bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mobility of Agrochemicals through Soil from Two Tillage Systems
Authors: Levanon D. , Codling E. E. , Meisinger J. J. , Starr J. L. 
Published: July 2010

AbstractThe fate of agrochemicais is often greatly affected by the surface‐soil conditions in the field. This study was conducted to characterize the impact of two contrasting tillage systems on the movement of agrochemicals in soil. The two tillage systems were plow‐tillage (PT) and no‐tillage (NT) for corn (Zea mays L.) production. The study included incubation and leaching of undisturbed soil columns and disturbed soil samples from 16‐yr plots subject to the two tillage regimes. The agrochemicals used in the study were NH4NO3, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine‐2,4 diamine), carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate), diazinon (0,0‐ diethyl‐O‐(6‐methyl‐ 2(1‐methethyl)‐4‐pryamidinyl phosphor‐ othioate), and metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐metoxy‐1‐methylethyl) acetamide). The results of this study show greater ponded flow movement of all agrochemicais in soils under PT vs. NT conditions. Strong evidence was found for preferential flow through the soil, with the chemicals by‐passing much of the soil‐matrix under recently plowed soils as well as NT soils. Nitrate leaching was significantly greater under PT than NT, apparently due to greater mineralizing activity of the PT soil compared with the NT soil. The pesticide movement also tended to be greater under PT than NT. Caution should be exercised in generalizing to field conditions, but these data suggest that there can be greater leaching losses of surface‐applied agrochemicals to groundwater under PT than under NT.
A Zero‐Tension Sampler for the Collection of Soil Water in Macropore Systems
Authors: Simmons K. E. , Baker D. E. 
Published: July 2010

AbstractA zero‐tension sampler was designed for the collection of soil leachate at 1.2 m in the soil profile to determine the effects of dairy manure and NH3NO3 applications on water quality in soils possessing a macropore structure. Nitrate‐N concentrations in soil water collected from these samplers were compared with concentrations in soil water collected from conventional ceramic porous‐cup samplers. The zero‐tension samplers were constructed from 5‐cm polyvinyl chloride (PVC) pipe and installed at a 45° angle in the soil profile. This design minimized the amount of field excavation and the interruption of routine cultivation. On average, approximately 50% of the samplers contained solution after rainfall and the data were effective at demonstrating the effect of macropore flow on NO3‐N concentrations in the leachate. Nitrate‐N concentrations in soil water collected from porous‐cup samplers were consistently higher than those collected from zero‐tension samplers. Mean NO3‐N concentrations in soil water from porous‐cup and zero‐tension samplers ranged from approximately 5 to 60 mg L−1 and 0 to 20 mg L−1, respectively.
Sensitivity of Critical Load Estimates for Surface Waters to Model Selection and Regionalization Schemes
Authors: Holdren George R. , Strickland Timothy C. , Shaffer Paul W. , Ryan Patrick F. , Ringold Paul L. , Turner Robert S. 
Published: July 2010

AbstractA critical load is the amount of atmospheric pollutant that can be deposited on a sensitive ecosystem without causing measurable, longterm degradation in ecosystem form or function. We compare several methods for making critical load estimates of SO4 deposition to lakes; these methods are among those identified by participants in the United Nations‐Economic Commission for Europe (UNECE) Convention on Long‐Range Transboundary Air Pollution. The models were originally developed to address surface water acidification issues. Critical loads are computed here as the levels of deposition required to reduce surface water acid neutralizing capacities (ANC) from present values to either 25 µeq L−1 or 0 µeq L−1. These end points were selected to provide a common basis for comparing critical load values obtained from the various models, and are not intended to provide definitive critical load estimates. Using the amount of deposition required to decrease steady‐state surface water ANC values from 25 to 0 µeq L−1, about 9 ± 2 kgSO4 ha−1 yr−1 in the northeastern USA as a basis for comparison, we find that models make significantly different projections regarding ecosystem sensitivites to deposition. For lakes with critical load values in the range of current deposition in the Northeast (i.e., 18–56 kg SO4 ha−1 yr−1), model results differ by as much as 82 kg SO4 ha−1 yr−1. Differences in results are observed not only between models, but within models when slightly different approaches are used for estimating certain parameters. The interpretation of model results depends strongly on how systems are grouped regionally. While the results suggest that reductions in deposition from current levels would reduce adverse effects in sensitive lakes, the magnitude and timing of the reductions necessary and the determination of appropriate population end points are decisions that will ultimately be made by risk managers rather than risk assessors.
Characterization of Wind Erosion Sediments in the Red River Valley of North Dakota
Authors: Cihacek L.J. , Sweeney M.D. , Deibert E.J. 
Published: July 2010

AbstractWind erosion is a serious problem in the Red River Valley of North Dakota. Wind erosion sediments were characterized to evaluate their potential as nonpoint source pollutants for surface water and shallow groundwater. Thirty‐four sites from the South Dakota border to the Canadian border were sampled to measure physical and chemical characteristics of displaced sediment and field soils. Collected sediments originated from fields with soils having silt loam, silty clay loam or silty clay textures. Sediments had >98% water‐stable aggregates and average NO−3‐N levels of 105 mg kg−1. Calcareous sediments (22 samples) were significantly higher in pH, NO−3‐N and electrical conductivity (EC), while noncalcareous sediments (12 samples) were higher in P and K. Soils from sugar beet (Beta vulgaris L.) and small grain fields tended to have higher NO−3‐N levels than fields with other crops or cropping practices. Agricultural chemical residues were detected and identified at two sample sites. A comparison of displaced sediments with field soils showed significant increases in NO−3‐N, P, K and EC in the sediments and a significant reduction in pH. Nearly 96% of the NO−3‐N could be leached out of the sediments in an initial leaching. Wind erosion sediments have the potential to be nonpoint sources of NO−3‐N and salinity for surface and groundwater.
Binding Mechanism of 2,4‐Dichlorophenoxyacetic Acid by Organo‐Clays
Authors: Hermosin M. C. , Cornejo J. 
Published: July 2010

AbstractThe interaction of the herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D) with decylammonium‐montmorillonite (C10M) and decylammonium‐vermiculite (C10V) was studied by measuring 2,4‐D adsorption at different pH levels, and by preparing herbicide‐organic clay complexes which were characterized by x‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT‐IR). The adsorption of 2,4‐D at different pH values indicated that the undissociated form was preferentially adsorbed on C10M, whereas the anionic form was adsorbed by C10V. The adsorption of 2,4‐D was much greater for C10V than for C10M. X‐ray diffraction diffractograms and FT‐IR spectra of C10M did not show any changes after exposure to 2,4‐D, indicating adsorption on external surfaces by weak lyopbilic, aromatic ring‐alkylchain(tail), bond. The d001 values of the two C10V samples expanded after 2,4‐D exposure from 2.1 to 2.9 nm and from 2.4 to 3.3 nm, indicating interlayer adsorption of the herbicide. The FT‐IR spectrum of herbicide‐C10V complex showed the presence of a small amount of the molecular form of 2,4‐D weakly adsorbed on external surfaces by lyophilic (ring‐tail) bonding, but most of the herbicide molecules were adsorbed at the interlayer spaces by hydrogen bonds between carbonyl group (vc=0 at 1634 cm−1) of 2,4‐D and ammonium group of the interlayer organic cations. Some 2,4‐D molecules in C10V complex appeared to be dissociated as suggested by two bands at 1590 and 1330 cm−1, which corresponded to the unsymmetrical and symmetrical vibrations, respectively, of the COO− groups.
Starch‐Encapsulated Atrazine: Efficacy and Transport
Authors: Schreiber M. M. , Hickman M. V. , Vail G. D. 
Published: July 2010

AbstractCurrent data indicate that pesticides are a contributor to the groundwater contamination problem, with the herbicide atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] one of the most commonly found contaminates. Reports indicate that the highest levels of atrazine found appear to be associated with the heavy spring rains following application of presently used commercial formulations (CF) of atrazine. This work reports the role of new starch encapsulated (SE) granular formulations of atrazine that significantly reduce the initial mobility of atrazine without appreciable loss of weed control efficacy. Leaching studies in the laboratory indicate that SE formulations reduced movement of atrazine by 70% compared to CF in both silty clay loam and sandy soils following a 75 mm h−1 simulated rainfall. Results from leaching of intact soil blocks with simulated rainfall of 40 mm h−1 for 2 h showed CF leached 80 and 60% more atrazine than the SE formulation from chisel and no‐till systems, respectively. Granular size of SE formulations can affect the rate of release. Starch‐encapsulated formulations gave good to excellent control of most weeds at 10 sites in six Midwest states during the 1990 and 1991 growing seasons and resulted in corn (Zea mays L.) yields equal to or better than with CF. Control of some large seeded weeds such as velvetleaf (Abutilon theophrasti Medic.) and cocklebur (Xanthium strumarium L.) was variable from site to site with both SE and CF. Starch‐encapsulated formulations offer an excellent potential technology advancement for significant reduction of atrazine and other pesticide contaminates of groundwater with minimal loss of efficacy.
Pesticides in Shallow Groundwater in the Delmarva Peninsula
Authors: Koterba M. T. , Banks W. S. L. , Shedlock R. J. 
Published: July 2010

AbstractA regional study of the areal and depth distribution of pesticides in shallow groundwater in the Delmarva Peninsula of Delaware, Maryland, and Virginia was done to (i) relate the pesticides detected to landscape and shallow subsurface features, and (ii) evaluate aquifer vulnerability and the potential contamination of drinking‐water supplies. Water samples collected at 100 wells from 1988 to 1990 were analyzed for concentrations of 36 pesticides, four metabolites, and other constituents. The most commonly detected residues were atrazine, cyanazine, simazine, alachlor, metolachlor, and dicamba. Concentrations were low; few exceeded 3 µg L−1. Most detections correlate with the intensive use of these herbicides in three widely distributed and commonly rotated crops—corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and small grain—particularly if grown in well‐drained soils. Most detections occurred in samples collected from shallow wells screened within 10 m of the overlying water table. The shallow depth distribution of most residues is consistent with their suspected history of use (ca. 20 yr), and patterns in shallow groundwater flow in the surficial aquifer in the study area. The areal and depth distributions of detectable residues in groundwater did not correlate with a vulnerability index, nor any of the component scores developed to estimate that index using the DRASTIC method. The shallow depth of most detections also indicates why few samples from water‐supply wells in this study had measurable concentrations of pesticides; most supply wells are deeper than 10 m below the water table. The low number of contaminated samples from supply wells implies that deep groundwater currently (1992) used for drinking generally does not contain detectable pesticide residues.
Observed and Simulated Transport of a Conservative Tracer under Line‐Source Irrigation
Authors: Comfort S. D. , Inskeep W. P. , Lockerman R. H. 
Published: July 2010

AbstractAlthough a number of solute transport models are currently available to predict the transport of agrichemicals in the vadose zone, validation of these models under field conditions has been limited. This study monitored the transport of a conservative tracer (Br−) under three water regimes (high, medium, and low) imposed by a line‐source irrigation system and tested the validity of the simulation model, LEACHM, to predict Br− transport. In July 1990, RbBr was surface applied to 12 uncropped columns at 56 kg Br− ha−1. Four columns (0.203‐m diam., 1.2‐m length) were positioned in each water regime and equipped with soil solution samplers at 0.36‐, 0.66‐, and 0.96‐m depths. Soil solution samples were taken 20 times over 80 d to monitor Br− transport. Cumulative water applied to each water regime, by irrigation and precipitation, ranged between 251 and 458 mm. Results indicated dramatic differences in Br− transport among water regimes. Complete Br− breakthrough curves (with apex concentrations of approximately 60 mg Br− L−1) were observed under high water regime at all depths whereas the majority of Br− applied to the low water regime remained at or near the 0.36‐m depth. Inputs used to predict Br− transport in LEACHM simulations were either measured directly or estimated from experimental conditions. To simulate Br− transport for each water regime, we used three LEACHM input files, which reflected the variability of the soil profile water release retention coefficients. Results indicated that LEACHM's predictions of Br− concentration (at all depths and under all water regimes) differed from observed means by an average (n = 180) of 9.0 to 9.4 mg Br− L−1 (approximately 15–16% of the average apex concentrations). These results indicate that under the experimental system studied, LEACHM adequately predicted the transport of a conservative tracer in the vadose zone.
Cotton Yield Losses and Ambient Ozone Concentrations in California's San Joaquin Valley
Authors: Olszyk D. , Bytnerowicz A. , Kats G. , Reagan C. , Hake S. , Kerby T. , Millhouse D. , Roberts B. , Anderson C. , Lee H. 
Published: July 2010

AbstractBased on controlled experiments and simulation modeling, ozone (O3) has been estimated to cause significant yield losses to cotton. The study reported here was conducted to verify losses for ‘Acala’ cotton (Gossypium hirsutum L. ‘SJ2’) along a gradient of ambient O3 concentrations across the San Joaquin Valley in California. Cotton was grown in nonfiltered (NF) and charcoal‐filtered (CF) open‐top chambers, and ambient air (AA) at four sites during the 1988 and 1989 summer growing seasons. Cotton yields (weights of mature bolls m−2) were reduced in NF compared with CF air in general proportion to O3 concentrations across all sites and years. Greatest cotton yield losses were as Shafter in the southern part of the San Joaquin Valley (20% in 1989), and lowest losses were at Five Points in the western part of the valley (none in 1989). Ozone injury symptoms on cotton were most noticeable in areas with greatest yield losses. Linear O3 exposure vs. predicted relative yield loss models using four common exposure indices were constructed for each site and year based on the NF, CF, and AA data. All models except the second highest daily maximum concentration (2ndHDM, the current ambient air quality standard for O3) predicted yield losses comparable to those predicted with previously published models for cotton in the San Joaquin Valley. Ozone exposure indices giving more weight to higher O3 concentrations or the 7‐h daytime mean better predicted cotton yield responses over the growing season than 2ndHDM.
Sewage Sludge Proteins: II. Extract Characterization
Authors: Lerch R. N. , Azari P. , Barbarick K. A. , Sommers L. E. , Westfall D. G. 
Published: July 2010

AbstractThe characterization of sewage sludge proteins is necessary to better understand their degradation by microbial populations when sludges are utilized for land application. The objective of this study was to characterize the molecular weights of extractable sewage sludge proteins by dialysis partitioning and polyacrylamide gel electrophoretic (PAGE) separation. Sewage sludges obtained from seven municipalities were extracted using H2O and 1 M NaOH followed by purification and concentration to facilitate molecular weight determinations. Dialysis partitioning of proteins showed that the majority of these compounds had molecular weights < 14 000 (i.e., they were not retained by dialysis membrane). The separation of proteins by PAGE also showed that the bulk of H2O and 1 M NaOH soluble proteins were of low molecular weight (< 17 000). This indicated considerable proteolysis during waste treatment processing. Thus, the extractable sludge proteins appeared to be primarily poly‐ and oligopeptides rather than intact proteins. Based on these findings, sludge proteinaceous materials would be expected to degrade rapidly in soil due to the many soil microorganisms capable of utilizing protein degradation products.
Estimating Daily Nutrient Fluxes to a Large Piedmont Reservoir from Limited Tributary Data
Authors: Nearing M. A. , Risse R. M. , Rogers L. F. 
Published: July 2010

AbstractPhysically based models of lakes require estimates of daily, spatially varied water and nutrient fluxes into the lake from surrounding watersheds. Often, however, only a selected set of streams are periodically (monthly or biweekly) sampled. The objective of this study was to develop and test a method for estimating daily flux of nutrients into a large reservoir using data from sampling of selected watersheds. Flow rate, nitrate (NO3‐N), total nitrogen (TN), soluble reactive phosphorus (SRP), total phosphorus (TP), and chemical oxygen demand (COD) were measured monthly during 1991 for eight watersheds that feed Lake Lanier in northern Georgia. Daily stream flow in the eight streams was correlated to data from nearby USGS gauged stream stations, and daily nutrient concentrations were related to watershed land use and monthly variation in measured concentrations. Fraction of agricultural land in the watershed (AG) was the only land use parameter that correlated to nonpoint‐source loads. Coefficients of determination for linear regressions between AG and NO3‐N, TN, SRP, TP, and COD were 0.74, 0.73, 0.47, 0.84, and 0.52, respectively. The relationships were tested on an independent data set consisting of two samples from 19 additional streams. Coefficients of determination (r2) between measured and predicted data for the independent test data was 0.77, 0.52, 0.66, 0.64, 0.69, and 0.76 for stream flow, NO3‐N, TN, SRP, TP, and COD, respectively. Percentages of nutrient loads attributable to nonpoint‐source loads ranged between 76% for TN to 92% for TP and COD, whereas those attributable to agricultural nonpoint source were about 15% for COD, 28% for TN, 34% for NO3‐N, 40% for TP, and 70% for SRP.
Orthophosphate and Calcium Carbonate Solubilities in the Upper Jordan Watershed Basin
Authors: Salingar Yigal , Geifman Yoel , Aronowich Michael 
Published: July 2010

AbstractAn understanding of the mechanisms controlling the P concentrations in the Upper Jordan River is necessary to develop strategies to avoid eutrophication of Lake Kinneret. This study examines the solubility of orthophosphate and CaCO3 in the calcareous Upper Jordan Basin via a thermodynamic model. The variation in alkalinity, pH, Ca, and phosphate concentrations in the surface waters of the Jordan River are consistent with an equilibrium between the solution and a metastable Ca phosphocarbonate phase with an apparent composition of Ca2(HCO3)2HPO4. This phase, CBP2, has not been observed in sediments or suspended particles. However, it rapidly forms on calcite surfaces in laboratory experiments. The CBP2 is replaced after a few days by a more stable compound, CBP3, with an apparent composition of Ca3(HCO3)3PO4. The apparent solubility product of CBP2 is 10−19.96±0.87. The consistency of the observed water chemistry collected from a variety of stations in the Upper Jordan Watershed over a period of 20 yr with this simple metastable “equilibrium” model suggests that CBP2 is rapidly formed in the Jordan River waters and its tributaries and needs to be considered in models of fluvial P transport.
Erosion Response of a Disturbed Sagebrush Steppe Hillslope
Authors: Goff Bruce F. , Bent Gardner C. , Hart George E. 
Published: July 2010

AbstractLand management activities that disrupt surface vegetation cover pose a serious threat to the long‐term stability of buried‐waste sites located within the semiarid sagebrush (Artemisia tridentata Nutt.) steppe region of the northwestern USA. In this study, we evaluated the erosion response of a sagebrush hillslope subjected to three vegetation cover treatments: natural (undisturbed), bare (plant canopy and litter cover removed), and clipped (canopy removed). A rotating boom rainfall simulator was used to apply rain at 60 or 120 mm/h intensities to runoff plots (3.0 m by 10.7 m) with dry, wet, and very wet antecedent moisture conditions, and during two late and one early summer seasons. Supplemental overland flow was added at the upper end of each plot to simulate increased slope length during very wet runs. Maximum soil loss rates on the natural, clipped, and bare treatments were, respectively, 1, 5, and 216 mg/m2 per s during the 60 mm/h rainfall intensity, and 13, 79, and 1473 mg/m2 per s during the 120 mm/h rainfall intensity. Cumulative soil loss was typically 100 to 1000 times greater on the bare treatment than on the natural or clipped treatments. Increases in simulated slope length produced a near linear increase in soil loss from the bare treatment plots (about 0.02 g/m2 per s soil loss per m of slope length) until 30 m, after which the effect of slope length declined. Surface crust development and mound‐intermound microtopography played important roles in governing soil detachment and transport on the hillslope. Despite high rainfall intensity and surface runoff rates, rill erosion was negligible on both the undisturbed and disturbed portions of the hillslope.
Adsorption and Mobility of Cadmium in Natural, Uncultivated Soils
Authors: Sánchez‐Martín M. J. , Sánchez‐Camazano M. 
Published: July 2010

AbstractThe influence of soil properties on the adsorption and mobility of Cd was studied in 22 natural, uncultivated soils from Salamanca province to understand the environmental characteristics of Cd as a pollutant. Cadmium adsorption was studied by means of adsorption isotherms, using low Cd concentrations that were similar to those potentially found in polluted soils, and Cd mobility was investigated by using soil thin layer chromatography. The Freundlich adsorption constant (K) was not found to be related to any soil properties studied. In contrast, the distribution coefficients (Kd) at 15 and 30 µg L−1 equilibrium concentrations were found to be related to the cation exchange capacity (CEC) of the soil (r = 0.43 and r = 0.44, respectively, p < 0.05). The adsorption (Q), amount adsorbed at high concentrations (Ci = 1000/µg L−1), was found to be significantly related to the CEC, the exchangeable Ca2+ content and the sum of bases. In addition, Rf values, which are indicative of the Cd mobility in soil, bore a highly significant (p < 0.001) negative correlation with some soil parameters such as pH, the exchangeable Ca2+ and Mg2+ contents and the sum of bases, as well as a less significant (p < 0.05), negative correlation with the CEC and clay content of the soil, but no correlation whatsoever with the adsorption constants. The type of organic matter present in the soil must be more influential on Cd mobility than was its content. The above results confirm that a CEC of a soil is highly influential on Cd adsorption and mobility.