bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Measurements of Denitrification in Constructed Wetlands
Authors: Xue Yuan , Kovacic David A. , David Mark B. , Gentry Lowell E. , Mulvaney Richard L. , Lindau Charles W. 
Published: July 2010

AbstractQuantitative estimates of denitrification are needed in designing artificial wetlands to optimize nitrate (NO−3) removal. Acetylene blockage and 15N‐tracer methods were employed to quantify denitrification in constructed wetlands receiving agricultural tile drainage, using plastic tubes to enclose in situ mesocosms. Estimates were also made through NO−3 disappearance from mesocosm water columns. The 15N and C2H2 methods yielded comparable rates. At 4 to 25°C, and with 9 to 20 mg NO−3‐N L−1 initially in the mesocosm water columns, denitrification rates by the C2H2 technique ranged from 2.0 to 11.8 mg N m−2 h−1. In the June–August 15N experiment, when wetland NO−3 was below detection, a time series of denitrification rates followed a bell‐shaped curve after a pulse input of NO−3 (∼15 mg N L−1, 70 atom% 15N). The maximal denitrification rate (9.3 mg N m−1 h−1) was observed 5.4 d after the pulse. After 33 d, 58% of the 15NO−3 had been evolved as N2, only ∼0.1% as N2O; 6 to 10% was recovered in plant shoots and as organic N in the upper 5 cm of sediment. From 32 to 36% of the 15NO−3 spike was not recovered, and presumably seeped into the sediments. The NO3 disappearance rates in the water column ranged from 12 to 63 mg N m−2 h−1 at 11 to 27°C. Because water infiltration carries NO−3 through the anaerobic sediment/water interface for denitrification, a subsurface‐flow wetland may denitrify more NO−3 than a surface‐flow wetland.
Soluble Barium in Barite and Phosphogypsum Amended Mississippi River Alluvial Sediment
Authors: Carbonell A. A. , Pulido R. , DeLaune R. D. , Patrick W. H. 
Published: July 2010

AbstractBarite (BaSO4), a density control material used in petroleum drilling fluids, can enter coastal and wetland environments. Because of its low solubility, it has been generally concluded that barium (Ba) will not leach into groundwater supplies, nor will it be taken up in significant quantities by plants and aquatic organisms. Such conclusions were mainly based on experiments conducted at neutral pH values and under oxidized conditions. The influence of pH and redox potential (Eh) on solubility of Ba from barite and phosphogypsum (PG) in Louisiana Mississippi River alluvial sediment was examined. Sediment suspensions containing barite or PG were incubated under oxidized and reduced conditions at pH 8, 7, 6, 5, and 4. The amount of Ba in solution at each combination (Eh‐pH) was measured. Results demonstrated that a combination of low pH and highly anaerobic conditions resulted in a release of Ba to the sediment solution. If low pH and anaerobic environment happen simultaneously, barite can account for significant levels of dissolved Ba entering the environment. In this study, approximately 4.4% of the total native Ba present in Louisiana Mississippi River alluvial sediment was converted to a soluble form under acidic and anaerobic conditions, compared to approximately 0.3% under alkaline and either anaerobic or aerobic conditions. Phosphogypsum application to the sediment significantly reduced the level of soluble Ba compared to control sediments, this was attributed to Ba precipitation as insoluble sulfates or sulfides under oxidized and reduced conditions.
Effects of Soil on Trace Metal Leachability from Papermill Ashes and Sludge
Authors: Xiao Chengqing , Ma Lena Q. , Sarigumba Terry 
Published: July 2010

AbstractUnderstanding trace metal leachability is important for successful land application of papermill residues. Trace metal leachability from papermill ashes (Ash 1 and Ash 2) and papermill sludge (Sludge), and the effects of a soil on their leachability were determined by leaching the three papermill residues packed on top of a soil in a column. The leachates were analyzed for pH, electrical conductivity (EC), dissolved organic carbon (DOC), and concentrations of six metals (Cd, Cr, Cu, Pb, Se, and Zn). Ash 1 behaved significantly differently from Ash 2 during the leaching experiment, primarily due to its high pH and Na contents. Application of papermill residues significantly increased the pH, EC, and DOC concentrations in leachates, with Ash 1 having significantly greater impacts than Ash 2 and sludge. Soil columns under alkaline leaching of Ash 1 appeared bleached due to the dissolution of solid‐phase organic matter. Significant amounts of Zn were leached from all papermill residues, whereas significant amounts of Cr, Se, and Cu were leached only in the Ash 1 treatments. The presence of a soil (especially a Bh horizon) generally enhanced metal leachability in the Ash 1 treatments due to the extremely high pH of Ash 1, whereas it decreased metal leachability in the Ash 2 and sludge treatments. Thus, organic matter enhances metal sorption when present as a solid phase, but it increases metal leachability when present in dissolved form under alkaline conditions.
Sorption and Desorption of Copper on Soil Clay Components
Authors: Wu J. , Laird D. A. , Thompson M. L. 
Published: July 2010

AbstractToxic effects have been reported due to the accumulation of Cu in soils receiving long‐term applications of swine (Sus scrofa) manure, sewage, municipal composts, and mining waste. The objective of this study was to quantify sorption and desorption of Cu on various clay and clay‐organic matter fractions separated from a Zook soil (fine, smectitic, mesic Cumulic Vertic Endoaquolls) located in central Iowa. The clay was separated into four particle‐size fractions and portions of each fraction were treated with H2O2 and/or dithionite‐citrate‐bicarbonate (DCB) for removal of organic matter and free‐iron compounds, respectively. A batch‐equilibration technique was employed to evaluate sorption of Cu at pH 6.0 in the presence of 0.01 M CaCl2. The sorption isotherms show that Cu was preferentially sorbed on organic matter associated with the coarse clay fraction of the soil. After removal of organic matter, the fine clay (<0.02 µm) exhibited higher Cu retention than did the coarse (0.2–2.0 µm) and medium clay (0.02–0.2 µm). The DCB treatment created or exposed high‐affinity sites for Cu on the fine clay, but had little effect on Cu sorption for the coarse day. Copper appears to be specifically sorbed on the surfaces of silicate clays in excess of that which can be accounted for by variable charge sites. The results also suggest that Fe oxides may coat lateral surfaces of layer silicates, blocking access of Cu to potential sorption sites. Substantial sorption‐desorption hysteresis was observed for all samples, suggesting that Cu forms high‐energy bonds with both organic matter and layer‐silicate surfaces.
A Type Transfer Function Approach for Regional‐Scale Pesticide Leaching Assessments
Authors: Stewart Iris T. , Loague Keith 
Published: July 2010

AbstractThe objective of this study was the development of a transfer function protocol to obtain quantitative, regional‐scale estimates of groundwater contamination from agricultural chemicals. The Jury transfer function model was extended for the first time to regional scales through the development of ‘type’ transfer functions (TTFs). Type transfer functions are generalized impulse‐response functions, that define not only the response of a particular system that is characterized by a particular soil profile and surface‐water flux, but give a representative response for sufficiently similar systems. For this study TTFs were developed for the Fresno case study. The Fresno case study is a regional‐scale, simulated database of 1,2‐dibromo‐3‐chloropropane (DBCP) leaching for a 1172‐km2 study area in east‐central Fresno County, California. Simulated TTF concentration time series for each DBCP application in every 1‐km2 element of the study area were obtained by scaling the appropriate TTF by the mass of applied solute, the annual recharge, and a correction function accounting for sorption and decay. The results of the TTF simulations were compared with PRZM‐2 simulations for the same study area. The comparison showed that the TTF model (i) only required scaling of a known function once the set of TTFs was identified, (ii) yielded quantitative estimates of peak DBCP concentrations within one order of magnitude of the PRZM‐2 estimates, and (iii) overestimated DBCP concentrations because of a basic TFM formulation and a conservative modeling strategy. The TTF approach is capable of producing quantitative, regional‐scale groundwater vulnerability assessments that compare well to process‐based simulations.
Distributed Watershed Modeling of Design Storms to Identify Nonpoint Source Loading Areas
Authors: Endreny T. A. , Wood E. F. 
Published: July 2010

AbstractWatershed areas that generate nonpoint source (NPS) polluted runoff need to be identified prior to the design of basin‐wide water quality projects. Current watershed‐scale NPS models lack a variable source area (VSA) hydrology routine, and are therefore unable identify spatially dynamic runoff zones. The TOPLATS model used a watertable‐driven VSA hydrology routine to identify runoff zones in a 17.5 km2 agricultural watershed in central Oklahoma. Runoff areas were identified in a static modeling framework as a function of prestorm watertable depth and also in a dynamic modeling framework by simulating basin response to 2, 10, and 25 yr return period 6 h design storms. Variable source area expansion occurred throughout the duration of each 6 h storm and total runoff area increased with design storm intensity. Basin‐average runoff rates of 1 mm h−1 provided little insight into runoff extremes while the spatially distributed analysis identified saturation excess zones with runoff rates equaling effective precipitation. The intersection of agricultural landcover areas with these saturation excess runoff zones targeted the priority potential NPS runoff zones that should be validated with field visits. These intersected areas, labeled as potential NPS runoff zones, were mapped within the watershed to demonstrate spatial analysis options available in TOPLATS for managing complex distributions of watershed runoff. TOPLATS concepts in spatial saturation excess runoff modeling should be incorporated into NPS management models.
Empirical Modeling of Spatial Vulnerability Applied to a Norflurazon Retrospective Well Study in California
Authors: Troiano J. , Marade J. , Spurlock F. 
Published: July 2010

AbstractOne goal of mandated well monitoring in California is to search for residues of active ingredients previously undetected in the state's groundwater. The realization that pesticide residues move into groundwater via several different pathways has led us to develop an empirical approach to delineate vulnerable areas; major climatic and edaphic features of areas where pesticides residues have been detected in well water have been identified on a geographic basis. The objective of this study was to evaluate the use of our empirical model in a retrospective well‐ sampling study for norflurazon, a preemergence herbicide with physical‐chemical properties that indicated potential to move offsite with water. In our modeling approach, sections of land, which are 2.59 km2 areas, were identified as having a greater potential for contamination based on soil and depth‐to‐groundwater (DGW) data. Wells were sampled from a subset of these sections where use of norflurazon was historically the greatest. Norflurazon residue was detected in 8 of 43 wells sampled in Fresno County, California, and in concentrations ranging from 0.07 to 0.69 µg L−1. This result was considered highly successful because residues had not been detected in 18 previous California groundwater studies for other active ingredients, some of which had been detected in other state and federal sampling programs. Location of sampling sites in these previous 18 California studies was based only on pesticide use data. The detections of norflurazon in this study indicated that, even though using an empirical modeling approach appeared to be unorthodox, it enabled us to effectively identify vulnerable areas.
Uncertainty in a Regional‐Scale Assessment of Cadmium Accumulation in the Netherlands
Authors: Tiktak Aaldrik , Leijnse Anton , Vissenberg Harald 
Published: July 2010

AbstractAtmospheric deposition and agricultural activities may cause the cadmium (Cd) content in the rural environment in the Netherlands to exceed legal environmental standards. A simple process‐oriented model, SOACAS, in combination with a Geographical Information System was used to assess the magnitude of the Cd accumulation on a regional scale. The objective of this study was to quantify the uncertainty in the Cd accumulation due to data uncertainty. Another objective was to study whether maps of simulated and observed Cd contents were statistically different when the uncertainty in both maps was considered. From a Monte Carlo analysis we derived that the model behaved virtually linear within the range of model inputs considered, and concluded that first‐order uncertainty analysis (FOUA) was appropriate for mapping prediction uncertainties. The maps created by FOUA indicated that the contribution of individual model parameters to the total uncertainty was soil dependent, and that the pedotransfer function for Cd sorption gave the largest contribution to the total uncertainty. In an earlier analysis we found that in 25% of the total area SOACAS underestimated the average levels of current Cd contents by >50%. The model predictions and the observations were statistically different at a much smaller area (10% of the total area), showing that ignoring uncertainty may result in misleading interpretations when the model is compared with field measurements.
Stochastic Simulation of Pesticide Transport in Heterogeneous Unsaturated Fields
Authors: Wu Q. J. , Workman S. R. 
Published: July 2010

AbstractCommonly used vadose‐zone models typically lack the capability to account for the spatial variability of soil properties that can greatly affect water flow and solute transport. In this study, stochastic techniques were applied to Groundwater Loading Effects of Agricultural Management Systems (GLEAMS), a deterministic vadose‐zone model, to simulate pesticide transport within experimental plots in southern Ohio subject to three different agricultural treatments. A hydrologic environment was discretized vertically into three layers based on the characteristics of the soil horizons. Selected hydrologic parameters in GLEAMS were described within each discretized layer by a random multivariate normal (MVN) vector. Simulations of transport and fate of three commonly used pesticides in the top 1.22‐m root zone were carried out at two levels: (i) single‐value output was obtained by using the mean values of the MVN vector components; and (ii) an empirical probability density function (pdf) was obtained by using the generated MVN vector realizations for each discretized layer. Statistical analyses were conducted to compare the simulation results and field observations, and examine the treatment effect on pesticide transport. Conclusions include: (i) soil spatial heterogeneity significantly affected pesticide movement and caused spatial variation of their distribution, and (ii) the Level 2 stochastic approach resulted in a better prediction of pesticide transport and fate.
Improved Models for Estimating Soil Erosion Rates from Cesium‐137 Measurements
Authors: Walling D. E. , He Q. 
Published: July 2010

AbstractFallout cesium‐137 (137Cs) measurements have been used in investigations of water‐induced soil erosion in a wide range of environments and in many different areas of the world over the past 20 yr. However, the existing calibration procedures commonly used for deriving quantitative estimates of soil redistribution rates from 137Cs measurements involve several limitations and uncertainties. Existing approaches to calibration and their associated limitations and uncertainties are briefly reviewed and improved models for converting 137Cs measurements to estimates of rates of water‐ and tillage‐induced soil redistribution, applicable to both cultivated and undisturbed soils, are proposed. Results obtained from existing field investigations and laboratory experiments indicate that redistribution of fallout 137Cs within the soil profile and across the land surface is influenced by several factors. These include time‐dependent fallout input, initial distribution within the surface layer, post‐depositional redistribution resulting from mechanical, physical, chemical, and biological processes operating in the soil system and the grain size selectivity associated with soil erosion and sediment transport processes. It is important to consider these factors when deriving estimates of soil redistribution rates using the 137Cs technique, and they have been incorporated into the improved models. The use of these models is demonstrated using data from a case study undertaken in a small catchment in Devon, UK, involving both cultivated and undisturbed soils.
Soluble Organic Carbon in a Biosolids‐Amended Mollisol
Authors: Han Nizhou , Thompson Michael L. 
Published: July 2010

AbstractOrganic matter can be mobilized from many sources and transported in soil by precipitation, snowmelt, and water table fluctuations. Knowledge of the potential fluxes of soluble organic C in different kinds of soil is essential to improve global C budgets. We characterized the soluble and suspendable organic matter in a biosolids‐amended fine, smectitic, mesic Cumulic Vertic Endoaquoll under two vegetation treatments: switchgrass (Panicum virgatum L.) and cottonwood‐poplar hybrid (Populus × euramericana—clone NC‐5326). Soil organic C (OC) that was dispersed in 0.1 mM CaCl2 was fractionated according to molecular weight and polarity using dialysis membranes and XAD‐8 resin chromatography. Under both types of vegetation, addition of biosolids increased the amount of soluble OC (SOC) in the soil, particularly under switchgrass. Biosolids application shifted the molecular‐weight distribution of SOC to lower weights (<14 000 Da). The concentrations of hydrophilic OC fractions exceeded those of hydrophobic OC in all treatments, although biosolids application increased the levels of both fractions. As the rate of biosolids addition increased, the 0 to 5 cm zone yielded smaller concentrations of extractable colloidal organic compounds than the 5 to 25 cm zone, and we attributed this to the high amounts of soluble salts introduced by biosolids application. A sequential extraction experiment showed that large amounts of colloidal organic compounds could be mobilized from the soil only after removal of the soluble salts. Our results suggest that biosolids amendments could increase the mobilization of hydrophilic, low‐molecular‐weight compounds in a soil while at the same time limiting the mobility of organic colloids.
Nonylphenol and Estrogenic Activity in Aquatic Environmental Samples
Authors: Tanghe Tom , Devriese Greet , Verstraete Willy 
Published: July 2010

AbstractWe surveyed a series of surface waters and sewage treatment plants in Flanders (north of Belgium) for the presence of estrogenic activity and a xeno‐estrogenic compound para‐nonylphenol (NP), respectively. The surface waters of rural origin, used for drinking water production, were free of significant levels of estrogenic activity and NP (<1 µg/L). Domestic sewage, after proper treatment, appeared to be no major source of this chemical. Yet, in some industrial effluents and surface waters of highly industrialized regions, NP and/or estrogenic activity was prominent, that is, <1 to 122 µg NP/L and 11 to 42 µg NP/L, respectively. This is because of the ongoing use of NP polyethoxylates in industry. The response of the recombinant yeast estrogen assay to the environmental samples tested was not consistent with the detected concentrations of NP. Standard addition of a natural estrogen, 17β‐estradiol, generated no or a reduced response compared to the standard curve concentration. Application of humic acids to standard series of NP and 17β‐estradiol resulted in a dose‐dependent decrease of the estrogenic response. It appears that this bioassay is subject to considerable interferences due to the complexity of environmental samples. Parallel implementation of extensive chemical screening for xenobiotics and use of the bioassay are needed for adequate assessment of the potential estrogenic hazard to avoid false negative evaluations.
Correlating Microbes to Major Odorous Compounds in Swine Manure
Authors: Zhu Jun , Jacobson Larry D. 
Published: July 2010

AbstractMalodor generation from swine manure is complicated by the involvement of many bacterial species that produce an extensive array of volatile organic compounds (VOCs). A lack of understanding of the basic manure microbiology further complicates the problem. This review covers pertinent detailed information about the indigenous bacterial genera in swine manure and their potential for producing odorous volatile compounds. It addresses not only the odorous compounds in swine manure but also the relations between bacterial species and the related compounds. It appears that volatile fatty acids may be the major odorous compounds in swine manure, and two bacterial genera, Eubacterium and Clostridium, are most likely the major contributors to these odorous acids. More research is needed to identify the bacterial species within these two genera to better understand the kinetics of malodor production by the bacteria.
Effects of Acidification on Metal Mobility in a Papermill‐Ash Amended Soil
Authors: Chirenje Tait , Ma Lena Q. 
Published: July 2010

AbstractElevated soil pH due to papermill ash application has adverse effects on forest soils. Column leaching studies were conducted to determine the effects of acidification on trace metal mobility in a papermill‐ash amended soil. Two types of ash, aged and fresh, were used. The aged ash‐soil profile was collected from the field where the ash was mixed with the surface soil to a depth of 47 cm at rates of 896 and 1792 mt ha−1 and left to stand for 1.5 yr. The fresh ash‐soil profile was prepared by mixing fresh ash with the surface soil at the same rates as the aged ash‐soil profiles. The pHs of the ash‐soil profiles were adjusted from 9–10 to 7 and 6 using dilute HNO3. Leachate concentrations of As, Ca, Cd, Cr, Cu, Na, Ni, Se, and dissolved organic carbon (DOC), and pH were measured at the end of 7 and 35 d. Acidification of the aged ash‐soil profiles elevated concentrations of Se, As, Cd, and Ni in leachate possibly due to the dissolution of CaCO3 and release of metals adsorbed to CaCO3. Reduced Cu concentrations were possibly due to reduced DOC concentrations at reduced pH. On the other hand, acidification greatly reduced the amount of metals leached through the fresh ash‐soil profiles (except Ca and Cd), mainly due to significant reduction in the mobilization/solubilization of organic matter. The high metal mobility in the unacidified fresh ash‐soil profiles could have been due to DOC‐facilitated metal migration.