The Experts below are selected from a list of 57423 Experts worldwide ranked by ideXlab platform
Gan-lin Zhang - One of the best experts on this subject based on the ideXlab platform.
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si cycling and isotope fractionation implications on weathering and Soil formation processes in a typical subtropical area
Geoderma, 2019Co-Authors: Jinling Yang, Gan-lin ZhangAbstract:Abstract The translocation of silicon (Si) is closely related to Soil Evolution. However, how to trace the transformation and migration paths of Si and further understand its effects on Soil formation and Evolution remains as a challenge in geochemistry and Soil science. Here we studied the Si isotope (δ30Si) values and physical, chemical and mineralogical properties of rock, Soil, plant and water in representative small watersheds in the south of Anhui province, subtropical China. The aims are to illustrate weathering and Soil formation processes by tracing the fractionation of Si isotope among those ecosystem components as well as Soil components and plant organs. Results show that the δ30Si values of bulk Soil and clay are significantly related to many Soil development indicators, such as total, free and amorphous Al oxides, as well as active Fe oxides, clay, silt and sand contents, Al/Si molar ratio and chemical index of alteration (CIA). These indicators evidence the relationships between Si isotope changes and mineral weathering and Soil development degree. Biological resilication (accumulation of Si) by plant does not lower Soil δ30Si because further fractionation occurs among plant organs, and Soil phytoliths have significantly higher δ30Si than Soil clay and silt particles. However, Soil desilication (loss of Si) lowers Soil δ30Si because much 30Si is transported to streams in runoff. The consistently positive δ30Si values of water and their relationships with Si concentrations and discharge suggest that dissolved Si (DSi) in stream water mainly comes from weathering of primary minerals; the contribution of dissolution of secondary minerals, quartz and phytolith is minor. Differential δ30Si values in clay, silt, sand, rock and water are the result of Soil formation processes which directly evidence a dominate neoformation pathway of secondary clay minerals in this area. This study can help to further understand mechanisms and processes of Si translocation during Soil Evolution and, extend the application of Si translocation in Soil genesis studies.
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phases and rates of iron and magnetism changes during paddy Soil development on calcareous marine sediment and acid quaternary red clay
Scientific Reports, 2018Co-Authors: Laiming Huang, Liu-mei Chen, Mingan Shao, Gan-lin ZhangAbstract:Dynamic changes in Fe oxides and magnetic properties during natural pedogenesis are well documented, but variations and controls of Fe and magnetism changes during anthropedogenesis of paddy Soils strongly affected by human activities remain poorly understood. We investigated temporal changes in different Fe pools and magnetic parameters in Soil profiles from two contrasting paddy Soil chronosequences developed on calcareous marine sediment and acid Quaternary red clay in Southern China to understand the directions, phases and rates of Fe and magnetism Evolution in Anthrosols. Results showed that paddy Soil Evolution under the influence of artificial submergence and drainage caused changes in Soil moisture regimes and redox conditions with both time and depth that controlled Fe transport and redistribution, leading to increasing profile differentiation of Fe oxides, rapid decrease of magnetic parameters, and formation of diagnostic horizons and features, irrespective of the different parent materials. However, the initial parent material characteristics (pH, Fe content and composition, weathering degree and landscape positions) exerted a strong influence on the rates and trajectories of Fe oxides Evolution as well as the phases and rates of magnetism changes. This influence diminished with time as prolonged rice cultivation drove paddy Soil evolving to common pedogenic features.
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Variations and controls of iron oxides and isotope compositions during paddy Soil Evolution over a millennial time scale
Chemical Geology, 2018Co-Authors: Laiming Huang, Aaron Thompson, Gan-lin Zhang, Xiaoxu Jia, Fang Huang, Min-an Shao, Liu-mei ChenAbstract:Abstract A paddy Soil chronosequence consisting of five profiles derived from calcareous marine sediments with cultivation history from 0 to 1000 years was studied to understand the underlying mechanisms and processes controlling the millennial scale Fe Evolution. We evaluated the chronosequencial changes in depth distribution of Fe oxide contents and Fe isotopic compositions. Results showed that paddy Soil Evolution under the influence of periodic flooding and groundwater fluctuation resulted with time in variations of Soil moisture regime and redox condition that control Fe mobilization, translocation and redistribution, leading to enhanced profile differentiation of Fe oxides and measurable Fe isotope fractionation. Total Fe and oxide bound Fe as well as their differentiation between surface and subsurface horizons increased as paddy Soils age, leading to the formation of diagnostic horizons and features characterizing Fe distribution and redistribution. Selective extractions showed that the weakly-bound, oxide-bound and silicate bound Fe corresponded to 1–16%, 8–46%, and 52–91% of the total Fe, respectively, and these proportions varied with both time and depth due to the redox-related Fe transformation and translocation. δ 56 Fe values in the studied paddy Soil chronosequence ranged from − 0.01‰ to 0.18‰ and exhibited a strong negative correlation with the logarithm of total Fe concentrations, suggesting mass-dependent Fe isotope fractionation occurred as a result of the preferential removal of lighter Fe isotopes during long-term paddy Soil Evolution under the predominant reducing conditions. However, the Fe isotopic ratio of a specific paddy Soil horizon was a result of a complex interaction of different processes, which were summarized and interpreted in our proposed conceptual model. Comparison of Fe isotopic compositions in the worldwide Soils demonstrated that Fe isotopes can evidence Fe transfer and pinpoint the factors and processes that control Fe mobilization and redistribution particularly in Soils with changing moisture regimes and redox conditions. Our findings provide new insights into the behavior and geochemical cycle of Fe at the Earth's surface strongly affected by human activities and contributes to an improved understanding of how anthropedogenesis affects Fe Evolution in the Earth's Critical Zone.
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pedogenesis significantly decreases the stability of water dispersible Soil colloids in a humid tropical region
Geoderma, 2016Co-Authors: Laiming Huang, David G. Rossiter, Mingan Shao, Xinhui Zhang, Gan-lin ZhangAbstract:Abstract The stability of Soil colloids influences Soil physicochemical properties, Soil development, and transfer of nutrients and contaminants to surface and ground waters. A better understanding of Soil colloids stability dynamics during Soil Evolution is important for the evaluation of Soil's capacity to retain nutrients and/or accommodate toxic contaminants. This study was aimed to determine changes in the stability of water-dispersible Soil colloids that accompany mineral transformation and surface charge Evolution during pedogenesis using a well characterized chronosequence derived from basalt in the humid tropical region of Hainan Island, South China. The results demonstrated that the pH-dependent colloid stability decreased significantly with tropical Soil development, which we attribute to the substantial changes in clay mineral compositions and colloid surface charge properties. Clay minerals in the studied chronosequence were characterized by an increase of kaolinite, gibbsite and Fe oxides and a decrease of quartz and halloysite towards more advanced stages of weathering, which resulted in the decline of permanent negative charges in the older Soils. The point of zero charge (pHPZC) increased while ∆ pH decreased across the tropical Soil chronosequence, being in good agreement with the observed lower colloid stability in aged Soils dominated by kaolinitic minerals. Our study of colloid stability at long-term pedogenic time scale suggests young tropical Soils (
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magnetic depletion and enhancement in the Evolution of paddy and non paddy Soil chronosequences
European Journal of Soil Science, 2015Co-Authors: Longfei Chen, David G. Rossiter, Gan-lin Zhang, Z H CaoAbstract:Summary The objective of this study was to understand the rates and controlling factors of magnetic depletion and enhancement during anthropogenic Soil Evolution. To this end, the study compared the dynamic changes in magnetic properties as well as iron oxide species of paddy and non-paddy Soil chronosequences with the same parent materials. A two-way analysis of variance (anova) showed that paddy management resulted in significant (P < 0.01) decreases in magnetic susceptibility (χ) and other magnetic properties. Paddy management-induced χ losses increased gradually from 24 to 55% as the cultivation history increased from 50 to 700 years. The rates of χ decrease were most rapid within the first 50 years of paddy cultivation, after which the rate slowed. The rapid decline in χ is probably caused by accelerated depletion of fine-grained maghemite and ultrafine magnetite by iron-reducing bacteria during Soil waterlogging and consequent reducing conditions. By contrast, a significant decrease in hard isothermal remanent magnetization (HIRM) occurred only after 700 years of paddy cultivation, which matches the time taken to leach CaCO3 from the profile. In contrast, although magnetic enhancement was observed in the non-paddy surface horizon, there was no increasing trend at the millennium time-scale, probably because of the large CaCO3 content of the Soil. We show that magnetic properties of paddy and non-paddy Soil derived from calcareous sediments are mainly controlled by the changing Soil moisture regime and Soil carbonate status along different paths of Soil development. Our study suggests that differences in Soil moisture regime caused by land use are substantially more important than the period of cultivation.
James G Bockheim - One of the best experts on this subject based on the ideXlab platform.
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mass balance of Soil Evolution on late quaternary marine terraces in coastal oregon
Geoderma, 1998Co-Authors: S J Langleyturnbaugh, James G BockheimAbstract:Mass-balance analysis was used to quantify elemental losses, gains and transformations for a Soil chronosequence developed on elevated marine terraces in south-coastal Oregon. The four Soils analyzed in the study range in age from 80 ka to greater than 250 ka and are Inceptisols, Spodosols and Ultisols. Dominant Soil-forming processes include (1) desilication and loss of base cations from the solum, (2) redistribution of iron and aluminum from surface to subsurface horizons, (3) transformation of iron and aluminum from sand and silt-size fractions to secondary clay and crystalline sesquioxide fractions, and (4) accumulation of organic matter. Silica represents the largest mass loss of any element from the system and varies from −6.48 g/cm2 (11% loss from solum compared to original amount of Si in parent material) to −42.99 g/cm2 (22%) with increasing terrace age. Losses of silica from the sand-size fraction over time (2% to 17%) are accompanied by increases of silica in the clay-size fraction. Base cations represent only a small portion of the Soil mass, but up to 53% (−0.09 g/cm2) of the sodium present in the parent material is lost due to weathering and leaching. Iron and aluminum are redistributed within the sola of younger terraces, during podzolization, but are lost from the older Soils due to intense weathering and leaching over time. The majority of iron is transformed from the sand and silt-size fractions to the crystalline sesquioxide fraction. In contrast, the majority of aluminum lost from the sand and silt-size fractions is transformed to the clay-size fraction.
Peter Finke - One of the best experts on this subject based on the ideXlab platform.
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Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a Soil Evolution model (SoilGen2.25)
Biogeosciences, 2015Co-Authors: Emmanuel Opolot, Peter FinkeAbstract:Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic Soil Evolution models. This study applies a mechanistic Soil Evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other Soil-forming processes and factors. The SoilGen Soil Evolution model is a 1-D model developed to simulate the time-depth Evolution of Soil properties as a function of various Soil-forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling, and bioturbation) driven by Soil-forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although Soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the Soil solution composition play an equally important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates possibly due to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore a need to include secondary mineral precipitation mechanism in our formulation. In addition, there is a need for a more detailed study that is specific to field sites with detailed measurements of silicate mineral dissolution rates, climate, hydrology, and mineralogy to enable the calibration and validation of the model. Nevertheless, this study is another important step to demonstrate the critical need to couple different Soil-forming processes with chemical weathering in order to explain differences observed between laboratory and field measured silicate mineral dissolution rates.
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Modeling Soil genesis at pedon and landscape scales: Achievements and problems
Quaternary International, 2015Co-Authors: Emmanuel Opolot, Peter FinkeAbstract:Modeling Soil Evolution is an important step towards understanding the complexity of the Soil system and its interaction with the other systems. The major challenge confronted by pedologists until now is the ability to develop models capable of describing the complete complexity of the Soil system. This paper presents the state of art overview of such a Soil Evolution model, SoilGen, its applications and limitations. In addition, the paper gives an overview of how the SoilGen model may be linked to landscape Evolution models to model Soilscape development. SoilGen is a mechanistic pedogenetic model in which Soil forming processes such as clay migration, decalcification, carbon cycling, bioturbation, physical and chemical weathering coupled with water flow are simulated at multi-millennium time scale. The model has been calibrated and undergone extensive field testing, giving reasonable results at both pedon and landscape scales. However discrepancies between observed and simulated Soil properties such as base saturation (BS), cation exchange capacity (CEC) and pH have been reported. These have been attributed partly to simplification of Soil forming processes particularly in the weathering and chemical systems. There is therefore a need to extend the description of chemical and weathering systems in the SoilGen model. These extensions will not only improve model performance but will also enlarge its application range in simulating the genesis of typical features of more than half of the WRB-Reference Soil Groups. We also note here that although landscape Evolution models have been successfully applied to model Soil production and distribution, simplified and/or incomplete description of Soil forming processes remain major limitations. We therefore add to the voices in scientific literature calling for integration of pedon and landscape scale models. In addition there is critical need for high quality chronosequence, climosequence, and toposequence profile datasets to enhance calibration and validation of Soil Evolution models.
Christopher J. Lewis - One of the best experts on this subject based on the ideXlab platform.
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the mass balance of Soil Evolution on late quaternary marine terraces northern california
Geological Society of America Bulletin, 1992Co-Authors: Dorothy J. Merritts, Oliver A. Chadwick, David M. Hendricks, George H. Brimhall, Christopher J. LewisAbstract:Mass-balance interpretation of a Soil chronosequence provides a means of quantifying elemental addition, removal, and transformation that occur in Soils from a flight of marine terraces in northern California. Six Soil profiles that range in age from several to 240,000 yr are developed in unconsolidated, sandy- marine, and eolian parent material deposited on bedrock marine platforms. Soil Evolution is dominated by (1) open-system depletion of Si, Ca, Mg, K, and Na; (2) open-system enrichment of P in surface Soil horizons; (3) relative immobility of Fe and Al; and (4) transformation of Fe, Si, and Al in the parent material to secondary clay minerals and sesquioxides. Net mass losses of bases and Si are generally uniform with depth and substantial—in some cases approaching 100%; however, the rate of loss of each element differs markedly, causing the ranking of each by relative abundance to shift with time. Loss of Si from the sand fraction by dissolution and particle-size diminution, from ∼100% to 80% to 90% to <10% concurrently with an increase of AI in the organic sesquioxide and clay phases, to 10% and 50%, respectively, while only minor increases occur in the nonorganic sesquioxide phases.
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Deformational Mass Transport and Invasive Processes in Soil Evolution
Science, 1992Co-Authors: George H. Brimhall, Oliver A. Chadwick, David M. Hendricks, Christopher J. Lewis, William Compston, Ian S. Williams, Kathy J. Danti, William E. Dietrich, Mary E. Power, James BrattAbstract:Soils are differentiated vertically by coupled chemical, mechanical, and biological transport processes. Soil properties vary with depth, depending on the subsurface stresses, the extent of mixing, and the balance between mass removal in solution or suspension and mass accumulation near the surface. Channels left by decayed roots and burrowing animals allow organic and inorganic detritus and precipitates to move through the Soil from above. Accumulation occurs at depths where small pores restrict further passage. Consecutive phases of translocation and root growth stir the Soil; these processes constitute an invasive dilatational process that leads to positive cumulative strains. In contrast, below the depth of root penetration and mass additions, mineral dissolution by descending organic acids leads to internal collapse under overburden load. This softened and condensed precursor horizon is transformed into Soil by biological activity, which stirs and expands the evolving residuum by invasion by roots and macropore networks that allows mixing of materials from above.
Laiming Huang - One of the best experts on this subject based on the ideXlab platform.
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phases and rates of iron and magnetism changes during paddy Soil development on calcareous marine sediment and acid quaternary red clay
Scientific Reports, 2018Co-Authors: Laiming Huang, Liu-mei Chen, Mingan Shao, Gan-lin ZhangAbstract:Dynamic changes in Fe oxides and magnetic properties during natural pedogenesis are well documented, but variations and controls of Fe and magnetism changes during anthropedogenesis of paddy Soils strongly affected by human activities remain poorly understood. We investigated temporal changes in different Fe pools and magnetic parameters in Soil profiles from two contrasting paddy Soil chronosequences developed on calcareous marine sediment and acid Quaternary red clay in Southern China to understand the directions, phases and rates of Fe and magnetism Evolution in Anthrosols. Results showed that paddy Soil Evolution under the influence of artificial submergence and drainage caused changes in Soil moisture regimes and redox conditions with both time and depth that controlled Fe transport and redistribution, leading to increasing profile differentiation of Fe oxides, rapid decrease of magnetic parameters, and formation of diagnostic horizons and features, irrespective of the different parent materials. However, the initial parent material characteristics (pH, Fe content and composition, weathering degree and landscape positions) exerted a strong influence on the rates and trajectories of Fe oxides Evolution as well as the phases and rates of magnetism changes. This influence diminished with time as prolonged rice cultivation drove paddy Soil evolving to common pedogenic features.
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Variations and controls of iron oxides and isotope compositions during paddy Soil Evolution over a millennial time scale
Chemical Geology, 2018Co-Authors: Laiming Huang, Aaron Thompson, Gan-lin Zhang, Xiaoxu Jia, Fang Huang, Min-an Shao, Liu-mei ChenAbstract:Abstract A paddy Soil chronosequence consisting of five profiles derived from calcareous marine sediments with cultivation history from 0 to 1000 years was studied to understand the underlying mechanisms and processes controlling the millennial scale Fe Evolution. We evaluated the chronosequencial changes in depth distribution of Fe oxide contents and Fe isotopic compositions. Results showed that paddy Soil Evolution under the influence of periodic flooding and groundwater fluctuation resulted with time in variations of Soil moisture regime and redox condition that control Fe mobilization, translocation and redistribution, leading to enhanced profile differentiation of Fe oxides and measurable Fe isotope fractionation. Total Fe and oxide bound Fe as well as their differentiation between surface and subsurface horizons increased as paddy Soils age, leading to the formation of diagnostic horizons and features characterizing Fe distribution and redistribution. Selective extractions showed that the weakly-bound, oxide-bound and silicate bound Fe corresponded to 1–16%, 8–46%, and 52–91% of the total Fe, respectively, and these proportions varied with both time and depth due to the redox-related Fe transformation and translocation. δ 56 Fe values in the studied paddy Soil chronosequence ranged from − 0.01‰ to 0.18‰ and exhibited a strong negative correlation with the logarithm of total Fe concentrations, suggesting mass-dependent Fe isotope fractionation occurred as a result of the preferential removal of lighter Fe isotopes during long-term paddy Soil Evolution under the predominant reducing conditions. However, the Fe isotopic ratio of a specific paddy Soil horizon was a result of a complex interaction of different processes, which were summarized and interpreted in our proposed conceptual model. Comparison of Fe isotopic compositions in the worldwide Soils demonstrated that Fe isotopes can evidence Fe transfer and pinpoint the factors and processes that control Fe mobilization and redistribution particularly in Soils with changing moisture regimes and redox conditions. Our findings provide new insights into the behavior and geochemical cycle of Fe at the Earth's surface strongly affected by human activities and contributes to an improved understanding of how anthropedogenesis affects Fe Evolution in the Earth's Critical Zone.
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pedogenesis significantly decreases the stability of water dispersible Soil colloids in a humid tropical region
Geoderma, 2016Co-Authors: Laiming Huang, David G. Rossiter, Mingan Shao, Xinhui Zhang, Gan-lin ZhangAbstract:Abstract The stability of Soil colloids influences Soil physicochemical properties, Soil development, and transfer of nutrients and contaminants to surface and ground waters. A better understanding of Soil colloids stability dynamics during Soil Evolution is important for the evaluation of Soil's capacity to retain nutrients and/or accommodate toxic contaminants. This study was aimed to determine changes in the stability of water-dispersible Soil colloids that accompany mineral transformation and surface charge Evolution during pedogenesis using a well characterized chronosequence derived from basalt in the humid tropical region of Hainan Island, South China. The results demonstrated that the pH-dependent colloid stability decreased significantly with tropical Soil development, which we attribute to the substantial changes in clay mineral compositions and colloid surface charge properties. Clay minerals in the studied chronosequence were characterized by an increase of kaolinite, gibbsite and Fe oxides and a decrease of quartz and halloysite towards more advanced stages of weathering, which resulted in the decline of permanent negative charges in the older Soils. The point of zero charge (pHPZC) increased while ∆ pH decreased across the tropical Soil chronosequence, being in good agreement with the observed lower colloid stability in aged Soils dominated by kaolinitic minerals. Our study of colloid stability at long-term pedogenic time scale suggests young tropical Soils (
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The use of chronosequences in studies of paddy Soil Evolution: A review
Geoderma, 2014Co-Authors: Laiming Huang, Aaron Thompson, Gan-lin Zhang, Liu-mei Chen, Guang-zhong Han, Zi-tong GongAbstract:article i nfo Chronosequencesand associated space-for-time substitutionsare animportant and fruitful means for investigat- ing the rates and directions of Soil and ecosystem Evolution across multiple time-scales ranging from decades to millions of years. Thispaperreviews the useof chronosequencesfor studying biogeochemistry of paddy Soil evo- lution to improve our understanding of the fundamental processes, the dynamic changes in Soil properties and the associatedenvironmentalthresholdsatdifferentstagesofpaddySoilEvolutionundertheintensiveanthropo- genic managements. Rice paddy cultivation results in accumulations of various nutrients (e.g. organic carbon, ni- trogen, and phosphorus) over a much longer time period than predicted by typical long-term (b50 years) field experiments, although it is not clear how long it takes paddy Soils with different origins to reach a steady-state of these important nutrients. Extensive investigations of a 2000-year paddy Soil chronosequence derived from calcareous marine sediments in the coastal region of Zhejiang Province (P.R. China) illustrate three phases of paddy Soil Evolution and the associated pedogenic thresholds: an initial phase during the first few decades dom- inated by rapid desalinization, loss of magnetic susceptibility, accumulation of topSoil organic matter and forma- tion of a compacted plow pan due to extrinsic thresholds resulting from anthropogenic activities; the second phaselastsseveralcenturiescomprisingFeandclayenrichmentintheilluvialhorizon,andthelossofphosphorus
