sandy Niger soil, the optimal generation parameters were found to be 1 g of soil agitated 9 min at the frequency of 500 cycles/min, but the effect of modifications of these recommended values have also been quantified. In terms of size-distribution as well as of elemental composition, the generated aerosol is found to compare well to the one collected in natural conditions during local events. For testing the capability of the GAMEL to produce aerosols from different soils, tests were also performed with 3 other soils from arid and semi-arid areas. Results showed that the GAMEL is able to produce aerosols whose characteristics encompass the regional variability of naturally produced mineral aerosols.

  1. Topsoil organic carbon mineralization and CO2 evolution of three paddy soils from South China and the temperature dependence.

    PubMed

    Zhang, Xu-Hui; Li, Lian-Qing; Pan, Gen-Xing

    2007-01-01

    Carbon mineralization and its response to climatic warming have been receiving global attention for the last decade. Although the virtual influence of temperature effect is still in great debate, little is known on the mineralization of organic carbon (SOC) of paddy soils of China under warming. SOC mineralization of three major types of China's paddy soils is studied through laboratory incubation for 114 d under soil moisture regime of 70% water holding capacity at 20 degrees C and 25 degrees C respectively. The carbon that mineralized as CO2 evolved was measured every day in the first 32 d and every two days in the following days. Carbon mineralized during the 114 d incubation ranged from 3.51 to 9.22 mg CO2-C/gC at 20 degrees C and from 4.24 to 11.35 mg CO2-C/gC at 25 degrees C respectively; and a mineralizable C pool in the range of 0.24 to 0.59 gC/kg, varying with different soils. The whole course of C mineralization in the 114 d incubation could be divided into three stages of varying rates, representing the three subpools of the total mineralizable C: very actively mineralized C at 1-23 d, actively mineralized C at 24-74 d and a slowly mineralized pool with low and more or less stabilized C mineralization rate at 75-114 d. The calculated Q10 values ranged from 1.0 to 2.4, varying with the soil types and N status. Neither the total SOC pool nor the labile C pool could account for the total mineralization potential of the soils studied, despite a well correlation of labile C with the shortly and actively mineralized C, which were shown in sensitive response to soil warming. However, the portion of microbial C pool and the soil C/N ratio controlled the C mineralization and the temperature dependence. Therefore, C sequestration may not result in an increase of C mineralization proportionally. The relative control of C bioavailability and microbial metabolic activity on C mineralization with respect to stabilization of sequestered C in the paddy soils of China is to be further studied. PMID:17918594

  2. Mineral nutrition of campos rupestres plant species on contrasting nutrient-impoverished soil types.

    PubMed

    Oliveira, Rafael S; Galvo, Hugo C; de Campos, Mariana C R; Eller, Cleiton B; Pearse, Stuart J; Lambers, Hans

    2015-02-01

    In Brazil, the campos rupestres occur over the Brazilian shield, and are characterized by acidic nutrient-impoverished soils, which are particularly low in phosphorus (P). Despite recognition of the campos rupestres as a global biodiversity hotspot, little is known about the diversity of P-acquisition strategies and other aspects of plant mineral nutrition in this region. To explore nutrient-acquisition strategies and assess aspects of plant P nutrition, we measured leaf P and nitrogen (N) concentrations, characterized root morphology and determined the percentage arbuscular mycorrhizal (AM) colonization of 50 dominant species in six communities, representing a gradient of soil P availability. Leaf manganese (Mn) concentration was measured as a proxy for carboxylate-releasing strategies. Communities on the most P-impoverished soils had the highest proportion of nonmycorrhizal (NM) species, the lowest percentage of mycorrhizal colonization, and the greatest diversity of root specializations. The large spectrum of leaf P concentration and variation in root morphologies show high functional diversity for nutritional strategies. Higher leaf Mn concentrations were observed in NM compared with AM species, indicating that carboxylate-releasing P-mobilizing strategies are likely to be present in NM species. The soils of the campos rupestres are similar to the most P-impoverished soils in the world. The prevalence of NM strategies indicates a strong global functional convergence in plant mineral nutrition strategies among severely P-impoverished ecosystems. PMID:25425486

  3. Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil

    NASA Astrophysics Data System (ADS)

    Lind, S. E.; Shurpali, N. J.; Peltola, O.; Mammarella, I.; Hyvönen, N.; Maljanen, M.; Räty, M.; Virkajärvi, P.; Martikainen, P. J.

    2015-10-01

    One of the strategies to reduce carbon dioxide (CO2) emissions from the energy sector is to increase the use of renewable energy sources such as bioenergy crops. Bioenergy is not necessarily carbon neutral because of greenhouse gas (GHG) emissions during biomass production, field management and transportation. The present study focuses on the cultivation of reed canary grass (RCG, Phalaris arundinaceae L.), a perennial bioenergy crop, on a mineral soil. To quantify the CO2 exchange of this RCG cultivation system, and to understand the key factors controlling its CO2 exchange, the net ecosystem CO2 exchange (NEE) was measured during three years using the eddy covariance (EC) method. The RCG cultivation thrived well producing yields of 6200 and 6700 kg DW ha-1 in 2010 and 2011, respectively. Gross photosynthesis (GPP) was controlled mainly by radiation from June to September. Vapour pressure deficit (VPD), air temperature or soil moisture did not limit photosynthesis during the growing season. Total ecosystem respiration (TER) increased with soil temperature, green area index and GPP. Annual NEE was -262 and -256 g C m-2 in 2010 and 2011, respectively. Throughout the studied period, cumulative NEE was -575 g C m-2. When compared to the published data for RCG on an organic soil, the cultivation of this crop on a mineral soil had higher capacity to take up CO2 from the atmosphere.

  4. Pathogenic prion protein is degraded by a manganese oxide mineral found in soils

    USGS Publications Warehouse

    Russo, F.; Johnson, C.J.; McKenzie, D.; Aiken, Judd M.; Pedersen, J.A.

    2009-01-01

    Prions, the aetiological agents of transmissible spongiform encephalopathies, exhibit extreme resistance to degradation. Soil can retain prion infectivity in the environment for years. Reactive soil components may, however, contribute to the inactivation of prions in soil. Members of the birnessite family of manganese oxides (MnO2) rank among the strongest natural oxidants in soils. Here, we report the abiotic degradation of pathogenic prion protein (PrPTSE) by a synthetic analogue of naturally occurring birnessite minerals. Aqueous MnO2 suspensions degraded the PrPTSE as evidenced by decreased immunoreactivity and diminished ability to seed protein misfolding cyclic amplification reactions. Birnessite-mediated PrPTSE degradation increased as a solution's pH decreased, consistent with the pH-dependence of the redox potential of MnO2. Exposure to 5.6 mg MnO2 ml-1 (PrPTSE:MnO2=1 : 110) decreased PrPTSE levels by ???4 orders of magnitude. Manganese oxides may contribute to prion degradation in soil environments rich in these minerals. ?? 2009 SGM.

  5. Organic nitrogen storage in mineral soil: implications for policy and management

    NASA Astrophysics Data System (ADS)

    Bingham, A. H.; Cotrufo, M. F.

    2015-06-01

    Nitrogen is one of the most important ecosystem nutrients and often its availability limits net primary production as well as stabilization of soil organic matter. The long-term storage of nitrogen-containing organic matter in soils was classically attributed to chemical complexity of plant and microbial residues that retarded microbial degradation. Recent advances have revised this framework, with the understanding that persistent soil organic matter consists largely of chemically labile, microbially processed organic compounds. Chemical bonding to minerals and physical protection in aggregates are more important to long-term (i.e., centuries to millennia) preservation of these organic compounds that contain the bulk of soil nitrogen rather than molecular complexity, with the exception of nitrogen in pyrogenic organic matter. This review examines the factors and mechanisms that influence the long-term sequestration of organic nitrogen in mineral soils. It examines the policy and management implications which stem from this newly accepted paradigm, such as critical loads considerations and nitrogen saturation and mitigation consequences. Finally, it emphasizes how essential it is for this important but underappreciated pool to be better quantified and incorporated into policy and management decisions.

  6. Minerals

    MedlinePLUS

    ... some of the minerals you get from food. Calcium Calcium is the top macromineral when it comes to ... on tasty food. Which foods are rich in calcium? dairy products, such as milk, cheese, and yogurt ...

  7. Mineral control of soil carbon storage with reforestation of abandoned pastures

    NASA Astrophysics Data System (ADS)

    Marín-Spiotta, E.; Silver, W. L.; Swanston, C. W.; Torn, M. S.; Burton, S. D.

    2006-12-01

    We applied CP MAS 13C-NMR spectroscopy and radiocarbon modeling to soil C density fractions to track changes in the quality and turnover of C with forest regrowth on former pasturelands. Our results showed that inter-aggregate, unattached particulate organic C (free light fraction) and C located inside soil aggregates (occluded light fraction) represent distinct soil C pools. The signal intensity of the O-alkyl region, representing cellulose, decreased with mineral-association, while alkyl C, attributed to waxy compounds and microbially resynthesized lipids, increased from the free to the occluded light fractions. The alkyl/O-alkyl ratio changed consistently with changes in C-to-N and δ15N across different land cover types, and thus appears to be a reliable index of humification. In contrast to cellulose, proteins, lipids and lignin did not show any consistent trends, suggesting different controls on their decomposition. Greater variability in the chemical makeup of the occluded light fraction suggests that it represents material in different stages of decay. Mean residence times (MRT) of the free light C were significantly shorter (4.3 ± 0.5 yrs) than for the occluded fraction (7.3 ± 0.8 yrs). The occluded fraction in active pastures and secondary forests in the earliest stage of succession had shorter MRT than in primary forests and older secondary forests, which would be explained by lower aggregate stability and faster cycling rates in disturbed versus undisturbed soils. The mineral associated C in the disturbed soils had slower cycling C (MRT = 98.9 ± 10.6 yrs) than the undisturbed sites (65.8 ± 2.1 yrs), most likely due to a preferential loss of labile C in the first. Incorporation of C into soil aggregates afforded some protection from decomposition, but the main mechanism of stabilization was direct mineral association. As the sorptive capacity of a soil is dependent on its mineral composition, it appears that the Oxisols at our sites have reached their maximum C storage capacity. This may explain their resiliency to land-use change and why we have observed no significant accumulation of soil C despite large increases in aboveground biomass with reforestation.

  8. Assessing the Influence of Mineral Surface Chemistry on Soil Organic Matter Stability in the US in Response to Climate Change

    NASA Astrophysics Data System (ADS)

    Toledo, A.; Heckman, K.; Rasmussen, C.; Harden, J. W.; Johnson, M.; Swanston, C.

    2014-12-01

    Soils represent a significant pool for carbon storage and sequestration. Previous field experiments have indicated that some mineral compositions are more effective in preserving soil organic matter (SOM) from microbial degradation. Due to climate change, it is important to quantify which soil types are changing in mineral surface chemistry. One way to do that is by differentiating the SOM stabilization mechanisms in different soil types at various depths. This study focused on examining the distribution of soil mass and composition by the soils density and mineral classification and the soils stability by measuring the amount of carbon and radiocarbon abundance. The United States Geological Survey collected the soils in Oregon, Mississippi, Alaska, and Arizona. The four different soil types were separated by density using density fractionation. Radiocarbon analysis of the different soils varying in density was conducted at Lawrence Livermore National Lab-Center for Accelerator Mass Spectrometry to determine the 13C/14C ratios. The ratios were used to determine the average age of the carbon in the samples. To determine the composition of the soil types, the soils were processed at Lawrence Berkeley National Lab using Fourier Transform Infrared-Attenuated Total Reflection. Results confirmed the amount of carbon, radiocarbon abundance and composition varied among the sites, thus SOM responds differently to climate change depending on the soil type.

  9. Geochemical soil sampling for deeply-buried mineralized breccia pipes, northwestern Arizona

    USGS Publications Warehouse

    Wenrich, K.J.; Aumente-Modreski, R. M.

    1994-01-01

    Thousands of solution-collapse breccia pipes crop out in the canyons and on the plateaus of northwestern Arizona; some host high-grade uranium deposits. The mineralized pipes are enriched in Ag, As, Ba, Co, Cu, Mo, Ni, Pb, Sb, Se, V and Zn. These breccia pipes formed as sedimentary strata collapsed into solution caverns within the underlying Mississippian Redwall Limestone. A typical pipe is approximately 100 m (300 ft) in diameter and extends upward from the Redwall Limestone as much as 1000 m (3000 ft). Unmineralized gypsum and limestone collapses rooted in the Lower Permian Kaibab Limestone or Toroweap Formation also occur throughout this area. Hence, development of geochemical tools that can distinguish these unmineralized collapse structures, as well as unmineralized breccia pipes, from mineralized breccia pipes could significantly reduce drilling costs for these orebodies commonly buried 300-360 m (1000-1200 ft) below the plateau surface. Design and interpretation of soil sampling surveys over breccia pipes are plagued with several complications. (1) The plateau-capping Kaibab Limestone and Moenkopi Formation are made up of diverse lithologies. Thus, because different breccia pipes are capped by different lithologies, each pipe needs to be treated as a separate geochemical survey with its own background samples. (2) Ascertaining true background is difficult because of uncertainties in locations of poorly-exposed collapse cones and ring fracture zones that surround the pipes. Soil geochemical surveys were completed on 50 collapse structures, three of which are known mineralized breccia pipes. Each collapse structure was treated as an independent geochemical survey. Geochemical data from each collapse feature were plotted on single-element geochemical maps and processed by multivariate factor analysis. To contrast the results between geochemical surveys (collapse structures), a means of quantifying the anomalousness of elements at each site was developed. This degree of anomalousness, named the "correlation value", was used to rank collapse features by their potential to overlie a deeply-buried mineralized breccia pipe. Soil geochemical results from the three mineralized breccia pipes (the only three of the 50 that had previously been drilled) show that: (1) Soils above the SBF pipe contain significant enrichment of Ag, Al, As, Ba, Ga, K, La, Mo, Nd, Ni, Pb, Sc, Th, U and Zn, and depletion in Ca, Mg and Sr, in contrast to soils outside the topographic and structural rim; (2) Soils over the inner treeless zone of the Canyon pipe show Mo and Pb enrichment anf As and Ga depletion, in contrast to soils from the surrounding forest; and (3) The soil survey of the Mohawk Canyon pipe was a failure because of the rocky terrane and lack of a B soil horizon, or because the pipe plunges. At least 11 of the 47 other collapse structures studied contain anomalous soil enrichments similar to the SBF uranium ore-bearing pipe, and thus have good potential as exploration targets for uranium. One of these 11, #1102, does contain surface mineralized rock. These surveys suggest that soil geochemical sampling is a useful tool for the recognition of many collapse structures with underlying ore-bearing breccia pipes. ?? 1994.

  10. Rebuilding Peatlands on Mineral Soils Utilizing Lessons Learned from Past Peatland Initiation

    NASA Astrophysics Data System (ADS)

    Vitt, D. H.; Koropchak, S. C.; Xu, B.; Bloise, R.; Wieder, R.; Mowbray, S.

    2010-12-01

    Recent surveys of peatland initiation during the past 10,000 years in northeastern Alberta have revealed that nearly all peatlands, regardless of whether they are currently bogs and fens, were initiated by paludification, or swamping of upland soils. Terrestrialization (or infilling of water bodies) rarely if ever was involved in the initiation of peatlands across the mid boreal of Canada. Although the importance of paludification as a significant natural process in the initiation of peatland ecosystems has long been known by peatland ecologists, this knowledge has not been transferred to peatland and wetland restoration methodologies. We initiated this study to determine if wetland structure and function could be re-established on mineral gas/oil pads that were originally placed on organic soils. We have attempted to emulate the paludification process by removing mineral material to near the surrounding peatland natural water level and introducing a suite of wetland plants to the rewetted mineral soils. The experimental design comprised two well sites at the Shell Carmon Creek in situ plant near Peace River, Alberta. We placed 292 2 x 2 m plots over a series of fertilizer, water level, cultivation, and amendment treatments. In this presentation, we address four questions: 1) Will locally available peatland vascular plant species establish on these wet, compacted, mineral soils? If so; 2) Are species responses affected by water level, amendment, cultivation, and fertilization treatments, 3) Are invasive weeds a concern in these re-establishment trials, and 4) Will the surrounding bog water chemistry have an effect on water in contact with the mineral soils? Results after three growing season are: 1) All three species originally planted (a sedge, a willow, and tamarack) have successfully established at both well sites; 2) Carex aquatilis has performed well and responses to differing water levels and cultivation are not significant; 3) The plant responses to amendments are, in general, not different from the control plots; 4) The abundance of weeds is significantly different among some of the amendment types; and 5) Water chemistry (pH and electrical conductivity) of the ditches is affected by the surrounding bog waters. In addition, a fifth question was asked: Can Carex aquatilis establish by seed and if so, do C. aquatilis seeds require a peat amendment? In May 2009, three blank 4 m2 plots were selected on each of the experimental well site reclamations. Half of each plot was covered with approximately 4 cm of peat and the other half remained a mineral soil substrate. Each plot half was divided into 2 halves (1 m2); one that had approximately 600 Carex aquatilis seeds scattered across it and one that had no seeds added. Results from reassessment in July 2010 showed that subplots with added seeds had more seedlings than the subplots without added seeds. There was no difference between the number of seedlings between the peat and mineral soil subplots on either site, but on one of the sites, the subplots with peat had much higher percent cover of weeds than the mineral soil subplots.

  11. 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. PMID:24798347

  12. Reactivity of Primary Soil Minerals and Secondary Precipitates beneath Leaking Hanford Waste Tanks

    SciTech Connect

    Nagy, Kathryn L.; Serne, R. Jeff; Yabusaki

    2001-06-01

    Since the late 1950s, leaks from 67 single-shell tanks at the Hanford Site have released about 1 million curies to the underlying sediments. At issue is the distribution of contaminants beneath the tanks, and the processes that led to their current disposition and will control their future mobility. The high ionic strength, high pH, and high aluminum concentrations in the tank liquids can significantly alter the vadose zone sediments through dissolution of primary minerals and precipitation of secondary minerals. Dissolution and precipitation directly influence (1) the flow paths that control contaminant transport and (2) the reactivity of the solid matrix that controls contaminant mobility. The impact of these processes, however, depends on mineral reaction kinetics and the dynamic interaction of the reactions with the flow field and contaminant sorption, neither of which are well-known for this extreme chemical system. Data obtained will be directly useful to other EMSP projects addressing contaminant mobility in the vadose zone. We are addressing three specific issues: (1) Recognized factors that control the kinetics of dissolution and precipitation must be quantified for the unnatural system of tank solutions mixing with soils, including effects of high pH, high ionic strength (especially NaNO3 solutions), temperature, and saturation state. (2) A clear understanding of the roles of nucleation mechanism, nucleation sites on soils minerals, and the role of reactive surface area in simultaneous dissolution and precipitation reactions are the key unknown components in comprehending this contaminated soil system. (3) Results obtained will help build a mechanistic understanding of how tank fluids migrate through the vadose zone. Local changes in porosity and permeability will dictate preferential flow paths which directly regulate the transport of later arriving chemical species. Changes in mineral surface area affect sorption site distribution. A comprehensive model is needed that integrates these feedback mechanisms with all the critically available data.

  13. Soil Fauna Alter the Effects of Litter Composition on Nitrogen Cycling in a Mineral Soil

    EPA Science Inventory

    Plant chemical composition and the soil community are known to influence litter and soil organic matter decomposition. Although these two factors are likely to interact, their mechanisms and outcomes of interaction are not well understood. Studies of their interactive effects are...

  14. Effect of Mineral Reactions on the Hydraulic Properties of Unsaturated Soils: Model Development and Application

    NASA Astrophysics Data System (ADS)

    Wissmeier, L. C.; Barry, D. A.

    2008-12-01

    Precipitation/dissolution induces changes in the pore radii of water-filled pores, and, consequently, affects flow in porous media. The selective radius shift model was developed to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties of unsaturated soils. The model considers the dependency of the amount of mineral precipitation/dissolution within a pore on the local pore volume. Furthermore, it accounts for precipitation/dissolution taking place only in the water-filled part of the pore space. The pore bundle concept was used to relate the pore-scale process of dissolution/precipitation to changes in macroscopic soil hydraulic properties. In the numerical model, the finite change in mineral volume at a discrete time step leads to a discontinuous pore-size distribution, because only the water-filled pores are affected. This pore-size distribution is converted back to a discontinuous soil moisture characteristic to which, at every time step, a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with the selective radius shift model a head-based solution of Richards' equation for aqueous phase flow was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC's comprehensive geochemical reactions. The model was applied to kinetic halite dissolution and calcite precipitation as a consequence of cation exchange in a variety of unsaturated flow situations. The applications showed marked changes in the soil's hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on the water content. Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even increase during precipitation due to changes in the pore-size distribution.

  15. The extent of carbon mineralization in boreal soils controls compositional changes

    NASA Astrophysics Data System (ADS)

    Mercier Quideau, S.; Oh, S.; Par, D.

    2013-12-01

    Almost twenty percent of global carbon stocks in vegetation and soil are found in boreal soils, making them the largest terrestrial carbon storehouse in the world. Yet, despite their importance in the global carbon budget, very little is known about the exact nature and decomposition pathways of organic matter in these soils. The overall objective of this study was to examine the effects of vegetation and disturbance (fire and harvest) on: 1) soil organic matter composition, and 2) decomposition-induced changes in composition from a range of representative boreal forest and peatland ecosystems. Forest floor and peat samples (0-10 cm) were obtained from 17 sites along an east-west transect from New Brunswick to British Columbia, Canada. Carbon mineralization rates were measured during a 1-year laboratory incubation at 10 C. Carbon chemistry in pre- and post-incubation samples was characterized by solid-state ramped-cross-polarization (RAMP-CP) 13C nuclear magnetic resonance (NMR). The percentage of carbon mineralized during incubation ranged from 1 to 24%, and corresponded to significant increases in aromatic, phenolic, and carbonyl carbons. As expected, significant differences in carbon composition pre-incubation were found among vegetation types regardless of disturbance and sampling location. May be more interestingly, comparable differences among samples persisted post-incubation. In addition, decomposition-induced changes in carbon chemistry significantly differed among vegetation types. Samples from Jack pine and Douglas fir stands, which experienced the highest carbon mineralization, also showed the greatest increase in aromatic, phenolic, and carbonyl carbons. Overall, changes in carbon chemistry were significantly correlated to the percentage of carbon mineralized; i.e., the extent of decomposition that the samples underwent.

  16. 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. PMID:24837340

  17. 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.; Rtting, 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 ?g 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 ?g N g-1 day-1). Gross FAA mineralization (3.4 0.2 ?g 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.

  18. 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.; Rtting, 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 ?g 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 ?g N g-1 day-1). Gross fAA mineralization (3.4 0.2 ?g 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.

  19. Identification of a green rust mineral in a reductomorphic soil by Mossbauer and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Trolard, F.; Gnin, J.-M. R.; Abdelmoula, M.; Bourri, G.; Humbert, B.; Herbillon, A.

    1997-03-01

    Mssbauer and Raman spectroscopies are used to identify for the first time a green rust as a mineral in a reductomorphic soil from samples extracted in the forest of Fougres (Brittany-France). The Mossbauer spectrum displays two characteristic ferrous and ferric quadrupole doublets, the abundance ratio Fe(II)/Fe(Ill) of which is close to 1. Comparison with synthetic mixed valence Fe(II)Fe(HI) hydroxides supports the conclusion that the most probable formula is Fe2(OH)5, i.e., according to the pyroaurite-like crystal structure [Fe(n1Fe1III)(OH),]+o [OH] -. The microprobe Raman spectrum exhibits two bands at 518 and 427 cm-' as for synthetic green rusts. When exposed to the air, the new mineral goes rapidly from bluish-green to ochrous. The formula is compatible with the values of ionic activity products Q for equilibria between aqueous iron species and minerals obtained from soil waters, which suggests that this new mineral is likely to control the mobility of Fe in the environment.

  20. An improved radiative transfer model for estimating mineral abundance of immature and mature lunar soils

    NASA Astrophysics Data System (ADS)

    Liu, Dawei; Li, Lin; Sun, Ying

    2015-06-01

    An improved Hapke's radiative transfer model (RTM) is presented to estimate mineral abundance for both immature and mature lunar soils from the Lunar Soil Characterization Consortium (LSCC) dataset. Fundamental to this improved Hapke's model is the application of an alternative equation to describe the effects of larger size submicroscopic metallic iron (SMFe) (>50 nm) in the interior of agglutinitic glass that mainly darken the host material, contrasting to the darkening and reddening effects of smaller size SMFe (<50 nm) residing in the rims of mineral grains. Results from applying a nonlinear inversion procedure to the improved Hapke's RTM show that the average mass fraction of smaller and larger size SMFe in lunar soils was estimated to be 0.30% and 0.31% respectively, and the particle size distribution of soil samples is all within their measured range. Based on the derived mass fraction of SMFe and particle size of the soil samples, abundances of end-member components composing lunar soil samples were derived via minimizing the difference between measured and calculated spectra. The root mean square error (RMSE) between the fitted and measured spectra is lower than 0.01 for highland samples and 0.005 for mare samples. This improved Hapke's model accurately estimates abundances of agglutinitic glass (R-squared = 0.88), pyroxene (R-squared = 0.69) and plagioclase (R-squared = 0.95) for all 57 samples used in this study including both immature and mature lunar soils. However, the improved Hapke's RTM shows poor performance for quantifying abundances of olivine, ilmenite and volcanic glass. Improving the model performance for estimation of these three end-member components is the central focus for our future work.

  1. [Impacts of Biochar Input on Mineralization of Native Soil Organic Carbon].

    PubMed

    Chen, Wei; Hu, Xue-yu; Lu, Hai-nan

    2015-06-01

    Since the biochar was applied in soil, its function in carbon sink had become a research hotspot recently. However, the present studies showed that its function in carbon sink remained controversial and the interaction between biochar and soil organic carbon remained to be investigated. So our study used paddy soil (C3 soil) as the experimental soil, and added washed (CS) or unwashed (CN) corn stalk (C4 crop). Biochar was mixed with soil uniformity by two kinds of weight, each treatment was 1% and 3% of the soil (CS1%, CS3% and CN1%, CN3%). Soil without biochar was used as the control treatment (CK), every treatments repeated three times. Then indoor culturing experiments was carried out to study the effect of biochar on the mineralization of organic carbon. The results showed as follows: (1) During the 180 days' experiment, the accumulated amount of released CO2 in CS1%, CS3% and CN1% groups were 1865.7, 1864.4 and 1856.2 mL x kg(-1) respectively, all were higher than the CK (1779.0 mL x kg(-1)). But the differences were not significant. However, the accumulated amount of released CO2 in the CN3% group was the highest (2289.1 mL x kg(-1)), which was significantly higher than those of all other groups. This showed that high addition of CS biochar significantly reduced the soil CO2 release. (2) The accumulated amount of released CO2 of native soil from the CK treatment, CS treatment and CN treatment were 1534.2, 1000.4 and 1153.7 mL x kg(-1) respectively, among which the CK group is significantly higher than the others. It showed that additions of two kinds of biochar both could inhibit the mineralization of organic carbon in the soil. The result of priming effect also proved that: the PE value of CS 3% group was -34.8%, and the PE value of CN 3% group was -24.8%. This showed that the negative priming effect significantly induced by washed (CS) biochar. PMID:26387339

  2. Minerals vs. Microbes: Biogeochemical Controls on Carbon Storage in Humid Tropical Forest Soils

    NASA Astrophysics Data System (ADS)

    Hall, S. J.; Silver, W. L.

    2012-12-01

    Humid tropical forest soils contain a substantial portion (~500 Pg) of the terrestrial carbon (C) pool, yet their response to climate change remains unclear due to mechanistic uncertainty in the biogeochemical controls on soil C storage in these ecosystems. Poorly-crystalline minerals have long been known to stabilize soil C, but few studies have explored their relative importance in comparison with other likely controls such as rhizosphere processes, oxygen deficiency (anaerobiosis), and C quality. We examined relationships among soil C and a suite of biogeochemical variables measured in 162 samples from surface soils (ultisols and oxisols) collected over scales of landforms to landscapes (m - km) in the Luquillo Experimental Forest, Puerto Rico. We measured iron (Fe), aluminum (Al), and manganese (Mn) oxides in 0.5M hydrochloric acid (HCl), sodium citrate/ascorbic acid (CA), and citrate/dithionite (CD) extractions, along with clay content, root biomass, C quality (C/N ratios), and anaerobiosis using HCl-extractable reduced iron (Fe(II)) concentrations as a proxy. We used mixed-effects models to compare the relative importance of the above variables (normalized by mean and standard deviation) as predictors of soil C, with random effects to account for spatial structure. Poorly-crystalline Al oxide concentrations (CA extraction), soil C/N ratio, and Fe(II) concentrations each had highly significant (p < 0.0001) positive relationships with soil C concentrations that conveyed equivalent explanatory power, assessed by comparing standardized regression coefficients. The optimal mixed model explained 82 % of the variation of the residual sum of squares of soil C concentrations, which varied between 2 - 20 % C among samples. Fine root biomass had a weak but significantly positive association with soil C concentrations (p < 0.05), while crystalline Fe oxide concentrations (CD extraction) displayed a negative correlation (p < 0.01), and clay contents had no significant relationship. The latter results are surprising given the documented role of Fe oxides and clay minerals in C stabilization, yet may indicate the importance of C supply via roots in controlling C concentrations in humid tropical ecosystems. Samples associated with high concentrations of crystalline Fe and high clay contents may represent soils from deeper in the soil profile exposed by landslides, characterized by poorly-developed aggregate structure and fewer C inputs since disturbance. Our optimal mixed model suggested an equivalent importance of soil mineralogy, anaerobiosis, and C quality as correlates of soil C concentrations across tropical forest ecosystems varying in temperature, precipitation, and community composition. Whereas soil mineralogy may be relatively static over timescales of years to decades, O2 availability and the chemical composition of soil C inputs and can potentially vary more rapidly. Our model suggests that changes in temperature and precipitation regimes that alter O2 availability and/or increase the lability of C inputs may lead to decreased soil C storage in humid tropical forest soils.

  3. Atrazine and its metabolites degradation in mineral salts medium and soil using an enrichment culture.

    PubMed

    Kumar, Anup; Singh, Neera

    2016-03-01

    An atrazine-degrading enrichment culture was used to study degradation of atrazine metabolites viz. hydroxyatrazine, deethylatrazine, and deisopropylatrazine in mineral salts medium. Results suggested that the enrichment culture was able to degrade only hydroxyatrazine, and it was used as the sole source of carbon and nitrogen. Hydroxyatrazine degradation slowed down when sucrose and/or ammonium hydrogen phosphate were supplemented as the additional sources of carbon and nitrogen, respectively. The enrichment culture could degrade high concentrations of atrazine (up to 110?g/mL) in mineral salts medium, and neutral pH was optimum for atrazine degradation. Further, except in an acidic soil, enrichment culture was able to degrade atrazine in three soil types having different physico-chemical properties. Raising the pH of acidic soil to neutral or alkaline enabled the enrichment culture to degrade atrazine suggesting that acidic pH inhibited atrazine-degrading ability. The study suggested that the enrichment culture can be successfully utilized to achieve complete degradation of atrazine and its persistent metabolite hydroxyatrazine in the contaminated soil and water. PMID:26846292

  4. Dynamic Response of Forest Litter and Mineral Soil to Pulsed Water Additions

    NASA Astrophysics Data System (ADS)

    Boot, C. M.; Schaeffer, S. M.; Carbone, M. S.; Still, C. J.; Schimel, J.

    2010-12-01

    Quantifying microbial responses to drought and moisture pulses are essential to understanding terrestrial C cycling in a changing climate. Using laboratory incubations we sought to determine if water added in multiple consecutive pulses to pine forest litter and mineral soil resulted in different C dynamics than water added in a single event. Soils were collected from two sites on Santa Cruz Island located in Channel Islands National Park 40 km southwest of Santa Barbara, CA. Both sites are dominated by Bishop pine (Pinus muricata) mixed with chaparral shrubs, with a ~3-10 cm thick litter layer. The sites differ, however, in the frequency and amount of precipitation received. Following water additions as either one or three pulses (equal total volume) we measured respiration, dissolved organic carbon (DOC) and microbial biomass carbon (MBC) over twenty-two days after the first water addition. Three days after the initial water addition in the litter samples the DOC and MBC for both treatments were not different; however, the temporal dynamics varied by site with the high precipitation site responding more quickly and with a higher magnitude than the low precipitation site. In both the litter and mineral soil respiration rate correlated with soil moisture (r2=0.91 and 0.84 respectively). Our results suggest that the water history and other site-specific characteristics were more important in the response to pulsed water additions than how the water was introduced to the system.

  5. Modeling mineral dust emissions from the Sahara desert using new surface properties and soil database

    NASA Astrophysics Data System (ADS)

    Laurent, B.; Marticorena, B.; Bergametti, G.; LOn, J. F.; Mahowald, N. M.

    2008-07-01

    The present study investigates the mineral dust emissions and the occurrence of dust emission events over the Sahara desert from 1996 to 2001. Mineral dust emissions are simulated over a region extending from 16N to 38N and from 19W to 40E with a ? ? spatial resolution. The input parameters required by the dust emission model are surface features data (aerodynamic roughness length, dry soil size distribution and texture for erodible soils), and meteorological surface data (mainly surface wind velocity and soil moisture). A map of the aerodynamic roughness lengths is established based on a composition of protrusion coefficients derived from the POLDER-1 surface products. Soil dry size distribution and texture are derived from measurements performed on soil samples from desert areas, and from a soil map derived from a geomorphologic analysis of desert landscapes. Surface re-analyzed meteorological databases (ERA-40) of the European Centre for Medium range Weather Forecasts (ECMWF) are used. The influence of soil moisture on simulated dust emissions is quantified. The main Saharan dust sources identified during the 6-year simulated period are in agreement with the previous studies based on in situ or satellite observations. The relevance of the simulated large dust sources and point sources ("hot spots") is tested using aerosol indexes derived from satellite observations (TOMS Absorbing Aerosol Index and Infrared Dust Difference Index Meteosat). The Saharan dust emissions simulated from 1996 to 2001 range from 585 to 759 Tg a-1. The simulations show marked seasonal cycles with a maximum in summer for the western Sahara and in spring for the eastern Sahara. The interannual variability of dust emissions is pronounced in the eastern part of the Sahara while the emissions from the western Sahara are more regular over the studied period. The soil moisture does not noticeably affect the Saharan dust emissions, their seasonal cycle or their interannual variability, but it can partly control and limit the dust emissions in some parts of the northern desert margin, where the precipitation rates are higher. Our simulations also tend to confirm that the Sahara is the major terrestrial source of mineral dust.

  6. Bioremediation of experimental petroleum spills on mineral soils in the Vestfold Hills, Antarctica

    SciTech Connect

    Kerry, E. )

    1993-01-01

    The effect of nutrient and water enhancement on the biodegradation of petroleum was tested in Antarctic mineral soils. Nitrogen, phosphorus and potassium were applied in solution, with or without gum xanthan or plastic covers, to sites artificially contaminated with distillate. The effectiveness of these procedures was assessed by measuring changes in total petroleum hydrocarbons; heptadecane/pristane and octadecane/phytane ratios; in concentrations of major hydrocarbon components and in microbial numbers and activity. Significantly lower hydrocarbon concentration were recorded after one year in soils treated with fertilizer solutions, but only in the surface 3 cm. These soils also showed lowered heptadecane/pristane and octadecane/phytane ratios and had the highest levels of microbial activity relative to other plots. Soils treated with gum xanthan or covered with plastic had the highest residual hydrocarbon levels. Both treatments inhibited evaporative loss of hydrocarbon, and there were indications that gum xanthan was utilized by the microbiota as an alternative carbon source to distillate. Higher temperatures were recorded under the plastic but no stimulation of biodegradation was detected. Estimated numbers of metabolically active bacteria were in the range 10[sup 7] to 10[sup 8] g[sup [minus]1] dry weight of soil, with an estimated biomass of 0.03 to 0.26 mg g[sup [minus]1] soil. Estimated numbers of amoebae were in the range 10[sup 6] 10[sup 7] g[sup [minus]1] soil (biomass of 2 to 4 mg g[sup [minus]1]). The highest populations were recorded in fertilized, contaminated soils, the only soils where petroleum degradation was demonstrated. 23 refs., 1 fig., 4 tabs.

  7. The Role of Elevated PCO2 on Selenate and Selenite Sorption to and Desorption from Calcareous Soils and Carbonate Minerals

    NASA Astrophysics Data System (ADS)

    Jacobson, A. R.; Wen, L.

    2013-12-01

    Selenium is a minor component of highly weatherable rock formations in the Uintah Basin Utah from which soils are formed. Activities such as soil/gas extraction and irrigated agriculture may be accelerating the mobilization of Se in the soils, which eventually reach the Pariette Wetlands. Since the wetlands are a stopping point for migratory water fowl, the elevated levels of Se detected in the sediments and waters are of concern. Understanding soil mechanisms related to selenium transport through soils is critical to managing the contamination. In microbially active agricultural soils concentrations of CO2 in the soil air may be 10 to 100 times higher than at the soil surface. CO2 dissolved in the soil solution forms numerous carbonate species that may enhance or compete with selenate and selenite sorption/desorption from soil. Thus we investigated the partitioning of Se between the immobile solid phase and mobile solution phase in six calcareous soils and three carbonate minerals by the batch sorption method at ambient and elevated PCO2. We hypothesized that in these highly buffered soils competition from carbonate species would result in decreased Se sorption. Results indicate that at elevated PCO2 selenate and selenite sorption increased in all soils and minerals tested relative to sorption at ambient levels. Minimal desorption occurred with a dilute electrolyte solution, but could be induced in the presence of phosphate. This finding suggests that actively respiring soils mitigate Se transport to ground or surface waters.

  8. [Characteristics of soil net nitrogen mineralization in subalpine/alpine forests of west Sichuan, Southwest China during seasonal freeze-thaw period].

    PubMed

    Liu, Jin-Ling; Wu, Fu-Zhong; Yang, Wan-Qin; Shi, Pei-Li; Wang, Ao; Yang, Yu-Lian; Wu, Zhi-Chao

    2012-03-01

    Seasonal freeze-thaw cycle and its change pattern under the scenarios of climate warming might exert strong effects on the soil nitrogen mineralization in alpine forests. In this paper, intact soil cores were collected from the subalpine/alpine forests along an altitudinal gradient in west Sichuan, and an incubation test was conducted to study the soil net nitrogen mineralization rate and the amount of soil mineralized nitrogen in the forests during growth season and seasonal freeze-thaw period under simulated scenarios of global warming. In the test soils, the NH(4+)-N and NO(3-)-N contents both showed a clear tendency of decreased in the period from growth season to the onset stage of freezing, increased at deep freezing stage, and decreased again at the early stage of thawing. The soil net nitrogen mineralization rate and the amount of soil mineralized nitrogen were significantly lower in freeze-thaw period than in growth season, and the soil inorganic nitrogen was obviously immobilized. The soil nitrogen immobilization was stronger at middle altitudes but weaker at high altitudes, as compared with that at low altitudes, possibly due to the variation of soil temperature and its induced different freeze-thaw cycle. During growth period, the soil net nitrogen mineralization rate and the amount of soil mineralized nitrogen showed an obvious increasing trend with the decrease of altitude, and the soil nitrogen mineralization was the strongest at low altitudes, implying that under the scenarios of climate warming, the increase of soil temperature promoted the soil nitrogen mineralization during growth season, and affected the soil nitrogen mineralization rate by increasing the frequency of freeze-thaw cycle and shortening the time period of freeze-thaw. Soil micro-environment could also affect the soil nitrogen mineralization in alpine forest regions. PMID:22720601

  9. Carbonation of Artificial Silicate Minerals in Soils: Passive Removal of Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Washbourne, C.; Renforth, P.; Manning, D. A.

    2010-12-01

    Sequestration of CO2 in global soils is a widely recognised phenomenon, which is amenable to an environmental engineering approach. It is proposed that the use of direct soil engineering, promoting CO2 sequestration by accelerating the activity of reactive mineral substrates, has the potential to harness the significant carbon turnover of the global pedologic system (75 x 10^15 gC/yr [1]) [2][3][4]. Estimates of C capture potential through this process are 100-1000 MTa-1. This study focuses on the ambient carbonation of high-Ca residues as agents of mineral CCS. A synergy of contemporary field observations is presented, alongside data acquired from laboratory testing (acid digestion, optical petrography, SEM, IRMS) of carbonated material recovered from urban brown-field and former industrial sites in north east England. It is demonstrated that urban soils may accumulate ~30 kg/m2 (300 T/ha) of carbon over 10 years as inorganic calcium carbonate, approximately twice the typical organic C content of rural soils, ~17.5 kg/m2 in the UK. Stable isotope data (δ13C and δ18O) confirm that over 90% of the carbon is derived from the atmosphere. Economic and mechanical constraints on experimental performance in industrial batch reactor settings have strongly influenced the contemporary view on the efficacy of mineral CCS for large-scale environmental application [5][6][7]. Effective, low-energy field-scale implementation of mineral CCS through soil engineering would counter many of these concerns. Proof of principle for carbon capture efficacy of artificial silicates in soil engineering has been demonstrated [4]; proof of field scale feasibility will be demonstrated though continuing empirical field observation, engineered field cell construction and laboratory investigation. [1] Schlesinger, W. H., et al. (2000), Biogeochemistry, Vol. 48: 7-20. [2] Lal, R. (2003), Critical Reviews in Plant Sciences, 22, pp. 151-184. [3] Manning, D. A. C., (2008), Mineralogical Magazine, Mineralogical Society, Vol. 72: 639-649. [4] Renforth, P., et al., (2009), Applied Geochemistry, Vol. 24(9): 1757-1764 [5] Butt, D. P., Lackner, K.S., Wendt, C.H., et al. (1997), Global Warming International Conference, Columbia University, NY. [6] Huijgen, W. J. J., et al. (2005), Environmental Science and Technology Vol. 39: 9676-9682. [7] Lackner, K. S., et al. (1997), Energy Conversion and Management Vol. 38: S259-S264.

  10. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  12. 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

    2016-01-01

    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

  13. The study of the soil clay minerals within the framework of the integrated research headed by N.I. Bazilevich

    NASA Astrophysics Data System (ADS)

    Chizhikova, N. P.

    2010-11-01

    The main areas of the integrated biogeochemical studies performed under the supervision of N.I. Bazilevich dealing with the investigation of soil minerals were considered. The development of the clay profiles in soils under the effect of chernozem formation, solodization, salinization, solonetzization, and gleyzation, the spatial differentiation of which favored the development of the pronounced complexity of the soil cover in the forest-steppe zone of the Baraba Lowland, was described. It was shown that irrigation with sodic water induces the evolution of chernozems to solodized soils due to the dispersion and destruction of the clay minerals. The behavior of the minerals in the sodic solonetz-solonchaks of Armenia during their reclamation with sulfuric acid and iron (II) sulfate was explained. The effect of the root exudates from black saxaul ( Haloxylon aphyllum) on the transformation of the layered silicates in the rooting zone of sandy desert soils was noted.

  14. Effect of foliar and soil application of potassium fertilizer on soybean seed protein, oil, fatty acids, and minerals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to evaluate the effectiveness of soil and foliar application of potassium (K) on leaf and seed mineral concentration levels, and seed composition (protein, oil, fatty acids, and minerals). Soybean cultivar (Pioneer 95470) of maturity group 5.7 was grown in a repeat...

  15. Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

    NASA Astrophysics Data System (ADS)

    Wissmeier, L.; Barry, D. A.

    2009-08-01

    The selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards' equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC's comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil's hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter ?. Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even increase during precipitation due to changes in the pore-size distribution.

  16. Andic soils : mineralogical effect onto organic matter dynamics, organic matter effect onto mineral dynamics, or both?

    NASA Astrophysics Data System (ADS)

    Basile-Doelsch, Isabelle; Amundson, Ronald; Balesdent, Jrome; Borschneck, Daniel; Bottero, Jean-Yves; Colin, Fabrice; de Junet, Alexis; Doelsch, Emmanuel; Legros, Samuel; Levard, Clment; Masion, Armand; Meunier, Jean-Dominique; Rose, Jrme

    2014-05-01

    From a strictly mineralogical point of view, weathering of volcanic glass produces secondary phases that are short range ordered alumino-silicates (SRO-AlSi). These are imogolite tubes (2 to 3 nm of diameter) and allophane supposedly spheres (3.5 to 5 nm). Their local structure is composed of a curved gibbsite Al layer and Si tetrahedra in the vacancies (Q0). Proto-imogolites have the same local structure but are roof-shape nanoparticles likely representing the precursors of imogolite and allophanes (Levard et al. 2010). These structures and sizes give to the SRO-AlSi large specific surfaces and high reactivities. In some natural sites, imogolites and allophanes are formed in large quantities. Aging of these phases may lead to the formation of more stable minerals (halloysite, kaolinite and gibbsite) (Torn et al 1997). In natural environments, when the weathering of volcanic glass is associated with the establishment of vegetation, the soils formed are generally andosols. These soils are particularly rich in organic matter (OM), which is explained by the high ability of SRO-AlSi mineral phases to form bonds with organic compounds. In a first order "bulk" approach, it is considered that these bonds strongly stabilize the organic compounds as their mean age can reach more than 10 kyrs in some studied sites (Basile-Doelsch et al. 2005; Torn et al. 1997). However, the structure of the mineral phases present in andosols deserves more attention. Traditionally, the presence in the SRO-AlSi andosols was shown by selective dissolution approaches by oxalate and pyrophosphate. Using spectroscopic methods, mineralogical analysis of SRO-AlSi in andosols samples showed that these mineral phases were neither imogolites nor allophanes as originally supposed, but only less organized structures remained in a state of proto-imogolites (Basile-Doelsch al. 2005 ; Levard et al., 2012). The presence of OM would have an inhibitory effect on the formation of secondary mineral phases, by blocking the crystal growth of SRO-AlSi. Conversely, the effect of minerals on the dynamics of organic compounds also deserves to be studied in greater detail. If the "bulk" approaches showed that proto-imogolites involve long-term stabilized OM, other approaches such as densimetric fractionation and C3/C4 chronosequences (Basile-Doelsch et al. 2007; De Junet et al. 2013) led us to consider a new model involving two types of organo-mineral interactions: (1) OM stabilized by strong bonds to proto-imogolite, leading to a slow OM turnover and (2) OM retained within the porosity of the 3D structure formed by the proto-imogolite (similar to a gel structure), leading to a faster OM turnover. Understanding the mechanisms of organo-mineral interactions in andosols will open new research directions for understanding the mechanisms of stabilization of OM in any type of soil (Bonnard et al. 2012). Basile-Doelsch et al., Geoderma, 137, 477-489, 2007. Basile-Doelsch et al., European Journal of Soil Science, 56, 689-703, 2005. Bonnard et al., European Journal of Soil Science, 63, 5, 625-636, 2012. de Junet, et al., Journal of Analytical and Applied Pyrolysis, 99, 92-10, 2013, Levard et al, Geoderma, 183-184, 100-108, 2012. Levard et al. Chemistry Of Materials, 22, 2466-2473, 2010 Torn et al. Nature, London, 389, 170-173, 1997.

  17. 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.

  18. Accumulation and turnover of carbon in organic and mineral soils of the BOREAS northern study area

    USGS Publications Warehouse

    Trumbore, S.E.; Harden, J.W.

    1997-01-01

    Rates of input, accumulation, and turnover of C differ markedly within soil profiles and in soils with different drainage in the BOREAS northern study area. Soil C storage increases from ???3 kg C m-2 in well-drained, sandy soils to greater than 100 kg C m-2 in wetlands. Two modes of C accumulation were observed in upland soil profiles. Large annual C inputs (0.06-0.1 kg C m-2 yr-1) and slow decomposition (turnover times of 6-250 years) lead to rapid C accumulation in regrowing surface moss and detrital layers following fire. Deep organic layers that have accumulated over the millennia since the initiation of soil development, and are located below the most recent charred horizon, show slower rates of input (0.015-0.03 kg C m-2 yr-1) and turnover (100-1600 years) and accumulate C about 10 times slower than surface detrital layers. Rates of C input to soils derived from C and 14C data were in accord with net primary production estimates, with highest rates of input (0.14-0.6 kg C m-2 yr-1) in wetlands. Turnover times for C in surface detrital layers were 6-15 years for well-drained sand soils that showed highest soil temperatures in summer, 30-40 years for wetlands, and 36-250 years for uplands with thick moss cover and black spruce trees. Long (>100 years) turnover times in upland black spruce/clay soils most likely reflect the influence of woody debris incorporated into detrital layers. Turnover times for deep organic and mineral layer C were controlled by drainage, with fastest turnover (80-130 years) in well-drained sand soils and slowest turnover (>3000 years) in wetlands. Total C accumulation rates, which account for C losses from both deep organic and surface detrital layers, are close to zero for sand/jack pine soils, 0.003-0.01 kg C m-2 yr-1 for moderately to poorly drained sites in mature forest stands, and 0.03 kg C m-2 yr-1 for a productive fen. Decomposition of organic matter more than several decades old accounts for 9-22% of total heterotrophic respiration at these sites. The rates of C accumulation derived here are decadal averages for specific stands and will vary as stands age or undergo disturbance. Extrapolation to larger regions and longer timescales, where burning offsets C gains in moss layers, will yield smaller rates of C storage.

  19. ACCUMULATION AND CROP UPTAKE OF SOIL MINERAL NITROGEN AS INFLUEMCED BY TILLAGE, COVER CROPS, AND NITROGEN FERTILIZATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil and crop management practices may influence soil mineral N, crop N uptake, and N leaching. We evaluated the effects of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)]...

  20. Biochar and manure effects on net nitrogen mineralization and greenhouse gas emissions from calcareous soil under corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Few multiyear field studies have examined the impacts of a one-time biochar application on net N mineralization and greenhouse gas emissions in an irrigated, calcareous soil; yet such applications are hypothesized as a means of sequestering atmospheric CO2 and improving soil quality. We fall-applie...

  1. Influence of residue and nitrogen fertilizer additions on carbon mineralization in soils with different texture and cropping histories

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using soil sampled from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ul...

  2. Zinc Fertilization Plus Liming to Reduce Cadmium Uptake by Romaine Lettuce on Cd-Mineralized Lockwood Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lockwood shaly loam (Pachic Argixerolls) and similar Cd mineralized soils derived from marine shale in California contain higher Cd levels and higher Cd:Zn ratios than uncontaminated US soils, and produce leafy vegetables with considerably higher Cd than is normal for US lettuce. Previous work by B...

  3. SOIL NITROGEN MINERALIZATION AND MICROBIAL BIOMASS IN FORAGE PRODUCTION SYSTEMS: INFLUENCES OF NITROGEN FERTILIZATION RATES AND TYPES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our objective was to determine the effects of swine lagoon effluent (SLE)and ammonium nitrate (AN) on soil N supplying capacity and microbial functional groups of N mineralizers and nitrifiers in a forage production system. We collected soils at 0 7.5 cm depth in 2004 from field plots planted with...

  4. Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil

    NASA Astrophysics Data System (ADS)

    Lind, Saara E.; Shurpali, Narasinha J.; Peltola, Olli; Mammarella, Ivan; Hyvönen, Niina; Maljanen, Marja; Räty, Mari; Virkajärvi, Perttu; Martikainen, Pertti J.

    2016-03-01

    One of the strategies to reduce carbon dioxide (CO2) emissions from the energy sector is to increase the use of renewable energy sources such as bioenergy crops. Bioenergy is not necessarily carbon neutral because of greenhouse gas (GHG) emissions during biomass production, field management and transportation. The present study focuses on the cultivation of reed canary grass (RCG, Phalaris arundinacea L.), a perennial bioenergy crop, on a mineral soil. To quantify the CO2 exchange of this RCG cultivation system, and to understand the key factors controlling its CO2 exchange, the net ecosystem CO2 exchange (NEE) was measured from July 2009 until the end of 2011 using the eddy covariance (EC) method. The RCG cultivation thrived well producing yields of 6200 and 6700 kg DW ha-1 in 2010 and 2011, respectively. Gross photosynthesis (GPP) was controlled mainly by radiation from June to September. Vapour pressure deficit (VPD), air temperature or soil moisture did not limit photosynthesis during the growing season. Total ecosystem respiration (TER) increased with soil temperature, green area index and GPP. Annual NEE was -262 and -256 g C m-2 in 2010 and 2011, respectively. Throughout the study period from July 2009 until the end of 2011, cumulative NEE was -575 g C m-2. Carbon balance and its regulatory factors were compared to the published results of a comparison site on drained organic soil cultivated with RCG in the same climate. On this mineral soil site, the RCG had higher capacity to take up CO2 from the atmosphere than on the comparison site.

  5. Carbon and nitrogen mineralization in a vineyard soil amended with grape marc vermicompost.

    PubMed

    Paradelo, Remigio; Moldes, Ana Beln; Barral, Mara Teresa

    2011-11-01

    Vineyard soils in many areas suffer from low organic matter contents, which can be the cause of negative effects such as increasing the risk of erosion, so the use of organic amendments must be considered a good agricultural practice. Even more, if grape marc is recycled as a soil amendment in the vineyards, benefits from a good waste management strategy are also obtained. In the present study, a grape marc from the wine region of Valdeorras (north-west Spain) was used for the production of vermicompost, and this added to a vineyard soil of the same area in a laboratory study. Mixtures of soil and grape marc vermicompost (2 and 4%, dry weight) were incubated for ten weeks at 25C and the mineralization of C and N studied. The respiration data were fitted to a first-order kinetic model. The rates of grape marc vermicompost which should be added to the vineyard soil in order to maintain the initial levels of organic matter were estimated from the laboratory data, and found to be 1.7?t?ha(-1)?year(-1) of bulk vermicompost (if the present mean temperature is considered) and 2.1?t?ha(-1)?year(-1) of bulk vermicompost (if a 2C increment in temperature is considered), amounts which could be obtained recycling the grape marc produced in the exploitation. PMID:20837558

  6. Mineral cycling in soil and litter arthropod food chains. Progress report, November 1, 1979-October 31, 1980

    SciTech Connect

    Crossley, Jr, D A

    1980-08-01

    Recent progress and current status are reported for research concerned with mineral element dynamics in soil arthropod food chains. Research is performed within the larger context of terrestrial decomposition systems, in which soil arthropods may act as regulators of nutrient dynamics during decomposition. Research is measuring rates of nutrient accumulation and excretion by using radioactive tracer techniques with radioactive analogs of nutrients. Experimental measurement of radioactive tracer excretion and nutrient element pools are reported for soil microarthropods, using new methods of counting and microprobe elemental analysis. Research on arthropod-fungal relations is utilizing high-efficiency extraction followed by dissection of 13 x 13 cm soil blocks. A two-component excretion model is reported for Cobalt-60 in earthworms (Eisenia foetida), demonstrating that no assimilation of cobalt occurs from the mineral soil fraction but is entirely from organic matter. Collection of data sets on soil arthropod communities and abundances is completed.

  7. Mineralization of nitrogen compounds in a soil under an oxalis birch forest

    NASA Astrophysics Data System (ADS)

    Razgulin, S. M.

    2013-02-01

    The total mineralization of nitrogen in the AO-A1 (0-6 cm), A1 (6-11 cm), and A2 (11-21 cm) horizons of a soddy pale-podzolic soil under an oxalis birch forest in Yaroslavl oblast was measured from May to November in 2009 and 2010 and comprised 6.7 0.9, 3.0 0.4, and 5.5 0.6 g of N/m2 in 2009 and 5.6 0.5, 2.5 0.2, and 2.1 0.5 g of N/m2 in 2010, respectively. The total nitrification reached 0.4 0.1, 1.1 0.2, and 1.4 0.1 g of N/m2 in 2009 and 1.0, 0.6, and 0.7 g of N/m2 in 2010. Overall, the amount of mineralized nitrogen in the 21-cm-deep soil layer in 2009 and 2010 constituted 15.2 1.1 and 10.2 0.7 g of N/m2, respectively. The contribution of nitrification to the nitrogen mineralization amounted to 20%. The seasonal variations in the soil temperature and moistening affected the concentrations of ammonium in the upper horizons and the accumulation of ammonium in the AO-A1 and A1 horizons. The combined effect of the temperature and moisture controlled the ammonification in the AO-A1 horizon ( R = 0.83 at p = 0.16 in 2010), the nitrification in all the studied horizons ( R = 0.86 at p= 0.13 in 2009), and the ammonia emission from the soil surface ( R = 0.92 at p = 0.06 in 2010). A correlation between the seasonal dynamics of the ammonification and the CO2 emission was found for the AO-A1 horizon ( r = 0.64 at p = 0.16 in 2010) and was absent in the deeper layers of the soil profile. The nitrogen losses from the soil surface due to the ammonia emission in the investigated periods reached 95 31 g of N/ha (2009) and 33 30 g of N/ha (2010).

  8. 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

  9. [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. PMID:26717705

  10. A Comparative Analyses of Granulometry, Mineral Composition and Major and Trace Element Concentrations in Soils Commonly Ingested by Humans.

    PubMed

    Ngole-Jeme, Veronica M; Ekosse, Georges-Ivo E

    2015-08-01

    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

  11. Effect of electrolytes and soil mineral surfaces on N2O hydrate formation kinetics

    NASA Astrophysics Data System (ADS)

    Kyung, D.; Ha, S.; Lee, W.

    2013-12-01

    Nitrous oxide (N2O) is one of the main greenhouse gases (GHGs) defined by IPCC (Intergovernmental Panel on Climate Change) and its global warming potential (GWP) is 310 times higher than that of carbon dioxide (CO2). Gas hydrates are unique crystalline compounds that trap suitable guest gas molecules (size between 0.35 and 0.9 nm) stably inside the hydrogen-bonded water cages via van der Waals interaction under high pressure and low temperature conditions. N2O has similar properties (e.g. van der Waals diameter, molar mass, density, etc.) with CO2 except for polarity and it was revealed that both N2O and CO2 can be formed as hydrate s-I in natural environment. In this study, we have identified the effect of electrolytes (NaCl, KCl, CaCl2, MgCl2) and solid surfaces (illite, nontronite, sphalerite, kaolinite, montmorillonite) on the N2O hydrate formation kinetics. The hydrate formation experiments were conducted by injecting N2O gas into the soil mineral suspensions with and without electrolytes in a 50mL pressurized vessel. The formation of N2O hydrate in aqueous electrolyte solutions was slower than that in deionized water. Ion charge and size were significant factors affecting N2O hydrate formation kinetic in electrolytes solutions. The addition of soil mineral suspensions accelerated the formation of N2O hydrate in the electrolyte solutions. Surface area and ionic strength of soil minerals highly influenced on formation kinetic of N2O hydrate. The hydrate formation times in the solid suspensions without electrolytes were very similar to that in the deionized water. The results obtained from this research could be indirectly applied to the fate of N2O sequestered into geological formations as well as its storage as a form of N2O hydrate.

  12. Geoarchaeological conclusions through investigating sediments, soils and minerals in karst depressions in Mount Ida, Central Crete

    NASA Astrophysics Data System (ADS)

    Holzhauer, I.; Siart, C.; Meyer, H. P.; Schukraft, G.; Altherr, R.; Eitel, B.

    2009-04-01

    The investigation of sediments, soils and minerals can provide important information for the reconstruction of past landscapes and the human impact on the environment. In this context, sediment-filled karst depressions function as archives as their different sediment structures reflect various superficial conditions and associated man-made changes in the environmental system. The study area, namely the doline of Zominthos, is located at 1200 m a.s.l. in the Ida Mountains in Central Crete and is known for its remnants of a late Minoan settlement complex (Neopalatial Period, ~1600 BC). Our purpose is to help understand the past human-environmental interactions in the Central Cretan highlands through the use of several sedimentological and mineralogical methods including percussion drilling and subsequent analysis with polarisation microscopy, SEM, EPMA and XRD investigations. The macroscopic evaluation of the core profiles and the micromorphological studies of thin sections give evidence of colluvial sediments within the doline which are interbedded with fine-grained, graded horizons featuring clearly fluvial textures. They must be considered with regard to intense landuse and deforestation of the surrounding escarpments. The mineralogical investigations show the coincident abundance of well-preserved angular minerals on the one side and heavily weathered minerals on the other side. This leads to the assumption of at least two different generations of minerals that underwent a various history of subaerial exposure. The vast majority of heavy minerals (e.g. carpholites, chloritoid, garnets, spinels) cannot derive from the limestone bedrock and must stem from allochthonous sources. They originate from metamorphic rocks that do not outcrop in the catchment area of Zominthos. However, they must have existed here in former times when klippes provided the concerning minerals for the buildup of the soil cover. Hence, the palaeorelief must have been different with divergent lithology. Considerable amounts of volcanogenic pyroxenes and amphiboles have been found, which can clearly be connected with the Thera eruption of Santorini 1620 BC. They have been found all over the core profiles and thus provide a time marker for the intense man-made geomorphodynamics since the date of the intense ash fallout over Crete. More than 10 up to 15 metres of pedosediments have been deposited in the Zominthos doline in the last 3400 years. Furthermore, large amounts of remarkable and very rare mineral species have been detected within the pedosediments, e.g. ferrocarpholite. The observed light minerals, respectively diverse quartz grains, show varied grain morphologies that indicate fluvial, aeolian as well as tectonic impacts. The clay mineralogy of the limestone residues and the pedosediments was investigated, showing significant amounts of kaolinite within the latter, which can be attributed to strong southern wind regimes that transported the particles from the Sahara into the study area. In contrast, the bedrock lacks completely in this allochthonous aeolian dust component. In addition, the strong polygenetic nature of the sediment fills has to be stated. The prevalent assumption of an autochthonous thin and clayey residue in karst depressions can not be confirmed. The human impact on this landscape is crucial and plays a major role regarding the composition and genesis of the sedimentary fills. The application of combined sedimentological and mineralogical investigations for (geo)archaeological purposes is still a quite exceptional approach. As shown by the results, it can deliver important information for the reconstruction of past human-environmental systems, which are encoded in minerals, sediments and soil properties.

  13. Mineralization of nitrogen compounds in soils of south-taiga ecosystems

    NASA Astrophysics Data System (ADS)

    Razgulin, S. M.

    2010-06-01

    The productivity of the nitrogen mineralization in the A0 (0-2 cm), A1 (2-3 cm), and A2 (3-13 cm) horizons of a soddy-podzolic soil was measured in a wood-sorrel-whortleberry birch forest (7Birch3Asp, 80 years, the second stand quality class, tree canopy density 0.7, Yaroslavl oblast) using the sample incubation method; the measurements were performed from May till October in eight replicates for each horizon. In 2007, 5.85 0.73 g N/m2 were mineralized in the soil. In the litter, 2.01 0.23 g N/m2 were mineralized, whereas 0.35 0.03 and 3.49 0.72 g N/m2 were mineralized in the A1 and A2 horizons, respectively. In 2008, 3.34 0.25 g N/m2 were mineralized in the A0 and A1 horizons, of which 2.44 0.23 g N/m2 were in the former. Ammonification prevailed in all the horizons. The contribution of nitrification was assessed as 1.6 and 0.3% of the processs productivity in 2007 and 2008, respectively. The Corg and Norg pools decreased in the litter by 407 g C/m2 and 13.7g N/m2 (or 33%) from May to October. Of this carbon amount, 67% is spent for humification and the organic mass preservation and 33% was transformed to carbonic acid. The nitrogen expenses for the synthesis of humus acids are equal to 70 and 30%; it is spent equally for the mineralization of the element and its immobilization by microorganisms. In the A0 and A1 horizons, the seasonal trends of the ammonification correlated with the carbon dioxide emission from these horizons in the year of 2008 with r = 0.75 atp = 0.09 and r = 0.82 atp = 0.04 for both horizons, respectively.

  14. Effects of temperature on microbial C metabolism in peat and mineral soil

    NASA Astrophysics Data System (ADS)

    Hagerty, S.; Dijkstra, P.; Miller, E.; Schwartz, E.; KOCH, G. W.; Hungate, B. A.

    2013-12-01

    Microbial metabolism, the main mechanism responsible for soil CO2 emissions, plays an important role in the global C cycle. Increased temperature generally stimulates decomposition and respiration, indicative of increased microbial C metabolism and possibly greater energy demand by microbes for growth and maintenance. Changes in microbial metabolism with temperature may manifest differently in microbial communities from soils with different C availability because it is generally expected that when more organic C is present, carbon use efficiency (CUE) will be lower and more CO2 will be released per unit C assimilated by microbes than when less C substrate is available. In this study we examined the effect of temperature on C processing in peat and mineral soil from the Marcel Experimental Forest in Minnesota. Samples were incubated for 7 days at 5, 10, 15, and 20C. We used position-specific 13C-labeled tracers to model C flux through the central C metabolic network (i.e. glycolysis, pentose phosphate pathway, and the citric acid cycle) and to asses the CUE of microbial communities. We also measured total CO2 production and microbial biomass, and we calculated the metabolic quotient (qCO2), which is the rate of CO2, respired per unit of microbial biomass. We found that temperature and soil type did not affect CUE and patterns of C flow through the central C metabolic network. Increased temperature stimulated respiration and decreased qCO2 in peat more than the mineral soil. These results suggest temperature affects rate of C cycling, but does not alter the relative demand for energy production and biosynthesis per unit substrate-C. This implies, in contrast to expectations that at higher temperatures more substrate will be used to offset greater demand for maintenance energy, warmer temperatures will not alter the balance of growth and maintenance energy by soil microbes. Moreover, substrate availability did not result in ';wasteful' C use, but increased C cycling rates. These findings may simplify the modeling of soil respiration with climatic warming.

  15. Sol-Gel Precursors for Ceramics from Minerals Simulating Soils from the Moon and Mars

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Gavira-Gallardo, Jose-Antonio; Hourlier-Bahloul, Djamila

    2003-01-01

    Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report some preliminary results on the production of sol-gel precursors for ceramic products using mineral resources available in Martian or Lunar soil. The presence of SiO2, TiO2, and A12O3 in both Martian (44 wt.% SiO2, 1 wt.% TiO2, 7 wt.% Al2O3) and Lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from Lunar and Martian simulant soils. Clear sol-gel precursors have been obtained by dissolution of silica from Lunar simulant soil in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Thermogravimetric Analysis and X-ray Photoelectron Spectroscopy were used to characterize the elemental composition and structure of the precursor molecules. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors. In the second set of experiments, we used the same starting materials to synthesize silicate esters in acidified alcohol mixtures. Preliminary results indicate the presence of silicon alkoxides in the product of distillation.

  16. Temporal dynamics of available and microbial phosphorus and organic phosphorus mineralization in a grassland soil

    NASA Astrophysics Data System (ADS)

    Liebisch, Frank; Keller, Fabrizio; Frossard, Emmanuel; Huguenin-Elie, Olivier; Oberson, Astrid; Bünemann, Else

    2010-05-01

    Turnover of phosphorus (P) through the microbial biomass and P mineralization have been reported as two main biological factors controlling P availability in soils. This is particularly true for grassland soils where organic matter is accumulated in the topsoil and microbial activity is high. The amounts of plant available inorganic P and microbial P can fluctuate over the season, but their interaction and responses to changes in environmental conditions, fertilization and cutting are not yet well understood. Also, gross P mineralization has not yet been measured in grassland soils. We studied P mineralization and immobilization in a species rich grassland managed at low intensity (with three harvests per season) under different P inputs. The trial was established in 1992 in Watt (Switzerland). Three different P input treatments were selected: no P (NK), mineral P (NPK) and organic P (NPKorg) fertilization, with 17 kg P ha-1yr-1 applied as superphosphate and slurry, respectively (rates according to Swiss fertilizer recommendations). We used two different approaches. Firstly, available (anion exchange resin extractable) and microbial P (hexanol labile P) were measured in fresh samples periodically taken throughout the vegetation period. Secondly, an isotopic dilution technique was applied on composite topsoil samples (0-5 cm) to determine rates of basal P mineralization and microbial immobilization of P in an incubation experiment. During the season available P ranged from 0.9-3.5, 5.3-11.2 and 1.9-6.7 mg kg-1 soil-1 and microbial P from 20-44, 43-59 and 61-93 mg kg-1 soil-1 in NK, NPK and NPKorg, respectively. Thus, microbial P was highest in NPKorg whereas available P was highest in NPK. Both P pools were lowest in NK. Average annual yield was lowest in NK (4.5 t ha-1), NPKorg (6.5 kg ha-1) and highest in NPK (7.5 t ha-1). However, no consistent relationship between changes in microbial and available P and plant productivity was found. Changes in weather conditions were reflected by changes in available and microbial P measured in the field. Phosphorus flushes were observed after dry periods (microbial P reduced and available P increased). Whereas fluctuations show microbial P release and P immobilization, an expected counteraction of microbial and available P could not be fully confirmed. In the incubation experiment microbial and available P were similar to average values in the field. A higher respiration rate measured in NPKorg indicated a higher microbial activity than in the other two treatments. Despite the differences in microbial P and respiration, the 33P recovery in the microbial biomass between 3 and 30 days of incubation was about 30% in all treatments. In conclusion we found complex interactions of available and microbial P with climate, fertilization, sward cutting and plant growth. An increased immobilization of P indicated by higher microbial P in the organic fertilized treatment was not confirmed in the isotope study. Gross and net mineralization data are still under analysis and will be presented at the conference.

  17. Water vapor diffusion into a nanostructured iron oxyhydroxide.

    PubMed

    Song, Xiaowei; Boily, Jean-François

    2013-06-17

    Water diffusion through 0.4 nm × 0.4 nm wide tunnels of synthesized akaganéite (β-FeOOH) nanoparticles was studied by a coupled experimental-molecular modeling approach. A sorption isotherm model obtained from quartz crystal microbalance measurements suggests that the akaganéite bulk can accommodate a maximum of 22.4 mg of water/g (44% bulk site occupancy) when exposed to atmospheres of up to 16 Torr water vapor. Fourier transform infrared spectroscopy also showed that water molecules interact with (hydr)oxo groups on both the akaganéite bulk and surface. Diffusion reactions through the akaganéite bulk were confirmed through important changes in the hydrogen-bonding environment of bulk hydroxyl groups. Molecular dynamics simulations showed that water molecules are localized in cavities that are bound by eight hydroxyl groups, forming short-lived (<0.5 ps) hydrogen bonds with one another. Diffusion coefficients of water are three orders of magnitude lower than they are in liquid water (D = 0.0-11.1 × 10(-12) m(2)·s(-1)), whereas large integral rotational correlation times are 4 to 15 times higher (τr = 8.4-31.8 ps). Moreover, both of these properties are strongly loading-dependent. The simulations of the interface between the water vapor phase and the (010) surface plane of the akaganéite, where tunnel openings are exposed, revealed sluggish rates of incorporation between interfacial water species and their tunnel counterparts. The presence of defects in the synthesized particles are suspected to contribute to different diffusion rates in the laboratory when compared to those observed in pristine crystalline materials, as studied by molecular modeling. PMID:23701490

  18. Interactions between arsenic and iron oxyhydroxides in lacustrine sediments

    SciTech Connect

    Belzile, N.; Tessier, A. )

    1990-01-01

    Arsenic and iron concentrations were measured in surficial sediments and in interstitial and overlying waters at 22 littoral stations of 16 lakes. The lakes were chosen to cover values of pH between 4.0 and 8.4 and various As concentrations. Depth-distributions of dissolved As and Fe concentrations suggest a close association of both elements in a dissolution-diffusion-precipitation cycle for Fe and adsorbed As. Using a simplified version of the surface complexation model, apparent adsorption constants of As onto natural Fe oxyhydroxides have been calculated from the concentrations of As and Fe determined in leachates of surficial lake sediments and the in situ measurement of dissolved As in their respective overlying waters. These calculations assume, based on thermodynamic considerations and experimental evidence, that only As(V) is associated with the natural Fe oxyhydroxides. The binding intensity values obtained from these lakes are compared to those obtained for the adsorption of As(V) onto various synthetic Fe oxyhydroxides in well-defined media. The binding constants derived from field measurements agree well with those obtained from laboratory experiments performed with amorphous Fe oxyhydroxides.

  19. Surface modified mesostructured iron oxyhydroxide: synthesis, ecotoxicity, and application.

    PubMed

    Choi, Jae-Woo; Mahendran, Basuvaraj; Chung, Seung-Gun; Kim, Song-Bae; Lee, Sang-Hyup

    2014-12-01

    Mesoporous iron oxide, particularly amine-functionalized FeO(x) and FeO(x), was investigated for the removal of toxic heavy metal anions of arsenic and chromium from an aqueous solution. As a control experiment for these toxic compounds, adsorption tests were also performed on Fe3O4 as their counterpart bulk chemical. The mesostructures were confirmed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM). In addition, we prepared stock suspensions of meso-FeO(x), amine-functionalized meso-FeO(x) and Fe3O4 particles, and compared their acute toxicity against Daphnia magna. The 24 h-EC50 values of the amine-functionalized meso-FeO(x), meso-FeO(x) and Fe particle suspensions used in this study were 1682, 2549 and 95 mg/L, respectively. Organism toxicity caused by spills of adsorbents can be negated when the amine-functionalized meso-FeO(x), up to 1500 mg/L, is used as the adsorbent for heavy metal treatment. The adsorption of arsenic and chromium by the three adsorbents were examined, and different adsorption models were used to describe the equilibrium and kinetic data. The amine-functionalized meso-FeO(x) adsorbent was found to give the maximum adsorption capacities for arsenic and chromium (33.51 and 25.05 mg/g, respectively). This research gives promising results for the application of modified meso-FeO(x) as an adsorbent of toxic heavy metal anions from aqueous solutions. PMID:25654937

  20. Effects of Simulated Nitrogen Deposition on Soil Net Nitrogen Mineralization in the Meadow Steppe of Inner Mongolia, China.

    PubMed

    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 (Rm) and net nitrification (Rn) 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 Rm 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

  1. 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 (Rm) and net nitrification (Rn) 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 Rm 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

  2. Evaluation of the genotoxic potential of soil contaminated with mineral coal tailings on snail Helix aspersa.

    PubMed

    de Souza, Melissa Rosa; da Silva, Fernanda Rabaioli; de Souza, Claudia Telles; Niekraszewicz, Liana; Dias, Johnny Ferraz; Premoli, Suziane; Corrêa, Dione Silva; Soares, Mariana do Couto; Marroni, Norma Possa; Morgam-Martins, Maria Isabel; da Silva, Juliana

    2015-11-01

    Coal remains an important source of energy, although the fuel is a greater environmental pollutant. Coal is a mixture of several chemicals, especially inorganic elements and polycyclic aromatic hydrocarbons (PAH). Many of these compounds have mutagenic and carcinogenic effects on organisms exposed to this mineral. In the town of Charqueadas (Brazil), the tailings from mining were used for landfill in the lower areas of the town, and the consequence is the formation of large deposits of this material. The purpose of this study was to evaluate the genotoxic potential of soil samples contaminated by coal waste in different sites at Charqueadas, using the land snail Helix aspersa as a biomonitor organism. Thirty terrestrial snails were exposed to different treatments: 20 were exposed to the soil from two different sites in Charqueadas (site 1 and 2; 10 in each group) and 10 non-exposed (control group). Hemolymph cells were collected after 24h, 5days and 7days of exposure and comet assay, micronucleus test, oxidative stress tests were performed. Furthermore, this study quantified the inorganic elements present in soil samples by the PIXE technique and polycyclic aromatic hydrocarbons (PAH) by HPLC. This evaluation shows that, in general, soils from sites in Charqueadas, demonstrated a genotoxic effect associated with increased oxidative stress, inorganic and PAH content. These results demonstrate that the coal pyrite tailings from Charqueadas are potentially genotoxic and that H. aspersa is confirmed to be a sensitive instrument for risk assessment of environmental pollution. PMID:26295689

  3. 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.

  4. Impact of Surface Roughness and Soil Texture on Mineral Dust Emission Fluxes Modeling

    NASA Technical Reports Server (NTRS)

    Menut, Laurent; Perez, Carlos; Haustein, Karsten; Bessagnet, Bertrand; Prigent, Catherine; Alfaro, Stephane

    2013-01-01

    Dust production models (DPM) used to estimate vertical fluxes of mineral dust aerosols over arid regions need accurate data on soil and surface properties. The Laboratoire Inter-Universitaire des Systemes Atmospheriques (LISA) data set was developed for Northern Africa, the Middle East, and East Asia. This regional data set was built through dedicated field campaigns and include, among others, the aerodynamic roughness length, the smooth roughness length of the erodible fraction of the surface, and the dry (undisturbed) soil size distribution. Recently, satellite-derived roughness length and high-resolution soil texture data sets at the global scale have emerged and provide the opportunity for the use of advanced schemes in global models. This paper analyzes the behavior of the ERS satellite-derived global roughness length and the State Soil Geographic data base-Food and Agriculture Organization of the United Nations (STATSGO-FAO) soil texture data set (based on wet techniques) using an advanced DPM in comparison to the LISA data set over Northern Africa and the Middle East. We explore the sensitivity of the drag partition scheme (a critical component of the DPM) and of the dust vertical fluxes (intensity and spatial patterns) to the roughness length and soil texture data sets. We also compare the use of the drag partition scheme to a widely used preferential source approach in global models. Idealized experiments with prescribed wind speeds show that the ERS and STATSGO-FAO data sets provide realistic spatial patterns of dust emission and friction velocity thresholds in the region. Finally, we evaluate a dust transport model for the period of March to July 2011 with observed aerosol optical depths from Aerosol Robotic Network sites. Results show that ERS and STATSGO-FAO provide realistic simulations in the region.

  5. 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.

  6. Process conditions for the mineralization of a biorefractory polycyclic aromatic hydrocarbon in soils using catalyzed hydrogen peroxide

    SciTech Connect

    Stanton, P.C.; Watts, R.J.

    1996-12-31

    Catalyzed hydrogen peroxide (H{sub 2}O{sub 2} and soluble iron or mineral catalysts) was investigated as a basis for mineralizing benzo[a]pyrene (BaP), a hydrophobic and toxic polycyclic aromatic hydrocarbon, in two soils of varied complexity. The process is based on Fenton`s reagent, which can be implemented in soils to generate hydroxyl radicals. This short-lived species reacts with most organic contaminants at near diffusion-controlled rates, providing a mechanism for potential rapid soil remediation. Benzo[a]pyrene labeled with {sup 14}C was added to silica sand and a silt loam loess soil; mineralization processes were then optimized using central composite rotatable experimental designs. Variables investigated during the optimization included H{sub 2}O{sub 2} concentration, slurry volume, iron (II) amendment, and pH. Experimental data were evaluated by linear regression to develop empirical relationships and interactions between the variables. The equations were then used to develop three-dimensional response surfaces to describe BaP mineralization. The results from the response surfaces showed that 74% and 78% BaP mineralization was achieved in the silica sand and loess soils, respectively. The balance of the contaminant carbon remained with the soil fraction and was probably irreversibly sorbed. Desorption measurements over 5 d confirmed negligible desorption; however, oxidation reactions, which were complete within 24 h, documented >78% BaP mineralization, suggesting that the contaminant was oxidized, at least in part, in the sorbed phase. The results show that catalyzed H{sub 2}O{sub 2} has the ability to rapidly mineralize BaP that is not irreversibly sorbed.

  7. A mineral support and biotic catalyst are essential in the formation of highly polymeric soil humic substances

    NASA Astrophysics Data System (ADS)

    Zavarzina, A. G.

    2006-12-01

    The hypothesis was proposed that highly polymeric humic substances in the mineral horizons of soils in a temperate humid climate originate from polymerization of water-soluble structural precursors directly on mineral surfaces under the catalytic effect of immobilized phenoloxidases (heterophasic biocatalysis). This hypothesis was confirmed by a laboratory experiment using a mixture of monomeric phenols and nitrogenous compounds as structural precursors, fungal laccase as a biotic catalyst, and a hydroxyaluminum-kaolinite complex as a mineral support. Enzymic oxidation of phenolic precursors on the mineral surface was substantially more rapid than abiotic oxidation and led to synthesis of a highly polymeric fraction with a molecular weight over 75 kDa. These products were not produced on the mineral with an absence of laccase (abiotic catalysis) or in solution without the mineral matrix (homogeneous catalysis).

  8. Patterns of spatial distribution of mineral components of the complex of gray forest soils Vladimir opolye

    NASA Astrophysics Data System (ADS)

    Karpova, Dina; Chizhikova, Natalya; Starokozhko, Natalya; Hadyushina, Viktorya; Korotaeva, Valentina

    2014-05-01

    The aim of the work is the analysis of spatial distribution of soil fundamental characteristics - fine fractions content (less than 1, 1-5, 5-10 and more than 10 mkm) and their mineralogical composition. The experiments were carried out on the experimental field in Suzdal region in a trench (22 m length and 2 m depth) laid in upland, well-drained conditions. Soil samples from 5 different soil profiles were collected. Fractions were obtained by Gorbunov method. Mineralogical analysis were carried out by universal X-ray diffractometer (Carl Zeiss Jena, Germany). The dominant fraction is a coarse silt fraction, the sand fraction content is negligible. The soil is characterized by medium-textured loam composition from the above and a sandy loam composition in the bottom. Textural differentiation occured due to the distribution of clay fraction. The content of this fraction in plough horizons varies depending on addition of part of other horizons during plowing. The plogh-layer of the residual-carbonate agrogrey soil is characterized by higher (20-23 %) amount of fraction less than 1 mkm, in comparison with plough horizon above the second humus horizon (SHH ), where the amount of silt is 15-16 %. The main components of the fraction derived from the rock are complex mixed- lattice formations dominated by mica - smectite with a high proportion of smectite packages, mica - smectites with low content of smectite packages were in subordinate quantity. The next component is hydromica - a mixture of dioctahedral and trioctahedral varieties. Smectite phase and hydromica add up to 85-90 % of the silt component. The amount of kaolinite and chlorite usually range in 7-13 %. Kaolinite is generally imperfect, chlorite is magnesia-ferric. The presence of fine quartz and feldspars (less amount) is revealed. During the soil formation the redistribution of the above minerals whose behavior is caused by the type of soil is occurring. Agrogrey heavy-textured soils are characterized by textural differentiation of the profile. The main carrier of this differentiation is the silt fraction, mainly its component - the swelling phase. Smectite phase dominates in silt fraction and it is eluvially distributed within the soil profile. Silty fraction of loess loam contains 72 % of the smectite phase. Behavior of minerals constituting the sum of kaolinite and chlorite content indicates its relatively uniform distribution. A slight increase in their content is noted in the eluvial part of the profile, mainly due to increasing in the proportion of kaolinite. The amount of hydromica reduces down the profile from 44.2 % to 19.8% in loess loam (soil-forming rock). The ratio of dioctahedral structures of hydromica to trioctahedral changes within the soil profile: trioctahedral varieties are more abundant in the upper part of the profile.

  9. Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions

    PubMed Central

    Lan, Yeqing; Deng, Baolin; Kim, Chulsung; Thornton, Edward C

    2007-01-01

    The effects of soil minerals on chromate (CrVIO42-, noted as Cr(VI)) reduction by sulfide were investigated in the pH range of 7.67 to 9.07 under the anoxic condition. The examined minerals included montmorillonite (Swy-2), illite (IMt-2), kaolinite (KGa-2), aluminum oxide (?-Al2O3), titanium oxide (TiO2, P-25, primarily anatase), and silica (SiO2). Based on their effects on Cr(VI) reduction, these minerals were categorized into three groups: (i) minerals catalyzing Cr(VI) reduction illite; (ii) minerals with no effect Al2O3; and (iii) minerals inhibiting Cr(VI) reduction- kaolinite, montmorillonite, SiO2 and TiO2 . The catalysis of illite was attributed primarily to the low concentration of iron solubilized from the mineral, which could accelerate Cr(VI) reduction by shuttling electrons from sulfide to Cr(VI). Additionally, elemental sulfur produced as the primary product of sulfide oxidation could further catalyze Cr(VI) reduction in the heterogeneous system. Previous studies have shown that adsorption of sulfide onto elemental sulfur nanoparticles could greatly increase sulfide reactivity towards Cr(VI) reduction. Consequently, the observed rate constant, kobs, increased with increasing amounts of both iron solubilized from illite and elemental sulfur produced during the reaction. The catalysis of iron, however, was found to be blocked by phenanthroline, a strong complexing agent for ferrous iron. In this case, the overall reaction rate at the initial stage of reaction was pseudo first order with respect to Cr(VI), i.e., the reaction kinetics was similar to that in the homogeneous system, because elemental sulfur exerted no effect at the initial stage prior to accumulation of elemental sulfur nanoparticles. In the suspension of kaolinite, which belonged to group (iii), an inhibitive effect to Cr(VI) reduction was observed and subsequently examined in more details. The inhibition was due to the sorption of elemental sulfur onto kaolinite, which reduced or completely eliminated the catalytic effect of elemental sulfur, depending on kaolinite concentration. This was consistent with the observation that the catalysis of externally added elemental sulfur (50 ?M) on Cr(VI) reduction would disappear with a kaolinite concentration of more than 5.0 g/L. In kaolinite suspension, the overall reaction rate law was: -d[Cr(VI)]/dt = kobs[H+]2[Cr(VI)][HS-]0.70 PMID:17430591

  10. Extraction Pattern of Arsenic Species with Mineral Composition in Contaminated Soils in Korea

    NASA Astrophysics Data System (ADS)

    Park, M.; Shin, M.; Yoon, H.; Kim, Y.; Kim, K.; Ko, I.

    2006-12-01

    Specific determination of various arsenic species is gaining increasing attention because the toxicity of arsenic differs with chemical forms such as organic (MMA, DMA) or inorganic (arsenite, arsenate). Knowledge of extraction method for arsenic speciation in contaminated soils then notified and tested by many researchers. However, the analytical technique for separation of different arsenic species has been always challenging in different environmental samples. A achieving correct analytical results and resolving the lowest detection limit is also desirable. Extraction method for arsenic speciation have been studied by many researchers with the use of a variety of extractants such as H3PO4, HCl, Na2CO3, EDTA 'in soils and sediments including plenty of clay. We, in this study, reported a benign extraction method and presented the pattern of arsenic in contaminated soils of different mineral compositions. Soil samples were collected from tailings of 2 places (Kyungbuk, Jeonnam); both were from abandoned metal mines in Korea. Samples were air dried at room temperature and separated by mechanical sieving to three fractions (2mm_200 ?m, 200_64?m, <64?m). Prepared samples were examined for total arsenic analysis used by KBSI method and modified Garcia-Manyes method for arsenic speciation. We extracted arsenic species from the soils by using a mixture of 1M phosphoric acid and 0.1% ascorbic acid. 0.2g of sample was placed in microwave digestion vessels along with 10ml extraction solution and treated for 15min at 60w microwave power. After the microwave stage, the contents were transferred to 30ml sample bottles and diluted to 16ml with deionized water, then centrifuged for 15min at 2500rpm. Total arsenic concentration of sample was analyzed by using ICP-AES (ICP-OES, Ultima2C, Jobin Yvon) and the arsenic species were analyzed by hyphenated system, SPE-HG-ICP-AES. To identify the mineral phases in bulk soil samples, we used XRD (Phillips X'Pert MPD) under 40kV/30mA condition. XRD data was collected between 5 and 70 2theta values using CuK? target.

  11. Mineralization of Soil Organic Matter in Two Elevated CO2 by Warming Experiments in Grassland

    NASA Astrophysics Data System (ADS)

    Pendall, E.; Hovenden, M.; Williams, A.; Dijkstra, F. A.; Morgan, J. A.

    2007-12-01

    Experimentally elevated atmospheric CO2 has enhanced carbon (C) allocation belowground, while ecosystem warming has led to losses of soil C due to enhanced mineralization of soil organic matter (SOM). Few investigations of possible interactions between elevated CO2 and temperature have been reported, but the potential for C cycling effects not to be simply additive is high. We have taken advantage of two multi-factor global change experiments being conducted in mixed C3/C4 grasslands to evaluate similarities and differences in responses of SOM mineralization rates. The TasFACE experiment in Tasmania, Australia, has been running for over 5 years, while the Prairie Heating and CO2 Enrichment (PHACE) experiment in Wyoming, USA, has been running for less than 2 years. Both experiments employ mini-FACE systems (enriched plots targeted at 550 at TasFACE and 600 ppm at PHACE) and overhead ceramic infrared emitters (heated plots targeted at +2 degrees C at TasFACE and +1.5/+3 degrees day/night at PHACE). Soil samples collected after 5 years at TasFACE and at the beginning of the second year at PHACE were incubated for three weeks to evaluate changes in labile SOM pool sizes and turnover rates. We hypothesized that elevated CO2 would enhance labile SOM pool size and that warming would reduce it, and that warming would stimulate decomposition rate. Preliminary results suggested that five years of warming enhanced decomposition rate in the TasFACE soils, but only under the C4 grass species, whereas the first two months of warming had no effects on decomposition rate at PHACE. Elevated CO2 increased mineralizable C pool sizes by 10 to 30 percent, depending on depth, in the TasFACE soils, but did not significantly alter C cycling in the PHACE soils. Short experimental duration likely explained the lack of treatment effects seen at PHACE. We plan to continue conducting parallel experiments to track temporal changes in C cycling with the expectation that interactive effects of elevated CO2 and warming may appear over the long term.

  12. The use of volcanic soil as mineral landfill liner--I. Physicochemical characterization and comparison with zeolites.

    PubMed

    Navia, Rodrigo; Hafner, Georg; Raber, Georg; Lorber, Karl E; Schöffmann, Elke; Vortisch, Walter

    2005-06-01

    The main physicochemical characteristics of the volcanic soil of Southern Chile, with allophane as the main pedogenic mineral phase were analysed and compared with common zeolites (clinoptilolite) of the European market. The ultimate goal of this study was to test volcanic soil for the use as mineral landfill liner. The main results indicated that the clay and silt fractions together of the volcanic soil were between 38 and 54%. The buffering capacity of the volcanic soil was higher compared with the studied zeolites, whereas the cationic exchange capacity of the volcanic soil (between 5.2 and 6.5 cmol + kg(-1)) is of the same order of magnitude of the studied zeolites (between 9.7 and 11.4 cmol + kg(-1)). Moreover, the anionic exchange capacity of the volcanic soil was higher compared to the zeolites analysed. The hydraulic conductivity of the volcanic soil, measured in the laboratory at maximum proctor density, ranges between 5.16 x 10(-9) and 6.48 x 10(-9) m s(-1), a range that is comparable to the value of 4.51 x 10(-9) m s(-1) of the studied zeolite. The Proctor densities of the volcanic soil are in a lower range (between 1.11 and 1.15 g ml(-1)) compared with zeolites (between 1.19 and 1.34 g ml(-1)). The volcanic soil physicochemical characteristics are comparable to all the requirements established in the Austrian landfill directive (DVO, 2000). Therefore, the use as mineral landfill basal sealing of the analysed volcanic soil appears reasonable, having a pollutant adsorption capacity comparable to zeolites. It is of special interest for Southern Chile, because there are no alternative mineral raw materials for basal liners of landfills. PMID:15988944

  13. Long-term fertilization of a boreal Norway spruce forest increases the temperature sensitivity of soil organic carbon mineralization

    PubMed Central

    Coucheney, Elsa; Strmgren, 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

  14. Banana leaf and glucose mineralization and soil organic matter in microhabitats of banana plantations under long-term pesticide use.

    PubMed

    Blume, Elena; Reichert, Jos Miguel

    2015-06-01

    Soil organic matter (SOM) and microbial activity are key components of soil quality and sustainability. In the humid tropics of Costa Rica 3 pesticide regimes were studied-fungicide (low input); fungicide and herbicide (medium input); and fungicide, herbicide, and nematicide (high input)-under continuous banana cultivation for 5 yr (young) or 20 yr (old) in 3 microhabitats-nematicide ring around plants, litter pile of harvested banana, and bare area between litter pile and nematicide ring. Soil samples were incubated sequentially in the laboratory: unamended, amended with glucose, and amended with ground banana leaves. Soil organic matter varied with microhabitat, being greatest in the litter pile, where microbes had the greatest basal respiration with ground banana leaf, whereas microbes in the nematicide ring had the greatest respiration with glucose. These results suggest that soil microbes adapt to specific microhabitats. Young banana plantations had similar SOM compared with old plantations, but the former had greater basal microbial respiration in unamended and in glucose-amended soil and greater first-order mineralization rates in glucose-amended soil, thus indicating soil biological quality decline over time. High pesticide input did not decrease microbial activity or mineralization rate in surface soil. In conclusion, microbial activity in tropical volcanic soil is highly adaptable to organic and inorganic inputs. PMID:25703385

  15. 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

  16. Application of calcium carbonate slows down organic amendments mineralization in reclaimed soils

    NASA Astrophysics Data System (ADS)

    Zornoza, Ral; Faz, ngel; Acosta, Jos A.; Martnez-Martnez, Silvia; ngeles Muoz, M.

    2014-05-01

    A field experiment was set up in Cartagena-La Unin Mining District, SE Spain, aimed at evaluating the short-term effects of pig slurry (PS) amendment alone and together with marble waste (MW) on organic matter mineralization, microbial activity and stabilization of heavy metals in two tailing ponds. These structures pose environmental risk owing to high metals contents, low organic matter and nutrients, and null vegetation. Carbon mineralization, exchangeable metals and microbiological properties were monitored during 67 days. The application of amendments led to a rapid decrease of exchangeable metals concentrations, except for Cu, with decreases up to 98%, 75% and 97% for Cd, Pb and Zn, respectively. The combined addition of MW+PS was the treatment with greater reduction in metals concentrations. The addition of PS caused a significant increase in respiration rates, although in MW+PS plots respiration was lower than in PS plots. The mineralised C from the pig slurry was low, approximately 25-30% and 4-12% for PS and MW+PS treatments, respectively. Soluble carbon (Csol), microbial biomass carbon (MBC) and ?-galactosidase and ?-glucosidase activities increased after the application of the organic amendment. However, after 3 days these parameters started a decreasing trend reaching similar values than control from approximately day 25 for Csol and MBC. The PS treatment promoted highest values in enzyme activities, which remained high upon time. Arylesterase activity increased in the MW+PS treatment. Thus, the remediation techniques used improved soil microbiological status and reduced metal availability. The combined application of PS+MW reduced the degradability of the organic compounds. Keywords: organic wastes, mine soils stabilization, carbon mineralization, microbial activity.

  17. Soil Mineral Composition Matters: Response of Microbial Communities to Phenanthrene and Plant Litter Addition in Long-Term Matured Artificial Soils

    PubMed Central

    Babin, Doreen; Vogel, Cordula; Zühlke, Sebastian; Schloter, Michael; Pronk, Geertje Johanna; Heister, Katja; Spiteller, Michael; Kögel-Knabner, Ingrid; Smalla, Kornelia

    2014-01-01

    The fate of polycyclic aromatic hydrocarbons (PAHs) in soil is determined by a suite of biotic and abiotic factors, and disentangling their role in the complex soil interaction network remains challenging. Here, we investigate the influence of soil composition on the microbial community structure and its response to the spiked model PAH compound phenanthrene and plant litter. We used long-term matured artificial soils differing in type of clay mineral (illite, montmorillonite) and presence of charcoal or ferrihydrite. The soils received an identical soil microbial fraction and were incubated for more than two years with two sterile manure additions. The matured artificial soils and a natural soil were subjected to the following spiking treatments: (I) phenanthrene, (II) litter, (III) litter + phenanthrene, (IV) unspiked control. Total community DNA was extracted from soil sampled on the day of spiking, 7, 21, and 63 days after spiking. Bacterial 16S rRNA gene and fungal internal transcribed spacer amplicons were quantified by qPCR and subjected to denaturing gradient gel electrophoresis (DGGE). DGGE analysis revealed that the bacterial community composition, which was strongly shaped by clay minerals after more than two years of incubation, changed in response to spiked phenanthrene and added litter. DGGE and qPCR showed that soil composition significantly influenced the microbial response to spiking. While fungal communities responded only in presence of litter to phenanthrene spiking, the response of the bacterial communities to phenanthrene was less pronounced when litter was present. Interestingly, microbial communities in all artificial soils were more strongly affected by spiking than in the natural soil, which might indicate the importance of higher microbial diversity to compensate perturbations. This study showed the influence of soil composition on the microbiota and their response to phenanthrene and litter, which may increase our understanding of complex interactions in soils for bioremediation applications. PMID:25222697

  18. Tracking rainfall variations in the late Pleistocene using U isotopes in dated secondary soil minerals

    NASA Astrophysics Data System (ADS)

    Ibarra, D. E.; Oster, J. L.; Maher, K.

    2011-12-01

    Past changes in rainfall are an important indicator of variations in atmospheric circulation. However, there are very few approaches that are uniquely sensitive to past changes in rainfall and use common materials that can be accurately dated. Secondary minerals in arid soils form directly from rainfall and can precipitate continuously over hundreds of thousands of years. Previous studies have used stable isotope measurements of soil carbonates to look at a variety of processes such as precipitation source and amount, evaporation, temperature, and vegetation. Often, the challenge with stable isotope approaches is to distinguish between these factors. In addition, stable isotope studies have not traditionally used high-resolution analytical techniques to capture the temporal variations within a given sample. The development of alternative isotopic systems that more directly reflect rainfall would provide a complimentary tool to more traditional strategies. In order to evaluate whether widely observed variations in the calculated initial U isotopic composition of dated soil minerals (e.g. (234U/238U)0) reflect changes in past rainfall, we sampled modern soil pore waters, soils and dust from a rainfall gradient in Fish Lake Valley, NV. In situ ion microprobe (SHRIMP-RG) techniques were used to determine the 230Th-U ages and (234U/238U)0 from uranium-rich soil opal collected at three field sites in western North America. Modern pore waters in desert soils from Fish Lake Valley, NV show systematic decreases in (234U/238U) with increasing rainfall. This is attributed to increasing infiltration flux and chemical weathering at higher rainfall rates, as the eolian influence should likely remain the same across the rainfall gradient. Although changes in the uranium concentration and isotopic composition of dust through time may also influence the (234U/238U) of soil water, these changes are likely minimal relative to changes in infiltration flux. The variations in (234U/238U)0 obtained from 230Th-U dating of soil opal span approximately the last 5-60 kyrs. Based on the modern pore water data, we interpret low (234U/238U)0 to indicate periods of higher rainfall, and high (234U/238U)0 to indicate periods of reduced rainfall. We observe nearly synchronous shifts during the last glacial-interglacial transition along the latitudinal transect of our field sites. Our initial results show that the transition from MIS 3 to 2 was likely characterized by increasing precipitation, with peak rainfall at the beginning of MIS 2. This corresponds to generally decreasing SST off of the California coast and rainier periods in speleothem records from the southwestern United States. Additionally (234U/238U)0 from our soil opal records co-varies with fluctuations in lake levels of large pluvial lake systems in western North America. The synchronous signal of increased rainfall during MIS 2 is consistent with a southward-shift in westerly storm tracks at the LGM. Our approach demonstrates an alternative method for increasing the spatial coverage and chronology of climate records in arid regions.

  19. Mineral cycling in soil and litter arthropod food chains. Annual progress report, February 1, 1983-January 31, 1984

    SciTech Connect

    Crossley, D.A. Jr.

    1983-09-30

    This annual report describes progress in research on the influence of soil fauna on the general process of terrestrial decomposition. The major goal is to investigate the regulation of decomposition by soil arthropods. Methods have included radioactive tracer measurements of food chain dynamics, rates of nutrient or mineral element flow during decomposition, and simulation modeling. This year's report describes significant progress in defining the influence of soil arthropods in stimulating microbial immobilization of nutrients. Preliminary efforts to define the importance of the soil-litter macroarthropods are also reported.

  20. Stable isotopes of carbon dioxide in soil gas over massive sulfide mineralization at Crandon, Wisconsin

    USGS Publications Warehouse

    Alpers, C.N.; Dettman, D.L.; Lohmann, K.C.; Brabec, D.

    1990-01-01

    Stable isotope ratios of oxygen and carbon were determined for CO2 in soil gas in the vicinity of the massive sulfide deposit at Crandon, Wisconsin with the objective of determining the source of anomalously high CO2 concentrations detected previously by McCarthy et al. (1986). Values of ??13C in soil gas CO2 from depths between 0.5 and 1.0 m were found to range from -12.68??? to -20.03??? (PDB). Organic carbon from the uppermost meter of soil has ??13C between -24.1 and -25.8??? (PDB), indicating derivation from plant species with the C3 (Calvin) type of photosynthetic pathway. Microbial decomposition of the organic carbon and root respiration from C3 and C4 (Hatch-Slack) plants, together with atmospheric CO2 are the likely sources of carbon in soil gas CO2. Values of ??18O in soil-gas CO2 range from 32 to 38??? (SMOW). These ??18O values are intermediate between that calculated for CO2 gas in isotopic equilibrium with local groundwaters and that for atmospheric CO2. The ??18O data indicate that atmospheric CO2 has been incorporated by mixing or diffusion. Any CO2 generated by microbial oxidation of organic matter has equilibrated its oxygen isotopes with the local groundwaters. The isotopic composition of soil-gas CO2 taken from directly above the massive sulfide deposit was not distinguishable from that of background samples taken 1 to 2 km away. No enrichment of the ??13C value of soil-gas CO2 was observed, contrary to what would be expected if the anomalous CO2 were derived from the dissolution of Proterozoic marine limestone country rock or of Paleozoic limestone clasts in glacial till. Therefore, it is inferred that root respiration and decay of C3 plant material were responsible for most CO2 generation both in the vicinity of the massive sulfide and in the "background" area, on the occasion of our sampling. Interpretation of our data is complicated by the effects of rainfall, which significantly reduced the magnitude of the CO2 anomaly. Therefore, we cannot rule out the possible mechanism of carbonate dissolution driven by pyrite oxidation, as proposed by Lovell et al. (1983) and McCarthy et al. (1986). Further work is needed on seasonal and daily variations of CO2 concentrations and stable isotope ratios in various hydrogeologic and ecologic settings so that more effective sampling strategies can be developed for mineral exploration using soil gases. ?? 1990.

  1. Does temperature of charcoal creation affect subsequent mineralization of soil carbon and nitrogen?

    NASA Astrophysics Data System (ADS)

    Pelletier-Bergeron, S.; Bradley, R.; Munson, A. D.

    2012-04-01

    Forest fire is the most common form of natural disturbance of boreal forest ecosystems and has primordial influence on successional processes. This may be due in part to the pre-disturbance vegetation development stage and species composition, but these successional pathways could also vary with differences in fire behavior and consequently in fire intensity, defined as the energy released during various phases of a fire. Fire intensity may also affect soil C and N cycling by affecting the quality of the charcoal that is produced. For example, the porosity of coal tends to increase with increasing temperature at which it is produced Higher porosity would logically increase the surface area to which dissolved soil molecules, such as tannins and other phenolics, may be adsorbed. We report on a microcosm study in which mineral and organic soils were jointly incubated for eight weeks with a full factorial array of treatments that included the addition of Kalmia tannins, protein, and wood charcoal produced at five different temperatures. A fourth experimental factor comprised the physical arrangement of the material (stratified vs. mixed), designed to simulate the effect of soil scarification after fire and salvage harvest. We examined the effects of these treatments on soil C and N mineralisation and soil microbial biomass. The furnace temperature at which the charcoal was produced had a significant effect on its physico-chemical properties; increasing furnace temperatures corresponded to a significant increase in % C (P<0.001), and a significant decrease in %O (P<0.001) and %H (P<0.001). Temperature also had significant impacts on microporosity (surface area and volume). Temperature of production had no effect (P=0.1355) on soil microbial biomass. We observed a linear decreasing trend (P<0.001) in qCO2 with increasing temperature of production, which was mainly reflected in a decline in basal respiration. Finally, we found a significant interaction (P=0.010) between temperature of charcoal production x soil mixing in controlling post incubation NH4+ concentrations. We discuss the results in relation to potential implications for changing fire regime and C and N cycles.

  2. Substrate quality alters the microbial mineralization of added substrate and soil organic carbon

    NASA Astrophysics Data System (ADS)

    Jagadamma, S.; Mayes, M. A.; Steinweg, J. M.; Schaeffer, S. M.

    2014-09-01

    The rate and extent of decomposition of soil organic carbon (SOC) is dependent, among other factors, on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial decomposition of carbon (C), and to use model fitting to quantify differences in pool sizes and mineralization rates. We conducted an incubation experiment for 270 days using four uniformly labeled 14C substrates (glucose, starch, cinnamic acid and stearic acid) on four different soils (a temperate Mollisol, a tropical Ultisol, a sub-arctic Andisol, and an arctic Gelisol). The 14C labeling enabled us to separate CO2 respired from added substrates and from native SOC. Microbial gene copy numbers were quantified at days 4, 30 and 270 using quantitative polymerase chain reaction (qPCR). Substrate C respiration was always higher for glucose than other substrates. Soils with cinnamic and stearic acid lost more native SOC than glucose- and starch-amended soils. Cinnamic and stearic acid amendments also exhibited higher fungal gene copy numbers at the end of incubation compared to unamended soils. We found that 270 days were sufficient to model the decomposition of simple substrates (glucose and starch) with three pools, but were insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality exerts considerable control on the microbial decomposition of newly added and native SOC, and demonstrates the need for multi-year incubation experiments to constrain decomposition parameters for the most recalcitrant fractions of SOC and complex substrates.

  3. Potential for Rapid Physical Protection of Wood and Pyrolyzed Carbon in the Mineral Soil Matrix: Effects of Soil Type, Depth, and Temperature

    NASA Astrophysics Data System (ADS)

    Castanha, C.; Tas, N.; Reichl, K.; Jansson, J. K.; Brodie, E. L.; Fischer, M. L.; Torn, M. S.

    2012-12-01

    To determine how soil type, depth, and temperature affect the stabilization of biochar and wood in soils, we conducted an incubation study using soils from a moist tropical forest in Tabonuco, Puerto Rico and from a Mediterranean grassland in Hopland, California, collected from surface and from deep horizons. To these four soil types we added ground 13C-labeled biochar (or the wood from which it was derived) and incubated at ambient (14 °C for the Hopland and 20 °C for the Tabonuco soil) and elevated (ambient +6 °C) temperatures at field gravimetric moisture content (20% for Hopland and 80% for Tabonuco) for 13 months. Preliminary analysis of the 13CO2 evolution from these soils indicates that wood was mineralized faster than biochar. Differences in the matrix of the soils - greater clay and iron oxide content in the Tabonuco Oxisol than in the Hopland Ultisol, but also greater clay and iron oxide content in the deep compared to the surface Hopland soil - lead to the expectation that the potential for physical protection of organic carbon substrates from mineralization is greater in the tropical soils and also greater in the deeper horizons. Here we present results from 13C analyses of density fractionations conducted on the soils after they incubated for 13 months, and thereby quantify the extent to which the introduced 13C was mobilized from the free particulate fraction, where it was added, to the intra-aggregate particulate fraction and the mineral-associated fraction. Our results will enable better predictions of the environmental conditions under which biochar (and wood) is more likely to contribute to stable soil carbon pools.

  4. Carbon mineralization of flooded boreal soil and vegetation under different temperature and oxygen conditions

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Ullah, S.; Roulet, N.; Moore, T.

    2009-05-01

    Flooding of terrestrial ecosystems significantly alters carbon (C) mineralization rates, which results in increasing emissions of carbon dioxide (CO2) and methane (CH4). To better understand the changes after water impoundment, C mineralization under flooded conditions needs to be investigated. This study investigates CO2 and CH4 fluxes from flooded boreal soil and vegetation, compares them to the fluxes of non- flooded treatment, and examines how environmental factors affect the fluxes. We conducted short-term in vitro experiments using boreal forest soil (FH layer), peat soil (0 to 5 and 5 to 15 cm) layer, and black spruce needles and small twigs, and shrub, sedge, lichen, and moss tissues. Flooded samples were incubated in 1- L Mason jars without light, under three temperatures (5, 12, and 24degC) and 0 and 50 percent of ambient oxygen (O2) concentration, and non-flooded ones were incubated in 1-L plastic containers under same light and temperature conditions to those of flooded samples and ambient oxygen concentration. We collected gas samples after flushing with nitrogen gas and air, and the fluxes of CO2 and CH4 were determined by gas chromatography. The average CO2 and CH4 fluxes in all materials were 200 and 0.8 microgram C/g organic matter/day, with smaller CO2 fluxes and larger CH4 fluxes than the fluxes of non-flooding (CO2 and CH4: 370 and 0.2 microgram C/g organic matter/day). Among the flooded samples, forest and peatland ground vegetation showed much high CO2 fluxes, and peat soils released more CH4 than other materials. Higher temperatures increased emissions of both CO2 and CH4, and the lower O2 concentration increased CH4 emissions. These results suggest the flooded vegetation and peat soil largely contribute to the total C emission in the flooded ecosystem and that spatial and temporal variability in CO2 and CH4 emissions can be related to substrate type, temperature and O2 concentration.

  5. Nitrogen mineralization and transformation from composts and biosolids during field incubation in a sandy soil

    SciTech Connect

    He, Z.L.; Alva, A.K.; Yan, P.; Li, Y.C.; Calvert, D.V.; Stoffella, P.J.; Banks, D.J.

    2000-02-01

    Field evaluation of nutrient release from composts is important to estimate nutrient contribution to crops, potential leaching of nutrients, and, ultimately, to determine optimum application rates, timing, and placement of composts. Field incubation and laboratory analyses were conducted to evaluate the mineralization rate and transformation of N in biosolids (BSD), yard waste (YW), and West Palm Beach co-compost (WPCC). Each of the composts or biosolids was packed into PVC columns and inserted vertically into the upper layer of an Oldsmar fine sand of raised citrus beds. The top end of the PVC column was capped to prevent excessive leaching of nutrients from the columns. The moisture equilibrium between the incubated sample and the soil in the field was attained through the bottom and four side holes of each column, which were separated from the contacting soil by 400-mesh nylon screen. A set of the incubated columns was removed at monthly intervals, and the soil underlying each column was sampled to analyze for KCl-extractable NH{sub 4}-N and NO{sub 3}-N. Total C and N of the incubated samples were determined at the end of the 1-year incubation.

  6. Characterization of mineral phosphate solubilization traits from a barley rhizosphere soil functional metagenome

    PubMed Central

    Chhabra, Sagar; Brazil, Dina; Morrissey, John; Burke, James I; O'Gara, Fergal; N Dowling, David

    2013-01-01

    Mineral phosphate solubilization (MPS) microorganisms are important for their provision of orthophosphate anions for plant growth promotion activity in soil. In this study, we applied a functional metagenomic approach to identify this trait directly from the microbiome in barley rhizosphere soil that had not received P fertilizer over a 15-year period. A fosmid system was used to clone the metagenome of which 18,000 clones (∼666 Mb of DNA) was screened for MPS. Functional assays and High Performance Liquid Chromatography analysis recognized gluconic acid production and MPS activity in the range 24.8–77.1 mmol/L and 27.6–38.16 μg/mL, respectively, when screened in an Escherichia coli host (at frequency of one MPS-positive clone hit per 114 Mb DNA tested). The MPS clones (with average insert size of ∼37 kb) were analysed by 454 Roche sequencing and annotated. A number of genes/operons with homology to Phosphorous (P) uptake, regulatory and solubilization mechanisms were identified, linking the MPS function to the uncultivated microbiome present in barley rhizosphere soil. PMID:23894099

  7. Characterization of mineral phosphate solubilization traits from a barley rhizosphere soil functional metagenome.

    PubMed

    Chhabra, Sagar; Brazil, Dina; Morrissey, John; Burke, James I; O'Gara, Fergal; N Dowling, David

    2013-10-01

    Mineral phosphate solubilization (MPS) microorganisms are important for their provision of orthophosphate anions for plant growth promotion activity in soil. In this study, we applied a functional metagenomic approach to identify this trait directly from the microbiome in barley rhizosphere soil that had not received P fertilizer over a 15-year period. A fosmid system was used to clone the metagenome of which 18,000 clones (~666 Mb of DNA) was screened for MPS. Functional assays and High Performance Liquid Chromatography analysis recognized gluconic acid production and MPS activity in the range 24.8-77.1 mmol/L and 27.6-38.16 ?g/mL, respectively, when screened in an Escherichia coli host (at frequency of one MPS-positive clone hit per 114 Mb DNA tested). The MPS clones (with average insert size of ~37 kb) were analysed by 454 Roche sequencing and annotated. A number of genes/operons with homology to Phosphorous (P) uptake, regulatory and solubilization mechanisms were identified, linking the MPS function to the uncultivated microbiome present in barley rhizosphere soil. PMID:23894099

  8. Applications of PIXE to mineral characterization

    NASA Astrophysics Data System (ADS)

    Wilson, Graham C.; Rucklidge, John C.; Campbell, John L.; Nejedly, Zdenek; Teesdale, William J.

    2002-04-01

    This article illustrates the application of the proton-induced X-ray emission (PIXE) technique to detailed documentation of mineral assemblages, with emphasis on base-metal ores. Some of the investigations aided by the PIXE laboratory at Guelph since 1993 include determinations of the distribution of minor and trace elements in magmatic Ni-Cu ores, volcanogenic massive sulphide Cu-Pb-Zn-(Ag-Au) ores and lode Au-(Ag) deposits. Minor elements of importance include possible by-products or co-products of metal refining, as well as deleterious impurities in mill-feed, e.g. Cd, In, Sn, As, Se, Te, Tl and Hg. Weathering products of primary sulphide mineralization, including tropical laterites and other oxidized assemblages, have been analysed successfully and can contain a wide range of minor elements which reflect the bedrock style of mineralization. The iron oxyhydroxide goethite, ?-FeO(OH), contains trace levels of many elements, and in some cases 1 wt.% or more of base metals and arsenic, elements which are invisible in reflected-light microscopy. Other metals such as Ag are of sporadic occurrence in oxidized ores: they may be found as discrete mineral species, not incorporated into the dominant oxyhydroxides. A summary of findings from three base-metal deposits in Canada, the Philippines and Portugal serves to illustrate the manner in which PIXE data benefit our knowledge of metal distributions in metallic ores. PIXE can contribute to several facets of mineral-deposit research, such as: (1) the development of ore textures, and specifically the distribution of elements within zoned crystals, or between multiple generations of a particular mineral; (2) the location of precious metals, Ag being in general the simplest case; and (3) pinpointing elements that may have implications for ore genesis, environmental quality or metal refining, such as Cr, As and Se.

  9. Interactive control of minerals, wildfire, and erosion on soil carbon stabilization in conifer ecosystems of the western U.S.

    NASA Astrophysics Data System (ADS)

    Rasmussen, C.

    2014-12-01

    Answering the question of what controls the fate and stabilization of organic carbon in forest soils is central to understanding the role of western US ecosystems in mitigating climate change, optimizing forest management, and quantifying local and regional terrestrial carbon budgets. Over half of forest soil C is stored belowground, stabilized by a number of separate, but interacting physical, chemical and biological mechanisms. Here we synthesize data from a series of field and laboratory studies focused on identifying mineral, physical, and landscape position controls on belowground C stabilization mechanisms in western U.S. conifer ecosystems. Results from these studies demonstrate an important for role for short-range-order Fe- and Al-oxyhydroxides and Al-humus complexes in C stabilization, and that the soil mineral assemblage moderates C cycling via control on partitioning of C into physical fractions ("free", "occluded", "mineral") with varying MRT and chemistry. Measures of occluded fraction chemical composition by 13C-NMR indicate this fraction is 2-5 times more enriched in pyrogenic C than the bulk soil and that this fraction is on the order of ~25 to 65% charred materials. Radiocarbon analyses of a large set of conifer soil samples from California and Arizona further indicate the occluded fraction is generally older than either the free light or mineral fraction. In particular, soil C in convergent, water and sediment gathering portions of the landscape are enriched in long MRT charred materials. These results indicate an important role for the interaction of soil mineral assemblage, wildfire, and erosion in controlling belowground C storage and stabilization in western conifer forests. Drought and wildfire are expected to increase with climate change and thus may exert significant control on belowground C storage directly through biochemical and physical changes in aboveground biomass, production of charred materials, and indirectly via post-fire physical erosion and redistribution of C-rich sediment across the landscape.

  10. Long Term Effect of Land Reclamation from Lake on Chemical Composition of Soil Organic Matter and Its Mineralization

    PubMed Central

    He, Dongmei; Ruan, Honghua

    2014-01-01

    Since the late 1950s, land reclamation from lakes has been a common human disturbance to ecosystems in China. It has greatly diminished the lake area, and altered natural ecological succession. However, little is known about its impact on the carbon (C) cycle. We conducted an experiment to examine the variations of chemical properties of dissolved organic matter (DOM) and C mineralization under four land uses, i.e. coniferous forest (CF), evergreen broadleaf forest (EBF), bamboo forest (BF) and cropland (CL) in a reclaimed land area from Taihu Lake. Soils and lake sediments (LS) were incubated for 360 days in the laboratory and the CO2 evolution from each soil during the incubation was fit to a double exponential model. The DOM was analyzed at the beginning and end of the incubation using UV and fluorescence spectroscopy to understand the relationships between DOM chemistry and C mineralization. The C mineralization in our study was influenced by the land use with different vegetation and management. The greatest cumulative CO2-C emission was observed in BF soil at 0–10 cm depth. The active C pool in EBF at 10–25 cm had longer (62 days) mean residence time (MRT). LS showed the highest cumulative CO2-C and shortest MRT comparing with the terrestrial soils. The carbohydrates in DOM were positively correlated with CO2-C evolution and negatively correlated to phenols in the forest soils. Cropland was consistently an outlier in relationships between DOM chemistry and CO2-evolution, highlighting the unique effects that this land use on soil C cycling, which may be attributed the tillage practices. Our results suggest that C mineralization is closely related to the chemical composition of DOM and sensitive to its variation. Conversion of an aquatic ecosystem into a terrestrial ecosystem may alter the chemical structure of DOM, and then influences soil C mineralization. PMID:24905998

  11. Local coordination of Zn in hydroxy-interlayered minerals and implications for Zn retention in soils

    NASA Astrophysics Data System (ADS)

    Jacquat, Olivier; Voegelin, Andreas; Kretzschmar, Ruben

    2009-01-01

    The objective of this study was to determine the local coordination of Zn in hydroxy-interlayered smectite (HIS) as a function of Zn loading and synthesis conditions and to assess the importance of hydroxy-interlayered minerals (HIM) for Zn retention in contaminated soils. Published and newly collected extended X-ray absorption fine structure (EXAFS) spectra of HIS reacted with Zn at molar Zn/hydroxy-Al ratios from 0.013 to 0.087 (corresponding to final Zn contents of 1615-8600 mg/kg Zn) were evaluated by shell fitting. In Zn-HIS, Zn was octahedrally coordinated to oxygen at 2.06-2.08 and surrounded by Al atoms at 3.03-3.06 in the second-shell. With increasing molar Zn/hydroxy-Al ratio, the coordination number of second-shell Al decreased from 6.6 to 2.1. These results were interpreted as a progressive shift from Zn incorporation in the vacancies of gibbsitic Al-polymers to Zn adsorption to incomplete Al-polymers and finally uptake by cation exchange in the polymer-free interlayer space of HIS with increasing Zn loadings. In a second part, we determined the speciation of Zn in eight contaminated soils (251-1039 mg/kg Zn) with acidic to neutral pH (pH 4.1-6.9) using EXAFS spectroscopy. All soils contained hydroxy-Al interlayered vermiculite (HIV). The analysis of EXAFS spectra by linear combination fitting (LCF) showed that a substantial fraction of total Zn (29-84%) was contained in HIM with high Zn loading. The remaining Zn was adsorbed to organic and inorganic soil components and incorporated into phyllosilicates. In sequential extractions of Zn-HIS spiked into quartz powder and the Zn contaminated soils, Zn was mainly released in the two most resistant fractions, in qualitative agreement with the findings from LCF. Our results suggest that formation of Zn-HIM may strongly retain Zn in pristine and moderately contaminated acidic to neutral soils. Due to their limited sorption capacity, however, HIM do not allow for the accumulation of high levels of Zn in response to continued Zn input into soils.

  12. Linking soil element-mass-transfer to microscale mineral weathering in the Santa Catalina Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Lybrand, R. A.; Rasmussen, C.

    2012-12-01

    Soil chemical denudation and mineral transformation contributes significantly to landscape evolution and to our understanding of water and carbon cycling across ecosystems. The main objective of this research was to couple the chemical composition of bulk soils to the elemental changes associated with microscale mineral transformations to better understand climatic controls on soil development in semi-arid and sub-humid environments. Soil profiles to the depth of refusal and representative parent rock samples were collected from granitic terrain across the Santa Catalina Mountain Critical Zone observatory (SCM-CZO) environmental gradient that spans desert scrub to mixed conifer forest ecosystems. Bulk elemental chemistry, including major, minor, and trace elemental constituents, was determined by x-ray fluorescence (XRF) for all samples and microscale weathering patterns were quantified using electron microprobe analyses. From these data, elemental mass-transfer percentages were calculated and normalized to the parent rock materials using Na and Zr as the mobile and immobile inputs, respectively. Chemical depletions of Na, a proxy for plagioclase feldspar weathering, was observed in both the desert scrub and mixed conifer ecosystems. Na chemical loss was most consistent with depth and across soil pedons (n = 4) in the mixed conifer system where sodium depletion averaged 46% ( 5%) relative to the parent material, providing evidence for loss of plagioclase to chemical weathering. Electron microprobe analyses of surface and subsurface soils at the mixed conifer site revealed a significant decrease in sodium weight percent from the unaltered regions of the grains (Na of ~7-8%) to fully transformed areas of the grains (Na of ~0.2-0.3%) located in joint fractures and at grain edges. In contrast, soils from the desert scrub site exhibited highly variable Na loss in the bulk soils with Na depletion ranging from 23 to 50%. Electron microprobe analyses of desert scrub soils indicated incomplete mineral transformation where sodium weight percents spanned ~7% in un-altered grain centers to ~4% in grain fractures and edges. Backscattered electron (BSE) images support these patterns where more completely transformed minerals were observed in the mixed conifer soils compared to incomplete transformations in soils at the desert scrub site. These results document an important link between bulk soil element loss and microscale weathering processes with increased chemical denudation and mineral transformation in wetter, higher elevation mixed conifer ecosystems.

  13. Seasonal Soil Nitrogen Mineralization within an Integrated Crop and Livestock System in Western North Dakota, USA

    NASA Astrophysics Data System (ADS)

    Landblom, Douglas; Senturklu, Songul; Cihacek, Larry; Pfenning, Lauren; Brevik, Eric C.

    2015-04-01

    Protecting natural resources while maintaining or maximizing crop yield potential is of utmost importance for sustainable crop and livestock production systems. Since soil organic matter and its decomposition by soil organisms is at the very foundation of healthy productive soils, systems research at the North Dakota State University Dickinson Research Extension Center is evaluating seasonal soil nitrogen fertility within an integrated crop and livestock production system. The 5-year diverse crop rotation is: sunflower (SF) - hard red spring wheat (HRSW) - fall seeded winter triticale-hairy vetch (THV; spring harvested for hay)/spring seeded 7-species cover crop (CC) - Corn (C) (85-90 day var.) - field pea-barley intercrop (PBY). The HRSW and SF are harvested as cash crops and the PBY, C, and CC are harvested by grazing cattle. In the system, yearling beef steers graze the PBY and C before feedlot entry and after weaning, gestating beef cows graze the CC. Since rotation establishment, four crop years have been harvested from the crop rotation. All crops have been seeded using a JD 1590 no-till drill except C and SF. Corn and SF were planted using a JD 7000 no-till planter. The HRSW, PBY, and CC were seeded at a soil depth of 3.8 cm and a row width of 19.1 cm. Seed placement for the C and SF crops was at a soil depth of 5.1 cm and the row spacing was 0.762 m. The plant population goal/ha for C, SF, and wheat was 7,689, 50,587, and 7,244 p/ha, respectively. During the 3rd cropping year, soil bulk density was measured and during the 4th cropping year, seasonal nitrogen fertility was monitored throughout the growing season from June to October. Seasonal nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), total season mineral nitrogen (NO3-N + NH4-N), cropping system NO3-N, and bulk density were measured in 3 replicated non-fertilized field plot areas within each 10.6 ha triple replicated crop fields. Within each plot area, 6 - 20.3 cm x 0.61 m aluminum irrigation pipes were pressed into the soil as enclosures to restrict root access to soil nitrogen. Soil samples were taken as close to 2-week intervals as possible from both inside and outside the enclosures. The crop rotation N values were also compared to triple replicated perennial native grassland plot areas (predominate sp. Western wheatgrass - Pascopyrum smithii, Blue grama - Bouteloua gracilis, Little bluestem - Schizachyrium scoparium, Switchgrass - Panicum virgatum). Trends identified for both NH4-N and NO3-N indicate that the values are relatively similar with respect to seasonal change over time. There was a greater amount of soil nitrogen accumulation inside the enclosures indicating that outside the enclosures roots scavenge nitrogen for plant growth and production. Seasonally, comparing the cropping system crops, NO3-N declined mid-July and then rebounded by mid-August and continued to increase until leveling off in September. Corn NO3-N, however, did not follow this pattern, but increased from early June to the end of June and remained high until the first of September. We will present the results of bulk density data and seasonal N fertility data providing evidence for the impact of previous CC on corn production. Probable explanation for the mid-summer nitrogen decline will be presented and justification for reduced fertilizer application will be discussed.

  14. Thallium speciation and extractability in a thallium- and arsenic-rich soil developed from mineralized carbonate rock.

    PubMed

    Voegelin, Andreas; Pfenninger, Numa; Petrikis, Julia; Majzlan, Juraj; Pltze, Michael; Senn, Anna-Caterina; Mangold, Stefan; Steininger, Ralph; Gttlicher, Jrg

    2015-05-01

    We investigated the speciation and extractability of Tl in soil developed from mineralized carbonate rock. Total Tl concentrations in topsoil (0-20 cm) of 100-1000 mg/kg are observed in the most affected area, subsoil concentrations of up to 6000 mg/kg Tl in soil horizons containing weathered ore fragments. Using synchrotron-based microfocused X-ray fluorescence spectrometry (?-XRF) and X-ray absorption spectroscopy (?-XAS) at the Tl L3-edge, partly Tl(I)-substituted jarosite and avicennite (Tl2O3) were identified as Tl-bearing secondary minerals formed by the weathering of a Tl-As-Fe-sulfide mineralization hosted in the carbonate rock from which the soil developed. Further evidence was found for the sequestration of Tl(III) into Mn-oxides and the uptake of Tl(I) by illite. Quantification of the fractions of Tl(III), Tl(I)-jarosite and Tl(I)-illite in bulk samples based on XAS indicated that Tl(I) uptake by illite was the dominant retention mechanism in topsoil materials. Oxidative Tl(III)uptake into Mn-oxides was less relevant, probably because the Tl loadings of the soil exceeded the capacity of this uptake mechanism. The concentrations of Tl in 10 mM CaCl2-extracts increased with increasing soil Tl contents and decreasing soil pH, but did not exhibit drastic variations as a function of Tl speciation. With respect to Tl in contaminated soils, this study provides first direct spectroscopic evidence for Tl(I) uptake by illite and indicates the need for further studies on the sorption of Tl to clay minerals and Mn-oxides and its impact on Tl solubility in soils. PMID:25885948

  15. Clay fractions from a soil chronosequence after glacier retreat reveal the initial evolution of organo-mineral associations

    NASA Astrophysics Data System (ADS)

    Dmig, Alexander; Husler, Werner; Steffens, Markus; Kgel-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.

  16. 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.

  17. Initial litter and soil C and N mineralization dynamics for a semi-arid scrubland exposed to experimental N deposition

    NASA Astrophysics Data System (ADS)

    Biudes, M. S.; Vourlitis, G. L.

    2011-12-01

    Atmospheric N deposition is estimated to be 20-45 kgN ha-1 yr-1 in polluted urban scrublands and woodlands in southern California. High N input has the potential to alter soil organic matter and litter quantity and quality, which can stimulate N mineralization and influence the C storage and cycling by altering rates of soil respiration and litter decomposition. Using soil and litter collected from a long-term in situ N addition experiment in a coastal sage scrub (CSS) ecosystem of southern California, we measured rates of litter decomposition, microbial respiration and N mineralization during an 8-week laboratory incubation to test the hypothesis that N addition will increase microbial activity and initial rates of litter decomposition. The experimental design consisted of intact soil cores collected from field plots (2 cores per plot) exposed to either ambient or elevated N (50 kgN ha-1 yr-1) over an 8 year period (4 plots per treatment). Surface litter was removed from the soil cores and replaced with either no litter or litter of Artemisia californica Less. collected from the ambient and added N field plots described above. While the lab incubation period was short, approximately 33-61% of the initial litter mass was lost and decomposition was higher in control soil than soil exposed to added N. Microbial respiration, measured as soil CO2 efflux, was also significantly higher on control soil, and litter amendment, regardless of whether litter was exposed to ambient or added N, significantly increased microbial respiration. In contrast, net N mineralization was significantly higher in soil exposed to added N, and litter addition significantly depressed net N mineralization presumably because higher microbial respiration on litter substrates increased microbial demand for N. Our results are qualitatively similar to those reported from other decomposition experiments, which suggest that chronic N deposition fundamentally alters soil microbial structure and function, causing a decline in initial rates of litter decomposition. Such an initial decline in microbial respiration and N demand, if indicative of the longer-term decomposition kinetics, would act to increase in soil C storage and N availability. Longer term field and laboratory decomposition experiments are needed in semiarid regions to determine how soil C and N dynamics are affected by chronic N deposition.

  18. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

    NASA Astrophysics Data System (ADS)

    Schrumpf, M.; Kaiser, K.; Guggenberger, G.; Persson, T.; Kgel-Knabner, I.; Schulze, E.-D.

    2012-09-01

    Conceptual models suggest that stability and age of organic carbon (OC) in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Various tools like density fractionation, mineralization experiments, and radiocarbon analyses have been used to study the importance of these mechanisms. We systematically apply them to a range of European soils to test whether general controls emerge even for soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled in 10 cm depth intervals to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions - fLF, occluded light fractions - oLF, heavy fractions - HF) were analysed for OC, total nitrogen (TN), ?13C, and ?14C. Bulk samples were also incubated to determine mineralizable OC. Declining OC-normalized CO2 release and increasing age with soil depth confirm greater stability of OC in subsoils across sites. Depth profiles of LF-OC matched those of roots, which in turn reflect plant functional types in soil profiles not subject to ploughing. Modern ?14C signatures and positive correlation between mineralizable C and fLF-OC indicate the fLF is an easily available energy and nutrient source for subsurface microbes. Fossil C derived from the geogenic parent material affected the age of OC especially in the LF at three study sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining OC-normalized CO2 release rates with increasing contributions of HF-OC to bulk soil OC and the low ?14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. The decrease in ?14C (increase in age) of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the ?14C profiles. While quantitatively less important than OC in the HF, consistent older ages of oLF-OC than fLF-OC indicate that occlusion of LF-OC in aggregates also contributes to OC stability in subsoils. Overall, our results showed that association with minerals is the most important factor in stabilization of OC in soils.

  19. Genetically biodiverse potato cultivars grown on a suitable agricultural soil under compost amendment or mineral fertilization: yield, quality, genetic and epigenetic variations, soil properties.

    PubMed

    Cicatelli, Angela; Baldantoni, Daniela; Iovieno, Paola; Carotenuto, Maurizio; Alfani, Anna; De Feis, Italia; Castiglione, Stefano

    2014-09-15

    The use of compost for soil amendment is a promising agricultural practice environmentally and economically viable. In the framework of a wide research project designed to evaluate the effects of soil amendment with municipal solid waste compost in comparison with traditional mineral fertilization practices, 54 different cultivars (Cvs) of potatoes were AFLP (amplified fragment length polymorphism) molecularly fingerprinted. The seven most genetically biodiverse potato Cvs were used to establish an experimental field in southern Italy. The field area was divided into two portions fertilized with compost (20 Mg ha(-1)) or with ammonium sulphate (200 kg ha(-1)). No significant differences in productivity, organoleptic characteristics and element concentrations were observed between the potato tubers obtained with both kinds of soil fertilization, while the tubers grown on compost amended soil showed, on average, higher K concentrations with respect to those grown on mineral fertilised soil. cDNA-AFLP (complementary DNA-AFLP) and MSAP (methylation sensitive amplified polymorphism) analyses were carried out on both leaves and tubers of one selected Cv to estimate if any transcriptome alterations or epigenetic modifications were induced by the two kinds of fertilization, however no variations were detected. Chemical and biological soil qualities (i.e., microbial respiration, FDA hydrolysis, alkaline and acid phosphatase) were assessed on soil samples at the start of the experiment and at the end of potato crop cycle. No significant differences in soil pH and limited ones, in the available fraction of some trace elements, were observed; while conductivity was much higher for the compost amended portion of the experimental field. Microbial respiration, FDA hydrolysis and acid phosphatase activities were significantly increased by compost amendment, in comparison with mineral fertilization. Finally, a sensory panel of potato Cvs detected no significant differences among qualitative descriptors and among potatoes coming from the two differently fertilized soils. PMID:25016108

  20. Post-Fire Spatial Patterns of Soil Nitrogen Mineralization and Microbial Abundance

    PubMed Central

    Smithwick, Erica A. H.; Naithani, Kusum J.; Balser, Teri C.; Romme, William H.; Turner, Monica G.

    2012-01-01

    Stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. However, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. The objectives of this study were to (1) quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2) determine whether microbial variables aid predictions of in situ net nitrogen mineralization rates in recently burned stands. The study was conducted in lodgepole pine (Pinus contorta var. latifolia) and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) forest stands that burned during summer 2000 in Greater Yellowstone (Wyoming, USA). Using a fully probabilistic spatial process model and Bayesian kriging, the spatial structure of microbial lipid abundance and fungi-to-bacteria ratios were found to be spatially structured within plots two years following fire (for most plots, autocorrelation range varied from 1.5 to 10.5 m). Congruence of spatial patterns among microbial variables, in situ net N mineralization, and cover variables was evident. Stepwise regression resulted in significant models of in situ net N mineralization and included variables describing fungal and bacterial abundance, although explained variance was low (R2<0.29). Unraveling complex spatial patterns of nutrient cycling and the biotic factors that regulate it remains challenging but is critical for explaining post-fire ecosystem function, especially in Greater Yellowstone, which is projected to experience increased fire frequencies by mid 21st Century. PMID:23226324

  1. Post-fire spatial patterns of soil nitrogen mineralization and microbial abundance.

    PubMed

    Smithwick, Erica A H; Naithani, Kusum J; Balser, Teri C; Romme, William H; Turner, Monica G

    2012-01-01

    Stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. However, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. The objectives of this study were to (1) quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2) determine whether microbial variables aid predictions of in situ net nitrogen mineralization rates in recently burned stands. The study was conducted in lodgepole pine (Pinus contorta var. latifolia) and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) forest stands that burned during summer 2000 in Greater Yellowstone (Wyoming, USA). Using a fully probabilistic spatial process model and Bayesian kriging, the spatial structure of microbial lipid abundance and fungi-to-bacteria ratios were found to be spatially structured within plots two years following fire (for most plots, autocorrelation range varied from 1.5 to 10.5 m). Congruence of spatial patterns among microbial variables, in situ net N mineralization, and cover variables was evident. Stepwise regression resulted in significant models of in situ net N mineralization and included variables describing fungal and bacterial abundance, although explained variance was low (R<0.29). Unraveling complex spatial patterns of nutrient cycling and the biotic factors that regulate it remains challenging but is critical for explaining post-fire ecosystem function, especially in Greater Yellowstone, which is projected to experience increased fire frequencies by mid 21(st) Century. PMID:23226324

  2. Sorption-desorption of ionogenic compounds at the mineral-water interface: study of metal oxide-rich soils and pure-phase minerals.

    PubMed

    Vasudevan, Dharni; Cooper, Ellen M; Van Exem, Oliver L

    2002-02-01

    Sorption of the ionic compounds 2,4-D and quinmerac onto iron oxide-rich, variable charged soils was strongly influenced by mineralogy, particularly soil iron and aluminum oxides, whereas sorption of the neutral norflurazon was only related to total soil C. An appreciable fraction of the mass sorbed in stirred-flow studies was easily desorbed by deionized water, and desorption of ionic compounds was initially more rapid than sorption. This sorption-desorption behavior, although contrary to desorption hysteresis commonly observed in batch studies, suggests that the reversibly sorbed fraction is weakly bound to the soil surface. 2,4-D sorption to iron oxide-rich soils and pure-phase metal oxides appears to be driven by nonspecific electrostatic attraction, with specific electrostatic attraction and van der Waals interactions being secondary. Both the carboxylate and the heterocyclic N groups may participate in sorption of quinmerac, facilitated by specific and nonspecific electrostatic attraction and surface complexation. The heterocyclic N, amine, and carbonyl groups of norflurazon do not appear to interact with soil minerals. PMID:11871567

  3. Carbon dioxide emissions from semi-arid soils amended with biochar alone or combined with mineral and organic fertilizers.

    PubMed

    Fernndez, Jos M; Nieto, M Aurora; Lpez-de-S, Esther G; Gasc, Gabriel; Mndez, Ana; Plaza, Csar

    2014-06-01

    Semi-arid soils cover a significant area of Earth's land surface and typically contain large amounts of inorganic C. Determining the effects of biochar additions on CO2 emissions from semi-arid soils is therefore essential for evaluating the potential of biochar as a climate change mitigation strategy. Here, we measured the CO2 that evolved from semi-arid calcareous soils amended with biochar at rates of 0 and 20tha(-1) in a full factorial combination with three different fertilizers (mineral fertilizer, municipal solid waste compost, and sewage sludge) applied at four rates (equivalent to 0, 75, 150, and 225kg potentially available Nha(-1)) during 182 days of aerobic incubation. A double exponential model, which describes cumulative CO2 emissions from two active soil C compartments with different turnover rates (one relatively stable and the other more labile), was found to fit very well all the experimental datasets. In general, the organic fertilizers increased the size and decomposition rate of the stable and labile soil C pools. In contrast, biochar addition had no effects on any of the double exponential model parameters and did not interact with the effects ascribed to the type and rate of fertilizer. After 182 days of incubation, soil organic and microbial biomass C contents tended to increase with increasing the application rates of organic fertilizer, especially of compost, whereas increasing the rate of mineral fertilizer tended to suppress microbial biomass. Biochar was found to increase both organic and inorganic C contents in soil and not to interact with the effects of type and rate of fertilizer on C fractions. As a whole, our results suggest that the use of biochar as enhancer of semi-arid soils, either alone or combined with mineral and organic fertilizers, is unlikely to increase abiotic and biotic soil CO2 emissions. PMID:24632059

  4. Development and evaluation of a new sorption model for organic cations in soil: contributions from organic matter and clay minerals.

    PubMed

    Droge, Steven T J; Goss, Kai-Uwe

    2013-12-17

    This study evaluates a newly proposed cation-exchange model that defines the sorption of organic cations to soil as a summed contribution of sorption to organic matter (OM) and sorption to phyllosilicate clay minerals. Sorption to OM is normalized to the fraction organic carbon (fOC), and sorption to clay is normalized to the estimated cation-exchange capacity attributed to clay minerals (CECCLAY). Sorption affinity is specified to a fixed medium composition, with correction factors for other electrolyte concentrations. The model applies measured sorption coefficients to one reference OM material and one clay mineral. If measured values are absent, then empirical relationships are available on the basis of molecular volume and amine type in combination with corrective increments for specific polar moieties. The model is tested using new sorption data generated at pH 6 for two Eurosoils, one enriched in clay and the other, OM, using 29 strong bases (pKa > 8). Using experimental data on reference materials for all tested compounds, model predictions for the two soils differed on average by only -0.1 0.4 log units from measured sorption affinities. Within the chemical applicability domain, the model can also be applied successfully to various reported soil sorption data for organic cations. Particularly for clayish soils, the model shows that sorption of organic cations to clay minerals accounts for more than 90% of the overall affinity. PMID:24266749

  5. Metagenomes from thawing low-soil-organic-carbon mineral cryosols and permafrost of the canadian high arctic.

    PubMed

    Chauhan, Archana; Layton, Alice C; Vishnivetskaya, Tatiana A; Williams, Daniel; Pfiffner, Susan M; Rekepalli, Bhanu; Stackhouse, Brandon; Lau, Maggie C Y; Phelps, Tommy J; Mykytczuk, Nadia; Ronholm, Jennifer; Whyte, Lyle; Onstott, Tullis C; Sayler, Gary S

    2014-01-01

    Microbial release of greenhouse gases from thawing permafrost is a global concern. Seventy-six metagenomes were generated from low-soil-organic-carbon mineral cryosols from Axel Heiberg Island, Nunavut, Canada, during a controlled thawing experiment. Permafrost thawing resulted in an increase in anaerobic fermenters and sulfate-reducing bacteria but not methanogens. PMID:25414511

  6. Temperature, Water Content and Wet-Dry Cycle Effects on DOC Production and Carbon Mineralization in Agricultural Peat Soils.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A series of controlled laboratory experiments were utilized to examine factors affecting dissolved organic carbon (DOC) production and C mineralization rates over a range of conditions experienced resulting from agricultural practices in peat soils from the Sacramento-San Joaquin Delta. We conclude...

  7. Metagenomes from Thawing Low-Soil-Organic-Carbon Mineral Cryosols and Permafrost of the Canadian High Arctic

    PubMed Central

    Chauhan, Archana; Layton, Alice C.; Vishnivetskaya, Tatiana A.; Williams, Daniel; Pfiffner, Susan M.; Rekepalli, Bhanu; Stackhouse, Brandon; Lau, Maggie C. Y.; Phelps, Tommy J.; Mykytczuk, Nadia; Ronholm, Jennifer; Whyte, Lyle; Onstott, Tullis C.

    2014-01-01

    Microbial release of greenhouse gases from thawing permafrost is a global concern. Seventy-six metagenomes were generated from low-soil-organic-carbon mineral cryosols from Axel Heiberg Island, Nunavut, Canada, during a controlled thawing experiment. Permafrost thawing resulted in an increase in anaerobic fermenters and sulfate-reducing bacteria but not methanogens. PMID:25414511

  8. EFFECT OF SOIL TYPE AND FERTILIZATION LEVEL ON MINERAL CONCENTRATION OF PASTURE: RELATIONSHIP TO RUMINANT PERFORMANCE AND HEALTH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A three-year study was conducted to measure the effects of varying levels of dairy slurry application on mineral concentration of forages from three soils types. Slurry was applied to orchardgrass (Dactylis glomerata L., cv. Pennlate) growing in 60 cm diameter drainage lysimeters to measure the dir...

  9. EFFECT OF SOIL TYPE AND FERTILIZATION LEVEL ON MINERAL CONCENTRATION OF PASTURE: RELATIONSHIP TO RUMINANT PERFORMANCE AND HEALTH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was conducted to measure the effects of varying levels of dairy slurry application on mineral content of forages from three soils types. Slurry was applied to orchardgrass (Dactylis glomerata L., cv. Pennlate) using 60 cm diameter drainage lysimeters to measure the direct impact of four lev...

  10. The effect of increasing salinity and forest mortality on soil nitrogen and phosphorus mineralization in tidal freshwater forested wetlands

    USGS Publications Warehouse

    Noe, Gregory B.; Krauss, Ken W.; Lockaby, B. Graeme; Conner, William H.; Hupp, Cliff R.

    2013-01-01

    Tidal freshwater wetlands are sensitive to sea level rise and increased salinity, although little information is known about the impact of salinification on nutrient biogeochemistry in tidal freshwater forested wetlands. We quantified soil nitrogen (N) and phosphorus (P) mineralization using seasonal in situ incubations of modified resin cores along spatial gradients of chronic salinification (from continuously freshwater tidal forest to salt impacted tidal forest to oligohaline marsh) and in hummocks and hollows of the continuously freshwater tidal forest along the blackwater Waccamaw River and alluvial Savannah River. Salinification increased rates of net N and P mineralization fluxes and turnover in tidal freshwater forested wetland soils, most likely through tree stress and senescence (for N) and conversion to oligohaline marsh (for P). Stimulation of N and P mineralization by chronic salinification was apparently unrelated to inputs of sulfate (for N and P) or direct effects of increased soil conductivity (for N). In addition, the tidal wetland soils of the alluvial river mineralized more P relative to N than the blackwater river. Finally, hummocks had much greater nitrification fluxes than hollows at the continuously freshwater tidal forested wetland sites. These findings add to knowledge of the responses of tidal freshwater ecosystems to sea level rise and salinification that is necessary to predict the consequences of state changes in coastal ecosystem structure and function due to global change, including potential impacts on estuarine eutrophication.

  11. Submicron mineral structures control the stabilization of litter-derived organic matter in soils - A NanoSIMS study

    NASA Astrophysics Data System (ADS)

    Vogel, Cordula; Mueller, Carsten W.; Hschen, Carmen; Buegger, Franz; Heister, Katja; Schulz, Stefanie; Schloter, Michael; Kgel-Knabner, Ingrid

    2014-05-01

    The sequestration of carbon and nitrogen by clay-sized particles in soils is well established. However, in the most cases, the complex structure of the organo-mineral associations remain a black box due to the common measurements of soil fractions as a whole. By combining nano-scale secondary ion mass spectrometry (NanoSIMS) with isotopic tracing it is possible to study the formation and spatial heterogeneity of organo-mineral associations. NanoSIMS enables the detection of up to seven secondary ion species (e.g. 13C-, 12N15N-, 27Al16O-, 56Fe16O-) simultaneously, to generate a submicron-scale image of the elemental and isotopic composition (e.g. 13C, 15N, Al and Fe) down to a lateral resolution of ~150 nm. Therefore this technique can be used to study organo-mineral associations at the relevant scale. The aim of our study was to follow the formation of organo-mineral associations over different time steps and the distribution of C and N by imaging the complex arrangement between soil mineral surfaces and litter-derived organic matter (OM). Parallel to the determination of the isotopic N and C composition of bulk soil and soil fractions (combined density and particle size fractionation) using isotope ratio mass spectrometry (IRMS), the spatial distribution of the OM was investigated by NanoSIMS analysis of the clay-sized fraction. In our study we show that only some of the clay-sized surfaces bind OM. Surprisingly, less than 19% of the mineral areas visible by scanning electron microscopy and NanoSIMS show an OM attachment. We demonstrate that mineral clusters with rough surfaces exhibit the preferential binding spots for OM. By combining NanoSIMS and isotopic tracing, we distinguish between new labelled and pre-existing OM and show that new OM is preferentially attached to already present organo-mineral clusters. Vogel, C., Mueller, C.W., Hschen, C., Buegger, F., Heister, K., Schulz, S., Schloter, M., Kgel-Knabner, I., 2014. Submicron structures provide preferential spots for carbon and nitrogen sequestration in soils. Nature Communications 5. doi:10.1038/ncomms3947

  12. DRIFT and HR MAS NMR characterization of humic substances from a soil treated with different organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Ferrari, Erika; Francioso, Ornella; Nardi, Serenella; Saladini, Monica; Ferro, Nicola Dal; Morari, Francesco

    2011-07-01

    In this study, using DRIFT and HR MAS NMR, we analyzed the humic substances isolated from a soil treated, over 40 years, with different organic, mineral and organic plus mineral treatments and cultivated with maize as the main crop. As expected, the structure of humic substances was very complex but by combining both techniques (DRIFT and HR MAS NMR) additional information was obtained on aromatic and aliphatic components, the most recalcitrant parts of these macromolecules. In so doing we wanted to investigate the relationship between HS structure and long-term management practices. An elevated content of lignin, aminoacids, peptides and proteins was observed mainly for farmyard manure treatments with respect to mineral or liquid manure amendments; this supports how the different management practices have greatly influenced the humification process of cultivated soils.

  13. Impact of soil primary size fractions on sorption and desorption of atrazine on organo-mineral fractions.

    PubMed

    Huang, Yufen; Liu, Zhongzhen; He, Yan; Li, Yanliang

    2015-03-01

    In the current study, a mechanical dispersion method was employed to separate clay (<2 μm), silt (2-20 μm), and sand (20-50 μm) fraction in six bulk soils. Batch equilibrium method was used to conduct atrazine sorption and desorption experiments on soil organo-mineral fractions with bulk soils and their contrasting size fractions separately. The potential contribution of total organic carbon (TOC) for atrazine retention in different fractions was further investigated. It was found that clay fraction had the highest adsorption but the least desorption capacities for atrazine, while sand fraction had the lowest adsorption but the highest desorption capacities for atrazine. The adsorption percentage of atrazine, as compared with adsorption by the corresponding bulk soils, ranged from 53.6 to 80.5%, 35.7 to 56.4%, and 0.2 to 4.5% on the clay, silt, and sand fractions, respectively. TOC was one of the key factors affecting atrazine retention in soils, with the exact contribution dependent on varying degree of coating with mineral component in different soil size fractions. The current study may be useful to predict the bioavailability of atrazine in different soil size fractions. PMID:25300187

  14. Alaska Geochemical Database (AGDB)-Geochemical data for rock, sediment, soil, mineral, and concentrate sample media

    USGS Publications Warehouse

    Granitto, Matthew; Bailey, Elizabeth A.; Schmidt, Jeanine M.; Shew, Nora B.; Gamble, Bruce M.; Labay, Keith A.

    2011-01-01

    The Alaska Geochemical Database (AGDB) was created and designed to compile and integrate geochemical data from Alaska in order to facilitate geologic mapping, petrologic studies, mineral resource assessments, definition of geochemical baseline values and statistics, environmental impact assessments, and studies in medical geology. This Microsoft Access database serves as a data archive in support of present and future Alaskan geologic and geochemical projects, and contains data tables describing historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 85 laboratory and field analytical methods on 264,095 rock, sediment, soil, mineral and heavy-mineral concentrate samples. Most samples were collected by U.S. Geological Survey (USGS) personnel and analyzed in USGS laboratories or, under contracts, in commercial analytical laboratories. These data represent analyses of samples collected as part of various USGS programs and projects from 1962 to 2009. In addition, mineralogical data from 18,138 nonmagnetic heavy mineral concentrate samples are included in this database. The AGDB includes historical geochemical data originally archived in the USGS Rock Analysis Storage System (RASS) database, used from the mid-1960s through the late 1980s and the USGS PLUTO database used from the mid-1970s through the mid-1990s. All of these data are currently maintained in the Oracle-based National Geochemical Database (NGDB). Retrievals from the NGDB were used to generate most of the AGDB data set. These data were checked for accuracy regarding sample location, sample media type, and analytical methods used. This arduous process of reviewing, verifying and, where necessary, editing all USGS geochemical data resulted in a significantly improved Alaska geochemical dataset. USGS data that were not previously in the NGDB because the data predate the earliest USGS geochemical databases, or were once excluded for programmatic reasons, are included here in the AGDB and will be added to the NGDB. The AGDB data provided here are the most accurate and complete to date, and should be useful for a wide variety of geochemical studies. The AGDB data provided in the linked database may be updated or changed periodically. The data on the DVD and in the data downloads provided with this report are current as of date of publication.

  15. The adsorption and release of sulfur in mineral and organic soils of the Athabasca Oil Sands Region, Alberta, Canada.

    PubMed

    Whitfield, C J; Adkinson, A; Eimers, M C; Watmough, S A

    2010-01-01

    Mineral soil and fibric peat from acid-sensitive western boreal catchments in the Athabasca Oil Sands Region of Alberta, Canada were evaluated for their ability to adsorb and release SO(4)(2-). Laboratory batch studies indicated that SO(4)(2-) adsorption in mineral soil from both the A and B horizons exhibits a limited response to elevated SO(4)(2-) concentrations, with the slope of initial mass isotherms <0.2 for all soils, likely due to low iron and aluminum oxide content. Although S retention is the dominant process in peat soils in the region, drought simulations in the lab using fibric peat collected from a poor fen exhibited as much as a five-fold increase in SO(4)(2-) concentration after drying and rewetting. Given the limited SO(4)(2-) adsorption capacity of mineral soils and the potential drought-induced S release from peatlands in this region where increased S deposition is expected, further investigation of acidification impacts is warranted. PMID:20400606

  16. A survey of mineral status of soils, feeds and cattle in the Selale Ethiopian highlands. I. Macro elements.

    PubMed

    Khalili, M; Lindgren, E; Varvikko, T

    1993-08-01

    The macro mineral status of cattle in the Selale highlands of Ethiopia was evaluated during the rainy and dry seasons of 1989 and 1990 in terms of mineral concentrations in soils, feeds, blood plasma and faeces on 25 farms. Bone samples from animals of local breeds from a slaughter house were collected during the rainy and dry seasons of 1990. Soils were analysed for pH, organic matter, Ca, P, Mg, Na and K. The results indicated wide variation in the concentrations of minerals on different farms. Available feeds in the area consist of pasture, hay, the straw of barley, oats and teff, and the grains of barley and oats. Pasture grass and other feeds were found to be deficient in Na, P and Mg in relation to dietary requirements. Analyses of blood plasma from crossbred and local cattle showed that a number of samples contained P below the critical level of 1.45 mmol/litre. Effects of year and season were significant for Ca, P, Mg and K. The effect of age was significant for P (P < 0.001). Faecal analyses revealed that about 80% of animals were deficient in Na. Wide variations in the mineral content of soils and lack of significant correlations among soil, pasture and blood plasma indicated that soil and pasture analyses are not reliable in assessing macro mineral status of grazing cattle in this environment. Analyses of bone and blood for Ca and P, blood for Mg and faeces for Na appear to provide better indices. PMID:8236493

  17. Mineral cycling in soil and litter arthropod food chains. Progress report, November 1, 1980-October 31, 1981

    SciTech Connect

    Crossley, D.A. Jr.

    1980-06-15

    Progress and current status are reported for research projects concerned with mineral element and nutrient dynamics in soil arthropod food chains. Research is performed within the larger context of terrestrial decomposition, in which soil arthropods may act as regulators of nutrient dynamics during decomposition. Research is measuring rates of nutrient accumulation and excretion by using radioactive tracer analogs of nutrients. This year, emphasis has been placed on field work in which soil arthropod population size and nutrients inputs were varied experimentally. The presence of microarthropods in field microcosms increased the mineralization of N and P in each case, but rates were not correlated with arthropod densities. Experiments recently started are using both arthropod and microfloral inhibitors, in open systems on the forest floor, with the objective of quantifying arthropod enhancement of microbial immobilization of nutrients.

  18. The content of available mineral phosphorus compounds in chestnut soils of Northern Mongolia upon application of different forms of phosphorite

    NASA Astrophysics Data System (ADS)

    Ubugunov, L. L.; Enkhtuyaa, B.; Merkusheva, M. G.

    2015-06-01

    The effect of different forms of phosphorite (activated and crude ground) of the Burenkhansk deposit on the phosphate status of chestnut soils and the productivity of spring wheat was studied in Northern Mongolia. It was found that the transformation of mineral soil phosphates upon the application of activated phosphorite (together with NK) is similar to that upon superphosphate application, and the available phosphorus concentration is even a gradation higher. The application of crude ground phosphorite helped to preserve the content of mineral phosphates in the soil at the initial level. Optimum concentrations of available phosphorus and the sum of loosely bound and calcium phosphates in the plow horizon were estimated 33-35 mg/kg) and 16-18 mg/100 g, respectively. Under these concentrations, high and sustainable yields of spring wheat were obtained upon application of activated phosphorite.

  19. Effect of clay minerals present in aquifer soils on the adsorption and desorption of hydrophobic organic compounds

    SciTech Connect

    Ghosh, D.R. ); Keinath, T.M. )

    1994-02-01

    Adsorption of hydrophobic organic compounds (HOCs) onto clay minerals and organic matter present in soils results in retarding their mobility. To study the impact of clay minerals on HOC sorption, kinetic and equilibrium studies were performed using naphthalene as a test surrogate contaminant. The results of these studies indicated that expandable clay minerals (clays that expand and expose large internal surface area on wetting), such as montmorillonite and vermiculite, had a significant impact on naphthalene partitioning. A mathematical model was developed from the equilibrium data which related clay mineral concentrations with the naphthalene partition coefficient. Equilibrium desorption studies were also performed by adding a micellar solution of a surfactant mixture (50:50) of Tween 20 and Aerosol AY-65 to mobilize the adsorbed naphthalene. The surfactant mixture was generally unable to mobilize the sorbed contaminant due to sorption irreversibility and adsorption hysteresis. 36 refs., 1 fig., 5 tabs.

  20. Factors driving the carbon mineralization priming effect in a sandy loam soil amended with different types of biochar

    NASA Astrophysics Data System (ADS)

    Cely, P.; Tarquis, A. M.; Paz-Ferreiro, J.; Méndez, A.; Gascó, G.

    2014-06-01

    The effect of biochar on the soil carbon mineralization priming effect depends on the characteristics of the raw materials, production method and pyrolysis conditions. The goal of the present study is to evaluate the impact of three different types of biochar on physicochemical properties and CO2 emissions of a sandy loam soil. For this purpose, soil was amended with three different biochars (BI, BII and BIII) at a rate of 8 wt% and soil CO2 emissions were measured for 45 days. BI is produced from a mixed wood sieving from wood chip production, BII from a mixture of paper sludge and wheat husks and BIII from sewage sludge. Cumulative CO2 emissions of biochars, soil and amended soil were well fit to a simple first-order kinetic model with correlation coefficients (r2) greater than 0.97. Results show a negative priming effect in the soil after addition of BI and a positive priming effect in the case of soil amended with BII and BIII. These results can be related to different biochar properties such as carbon content, carbon aromaticity, volatile matter, fixed carbon, easily oxidized organic carbon or metal and phenolic substance content in addition to surface biochar properties. Three biochars increased the values of soil field capacity and wilting point, while effects over pH and cation exchange capacity were not observed.

  1. How biological crusts are stabilizing the soil surface? The devolpment of organo-mineral interactions in the initial phase

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Veste, M.; Wiehe, W.; Lange, P.

    2009-04-01

    First colonizers of new land surfaces are cryptogames which often form biological soil crusts (BSC) covering the first millimetre of the top soil in many ecosystems from polar to desert ecosystems. These BSC are assemblages of cyanobacteria, green algae, mosses, liverworts, fungi and/or lichens. The development of soil surface crusts plays a major role for the further vegetation pattern through changes to the physico-chemical conditions and influencing various ecosystem processes. We studied the development of BSC on quaternary substrate of an initial artificial water catchment in Lusatia, Germany. Due to lack of organic matter in the geological substrate, photoautotrophic organisms like green algae and cyanobacteria dominated the initial phases of ecosystem development and, hence, of organo-mineral ineractions. We combined SEM/EDX and FTIR microscopy to study the contact zone of extracellular polymeric substances (EPS) of green algae and cyanobacteria with quartz, spars and mica on a >40 µm scale in undisturbed biological soil crusts, which had a maximum thickness of approx. 2 mm. SEM/EDX microscopy was used to determine the spatial distribution of S, Ca, Fe, Al, Si and K in the profiles, organic compounds were identified using FTIR microscopy. Exudates of crust organisms served as cementing material between sand particles. The crust could be subdivided into two horizontal layers. The upper layer, which had a thickness of approx. 200 µm, is characterized by accumulation of Al and K, but absence of Fe in microbial derived organic matter, indicating capture of weathering products of feldspars and mica by microbial exudates. The pore space between mineral particles was entirely filled with organic matter here. The underlying layer can be characterized by empty pores and organo-mineral bridges between the sand particles. Contrarily to the upper layer of the crust, Fe, Al and Si were associated with organic matter here but K was absent. Highest similarity of the FTIR spectra of EPS was observed with carbohydrates, using cellulose, dextran and humic acid Na salt as controls. Obviously, humification does not play a key role during this initial phase of soil formation. It was hypothesized that biological soil crusts facilitate the weathering of mineral substrate by (I) circumventing loss of fine particles with erosion, (II) by chemical treatment of minerals and (III) by catching small mineral-particles by glutinous EPS on the soil surface from the surrounding area.

  2. Maize Varieties Released in Different Eras Have Similar Root Length Density Distributions in the Soil, Which Are Negatively Correlated with Local Concentrations of Soil Mineral Nitrogen

    PubMed Central

    Ning, Peng; Li, Sa; White, Philip J.; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 060 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 3060 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 020 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize. PMID:25799291

  3. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    PubMed

    Ning, Peng; Li, Sa; White, Philip J; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize. PMID:25799291

  4. Recent (<4 year old) Leaf Litter is Not a Major Source of Microbial Carbon in a Temperate Forest Mineral Soil

    SciTech Connect

    Kramer, Christiane; Trumbore, Susan E.; Froberg, Mats J.; Cisneros dozal, Luz Maria; Zhang, Dachun; Xu, Xiamei; Santos, Guaciara; Hanson, Paul J