bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cation Exchange Behavior of Bauxite Refining Residues from Western Australia
Authors: Wong J. W. C. , Ho G. E. 
Published: July 2010

AbstractOver 60 million tonnes per year of bauxite refining residue (red mud) is produced worldwide. Its high Na concentration inhibits plant growth and hence reclamation. The cation‐exchange capacity (CEC) of red mud and the cation exchange equilibria between Na+ and several other cations were measured to elucidate the mechanism of Na release from red mud. The CECs obtained by using K+ and NH+4 were significantly higher than those obtained using Ca2+ and Ba2+. This unusual cation exchange phenomenon can be attributed to the presence of zeolitic minerals in red mud. Cation exchange equilibria show that Na+ originally present in red mud was preferentially adsorbed by the mud over other cations. At high cation fractions in red mud (>0.1), the mud selectively sorbed monovalent over divalent cations, with the following order of selectivity: K+ > Li+ > NH+4 > Ba2+ ≥ Ca2+ > Mg2+. The exchange of Na+ has been found to have significant negative correlations with the radius of hydration and Debye‐Huckei parameter. Divalent cations have little ability to exchange Na+ from zeolitic exchange sites. Incremental extraction of Na+ in red mud shows that K+ and NH+4 displaced 99 (63%) and 57 (44%) cmolc kg−1 red mud whereas Ca2+ and Mg2+ could only displace 33 and 29 cmolc kg−1 red mud, respectively, out of a total of 99 cmolc Na kg−1 red mud. In a reverse process 95% of K+ adsorbed on red mud was readily replaced by Na+. The experimental evidence suggests that the release of Na+ from red mud is due to cation exchange.
Agricultural Water Quality Program Policy Considerations
Authors: Harris B. L. , Nipp T. L. , Waggoner D. K. , Weber A. 
Published: July 2010

AbstractCongress, in dealing with the Coastal Zone Management Act and Amendments, and the Clean Water Act reauthorization, has placed increased attention on agricultural point and nonpoint‐source pollution. A structure (“tiered and targeted”) for integrating voluntary, incentive‐based, and regulatory approaches to address agricultural point and nonpoint‐source pollution is proposed, in keeping with the administration's commitment to use voluntary programs to the extent possible, but applying regulatory programs where necessary. The focus of this article is on agricultural sources of nonpoint‐source pollution and the appropriate mix of federal, state, and local programs for necessary control actions. Specific suggestions are offered for improving existing programs and appropriate roles are suggested for land‐grant universities in responding to pollution demands.
Nonlinear Regression of Breakthrough Curves to Obtain Retardation Factors in a Natural Gradient Field Study
Authors: Widmer S. K. , Spalding R. F. , Skopp J. 
Published: July 2010

AbstractAn investigation of the fate and transport of trace quantities of commonly detected herbicides and herbicide degradates in groundwater under aquifer conditions was conducted in a shallow sand and gravel aquifer. Herbicides and a conservative tracer (bromide) were injected into the aquifer and the plumes monitored for 2 to 3 mo using an array of downgradient multilevel samplers (MLSs). Breakthrough curves were fitted to the advection‐dispersion and exponentially modified Guassian (EMG) equations. Coefficients of determination were high for both models (generally >0.90). Comparison of the breakthrough curves for the conservative tracer and each herbicide provides a measure of retardation in the aquifer. A retardation factor (R) may be calculated from the first central moment of the data or from peak parameters obtained from the fitted curves, such as: (i) the time required to reach half‐maximum concentration, (ii) the centroid of the curve, or (iii) model parameters such as the apparent transport velocity. Comparison of the retardation factors shows small differences due to the method of calculation both within and between models. The similarities in the retardation factors and the fitted curves suggest that both the EMG and the advection‐dispersion model describe the data well. The detection of differences in herbicide retardation factors varied with the method of calculating R.
Ingested Soil: Bioavailability of Sorbed Lead, Cadmium, Cesium, Iodine, and Mercury
Authors: Sheppard S. C. , Evenden W. G. , Schwartz W. J. 
Published: July 2010

AbstractIngestion of soil, inadvertent or otherwise, is an important route of exposure for contaminants that are not geochemically or biologically mobile. There is little known about the bioavailability of these contaminants, especially when the contaminants are sorbed onto native soil particles. We investigated this with in vitro acid‐extraction and enzymolysis experiments and with in vivo single and chronic exposure studies with mice (Mus musculus). The only anion studied was 125I, and soil in the diet had no effect on the carcass 125I content. The bioavailability of the cations tested decreased in the order of 134Cs > 203Hg > 115Cd = 210Pb, and the effect of soil in the diet on concentrations in the carcass decreased in the same order. Soil in the diet significantly decreased the bioavallability of 134Cs, by more than four‐fold, whereas the effect on 210Pb was only ≈1.1‐fold and was not significant. The results of the in vitro digestions ordered the elements in the same way as observed in the in vivo analyses. These results indicate that for contaminants that are not very mobile and are sorbed onto native soil particles, the presence of soil in the diet does not markedly affect bioavailability in the gut.
Spatial Analysis of Plutonium‐239 + 240 and Americium‐241 in Soils around Rocky Flats, Colorado
Authors: Litaor M. Iggy 
Published: July 2010

AbstractPlutonium and americium contamination of soils around Rocky Flats, Colorado resulted from past outdoor storage practices. Four previous studies produced four different Pu isopleth maps. Spatial estimation techniques were not used in the construction of these maps and were also based on an extremely small number of soil samples. The purpose of this study was to elucidate the magnitude of Pu‐239 + 240 and Am‐241 dispersion in the soil environment east of Rocky Flats using robust spatial estimation techniques. Soils were sampled from 118 plots of 1.01 and 4.05 ha by compositing 25 evenly spaced samples in each plot from the top 0.64 cm. Plutonium‐239 + 240 activity ranged from 1.85 to 53 560 Bq/kg with a mean of 1924 Bq/kg and a standard deviation of 6327 Bq/kg. Americium‐241 activity ranged from 0.18 to 9990 Bq/kg with a mean of 321 Bq/kg and a standard deviation of 1143 Bq/kg. Geostatistical techniques were used to model the spatial dependency and construct isopleth maps showing Pu‐239 + 240 and Am‐241 distribution. The isopleth configuration was consistent with the hypothesis that the dominant dispersal mechanism of Pu‐239 + 240 was wind dispersion from west to east. The Pu‐239 + 240 isopleth map proposed by this study differed significantly in the direction and distance of dispersal from the previously published maps. This isopleth map as well as the Am‐241 map should be used as the primary data for future risk assessment associated with public exposure to Pu‐239 + 240 and Am‐241.
Soil Matrix and Macropore Biodegradation of 2,4‐D
Authors: Pivetz B. E. , Steenhuis T. S. 
Published: July 2010

AbstractPreferential flow of pesticides in macropores can lead to decreased travel times through the vadose zone and increased groundwater contamination. Macropores, however, may present a favorable environment for biodegradation because of greater oxygen, nutrient, and substrate supply, and higher microbial populations in earthworm burrows, compared to the soil matrix. The biodegradation of 2,4‐dichlorophenoxyacetic acid (2,4‐D) was measured in macropores and soil matrix of packed soil columns (7.0‐cm diam., 10‐cm length) and undisturbed soil cores (10‐cm diam., 7.3 or 8.0‐cm length). Each packed column contained a well‐defined artificial macropore and the undisturbed cores contained earthworm‐burrow macropores. A 50 µg/L 2,4‐D solution was continuously applied to the unsaturated soil surface and breakthrough curves (BTCs) indicating pesticide loss in the effluent were obtained from the soil matrix and macropore flow paths. Biodegradation rates were calculated separately for each flow path by comparing the BTCs to BTCs representing abiotic conditions, and dividing the 2,4‐D loss by the travel time through each flow path. The biodegradation rates increased with time in both flow paths, and the final biodegradation rate in the macropore region surpassed that of the matrix, presumably because of increased microbial populations in the macropore. Complete loss of the 2,4‐D in both flow paths was observed after continuous application of 2,4‐D for 400 h, with maximum column‐averaged 2,4‐D loss rates of 0.879 µg/(L h) in the matrix and 1.073 µg/(L h) in the macropore. Biodegradation of 2,4‐D was also observed in the macropore and matrix regions of the undisturbed soil cores.
In Situ Respirometry: Field Methods and Implications for Hydrocarbon Biodegradation in Subsurface Soils
Authors: Hickey W. J. 
Published: July 2010

AbstractUsing soil ventilation to promote in situ biodegradation is a promising technology for remediation of unsaturated, hydrocarbon‐contaminated, subsurface soils. Evaluating in situ hydrocarbon biodegradation rates and levels is a critical part of this approach and determining changes in subsurface O2 and/or CO2 levels is a convenient method for monitoring this process because repetitive, noninvasive measurements can be made. In this study, two rapid field procedures for gas analysis, using either liquid‐ or solid‐phase absorption of O2 and CO2, were compared and the implications of these gas measurements for evaluating in situ hydrocarbon biodegradation considered. Air samples were taken from 5 vadose zone piezometers in a gasoline‐contaminated soil under treatment by a soil vapor extraction system and one piezometer in a noncontaminated background area. Similar rates and levels of O2 consumption and CO2 production were obtained by both techniques during the 20‐d study; thus, the method of choice will depend on factors such as cost, air sample volume limitations, or the need for contaminant vapor analyses in the field. While these techniques were good assays for relative microbial activity levels, significant discrepancies between predicted and measured CO2 levels raised questions concerning the validity of basing hydrocarbon biodegradation estimates solely on O2 consumption data. To improve the reliability of in situ fuel biodegradation estimates based on O2 measurements, the relationship(s) between metabolic activities of microbial populations in hydrocarbon‐contaminated soils, and changes in subsurface O2 and CO2 levels should be clarified.
Distribution and Persistence of Azinphos‐Methyl and Parathion in Chemigated Cranberry Bogs
Authors: Wan Michael T. , Szeto Sunny Y. , Price Patricia 
Published: July 2010

AbstractDitches draining two cranberry (Vaccinium spp.) bogs flowing into salmon (Oncorhynchus spp.) bearing waterbodies in the Lower Fraser Valley of British Columbia, Canada, were sampled in 1992 to determine the distribution and persistence of azinphos‐methyl (AZI) and parathion (PAR) following three treatments through an irrigation system (chemigation), to control the black‐headed fireworm (Rhopobota naevana Hbn). One bog was surrounded by a secured dike system for water retention and the other by a leaking dike system, representing a worst‐case scenario. After each treatment, AZI and PAR residues were detected in ditch water (detection limit = 0.05 µg/L) and sediments (detection limit = 5 µg/kg) inside and outside the bogs and they persisted for 72 and 32 d, respectively. The highest concentrations in water were 175 µg/L for AZI and 21 µg/L for PAR. Concentrations of AZI and PAR in sediments ranged from not detected to 1582 µg/kg and persisted for 210 and 13 d, respectively. Low levels of aerial drift resulting from the treatment were detected beyond the outer perimeter of the sprinkler irrigation system in the cranberry bogs. Off‐site release of insecticide residues occurred in the leaking dike system but not in the secured dike system. The released insecticide residues adversely affected nontarget aquatic organisms. Harvested cranberries contained no detectable (detection limit = 5 µg/kg) residues of AZI and PAR.
Biosolids Effect on Phosphorus, Copper, Zinc, Nickel, and Molybdenum Concentrations in Dryland Wheat
Authors: Barbarick K. A. , Ippolito J. A. , Westfall D. G. 
Published: July 2010

AbstractWhen biosolids that are low in trace elements are applied on cropland, the tissue concentrations of trace elements may approach a concentration plateau as cumulative quantity of the element added increases. If the plateau concentration is less than that of safe threshold, the application may continue indefinitely. We found that wheat (Triticum aestivum L. ‘Vona’ or ‘TAM107’) grain concentrations of P, Cu, Zn, and Ni from an 11‐yr field study of biosolids land application follow a plateau model. The grain concentrations of P, Cu, and Zn approach the calculated plateau maximum after 11 applications (in fallow rotation, we completed six applications to one set of plots plus five applications to a second set). Grain Ni levels show a linear response to cumulative inputs of biosolids Ni. Possibly, the biosolids are providing a labile source of Ni. The Mo concentrations did not change significantly as cumulative inputs of biosolids Mo increased. Our results indicate that plateau modeling can describe the changes in wheat grain concentrations associated with biosolids application.
Tree Survival and Growth on Land Reclaimed in Accord with Public Law 95‐87
Authors: Chaney William R. , Pope Phillip E. , Byrnes William R. 
Published: July 2010

AbstractThe objective of this study was to determine survival and growth of black walnut (Juglans nigra L.) and northern red oak (Quercus alba L.) 12 yr after planting on a surface‐mined site in southern Indiana reclaimed according to specifications of Public Law 95‐87, the Surface Mining Control and Reclamation Act of 1977. A stocking level adequate to meet the requirements for forest land use (1112 trees/ha, or 450 trees/acre) was attained only for black walnut and only if competing ground cover vegetation was controlled in the tree rows. Height of both tree species was significantly greater when ground cover vegetation was controlled during the first 2 yr, but the growth rate, approximately 10 cm/yr, was very slow.
Spatial and Temporal Variation in Groundwater Nitrate Removal in a Riparian Forest
Authors: Nelson William M. , Gold Arthur J. , Groffman Peter M. 
Published: July 2010

AbstractWe quantified nitrate (NO−3) removal rates from groundwater in a red maple (Acer rubrum L.) riparian forest subjected to NO−3 dosing. The site was in Southern New England on soils classified as sandy mixed mesic Haplaquept soils and contained somewhat poorly (SPD) and poorly drained (PD) soils. The specific objectives were to examine groundwater NO−3 removal rates within a riparian forest with respect to: (i) soil drainage class; (ii) depth below water table; and (iii) time of year. We created 16 experimental dosing/monitoring stations at two depths along three soil drainage class transects (SPD, SPD/PD, PD). We added solution containing NO−3 and Br− continuously for 11 mo to a dosing well at each station. Groundwater was monitored at sampling wells 0.6 m downgradient of the dosing well. Nitrate removal rates were determined by coupling changes in the NO−3/Br− ratio with groundwater flux estimates from each experimental station. Although located just 20 m downgradient, the PD transects had substantially higher NO−3 removal rates and lower dissolved oxygen than the SPD transects. Both the SPD/PD and PD transects had considerable NO−3‐N removal capacity throughout the upper 1.5 m of the groundwater (16–46 µg kg−1 d−1). Rates were not significantly influenced by temperature. The scale of variation in removal rates suggests that high resolution soil and groundwater maps may be needed when riparian forests are to be used for water quality management.
The Effect of Moisture and Soil Texture on the Adsorption of Organic Vapors
Authors: Petersen L. W. , Moldrup P. , El‐Farhan Y. H. , Jacobsen O. H. , Yamaguchi T. , Rolston D. E. 
Published: July 2010

AbstractThe fate of volatile organic compounds (VOCs) moving as vapors in the subsurface is dependent on their interaction with the soil. Adsorption of VOC vapors is greatly influenced by soil texture and soil‐water content. The effects of differences in texture and soil‐water content on vapor partition coefficients for trichloroethylene (TCE) were examined. Batch experiments were conducted for a variety of soils and at different soil‐water contents, w, to determine the relationship between the vapor/solid partition coefficient, KD′, and w. In dry soils, KD′ was nonlinearly related to soil‐water content because, in that range, water molecules compete with VOC molecules for adsorption sites on the soil surface. Under wet conditions, KD′ became linearly related to water content according to Henry's law, indicating that adsorbed water molecules were acting as a solvent for VOC molecules. In general, KD′ under oven‐dry conditions did not relate well to total specific surface area of soils, most likely because VOC molecules adsorb only on the outside surfaces of soil particles (due to their nonpolarity), rather than the total surface area present. In the dry range, adsorption was dominated by soils with high specific areas (i.e., high clay content), while soils with higher organic carbon content manifested higher adsorption amounts in the wet moisture range. A one‐parameter, exponential model well described the log KD′‐w curve in the nonlinear region. The model parameter, a, was found to be highly dependent on the specific surface area of the soil. The proposed KD′‐(w) model incorporated in conventional VOC transport models seems promising for analyzing the effects of VOC vapor adsorption on VOC subsurface transport.
Plant Selenium from Soil and the Atmosphere
Authors: Haygarth Philip M. , Harrison Anthony F. , Jones Kevin C. 
Published: July 2010

AbstractTransfer of selenium (Se) to pasture is important for prevention of Se deficiency in livestock, yet little is known about the relative importance of inputs to pasture from soil and the atmosphere. An isotope dilution method was used to assess quantitatively the importance of these inputs to ryegrass. Soil was labelled with 75Se and subjected to two field treatments that were untreated (pH 6.0) and limed (pH 7.0). After an initial period of equilibration, the specific activity of Se associated with unwashed leaves became lower than that of soil. This indicated that atmospheric Se had been deposited onto and possibly incorporated into the ryegrass. The percent contribution of 75Se in pasture leaves derived from the soil was 47% (pH 6.0) and 70% (pH 7.0), with, by inference, the remainder coming from the atmosphere.
Linking a Geographic Information System with a Potato Simulation Model for Site‐Specific Crop Management
Authors: Han S. , Evans R. G. , Hodges T. , Rawlins S. L. 
Published: July 2010

AbstractSite‐specific crop management (SSCM) requires that crop simulation models be applied to subareas of a field to test or develop management practices. When the number of subareas is sufficiently large, crop simulation models should be linked with a geographic information system (GIS) for ease of input data preparation and for output data analysis. An interface between PC ARC/INFO (a GIS) and SIMPO‐TATO (a potato growth simulator) was developed to study potato (Solanum tuberosum L.) yield and N leaching distributions. The most important distributed input parameters were identified as the irrigated water/N, soil texture, and initial soil N. An example usage of the interface program is given to study the N leaching under different management scenarios.
Denitrification in a Restored Riparian Forest Wetland
Authors: Lowrance Richard , Vellidis George , Hubbard Robert K. 
Published: July 2010

AbstractGroundwater nitrate moving from upland areas toward streams can be removed by denitrification in mature riparian forests, but denitrification in restored riparian forests has not been quantified. We determined denitrification rates in a restored riparian wetland below a liquid manure application site. A riparian forest buffer consisting of hardwoods along the stream and pines above the hardwoods was established according to USDA specifications. Denitrification was measured monthly using the acetylene inhibition technique on intact soil cores for 2 mo before manure application began and for 24 mo after manure application. Groundwater movement of NO3−‐N and total Kjeldahl N were estimated biweekly. Average annual denitrification rate was 68 kg N2O‐N ha−1 yr−1. Denitrification was significantly higher in a grassed area than in either of the forested areas. Denitrification did not differ significantly between the hardwood and pine areas. Denitrification was greater than a conservative estimate of groundwater input of total N. Denitrification rates were higher in April and May 1992 and 1993, after manure application to the upland began, compared with April and May 1991, before manure application began. These results indicate that a riparian wetland, which has not undergone hydrologic modifications, can have denitrification rates comparable to mature riparian forests. Higher denitrification rates in an adjacent grassed wetland and lack of differences in denitrification in hardwood and pine zones indicates that the high denitrification rates were due to factors other than the reforestation itself. Compared with groundwater inputs of N, denitrification was an important sink for N moving from the upland management system.
The Effects of pH, Flow Rate, and Carbon Supplementation on Manganese Retention in Mesocosm Wetlands
Authors: Stark Lloyd R. , Wenerick William R. , Williams Frederick M. , Wuest Paul J. 
Published: July 2010

AbstractIn an effort to obtain design parameters, a wetland mesocosm experiment was conducted to determine the effects on Mn retention of flow rate, inlet pH, and C supplementation. Sustained Mn retention was not achieved under reducing conditions when spent mushroom substrate was used as a substrate irrespective of flow rate, inlet pH, and C supplementation regimes. However, a lowered flow rate resulted in many significant effects on outlet water chemistry, including lower outlet Mn concentrations, higher outlet pH, lower outlet acidity, higher outlet alkalinity, higher outlet sulfide, lower outlet sulfate, and lower outlet redox potential. Supplementation of the wetlands with dairy whey resulted in marginally lower outlet Mn concentrations and marginally higher outlet sulfide levels. Wetlands receiving a neutral pH had lower outlet acidity, higher outlet alkalinity, lower outlet sulfate, but equivalent outlet Mn concentrations to wetlands receiving an acidic pH. Sulfate reduction was stimulated by reducing flow rates and metal loads. Metal extractions indicated that most of the Mn was retained as exchangeable Mn (37%), carbonate‐bound Mn (30%), and oxide‐bound Mn (21%), with most (64%) of the Mn retained at the surface of the wetland. The dominant form of Mn found in the subsurface substrate samples was exchangeable Mn (44%), indicating that stable forms of Mn did not form under reducing conditions.