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At least 667 records · Page 37Linked to original sources
USGS2016

Soil amplification with a strong impedance contrast: Boston, Massachusetts

In this study, we evaluate the effect of strong sediment/bedrock impedance contrasts on soil amplification in Boston, Massachusetts, for typical sites along the Charles and Mystic Rivers. These sites can be characterized by artificial fill overlying marine sediments overlying glacial till and bedrock, where the depth to bedrock ranges from 20 to 80 m. The marine sediments generally consist of organic silts, sand, and Boston Blue Clay. We chose these sites because they represent typical foundation conditions in the city of Boston, and the soil conditions are similar to other high impedance contrast environments. The sediment/bedrock interface in this region results in an impedance ratio on the order of ten, which in turn results in a significant amplification of the ground motion. Using stratigraphic information derived from numerous boreholes across the region paired with geologic and geomorphologic constraints, we develop a depth-to-bedrock model for the greater Boston region. Using shear-wave velocity profiles from 30 locations, we develop average velocity profiles for sites mapped as artificial fill, glaciofluvial deposits, and bedrock. By pairing the depth-to-bedrock model with the surficial geology and the average shear-wave velocity profiles, we can predict soil amplification in Boston. We compare linear and equivalent-linear site response predictions for a soil layer of varying thickness over bedrock, and assess the effects of varying the bedrock shear-wave velocity (V Sb ) and quality factor (Q). In a moderate seismicity region like Boston, many earthquakes will result in ground motions that can be modeled with linear site response methods. We also assess the effect of bedrock depth on soil amplification for a generic soil profile in artificial fill, using both linear and equivalent-linear site response models. Finally, we assess the accuracy of the model results by comparing the predicted (linear site response) and observed site response at the Northeastern University (NEU) vertical seismometer array during the 2011 M 5.8 Mineral, Virginia, earthquake. Site response at the NEU vertical array results in amplification on the order of 10 times at a period between 0.7-0.8 s. The results from this study provide evidence that the mean short-period and mean intermediate-period amplification used in design codes (i.e., from the F a and F v site coefficients) may underpredict soil amplification in strong impedance contrast environments such as Boston.

Massachusetts↗
USGS2004

The effect of soil composition and hydration on the bioavailability and toxicity of cadmium to hibernating juvenile American toads ( Bufo americanus )

The soil ecotoxicology literature has focused primarily on a few major taxa, to the neglect of other fossorial organisms such as amphibians. We selected cadmium (Cd) and the American toad ( Bufo americanus ) as a model contaminant and biological species to assess the impact of soil contamination on amphibian hibernation survival and post-hibernation condition. Soil sand composition (50, 70, 90%) and hydration (100, 150% water holding capacity (WHC)) were manipulated in addition to Cd concentration (0, 56, 165, 483 μg/g) to determine whether these soil properties affect toxicity. Soil Cd concentration significantly reduced survival and locomotor performance, and was correlated negatively with percent mass loss and positively with whole body Cd concentration. Higher sand content resulted in less mass loss and greater Cd uptake. Toads that were hibernated in 50% sand hydrated to 100% WHC had higher survival, less mass loss, and better sprint performance than those hibernated in 50% sand, 150% WHC. This study demonstrates that concentrations of Cd found in soil at highly contaminated sites can be bioaccumulated by hibernating amphibians and may reduce fitness. Differences in microhabitat use may cause species to vary in their exposure and susceptibility to soil contamination. The toxicity of Cd to amphibians could be greater in natural systems where there are multiple stressors and fluctuations in environmental variables.

Environmental Pollution↗
USGS2015

Organic amendments for risk mitigation of organochlorine pesticide residues in old orchard soils

Performance of compost and biochar amendments for in situ risk mitigation of aged DDT, DDE and dieldrin residues in an old orchard soil was examined. The change in bioavailability of pesticide residues to Lumbricus terrestris L. relative to the unamended control soil was assessed using 4-L soil microcosms with and without plant cover in a 48-day experiment. The use of aged dairy manure compost and biosolids compost was found to be effective, especially in the planted treatments, at lowering the bioavailability factor (BAF) by 18–39%; however, BAF results for DDT in the unplanted soil treatments were unaffected or increased. The pine chip biochar utilized in this experiment was ineffective at lower the BAF of pesticides in the soil. The US EPA Soil Screening Level approach was used with our measured values. Addition of 10% of the aged dairy manure compost reduced the average hazard quotient values to below 1.0 for DDT + DDE and dieldrin. Results indicate this sustainable approach is appropriate to minimize risks to wildlife in areas of marginal organochlorine pesticide contamination. Application of this remediation approach has potential for use internationally in areas where historical pesticide contamination of soils remains a threat to wildlife populations.

Maryland↗
USGS2015

Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model

Mass balance models have become standard tools for characterizing element gains and losses and volumetric change during weathering and soil development. However, they rely on the assumption of complete immobility for an index element such as Ti or Zr. Here we describe a dual-phase mass balance model that eliminates the need for an assumption of immobility and in the process quantifies the contribution of aqueous versus colloidal element transfer. In the model, the high field strength elements Ti and Zr are assumed to be mobile only as suspended solids (colloids) and can therefore be used to distinguish elemental redistribution via colloids from redistribution via dissolved aqueous solutes. Calculations are based upon element concentrations in soil, parent material, and colloids dispersed from soil in the laboratory. We illustrate the utility of this model using a catena in South Africa. Traditional mass balance models systematically distort elemental gains and losses and changes in soil volume in this catena due to significant redistribution of Zr-bearing colloids. Applying the dual-phase model accounts for this colloidal redistribution and we find that the process accounts for a substantial portion of the major element (e.g., Al, Fe and Si) loss from eluvial soil. In addition, we find that in illuvial soils along this catena, gains of colloidal material significantly offset aqueous elemental loss. In other settings, processes such as accumulation of exogenous dust can mimic the geochemical effects of colloid redistribution and we suggest strategies for distinguishing between the two. The movement of clays and colloidal material is a major process in weathering and pedogenesis; the mass balance model presented here is a tool for quantifying effects of that process over time scales of soil development.

Geochimica et Cosmochimica Acta↗
USGS2008

Soil morphology of a debris flow chronosequence in a coniferous forest, southern California, USA

Soils on a series of debris flow deposits, ranging from < 1 to 244??years old, were described and sampled in order to investigate the early stages of soil development. The parent material at the site is debris flow regolith, composed mainly of gneiss, the soil moisture regime is xeric, and the vegetation is mixed coniferous forest. Ages of the deposits were assessed using dendrochronology. Morphologic trends in the organic horizons included a thickening of the humus form over time, along with the development of Fm and Hr horizons. The humus forms underwent a progression from Mormodors (20??years old), to Hemimors (26-101??years old), and finally Lignomors (163??years old) and Resimors (184-244??years old). Changes in physical properties of the uppermost mineral horizons as a function of increasing age included a decrease in the volume of coarse fragments, a linear decrease in bulk density, and a darkening and reddening of the soil color. No significant soil development took place in the subsoil during the time span of this chronosequence. The soils described were classified as Typic Xerofluvents and Typic Xerorthents (Regosols and Leptosols). Buried A horizons were observed in many of the soils. Where the A horizons could be linked to dendrochronology to assess the age of the buried surface, we found that the properties of the buried A horizons do not serve as a good indicator of the age of the surface. This study suggests rapid development of the humus form profile (organic horizons and A horizon) following debris flow deposition and rapid degradation of these horizons when the debris flow surface is buried. ?? 2008 Elsevier B.V.

Geoderma↗
USGS2011

Geochemical and isotopic study of soils and waters from an Italian contaminated site: Agro Aversano (Campania)

Lead isotope applications have been widely used in recent years in environmental studies conducted on different kinds of sampled media. In the present paper, Pb isotope ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1. m), 11 stream waters and 4 groundwaters were collected. Major element concentrations in sampled media have been analyzed by the ICP-MS technique. Surface soils (20 samples), all soil profiles and all waters have been also analyzed for Pb isotope compositions by thermal ionization (TIMS). The geochemical data were assessed using statistic methods and cartographically elaborated in order to have a clear picture of the level of disturbance of the area. Pb isotopic data were studied to discriminate between anthropogenic and geologic sources. Our results show that As (5.6-25.6. mg/kg), Cu (9-677. mg/kg), Pb (22-193. mg/kg), Tl (0.53-3.62. mg/kg), V (26-142. mg/kg) and Zn (34-215. mg//kg) contents in analyzed soils, exceed the intervention limits fixed by the Italian Environmental Law for residential areas in some of the sampled sites, while intervention limit for industrial areas is exceeded only for Cu concentrations. Lead isotopic data, show that there is a high similarity between the ratios measured in the leached soil samples and those deriving from anthropic activities. This similarity with anthropogenic Pb is also evident in the ratios measured in both groundwater and stream water samples. ?? 2010 Elsevier B.V.

Journal of Geochemical Exploration↗
USGS2013

Effects of mining-associated lead and zinc soil contamination on native floristic quality

We assessed the quality of plant communities across a range of lead (Pb) and zinc (Zn) soil concentrations at a variety of sites associated with Pb mining in southeast Missouri, USA. In a novel application, two standard floristic quality measures, Mean Coefficient of Conservatism (Mean C) and Floristic Quality Index (FQI), were examined in relation to concentrations of Pb and Zn, soil nutrients, and other soil characteristics. Nonmetric Multidimensional Scaling and Regression Tree Analyses identified soil Pb and Zn concentrations as primary explanatory variables for plant community composition and indicated negative relationships between soil metals concentrations and both Mean C and FQI. Univariate regression also demonstrated significant negative relationships between metals concentrations and floristic quality. The negative effects of metals in native soils with otherwise relatively undisturbed conditions indicate that elevated soil metals concentrations adversely affect native floristic quality where no other human disturbance is evident.

Missouri↗
USGS2016

Adaptive management for soil ecosystem services

Ecosystem services provided by soil include regulation of the atmosphere and climate, primary (including agricultural) production, waste processing, decomposition, nutrient conservation, water purification, erosion control, medical resources, pest control, and disease mitigation. The simultaneous production of these multiple services arises from complex interactions among diverse aboveground and belowground communities across multiple scales. When a system is mismanaged, non-linear and persistent losses in ecosystem services can arise. Adaptive management is an approach to management designed to reduce uncertainty as management proceeds. By developing alternative hypotheses, testing these hypotheses and adjusting management in response to outcomes, managers can probe dynamic mechanistic relationships among aboveground and belowground soil system components. In doing so, soil ecosystem services can be preserved and critical ecological thresholds avoided. Here, we present an adaptive management framework designed to reduce uncertainty surrounding the soil system, even when soil ecosystem services production is not the explicit management objective, so that managers can reach their management goals without undermining soil multifunctionality or contributing to an irreversible loss of soil ecosystem services.

Journal of Environmental Management↗
USGS2023

Water-soluble organic carbon release from mineral soils and sediments in an irrigated agricultural system

Water interactions with soil and vegetation are greatly altered in agricultural watersheds compared to natural landscapes, which impacts sources and fates of organic carbon (OC). While mineral soil horizons in natural ecosystems primarily act as filters for dissolved organic carbon (DOC) leached from organic surface horizons, tilled soils largely lack an organic horizon and their mineral horizons therefore act as a source for both DOC and sediment to surface waters. Irrigated watersheds highlight this difference, as DOC and total suspended sediment (TSS) concentrations simultaneously increase during the low-discharge irrigation season, suggesting that sediment-associated OC may constitute a significant source of DOC. While water-soluble OC (WSOC) from sediments and soils has been found to be compositionally similar to stream DOC, these contributions remain poorly quantified in agricultural streams. To address this, we conducted abiotic solubilization experiments using sediments (suspended and bed) and soils from an irrigated agricultural watershed in northern California, USA. Sediments (R 2 > 0.99) and soils (0.74 < R 2 < 0.89) displayed linear solubilization behaviors over the range of concentrations tested. Suspended sediment from the irrigation season exhibited the largest solubilization efficiency (10.9 ± 1.6% TOC sediment solubilized) and potential (1.79 ± 0.26 mg WSOC g −1 dry sediment), followed by suspended sediment from a winter storm, then bed sediment and soils. Successive solubilization experiments increased the total release of WSOC by ∼50%, but most (88–97%) of the solid-phase OC remained insoluble in water. Using these solubilization potential estimates and measured TSS concentrations, we estimated that WSOC from suspended sediment in streams represented 4–7% of the annual DOC export from the watershed. However, field sediment export is much higher than what is represented by suspended sediment in the water column, therefore field-scale contributions from sediments could be much higher than estimated.

California↗
USGS2026

Generating geochemical and mineralogy distributions of soil in the conterminous United States using Bayesian hierarchical spatial models

Characterizing geochemical and mineralogical soil distributions across large spatial extents is essential for understanding mineral resources, ecosystem processes, and environmental risks. Rasters of soil geochemical distributions for the conterminous United States, however, are limited. We present a Bayesian modeling workflow and tool for generating predictive geochemical and mineralogy distribution maps for the conterminous United States using integrated nested Laplace approximation (INLA) with the stochastic partial differential equation approach. By modeling soil geostatistical data with environmental covariates (soil properties, topography, climate, and land cover), we generate predictive distributions of soil geochemistry that can be mapped or extracted for further analyses. As an example, we model the spatial distribution of trace elements in soil relevant to vertebrate health (cobalt, copper, iron, manganese, selenium, and zinc) and provide a workflow that can be used to generate and visualize predictive distributions of 39 other major and trace elements and 21 minerals of the soil survey, supporting a variety of ecological, environmental, and agricultural applications.

MethodsX↗
USGS2016

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil

Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14 spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.

Journal of Microbiological Methods↗
USGS2009

N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15 N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by 15 N NMR. Liquid state 15 N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection ( 1 H- 15 N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

Organic Geochemistry↗
USGS2022

A quantitative soil-geomorphic framework for developing and mapping ecological site groups

Land management decisions need context about how landscapes will respond to different circumstances or actions. As ecologists’ understanding of nonlinear ecological dynamics has evolved into state-and-transition models (STMs), they have put more emphasis on defining and mapping the soil, geomorphological, and climate parameters that mediate these dynamics. The US Department of Agriculture Natural Resources Conservation Service ecological site descriptions (ESDs) have become the foremost system in classifying lands into ecological units based on STMs. However, an exhaustive inventory of ESDs has proved challenging to complete in the United States, and there have been questions about the consistency of detail in areas completed and the ability to objectively support some assertions made in existing ESDs. To address these issues, this study examines ESDs in the diverse Upper Colorado River region, where ESDs are only partially complete, to look at quantitative approaches to generalizing ecological site concepts based on unifying underlying soil, geomorphology, and climate patterns. Using existing ESDs and vegetation monitoring plot data, results show that a simple hierarchical soil geomorphic unit (SGU) framework based on topographic mediation of moisture, soil salinity, soil depth, slope, rock content, and soil texture can represent much of the ecological dynamics cataloged in ESDs. Analyses of reference plant production data, ecological state attribution, and regional monitoring data show that the new SGUs represent more variation than common climate parameters. This study also included predictively mapping SGUs at 30-m resolution (Kappa of 0.53, 74% agreement with top two predictions in validation). An optimized combination of SGUs with climate zones derived from an aridity index and maximum temperature of the hottest month resulted in an ecological site group framework that condensed over 826 unique ecological site records at various stages of completeness in the regional soil survey down to 35 intuitive and mappable ecological site groups.

Rangeland Ecology and Management↗
USGS2010

Multivariate analysis of the geochemistry and mineralogy of soils along two continental-scale transects in North America

Soils collected in 2004 along two North American continental-scale transects were subjected to geochemical and mineralogical analyses. In previous interpretations of these analyses, data were expressed in weight percent and parts per million, and thus were subject to the effect of the constant-sum phenomenon. In a new approach to the data, this effect was removed by using centered log-ratio transformations to 'open' the mineralogical and geochemical arrays. Multivariate analyses, including principal component and linear discriminant analyses, of the centered log-ratio data reveal the effects of soil-forming processes, including soil parent material, weathering, and soil age, at the continental-scale of the data arrays that were not readily apparent in the more conventionally presented data. Linear discriminant analysis of the data arrays indicates that the majority of the soil samples collected along the transects can be more successfully classified with Level 1 ecological regional-scale classification by the soil geochemistry than soil mineralogy. A primary objective of this study is to discover and describe, in a parsimonious way, geochemical processes that are both independent and inter-dependent and manifested through compositional data including estimates of the elements and corresponding mineralogy. ?? 2010.

Science of the Total Environment↗
USGS2012

Earthworm bioassays and seedling emergence for monitoring toxicity, aging and bioaccumulation of anthropogenic waste indicator compounds in biosolids-amended soil

Land application of biosolids (treated sewage sludge) can be an important route for introducing xenobiotic compounds into terrestrial environments. There is a paucity of available information on the effects of biosolids amendment on terrestrial organisms. In this study, the influence of biosolids and biosolids aging on earthworm (Eisenia fetida) reproduction and survival and lettuce (Lactuca sativa) seedling emergence was investigated. Earthworms were exposed to soils amended with varying quantities of biosolids (0, 1, 2, 3, or 4% dry mass). To investigate the influence of biosolids aging, the biosolids used in the study were aged for differing lengths of time (2 or 8 weeks) prior to exposure. All of the adult earthworms survived in the biosolids–amended soils at all concentrations that were aged for 2 weeks; however, only 20% of the adults survived in the soil amended with the highest concentration of biosolids and aged for 8 weeks. Reproduction as measured by mean number of juveniles and unhatched cocoons produced per treatment correlated inversely with biosolids concentration, although the effects were generally more pronounced in the 8-week aged biosolids–soil samples. Latent seedling emergence and reduced seedling fitness correlated inversely with biosolids concentration, but these effects were tempered in the 8-week aged versus the 2-week aged soil–biosolids mixtures. Anthropogenic waste indicator compounds (AWIs) were measured in the biosolids, biosolids–soil mixtures, and earthworm samples. Where possible, bioaccumulation factors (BAFs) were calculated or estimated. A wide variety of AWIs were detected in the biosolids (51 AWIs) and earthworm samples (≤ 19 AWI). The earthworms exposed to the 8-week aged biosolids–soil mixtures tended to accumulate greater quantities of AWIs compared to the 2-week aged mixture, suggesting that the bioavailability of some AWIs was enhanced with aging. The BAFs for a given AWI varied with treatment. Notably large BAFs were determined for some AWIs. For example, the maximum BAF determined for para-cresol, methyl salicylate, bisphenol-A, and cholesterol was greater than 100 in some treatments.

Science of the Total Environment↗
USGS2012

Modeling of soil erosion and sediment transport in the East River Basin in southern China

Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

Science of the Total Environment↗
USGS2016

Modeled effects of soil acidification on long-term ecological and economic outcomes for managed forests in the Adirondack region (USA)

Sugar maple ( Acer saccharum ) is among the most ecologically and economically important tree species in North America, and its growth and regeneration is often the focus of silvicultural practices in northern hardwood forests. A key stressor for sugar maple (SM) is acid rain, which depletes base cations from poorly-buffered forest soils and has been associated with much lower SM vigor, growth, and recruitment. However, the potential interactions between forest management and soil acidification &ndash; and their implications for the sustainability of SM and its economic and cultural benefits &ndash; have not been investigated. In this study, we simulated the development of 50 extant SM stands in the western Adirondack region of NY (USA) for 100 years under different soil chemical conditions and silvicultural prescriptions. We found that interactions between management prescription and soil base saturation will strongly shape the ability to maintain SM in managed forests. Below 12% base saturation, SM did not regenerate sufficiently after harvest and was replaced mainly by red maple ( Acer rubrum ) and American beech ( Fagus grandifolia ). Loss of SM on acid-impaired sites was predicted regardless of whether the shelterwood or diameter-limit prescriptions were used. On soils with sufficient base saturation, models predicted that SM will regenerate after harvest and be sustained for future rotations. We then estimated how these different post-harvest outcomes, mediated by acid impairment of forest soils, would affect the potential monetary value of ecosystem services provided by SM forests. Model simulations indicated that a management strategy focused on syrup production &ndash; although not feasible across the vast areas where acid impairment has occurred &ndash; may generate the greatest economic return. Although pollution from acid rain is declining, its long-term legacy in forest soils will shape future options for sustainable forestry and ecosystem stewardship in the northern hardwood forests of North America.

New York↗
USGS2020

Soil organic carbon stocks and sequestration rates of inland, freshwater wetlands: Sources of variability and uncertainty

Impacts of land use, specifically soil disturbance, are linked to reductions of soil organic carbon (SOC) stocks. Correspondingly, ecosystem restoration is promoted to sequester SOC to mitigate anthropogenic greenhouse gas emissions, which are exacerbating global climate change. Restored wetlands have relatively high potential to sequester carbon compared to other ecosystems, but SOC accumulation rates are variable, which leads to high uncertainty in sequestration rates. To assess soil properties and carbon sequestration rates of freshwater mineral soil wetlands, we analyzed an extensive database of SOC concentrations from the Prairie Pothole Region (549 wetlands over 160,000 km 2 ), which is considered one of the largest wetland ecosystems in North America. We demonstrate that SOC of wetland catchments varies among inner, transition, toe slope, and upland landscape positions (LSPs), as well as among land uses and soil depth segments. Soil organic carbon concentrations were greatest in the inner portion of the catchment (66 Mg ha −1 ) and progressively decrease towards the upland LSP (43 Mg ha −1 ). We also conducted a regional extrapolation based on LSP- and land-use-specific SOC stocks, and estimated that wetland and upland areas of PPR wetland catchments contain 141 and 178 Tg of SOC in the upper 15 cm of the soil profile, respectively. Regressing SOC by restoration age (years restored) showed that sequestration rates, which differ by LSP and depth, ranged from 0.35 to 1.10 Mg ha −1 year −1 . Using these SOC sequestration rates, along with data from natural and cropland reference sites, we estimated that it takes 20 to 64 years for SOC levels of restored wetlands to return to natural reference conditions, depending on LSP and depth segment. Accounting for LSP reduces uncertainty and should refine future assessments of the greenhouse gas mitigation potential from wetland restoration.

Iowa, Minnesota, Montana, North Dakota, South Dako↗