bluuebunny/crossref_metadata_2025_split huggingface dataset:
Denitrification in Cultivated and Noncultivated Riparian Areas of Grass Cropping Systems
Authors: Horwath William R. , Elliott Lloyd F. , Steiner Jeffrey J. , Davis Jennifer H. , Griffith S. M. 
Published: July 2010

AbstractThe factors that affect denitrification of fertilizer N were determined in cultivated riparian (CR) soils cropped to perennial ryegrass (Lolium perenne L.) and noncultivated naturally vegetated riparian soils (NCR) of poorly drained grass cropping systems in western Oregon. Denitrification activity in the NCR was low compared with the CR using the Acetylene Inhibition method. The CR soil denitrification activity was consistent over the growing season, averaging between 269 and 280 g N2O‐N ha−1 d−1 during the measurement period depending on soil type. Denitrification activity was positively correlated to soil NH4‐N level in the CR. The greater denitrification activity of the CR likely reflects fertilizer applications in contrast to no fertilizer addition to the NCR. Nitrate‐N levels in the CR averaged 5 to 12 times higher than those of the NCR. Nitrate did not appear to encroach from the CR into the NCR by subsurface water movement. The microbial biomass was four times larger in the NCR soils and may have functioned as a significant sink for N reducing denitrification activity. Multivariate factor analysis using orthogonal factor rotation showed that approximately 83% of the observed variance in denitrification was explained by grouping experimental variables by microbial activity, N2O‐N emission, temperature, and nitrification. The grouping of soil variables was useful in explaining the importance of different soil processes in regulating denitrification. These denitrification activity data demonstrate the possibility for significant N losses, amounting to 12.5% of the applied fertilizer N, from poorly drained cropping systems.
Chromate Extraction from Surfactant‐Modified Zeolite Surfaces
Authors: Li Zhaohui 
Published: July 2010

AbstractSurfactant‐modified zeolites (SMZ) as permeable barriers for remediation of chromate contaminated groundwater have shown great promises due to their low cost, excellent hydraulic conductivity, and instantaneous chromate sorpfion. However, the stability of chromate sorbed on SMZ surfaces need to be evaluated. In addition, effective extractants for chromate extraction may lead a way to regenerate the chromate‐saturated SMZ. In this research 10 different published methods were tested for chromate extraction. The sorbed chromate is relative resistant to most extractants, a prerequisite for SMZ to be used as permeable barriers. The methods using phosphate buffer and using hydroxide solution extracted <10% of the spiked and sorbed chromate. On the other hand, a carbonate‐hydroxide solution as the extractant removed 90 to 100% sorbed chromate. The maximum extraction of chromate by the carbonate‐hydroxide solution may indicate that it is the high concentration of carbonate that makes the substitution of sorbed chromate by carbonate possible, while the high pH resulting from NaOH addition ensures that the dominating anion species is CO2−3 instead of HCO−3.
Agricultural Phosphorus and Eutrophication: A Symposium Overview
Authors: Daniel T. C. , Sharpley A. N. , Lemunyon J. L. 
Published: July 2010

AbstractPhosphorus in runoff from agricultural land is an important component of nonpoint‐source pollution and can accelerate eutrophication of lakes and streams. Long‐term land application of P as fertilizer and animal wastes has resulted in elevated levels of soil P in many locations in the USA. Problems with soils high in P are often aggravated by the proximity of many of these areas to P‐sensitive water bodies, such as the Great Lakes, Chesapeake and Delaware Bays, Lake Okeechobee, and the Everglades. This paper provides a brief overview of the issues and options related to management of agricultural P that were discussed at a special symposium titled, “Agricultural Phosphorus and Eutrophication,” held at the November 1996 American Society of Agronomy annual meetings. Topics discussed at the symposium and reviewed here included the role of P in eutrophication; identification of P‐sensitive water bodies; P transport mechanisms; chemical forms and fate of P; identification of P source areas; modeling of P transport; water quality criteria; and management of soil and manure P, off‐farm P inputs, and P transport processes.
Cadmium Solubility and Phytoavailability in Sludge‐Treated Soil: Effects of Soil Organic Carbon
Authors: Hyun Hae‐nam , Chang A. C. , Parker D. R. , Page A. L. 
Published: July 2010

AbstractSlow mineralization of organic matter in sewage sludge‐treated soil could release metals into more labile forms, which would then be more available for plant absorption. We examined the effect of soil organic matter decomposition on the phytoavailability of Cd in soils which, prior to this experiment, received 0 (control), 22.5, 45, 90, 180 Mg ha−1 yr−1 of sewage sludge for 6 yr. At the commencement of the experiment, one‐half of the experimental plots continued to receive sewage sludge application`at the prescribed rates. Sewage sludge application in the other half of the plots was terminated. All treated soils were cropped to Swiss chard (Beta vulgaris) twice each year for 10 yr and the soil was sampled after each crop harvest. When sewage sludge applications were teenated, the soluble Cd concentrations of the sludge‐treated soil were higher than those in the control soils and did not decline significantly over the next 10 yr. With continuous sludge applications, the soluble Cd concentration of sludge‐treated soils increased with each incremental addition of sludge for the same 10 yr. In soils receiving continuous sewage sludge inputs, the organic C content continued to rise with sludge inputs. After the termination of sludge application, organic C content of the sludge‐treated soils decreased by approximately 40% over the 10‐yr study. There was no indication that the soluble Cd concentration or the phytoavailability of Cd in the sludge‐treated soils increased as the organic C in these soils declined over the 10 yr following termination of sewage sludge application.
Effect of Polyaromatic Hydrocarbons in Soil on Arbuscular Mycorrhizal Plants
Authors: Leyval C. , Binet P. 
Published: July 2010

AbstractThe rhizosphere of plants plays a role in the bioremediation of soils polluted with organic pollutants such as polyaromatic hydrocarbons (PAHs). Arbuscular mycorrhizal (AM) fungi provide a direct link between soil and plant roots, but very little is known of the interactions between PAHs and AM fungi. We studied the effect of PAHs on mycorrhizal colonization in polluted soil, and the effect of AM fungi on plant growth in these soils. Leek (Allium porrum L.), maize (Zea mays L.), ryegrass (Lolium perenne L.), and clover (Trifolium subterraneum L.) were grown in pots containing a soil artificially contaminated with increasing concentrations of anthracene or mixed with an industrial soil polluted with PAHs. Mycorrhizal colonization by the indigenous AM population of the nonpolluted soil was not significantly affected by the addition of anthracene up to 10 g kg−1. However, mycorrhizal colonization of clover and leek decreased when the industrial soil was added to the nonpolluted soil, while maize and ryegrass colonization was not affected. The effect of PAHs on plant survival and growth depended on plant species. Inoculation of ryegrass with Glomus mosseae improved plant survival and plant growth in the industrially polluted soil. At 5 g of PAH kg−1 only mycorrhizal plants survived. Mycorrhizal fungi may contribute to the establishment and maintenance of plants in PAH‐polluted soils.
Acceleration of 1,3‐Dichloropropene Degradation by Organic Amendments and Potential Application for Emissions Reduction
Authors: Gan J. , Yates S. R. , Crowley D. , Becker J. O. 
Published: July 2010

AbstractEmissions of the fumigant 1,3‐dichloropropene (1,3‐D) can result in degradation of air quality in certain areas. The high emission potential of 1,3‐D is caused by its rapid diffusion and comparatively slow degradation in soil. One approach to reduce the emission is to enhance the surface soil's capacity to degrade 1,3‐D. We investigated the capability of two organic amendments, a composted manure (CM) and a biosolid‐manure mix (BM), to accelerate 1,3‐D degradation in soil. Degradation of 1,3‐D was significantly enhanced in amended soils compared to the unamended soil, and the degree of acceleration varied with the type as well as the rate of amendment. Compost manure was more effective in stimulating 1,3‐D degradation than the less decomposed BM; even at an amendmen/soil ratio as low as 1:40 (w/w), degradation in the CM‐amended soil was two times faster than that in the unamended soil. The acceleration in CM‐amended soils was a combined result of enhanced chemical and microbial degradation, since sterilization only partially reduced the enhanced degradation. The reduction of 1,3‐D emissions by surface application of organic amendments was illustrated in a column experiment: 1,3‐D emission loss after injection at 30 cm was 30% from an unamended Arlington sandy loam (a coarse‐loamy, mixed, thermic Haplic Durixeralf), but decreased to only 16% in the column containing 5% CM in its top 5‐cm layer.
Effect of Application Methods on 1,3‐Dichloropropene Volatilization from Soil under Controlled Conditions
Authors: Gan J. , Yates S. R. , Wang D. , Ernst F. F. 
Published: July 2010

AbstractEmissions of fumigants can be an important source of air pollution at soil fumigation sites, and the high emission rates result partly from the use of application methods that are high in volatilization potential. In this study, we compared volatilization of fumigant 1,3‐dichloropropene (1,3‐D) fr.om a sandy loam in 60‐cm packed columns after applied by different methods. The most volatilization was found with injection into uncovered soil at a shallow depth (e.g., 56% loss for the 20‐cm injection) and application via surface drip irrigation (>90%). Volatilization fluxes and cumulative losses, however, rapidly decreased as the injection depth was increased, and the total loss was only 27% for the 40‐cm injection. The commonly used polyethylene plastic was ineffective in reducing the volatilization because of its high permeability to 1,3‐D. Water application after the 20‐cm injection resulted in substantially reduced volatilization, but the least loss (22%) was obtained when an emulsifiable formulation of 1,3‐D, Telone SL, was drip‐applied to the subsurface at 20 cm. Our results indicate that variables most influencing 1,3‐D volatilization are injection depth and water management. By optimizing these variables, application methods with low emission potential can be developed.
The Fate of Groundwater Ammonium in a Lake Edge Wetland
Authors: Lusby Fleur E. , Gibbs Max M. , Cooper A. Bryce , Thompson Keith 
Published: July 2010

AbstractThe removal of ammonium—nitrogen (NH4‐N) from groundwater flowing through a grey willow (Salix cinerea) and native raupo (Typha orientalis) lake edge wetland was investigated over 10 mo. Monthly groundwater sampling showed that more than 95% of incoming NH2‐N was removed by the wetland. Laboratory assays found that the potential for NH4‐N removal by nitrification and subsequent denitrification was significantly higher in the organic surface sediments than in deeper, sandy, root zone sediments. In a laboratory 15N‐tracer experiment, Salix cinerea and Typha orientalis readily assimilated NH2‐N from the root zone and were found to enhance the natural diffusion of NH4‐N up through the organic sediment layer and into the overlying water. Estimated rates of removal of NH2‐N by coupled nitrification‐denitrification and plant assimilation were 8 to 9 mg of N m−2 d−1 and 9 to 46 mg of N m−2 d−1, respectively. Assimilated N, returned to the overlying water‐sediment surface via litter fall may be subject to sequential mineralization, nitrification, and denitrification, resulting in gaseous N loss. Sixty‐five percent of the 15N in Salix leaf litter was transformed in such a way. The results of this study indicate that plants play a central role in the NH4‐N processing capacity of wetlands. The relevance of our findings to constructed wetland design is discussed.
Field Response of Soil Physical Properties to Sewage Sludge
Authors: Lindsay Billie J. , Logan Terry J. 
Published: July 2010

AbstractAn anaerobically digested sewage sludge was applied to a Miamian silt loam (fine, mixed, mesic Typic Hapludalfs) at rates of 0, 7.5, 15, 30, 60, 90, 120, 150, 188, 225, and 300 Mg/ha. Surface soils (0–15) cm were sampled 4 yr after sludge application and analyzed for bulk density, particle density, porosity, saturated hydraulic conductivity, moisture retention, aggregate stability, shrinkage, liquid and plastic limits, and total C. Bulk density significantly decreased, and porosity, moisture retention at 5.9 kPa, 33 kPa, and 1.5 MPa, percentage water stable aggregates, mean weight diameter of aggregates, and liquid and plastic limits increased with increasing sludge application. Sludge application had no significant effect on particle density, available water, saturated hydraulic conductivity, and shrinkage. Physical property responses to sludge application were linear except aggregate stability and mean weight diameter of aggregates that showed a maximum effect at 60 Mg/ha sludge application rate. Organic C increased linearly with sludge application, and 4 yr after application there was three times as much C in the 300 Mg/ha plots as in the zero sludge control plots. It is likely that many of the observed differences in soil physical properties are due to effects of added organic matter and these effects have persisted for at least 4 yr.
Transport and Persistence of Pesticides in Alluvial Soils: I. Simazine
Authors: Cogger C. G. , Bristow P. R. , Stark J. D. , Getzin L. W. , Montgomery M. 
Published: July 2010

AbstractPesticide leaching is a concern in the alluvial valleys of western Washington, where high‐value crops are grown in soils with water tables <m deep. We conducted this project to determine the long‐term leaching pattern of simazine [2‐chloro‐4,6‐bis‐(ethylamino)‐s‐triazine] applied to red raspberry (Rubus idaeus L.) and strawberry (Fragaria × ananassa Duch.). Simazine was applied to strawberry and raspberry in paired plots at two sites. Strawberry received a split application (total 2.2 kg ha−1) in August and November, and raspberry received a single 4.5 kg ha−1 application in November. We applied simazine yearly from 1986 to 1989, and sampled soil (to 180 cm) and shallow groundwater monthly until April 1991, and at one site again in 1994. Most of the simazine remained in the surface 15 cm of the soil or degraded, but small amounts moved downward. Preferential flow soon after application was not the main cause of downward movement. Simazine was persistent, with disappearance half lives of 128 and 175 d at the two sites the first year. Some simazine remained in the soil 4 yr after the final application. Simazine was most mobile beneath raspberry at one site. This site had finer texture and slightly more organic matter, but a lower Kd for simazine than the other site. Small amounts of simazine reached shallow groundwater beneath both crops. The observed simazine leaching peak was more asymmetric than the peak predicted by the PRZM‐2 model, an indication of nonequilibrium adsorption‐desorption effects on simazine movement.
Long‐Term RDX Sorption and Fate in Soil
Authors: Singh J. , Comfort S. D. , Hundal L. S. , Shea P. J. 
Published: July 2010

AbstractSoils at former munitions production facilities are often contaminated with hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). Contamination can be excessive and soils often contain precipitated or solid‐phase RDX, resulting in soil solution concentrations at or near saturation. Sorption and long‐term fate must be understood to predict RDX availability and develop remediation strategies. We characterized RDX sorption and availability in Sharpsburg (a fine, montmorillontic, mesic Typic Argiudoll) surface soil by equilibrating the soil with 32 mg RDX L−1 (spiked with 14C‐labeled RDX) for 168 d; similar experiments were performed with contaminated and uncontaminated subsurface soils. Surface soils exhibited rapid RDX sorption with 34% of the 14C sorbed within 30 min. This sorbed fraction increased to only 37% at 168 d. During the 168‐d equilibration, readily available RDX (sorbed RDX extractable with 3 mM CaCl2) decreased from 75 to 52%, while potentially available RDX (acetonitrile‐extractable) increased from 24 to 32%. Carbon‐14 in the 0.5 M NaOH‐extractable organic matter fraction increased from 0.8 (T = 30 min) to 3.8% (T = 168 d). Little 14C was removed after eight extractions with 10% KOH in ethanol. Eight percent of the 14C‐label was unextractable (bound) residue at 168 d; no 14C‐bound residue formed in surface soil when solid‐phase RDX was present in the equilibrating solution. Our experiments indicated limited RDX sorption and transformation in the Sharpsburg surface and subsurface soils. Most of the sorbed 14C was potentially available for transport, indicating the importance of remediating RDX‐contaminated soil to protect groundwater quality.
Effects of Heavy Metal Contamination and Remediation on Soil Microbial Communities in the Vicinity of a Zinc Smelter
Authors: Kelly John J. , Tate Robert L. 
Published: July 2010

AbstractHeavy metal contamination can impact soil ecosystems sufficiently to result in significant losses in soil quality. The negative impact of heavy metals results from their toxicity to biological processes, including processes catalyzed by soil microorganisms. Therefore, it is postulated that the soil microbial community could serve as an indicator of losses in soil quality due to heavy metal contamination and of changes in soil quality resulting from reclamation. In this study, the size, activity, and structure of microbial communities from remediated and unremediated soils in the vicinity of a Zn smelter were evaluated. Both total and soluble metal loadings in these soils increased with proximity to the smelter. Indicators of microbial activity (dehydrogenase activity) and viable population size (plate counts) were negatively affected by the elevated metal levels. Microbial community structure also varied with increasing contamination, as indicated by cluster analysis and principal component analysis of BIOLOG community metabolic profiles. Remediated soils at this site were treated by surface application of a mixture of sewage sludge and fly ash. Remediation resulted in a decrease in soluble metals and an increase in indicators of biological activity and viable population size. Remediated soils also showed metabolic profiles that were more similar to the least contaminated site, suggesting recovery of the microbial populations. These data suggest that the microbial community may be a useful indicator of changes in soil quality with management of these highly contaminated soils.
Salinity Trends in Surface Waters of the Upper Colorado River Basin, Colorado
Authors: Bauch Nancy J. , Spahr Norman E. 
Published: July 2010

AbstractDissolved‐solids data collected in the Upper Colorado River Basin upstream from Cameo, Colorado, and in the Gunnison River Basin were analyzed for trends in flow‐adjusted dissolved‐solids concentrations and loads for water years 1970 to 1993, 1980 to 1993, and 1986 to 1993. Trend results for flow‐adjusted periodic dissolved‐solids concentrations for the Colorado River Basin upstream from Cameo, CO, generally were downward or no trend was indicated. Trends in flow‐adjusted monthly and annual dissolved‐solids loads primarily were downward or absent. These trend results partly agree with the downward trends reported by a previous investigation for the Colorado River near Cameo site. In the Gunnison River Basin, trends in flow‐adjusted dissolved‐solids concentrations and loads were not detected for more than one‐half of the site/analysis‐period combinations. Of the trends that were present, most indicated decreases in concentrations and loads rather than increases. In both the Colorado River Basin upstream from Cameo, CO, and the Gunnison River Basin, trends in flow‐adjusted dissolved‐solids concentrations and flow‐adjusted monthly and annual dissolved‐solids loads may be affected by a variety of factors. These include channel evolution and hydrologic variation, water quality and flow rate of groundwater discharges and springs, sample size and period of record of dissolved‐solids data, and changes in land use in the basin.
Decreasing Nitrogen Leaching from Sandy Soil with Ammonium‐Loaded Clinoptilolite
Authors: Perrin T. S. , Boettinger J. L. , Drost D. T. , Norton J. M. 
Published: July 2010

AbstractNitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO−3) levels in surface and groundwaters. In this study, as a preface to a plant growth study, we compared N leaching from NH+4‐loaded clinoptilolite (A‐Cp) and (NH4)2SO4 (AS) in two media: a rounded quartz sand and a sandy soil. We hypothesized that quartz sand or soil amended with A‐Cp would leach significantly less N than these media amended with AS, and that more N would leach from smaller A‐Cp size fractions than from larger A‐Cp size fractions. Ammonium sulfate, or one of the three A‐Cp size fractions, small (<0.25 mm), medium (0.25–2 mm), or large (2–4 mm), was banded at a depth of 5 cm in leaching columns filled with inert quartz sand at a rate of 112, 224, or 336 kg N ha−1. The experiment was repeated with sandy soil in greenhouse pots at rates of 112 and 224 kg N ha−1. The columns and pots were leached for about 40 d with a simulated irrigation water. Significantly more N, as NH+4 and NO−3, leached from AS amendments than any of the A‐Cp amendments in both experiments. Results indicated that the larger the A‐Cp size fraction, the slower NH+4 is released from A‐Cp. Ammonium‐Cp slowly releases N and could significantly minimize N leaching from sandy soils compared to AS.
Field Evaluation of Calcium Sulfate as a Chemical Flocculant for Sedimentation Basins
Authors: Przepiora A. , Hesterberg D. , Parsons J. E. , Gilliam J. W. , Cassel D. K. , Faircloth W. 
Published: July 2010

AbstractSedimentation basins are built at construction sites to reduce the load of suspended solids in runoff water discharged into surface waters. However, these basins are not effective in reducing turbidity caused by fine suspended particles such as clay and silt. The objective of this field study was to evaluate the efficiency of moulding plaster (CaSO4 · 0.5 H2O) as a chemical flocculant for reducing the turbidity of water discharged from sedimentation basins equipped with a floating skimmer device. Following each of 14 rainfall events, sedimentation basins at two urban construction sites were either treated with moulding plaster or left untreated, and the turbidity and chemical properties of the impounded water and discharge water were monitored as the basins drained during a 50‐ to 70‐h time period. Each sedimentation basin was equipped with a floating skimmer device that discharged water at a controlled rate from 5‐cm below the surface of the impounded water. The turbidity of discharge water from untreated basins ranged from 100 to 1650 NTU (nephelometric turbidity units), while a surface‐applied moulding plaster treatment of 450 to 520 mg L−1 decreased the turbidity to <50 NTU. The time required for the discharge water from treated basins to reach either 100 NTU (2–20 h) or 50 NTU (5–52 h) was inversely proportional to the concentration of dissolved moulding plaster. Chemical flocculation using moulding plaster reduced the turbidity of discharge water to <50 NTU while producing dissolved SO4 concentrations of <250 mg L−1.