Science.gov

Sample records for iron-oxyhydroxide soil minerals

  1. Iron oxyhydroxide mineralization on microbial extracellular polysaccharides

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

    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 (μXRF) 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 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.

  3. 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

  4. 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.

  5. 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.

  6. Reactivity of Uranium and Ferrous Iron with Natural Iron Oxyhydroxides.

    PubMed

    Stewart, Brandy D; Cismasu, A Cristina; Williams, Kenneth H; Peyton, Brent M; Nico, Peter S

    2015-09-01

    Determining key reaction pathways involving uranium and iron oxyhydroxides under oxic and anoxic conditions is essential for understanding uranium mobility as well as other iron oxyhydroxide mediated processes, particularly near redox boundaries where redox conditions change rapidly in time and space. Here we examine the reactivity of a ferrihydrite-rich sediment from a surface seep adjacent to a redox boundary at the Rifle, Colorado field site. Iron(II)-sediment incubation experiments indicate that the natural ferrihydrite fraction of the sediment is not susceptible to reductive transformation under conditions that trigger significant mineralogical transformations of synthetic ferrihydrite. No measurable Fe(II)-promoted transformation was observed when the Rifle sediment was exposed to 30 mM Fe(II) for up to 2 weeks. Incubation of the Rifle sediment with 3 mM Fe(II) and 0.2 mM U(VI) for 15 days shows no measurable incorporation of U(VI) into the mineral structure or reduction of U(VI) to U(IV). Results indicate a significantly decreased reactivity of naturally occurring Fe oxyhydroxides as compared to synthetic minerals, likely due to the association of impurities (e.g., Si, organic matter), with implications for the mobility and bioavailability of uranium and other associated species in field environments. PMID:26226398

  7. Role of sol with iron oxyhydroxide/sodium dodecyl sulfate composites on Fenton oxidation of sorbed phenanthrene in sand.

    PubMed

    Park, Joo-Yang; Kim, Jung-Hwan

    2013-09-15

    In situ Fenton oxidation has been recently used to oxidize sorbed organic contaminants in soil. The objective of present contribution was to study the role of sodium dodecyl sulfate (SDS) as anionic surfactant and sol with iron oxyhydroxide/SDS for Fenton oxidation of sorbed phenanthrene in sand. The most effective experimental condition for phenanthrene oxidation was the Fenton-like reaction system with 0.35% H2O2, 30 mM SDS, and 4 mM FeCl2. The Fenton-like reactions under these experimental conditions resulted in the production and sustenance of a stable sol with iron oxyhydroxide/SDS composites over 24 h. The formation of iron oxyhydroxide/SDS composites resulted in stabilization of H2O2, and then the Fenton-like reactions were sustained over 24 h. Furthermore, the sol of iron oxyhydroxide/SDS composites gave suitable sites to sustain oxidations of dissolved phenanthrene over a prolonged reaction span, which is required for in situ chemical oxidation. PMID:23666072

  8. 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

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

    PubMed

    Wang, Dengjun; Bradford, Scott A; Harvey, Ronald W; Gao, Bin; Cang, Long; Zhou, Dongmei

    2012-03-01

    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 transport and retention kinetics of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated packed columns that encompassed a range of humic acid concentrations (HA, 0-10 mg L(-1)), fractional surface coverage of iron oxyhydroxide coatings on sand grains (λ, 0-0.75), and pH (6.0-10.5). HA was found to have a marked effect on the electrokinetic properties of ARS-nHAP, and on the transport and retention of ARS-nHAP in granular media. The transport of ARS-nHAP was found to increase with increasing HA concentration because of enhanced colloidal stability and the reduced aggregate size. When HA = 10 mg L(-1), greater ARS-nHAP attachment occurred with increasing λ because of increased electrostatic attraction between negatively charged nanoparticles and positively charged iron oxyhydroxides, although alkaline conditions (pH 8.0 and 10.5) reversed the surface charge of the iron oxyhydroxides and therefore decreased deposition. The retention profiles of ARS-nHAP exhibited a hyperexponential shape for all test conditions, suggesting some unfavorable attachment conditions. Retarded breakthrough curves occurred in sands with iron oxyhydroxide coatings because of time-dependent occupation of favorable deposition sites. Consideration of the above effects is necessary to improve remediation efficiency of nHAP for metals and actinides in soils and subsurface environments. PMID:22316080

  10. Antagonistic effects of humic acid and iron oxyhydroxide grain-coating on biochar nanoparticle transport in saturated sand.

    PubMed

    Wang, Dengjun; Zhang, Wei; Zhou, Dongmei

    2013-05-21

    Biochar land application may result in multiple agronomic and environmental benefits (e.g., carbon sequestration, improving soil quality, and immobilizing environmental contaminants). However, our understanding of biochar particle transport is largely unknown in natural environments with significant heterogeneity in solid (e.g., patches of iron oxyhydroxide coating) and solution chemistry (e.g., the presence of natural organic matter), which represents a critical knowledge gap in assessing the environmental impact of biochar land application. Transport and retention kinetics of nanoparticles (NPs) from wheat straw biochars produced at two pyrolysis temperatures (i.e., 350 and 550 °C) were investigated in water-saturated sand columns at environmentally relevant concentrations of dissolved humic acid (HA, 0, 1, 5, and 10 mg L(-1)) and fractional surface coverage of iron oxyhydroxide coatings on sand grains (ω, 0.16, 0.28, and 0.40). Transport of biochar NPs increased with increasing HA concentration, largely because of enhanced repulsive interaction energy between biochar NPs and sand grains. Conversely, transport of biochar NPs decreased significantly with increasing ω due to enhanced electrostatic attraction between negatively charged biochar NPs and positively charged iron oxyhydroxides. At a given ω of 0.28, biochar NPs were less retained with increasing HA concentration due to increased electrosteric repulsion between biochar NPs and sand grains. Experimental breakthrough curves and retention profiles were well described using a two-site kinetic retention model that accounted for Langmuirian blocking or random sequential adsorption at one site. Consistent with the blocking effect, the often observed flat retention profiles stemmed from decreased retention rate and/or maximum retention capacity at a higher HA concentration or smaller ω. The antagonistic effects of HA and iron oxyhydroxide grain-coating imparted on the mobility of biochar NPs suggest that

  11. 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.

  12. 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

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1993-11-01

    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.

  16. 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

  17. 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

  18. 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.

  19. Mineralogy and inorganic chemistry of naturally occurring biogenic iron oxyhydroxides: Spectroscopic evidence of thermal maturation

    NASA Astrophysics Data System (ADS)

    Haddad, A.; Fakra, S.; Orcutt, B. N.; Toner, B.; Edwards, K. J.

    2011-12-01

    Microbial mats were sampled at four sites at the Lo'ihi Seamount and examined for changes in mineralogy and inorganic chemistry via synchrotron-sourced X-ray Absorption Spectroscopy (XAS). These mats are rich in iron oxyhydroxides with morphologies similar to those produced by iron oxidizing microorganisms related to Zetaproteobacteria such as Mariprofundus ferroxydans, which have been shown to be present and active in all of these mat ecosystems. The same particle morphologies are observed consistently at all four sites, which range in temperature (4 - 40°C) and hydrothermal activity (dead to very active). Fe L-edge XAS reveals no significant differences in Fe speciation between the morphologies. Mineralogy, however, as reflected in O 1s XAS measurements, appears to be a function of thermal maturation with the hottest site harboring more crystalline particles. Morphology does not factor into the changes in mineralogy. These measurements are confirmed by Fe 1s XAS spectroscopy. The C 1s XAS spectroscopy is highly variable and may be related to overall maturation (age) or undetermined factors. Elucidating the effect of thermal maturation on biogenic iron oxhydroxide particles is essential to understanding the environmental influences on their preservation in the rock record.

  20. Aqueous solution deposition kinetics of iron oxyhydroxide on sulfonic acid terminated self-assembled monolayers

    SciTech Connect

    Rieke, P.C.; Marsh, B.D.; Wood, L.L.; Tarasevich, B.J.; Liu, J.; Song, L.; Fryxell, G.E. )

    1995-01-01

    The deposition kinetics of iron oxyhydroxide on sulfonic acid terminated self-assembled monolayers were studied. The thin films of FeOOH were formed on the substrates by thermal hydrolysis of millimolar aqueous solutions of Fe(NO[sub 3])[sub 3] at a pH of approximately 2.0. The thickness of the films was measured ellipsometrically at various times. Both Fe(NO[sub 3])[sub 3] and HNO[sub 3] concentrations were independently varied to provide varying degrees of solution supersaturation. Depending on these concentrations, an induction time was observed before film growth commenced. The correlation between supersaturation and induction time was modeled using classical nucleation theory. Very good agreement was observed regardless of whether supersaturation was varied via the concentration of Fe(NO[sub 3])[sub 3] or HNO[sub 3]. From these results an interfacial free energy for nucleation of 148 mJ/m[sup 2] was calculated. The critical nucleus species was identified as a tetrameric iron species by considering the order of nucleation. 49 refs., 11 figs., 1 tab.

  1. Mineralization of Iron Oxyhydroxides in the Presence and in the Absence of Bacterial Cells

    NASA Astrophysics Data System (ADS)

    Châtellier, X.; West, M.; Rose, J.; Fortin, D.; Leppard, G. G.; Ferris, G.

    2001-12-01

    Because of their small size, iron oxides have a large surface area per unit weight ratio and are believed to play an important role as an adsorbing phase in lake sediments for various molecules, including potentially dangerous ones like heavy metals. They have been observed to form in close association with bacterial cells, by oxidation of ferrous ions. It is thus important to determine whether the presence of the bacterial cells can affect the mineralogy and the mesoscopic structure of the Fe-oxides particles, as well as their reactivity towards heavy metals. We synthesized in the lab nanoparticles of Fe-oxides by oxidation of ferrous ions. This was done in the presence and in the absence of various bacterial strains (Escherichia coli, Bacillus subtilis, Pseudomonas Aeruginosa and Bacillus licheniformis) and of inorganic ligands (sulfate, phosphate, silicate). The Fe-oxides particles were then observed by TEM on thin sections and on whole mounts. The chemical composition was estimated by wet chemistry and by EDS. The mineralogy was determined by XRD, SAED and EXAFS. Surface area was investigated by BET. And adsorption of cadmium was also measured at various pH. We observed that the size and the morphology of the particles as well as their mesoscopic spatial organization can be affected by the presence of the cells, whereas the mineralogy is controlled by the chemistry of the solution. The adsorption isotherms of cadmium on the various Fe-oxides will be discussed at the light of these observations.

  2. 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

  3. 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

  4. 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

  5. Soil organic matter mineralization in frozen soils

    NASA Astrophysics Data System (ADS)

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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration

    NASA Astrophysics Data System (ADS)

    da Cunha, Camila C. R. F.; da Costa, Geraldo M.

    2016-08-01

    Protohematite (Fe2-x/3(OH) x O3-x 1 ≤ x < 0.5) and hydrohematite (Fe2-x/3(OH) x O3-x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.

  12. 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

  13. 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

  14. 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

    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.

  15. 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

  16. Measuring Soil Nitrogen Mineralization under Field Conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land application of animal manure is known to alter rates of nitrogen (N) mineralization in soils, but quantitative information concerning intensity and duration of these effects has been difficult to obtain under field conditions. We estimated net effects of manure on N mineralization in soils unde...

  17. 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 +4°C). Freezing of the soil markedly reduced microbial utilization of the cellulose. The [13C]-CO2 production rate in the samples at +4°C were 0.52 mg CO2 SOM -1 day-1 while rates in the frozen samples (-4°C) 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

  18. 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.

  19. Nitrogen mineralization in a tussock tundra soil

    SciTech Connect

    Marion, G.M.; Miller, P.C.

    1982-01-01

    The effects of substrate quality, temperature, and moisture on nitrogen mineralization from a tussock tundra soil were examined with laboratory soil incubations utilizing both air-dried samples and field-moist intact cores. The potentially mineralizable nitrogen (PMN) was highly correlated to both total soil nitrogen (positively) and the carbon/nitrogen ratio (negatively). All soil horizons exhibited a net nitrogen mineralization even at a high carbon/nitrogen ratio of 92. It was concluded that field-moist intact soil cores provide a more reliable estimate than the air-dried samples of both PMN and the mineralization rate under standard laboratory conditions. There was no significant effect of moisture tension (0.0 to 0.4 bars) on net nitrogen mineralization. The average Q/sub 10/ (temperature effect) for net nitrogen mineralization was 2.5. Based on this study and others, it was concluded that temperature through its effect on nitrogen mineralization plays an important role in controlling plant productivity in these naturally nitrogen-deficient tundra ecosystems.

  20. 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 +4°C). The [13C]-CO2 production rate in the samples at +4°C were 0.524 mg CO2 SOM -1 day-1 while rates in the frozen samples (-4°C) 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.

  1. 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

  2. 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.

  3. 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...

  4. 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...

  5. 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...

  6. Electrokinetic properties of soil minerals and soils modified with polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Kurochkina, G. N.; Pinskii, D. L.; Haynos, M.; Sokolowska, Z.; Tsesla, I.

    2014-07-01

    The formation features of nanoadsorption polyelectrolyte (PE) layers with the formation of a mineral-organic matrix on the surface of clay minerals and soils (kaolinite, montmorillonite, quartz sand, gray forest soil, and chernozemic soil) have been elucidated by direct adsorption measurements. It has been found that the experimental values for the limit adsorption of polyacrylamide (PAM) and polyacrylic acid (PAA) on all the minerals are significantly higher than the calculated values for the formation of a monolayer. This indicates adsorption on the surface of not only separate macromolecules but also secondary PE structures as packets or fibrils determining the cluster-matrix structure of the modified surface. The study of the electro-surface properties (electrophoretic mobility, electrokinetic potential, pH, and electroconductivity) of mineral and soil particles adsorption-modified with PEs has confirmed the differences in the adsorption mechanisms (from physical sorption to chemisorption) with the formation of surface compounds depending on the different polar groups of PEs and the mineral type.

  7. Reverse micelle synthesis of nanoscale metal containing catalysts. [Nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide nanoscale powders

    SciTech Connect

    Darab, J.G.; Fulton, J.L.; Linehan, J.C.

    1993-03-01

    The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction and precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni[sub 3]Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.

  8. 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 4°C. 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

  9. 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

  10. 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

  11. Clay mineral type effect on bacterial enteropathogen survival in soil.

    PubMed

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

    2014-01-15

    Enteropathogens released into the environment can represent a serious risk to public health. Soil clay content has long been known to have an important effect on enteropathogen survival in soil, generally enhancing survival. However, clay mineral composition in soils varies, and different clay minerals have specific physiochemical properties that would be expected to impact differentially on survival. This work investigated the effect of clay materials, with a predominance of a particular mineral type (montmorillonite, kaolinite, or illite), on the survival in soil microcosms over 96 days of Listeria monocytogenes, Salmonella Dublin, and Escherichia coli O157. Clay mineral addition was found to alter a number of physicochemical parameters in soil, including cation exchange capacity and surface area, and this was specific to the mineral type. Clay mineral addition enhanced enteropathogen survival in soil. The type of clay mineral was found to differentially affect enteropathogen survival and the effect was enteropathogen-specific. PMID:24035982

  12. The associations of heavy metals with crystalline iron oxides in the polluted soils around the mining areas in Guangdong Province, China.

    PubMed

    Yin, Hui; Tan, Nianhao; Liu, Chuanping; Wang, Juju; Liang, Xiaoliang; Qu, Mingkai; Feng, Xionghan; Qiu, Guohong; Tan, Wenfeng; Liu, Fan

    2016-10-01

    In current selective sequential extraction (SSE) methods, heavy metals associated well-crystallized iron oxyhydroxides are not well defined and considered, and usually fall into residual forms, which actually make their mobility and environmental risk underestimated. This study compared various fractions of heavy metals in samples of mining tailings and nearby soils under different land uses in Guangdong Province of China. Iron oxides in these soils were mainly Al-substituted goethites and/or hematites. Independent of the land uses, the percentages of various Cd fractions in the soils decrease in the order of well-crystallized iron oxyhydroxides-associated (27.2-91.2%) > residual (2.1-37.0%) > reducible FeMn oxides (3.2-45.7%) > exchangeable (1.0-28.2%) > organic-associated form (0-5.1%). Pb mainly existes in the residual fraction (25.9-74.5%), followed by crystalline iron oxyhydroxides-associated (0.4-69.0%) and reducible fractions (2.4-40.4%). Zn mainly exists in the residual fraction (25.4-85.9%), followed by the well-crystallized iron oxyhydroxides-associated fraction (6.4-55.0%). However, Cu mainly existes in the residual form and the fractionation of Cu varies obviously between samples. The association of these metals with crystalline iron oxyhydroxides in the soils decreases in the sequence of Cd > Pb > Zn > Cu. These results suggest that in heavy-metal-polluted weathered soils in tropical and subtropical areas enriched with iron oxides, it is essential to assess potential bioavailability and toxicity of heavy metals bound to well-crystallized iron oxyhydroxides with appropriate procedures in the fractionation measurement. The modified Tessier method present here can be used to quantify the fractions of heavy metals in such areas. PMID:27427775

  13. 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

  14. 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

  15. 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

  16. 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.

  17. Relationship between carbon and nitrogen mineralization in a subtropical soil

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  18. 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

  19. 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 δ56Fe 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 δ56Fe 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.

  20. 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.

  1. The Impact of Organo-Mineral Complexation on Mineral Weathering in the Soil Zone: Column Experiment

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    While it is well known that organo-mineral complexes can protect organic matter (OM) from degradation, its impact on soil mineral weathering is not clear. Strong evidence has shown that the adsorption of OM to mineral surface accelerates the dissolution of some minerals, but these observations are limited to bench-scale experiments that focus on specific OM and minerals. In this study, soil samples prepared from an undisturbed forest site were used to determine mineral weathering rates under differing OM sorption on minerals. Soil samples from two depths, 0-6cm and 84-100cm, were chosen to represent different soil OM content and soil mineralogy. Soil OM was removed stepwise by heating samples to 350℃ for different durations (0-6cm: 100% removed, ~50% removed, and no removal; 84-100cm: 100% removed and no removal). Pretreated soil samples were subjected to flow-through, saturated column experiments using 0.01M LiCl and 5%CO2/95%air gas saturated (pH = 4.5) influent solution. Each column treatment was run in duplicate under a constant flow rate (Darcy velocity ≈ 8cm/hr). All columns reached a steady state after 600~700 pore volumes at which effluent pH, dissolved organic carbon (DOC) and element concentrations were constant. At the 95% significance level, the DOC from OM-present columns was significantly higher, as expected. Correspondingly, effluent pH was lower in higher OM content columns. The chemical denudation rates were calculated from the effluent concentrations of the elements of interest. For the soil columns from both depths, silicon (Si) leaching rate showed that dissolution of silicate minerals was 2-3 times higher in OM-removed columns, suggesting that organo-mineral complexes suppress mineral dissolution. The N2-BET specific surface area (SSA) measurement also showed that the removal of OM increased SSA, which supported the idea that OM adsorption had decreased mineral exposure and thus decreased mineral dissolution. The leaching rates of some

  2. 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

  3. Acid rains`s dirty business: Stealing minerals from soil

    SciTech Connect

    Kaiser, J.

    1996-04-12

    This article describes the hidden environmental effects of acid rain - leaching of base mineral ions from the soil, often changing soil chemistry dramatically. The primary information comes from Ecosystem studies at Hubbard Brook of Likens and Buso. The article also discusses both other opinions and possible solutions.

  4. 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...

  5. Kinetics of methane oxidation in selected mineral soils

    NASA Astrophysics Data System (ADS)

    Walkiewicz, A.; Bulak, P.; Brzeziñska, M.; Włodarczyk, 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.

  6. Mineral protection of soil carbon counteracted by root exudates

    NASA Astrophysics Data System (ADS)

    Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; Pett-Ridge, Jennifer; Weber, Peter K.; Kleber, Markus

    2015-06-01

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

  7. A scalable model for methane consumption in arctic mineral soils

    NASA Astrophysics Data System (ADS)

    Oh, Youmi; Stackhouse, Brandon; Lau, Maggie C. Y.; Xu, Xiangtao; Trugman, Anna T.; Moch, Jonathan; Onstott, Tullis C.; Jørgensen, Christian J.; D'Imperio, Ludovica; Elberling, Bo; Emmerton, Craig A.; St. Louis, Vincent L.; Medvigy, David

    2016-05-01

    Recent field studies have documented a surprisingly strong and consistent methane sink in arctic mineral soils, thought to be due to high-affinity methanotrophy. However, the distinctive physiology of these methanotrophs is poorly represented in mechanistic methane models. We developed a new model, constrained by microcosm experiments, to simulate the activity of high-affinity methanotrophs. The model was tested against soil core-thawing experiments and field-based measurements of methane fluxes and was compared to conventional mechanistic methane models. Our simulations show that high-affinity methanotrophy can be an important component of the net methane flux from arctic mineral soils. Simulations without this process overestimate methane emissions. Furthermore, simulations of methane flux seasonality are improved by dynamic simulation of active microbial biomass. Because a large fraction of the Arctic is characterized by mineral soils, high-affinity methanotrophy will likely have a strong effect on its net methane flux.

  8. Adsorption coefficients for TNT on soil and clay minerals

    NASA Astrophysics Data System (ADS)

    Rivera, Rosángela; Pabón, Julissa; Pérez, Omarie; Muñoz, 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.

  9. [Occurrence relationship between iron minerals and clay minerals in net-like red soils: evidence from X-ray diffraction].

    PubMed

    Yin, Ke; Hong, Han-Lie; Han, Weni; Ma, Yu-Bo; Li, Rong-Biao

    2013-04-01

    The high purity of clay minerals is a key factor to reconstruct the palaeoclimate in clay mineralogy, however, the existence of iron minerals (such as goethite and hematite) and organics lead to the intergrowth of clay minerals and other minerals, producing other mineral impurities in enriched clay minerals. Although the removal of organics in soil sediments has been fully investigated, the occurrence state of iron minerals remains controversial, hindering the preparation of high-purity clay minerals. Therefore, the occurrence relationship of iron minerals and clay minerals in Jiujiang net-like red soils of the middle to lower reaches of the Yangtze River was investigated using the sequential separation method, which provided some implications for the removal of iron minerals in soil sediments. The results indicated that goethite and hematite were mostly absorbed on the surface of hydroxy-interlayered smectite and illite in the form of films, and the rest were absorbed by kaolinite. PMID:23841442

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

    NASA Astrophysics Data System (ADS)

    Ahmed, Engy; Holmström, 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.

  11. 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 2θ 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.

  12. 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...

  13. 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

  14. 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.

  15. 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...

  16. 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...

  17. 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.

  18. [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

  19. Mineralization of hexachlorocyclohexane in soil during solid-phase bioremediation.

    PubMed

    Phillips, Theresa M; Lee, Hung; Trevors, Jack T; Seech, Alan G

    2004-06-01

    Soil containing hexachlorocyclohexane (HCH) was spiked with (14)C-gamma-HCH and then subjected to bioremediation in bench-scale microcosms to determine the rate and extent of mineralization of the (14)C-labeled HCH to (14)CO(2). The soil was treated using two different DARAMEND amendments, D6386 and D6390. The amendments were previously found to enhance natural HCH bioremediation as determined by measuring the disappearance of parent compounds under either strictly oxic conditions (D6386), or cycled anoxic/oxic conditions (D6390). Within 80 days of the initiation of treatment, mineralization was observed in all of the strictly oxic microcosms. However, mineralization was negligible in the cycled anoxic/oxic microcosms throughout the 275-day study, even after cycling was ceased at 84 days and although significant removal (up to 51%) of indigenous gamma-HCH (146 mg/kg) was detected by GC with electron capture detector. Of the amended, strictly oxic treatments, only one, in which 47% of the spiked (14)C-HCH was recovered as (14)CO(2), enhanced mineralization compared with an unamended treatment (in which 34% recovery was measured). Other oxic treatments involving higher amendment application rates or auxiliary carbon sources were inhibitory to mineralization. Thus, although HCH degradation occurs during the application of either oxic or cycled anoxic/oxic DARAMEND treatments, mineralization of gamma-HCH may be inhibited depending on the amendment and treatment protocol. PMID:15221667

  20. 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

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Garten, Charles T., Jr.

    2009-03-01

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

  3. 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.

  4. Mineral protection of soil carbon counteracted by root exudates

    SciTech Connect

    Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; Pett-Ridge, Jennifer; Weber, Peter K.; Kleber, Markus

    2015-03-30

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

  5. Mineral protection of soil carbon counteracted by root exudates

    DOE PAGESBeta

    Keiluweit, Marco; Bougoure, Jeremy J.; Nico, Peter S.; Pett-Ridge, Jennifer; Weber, Peter K.; Kleber, Markus

    2015-03-30

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

  6. 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

  7. 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...

  8. Stability of Soil Carbon Fractions - Aggregation Versus Mineral Association

    NASA Astrophysics Data System (ADS)

    Mueller, C. W.; Koegel-Knabner, I.

    2007-12-01

    Models that seek to describe the dynamics of soil organic C typically distinguish between two or more C fractions according to differences of biochemical and microbial degradation. The rates are a consequence of recalcitrance, accessibility and interactions. Soil aggregation is an important mechanism controlling the accessibility of substrates by microbes and enzymes and thus the dynamics of minerals bound C are interacting with soil aggregate dynamics. In this study we focused on C fractions isolated by particle size fractionation. The main objective of our study was to differentiate between C stabilization of soil fractions due to accessibility/aggregation or to association with minerals. For a detailed understanding of these processes and the sources of respired soil CO2 we combined the measurement of heterotrophic respiration, CO2-13C analyses and radiocarbon dating of the respired CO2 in a long-term laboratory mineralization experiment. For the experiment we took soil material from the A horizon of an Albic Luvisol under Norway spruce forest (Picea abies) in southern Germany. The air dried bulk soil (< 2000 µm) was subjected to ultrasonication (1st step 60 J ml-1; 2nd step 440 J ml-1) and separated according to particle size in three fractions: > 63 µm to 2000 µm - sand, > 6.3 µm to 63 µm - silt and silt/clay fraction < 6.3 µm - clay. Solid-state 13C-CPMAS NMR spectroscopy was used to analyze the composition of bulk soil and fractions. The incubation of the three fractions and the bulk soil was done for 250 days in triplicate at 20 degree Celsius and 70% of maximal water holding capacity. A relative enrichment of alkyl C and an increase of the alkyl / O/N-alkyl C ratios in the order of sand < silt < clay were observed by 13C-NMR. On a long term the sand fraction and the bulk soil showed a sustained C bioavailability. For the silt and clay fraction similar respiration rates and a low C bioavailability were detected. The recombined fractions (by

  9. Microprobe analyses of glasses and minerals from Luna-16 soil

    NASA Technical Reports Server (NTRS)

    Brown, R. W.; Harmon, R. S.; Jakes, P.; Reid, A. M.; Ridley, W. I.; Warner, J. L.

    1971-01-01

    Electron microprobe analyses are presented for nine elements in 250 glasses and 434 pyroxenes, eight elements in 113 olivines, and six elements in 354 feldspars, 35 spinels, and 159 ilmenites. All grains are from the 125-425 micron fraction of horizon A and horizon D soil from the Luna 16 sample. A norm is presented for each glass analysis and the structural formula is calculated for each mineral analysis.

  10. 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 ...

  11. 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 ...

  12. 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

  13. Distinct temperature sensitivity of soil carbon decomposition in forest organic layer and mineral soil

    PubMed Central

    Xu, Wenhua; Li, Wei; Jiang, Ping; Wang, Hui; Bai, Edith

    2014-01-01

    The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Here we determined Q10 in surface organic layer and subsurface mineral soil along an elevation gradient in a temperate forest ecosystem. Q10 was calculated by comparing the times required to respire a given amount of soil C at 15 and 25°C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.22–0.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation. This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. No clear trend of Q10 was found along the elevation gradient. Because the soil organic C pool of the organic layer in temperate forests is large, its higher temperature sensitivity highlights its importance in C cycling under global warming. PMID:25270905

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. 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

  17. 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

  18. 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

  19. 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.

  20. An underestimated methane sink in Arctic mineral soils

    NASA Astrophysics Data System (ADS)

    Oh, Y.; Medvigy, D.; Stackhouse, B. T.; Lau, M.; Onstott, T. C.; Jørgensen, C. J.; Elberling, B.; Emmerton, C. A.; St Louis, V. L.; Moch, J.

    2015-12-01

    Atmospheric methane has more than doubled since the industrial revolution, yet the sources and sinks are still poorly constrained. Though soil methane oxidation is the largest terrestrial methane sink, it is inadequately represented in current models. We have conducted laboratory analysis of mineral cryosol soils from Axel Heiberg Island in the Canadian high arctic. Microcosm experiments were carried out under varying environmental conditions and used to parameterize methane oxidation models. One-meter long intact soil cores were also obtained from Axel Heiberg Island and analyzed in the laboratory. A controlled core thawing experiment was carried out, and observed methane fluxes were compared to modeled methane fluxes. We find that accurate model simulation of methane fluxes needs to satisfy two requirements:(1) microbial biomass needs to be dynamically simulated, and (2) high-affinity methanotrophs need to be represented. With these 2 features, our model is able to reproduce observed temperature and soil moisture sensitivities of high affinity methanotrophs, which are twice as sensitive to temperature than the low affinity methanotrophs and are active under saturated moisture conditions. The model is also able to accurately reproduce the time rate of change of microbial oxidation of atmospheric methane. Finally, we discuss the remaining biases and uncertainties in the model, and the challenges of extending models from the laboratory scale to the landscape scale.

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. Simultaneous inhibition of carbon and nitrogen mineralization in a forest soil by simulated acid precipitation

    SciTech Connect

    Klein, T.M.; Novick, N.J.; Kreitinger, J.P.; Alexander, M.

    1984-06-01

    One method to simulate the long-term exposure of soil to acid rain involves the addition of single doses of concentrated acid. The inhibition of carbon mineralization accompanied by a stimulation of nitrogen mineralization may result from this severe, unnatural treatment. The present study was designed to determine whether the inhibition of carbon mineralization and the accompanying enhanced nitrogen mineralization would occur when soils are treated with more dilute acid for long periods of time, as takes place in nature.

  5. 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

  6. A short-term mineral amendment impacts the mineral weathering bacterial communities in an acidic forest soil.

    PubMed

    Lepleux, C; Uroz, S; Collignon, C; Churin, J-L; Turpault, M-P; Frey-Klett, P

    2013-09-01

    Mineral amendment (i.e. calcium, phosphorous, potassium and/or magnesium) is a management practice used in forestry to improve nutrient availability and recover soil fertility, especially in nutrient-poor forest ecosystems. However, whether this amendment can lead to modifications of the soil characteristics and an improvement in tree growth, and its impact on the soil bacterial communities, especially the mineral weathering bacterial communities, remains poorly documented. In this study, we investigated the short-term impact of a mineral amendment on the taxonomic and functional structure of the mineral weathering bacterial communities. To do this, a plantation of four-year old oak (Quercus petraea) trees amended with or without dolomite [CaMg(CO3)2] was established in the experimental forest site of Breuil-Chenue, which is characterized by an acidic soil and a low availability of calcium and magnesium. Three years after amendment, soil samples were used to isolate bacteria as well as to determine the soil characteristics and the metabolic potentials of these soil microbial communities. Based on a bioassay for quantifying the solubilisation of inorganic phosphorous, we demonstrate that the bacterial isolates coming from the non-amended bulk soil were significantly more efficient than those from the amended bulk soil. No difference was observed between the bacterial isolates coming from the amended and non-amended rhizospheres. Notably, the taxonomic analyses revealed a dominance of bacterial isolates belonging to the Burkholderia genus in both samples. Overall, our results suggest that the bioavailability of nutritive cations into soil impacts the distribution and the efficacy of mineral weathering bacterial communities coming from the soil but not those coming from the rhizosphere. PMID:23583355

  7. Sorption of triazoles to soil and iron minerals.

    PubMed

    Jia, Yu; Aagaard, Per; Breedveld, Gijs D

    2007-02-01

    Triazoles, additives in runway de-icers, are found in soil and groundwater at airport sites. To better understand the fate and transport of benzotriazole (BTA) and methylbenzotriazole (MeBTA) and to assess possible remediation options of contaminated groundwater, sorption to various soils and ferrous sorbents has been studied. In batch experiments, limited non-linear sorption of BTA to mineral subsoil from the Oslo International Airport, Gardermoen was observed. The sorption to soil could be described using a Freundlich isotherm. pH affected sorption of BTA to subsoil, although the effect was not strong. Increased sorption was observed to zerovalent iron (Fe(0)). MeBTA showed similar sorption behaviour as BTA although the sorption coefficient was generally higher. Sorption to Fe(0) seems to be controlled by multi-layer coverage. Our data suggest that sorption of triazoles to Fe(2)O(3) is negligible. However BTA sorption to 2-line and 6-line ferrihydrites showed strong sorption. The results demonstrate that triazoles are highly mobile in the subsurface environment, however zerovalent iron can be an effective medium for groundwater remediation. Without remediation, wide distribution of triazoles in the environment can be expected due to its extensive application and limited degradability. PMID:17123582

  8. 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...

  9. Reanalysis of boron adsorption on soils and soil minerals using the constant capacitance model

    SciTech Connect

    Goldberg, S.

    1999-08-01

    Inclusion of microscopic information improved the ability of the constant capacitance model to provide a quantitative description of B adsorption on various Al and Fe oxides, clay minerals, and arid-zone soils as a function of solution pH. The same set of B surface complexation reactions was used for all adsorbing surfaces. This study tests the ability of the model to describe B adsorption using surface configurations that had been observed experimentally. In the present model application, both trigonal, B(OH){sub 3}, and tetrahedral, B(OH){sub 4}{sup {minus}}, B surface complexes are postulated, consistent with experimental spectroscopic results. Boron surface complexation constants for Al and Fe oxides and kaolinites are not statistically significantly different from each other. Boron surface complexation constants for kaolinites are statistically significantly different from those for 2:1 clays and soils. Boron surface complexation constants for 2:1 clays and soils are not statistically significantly different from each other, reflecting the dominance of 2:1 clay minerals in B adsorption reactions in arid-zone soils. Average sets of B surface complexation constants provided adequate descriptions of B adsorption behavior on all adsorbents studied, indicating some predictive capability. The constant capacitance model was able to predict B adsorption behavior on additional arid-zone soils using the average set of B surface complexation constants.

  10. Predicting the impact of anaerobic microsites on soil organic matter mineralization rates in upland soils

    NASA Astrophysics Data System (ADS)

    Gee, K. E.; Keiluweit, M.; Denney, A.; Fendorf, S. E.

    2015-12-01

    Soils are a crucial component of the global carbon (C) cycle, representing a highly dynamic and large reservoir of C stored as soil organic matter (SOM). An important control on SOM residence time is microbial mineralization. While the impact of climactic and site-specific constraints on SOM mineralization rates are recognized, the role of oxygen limitations remains elusive. If oxygen consumption (via heterotrophic respiration) outpaces supply (via diffusion), anaerobic microsites can occur even within seemingly well-aerated upland soils. Under anaerobic conditions, SOM mineralization rates are expected to be slower due to metabolic constraints on microbial C oxidation. Process-based C cycling models have begun to incorporate the inhibiting effect of oxygen limitations by estimating anaerobic pore volume. However, such model predictions still lack experimental validation and research on environmental controls thus far has largely been focused on soil moisture. Here we aimed to determine the extent of anaerobic microsites within seemingly well-aerated upland soils experimentally and identify whether texture, SOM content, and microbial biomass can act as useful predictors in modeling frameworks. To this end, we monitored oxygen dynamics in soils spanning natural and artificial gradients in texture, SOM content and microbial biomass. Anaerobic microsites was visualized using a planar optode imaging system. Oxygen consumption rates were determined using gas chromatography, while oxygen diffusion rates were estimated based on porosity and pore-size distribution quantified by x-ray microtomography. Our results show that bulk oxygen concentrations ranged from 70% to as low as 20% saturation. However, all soils showed substantial micro-scale variability in oxygen concentrations, leading to the formation of anaerobic microsites even at modest moisture content. The extent of anaerobic microsites correlated with an overall reduction in SOM mineralization rates, and depended

  11. Effects of biochar on organic nitrogen mineralization of Northeast forest soil

    NASA Astrophysics Data System (ADS)

    Du, Siyao; Tao, Jun; Luo, Xianxiang

    2016-04-01

    These years,Biochar,as a new environmental functional material,received widespread attention of scholars both in China and abroad.Biochar is applied as a soil conditioner which is because it will improve the soil texture and increase plant yields. But the influence of nitrogen cycle while biochar is added to the forest soil is still controversial. This article takes forest soil as the object of research, aiming at learning the effects of different biochar on nitrogen mineralization of forest soil,and that in the case of different incubation temperature.The results show that it can reduce the net mineralization of soil organic nitrogen. That means the addition of biochar could suppress the mineralization of forest soil organic nitrogen.In a certain range,high temperature significantly facilitate to the mineralization of soill organic nitrogen while the existence of biochar also inhibits of that.

  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 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. ...

  16. 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

  17. Experimental warming effects on C and N mineralization in an Austrian mountain forest soil

    NASA Astrophysics Data System (ADS)

    Schütt, Marianne; Anzenhofer, Regina; Heuck, Christine; Hubach, Alena; Matzner, Egbert; Schindlbacher, Andreas; Borken, Werner

    2013-04-01

    An increase in soil temperatures substantially increases soil respiration rates as both processes are positively correlated. This has been demonstrated in a wide range of manipulative field and laboratory studies. However, the response of gross and net nitrogen (N) mineralization rates to enhanced soil temperatures has rarely been investigated. Previous studies ascribed the increased carbon (C) mineralization rates under elevated soil temperatures to enhanced microbial metabolic activity. We conduct a laboratory incubation experiment to determine gross and net N mineralization rates as well as CO2 production rates to test the hypothesis that elevated soil temperatures lead to an increase in gross and net N mineralization rates likewise as observed in C mineralization. We expect that gross N mineralization has a different temperature sensitivity than C mineralization. Soil samples were taken from the Achenkirch (Austria) soil warming experiment. Warmed and control plots were established in a mixed spruce-beech forest stand each with three replications in 2004. Soil temperature was enhanced in the warmed plots by 4°C above ambient temperature during the vegetation period. Due to anthropogenic deposition this site is highly N-saturated. Soil samples were taken in two depths (Oi/Oe layer and 0-10 cm). Gross ammonification and nitrification rates were measured by the 15N pool dilution technique, net N and CO2 production rates were determined in lab incubations over 12 weeks. First results of this study will be presented.

  18. Specific 137Cs-sorption capacity parameters of soils and mineral sorbents

    NASA Astrophysics Data System (ADS)

    Kruglov, S. V.; Anisimov, V. S.; Anisimova, L. N.; Aleksakhin, R. M.

    2008-06-01

    The selective sorption of cesium by some soils, minerals, and natural mineral sorbents was studied using new methodological and experimental approaches. It was found that the total capacity of two types of highly selective sorption sites significantly differing (by several orders of magnitude) in the selectivity coefficients of Cs-K ion exchange makes up 0.5-6% of the total capacity of the ion exchanger. The values of the radiocesium interception potential were determined for the studied soils and minerals.

  19. A novel approach to the examination of soil evidence: mineral identification using infrared microprobe analysis.

    PubMed

    Weinger, Brooke A; Reffner, John A; De Forest, Peter R

    2009-07-01

    Identification of minerals using the infrared microprobe with a diamond internal reflection objective is a rapid and reliable method for forensic soil examinations. Ninety-six mineral varieties were analyzed, and 77 were differentiated by their attenuated total reflection (ATR) spectra. Mineral grains may be mounted in oil for conventional polarized light microscope characterization and their ATR spectrum obtained with little or no interference by the liquid. This infrared microprobe method can be used to identify silicates, phosphates, nitrates, carbonates, and other covalent minerals; however, ionic minerals, metal oxide and sulfide minerals, and minerals with refractive indexes greater than diamond do not produce identifiable spectra, but the lack of a spectrum or one with high absorbance values does provide useful information. This research demonstrates the overall utility that infrared microprobe analysis brings mineral identification in soil evidence. PMID:19467138

  20. Potential net soil N mineralization and decomposition of glycine-13C in forest soils along an elevation gradient

    SciTech Connect

    Garten Jr, Charles T

    2004-09-01

    The objective of this research was to better understand patterns of soil nitrogen (N) availability and soil organic matter (SOM) decomposition in forest soils across an elevation gradient (235-1670 m) in the southern Appalachian Mountains. Laboratory studies were used to determine the potential rate of net soil N mineralization and in situ studies of {sup 13}C-labelled glycine were used to infer differences in decomposition rates. Nitrogen stocks, surface soil (0-5 cm) N concentrations, and the pool of potentially mineralizable surface soil N tended to increase from low to high elevations. Rates of potential net soil N mineralization were not significantly correlated with elevation. Increasing soil N availability with elevation is primarily due to greater soil N stocks and lower substrate C-to-N ratios, rather than differences in potential net soil N mineralization rates. The loss rate of {sup 13}C from labelled soils (0-20 cm) was inversely related to study site elevation (r = -0.85; P < 0.05) and directly related to mean annual temperature (+0.86; P<0.05). The results indicated different patterns of potential net soil N mineralization and {sup 13}C loss along the elevation gradient. The different patterns can be explained within a framework of climate, substrate chemistry, and coupled soil C and N stocks. Although less SOM decomposition is indicated at cool, high-elevation sites, low substrate C-to-N ratios in these N-rich systems result in more N release (N mineralization) for each unit of C converted to CO{sub 2} by soil microorganisms.

  1. [Effects of temperature on organic carbon mineralization in paddy soils with different clay content].

    PubMed

    Ren, Xiu-E; Tong, Cheng-Li; Sun, Zhong-Lin; Tang, Guo-Yong; Xiao, He-Ai; Wu, Jin-Shui

    2007-10-01

    An incubation test with three kinds of paddy soil (sandy loam, clay loam, and silty clay soils) in subtropical region was conducted at 10, 15, 20, 25 and 30 degrees C to examine the response of the mineralization of soil organic carbon (SOC) to temperature change. The results showed that during the period of 160 d incubation, the accumulative mineralized amount of SOC in sandy loam, clay loam, and silty clay soils at 30 degrees C was 3.5, 5.2 and 4.7 times as much as that at 10 degrees C, respectively. The mineralization rate was lower and relatively stable at lower temperatures (< or = 20 C), but was higher at the beginning of incubation and decreased and became stable as the time prolonged at higher temperatures (> or = 25 degrees C). During incubation, the temperature coefficient (Q10) of SOC mineralization in test soils fluctuated, with an average Q10 in sandy loam, clay loam, and silty clay soils being 1.92, 2.37 and 2.32, respectively. There was a positive exponential correlation between SOC mineralization constant k and temperature (P < 0.01), and the response of SOC mineralization to temperature change was in the order of clay loam soil > silty clay soil > sandy loam soil. PMID:18163305

  2. 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.

  3. 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 ...

  4. Nitrogen Mineralization in a Semiarid Silt Loam Soil in the Pacific Northwest

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mineralization of nitrogen from soil organic matter or plant residues can provide a substantial amount of nitrogen for crop growth. Microbial activity in a soil may be adversely affected by either very high or low soil water content. A field study was conducted to determine the affect of three...

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  7. 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.

  8. [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

  9. Nitrogen mineralization rates of the acidic, xeric soils of the New Jersey Pinelands: laboratory studies

    SciTech Connect

    Poovarodom, S.; Tate, R.L. III

    1988-05-01

    In a series of laboratory incubation studies, the authors evaluated the effects of temperature, moisture, and nitrogen amendment on nitrogen mineralization rates in the acidic Lakehurst and Atsion sands of the New Jersey Pinelands. The average potentially mineralizable nitrogen (N/sub 0/) values for the Lakehurst and Atsion sands were 87 and 94 ..mu..g/g, respectively. Mineralization constants (k) were 0.0501 and 0.0756/wk at 25 and 35/degrees/C, respectively, for the Lakehurst sand and were 0.0327 and 0.0452/wk for the Atsion sand. Maximum mineralization occurred at 35/degrees/C for both soils with Q/sub 10/ values ranging from 1.8 to 2.1. Optimal soil moisture tensions for nitrogen mineralization were between /minus/0.01 and /minus/0.03 MPa. A soil moisture tension of /minus/0.01 MPa reduced nitrogen mineralization with the Lakehurst sand, but not with the Atsion sand. Amendment of the soil with ammonium sulfate increased mineralization with the Atsion sand, but had no effect on the Lakehurst soil. Conversely, ammonium chloride amendment increased the nitrogen mineralization rates in the Lakehurst, but not the Atsion sand. Urea amendment inhibited nitrogen mineralization with both soils. No nitrate accumulation was observed in any of the nitrogen-amended samples.

  10. [Soil nitrogen mineralization and its prediction in winter wheat-summer maize rotation system].

    PubMed

    Ju, Xiaotang; Liu, Xuejun; Zhang, Fusuo

    2003-12-01

    The mineralization of soil nitrogen in winter wheat-summer maize growth season was studied with field experiment, and its prediction was made by interval leached aerial incubation combined with first-order dynamic model. The results showed that the amount of soil mineralized nitrogen had a large variation among years and crops. The soil nitrogen mineralization was lower in winter wheat growth season than in summer maize growth season, resulted in the yield increment of summer maize being not significant with increasing nitrogen fertilization rate. The amount of soil mineralized nitrogen occupied 31%-60% of the total nitrogen uptake by winter wheat and 62%-108% by summer maize. It was understandable why crop yield (especially summer maize) was not significantly response to applied nitrogen fertilizer. The amount of soil mineralized nitrogen decreased with increasing soil nitrogen supply. The mineralization was positive in normal nitrogen supply range(0-300 kg N.hm-2). The first order dynamic model could only predict the whole trend of mineralization in growth season, but could not reflect its variation in some growth stages. The role of the model was still important in view of the prediction of nitrogen mineralization before sowing. PMID:15031925

  11. 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.

  12. Fine-resolution multiscale mapping of clay minerals in Australian soils measured with near infrared spectra

    NASA Astrophysics Data System (ADS)

    Viscarra Rossel, R. A.

    2011-12-01

    Clay minerals are the most reactive inorganic components of soils. They help to determine soil properties and largely govern their behaviors and functions. Clay minerals also play important roles in biogeochemical cycling and interact with the environment to affect geomorphic processes such as weathering, erosion and deposition. This paper provides new spatially explicit clay mineralogy information for Australia that will help to improve our understanding of soils and their role in the functioning of landscapes and ecosystems. I measured the abundances of kaolinite, illite and smectite in Australian soils using near infrared (NIR) spectroscopy. Using a model-tree algorithm, I built rule-based models for each mineral at two depths (0-20 cm, 60-80 cm) as a function of predictors that represent the soil-forming factors (climate, parent material, relief, vegetation and time), their processes and the scales at which they vary. The results show that climate, parent material and soil type exert the largest influence on the abundance and spatial distribution of the clay minerals; relief and vegetation have more local effects. I digitally mapped each mineral on a 3 arc-second grid. The maps show the relative abundances and distributions of kaolinite, illite and smectite in Australian soils. Kaolinite occurs in a range of climates but dominates in deeply weathered soils, in soils of higher landscapes and in regions with more rain. Illite is present in varied landscapes and may be representative of colder, more arid climates, but may also be present in warmer and wetter soil environments. Smectite is often an authigenic mineral, formed from the weathering of basalt, but it also occurs on sediments and calcareous substrates. It occurs predominantly in drier climates and in landscapes with low relief. These new clay mineral maps fill a significant gap in the availability of soil mineralogical information. They provide data to for example, assist with research into soil

  13. Degradation and mineralization of atrazine by a soil bacterial isolate.

    PubMed Central

    Radosevich, M; Traina, S J; Hao, Y L; Tuovinen, O H

    1995-01-01

    An atrazine-degrading bacterial culture was isolated from an agricultural soil previously impacted by herbicide spills. The organism was capable of using atrazine under aerobic conditions as the sole source of C and N. Cyanuric acid could replace atrazine as the sole source of N, indicating that the organism was capable of ring cleavage. Ring cleavage was confirmed in 14CO2 evolution experiments with [U-14C-ring]atrazine. Between 40 and 50% of ring-14C was mineralized to 14CO2. [14C]biuret and [14C]urea were detected in spent culture media. Cellular assimilation of 14C was negligible, in keeping with the fully oxidized valence of the ring carbon. Chloride release was stoichiometric. The formation of ammonium during atrazine degradation was below the stoichiometric amount, suggesting a deficit due to cellular assimilation and metabolite-N accumulation. With excess glucose and with atrazine as the sole N source, free ammonium was not detected, suggesting assimilation into biomass. The organism degraded atrazine anaerobically in media which contained (i) atrazine only, (ii) atrazine and glucose, and (iii) atrazine, glucose, and nitrate. To date, this is the first report of a pure bacterial isolate with the ability to cleave the s-triazine ring structure of atrazine. It was also concluded that this bacterium was capable of dealkylation, dechlorination, and deamination in addition to ring cleavage. PMID:7887609

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  15. 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 storage—such 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

  16. X-Ray Digital Imaging Petrography of Lunar Mare Soils: Modal Analyses of Minerals and Glasses

    NASA Astrophysics Data System (ADS)

    Taylor, Lawrence A.; Patchen, Allan; Taylor, Dong-Hwa S.; Chambers, John G.; McKay, David 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 μm 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 ≅ 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]).

  17. 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]).

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

    SciTech Connect

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

    1990-09-01

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

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

    PubMed

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

    2004-01-01

    In situ incubation methods may help provide site-specific estimates of N mineralization from land-applied wastes. However, there are concerns about the reliability of the data generated by the various methods due to containment artifacts. We amended a sandy soil with either poultry manure, biosolids, or yard-waste compost and incubated the mixtures using four in situ methods (buried bags, covered cylinders, standard resin traps, and "new" soil-resin traps) and a conventional laboratory technique in plastic bags. Each incubation device was destructively sampled at 45-d intervals for 180 d and net N mineralization was determined by measuring the amount of inorganic N that accumulated in the soil or soil plus resin traps. Containment effects were evaluated by comparing water content of the containerized soil to a field-reference soil column. In situ incubation methods provided reasonable estimates of short-term (< 45 d) N mineralization, but long-term (> 45 d) mineralization data were not accurate due to a variety of problems specific to each technique. Buried bags and covered cylinders did not retain mineralized N due to water movement into and out of the containers. Neither resin method captured all of the mineralized N that leached through the soil columns, but the new soil-resin trap method tracked field soil water content better than all other in situ methods evaluated. With further refinement and validation, the new soil-resin trap method may be a useful in situ incubation technique for measuring net N mineralization rates of organic soil amendments. PMID:15224949

  20. 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).

  1. 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

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

    NASA Astrophysics Data System (ADS)

    Dietzen, Christiana; Harrison, Robert

    2016-04-01

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

  3. 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

  4. [Effects of Phyllostachys edulis expansion on soil nitrogen mineralization and its availability in evergreen broadleaf forest].

    PubMed

    Song, Qing-Ni; Yang, Qing-Pei; Liu, Jun; Yu, Ding-Kun; Fang, Kai; Xu, Pei; He, Yu-juan

    2013-02-01

    By the methods of space-time substitution and PVC tube closed-top in situ incubation, this paper studied the soil mineralized-N content, N mineralization rate, and N uptake rate in Phyllostachys edulis-broadleaf mixed forest (PBMF) formed by P. edulis expansion and its adjacent evergreen broadleaf forest (EBF) in Dagangshan Mountain of Jiangxi Province, China. There existed the same spatiotemporal variation trend of soil total mineralized-N (TMN) content between the two forests. The annual average N mineralization rate was slightly lower in PBMF than in EBF. In PBMF, soil N mineralization was dominated by ammonification; while in EBF, soil ammonification and nitrification were well-matched in rate, and soil nitrification was dominated in growth season (from April to October). The N uptake by the plants in PBMF and EBF in a year was mainly in the form of NH4+-N, but that in EBF in growth season was mainly in the form of NO3- -N. These findings indicated that the expansion of P. edulis into EBF could promote the ammonification of soil N, weakened soil nitrification and total N mineralization, and also, increased the NH4+-N uptake but decreased the NO3- -N and TMN uptake by the plants. PMID:23705376

  5. Studies of light noble gases in mineral grains from lunar soils: A status report

    NASA Technical Reports Server (NTRS)

    Wieler, R.; Etique, P.; Signer, P.

    1986-01-01

    Among the lunar soil constituents, monomineralic grains deserve special attention. Noble gases of carefully prepared mineral separates from lunar bulk soils were studied. The major results and conclusions of these investigations are summarized, in the context of both the regolith evolution and the history of the solar corpuscular radiation. With regard to the most abundant noble gas component in the regolith samples (the solar gases) the mineral grains have mainly two properties giving these particles among all soil constituents the best characteristics as sensors for solar gases, despite the fact, that the noble gas concentrations in a mineral separate are 10 to 60 times lower that those in a bulk sample of the same grain size. The first of these properties is the mineral dependent retentivity of the light gases He and Ne, the second property concerns the relatively short time during which a mineral grain acquires it solar gases. These two points are briefly discussed.

  6. 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

  7. 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 ...

  8. 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.

  9. THE INFLUENCE OF MINERAL REACTIONS ON THE ENVIRONMENTAL 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, however, these ...

  10. 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.

  11. Characteristics of nitrogen mineralization rates and controlling factors in forest soils in Japanese archipelago

    NASA Astrophysics Data System (ADS)

    Urakawa, R.; Ohte, N.; Shibata, H.; Isobe, K.; Oda, T.; Watanabe, T.; Fukuzawa, K.; Ugawa, S.; Hishi, T.; Enoki, T.; Tateno, R.; Fukushima, K.; Nakanishi, A.; Saigusa, N.; Yamao, Y.; Oyanagi, N.; Hattori, D.; Nakata, M.; Kenta, T.; Toda, H.; Inagaki, Y.; Hirai, K.

    2013-12-01

    1. Introduction The nitrogen (N) dynamics in forest soils in the Japanese archipelago varies widely because it extends for 3000 km and the climatic zone ranges from cool-temperate to subtropical region. Therefore, it is necessary to understand the soil N transformation characteristics and its controlling factors across a wide area because the changes in N dynamics due to the climate change are expected to differ from region to region. In this study, we selected more than 30 sites from across the Japanese archipelago and measured net rates of soil N mineralization and nitrification. Also, we measured the physical, chemical and biological properties of soil to clarify the controlling factors. 2. Materials and methods We established an experimental plot (20 * 20 m) at each site, and at each plot, five soil sampling locations were established. At each sampling location, mineral soil samples were collected from 0-10, 10-30, 30-50 cm in depth. Net and gross N mineralization and nitrification rate, soil pH(H2O), water soluble cation (Ca2+, Mg2+, K+, Na+, NH4+, Al3+), anion (Cl-, NO3-, SO42-), and organic carbon (WSOC) were measured. From the net N mineralization and nitrification rate measured by laboratory incubation at three different temperatures (15, 20, 25 °C), Q10min, Q10nit (Q10 of N mineralization and nitrification) and average net rate at 20 °C (N20min and N20nit) were calculated. 3. Results and discussion In most of the sites, net N mineralization and nitrification rates were higher in the shallower soil layers. N20min and N20nit ranged 0.01-3.23 and 0.00-3.00 mgN/kg/d, respectively and Q10min and Q10nit ranged 1.09-24.16 and 1.38-20.10 respectively. There was a pattern that low rates soil (N20 < 0.5 mgN/kg/d) had high Q10 values. Soils which had high N mineralization rates had also high nitrification rates. Soils with high N mineralization and nitrification rate were mostly located in the northern region (Hokkaido Island and Tohoku region) in Japan. This

  12. Prevalence and Contribution of Anaerobic Microsites to Carbon Mineralization in Upland Soils

    NASA Astrophysics Data System (ADS)

    Fendorf, S. E.; Keiluweit, M.; Gee, K. E.; Kleber, M.; Wanzek, T.; Nico, P. S.

    2015-12-01

    Soil organic matter (SOM) storage, or residence time, is dominantly controlled by the mineralization (oxidation) rate, which is affected by climatic factors (particularly temperature and rainfall) influencing microbial metabolic rates as well as SOM chemistry, mineral-organic associations, and physical protection. Variation in anaerobic respiratory pathways can further, and dramatically, impact carbon oxidation rates. Within the aggregated structure of soils, steep chemical gradients arise from the supply of oxygen and nutrients along macropores that are rapidly consumed (relative to supply) within the micropore domains of aggregate interiors. As a consequence of demand exceeding oxygen supply within soil aggregates and peds, an appreciable fraction of the soil volume may persist in an anaerobic state within upland, agriculturally productive system. Factors limiting oxygen diffusion and availability such as soil texture, soil moisture content, organic matter input, and aggregate size (soil structure) provide central controls on microbial carbon mineralization rates. Here, we combine laboratory studies with manipulations of field samples and in-field measurements to illustrate how soil structure and carbon availability interact to impose anaerobic conditions and associated respiratory constraints on organic matter mineralization rates and thus storage within soils.

  13. 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.

  14. 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

  15. Impact of activated carbon, biochar and compost on the desorption and mineralization of phenanthrene in soil.

    PubMed

    Marchal, Geoffrey; Smith, Kilian E C; Rein, Arno; Winding, Anne; Wollensen de Jonge, Lis; Trapp, Stefan; Karlson, Ulrich G

    2013-10-01

    Sorption of PAHs to carbonaceous soil amendments reduces their dissolved concentrations, limiting toxicity but also potentially biodegradation. Therefore, the maximum abiotic desorption of freshly sorbed phenanthrene (≤5 mg kg(-1)) was measured in three soils amended with activated carbon (AC), biochar or compost. Total amounts of phenanthrene desorbed were similar between the different soils, but the amendment type had a large influence. Complete desorption was observed in the unamended and compost amended soils, but this reduced for biochar (41% desorbed) and AC (8% desorbed). Cumulative amounts mineralized were 28% for the unamended control, 19% for compost, 13% for biochar and 4% for AC. Therefore, the effects of the amendments in soil in reducing desorption were also reflected in the extents of mineralization. Modeling was used to analyze key processes, indicating that for the AC and charcoal treatments bacterial activity did not limit mineralization, but rather desorption into the dissolved phase. PMID:23871817

  16. Cumulative effects of biochar, mineral and organic fertilizers on soil organic matter

    NASA Astrophysics Data System (ADS)

    Plaza, César; López-de-Sá, Esther G.; Gascó, Gabriel; Méndez, Ana; Zaccone, Claudio

    2016-04-01

    We investigated the effect of three consecutive annual applications of biochar at rates of 0 and 20 t ha-1, in a factorial combination with a mineral fertilizer (NPK and nitrosulfate) and two types of organic amendment (municipal solid waste compost and sewage sludge), on soil organic matter in a field experiment under Mediterranean conditions. Biochar increased significantly soil organic C content and C/N ratio. In biochar-amended soils, soil organic C increased significantly with the addition of municipal solid waste compost and sewage sludge. To capture organic matter protection mechanisms related to aggregation and mineral interaction, the soil samples will be fractionated into free (unprotected), intra-macroaggregate, intra-microaggregate, and mineral-associated organic matter pools, and the isolated fractions will be subjected to further chemical and spectroscopic analysis.

  17. 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…

  18. 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.

  19. 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...

  20. Raman spectroscopy of some complex arsenate minerals-implications for soil remediation.

    PubMed

    Frost, Ray L; Kloprogge, J Theo

    2003-10-01

    The application of spectroscopy to the study of contaminants in soils is important. Among the many contaminants is arsenic, which is highly labile and may leach to non-contaminated areas. Minerals of arsenate may form depending upon the availability of specific cations for example calcium and iron. Such minerals include carminite, pharmacosiderite and talmessite. Each of these arsenate minerals can be identified by its characteristic Raman spectrum enabling identification. PMID:14499841

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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...

  6. 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...

  7. Enhanced mineralization of polychlorinated biphenyls in soil inoculated with chlorobenzoate-degrading bacteria.

    PubMed Central

    Hickey, W J; Searles, D B; Focht, D D

    1993-01-01

    An Altamont soil containing no measurable population of chlorobenzoate utilizers was examined for the potential to enhance polychlorinated biphenyl (PCB) mineralization by inoculation with chlorobenzoate utilizers, a biphenyl utilizer, combinations of the two physiological types, and chlorobiphenyl-mineralizing transconjugants. Biphenyl was added to all soils, and biodegradation of 14C-Aroclor 1242 was assessed by disappearance of that substance and by production of 14CO2. Mineralization of PCBs was consistently greatest (up to 25.5%) in soils inoculated with chlorobenzoate degraders alone. Mineralization was significantly lower in soils receiving all other treatments: PCB cometabolizer (10.7%); chlorobiphenyl mineralizers (8.7 and 14.9%); and mixed inocula of PCB cometabolizers and chlorobenzoate utilizers (11.4 and 18.0%). However, all inoculated soils had higher mineralization than did the uninoculated control (3.1%). PCB disappearance followed trends similar to that observed with the mineralization data, with the greatest degradation occurring in soils inoculated with the chlorobenzoate-degrading strains Pseudomonas aeruginosa JB2 and Pseudomonas putida P111 alone. While the mechanism by which the introduction of chlorobenzoate degraders alone enhanced biodegradation of PCBs could not be elucidated, the possibility that chlorobenzoate inoculants acquired the ability to metabolize biphenyl and possibly PCBs was explored. When strain JB2, which does not utilize biphenyl, was inoculated into soil containing biphenyl and Aroclor 1242, the frequency of isolates able to utilize biphenyl and 2,5-dichlorobenzoate increased progressively with time from 3.3 to 44.4% between 15 and 48 days, respectively. Since this soil contained no measurable level of chlorobenzoate utilizers yet did contain a population of biphenyl utilizers, the possibility of genetic transfer between the latter group and strain JB2 cannot be excluded. PMID:8476293

  8. Mineralization of soil organic matter in two elevated CO2 by warming experiments in grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  9. 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.

  10. 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...

  11. Soil attributes, soybean mineral nutrition and yield in diverse crop rotations under no-till conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development of sustainable agricultural systems depends on understanding complex relationships between soil attributes, crop rotations, and crop yield. Objectives were to measure how soil chemical and physical attributes as well as soybean (Glycine max Merr.) stover dry weight and mineral concentra...

  12. 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...

  13. 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...

  14. 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 (...

  15. 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.

  16. 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...

  17. 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)...

  18. 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 (...

  19. 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...

  20. Mineralization of soil organic matter in biochar amended agricultural landscape

    NASA Astrophysics Data System (ADS)

    Chintala, R.; Clay, D. E.; Schumacher, T. E.; Kumar, S.; Malo, D. D.

    2015-12-01

    Pyrogenic biochar materials have been identified as a promising soil amendment to enhance climate resilience, increase soil carbon recalcitrance and achieve sustainable crop production. A three year field study was initiated in 2013 to study the impact of biochar on soil carbon and nitrogen storage on an eroded Maddock soil series - Sandy, Mixed, Frigid Entic Hapludolls) and deposition Brookings clay loam (Fine-Silty, Mixed, Superactive, Frigid Pachic Hapludolls) landscape positions. Three biochars produced from corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue, and switchgrass (Panicum virgatum L.) were incorporated at 9.75 Mg ha-1 rate (≈7.5 cm soil depth and 1.3 g/cm3 soil bulk density) with a rototiller. The changes in chemical fractionation of soil carbon (soluble C, acid hydrolyzable C, total C, and δ13 C) and nitrogen (soluble N, acid hydrolyzable N, total N, and δ14 N) were monitored for two soil depths (0-7.5 and 7.5 - 15 cm). Soluble and acid hydrolyzable fractions of soil C and N were influenced by soil series and were not significantly affected by incorporation of biochars. Based on soil and plant samples to be collected in the fall of 2015, C and N budgets are being developed using isotopic and non-isotopic techniques. Laboratory studies showed that the mean residence time for biochars used in this study ranged from 400 to 666 years. Laboratory and field studies will be compared in the presentation.

  1. 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

  2. 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

  3. Factors for Microbial Carbon Sources in Organic and Mineral Soils from Eastern United States Deciduous Forests

    NASA Astrophysics Data System (ADS)

    Stitt, C.; McFarlane, K. J.

    2013-12-01

    Forest soils represent a large portion of global terrestrial carbon; however, which soil carbon sources are used by soil microbes and respired as carbon dioxide (CO2) is not well known. This study will focus on characterizing microbial carbon sources from organic and mineral soils from four eastern United States deciduous forests using the unique radiocarbon tracer, 14C. Results from the dark incubation of the organic and mineral soils are heavily influenced by site characteristics when incubated at microbial optimal activity temperature. The sites with the most similarities are statically the same (p> 0.10). The sites with considerable differences in temperature, texture, and location are statically different concluding that site characteristics play a role in soil respiration.

  4. 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

  5. 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

  6. 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

  7. Mineralization of soil nitrogen in the presence of different metallic and organic solids

    SciTech Connect

    Smith, S.J.; Young, L.B.

    1984-01-01

    Mineralization of soil N was determined under aerobic and anaerobic conditions with four soils, three alfisols and one mollisol, for up to 24 weeks in the presence of various solids. These include: 1) metals--aluminum, brass, copper, iron, nickel, lead, stainless steel, tin, and zinc; 2) woods--cedar, pine, and redwood; and 3) other--latex paint and polyvinyl chloride. Presence of the metals, in general, had little or no effect, or depressed soil N mineralization, sometimes more than 50 percent. With a few exceptions, depression occurred mainly in the presence of brass, copper, iron, and zinc.

  8. 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

  9. 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

  10. 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.

  11. Using diffuse reflectance spectroscopy (DRS) for qualitative examination of iron minerals formed in a hydromorphic soil

    NASA Astrophysics Data System (ADS)

    Ringer, Marianna; Kiss, Klaudia; Németh, Tibor; Sipos, Péter; Szalai, Zoltán

    2016-04-01

    The method of diffuse reflectance spectroscopy (DRS) allows a large number of measurements in a rapid, non-destructive mode and does not require complex sample preparation. Based on the recorded wavelength-reflectance spectra, the simultaneous investigation of various soil parameters such as colour, mineral composition, organic matter and moisture content is possible. Several publications have presented results of the qualitative and quantitative analysis of iron-oxides containing trivalent iron (primarily hematite, goethite) by DRS. These iron minerals are usually formed in soils and sediments under surface conditions. Nevertheless in the case of hydromorhic soils water saturation can result iron mineral formation in the absence of oxygen. However, the related soil forming process leads to the appearance of ferrous iron-hydroxides (green rust) in the soil profile, in the literature no reference was found discussing the investigation of samples from reduced soil conditions by DRS method. Our aim was to reveal if DRS is suitable to perform qualitative characterization of both ferrous and ferric iron-oxide and hydroxide minerals of waterlogged soils. In the present study samples from a sandy meadow soil (calcic, gleyic Phaeozem ferric, arenic) profile were examined in the laboratory using an UV-Vis-NIR spectrophotometer with a diffuse reflectance attachement. Pedogenic iron minerals were characterized through spectral transformations and by comparison with spectrum database and literature data. The results were compared with data obtained from widely used routine methods. X-ray powder diffraction (XRD) for the determination of mineral composition, X-ray fluorescence spectroscopy (XRF) for total iron content and selective chemical dissolution (SCD) for the amorphous and crystalline iron content were presented. Although iron oxide minerals are usually at low concentrations (approx. 0,1%) or present in a poorly crystalline form, our results show that the presence of

  12. Carbon and nitrogen stocks and nitrogen mineralization in organically managed soils amended with composted manures.

    PubMed

    Romanyà, Joan; Arco, Noèlia; Solà-Morales, Ignasi; Armengot, Laura; Sans, Francesc Xavier

    2012-01-01

    The use of composted manures and of legumes in crop rotations may control the quality and quantity of soil organic matter and may affect nutrient retention and recycling. We studied soil organic C and N stocks and N mineralization in organically and conventionally managed dryland arable soils. We selected 13 extensive organic fields managed organically for 10 yr or more as well as adjacent fields managed conventionally. Organic farmers applied composted manures ranging from 0 to 1380 kg C ha yr and incorporated legumes in crop rotations. In contrast, conventional farmers applied fresh manures combined with slurries and/or mineral fertilizers ranging from 200 to 1900 kg C ha yr and practiced a cereal monoculture. Despite the fact that the application of organic C was similar in both farming systems, organically managed soils showed higher C and similar N content and lower bulk density than conventionally managed soils. Moreover, organic C stocks responded to the inputs of organic C in manures and to the presence of legumes only in organically managed soils. In contrast, stocks of organic N increased with the inputs of N or C in both farming systems. In organically managed soils, organic N stocks were less mineralizable than in conventional soils. However, N mineralization in organic soils was sensitive to the N fixation rates of legumes and to application rate and C/N ratio of the organic fertilizers. PMID:22751078

  13. 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, 48°00'N 2°50W) 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 1.1±0.2µmol.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 5.03±0.5µmol.m-2.s-1 at the end of July. In WDM soil, CO2 emissions were high at the end of spring (average of 7µmol.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

  14. 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 (35°12' N, 107°40' 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.

  15. 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

  16. 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.

  17. Impact of lead and sewage sludge on soil microbial biomass and carbon and nitrogen mineralization

    SciTech Connect

    Dar, G.H.

    1997-02-01

    Sewage sludge disposal on arable land is viewed as a method to reduce waste accumulation and to enrich soil fertility. However, such disposal can degrade soil ecosystems due to the presence of potentially harmful substances, such as heavy metals. Pb has assumed greater significance because currently its dispersal through anthropogenic activities has exceeded the inputs from natural sources by about 17 fold. Several soil variables such as texture, organic matter content, clay, cation exchange capacity, soil pH, and CaCO{sub 3} content influence the toxic effects of heavy metals on sol microbes and their activities. Microbes have an essential function in cycling of nutrients through mineralization activities. However, the addition of 375 and 1500 {mu}g Pb g{sup -1} soil in sandy loam and clay loam has been reported to cause a 15% decrease in soil microbial respiration. Contrarily, in an organic soil microbial respiration and enzyme activities were observed to remain unaltered by the addition of 1000 {mu}g Pb g{sup -1} soil. While the nitrification process in a sandy loam soil has been reported to be significantly inhibited at 100 {mu}g Pb g{sup -1} soil, the addition of similar amount of Pb to alluvial and clay loam had no effect on nitrification and ammonifying and nitrifying bacteria. This study assesses the effects of lead and sewages sludge on microbial biomass and mineralization processes in soils of varied texture and organic matter content. 17 refs., 4 tabs.

  18. Carbon and nitrogen pools and mineralization rates in boreal forest soil after stump harvesting

    NASA Astrophysics Data System (ADS)

    Kaarakka, Lilli; Hyvönen, Riitta; Strömgren, Monika; Palviainen, Marjo; Persson, Tryggve; Olsson, Bengt A.; Helmisaari, Heljä-Sisko

    2016-04-01

    The use of forest-derived biomass has steadily increased in the Finland and Sweden during the past decades. Thus, more intensive forest management practices are becoming more common in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting causes a direct removal of carbon (C) in the form of biomass from the stand and can cause extensive soil disturbance, which in turn can result in increased C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied at two different clear-felled Norway spruce (Picea abies) stands in Central Finland. The treatments were conventional stem-only harvesting combined with mounding (WTH) and stump harvesting (i.e. complete tree harvesting) combined with mounding (WTH+S). Logging residues were removed from all study sites. Soil samples down to a depth of 20 cm were systematically collected from the different soil disturbance surfaces (undisturbed soil, the mounds and the pits) 12-13 years after final harvest. Soil samples were incubated in the laboratory to determine the C and N mineralization rates. In addition, total C and N pools were estimated for each disturbance class and soil layer. Soil C and N pools were lower following stump harvesting, however, no statistically significant treatment effect was detected. Instead, C mineralization responses to treatment intensity was site-specific. C/N-ratio and organic matter content were significantly affected by harvest intensity. The observed changes in C and N pools appear to be related to the intrinsic variation of the surface disturbance and soil characteristics, and harvesting per se, rather than treatment intensity. Long-term studies are however needed to draw long-term conclusions whether stump harvesting significantly changes soil C and nutrient dynamics.

  19. Persistence of Mineral-Associated Soil Organic Carbon in European Soil Profiles

    NASA Astrophysics Data System (ADS)

    Mayer, A.; Schrumpf, M.; Trumbore, S.

    2014-12-01

    Soil Organic Carbon (SOC) is a heterogeneous mixture of components that are not equally biologically available, including light, plant derived material, dissolved organic carbon, and mineral-associated organic matter (MOM). Radiocarbon ages of bulk SOC average across this heterogeneity. Of particular interest is whether there are small amounts of very old OC (the so-called 'passive' pool) that can mask the fact that much of the OM is much younger. MOM has been shown to be older than the light fraction and DOC, but MOM is also a mixture of old and young material. This study seeks to clarify the quantity of C persisting on millennial time scales at different depths in the soil profile, and what factors allow this fraction to be more persistent than other fractions. We studied the fraction and age of C of the most chemically and physically stable fraction we could isolate from five European soils with differing land use, parent material, and soil type. First we isolated the MOM fraction by density, and then oxidized the MOM fraction with H2O2 to remove the labile C. The oxidation resistant residue was analyzed for C content and radiocarbon signature. The oxidation procedure removed 70-95% of the MOM fraction; the residue had a consistently older radiocarbon signature than the initial MOM, indicating that the C removed was younger than the bulk average. This stable fraction ranged from 100 radiocarbon years Before Present (BP) in the top 5 cm, to 10,000 years BP at the 30-40 cm depth. Non-crystalline iron concentrations were correlated with the absolute amount of SOC protected from oxidation, but not its proportion or age. With the exception of a tilled cropland site, all examined profiles exhibited a nearly linear depletion in radiocarbon signature with depth in both the protected and oxidizable MOM, confirming that the most chemically and physically stable C is oldest at the deepest point in a 50 cm profile. Ongoing work on this study will further elucidate how the

  20. Soil moisture influenced the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    Temperature sensitivity of SOC mineralization (Q10) determines how strong the feedback from global warming may be on the atmospheric CO2 concentration, thus understanding the factors influencing the interannual variation in Q10 is important to accurately estimate the local soil carbon cycle. In situ SOC mineralization was measured using an automated CO2 flux system (Li-8100) in long-term bare fallow soil in the Loess Plateau (35° 12' N, 107° 40' E) in Changwu, Shaanxi, China form 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m-2 y-1 (mean =253 g C m-2 y-1; CV =13%), annual Q10 ranged from 1.48 to 1.94 (mean =1.70; CV =10%), and annual soil moisture content ranged from 38.6 to 50.7% WFPS (mean =43.8% WFPS; CV =11%), which were mainly affected by the frequency and distribution of precipitation. Annual Q10 showed a negative quadratic correlation with soil moisture. In conclusion, understanding of the relationships between interannual variation in Q10 of SOC mineralization, soil moisture and precipitation is important to accurately estimate the local carbon cycle, especially under the changing climate.

  1. 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...

  2. 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

  3. 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

  4. 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.

  5. 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 40°C). The results suggested that accumulated ammonium nitrogen (NH4+-N) increased with increasing incubation time under all salinity concentrations. Higher temperatures and salinities significantly enhanced soil N mineralization except for a short-term (≈10 days) inhibiting effect found under 35‰ salinity. The incubation time, temperature, salinity and their interactions exhibited significant effects on N mineralization (P<0.001) except the interactive effect of salinity and temperature (P>0.05), while temperature exhibited the greatest effect (P<0.001). Meanwhile, N mineralization processes were simulated using both an effective accumulated temperature model and a one-pool model. Both models fit well with the simulation of soil N mineralization process in the coastal freshwater wetlands under a range of 30 to 40°C (R2 = 0.88-0.99, P<0.01). Our results indicated that an enhanced NH4+-N release with increasing temperature and salinity deriving from the projected global warming could have profound effects on nutrient cycling in coastal wetland ecosystems. PMID:24733366

  6. High Temperature and Salinity Enhance Soil Nitrogen Mineralization in a Tidal Freshwater Marsh

    PubMed Central

    Gao, Haifeng; Bai, Junhong; He, Xinhua; Zhao, Qingqing; Lu, Qiongqiong; Wang, Junjing

    2014-01-01

    Soil nitrogen (N) mineralization in wetlands is sensitive to various environmental factors. To compare the effects of salinity and temperature on N mineralization, wetland soils from a tidal freshwater marsh locating in the Yellow River Delta was incubated over a 48-d anaerobic incubation period under four salinity concentrations (0, 10, 20 and 35‰) and four temperature levels (10, 20, 30 and 40°C). The results suggested that accumulated ammonium nitrogen (NH4+-N) increased with increasing incubation time under all salinity concentrations. Higher temperatures and salinities significantly enhanced soil N mineralization except for a short-term (≈10 days) inhibiting effect found under 35‰ salinity. The incubation time, temperature, salinity and their interactions exhibited significant effects on N mineralization (P<0.001) except the interactive effect of salinity and temperature (P>0.05), while temperature exhibited the greatest effect (P<0.001). Meanwhile, N mineralization processes were simulated using both an effective accumulated temperature model and a one-pool model. Both models fit well with the simulation of soil N mineralization process in the coastal freshwater wetlands under a range of 30 to 40°C (R2 = 0.88–0.99, P<0.01). Our results indicated that an enhanced NH4+-N release with increasing temperature and salinity deriving from the projected global warming could have profound effects on nutrient cycling in coastal wetland ecosystems. PMID:24733366

  7. 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

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

    NASA Astrophysics Data System (ADS)

    Sánchez, L. F.; García-Miragaya, J.; Chacón, 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

  9. Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils.

    PubMed

    Zhang, Mingkui; Pu, Jincheng

    2011-01-01

    Four minerals, agricultural limestone (AL), rock phosphate (RP), palygorskite (PG), and calcium magnesium phosphate (CMP), were evaluated by means of chemical fractions of heavy metals in soils and concentrations of heavy metals in leachates from columns to determine their ability to stabilize heavy metals in polluted urban soils. Two urban soils (calcareous soil and acidic soil) polluted with cadmium, copper, zinc and lead were selected and amended in the laboratory with the mineral materials) for 12 months. Results indicated that application of the mineral materials reduced exchangeable metals in the sequence of Pb, Cd > Cu > Zn. The reduction of exchangeable fraction of heavy metals in the soils amended with different mineral materials followed the sequence of CMP, PG > AL > RP. Reductions of heavy metals leached were based on comparison with cumulative totals of heavy metals eluted through 12 pore volumes from an untreated soil. The reductions of the metals eluted from the calcareous soil amended with the RP, AL, PG and CMP were 1.98%, 38.89%, 64.81% and 75.93% for Cd, 8.51%, 40.42%, 60.64% and 55.32% for Cu, 1.76%, 52.94%, 70.00% and 74.12% for Pb, and 28.42%, 52.74%, 64.38% and 49.66% for Zn. Those from the acidic soil amended with the CMP, PG, AL, and RP were 25.65%, 68.06%, 78.01% and 79.06% for Cd, 26.56%, 49.64%, 43.40% and 34.68% for Cu, 44.44%, 33.32%, 61.11% and 69.44% for Pb, and 18.46%, 43.77%, 41.98% and 40.68% for Zn. The CMP and PG treatments were superior to the AL and RP for stabilizing heavy metals in the polluted urban soils. PMID:21793403

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

    PubMed Central

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

    2015-01-01

    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

  11. 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

  12. Mineralization of the Bacillus thuringiensis Cry1Ac endotoxin in soil.

    PubMed

    Accinelli, Cesare; Koskinen, William C; Becker, Joanna M; Sadowsky, Michael J

    2008-02-13

    Although a number of studies have been done describing the fate of Bacillus thuringiensis insecticidal endotoxins in soil, there is conflicting information on the persistence of this class of insecticidal toxins. This is partly due to methodological limitations in many of the previous studies. In the experiments reported here, 14C-labeled B. thuringiensis Cry1Ac endotoxin was used to study its mineralization in soil incubated under controlled conditions. Fifty-nine percent of the radiolabeled Cry1Ac was recovered as 14CO2 at the end of the 20 day incubation period. The addition of 4.5% corn residues stimulated mineralization of [14C]Cry1Ac toxin, and mineralization of glucose was 3.6 times faster than that of the Cry1Ac toxin, indicating that the soil was microbiologically and metabolically active. Because only low mineralization (approximately 6%) of the radiolabeled toxin was observed in autoclaved soil, the current findings indicate that microbial processes play a major role in the dissipation of the Cry1Ac endotoxin in soil. The results of this study suggest that there may be limited risk of the bioaccumulation of Cry1Ac in soil due to the eventual release of this insecticidal toxin by Bt-protected crops. PMID:18181567

  13. Organic matter protection as affected by the mineral soil matrix: allophanic vs. non-allophanic volcanic ash soils

    NASA Astrophysics Data System (ADS)

    Nierop, K. G. J.; Kaal, J.; Jansen, B.; Naafs, D. F. W.

    2009-04-01

    Volcanic ash soils (Andosols) contain the largest amounts of organic carbon of all mineral soil types. Chemical (complexes of organic matter with allophane, Al/Fe) and physical (aggregation) mechanisms are protecting the carbon from decomposition. While allophanic Andosols are dominated by short range order minerals such as allophane, imogolite and ferrihydrite, organic matter-Al/Fe complexes dominate non-allophanic Andosols. Consequently, chemical interactions between the mineral soil matrix and organic matter differ between these two soil types. This difference could potentially lead to different organic matter compositions. In this study, the organic matter of Ah horizons of an allophanic Andosol with a non-allophanic Andosol from Madeira Island is compared using analytical pyrolysis. Both volcanic soil types showed a relative decrease of lignin-derived pyrolysis products with depth, but this decrease was more pronounced in the allophanic Andosol. Polysaccharides were more abundant in the allophanic Ah horizon, particularly at lower depth, and this was also the case for the non-plant-derived N-containing polysaccharide chitin. Most likely, these biopolymers are adsorbed onto short range order minerals such as allophane and therefore were better protected in the allophanic Andosol. In addition, the higher chitin contents combined with the more pronounced lignin degradation suggests a higher fungal activity. Aliphatic pyrolysis products (n-alkenes/n-alkanes, fatty acids) were relatively more enriched in the non-allophanic Andosol. Lower microbial activity caused by the more acidic pH and higher levels of (toxic) aluminium are the most plausible reasons for the accumulation of these compounds in the non-allophanic Andosol. Although the allophanic and non-allophanic Andosol resembled each other in containing biopolymer groups of the same orders of magnitudes, in particular the contents of chitin and aliphatic compounds were distinctly affected by the differences in

  14. 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.

  15. Fly ash addition affects microbial biomass and carbon mineralization in agricultural soils.

    PubMed

    Nayak, A K; Kumar, Anjani; Raja, R; Rao, K S; Mohanty, Sangita; Shahid, Mohammad; Tripathy, Rahul; Panda, B B; Bhattacharyya, P

    2014-02-01

    The microbial biomass carbon (MBC) and carbon mineralization of fly ash (FA) amended soil at (0 %, 1.25 %, 2.5 %, 5 %, 10 % and 20 % FA; v/v) was investigated under laboratory conditions for 120 days at 60 % soil water-holding capacity and 25 ± 1°C temperature. The results demonstrated that soil respiration and microbial activities were not suppressed up to 2.5 % FA amendment and these activities decreased significantly at 10 % and 20 % FA treatment with respect to control. Application of 10 % and 20 % FA treated soils showed a decreasing trend of soil MBC with time; and the decrease was significant throughout the period of incubation. The study concluded that application of FA up to 2.5 % can thus be safely used without affecting the soil biological activity and thereby improve nutrient cycling in agricultural soils. PMID:24362819

  16. 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

  17. Degradation of plant cuticles in soils: impact on formation and sorptive ability of humin-mineral matrices.

    PubMed

    Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

    2015-05-01

    Plant cuticles are important precursors for soil organic matter, in particular for soil humin, which is considered an efficient sorbent for organic pollutants. In this study, we examined degradation and transformation of cuticles isolated from fruit and leaves in loamy sand and sandy clay loessial arid brown soils. We then studied sorption of phenanthrene and carbamazepine to humin-mineral matrices isolated from the incubated soils. Low degradation (22%) was observed for agave cuticle in a sandy clay soil system, whereas high degradation (68-78%) was obtained for agave cuticle in a loamy sand soil system and for loamy sand and sandy clay soils amended with tomato cuticle. During incubation, most of the residual organic matter was accumulated in the humin fraction. Sorption of phenanthrene was significantly higher for humin-mineral matrices obtained from soils incubated with plant cuticles as compared with soils without cuticle application. Sorption of carbamazepine to humin-mineral matrices was not affected by cuticle residues. Cooperative sorption of carbamazepine on humin-mineral matrices isolated from sandy clay soil is suggested. Sorption-desorption hysteresis of both phenanthrene and carbamazepine was lower for humin-mineral matrices obtained from soils incubated with plant cuticles as compared with nonamended soils. Our results show that cuticle composition significantly affects the rate and extent of cuticle degradation in soils and that plant cuticle application influences sorption and desorption of polar and nonpolar pollutants by humin-mineral matrices. PMID:26024265

  18. Soil sorption and leaching of active ingredients of Lumax® under mineral or organic fertilization.

    PubMed

    Pinna, Maria Vittoria; Roggero, Pier Paolo; Seddaiu, Giovanna; Pusino, Alba

    2014-09-01

    The study describes the soil sorption of the herbicide Lumax®, composed of S-metolachlor (MTC), terbuthylazine (TBZ), and mesotrione (MST), as influenced by mineral and organic fertilizers. The investigation was performed on a sandy soil of an agricultural area designated as a Nitrate Vulnerable Zone, where mineral and organic fertilizers were applied for many years. Two organic fertilizers, cattle manure and slurry, respectively, and a mineral fertilizer with a nitrification inhibitor, Entec®, were compared. According to the experiments, performed with a batch method, the sorption conformed to Freundlich model. The extent of sorption of Lumax® ingredients was closely related to their octanol-water partition coefficient Kow. The respective desorption was hysteretic. Leaching trials were carried out by using water or solutions of DOM or Entec® as the eluants. Only the elution with the mineral fertilizer promoted the leaching of Lumax® active ingredients. PMID:24997942

  19. Nitrogen mineralization rates of the acidic, xeric soils of the New Jersey Pinelands: field rates

    SciTech Connect

    Poovarodom, S.; Tate, R.L. III; Bloom, R.A.

    1988-04-01

    Using the buried-bag procedure, the authors quantified nitrogen mineralization rates in the xeric, acidic Lakehurst, and Atsion sands of the New Jersey Pine Barrens. Average annual nitrogen yields in the upper 15 cm for the Lakehurst and the Atsion sands were 38.4 and 53.0 kg N/ha, corresponding to 4.5 and 2.5% of the total nitrogen, respectively. Net nitrogen mineralization in both soils exhibited distinct seasonal patterns with maxima in summer and minimum rates in the winter. Nitrification accounted for only 5% of the total N mineralized in both soils. This is consistent with the finding of low populations of autotrophic nitrifiers in these soils.

  20. 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...

  1. Contribution of Soil Nitrogen Mineralization and Nitrification Pulses to Soil Nitrogen Availability and Nitrate Exports in a Mediterranean Catchment

    NASA Astrophysics Data System (ADS)

    Bernal, S.; Lupon, A.; Sabater, F.

    2015-12-01

    A good assessment of pulses of microbial nitrogen (N) supply is of paramount importance in helping understand the soil N cycle and catchment N exports in Mediterranean regions. Yet, the real contribution of N mineralization and nitrification pulses to soil N availability and catchment N exports remains unclear because most of the experiments have been performed on single forest ecosystem, while focusing on just few rainfall events. Over a year, we performed biweekly soil incubations to investigate patterns and controls of pulses of net N mineralization (NNM) and nitrification (NN) in three forests (riparian, evergreen oak and beech) coexisting within a Mediterranean headwater catchment. Further, we examined the influence of these pulses on soil N budgets and stream N loads. Within the catchment, riparian soils were hotspots of NNM and NN as they accounted for 30% of measured soil N supply, with median rates being multiple-fold higher than at the oak and beech forests. Pulses of NNM and NN generally occurred in spring immediately after large rainfall events (>20 mm). Moreover, high summer soil temperatures (>16ºC) promoted pulses of microbial activity at the riparian site. Although microbial pulses were restricted in time at all sites, they could contribute between 26-42% of the annual rates of NNM and NN. However, only NN pulses in the riparian site lead to disproportional increases in soil N availability and stream N loads, suggesting that these Mediterranean riparian soils could be a critical source of nitrate to the stream. Our study stresses that intensive monitoring is essential to capture hot moments of soil N processes, and thus to understand the relevance of microbial pulses on soil N biogeochemistry.

  2. 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

  3. 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

  4. 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

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

    PubMed

    Likar, M; Vogel-Mikuš, K; Potisek, M; Hančević, K; Radić, T; Nečemer, 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

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Zinyakova, Natalia; Semenov, Vyacheslav

    2016-04-01

    Warming, drying, wetting are the prevalent disturbing natural impacts that affect the upper layers of uncultivated and arable soils. The effect of drying-wetting cycles act as a physiological stress for the soil microbial community and cause changes in its structure, the partial death or lysis of the microbial biomass. The mobilization of the SOM and the stabilization of the potentially mineralizable components lead to change of mineralization potential in the soil. To test the effects of different moisture regime on plant growth and soil biological properties, plot experiment with the gray forest soil including trials with plants (corn) and bare fallow was performed. Different regimes of soil moisture (conditionally optimal, relatively deficient soil moisture and repeated cycles of drying-wetting) were created. Control of soil moisture was taken every two or three days. Gas sampling was carried out using closed chambers. Soil samples were collected at the end of the pot experiment. The potentially mineralizable content of soil organic carbon (SOC) was measured by biokinetic method based on (1) aerobic incubation of soil samples under constant temperature and moisture conditions during 158 days, (2) quantitation of C-CO2, and (3) fitting of C-CO2 cumulative curve by a model of first-order kinetic. Total soil organic carbon was measured by Tyrin's wet chemical oxidation method. Permanent deficient moisture in the soil favored the preservation of potentially mineralizable SOC. Two repeated cycles of drying-wetting did not reduce the potentially mineralizable carbon content in comparison with control under optimal soil moisture during 90 days of experiment. The emission loss of C-CO2 from the soil with plants was 1.4-1.7 times higher than the decrease of potentially mineralizable SOC due to the contribution of root respiration. On the contrary, the decrease of potentially mineralized SOC in the soil without plants was 1.1-1.2 times larger than C-CO2 emissions from the

  8. [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

  9. [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

  10. 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.

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

    PubMed

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

    2014-09-01

    This work investigated the impact of a clay mineral (bentonite) on the air oxidation of the solvent extractable organic matters (EOMs) and the PAHs from contaminated soils. EOMs were isolated from two coking plant soils and mixed with silica sand or bentonite. These samples, as well as raw soils and bentonite/soil mixtures, were oxidized in air at 60 and 100 °C for 160 days. Mineralization was followed by measuring the CO2 produced over the experiments. EOM, polycyclic aromatic compound (PAC), including PAH, contents were also determined. Oxidation led to a decrease in EOM contents and PAH concentrations, these diminutions were enhanced by the presence of bentonite. Transfer of carbon from EOM to insoluble organic matter pointed out a condensation phenomenon leading to a stabilization of the contamination. Higher mineralization rates, observed during the oxidation of the soil/bentonite mixtures, seem to indicate that this clay mineral had a positive influence on the transformation of PAC into CO2. PMID:24816462

  12. Sorption equilibria of vapor-phase organic pollutants on unsaturated soils and soil minerals. Final report, Mar 85-Mar 89

    SciTech Connect

    Lion, L.W.; Ong, S.K.; Linder, S.R.; Swager, J.L.; Schwager, S.J.

    1990-04-01

    Most groundwater pollutants are volatile organic compounds; however, there is relatively little understanding of the sorption reactions that control the transport and fate of organic vapors in the vadose zone. This investigation identified the physical/chemical properties of the soil matrix and organic vapors which control vapor-solid phase distribution. The dominant property which regulates vapor sorption in the unsaturated zone is the moisture content of the soil. Under very dry conditions, soil mineral/vapor interactions are regulated by specific surface area, indicating the dominance of a relatively non-specific physical adsorption process. However, at moisture contents exceeding an average surface coverage of four to eight layers of water, vapor uptake is controlled by partitioning reactions into soil moisture and soil organic matter.

  13. 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...

  14. Organic Matter Development and Turnover depending on Mineral Composition in an Artificial Soil Incubation Experiment

    NASA Astrophysics Data System (ADS)

    Pronk, G. J.; Heister, K.; Kogel-Knabner, I.

    2012-12-01

    Recent research indicates that minerals play an important role in the formation and stabilization of soil organic matter (SOM). However, it is difficult to determine the effect of mineral composition on SOM development in natural soils where mineral composition is usually not well defined and initial conditions are generally unknown. Therefore, we performed an incubation experiment with so-called "artificial soils" composed of mixtures of clean and well-defined model materials where the development of organic matter could be followed from known initial conditions. The artificial soils were composed of 8 different mixtures of quartz, illite, montmorillonite, ferrihydrite, boehmite and charcoal, manure as carbon substrate and a microbial inoculum extracted from a natural arable soil. These mixtures were incubated in the dark and sampled 4 times over a total incubation time of 18 months. The organic matter (OM) turnover during incubation was followed by measuring CO2 respiration and C and N contents and distribution over particle size fractions with time. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and acid hydrolysis were used to determine the development of OM composition. The artificial soil mixtures developed quickly into complex, aggregated, soil-like materials. CO2 respiration was the same for all artificial soil compositions, indicating that microbial degradation was probably limited by nutrient or substrate availability. With increasing incubation time, nitrogen-rich, proteinaceous material, became enriched in the smallest particle size fraction, indicating the accumulation of microbial debris. There was some difference in the distribution of hydrolysable and non-hydrolysable N and organic carbon after 3 months of incubation depending on the type of clay mineral and charcoal presence. However, the artificial soils developed towards more similar systems with increasing incubation time. The artificial soil incubation experiment provided a

  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

    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

  17. 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

  18. [Impacts of land-use types on soil C mineralization and temperature sensitivity of forests in Qianyanzhou, Jiangxi Province, China].

    PubMed

    Li, Jie; Wei, Xue-Hong; Chai, Hua; Wang, Ruo-Meng; Wang, Dan; He, Nian-Peng

    2014-07-01

    Decomposition of soil organic matter plays an important role in the regulation of carbon (C) cycles at ecosystem or regional scales, and is closely related to temperature, moisture, and land-use types. The influences of soil temperature, moisture, and land-use types on soil C mineralization in Citrus reticulata and Pinus elliottii forests were investigated at the Qianyanzhou Ecological Experiment Station, Chinese Academy of Sciences, by conducting incubation experiments at 5-level temperatures (5, 10, 15, 20 and 25 degrees C) and 3-level moistures (30%, 60% and 90% saturated soil moisture, SSM). The results showed that soil temperature, moisture, and land-use types had significant effects on soil C mineralization and they had significant interaction effects. Soil C mineralization was positively correlated with incubation temperature in the two forests, and the maximum of soil C mineralization was in the 60% SSM treatment. The accumulation of soil C mineralization was higher in the C. reticulata forest than in the P. elliottii forest under the same temperature and moisture conditions. The temperature sensitivity (Q10) of soil C mineralization was influenced by land-use type and soil moisture. Q10 increased with the increasing soil moisture in both C. reticulata and P. elliottii forests at incubation 7 and 42 d. Q10 in the C. reticulata forest was higher than in the P. elliottii forest in the same moisture level, and the deviation increased with the increasing soil moisture. The model including temperature and moisture could depict the response of soil C mineralization to temperature and moisture. Temperature and moisture together explained 79.9% -91.9% of the variation in soil C mineralization. PMID:25345040

  19. 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.

  20. 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.

  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. 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...

  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. 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 δ15N than non-mineral-associated OM. This implies that the δ15N 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 δ15N 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 δ15N in

  5. 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

  6. 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.

  7. Effect of three typical sulfide mineral flotation collectors on soil microbial activity.

    PubMed

    Guo, Zunwei; Yao, Jun; Wang, Fei; Yuan, Zhimin; Bararunyeretse, P; Zhao, Yue

    2016-04-01

    The sulfide mineral flotation collectors are wildly used in China, whereas their toxic effect on soil microbial activity remains largely unexplored. In this study, isothermal microcalorimetric technique and soil enzyme assay techniques were employed to investigate the toxic effect of typical sulfide mineral flotation collectors on soil microbial activity. Soil samples were treated with different concentrations (0-100 μg•g - 1 soil) of butyl xanthate, butyl dithiophosphate, and sodium diethyldithiocarbamate. Results showed a significant adverse effect of butyl xanthate (p < 0.05), butyl dithiophosphate, and sodium diethyldithiocarbamate (p < 0.01) on soil microbial activity. The growth rate constants k decreased along with the increase of flotation collectors concentration from 20.0 to 100.0 μg•g(-1). However, the adverse effects of these three floatation collectors showed significant difference. The IC 20 of the investigated flotation reagents followed such an order: IC 20 (butyl xanthate) > IC 20 (sodium diethyldithiocarbamate) > IC 20 (butyl dithiophosphate) with their respective inhibitory concentration as 47.03, 38.36, and 33.34 μg•g(-1). Besides, soil enzyme activities revealed that these three flotation collectors had an obvious effect on fluorescein diacetate hydrolysis (FDA) enzyme and catalase (CAT) enzyme. The proposed methods can provide meaningful toxicological information of flotation reagents to soil microbes in the view of metabolism and biochemistry, which are consistent and correlated to each other. PMID:26695417

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Barré, 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

  10. A general framework for modelling the vertical organic matter profile in mineral and organic soils

    NASA Astrophysics Data System (ADS)

    Braakhekke, Maarten; Ahrens, Bernhard

    2016-04-01

    The vertical distribution of soil organic matter (SOM) within the mineral soil and surface organic layer is an important property of terrestrial ecosystems that affects carbon and nutrient cycling and soil heat and moisture transport. The overwhelming majority of models of SOM dynamics are zero-dimensional, i.e. they do not resolve heterogeneity of SOM concentration along the vertical profile. In recent years, however, a number of new vertically explicit SOM models or vertically explicit versions of existing models have been published. These models describe SOM in units of concentration (mass per unit volume) by means of a reactive-transport model that includes diffusion and/or advection terms for SOM transport, and vertically resolves SOM inputs and factors that influence decomposition. An important assumption behind these models is that the volume of soil elements is constant over time, i.e. not affected by SOM dynamics. This assumption only holds if the SOM content is negligible compared to the mineral content. When this is not the case, SOM input or loss in a soil element may cause a change in volume of the element rather than a change in SOM concentration. Furthermore, these volume changes can cause vertical shifts of material relative to the surface. This generally causes material in an organic layer to gradually move downward, even in absence of mixing processes. Since the classical reactive-transport model of the SOM profile can only be applied to the mineral soil, the surface organic layer is usually either treated separately or not explicitly considered. We present a new and elegant framework that treats the surface organic layer and mineral soil as one continuous whole. It explicitly accounts for volume changes due to SOM dynamics and changes in bulk density. The vertical shifts resulting from these volume changes are included in an Eulerian representation as an additional advective transport flux. Our approach offers a more elegant and realistic

  11. [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

  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

  13. 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.

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

    PubMed

    Burgos, Pilar; Madejón, 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

  15. 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

  16. Nitrogen mineralization, immobilization, and nitrification following urea fertilization of a forest soil under field and laboratory conditions

    SciTech Connect

    Johnson, D.W.; Edwards, N.T.; Todd, D.E.

    1980-05-01

    Following a 200-kg urea-N/ha fertilization in a loblolly pine stand (Pinus taeda), soil mineral N levels (almost entirely NH/sub 4//sup +/) declined from 200 ppM 20 days after fertilization to < 10 ppM within 161 days. Similar patterns had been previously observed following urea fertilization in a Douglas-fir stand. After the decline in soil mineral N, 20% (40 ppM) of fertilizer N was mineralized within 4 weeks of aerobic incubation in the laboratory at 25/sup 0/C. Nitrogen mineralization in control soils did not occur after 7 weeks incubation.

  17. 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

  18. 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...

  19. 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...

  20. Draft Genome Sequence of Ensifer adhaerens M78, a Mineral-Weathering Bacterium Isolated from Soil.

    PubMed

    Wang, Yuanli; Chen, Wei; He, Linyan; Wang, Qi; Sheng, Xia-Fang

    2016-01-01

    Ensifer adhaerens M78, a bacterium isolated from soil, can weather potash feldspar and release Fe, Si, and Al from rock under nutrient-poor conditions. Here, we report the draft genome sequence of strain M78, which may facilitate a better understanding of the molecular mechanism involved in mineral weathering by the bacterium. PMID:27609930

  1. 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...

  2. 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 ...

  3. 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 ...

  4. Natural soil mineral nanoparticles are novel sorbents for pentachlorophenol and phenanthrene removal.

    PubMed

    He, Yan; Zeng, Fanfeng; Lian, Zhenghua; Xu, Jianming; Brookes, Philip C

    2015-10-01

    Natural soil montmorillonite and kaolinite nanoparticles (NPs) were tested as efficient sorbents for organic contaminant (OC) removal through mimicking their natural environmental dispersive states. Sorption of both mineral NPs decreased with increasing pH with ionizable pentachlorophenol (PCP), but increased with pH with non-ionizable phenanthrene (PHE), within the pH range of 4-10. In contrast, sorption decreased consistently for both PCP and PHE, as a function of increasing ion concentration (0.001-0.1 mol L(-1)). Sorption differences were likely caused by the electrolytic conditions dependent upon surface chemistry of OCs and mineral NPs. The results confirmed that the highly dispersive soil mineral NPs would prevail over both engineered NPs and their regular μm-sized colloids for OC removal, due to their ecological advantages and higher sorption properties. This finding provided a realistic assessment of the environmental function of soil natural minerals in water once they are released from soil into OC polluted aqueous systems. PMID:26005862

  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. Mineral composition and charcoal determine the bacterial community structure in artificial soils.

    PubMed

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

    2013-10-01

    To study the influence of the clay minerals montmorillonite (M) and illite (I), the metal oxides ferrihydrite (F) and aluminum hydroxide (A), and charcoal (C) on soil bacterial communities, seven artificial soils with identical texture provided by quartz (Q) were mixed with sterilized manure as organic carbon source before adding a microbial inoculant derived from a Cambisol. Bacterial communities established in artificial soils after 90 days of incubation were compared by DGGE analysis of bacterial and taxon-specific 16S rRNA gene amplicons. The bacterial community structure of charcoal-containing soils highly differed from the other soils at all taxonomic levels studied. Effects of montmorillonite and illite were observed for Bacteria and Betaproteobacteria, but not for Actinobacteria or Alphaproteobacteria. A weak influence of metal oxides on Betaproteobacteria was found. Barcoded pyrosequencing of 16S rRNA gene amplicons done for QM, QI, QIF, and QMC revealed a high bacterial diversity in the artificial soils. The composition of the artificial soils was different from the inoculant, and the structure of the bacterial communities established in QMC soil was most different from the other soils, suggesting that charcoal provided distinct microenvironments and biogeochemical interfaces formed. Several populations with discriminative relative abundance between artificial soils were identified. PMID:23289489

  7. 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 15°C, 25°C and 35°C. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. Exploring soil organic matter-mineral interactions: mechanistic insights at the nanometer and molecular length scales

    NASA Astrophysics Data System (ADS)

    Newcomb, C.; Qafoku, N. P.; Grate, J. W.; Hufschmid, R.; Browning, N.; De Yoreo, J. J.

    2015-12-01

    With elevated levels of carbon dioxide in the atmosphere due to anthropogenic emissions and disruption to the carbon cycle, the effects of climate change are being accelerated. Approximately 80% of Earth's terrestrial organic carbon is stored in soil, and the residence time of this carbon can range from hours to millenia. Understanding the dynamics of this carbon pool in the carbon cycle is crucial to both predicting climate and sustaining ecosystem services. Soil organic carbon is known to be strongly associated with high surface area clay minerals. The nature of these interactions is not well understood primarily due to the heterogeneity of soil, as much of the current knowledge relies on experiments that take a top-down approach using bulk experimental measurements. Our work seeks to probe physical, chemical, and molecular-level interactions at the organic-mineral interface using a bottom-up approach that establishes a model system where complexity can be built in systematically. By performing in situ techniques such as dynamic force spectroscopy, a technique where organic molecules can be brought into contact with mineral surfaces in a controlled manner using an atomic force microscope, we demonstrate the ability to mechanistically probe the energy landscape of individual organic molecules with mineral surfaces. We demonstrate the ability to measure the binding energies of soil-inspired organic functional groups (including carboxylic acid, amine, methyl, and phosphate) with clay and mineral surfaces as a function of solution chemistry. This effort can provide researchers with both guiding principles about carbon dynamics at the sub-nanometer length scale and insights into early aggregation events, where organic-mineral interactions play a significant role.

  13. 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

  14. The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces.

    PubMed

    Kebede, Mulu A; Bish, David L; Losovyj, Yaroslav; Engelhard, Mark H; Raff, Jonathan D

    2016-08-16

    Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces (Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert) and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. The magnitude of NO2-to-HONO conversion depends on the amount of Fe(2+) present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe(2+)(aq) present in thin films of water coating the surface, whereas in the range of pH 5-8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe(2+) followed by protonation of nitrite via surface Fe-OH2(+) groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas. PMID:27409359

  15. Calculating carbon mass balance from unsaturated soil columns treated with CaSO₄₋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. 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

  17. Application of microwave method for moisture determination of organic and organic-mineral soils

    NASA Astrophysics Data System (ADS)

    Kramarenko, V. V.; Nikitenkov, A. N.; Molokov, V. Yu; Shramok, A. V.; Pozdeeva, G. P.

    2016-03-01

    The problem of rapid drying arises when determining moisture, ash and organic matter content, as well as during many other soil tests. For highly-organic and organo-mineral peat soils the problem of advanced measurement of moisture content is of special importance, since after reweighing the dry sample increase in mass may be observed. The article examines the methods in determining the moisture content in peat and organic soils via microwave radiation, which will greatly speed up the process, simplify the complexity and cost of laboratory tests. The paper presents a detailed review of the methods determining moisture content in soils and characteristics, as well as application scope. The work contains the research results on moisture organic soils: drying in a microwave oven and the current domestic standards.

  18. A Combination of Biochar-Mineral Complexes and Compost Improves Soil Bacterial Processes, Soil Quality, and Plant Properties.

    PubMed

    Ye, Jun; Zhang, Rui; Nielsen, Shaun; Joseph, Stephen D; Huang, Danfeng; Thomas, Torsten

    2016-01-01

    Organic farming avoids the use of synthetic fertilizers and promises food production with minimal environmental impact, however this farming practice does not often result in the same productivity as conventional farming. In recent years, biochar has received increasing attention as an agricultural amendment and by coating it with minerals to form biochar-mineral complex (BMC) carbon retention and nutrient availability can be improved. However, little is known about the potential of BMC in improving organic farming. We therefore investigated here how soil, bacterial and plant properties respond to a combined treatment of BMC and an organic fertilizer, i.e., a compost based on poultry manure. In a pakchoi pot trial, BMC and compost showed synergistic effects on soil properties, and specifically by increasing nitrate content. Soil nitrate has been previously observed to increase leaf size and we correspondingly saw an increase in the surface area of pakchoi leaves under the combined treatment of BMC and composted chicken manure. The increase in soil nitrate was also correlated with an enrichment of bacterial nitrifiers due to BMC. Additionally, we observed that the bacteria present in the compost treatment had a high turnover, which likely facilitated organic matter degradation and a reduction of potential pathogens derived from the manure. Overall our results demonstrate that a combination of BMC and compost can stimulate microbial process in organic farming that result in better vegetable production and improved soil properties for sustainable farming. PMID:27092104

  19. A Combination of Biochar–Mineral Complexes and Compost Improves Soil Bacterial Processes, Soil Quality, and Plant Properties

    PubMed Central

    Ye, Jun; Zhang, Rui; Nielsen, Shaun; Joseph, Stephen D.; Huang, Danfeng; Thomas, Torsten

    2016-01-01

    Organic farming avoids the use of synthetic fertilizers and promises food production with minimal environmental impact, however this farming practice does not often result in the same productivity as conventional farming. In recent years, biochar has received increasing attention as an agricultural amendment and by coating it with minerals to form biochar–mineral complex (BMC) carbon retention and nutrient availability can be improved. However, little is known about the potential of BMC in improving organic farming. We therefore investigated here how soil, bacterial and plant properties respond to a combined treatment of BMC and an organic fertilizer, i.e., a compost based on poultry manure. In a pakchoi pot trial, BMC and compost showed synergistic effects on soil properties, and specifically by increasing nitrate content. Soil nitrate has been previously observed to increase leaf size and we correspondingly saw an increase in the surface area of pakchoi leaves under the combined treatment of BMC and composted chicken manure. The increase in soil nitrate was also correlated with an enrichment of bacterial nitrifiers due to BMC. Additionally, we observed that the bacteria present in the compost treatment had a high turnover, which likely facilitated organic matter degradation and a reduction of potential pathogens derived from the manure. Overall our results demonstrate that a combination of BMC and compost can stimulate microbial process in organic farming that result in better vegetable production and improved soil properties for sustainable farming. PMID:27092104

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

    NASA Astrophysics Data System (ADS)

    Zornoza, R.; Muñoz, 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 Apolobambás 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

  1. 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 Δ14C 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.

  2. [Soil nitrogen mineralization and primary productivity in Rhododendron aureum community of snowpacks in alpine tundra of Changbai Mountain].

    PubMed

    Zhang, Guo-chun; Liu, Qi-jing; Xu, Qian-qian; Liu, Yan

    2010-09-01

    Based on continuous observation of soil temperature and in situ incubation, this paper studied the effects of snow packs on soil temperature, soil nitrogen (N) mineralization, and primary productivity of Rhododendron aureum community alpine tundra in Changbai Mountain. During the snow-covered period of non-growth season (from last October to early May), test soil had an increasing N content, and accumulated sufficient mineralized N for plant growth in the coming year. The soil under snow packs in snow-covered period had a mean temperature -3.0 degrees C, and its N mineralization was more vigorous, with available N increased by 3.88 g x m(-2); while the soil with no snowpack had a mean temperature -7.5 degrees C, and the available N only increased by 1.21 g x m(-2). During growth season (from mid May to late August), soil N content decreased. In autumn when plants stopped growing, soil available N content tended to increase. In winter, the soil temperature under snowpacks kept at around 0 degrees C or a little lower, which promoted soil N mineralization, while that with no snowpack was in a frozen status. The difference in soil N mineralization was the key factor resulting in the higher primary productivity of snowpack Rh. aureum community and the driving force for the spatial variation of vegetation. PMID:21265136

  3. 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

  4. 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

  5. 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.

  6. Temperature and moisture responses to carbon mineralization in the biochar-amended saline soil.

    PubMed

    Sun, Junna; He, Fuhong; Zhang, Zhenhua; Shao, Hongbo; Xu, Gang

    2016-11-01

    This study assessed the effects of temperature and moisture on carbon mineralization (Cmin) in a saline soil system with biochar amendment. The dynamics of Cmin were monitored in a biochar-amended saline soil for 220days by incubation experiments under different conditions of temperature (15°C, 25°C and 35°C) and moisture (30%, 70% and 105% of the water-holding capacity). Results showed that as the incubation temperature rose, cumulative Cmin consistently increased in soil added with 0-4% biochar. The two-compartment model could well describe the dynamics of Cmin. The temperature rise increased the concentration of labile C in soil, but reduced the turnover time of labile and recalcitrant C pools and the value of temperature coefficient Q10. The response of Cmin to moisture was varying in soil amended with different levels of biochar. In the control treatment (soil alone), cumulative Cmin increased only when soil moisture was >105%. In the biochar treatments, however, 70% of water-holding capacity was optimal for Cmin, except for 2%-biochar treatment at 35°C. The findings highlight the necessity to consider the combined effects of soil moisture, temperature and the amount of biochar added for assessing Cmin in biochar-amended saline soils. PMID:27348703

  7. 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

  8. 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.

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

    PubMed

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

    2012-11-01

    The deep soil layer (below 100 cm) stores considerable soil organic carbon (SOC). We can reveal its stability and provide the basis for certification of the deep soil carbon sinks by studying the SOC mineralization in the deep soil layer. With the shallow soil layer (0-100 cm) as control, the SOC mineralization under the condition (temperature 15 degrees C, the soil water content 8%) of Black Locust forest in the deep soil layer (100-400 cm) of the hilly region of the Loess Plateau was studied. The results showed that: (1) There was a downward trend in the total SOC mineralization with the increase of soil depth. The total SOC mineralization in the sub-deep soil (100-200 cm) and deep soil (200-400 cm) were equivalent to approximately 88.1% and 67.8% of that in the shallow layer (0-100 cm). (2) Throughout the carbon mineralization process, the same as the shallow soil, the sub-deep and deep soil can be divided into 3 stages. In the rapid decomposition phase, the ratio of the mineralization or organic carbon to the total mineralization in the sub-deep and deep layer (0-10 d) was approximately 50% of that in the shallow layer (0-17 d). In the slow decomposition phase, the ratio of organic carbon mineralization to total mineralization in the sub-deep, deep layer (11-45 d) was 150% of that in the shallow layer (18-45 d). There was no significant difference in this ratio among these three layers (46-62 d) in the relatively stable stage. (3) There was no significant difference (P > 0.05) in the mineralization rate of SOC among the shallow, sub-deep, deep layers. The stability of SOC in the deep soil layer (100-400 cm) was similar to that in the shallow soil layer and the SOC in the deep soil layer was also involved in the global carbon cycle. The change of SOC in the deep soil layer should be taken into account when estimating the effects of soil carbon sequestration in the Hilly Region of the Loess Plateau, China. PMID:23323422

  10. 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.

  11. Ice nucleation by soil dusts: relative importance of mineral and biological components

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, Ben; Webb, Michael; Whale, Thomas; Atkinson, James; Baustian, Kelly; Malkin, Tamsin

    2013-04-01

    Dusts emitted from agricultural soils may represent a significant source of atmospheric particulates at mid-latitudes. Such dusts, which can be aerosolised by anthropogenic agricultural activities, have previously been estimated to be present in the atmosphere at sufficient number densities that they could potentially compete with other known ice nuclei. In contrast to soils from arid regions, such as the Sahara, fertile soils contain a larger fraction of biological material, which can lead to an enhancement in the ice nucleating ability of their associated dusts. However, considerable uncertainties remain regarding the relative efficacy of soil dust particles from fertile soils as IN. In particular, the relative contribution to the overall ice nucleating activity from both the biological and mineral components present remains unclear. Using a novel experimental methodology designed to increase sensitivity to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice nucleating activities of PM10 extracted from soils collected in England. By controlling droplet sizes, which ranged in volume from 10-12 to 10-6L, we have been able to characterise the ice active site densities in soils (estimated using a time-independent framework) at temperatures ranging from -5° C down to the homogeneous limit of freezing at ~ -36° C. To distinguish between biological and mineral IN in the soil dusts, we examined the effects of heat treatment and organic matter digestion with hydrogen peroxide on the ice nucleating activities of the soils. Both heat and H2O2 treatment reduced the ice nucleating ability of the soil dust particles at low supercoolings (T >-15° C) by up to two orders of magnitude, suggesting that the ice nucleating active sites are primarily biological in nature within this regime. However, below -15° C, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the

  12. 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

  13. 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.

  14. 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...

  15. Watershed-Scale Geochemical Inventory of Soils by Portable X-Ray Fluorescence

    NASA Astrophysics Data System (ADS)

    Beaudette, D. E.; Stupi, L. K.; Swarowsky, A.; O'Geen, A. T.; Chang, J. F.; Gallagher, B.

    2009-12-01

    Spatial databases of geochemical data are an excellent source of point-scale information on naturally occurring toxic elements (arsenic, selenium or radon), contamination from industrial processes (lead, mercury, or cesium), mineralogical variability, and the fate of toxic compounds (i.e. sorption of pesticides to iron oxyhydroxide minerals) in soil. Sample preparation time, safety concerns associated with HF or HNO3 acid dissolution, instrument availability, and cost are all common constraints that limit the scale at which new geochemical surveys can be conducted. We used a Thermo-Fisher Niton portable X-Ray fluorescence (XRF) meter to perform comparatively rapid geochemical surveys in soils of two (35 ha) watersheds. The watersheds have contrasting parent materials, one formed from metavolcanic rock and the other from granite. The X-Ray fluorescence inventory of genetic soil horizons (n=660) was used to identify trends in soil development and landscape processes. Since soil samples are usually sieved and ground for standard laboratory characterization, the additional time required to prepare samples for XRF analysis was minimal, approximately 2 minutes for sample preparation and 6 minutes for machine scan time per sample. Preliminary analysis of the resulting geochemical data show strong spatial trends in watershed- and hillslope-scale variability in weathering indices (FeCBD:FeTotal and K:Ti), inferred mineralogy (Si:Al, Si:Al+Fe), and geologic signatures (multivariate analysis of 20 common elements). Depth trends and spatial patterns were correlated with common terrain-shape indices (slope, upslope contributing area, surface curvatures, local prominence, etc.), degree of soil development, parent material, and hydrological conditions. For example, Si:Al was higher in soils with greater upslope contributing area, and in seasonally saturated soils (Fig 1). Our findings demonstrate that portable XRF technology is a promising new tool for rapid lab-based and in situ

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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 (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

  3. 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 f

  4. Is demineralization with dilute hydrofluoric acid a viable method for isolating mineral stabilized soil organic matter?

    NASA Astrophysics Data System (ADS)

    Sanderman, J.; Baldock, J.; Farrell, M.; Macreadie, P.; McGowan, J.

    2015-12-01

    While you might not be able to dispose of a body with hydrofluoric acid (HF), as fans of Breaking Bad know HF will break silicon-oxygen bonds. These dual properties make HF a powerful tool in investigations of soil organic matter (SOM). When a soil sample is treated with HF, any low molecular weight OM that was bound to mineral surfaces will be released into solution allowing study of the amount and composition of this stable SOM pool. In the work presented here, we take advantage of this property of HF to explore if different forms of SOM are becoming stabilized to mineral surfaces in terrestrial and marine environments. Difference spectra obtained from solid-state 13C NMR spectroscopic analysis of bulk and 10% HF treated soil samples suggest that in aerobic terrestrial environments alkyl-C and aryl-C compounds can dominate the mineral stabilized fraction. However, in anoxic coastal environments this fraction is dominated by O-alkyl C. Demineralization of soil samples with HF is often necessary for removing paramagnetic interferences and concentrating carbon prior to obtaining NMR spectra. The working assumption using dilute HF is that the resultant SOM chemistry determined by NMR spectroscopy has not been significantly biased by the HF treatment process. This assumption has been validated in several studies but also refuted in others. A second goal of this study was to revisit this critical assumption by looking at carbon loss and resulting 13C NMR chemistry from a diverse set of soils and organic materials using HF in 2% and 10% concentrations. We found that 10% HF resulted in slightly greater loss of C than 2% HF but in cases where a preferential shift in chemistry was observed it was observed in both the 2% and 10% treatments. The implications of both of these findings will be discussed in the context of understanding the sources, stability and potential loss mechanisms of mineral stabilized SOM.

  5. Minerals

    MedlinePlus

    ... your body needs in larger amounts. They include calcium, phosphorus, magnesium, sodium, potassium, chloride and sulfur. Your body needs just small amounts of trace minerals. These include iron, manganese, copper, iodine, zinc, cobalt, fluoride and selenium. The best way to ...

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

    PubMed

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

    2016-01-01

    To investigate the seasonal dynamics of soil organic carbon (SOC) mineralization in Xiaoxing'an Mountain, we incubated soil samples collected from virgin Korean pine forest and broad-leaved secondary forest in different seasons in the laboratory and measured the SOC mineralization rate and cumulative SOC mineralization (Cm). We employed simultaneous reaction model to describe C mineralization kinetics and estimated SOC mineralization parameters including soil easily mineralizable C (C1), potentially mineralizable C (C₀). We also analyzed the relations between Cm, C₁and their influencing factors. Results showed that the incubated SOC mineralization rate and Cm for 0-5 cm soil layer decreased from early spring to late autumn, while for 5-10 cm soil layer the seasonal variation was not statistically significant for both forest types. The C₁ in 0-5 and 5-10 cm soil layers varied from 42.92-92.18 and 19.23-32.95 mg kg⁻¹, respectively, while the C₀ in 0-5 and 5-10 cm soil layers varied from 863.92-3957.15 and 434.15-865.79 mg · kg⁻¹, respec- tively. Both C₁ and C₀ decreased from early spring to late autumn. The proportions of C₀ in SOC for two forest types were 0.74%-2.78% and 1.11%-1.84% in 0-5 and 5-10 cm soil layers, respectively, and decreased from early spring to late autumn, indicating that SOC tended to become more stable as a whole from spring to autumn. The Cm and C₀ were significantly positively correlated to in situ soil water content and hot water-extractable carbohydrate content, but were not correlated to in situ soil temperature and cool water-extractable carbohydrate content. We concluded that soil labile organic carbon, soil physical and chemical properties contributed to the seasonal dynamics of SOC mineralization in the forests. PMID:27228587

  7. 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

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

    NASA Astrophysics Data System (ADS)

    Merino, Carolina; Matus, Francisco; Fontaine, Sebastien

    2016-04-01

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

  9. 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

  10. Exchangeable and secondary mineral reactive pools of aluminium in coastal lowland acid sulfate soils.

    PubMed

    Yvanes-Giuliani, Yliane A M; Waite, T David; Collins, Richard N

    2014-07-01

    The use of coastal floodplain sulfidic sediments for agricultural activities has resulted in the environmental degradation of many areas worldwide. The generation of acidity and transport of aluminium (Al) and other metals to adjacent aquatic systems are the main causes of adverse effects. Here, a five-step sequential extraction procedure (SEP) was applied to 30 coastal lowland acid sulfate soils (CLASS) from north-eastern New South Wales, Australia. This enabled quantification of the proportion of aluminium present in 'water-soluble', 'exchangeable', 'organically-complexed', 'reducible iron(III) (oxyhydr)oxide/hydroxysulfate-incorporated' and 'amorphous Al mineral' fractions. The first three extractions represented an average of 5% of 'aqua regia' extractable Al and their cumulative concentrations were extremely high, reaching up to 4000 mg·kg(-1). Comparison of Al concentrations in the final two extractions indicated that 'amorphous Al minerals' are quantitatively a much more important sink for the removal of aqueous Al derived from the acidic weathering of these soils than reducible Fe(III) minerals. Correlations were observed between soil pH, dissolved and total organic carbon (DOC and TOC) and Al concentrations in organic carbon-rich CLASS soil horizons. These results suggest that complexation of Al by dissolved organic matter significantly increases soluble Al concentrations at pH values >5.0. As such, present land management practices would benefit with redefinition of an 'optimal' soil from pH ≥5.5 to ~4.8 for the preservation of aquatic environments adjacent to organic-rich CLASS where Al is the sole or principle inorganic contaminant of concern. Furthermore, it was observed that currently-accepted standard procedures (i.e. 1 M KCl extraction) to measure exchangeable Al concentrations in these types of soils severely underestimate exchangeable Al and a more accurate representation may be obtained through the use of 0.2 M CuCl2. PMID:24727041

  11. 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.

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

    PubMed

    Oliveira, Rafael S; Galvão, 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

  13. 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.

  14. 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.

  15. Isotopic investigations of dissolved organic N in soils identifies N mineralization as a major sink process

    NASA Astrophysics Data System (ADS)

    Wanek, Wolfgang; Prommer, Judith; Hofhansl, Florian

    2016-04-01

    Dissolved organic nitrogen (DON) is a major component of transfer processes in the global nitrogen (N) cycle, contributing to atmospheric N deposition, terrestrial N losses and aquatic N inputs. In terrestrial ecosystems several sources and sinks contribute to belowground DON pools but yet are hard to quantify. In soils, DON is released by desorption of soil organic N and by microbial lysis. Major losses from the DON pool occur via sorption, hydrological losses and by soil N mineralization. Sorption/desorption, lysis and hydrological losses are expected to exhibit no 15N fractionation therefore allowing to trace different DON sources. Soil N mineralization of DON has been commonly assumed to have no or only a small isotope effect of between 0-4‰, however isotope fractionation by N mineralization has rarely been measured and might be larger than anticipated. Depending on the degree of 15N fractionation by soil N mineralization, we would expect DON to become 15N-enriched relative to bulk soil N, and dissolved inorganic N (DIN; ammonium and nitrate) to become 15N-depleted relative to both, bulk soil N and DON. Isotopic analyses of soil organic N, DON and DIN might therefore provide insights into the relative contributions of different sources and sink processes. This study therefore aimed at a better understanding of the isotopic signatures of DON and its controls in soils. We investigated the concentration and isotopic composition of bulk soil N, DON and DIN in a wide range of sites, covering arable, grassland and forest ecosystems in Austria across an altitudinal transect. Isotopic composition of ammonium, nitrate and DON were measured in soil extracts after chemical conversion to N2O by purge-and-trap isotope ratio mass spectrometry. We found that delta15N values of DON ranged between -0.4 and 7.6‰, closely tracking the delta15N values of bulk soils. However, DON was 15N-enriched relative to bulk soil N by 1.5±1.3‰ (1 SD), and inorganic N was 15N

  16. 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

  17. Influence of soil properties on the toxicity of TiO₂ nanoparticles on carbon mineralization and bacterial abundance.

    PubMed

    Simonin, Marie; Guyonnet, Julien P; Martins, Jean M F; Ginot, Morgane; Richaume, Agnès

    2015-01-01

    Information regarding the impact of low concentration of engineered nanoparticles on soil microbial communities is currently limited and the importance of soil characteristics is often neglected in ecological risk assessment. To evaluate the impact of TiO2 nanoparticles (NPs) on soil microbial communities (measured on bacterial abundance and carbon mineralization activity), 6 agricultural soils exhibiting contrasted textures and organic matter contents were exposed for 90 days to a low environmentally relevant concentration or to an accidental spiking of TiO2-NPs (1 and 500mgkg(-1) dry soil, respectively) in microcosms. In most soils, TiO2-NPs did not impact the activity and abundance of microbial communities, except in the silty-clay soil (high OM) where C-mineralization was significantly lowered, even with the low NPs concentration. Our results suggest that TiO2-NPs toxicity does not depend on soil texture but likely on pH and OM content. We characterized TiO2-NPs aggregation and zeta potential in soil solutions, in order to explain the difference of TiO2-NPs effects on soil C-mineralization. Zeta potential and aggregation of TiO2-NPs in the silty-clay (high OM) soil solution lead to a lower stability of TiO2-NP-aggregates than in the other soils. Further experiments would be necessary to evaluate the relationship between TiO2-NPs stability and toxicity in the soil. PMID:25464292

  18. 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.

  19. 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

  20. 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

  1. 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

  2. Plants Rather than Mineral Fertilization Shape Microbial Community Structure and Functional Potential in Legacy Contaminated Soil

    PubMed Central

    Ridl, Jakub; Kolar, Michal; Strejcek, Michal; Strnad, Hynek; Stursa, Petr; Paces, Jan; Macek, Tomas; Uhlik, Ondrej

    2016-01-01

    Plant-microbe interactions are of particular importance in polluted soils. This study sought to determine how selected plants (horseradish, black nightshade and tobacco) and NPK mineral fertilization shape the structure of soil microbial communities in legacy contaminated soil and the resultant impact of treatment on the soil microbial community functional potential. To explore these objectives, we combined shotgun metagenomics and 16S rRNA gene amplicon high throughput sequencing with data analysis approaches developed for RNA-seq. We observed that the presence of any of the selected plants rather than fertilization shaped the microbial community structure, and the microbial populations of the root zone of each plant significantly differed from one another and/or from the bulk soil, whereas the effect of the fertilizer proved to be insignificant. When we compared microbial diversity in root zones versus bulk soil, we observed an increase in the relative abundance of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria or Bacteroidetes, taxa which are commonly considered copiotrophic. Our results thus align with the theory that fast-growing, copiotrophic, microorganisms which are adapted to ephemeral carbon inputs are enriched in the vegetated soil. Microbial functional potential indicated that some genetic determinants associated with signal transduction mechanisms, defense mechanisms or amino acid transport and metabolism differed significantly among treatments. Genetic determinants of these categories tend to be overrepresented in copiotrophic organisms. The results of our study further elucidate plant-microbe relationships in a contaminated environment with possible implications for the phyto/rhizoremediation of contaminated areas. PMID:27446035

  3. Plants Rather than Mineral Fertilization Shape Microbial Community Structure and Functional Potential in Legacy Contaminated Soil.

    PubMed

    Ridl, Jakub; Kolar, Michal; Strejcek, Michal; Strnad, Hynek; Stursa, Petr; Paces, Jan; Macek, Tomas; Uhlik, Ondrej

    2016-01-01

    Plant-microbe interactions are of particular importance in polluted soils. This study sought to determine how selected plants (horseradish, black nightshade and tobacco) and NPK mineral fertilization shape the structure of soil microbial communities in legacy contaminated soil and the resultant impact of treatment on the soil microbial community functional potential. To explore these objectives, we combined shotgun metagenomics and 16S rRNA gene amplicon high throughput sequencing with data analysis approaches developed for RNA-seq. We observed that the presence of any of the selected plants rather than fertilization shaped the microbial community structure, and the microbial populations of the root zone of each plant significantly differed from one another and/or from the bulk soil, whereas the effect of the fertilizer proved to be insignificant. When we compared microbial diversity in root zones versus bulk soil, we observed an increase in the relative abundance of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria or Bacteroidetes, taxa which are commonly considered copiotrophic. Our results thus align with the theory that fast-growing, copiotrophic, microorganisms which are adapted to ephemeral carbon inputs are enriched in the vegetated soil. Microbial functional potential indicated that some genetic determinants associated with signal transduction mechanisms, defense mechanisms or amino acid transport and metabolism differed significantly among treatments. Genetic determinants of these categories tend to be overrepresented in copiotrophic organisms. The results of our study further elucidate plant-microbe relationships in a contaminated environment with possible implications for the phyto/rhizoremediation of contaminated areas. PMID:27446035

  4. Nitrogen Mineralization of a Loam Soil Supplemented with Organic–Inorganic Amendments under Laboratory Incubation

    PubMed Central

    Abbasi, M. Kaleem; Khaliq, Abdul

    2016-01-01

    The quantification of nitrogen (N) supplying capacity of organic amendments applied to a soil is of immense importance to examine synchronization, N release capacity, and fertilizer values of these added materials. The aims of the present study was to determine the potential N mineralization and subsequent nitrification of separate and combined use of poultry manure (PM), wheat straw residues (WSR), and urea N (UN) applied to a loam soil incubated periodically over 140 days period. In addition, changes in total soil N and carbon contents were also monitored during the study. Treatments included: PM100, WSR100, PM50 + WSR50, UN100, UN50 + PM50, UN50 + WSR50, UN50 + PM25 + WSR25, and a control (unfertilized). All the amendments were applied on an N-equivalent basis at the rate of 200 mg N kg-1. Results indicated that a substantial quantity of N had been released from the added amendments into the soil mineral pool and the net cumulative N mineralized varied between 39 and 147 mg N kg-1, lowest in the WSR and highest in the UN50 + PM50. Significant differences were observed among the amendments and the net mineral N derived from a separate and combined use of PM was greater than the other treatments. The net cumulative N nitrified (NCNN) varied between 16 and 126 mg kg-1, highest in UN50 + PM50 treatment. On average, percentage conversion of added N into available N by different amendments varied between 21 and 80%, while conversion of applied N into NO3-–N ranged between 9 and 65%, and the treatment UN50 + PM50 displayed the highest N recovery. Urea N when applied alone showed disappearance of 37% N (N unaccounted for) at the end while application of PM and WSR with UN reduced N disappearance and increased N retention in the mineral pool for a longer period. Organic amendments alone or in combination with UN improved organic matter buildup and increased soil N concentration. These results demonstrate the existence of substantial amounts of N reserves present in PM

  5. Nitrogen Mineralization of a Loam Soil Supplemented with Organic-Inorganic Amendments under Laboratory Incubation.

    PubMed

    Abbasi, M Kaleem; Khaliq, Abdul

    2016-01-01

    The quantification of nitrogen (N) supplying capacity of organic amendments applied to a soil is of immense importance to examine synchronization, N release capacity, and fertilizer values of these added materials. The aims of the present study was to determine the potential N mineralization and subsequent nitrification of separate and combined use of poultry manure (PM), wheat straw residues (WSR), and urea N (UN) applied to a loam soil incubated periodically over 140 days period. In addition, changes in total soil N and carbon contents were also monitored during the study. Treatments included: PM100, WSR100, PM50 + WSR50, UN100, UN50 + PM50, UN50 + WSR50, UN50 + PM25 + WSR25, and a control (unfertilized). All the amendments were applied on an N-equivalent basis at the rate of 200 mg N kg(-1). Results indicated that a substantial quantity of N had been released from the added amendments into the soil mineral pool and the net cumulative N mineralized varied between 39 and 147 mg N kg(-1), lowest in the WSR and highest in the UN50 + PM50. Significant differences were observed among the amendments and the net mineral N derived from a separate and combined use of PM was greater than the other treatments. The net cumulative N nitrified (NCNN) varied between 16 and 126 mg kg(-1), highest in UN50 + PM50 treatment. On average, percentage conversion of added N into available N by different amendments varied between 21 and 80%, while conversion of applied N into NO3 (-)-N ranged between 9 and 65%, and the treatment UN50 + PM50 displayed the highest N recovery. Urea N when applied alone showed disappearance of 37% N (N unaccounted for) at the end while application of PM and WSR with UN reduced N disappearance and increased N retention in the mineral pool for a longer period. Organic amendments alone or in combination with UN improved organic matter buildup and increased soil N concentration. These results demonstrate the existence of substantial amounts of N reserves present

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

    NASA Astrophysics Data System (ADS)

    Mercier Quideau, S.; Oh, S.; Paré, 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.

  7. 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.

  8. 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...

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. Effect of potassium salts and distillery effluent on carbon mineralization in soil.

    PubMed

    Chandra, Suresh; Joshi, H C; Pathak, H; Jain, M C; Kalra, N

    2002-07-01

    Distillery effluent, a rich source of potassium, is used for irrigation at many places in the world. A laboratory experiment was conducted to study the influence of potassium salts present in post-methanation distillery effluent (PME) along with two other salts, KCl and K2SO4, on mineralization of carbon in soil. PME oxidized with H2O2, raw PME, KCl and K2SO4 solutions containing K equivalent to 10%, 20%, 40% and 100% of K present in PME were added to the soil separately, maintaining four replications for each treatment and control. Addition of salts up to a certain concentration stimulated C mineralization but a decline was noticed at higher concentrations. All the levels of salts caused higher CO2 evolution than the control suggesting that the presence of K salts enhanced the microbial activity resulting in increased CO2 evolution. The influence of K2SO4 was significantly higher than KCl in stimulating C mineralization in soil. Oxidized effluent had a higher stimulating effect than inorganic salts, showing the influence of other salts accompanying K in the PME. Raw PME, which contained excess organic C, increased CO2 evolution even at the highest salt level (100% PME) signifying the effect of added C on alleviating the salt stress on microbial activity. PMID:12094803

  13. Adsorption of iron cyanide complexes onto clay minerals, manganese oxide, and soil.

    PubMed

    Kang, Dong-Hee; Schwab, A Paul; Johnston, C T; Banks, M Katherine

    2010-09-01

    The adsorption characteristics of an iron cyanide complex, soluble Prussian blue KFe(III)[Fe(II)(CN)(6)], were evaluated for representative soil minerals and soil at pH 3.7, 6.4 and 9.7. Three specimen clay minerals (kaolinite, montmorillonite, and illite), two synthesized manganese oxides (birnessite and cryptomelane), and a Drummer soil from Indiana were used as the adsorbents. Surface protonation of variable charge sites increased with decreasing pH yielding positively charged sites on crystal edges and enhancing the attractive force between minerals and iron cyanide complexes. Anion adsorption on clays often is correlated to the metal content of the adsorbent, and a positive relationship was observed between iron or aluminum content and Prussian blue adsorption. Illite had high extractable iron and adsorbed more ferro-ferricyande anion, while kaolinite and montmorillonite had lower extractable iron and adsorbed less. However, less pH effect was observed on the adsorption of iron cyanide to manganese oxides. This may due to the manganese oxide mediated oxidation of ferrocyanide [Fe(II)(CN)(6)(4-)], to ferricyanide [Fe(III)(CN)(6)(3-)], which has a low affinity for manganese oxides. PMID:20665323

  14. 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.

  15. Atmospheric ice nucleation by fertile soil dusts particles: Relative importance of mineral and biological components

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, B. J.; Malkin, T. L.; Webb, M. E.; Whale, T. F.; Atkinson, J. D.; Baustian, K. J.

    2013-05-01

    Dusts emitted from agricultural soils may represent a significant source of atmospheric particulates at mid-latitudes. Such dusts, which can be aerosolised by anthropogenic agricultural activities, have previously been estimated to be present in the atmosphere at sufficient number densities that they could potentially compete with other known ice nuclei (IN). In contrast to soils from arid regions, such as the Sahara, fertile soils contain a larger fraction of biological material, which can lead to an enhancement in the ice nucleating ability of their associated dusts. However, considerable uncertainties remain regarding the relative efficacy of soil dust particles from fertile soils as IN. Using an experimental methodology designed to increase sensitivity to a wide range of ice nucleation efficiencies, we have characterized the immersion mode ice nucleating activities of sub 11 μm particles extracted from surface soils collected in four locations around England. By using a variety of droplet sizes, from pico-to micro-litre, we have been able to characterize the ice active site densities in soils (estimated using a time-independent framework) at temperatures ranging from -5°C down to the homogeneous limit of freezing at ˜ -36°C. At temperatures below -15°C, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts becomes increasingly important in the initiation of the ice phase at large supercoolings. Conversely, above -15°C we find that the ice nucleating activity of the soils dusts was larger than expected from the mineral composition of the soils. The sites responsible for this high temperature ice nucleating activity were sensitive to heat treatment and digestion with hydrogen peroxide, suggesting that they are biological in origin. We conclude that although only being a relatively minor contributor to the global atmospheric dust burden, the

  16. [Effects of long-term fertilization and fallowing on soil nitrogen mineralization and exogenous NO3(-) -N transformation].

    PubMed

    Ai, Na; Zhou, Jian-Bin; Yang, Xue-Yun; Liang, Bin

    2008-09-01

    Soil samples were collected from a 17-year fertilization experiment site in southern Loess Plateau to study the effects of different fertilizations and fallowing on the characteristics of soil nitrogen mineralization, and the transformation of exogenous NO3(-) -N in sterilized and non-sterilized soil samples. The results showed that a combined application of manure and chemical NPK and long-term fallowing increased the contents of soil organic matter, total N, and mineralized N, as well as the N mineralization rate significantly, compared with the control. Applying chemical NPK increased soil inorganic N content, but had less effects on the contents of soil organic matter, total N and mineralized N, as well as the N mineralization rate. Autoclaved sterilization resulted in a significant increase of soil NH4(+) -N content, while soil NO3(-) -N content remained relatively constant whether sterilization or not, suggesting that under the conditions of our incubation, abiotic and biological factors had no significant effects on the transformation of exogenous NO3 (-) -N. PMID:19102306

  17. 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

  18. Clay Mineralogy: The clay mineral composition of soils and clays is providing an understanding of their properties.

    PubMed

    Grim, R E

    1962-03-16

    The structures of the clay minerals are reasonably well known, but greater detail and more precision are needed if the properties of clays and soils are to be fully understood. For example, the selective adsorptive and catalytic properties and the reaction with organic materials vary with the character of the clay mineral, but the structural factors that control such properties are not well understood. Research is urgently needed on the structure of pure clay minerals and on the reactions of pure clay minerals with organic and inorganic materials. Much past research on clay-mineral reactions has little fundamental value because the clay that was used was composed of a mixture of minerals which were not well characterized. It is not a simple matter to find pure samples of many of the clay minerals, and to a considerable extent progress depends on finding such pure minerals or preparing them in the laboratory. PMID:17816101

  19. 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.

  20. 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.; LéOn, 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 16°N to 38°N and from 19°W to 40°E 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

  1. Maxwell-Wagner relaxation in common minerals and a desert soil at low water contents

    NASA Astrophysics Data System (ADS)

    Arcone, Steven A.; Boitnott, Ginger E.

    2012-06-01

    Penetration of 100- to 1000-MHz ground-penetrating radar (GPR) signals is virtually non-existent in arid and desert soils despite their low water content and moderate conductivity, the latter of which cannot explain the loss. Under the hypothesis that strong dielectric relaxation supplements DC conductivity to cause high intrinsic attenuation rates, we compared the complex permittivity of a desert soil sample with that of controlled samples of quartz, feldspars, calcite, coarse and crystallite gypsum, kaolinite and montmorillonite. The soil had 80% quartz, 10% feldspars and 10% gypsum by weight, with the latter composed of crystallites and crustations. All samples had 4-7% volumetric water content. We measured permittivity most accurately from 1.6 MHz to 4 GHz with Fourier Transform time domain reflectometry, and used grain sizes less than 53 μm. All samples show low-frequency dispersion with the soil, gypsum crystallites and montmorillonite having the strongest below 100 MHz, the highest attenuation rates, and conductivity values unable to account for these rates. The soil rate exceeded 100 dB m- 1 by 1 GHz. Through modeling we find that a broadened relaxation centered from 2 to 16 MHz sufficiently supplements losses caused by conductivity and free water relaxation to account for loss rates in all our samples, and accounts for low-frequency dispersion below 1 GHz. We interpret the relaxation to be of the Maxwell-Wagner (MW) type because of the 2- to 16-MHz values, relaxation broadening, the lack of salt, clay and magnetic minerals, and insufficient surface area to support adsorbed water. The likely MW dipolar soil inclusions within the predominantly quartz matrix were gypsum particles coated with water containing ions dissolved from the gypsum, and the conducting water layers themselves. The inclusions for the monomineralic soils were likely ionized partially or completely water-filled interstices, and partially filled galleries for the montmorillonite. The low

  2. 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.

  3. 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.

  4. Stabilization of organic matter in soils: role of amorphous mineral phases

    NASA Astrophysics Data System (ADS)

    Zewde Tamrat, Wuhib; Rose, Jérôme; Levard, Clément; Chaurand, Perrine; Basile-Doelsch, Isabelle

    2016-04-01

    Soil organic matter (SOM) globally contributes the largest portion of continental carbon stock. One major issue concerning this large C pool includes its instability by mineralization and erosion due to land use. The main hypothesis of this work is that physicochemical stabilization of SOM is mainly driven by interactions of organic compounds, not with mineral surfaces as classically considered, but with amorphous polymers continuously formed by the alteration of soil minerals(1-3). Our objective is to understand how nano-organomineral complexes (nCOMx) are structured at the nanoscale, assess mechanisms of their formation, and quantify the effects of their occurrence on SOM turnovers. Due to inherent high complexity of natural samples, our methodology is based on the formation of nCOMx from both synthetic systems and natural mineral-weathered components. For the mineral component, biotite (from Bancroft, Canada) was selected. For the organic component, 3,4-Dihydroxy-L-phenylalanine, an amino acid with hydroxyl (pKa=9.95), carboxyl (pKa=2,58), amino (pKa=9,24) and an aromatic functions was chosen. The methodology aimed at developing conditions that generate biotite dissolution and nCOMx precipitation. The second step of the experiment consisted of the precipitation of nCOMx by slowly increasing pH over 3 to 12 hours of hydrolysis. Three final pH conditions were tested (4.2, 5 and 7) with Metal/Carbon ratios of 0.01, 0.1, 1, 10 and 'No Carbon'. The first results of dissolution rates and congruency, AFM imaging, ICPMS, HR-TEM and XRD as well as XAS characterizations (transmission and florescence mode at the Fe K-edge) of nCOMx will be presented. Experiments and analysis techniques were designed to study these synthetic phases with regard to Si, Al, Fe and OM proportions to increase the OM proportion (as in natural soil phases) and also increase the stability of the OM phase (as in increased residence time of OM in the soil). We will focus particularly on the Fe state

  5. [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

  6. 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

  7. Effects of belowground litter addition, increased precipitation and clipping on soil carbon and nitrogen mineralization in a temperate steppe

    NASA Astrophysics Data System (ADS)

    Ma, L.; Guo, C.; Xin, X.; Yuan, S.; Wang, R.

    2013-11-01

    Soil carbon (C) and nitrogen (N) cycling are sensitive to changes in environmental factors and play critical roles in the responses of terrestrial ecosystems to natural and anthropogenic perturbations. This study was conducted to quantify the effects of belowground particulate litter (BPL) addition, increased precipitation and their interactions on soil C and N mineralization in two adjacent sites where belowground photosynthate allocation was manipulated through vegetation clipping in a temperate steppe of northeastern China from 2010 to 2011. The results show that BPL addition significantly increase soil C mineralization rate (CMR) and net N mineralization rate (NMR). Although increased precipitation-induced enhancement of soil CMR essentially ceased after the first year, stimulation of soil NMR and net nitrification rate continued into the second year. Clipping only marginally decreased soil CMR and NMR during the two years. There were significant synergistic interactions between BPL addition (and increased precipitation) and clipping on soil CMR and NMR, likely to reflect shifts in soil microbial community structure and a decrease in arbuscular mycorrhizal fungi biomass due to the reduction of belowground photosynthate allocation. These results highlight the importance of plants in mediating the responses of soil C and N mineralization to potentially increased BPL and precipitation by controlling belowground photosynthate allocation in the temperate steppe.

  8. 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

  9. 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.

  10. 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...

  11. 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 α. 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.

  12. Microorganism-induced weathering of clay minerals in a hydromorphic soil

    NASA Astrophysics Data System (ADS)

    Hong, Hanlie; Fang, Qian; Cheng, Liuling; Wang, Chaowen; Churchman, Gordon Jock

    2016-07-01

    In order to improve the understanding of factors influencing weathering in hydromorphic soils, the clay mineral and chemical compositions, iron (hydr)oxides, organic compounds, and Sr and Nd isotopic compositions, of hydromorphic soils on the banks of the Liangzi Lake, Hubei province, south China, were investigated. The B horizon in the lower profile exhibits a distinct net-like pattern, with abundant short white veins within the red-brown matrix. Their various 87Sr/86Sr and 143Nd/144Nd isotopic compositions showed only small variations of 0.7270-0.7235 and 0.51200-0.51204, respectively, consistent with the composition of Yangtze River sediments, indicating that the soils were all derived from alluvium from the catchment. The white veins contained notably more SiO2, Al2O3, TiO2, and mobile elements relative to the red-brown matrix, while they both showed similar values for the chemical index of alteration of 86.7 and 87.1, respectively, and displayed similar degrees of weathering. The clay minerals in A, AE, and E horizons of the soil profile were illite, kaolinite, and mixed-layer illite-smectite. These same three clay minerals comprised the white net-like veins in the soil B horizon, whereas only illite and kaolinite were observed in the red-brown matrix. Iron (hydr)oxides in A, AE, and E horizons of the soil profile were hematite and goethite, whereas in the red-brown matrix of the B horizon they were hematite, goethite, and ferrihydrite. Different organic compounds were observed for the white vein and the red-brown matrix in the soil B horizon: an 18:2 fatty acid biomarker for fungi in the net-like vein, but not in the red-brown matrix. Compared with the red-brown matrix, the white net-like vein also clearly contained more mono-unsaturated fatty acids, which are sometimes associated with bacteria that have the capacity to reduce Fe(III). Thus, migration of iron and the formation of the net-like veins involved the participation of biota during the hydromorphic

  13. Influence of pH and electrolyte composition on adsorption of poliovirus by soils and minerals.

    PubMed Central

    Taylor, D H; Moore, R S; Sturman, L S

    1981-01-01

    The pH and the nature an concentration of simple electrolytes influenced the interaction of poliovirus type 2 with three soils, a sand, and a clay mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent charge properties, as determined by whole-particle microelectrophoresis. Only when the pH was close to or above the critical region was uptake increased with electrolyte concentration. The transition region for all substrates was above pH 7.5 the isoelectric point of the virus. Thus, it appears that when both the virus and substrate are highly negative charged, repulsive electrostatic effects may exceed inherent attractive interactions, thereby inhibiting adsorption. PMID:6274260

  14. 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, Jérome; Borschneck, Daniel; Bottero, Jean-Yves; Colin, Fabrice; de Junet, Alexis; Doelsch, Emmanuel; Legros, Samuel; Levard, Clément; Masion, Armand; Meunier, Jean-Dominique; Rose, Jérôme

    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

  15. 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

  16. Spectral unmixing for mineral identification in pancam images of soils in Gusev crater, Mars

    NASA Astrophysics Data System (ADS)

    Parente, M.; Bishop, J. L.; Bell, J. F.

    2009-10-01

    The objective of this work is to propose an automated unmixing technique for the analysis of 11-channel Mars Exploration Rover Panoramic Camera (MER/Pancam) spectra. Our approach is to provide a screening tool for identifying unique/distinct reflectance spectra. We demonstrate the utility of this unmixing technique in a study of the mineralogy of the bright salty soils exposed by the rover wheels in images of Gusev crater regions known as Paso Robles (Sols 400,426), Arad (Sol 721), and Tyrone (Sol 790). The unmixing algorithm is based on a novel derivation of the Nonnegative Matrix Factorization technique and includes added features that preclude the adverse effects of low abundance materials that would otherwise skew the unmixing. In order to create a full 11-channel spectrum out of the left and right eye stereo pairs, we also developed a new registration procedure that includes rectification and disparity calculation of the images. We identified two classes of endmember spectra for the bright soils imaged on Sols 426 and 790. One of these endmember classes is also observed for soils imaged on Sols 400 and 721 and has a unique spectral shape that is distinct from most iron oxide, sulfate and silicate spectra and differs from typical martian surface spectra. Instead, its unique spectral character resembles the spectral shape of the ferric sulfate minerals fibroferrite (Fe 3+(SO 4)(OH) · 5H 2O) and ferricopiapite ((Fe,Al,Mg)Fe53+(SO)6(OH)2·20HO) and the phosphate mineral ferristrunzite ((Mn,Fe23+)2(PO)2(OH)2·6HO). The other endmember class is less consistent with specific minerals and is likely a mixture of altered volcanic material and some bright salts. Further analyses of data from Sols 400 and 790 using an anomaly detection algorithm as a tool for detecting low abundance materials additionally suggests the identification of the sulfate mineral paracoquimbite (Fe 2(SO 4) 3 · 9H 2O). This spectral study of Pancam images of the bright S- and P-enriched soils of

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  19. [Effects of temperature, moisture and forest succession on nitrogen mineralization in hillside red soils in mid-subtropical region, China].

    PubMed

    Chen, Fu-Sheng; Yu, Kun; Gan, Lu; Liu, Yi; Hu, Xiao-Fei; Ge, Gang

    2009-07-01

    Effects of temperature, moisture and forest succession, as well as their interaction on nitrogen mineralization in hillside red soils in mid-subtropical region were investigated. The results showed that effects of temperature and succession stage on soil ammonification rate were significant with rate at 12 degrees C < 24 degrees C < 36 degrees C, and rate in shrub and Masson pine forest being lower than that in evergreen broad-leaved forest (P < 0.05), while the impact of moisture was not significant. Moisture and succession stage significantly affected the soil nitrification rate, with that of half-saturation being higher than natural and saturation moisture levels, and that in Masson pine forest being higher than in shrubs (P < 0.05), while temperature had no significant impact. The effects of temperature, moisture and succession stage on soil net N-mineralization rate were all significant, with 12 degrees C < 24 degrees C < 36 degrees C, half-saturation higher than natural and saturation, and shrubs < Masson pine forest < evergreen broad-leaved forest (P < 0.05). Soil ammonification and net N-mineralization rates increased with increasing temperature, while the maximum soil nitrification rate occurred at medium temperature. Moderate soil moisture would benefit the nitrogen mineralization process, and forest succession could improve soil nitrogen supply and restrain excessive nitrification. PMID:19899447

  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. 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.)]...

  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 Belén; Barral, María 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 25°C 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 2°C 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. Prediction of nitrogen responses of corn by soil nitrogen mineralization indicators.

    PubMed

    Simard, R R; Ziadi, N; Nolin, M C; Cambouris, A N

    2001-11-01

    Soil nitrogen mineralization potential (N min) has to be spatially quantified to enable farmers to vary N fertilizer rates, optimize crop yields, and minimize N transfer from soils to the environment. The study objectives were to assess the spatial variability in soil N min potential based on clay and organic matter (OM) contents and the impact of grouping soils using these criteria on corn grain (Zea mays L.) yield, N uptake response curves to N fertilizer, and soil residual N. Four indicators were used: OM content and three equations involving OM and clay content. The study was conducted on a 15-ha field near Montreal, Quebec, Canada. In the spring 2000, soil samples (n = 150) were collected on a 30- x 30-m grid and six rates of N fertilizer (0 to 250 kg N ha(-1)) were applied. Kriged maps of particle size showed areas of clay, clay loam, and fine sandy loam soils. The N min indicators were spatially structured but soil nitrate (NO3-) was not. The N fertilizer rate to reach maximum grain yield (N max), as estimated by a quadratic model, varied among textural classes and Nmin indicators, and ranged from 159 to 250 kg N ha(-1). The proportion of variability (R2) and the standard error of the estimate (SE) varied among textural groups and N min indicators. The R2 ranged from 0.53 to 0.91 and the SE from 0.13 to 1.62. Corn grain N uptake was significantly affected by N fertilizer and the pattern of response differed with soil texture. For the 50 kg N ha(-1) rate, the apparent N min potential (ANM) was significantly larger in the clay loam (122 kg ha(-1)) than in the fine sandy loam (80 kg ha(-1)) or clay (64 kg ha(-1)) soils. The fall soil residual N was not affected by N fertlizer inputs. Textural classes can be used to predict N max. The N min indicators may also assist the variable rate N fertilizer inputs for corn production. PMID:12805786

  8. Ice nucleation by soil dusts: relative importance of mineral dust and biogenic components

    NASA Astrophysics Data System (ADS)

    O'Sullivan, D.; Murray, B. J.; Malkin, T. L.; Whale, T.; Umo, N. S.; Atkinson, J. D.; Price, H. C.; Baustian, K. J.; Browse, J.; Webb, M. E.

    2013-08-01

    Agricultural dust emissions have been estimated to contribute around 20% to the global dust burden. In contrast to dusts from arid source regions, the ice-nucleating abilities of which have been relatively well studied, soil dusts from fertile sources often contain a substantial fraction of organic matter. Using an experimental methodology which is sensitive to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice-nucleating activities of dusts extracted from fertile soils collected at four locations around England. By controlling droplet sizes, which ranged in volume from 10-12 to 10-6 L, we have been able to determine the ice nucleation behaviour of soil dust particles at temperatures ranging from 267 K (-6 °C) down to the homogeneous limit of freezing at about 237 K (-36 °C). At temperatures above 258 K (-15 °C) we find that the ice-nucleating activity of soil dusts is diminished by heat treatment or digestion with hydrogen peroxide, suggesting that the ice nuclei stem from biogenic components in the soil. However, below 258 K, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts, in particular the K-feldspar fraction, becomes increasingly important in the initiation of the ice phase at lower temperatures. We conclude that although only a relatively minor contributor to the global atmospheric dust burden, the enhanced IN activities of dusts generated from agricultural activities may play an important role in cloud glaciation, particularly at temperatures above 258 K.

  9. Ice Nucleation by Soil Dusts: Relative Importance of Mineral Dust and Biogenic Components

    NASA Astrophysics Data System (ADS)

    Murray, B. J.; O'Sullivan, D.; Malkin, T. L.; Whale, T.; Umo, N.; Atkinson, J.; Price, H.; Baustian, K. J.; Browse, J.; Webb, M. E.

    2013-12-01

    Agricultural dust emissions have been estimated to contribute around 20 % to the global dust burden. In contrast to dusts from arid source regions, the ice-nucleating abilities of which have been relatively well studied, soil dusts from fertile sources often contain a substantial fraction of organic matter. Using an experimental methodology which is sensitive to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice-nucleating activities of dusts extracted from fertile soils collected at four locations around England. By controlling droplet sizes, which ranged in volume from pico- to micro- Liter , we have been able to determine the ice nucleation behaviour of soil dust particles at temperatures ranging from 267 K (-6 °C) down to the homogeneous limit of freezing at about 237 K (-36 °C). At temperatures above 258 K (-15 °C) we find that the ice-nucleating activity of soil dusts is diminished by heat treatment or digestion with hydrogen peroxide, suggesting that the ice nuclei stem from biogenic components in the soil. However, below 258 K, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts, in particular the K-feldspar fraction, becomes increasingly important in the initiation of the ice phase at lower temperatures. We conclude that although only a relatively minor contributor to the global atmospheric dust burden, the enhanced IN activities of dusts generated from agricultural activities may play an important role in cloud glaciation, particularly at temperatures above 258 K.

  10. Ice nucleation by fertile soil dusts: relative importance of mineral and biogenic components

    NASA Astrophysics Data System (ADS)

    O'Sullivan, D.; Murray, B. J.; Malkin, T. L.; Whale, T. F.; Umo, N. S.; Atkinson, J. D.; Price, H. C.; Baustian, K. J.; Browse, J.; Webb, M. E.

    2014-02-01

    Agricultural dust emissions have been estimated to contribute around 20% to the global dust burden. In contrast to dusts from arid source regions, the ice-nucleating abilities of which have been relatively well studied, soil dusts from fertile sources often contain a substantial fraction of organic matter. Using an experimental methodology which is sensitive to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice-nucleating activities of dusts (d < 11 µm) extracted from fertile soils collected at four locations around England. By controlling droplet sizes, which ranged in volume from 10-12 to 10-6 L (concentration = 0.02 to 0.1 st% dust), we have been able to determine the ice nucleation behaviour of soil dust particles at temperatures ranging from 267 K (-6° C) down to the homogeneous limit of freezing at about 237 K (-36° C). At temperatures above 258 K (-15° C) we find that the ice-nucleating activity of soil dusts is diminished by heat treatment or digestion with hydrogen peroxide, suggesting that a major fraction of the ice nuclei stems from biogenic components in the soil. However, below 258 K, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts, in particular the K-feldspar fraction, becomes increasingly important in the initiation of the ice phase at lower temperatures. We conclude that dusts from agricultural activities could contribute significantly to atmospheric IN concentrations, if such dusts exhibit similar activities to those observed in the current laboratory study.

  11. [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

  12. 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

  13. 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

  14. 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

  15. 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 process’s 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.

  16. 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.

  17. 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

  18. Phosphate-Based Mineralization of Arsenic in Contaminated Soil: A Potential Remediation Method for Soil and Groundwater

    NASA Astrophysics Data System (ADS)

    Neupane, G.; Donahoe, R. J.

    2009-12-01

    Soil arsenic contamination resulting from the use of arsenical compounds is a widespread environmental problem. A phosphate-based remediation method which has the potential to immobilize arsenic in both oxidizing and reducing subsurface systems is under laboratory investigation. Although phosphate treatments have been reported to be effective in removal of arsenic from contaminated water, its use in contaminated soils has not been tested. This study aims to (1) determine the competitive adsorption/desorption of arsenate and phosphate at surfaces of ferric hydroxide coated sand in the absence or presence of calcium ions, and (2) develop a method of arsenic fixation which involves phosphoric acid flushing of arsenic from contaminated soil and precipitation of arsenic as apatite-like phases. Ferric hydroxide is a significant arsenic sequestering constituent in soil. Phosphate competes with arsenate for adsorption sites on the ferric hydroxide surface. Batch adsorption experiments conducted using ferric hydroxide coated sand have indicated similar pH-controlled adsorption mechanisms for both arsenate and phosphate. The data obtained from the adsorption experiments is being used to guide the development of a phosphate-based method for soil and groundwater arsenic remediation. Batch experiments were performed using 3g of contaminated soil in contact with 45 ml of treatment fluid (a dilute phosphoric acid and calcium hydroxide solution). Solution samples were collected at 24, 72, 144, 312, and 384 hours, with continuous agitation at 200 rpm. Solution concentrations of phosphorus and calcium generally decreased with time and were primarily controlled by pH. It has been experimentally demonstrated that solution arsenic concentrations can be lowered by maintaining high pH with adequate calcium supply. A batch experiment conducted at pH > 11, using 1 kg of soil in contact with 1 liter of 0.25% H3PO4, precipitated a white material giving an XRD signature indicative of brushite

  19. Nitrogen mineralization and microbial activity in oil sands reclaimed boreal forest soils.

    PubMed

    McMillan, R; Quideau, S A; MacKenzie, M D; Biryukova, O

    2007-01-01

    Organic materials including a peat-mineral mix (PM), a forest floor-mineral mix (L/S), and a combination of the two (L/PM) were used to cap mineral soil materials at surface mine reclamation sites in the Athabasca oil sands region of northeastern Alberta, Canada. The objective of this study was to test whether LFH provided an advantage over peat by stimulating microbial activity and providing more available nitrogen for plant growth. Net nitrification, ammonification, and N mineralization rates were estimated from field incubations using buried bags. In situ gross nitrification and ammonification rates were determined using the 15N isotope pool dilution technique, and microbial biomass C (MBC) and N (MBN) were measured by the chloroform fumigation-extraction method. All reclaimed sites had lower MBC and MBN, and lower net ammonification and net mineralization rates than a natural forest site (NLFH) used as a control, but the reclamation treatment using LFH material by itself had higher gross and net nitrification rates. A positive correlation between in situ moisture content, dissolved organic N, MBC, and MBN was observed, which led us to conduct a moisture manipulation experiment in the laboratory. With the exception of the MBN for the L/S treatment, none of the reclamation treatments ever reached the levels of the natural site during this experiment. However, materials from reclamation treatments that incorporated LFH showed higher respiration rates, MBC, and MBN than the PM treatment, indicating that the addition of LFH as an organic amendment may stimulate microbial activity as compared to the use of peat alone. PMID:17766826

  20. 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

  1. Characterization of lead on mineral surfaces in soils contaminated by mining and smelting

    NASA Astrophysics Data System (ADS)

    Tingle, Tracy N.; Borch, Robert S.; Hochella, Michael F.; Becker, Christopher H.; Walker, William J.

    1993-12-01

    Mine tailings and soils impacted by mining, milling and smelting of Cu-Pb-Zn-Ag-Au ores in a small mining town in central Colorado were analyzed by X-ray photoelectron spectroscopy (XPS), and surface analysis by laser ionization (SALI) utilizing stimulated desorption (pulsed Ar +) coupled with nonresonant photoionization (using 266 nm light) and time-of-flight mass spectrometry. These surface-sensitive techniques revealed that Pb is present on mineral grain surfaces in some soild and mine tailings. The presence of surface-bound Pb correlates with soil pH; carbonate-sulfide tailing with pH≈7 have Pb-bearing iron hydroxide (and to a lesser extent iron sulfate) coatings that are several μm thick, whereas sulfide tailings with pH≈2 have little or no detectable surface-bound Pb. Grains from residential soils (pH≈7) have thin (a few nm thick) Pb-bearing surface layers. Soils impacted by smelter aerosols and fly ash (pH = 4.5) also have thin (a few nm thick) Pb-bearing surfaces layers. Measured Pb4f 7/2 binding energies (corrected for charge shifting by referencing the Si2s peak to 153.0 eV) ranged from 137.4 to 138.2 eV and suggest that the surface-bound Pb is present as Pb-O or Pb-OH species.

  2. 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

  3. 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

  4. 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.

  5. 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.

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

    USGS Publications Warehouse

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

    2015-01-01

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

  7. 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

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

    SciTech Connect

    Morrison, D.E.; Alexander, M.

    1997-08-01

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

  9. 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.

  10. 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).

  11. Response of forest seedling/soil microcosms to elevated CO{sub 2} and soil temperature, water, and light: Carbon and nitrogen mineralization and allocation

    SciTech Connect

    Gillham, M.L.; Perry, D.A.

    1995-09-01

    Soils from 500-year-old old-growth Douglas-fir forests in the western Oregon Cascade Mtns. (945m and 1325m sites) were {open_quotes}incubated{close_quotes} for 32 weeks in controlled-environment chambers. Objectives were (1) to determine the interacting effects of soil temperature and atmospheric CO{sub 2} on N availability in soils, growth of Douglas-fir seedlings, and resulting C & N fluxes among trees, soils, and the atmosphere, and (2) to model these interactions with a version of Fregro linked with the GEM soil-decomposition model. The experiment was a split-plot with a factorial treatment combination containing two leves each of atmospheric CO{sub 2} (350/700 ppm), soil temperature (13.8/17.7{degrees}C), soil C & N (1325m soils had 2.3x more C and 1.25x more N than 945m soils), and vegetation (+/-seedlings). Each wholeplot (chamber) treatment (CO{sub 2} x temperature) was replicated three times. Photosynthetic photon flux density, soil temperature, and volume of added water were determined for each pot and analyzed as covariates. Responses measured include differences in soil C & N mineralization and total soil C & N in the presence/absence of seedlings, the extent to which subsequent seedling growth offsets potential {open_quote}system{close_quote} losses of C & N, and allocation of C & N to foliage and fine roots. Previously reported early results (ESA, 1994) suggest that (1) as hypothesized, soil temperatures is the main driver of changes in both N mineralization and biomass production in seedling microcosms, (2) allocation is primarily influenced by atmospheric CO{sub 2} concentration, and (3) a soil type x soil temperature x CO{sub 2} interaction influences seedling growth.

  12. 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

  13. 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 (γ-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

  14. 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

  15. Maxwell Wagner Relaxation in Common Minerals and a Desert Soil at Low Water Contents

    NASA Astrophysics Data System (ADS)

    Arcone, S. A.

    2010-12-01

    Maxwell-Wagner type dielectric permittivity relaxation in soils is caused by macro-dipolar inclusions, usually of grain size dimensions, and generally within a more dielectric matrix. We discuss laboratory measurements of the complex permittivity of quartz, feldspars, calcite, two forms of gypsum and a simple desert soil at 4-7 percent volumetric water content, and in which we interpret Maxwell-Wagner processes to have dominated. We used Fourier Transform time domain reflectometry, measured from 1 MHz to 6 GHz, and used small samples with grain sizes less than 53 microns. Using XRD and SEM, we found the soil contained quartz, gypsum and feldspars at 80, 10 and 10 percent by weight, respectively, with the gypsum appearing as crystallites and crustations on the quartz particles. All samples show low conductivity, and low-frequency dispersion. The montmorillonite, gypsum crystallites, and desert soil exhibit unusually strong and broad low-frequency dispersion, and strong attenuation rates above 100 MHz. The one-way attenuation rates of the soil exceed those of its constituents, are similar to that of montmorillonite, and exceed 100 dB/m by 1 GHz. Through modeling using the CRIM approach, we attribute all permittivity behavior to a combination of Maxwell-Wagner and free water relaxations, with the former dominant and able to contribute significantly to attenuation rates into the GHz range because of Cole-Cole broadened relaxation frequencies centered from 1-20 MHz, while the latter is centered at 20 GHz. The lack of sufficient surface area to support adsorbed water relaxation, the lack of salts, clay and magnetic minerals, and the inadequacy of measured conductivity values to explain the high loss further justify our Maxwell-Wagner interpretation. The polarized inclusions within the soil are likely to have been conductive wet gypsum particles, whereby films of water that coated the particles polarized. The source of the charge was likely to have been ions dissolved

  16. 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

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

    PubMed

    Coucheney, Elsa; Strömgren, Monika; Lerch, Thomas Z; Herrmann, Anke M

    2013-12-01

    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

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

    PubMed Central

    Coucheney, Elsa; Strömgren, Monika; Lerch, Thomas Z; Herrmann, Anke M

    2013-01-01

    Boreal ecosystems store one-third of global soil organic carbon (SOC) and are particularly sensitive to climate warming and higher nutrient inputs. Thus, a better description of how forest managements such as nutrient fertilization impact soil carbon (C) and its temperature sensitivity is needed to better predict feedbacks between C cycling and climate. The temperature sensitivity of in situ soil C respiration was investigated in a boreal forest, which has received long-term nutrient fertilization (22 years), and compared with the temperature sensitivity of C mineralization measured in the laboratory. We found that the fertilization treatment increased both the response of soil in situ CO2 effluxes to a warming treatment and the temperature sensitivity of C mineralization measured in the laboratory (Q10). These results suggested that soil C may be more sensitive to an increase in temperature in long-term fertilized in comparison with nutrient poor boreal ecosystems. Furthermore, the fertilization treatment modified the SOC content and the microbial community composition, but we found no direct relationship between either SOC or microbial changes and the temperature sensitivity of C mineralization. However, the relation between the soil C:N ratio and the fungal/bacterial ratio was changed in the combined warmed and fertilized treatment compared with the other treatments, which suggest that strong interaction mechanisms may occur between nutrient input and warming in boreal soils. Further research is needed to unravel into more details in how far soil organic matter and microbial community composition changes are responsible for the change in the temperature sensitivity of soil C under increasing mineral N inputs. Such research would help to take into account the effect of fertilization managements on soil C storage in C cycling numerical models. PMID:24455147

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

    PubMed

    Blume, Elena; Reichert, José 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

  20. 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

  1. 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.

  2. 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

    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.

  3. 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

  4. 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

  5. Soil mineral composition matters: response of microbial communities to phenanthrene and plant litter addition in long-term matured artificial soils.

    PubMed

    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

  6. 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.

  7. Substrate quality alters 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.

    2014-03-01

    The rate and extent of decomposition of soil organic carbon (SOC) is dependent on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial processing 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, despite an initial delay in respiration. 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 was sufficient to model decomposition of simple substrates (glucose and starch) with three pools, but was insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality imparts considerable control on 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 added substrates.

  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, α-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. Artificial soil studies reveal domain-specific preferences of microorganisms for the colonisation of different soil minerals and particle size fractions.

    PubMed

    Hemkemeyer, Michael; Pronk, Geertje J; Heister, Katja; Kögel-Knabner, Ingrid; Martens, Rainer; Tebbe, Christoph C

    2014-12-01

    Artificial soils were used in this study to analyse the importance of different mineral compositions for the diversity of soil microorganisms. Variants containing montmorillonite (MT), illite (IL) and illite + ferrihydrite (IL+FH) were compared to each other. Bulk material and their particle size fractions, as obtained by ultracentrifugation and wet-sieving, were characterised for abundance and diversity of Bacteria, Archaea and Fungi. Samples were analysed 6 and 18 months after inoculation with sterilised manure and a soil-extracted microbial community. Generally, IL, and even more pronouncedly IL+FH, supported the growth of more Bacteria, Archaea and Fungi, than MT. This trend was most pronounced in the finest fraction (< 20 μm). The structural diversity of Fungi responded more strongly to the different mineral compositions than the Bacteria, for which particle size fractions were more important. Archaea established a specific community in the finest fraction and showed no response to the different mineral compositions. Overall, this study demonstrates that the mineral composition and the particle size fractions have specific and different selective effects on the three domains and, thus, suggests that these factors strongly contribute to niche separation and the high diversity of microbial communities in natural soils with complex mineral compositions. PMID:25303098

  10. 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 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

  11. 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.

  12. Stimulating soil microorganisms for mineralizing the herbicide isoproturon by means of microbial electroremediating cells.

    PubMed

    Rodrigo Quejigo, Jose; Dörfler, Ulrike; Schroll, Reiner; Esteve-Núñez, Abraham

    2016-05-01

    The absence of suitable terminal electron acceptors (TEA) in soil might limit the oxidative metabolism of environmental microbial populations. Microbial electroremediating cells (MERCs) consist in a variety of bioelectrochemical devices that aim to overcome electron acceptor limitation and maximize metabolic oxidation with the purpose of enhancing the biodegradation of a pollutant in the environment. The objective of this work was to use MERCs principles for stimulating soil bacteria to achieve the complete biodegradation of the herbicide (14) C-isoproturon (IPU) to (14) CO2 in soils. Our study concludes that using electrodes at a positive potential [+600 mV (versus Ag/AgCl)] enhanced the mineralization by 20-fold respect the electrode-free control. We also report an overall profile of the (14) C-IPU metabolites and a (14) C mass balance in response to the different treatments. The remarkable impact of electrodes on the microbial activity of natural communities suggests a promising future for this emerging environmental technology that we propose to name bioelectroventing. PMID:26880137

  13. Enhanced Mineralization of [U-14C]2,4-Dichlorophenoxyacetic Acid in Soil from the Rhizosphere of Trifolium pratense

    PubMed Central

    Shaw, Liz J.; Burns, Richard G.

    2004-01-01

    Enhanced biodegradation in the rhizosphere has been reported for many organic xenobiotic compounds, although the mechanisms are not fully understood. The purpose of this study was to discover whether rhizosphere-enhanced biodegradation is due to selective enrichment of degraders through growth on compounds produced by rhizodeposition. We monitored the mineralization of [U-14C]2,4-dichlorophenoxyacetic acid (2,4-D) in rhizosphere soil with no history of herbicide application collected over a period of 0 to 116 days after sowing of Lolium perenne and Trifolium pratense. The relationships between the mineralization kinetics, the number of 2,4-D degraders, and the diversity of genes encoding 2,4-D/α-ketoglutarate dioxygenase (tfdA) were investigated. The rhizosphere effect on [14C]2,4-D mineralization (50 μg g−1) was shown to be plant species and plant age specific. In comparison with nonplanted soil, there were significant (P < 0.05) reductions in the lag phase and enhancements of the maximum mineralization rate for 25- and 60-day T. pratense soil but not for 116-day T. pratense rhizosphere soil or for L. perenne rhizosphere soil of any age. Numbers of 2,4-D degraders in planted and nonplanted soil were low (most probable number, <100 g−1) and were not related to plant species or age. Single-strand conformational polymorphism analysis showed that plant species had no impact on the diversity of α-Proteobacteria tfdA-like genes, although an impact of 2,4-D application was recorded. Our results indicate that enhanced mineralization in T. pratense rhizosphere soil is not due to enrichment of 2,4-D-degrading microorganisms by rhizodeposits. We suggest an alternative mechanism in which one or more components of the rhizodeposits induce the 2,4-D pathway. PMID:15294813

  14. 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

  15. [Dynamics of the mineralization and transformation of rice photosynthesized carbon in paddy soils--a batch incubation experiment].

    PubMed

    Tan, Li-Min; Peng, Pei-Qin; Li, Ke-Lin; Li, Bao-Zhen; Nie, San-An; Ge, Ti-Da; Tong, Cheng-Li; Wu, Jin-Shui

    2014-01-01

    Photosynthesized carbon is an important part in C cycling of "atmosphere-plant-soil" and is the source of soil organic carbon (SOC), but its mineralization and transformation dynamics in paddy soils remains still unclear. Therefore, a batch incubation experiment was conducted to investigate the mineralization and transformation of rice photosynthesized carbon in paddy soils after rice harvest. The results showed that the mineralization rate of native SOC ranged from 4.44 to 17.8 microg x (g x d)(-1), while that of photosynthesized carbon (new carbon) was 0.15- 1.51 micro x (gx d)(-1) during the course of 100-day-incubation span. Rice photosynthesized carbon input significantly influenced the soil active carbon (DOC, MBC) transformation. During the incubation period (100 d), the amount of 14C-DOC transformation ranged from 1.89 to 5.32 mg x 8 kg(-1), and that of native DOC varied from 61.13 to 90.65 mg x kg(-2), with the transformation rates ranged from 0.18 to 0.34 mg x (kg x d)(-1) and from 4.10 to 5.48 mg. (kg x d)(-1), respectively. However, the 14C-MBC and native original MBC were 10.92-44.11 mg x kg(-1) and 463.31-1153.46 mg x kg(-1), respectively, and their transformation rates were 0.80-2.87, 41.60-74.46 mg x (kg-d)(-1), respectively. It suggested that the turnover of MBC was greater than that of DOC. Furthermore, "new carbon" was easier to be mineralized and decomposed than native SOC. The mineralized portion in "new carbon" was 13.5%-20.2%, whereas that in native SOC was only 2.2%-3.7%. Therefore, we concluded that the incorporation of rice photosynthesized carbon was vital to maintain the soil carbon sink for paddy soils. PMID:24720210

  16. 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

  17. 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 Å and surrounded by Al atoms at 3.03-3.06 Å 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

  18. 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

  19. 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; Plötze, Michael; Senn, Anna-Caterina; Mangold, Stefan; Steininger, Ralph; Göttlicher, Jörg

    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 (μ-XRF) and X-ray absorption spectroscopy (μ-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

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

    NASA Astrophysics Data System (ADS)

    Dümig, Alexander; Häusler, Werner; Steffens, Markus; Kögel-Knabner, Ingrid

    2012-05-01

    Interactions between organic and mineral constituents prolong the residence time of organic matter in soils. However, the structural organization and mechanisms of organic coverage on mineral surfaces as well as their development with time are still unclear. We used clay fractions from a soil chronosequence (15, 75 and 120 years) in the foreland of the retreating Damma glacier (Switzerland) and from mature soils outside the proglacial area (>700 and <3000 years) to elucidate the evolution of organo-mineral associations during initial soil formation. The chemical composition of the clay-bound organic matter (OM) was assessed by solid-state 13C NMR spectroscopy while the quantities of amino acids and neutral sugar monomers were determined after acid hydrolysis. The mineral phase was characterized by X-ray diffraction, oxalate extraction, specific surface area by N2 adsorption (BET approach), and cation exchange capacity at pH 7 (CECpH7). The last two methods were applied before and after H2O2 treatment. We found pronounced shifts in quantity and quality of OM during aging of the clay fractions, especially within the first one hundred years of soil formation. The strongly increasing organic carbon (OC) loading of clay-sized particles resulted in decreasing specific surface areas (SSA) of the mineral phases and increasing CECpH7. Thus, OC accumulation was faster than the supply of mineral surfaces and cation exchange capacity was mainly determined by the OC content. Clay-bound OC of the 15-year-old soils showed high proportions of carboxyl C and aromatic C. This may point to remnants of ancient OC which were inherited from the recently exposed glacial till. With increasing age (75 and 120 years), the relative proportions of carboxyl and aromatic C decreased. This was associated with increasing O-alkyl C proportions, whereas accumulation of alkyl C was mainly detected in clay fractions from the mature soils. These findings from solid-state 13C NMR spectroscopy are in

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. Clay minerals and metal oxides strongly influence the structure of alkane-degrading microbial communities during soil maturation.

    PubMed

    Steinbach, Annelie; Schulz, Stefanie; Giebler, Julia; Schulz, Stephan; Pronk, Geertje J; Kögel-Knabner, Ingrid; Harms, Hauke; Wick, Lukas Y; Schloter, Michael

    2015-07-01

    Clay minerals, charcoal and metal oxides are essential parts of the soil matrix and strongly influence the formation of biogeochemical interfaces in soil. We investigated the role of these parental materials for the development of functional microbial guilds using the example of alkane-degrading bacteria harbouring the alkane monooxygenase gene (alkB) in artificial mixtures composed of different minerals and charcoal, sterile manure and a microbial inoculum extracted from an agricultural soil. We followed changes in abundance and community structure of alkane-degrading microbial communities after 3 and 12 months of soil maturation and in response to a subsequent 2-week plant litter addition. During maturation we observed an overall increasing divergence in community composition. The impact of metal oxides on alkane-degrading community structure increased during soil maturation, whereas the charcoal impact decreased from 3 to 12 months. Among the clay minerals illite influenced the community structure of alkB-harbouring bacteria significantly, but not montmorillonite. The litter application induced strong community shifts in soils, maturated for 12 months, towards functional guilds typical for younger maturation stages pointing to a resilience of the alkane-degradation function potentially fostered by an extant 'seed bank'. PMID:25535940

  3. 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

  4. Effect of organic and mineral soil fractions on sorption behaviour of chlorophenol and triazine micropollutants.

    PubMed

    Stipicević, Sanja; Fingler, Sanja; Drevenkar, Vlasta

    2009-03-01

    This article compares the sorption behaviour of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, chlorotriazine atrazine, methylthiotriazine ametryn, methoxytriazine atratone, hydroxyatrazine, and didelakylated atrazine in a topsoil and an aquifer sediment before and after removal of sorbent organic matter and in humic acid. Freundlich isotherm coefficients Kf and 1/n and free energy change (deltaG degrees ) were calculated for all compounds in all sorbents. According to sorbent pH values, chlorophenolate anions and uncharged triazine species dominated in all sorption experiments with topsoil and aquifer sediment. In experiments with humic acid, chlorophenols, atrazine, and didealkylated atrazine existed almost completely as neutral species, whereas protonated species dominated for hydroxyatrazine, atratone, and ametryn. In addition to a hydrophobic partition, sorption of all compounds in native soil and sediment sorbents includes specific, more polar interactions, which greatly depend on sorbate acidity/basicity, specific properties of the sorbent organic matter and of mineral surface, as well as on the system pH. A significantly greater sorption intensity of all compounds in "organic-free" than in the native aquifer sediment confirmed the importance and possible dominance of mineral surface in the sorption process. Sorption intensity of chlorophenol and triazine compounds in humic acid was closely related to compound hydrophobicity. Greater sorption of almost completely protonated hydroxyatrazine than of the more hydropohobic but uncharged atrazine indicated different humic acid reaction sites for two compounds and consequently different sorption mechanisms. PMID:19329375

  5. Chromate adsorption on selected soil minerals: Surface complexation modeling coupled with spectroscopic investigation.

    PubMed

    Veselská, Veronika; Fajgar, Radek; Číhalová, Sylva; Bolanz, Ralph M; Göttlicher, Jörg; Steininger, Ralph; Siddique, Jamal A; Komárek, Michael

    2016-11-15

    This study investigates the mechanisms of Cr(VI) adsorption on natural clay (illite and kaolinite) and synthetic (birnessite and ferrihydrite) minerals, including its speciation changes, and combining quantitative thermodynamically based mechanistic surface complexation models (SCMs) with spectroscopic measurements. Series of adsorption experiments have been performed at different pH values (3-10), ionic strengths (0.001-0.1M KNO3), sorbate concentrations (10(-4), 10(-5), and 10(-6)M Cr(VI)), and sorbate/sorbent ratios (50-500). Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy were used to determine the surface complexes, including surface reactions. Adsorption of Cr(VI) is strongly ionic strength dependent. For ferrihydrite at pH <7, a simple diffuse-layer model provides a reasonable prediction of adsorption. For birnessite, bidentate inner-sphere complexes of chromate and dichromate resulted in a better diffuse-layer model fit. For kaolinite, outer-sphere complexation prevails mainly at lower Cr(VI) loadings. Dissolution of solid phases needs to be considered for better SCMs fits. The coupled SCM and spectroscopic approach is thus useful for investigating individual minerals responsible for Cr(VI) retention in soils, and improving the handling and remediation processes. PMID:27450335

  6. 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

  7. 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 (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 21(st) Century. PMID:23226324

  8. Carbon dioxide emissions from semi-arid soils amended with biochar alone or combined with mineral and organic fertilizers.

    PubMed

    Fernández, José M; Nieto, M Aurora; López-de-Sá, Esther G; Gascó, Gabriel; Méndez, Ana; Plaza, César

    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

  9. Vadose zone modelling as a tool to develop a generic framework for the re-use of soil or mineral waste onto soil

    NASA Astrophysics Data System (ADS)

    Joris, I.; Quaghebeur, M.; Broos, K.; Seuntjens, P.; van Gestel, G.; Debaene, L.; Dedecker, D.

    2009-04-01

    Slightly contaminated soil that is excavated during building or land management projects can be re-used at other locations either as soil or as building material. Likewise, mineral waste products re-usable as building material can be applied onto soil, e.g. in roadworks or building foundation layers. In order to ensure that this is done in a safe manner without compromising soil or groundwater quality, quality standards need to be set. In this study, a framework is developed of generic quality standards for the re-use of excavated soil as well as mineral waste products re-usable as building materials. Topics that are addressed before the start of model calculations are: - what are safe concentrations in soil and groundwater that ensure protection of human and ecosystem health; - what are typical application scenarios; - what is the range of soil parameters to be used in the model calculations; - what type of leaching tests are used to describe leaching of contaminants from the excavated soil or mineral waste and how can these test results be translated to a source term for model calculations. These boundary conditions are defined within the limits set by EU regulations such as the Water Framework Directive and the Landfill Directive and presented and discussed with stakeholders. Next, risk-based quality standards are calculated that are protective for both soil and groundwater. Since well-defined applications scenarios were set for the derivation of quality standards, model calculations are carried out using a 1D analytical water flow and transport model. Calculations are done for different metals and for a range of soil parameters that are either critical for soil (high sorption) or for groundwater (low sorption). Quality standards for re-use are determined iteratively as the concentration at which the maximum tolerable concentration in soil or in groundwater is reached. Different sets of quality standards are presented and the sensitivity of the results to the

  10. 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...

  11. The effect of increasing salinity and forest mortality on soil nitrogen and phosphorus mineralization in tidal freshwater forested wetlands