bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Solid‐Phase Extraction Based Soil Extraction Method for Pesticides of Varying Polarity
Authors: Turin H. J. , Bowman R. S. 
Published: July 2010

AbstractSolid‐phase extraction (SPE) is an innovative method for efficiently and quantitatively extracting pesticides from large numbers of soil samples. An extraction method using commercially available SPE columns has been developed and tested using three herbicides of varying polarity: bromacil [5‐bromo‐6‐methyl‐3‐(1‐methylpropyl)‐2,4(1H,3H)pyrimidinedione], napropamide [N,N‐diethyl‐2‐(1‐naphthalenyloxy)propanamide], and prometryn [N,N′‐bis(1‐methylethyl)‐6‐(methylthio)‐1,3,5‐triazine‐2,4‐diamine]. The soil sample is shaken with a methanol/water mixture and centrifuged. The supernatant is then diluted with a concentrated NaCl solution, and drawn through an SPE column. The sorbed pesticides are finally eluted from the column with methanol. This method requires no specialized laboratory equipment and is well suited for processing large numbers of samples. Analyses of spiked soil samples show recoveries of over 90% and average coefficients of variation (CV's) ranging from 5% at high soil pesticide concentrations to 18% at lower concentrations. The practical detection limit for the method is approximately 10 µg/kg.
Agricultural Water Quality Priorities: A Symposium Overview
Authors: Gish Timothy J. , Sadeghi Ali 
Published: July 2010

AbstractTo meet the global needs of a growing population, both increased productivity and additional land may need to be dedicated to agriculture. However, to effectively evaluate the impact of new farming strategies and agricultural chemicals on the environment, a broad perspective is needed to prevent simply shifting pollution from one part of the hydrologic cycle to another. The loss of agricultural chemicals to the environment may include a combination of processes such as volatilization, runoff and leaching, each exhibiting considerable spatial and temporal dependency. Subsequent losses of agricultural chemicals to the environment may also be transported offsite, having a potential detrimental effect on the environment. This overview provides a brief introduction to the papers presented at a special USDA‐ARS symposium entitled “Agricultural Water Quality Priorities, A Team Approach to Conserving Natural Resources.”
Occurrence of Nitrate in Groundwater—A Review
Authors: Spalding R. F. , Exner M. E. 
Published: July 2010

AbstractThe results of federal, state, and local surveys, which included more than 200 000 NO3‐N data points, are summarized in this review of NO3 in groundwater in the USA. The levels of NO3‐N are associated with source availability and regional environmental factors. In regions where well‐drained soils are dominated by irrigated cropland, there is a strong propensity toward the development of large areas with groundwater that exceeds the maximum contaminant level of 10 mg/L NO3‐N. Most of these areas are west of the Missouri River where irrigation is a necessity. Aquifers in highly agricultural areas in the southeastern USA reportedly are not contaminated. Vegetative uptake and denitrification in this warm, wet, C‐rich environment are responsible for the natural remediation of NO3 in shallow aquifers. In the Middle Atlantic states and the Delmarva Peninsula, localized contamination occurs beneath cropped, well‐drained soils that receive excessive applications of manure and commercial fertilizer. Extensive tile drainage has for the most part prevented a NO3 problem in the groundwater of the Corn Belt states. Throughout the USA there are recurring themes. They include a decrease in NO3‐N levels with depth; lower NO3‐N levels in shallow wells (< 8 m); and a significant increase in NO3‐N in older wells and in wells with poor construction. The factors affecting the distribution of NO3 in aquifers are complex and poorly understood. Interdisciplinary studies using discrete depth sampling, hydrogeological indicators, isotopic tracers, and microbiological techniques are necessary to unravel the complex dynamics.
RUSLE Model Description and Database Sensitivity
Authors: Renard K. G. , Ferreira V. A. 
Published: July 2010

AbstractWater quality modeling generally requires estimates of the amount of eroded material entering water courses. This information is necessary because sediment often transports adsorbed chemicals. Numerous models have been developed to assist with assessment of this problem. These models often contain some modification of the Universal Soil Loss Equation (USLE). A recently initiated effort to improve USLE technology has produced a computer‐based model, RUSLE (Revised USLE), which employs new relationships to estimate values of the six factors in the equation. Three input databases are required: climatic data, crop data, and field operations data. Although numerous specific entries for these data are contained in the program, in many cases users must supplement or modify the supplied data. Results of a sensitivity analysis help users tailoring the databases to specific conditions.
Modeling the Transport of Solutes to Groundwater Using Transfer Functions
Authors: Roth Kurt , Jury William A. 
Published: July 2010

AbstractTransport of chemicals through the unsaturated zone into groundwater is in general a highly nonlinear process with a pronounced spatial structure of which only a very limited number of measurements is economically and technically feasible. In most applications, it is thus not practicable to model these processes with high spatial and temporal resolutions. However, in an agricultural environment chemicals are usually applied to large areas, and we are generally interested in their long‐term effects on groundwater quality. With these restrictions, the transport processes may be averaged in space and time over sufficiently large regions such that it may be permissible to use a stationary, linear approximation. An efficient way to study such systems exploits that a stationary, linear system is completely determined by its transfer function, that is, by its response to a narrow pulse input. We use a general formalism to represent the transport processes implicitly by the relation between the flux and the resident concentration of a conservative chemical. To model the transport of nonconservative chemicals, this description is coupled, as it was done by (Villermaux, 1981), with a model of the local interactions. We obtain an expression for the transfer function of a linearly adsorbing chemical with linear adsorption kinetics and first‐order decay in the water and in the adsorbed phase which is based on the measured transfer function of a conservative tracer. This procedure has the major advantage that parameter estimation and model validation tests can be applied to the chemical reaction processes alone.
Sorption of Para‐Xylene Vapors on Salt‐Treated Soils Measured by Flow‐Equilibration and Gas Chromatography Methods
Authors: Rhue R.D. , Pennell K.D. , Reve W. H. , Hornsby A. G. 
Published: July 2010

AbstractThe impact of soil properties other than organic C content and surface area on vapor‐phase sorption has rarely been considered. This study was conducted to determine the effect of salt, namely CaCl2, on the sorption of p‐xylene vapor under anhydrous and hydrated conditions. Sorption on Webster soil (Typic Haploquolls) before and after removal of organic C was measured using a flow‐equilibration method. In addition, the utility of an eluted pulse gas chromatography method was evaluated using the sand fraction of Oldsmar soil (Alfic Arenic Haplaquods) as a column‐packing material. The CaCl2 significantly decreased p‐xylene sorption at both 0 and 90% RH for both adsorbents. Under anhydrous conditions, reduced sorption by Oldsmar sand was evidenced at low p‐xylene vapor pressures by a constant net retention volume and symmetrical peaks, indicating linear sorption and ideal behavior at these vapor pressures (i.e., the Henry's region). In the absence of salt, the net retention volume continued to increase at p‐xylene vapor pressures as low as 0.33 Pa, indicating isotherm nonlinearity, even at this low vapor pressure. This difference in retention behavior suggests that salt modified the nature of the surface of the sorbents. Under hydrated conditions, the reduction in sorption may be related to the salting‐out effect of CaCl2 on gas solubility in adsorbed water films. These data suggest that the distribution and migration of organic vapors may be substantially greater in salt‐affected soils due to reduced sorption on both the dry and water‐coated solid phases that are present.
Toxicity of Tributyltin Chloride to Anaerobic Nitrogen Transformations in Sediment and Porewater
Authors: Bergeron Virginie , Blais Jean Simon , Wharf Ivor , Marshall William D. 
Published: July 2010

AbstractThe influence of tributyltin chloride (TBTCl) on N transformations in anoxic sediment cultures, during approximately 14‐d incubations, was studied using acetylene inhibition and acetylene reduction techniques as measures of microbially mediated denitrification and dinitrogen fixation, respectively. The accumulation of N2O, CO2 and C2H4 with time was modeled with a best‐fit polynomial to detect statistically significant differences between treatments and with a three‐segment continuous line model to assess lag times, rates of accumulation and rates of subsequent loss of these gases from the headspace. In sediment cultures, the presence of up to 100 mg L−1 of TBT had a barely detectable influence on these transformations. However, the analogous processes in porewater, prepared by centrifuging sediment slurry at 3 000 × g for 30 min, were appreciably modified by the presence of > 1 mg L−1 of this toxicant. Although the two media were different in terms of their denitrifying potential and their fermenting capacity, dose‐related responses in the porewater were evident for both processes. Apparently the presence of particulate matter in the sediment slurry appreciably attenuated the inhibitory effects of the toxicant. Moreover, a portion of the denitrifiers in cultures of porewater developed a resistance to 100 mg L−1 of TBT in the medium and reduced added nitrate stoichiometrically. When transferred to autoclaved medium containing the same level of toxicant, aliquots of the resistant culture stoichiometrically reduced the added nitrate after a shorter lag time. The resistance was not the result of metabolic detoxification as indicated by the recovery of 74% of toxicant in an unchanged form, after 15 d incubation, using analytical methods which would have detected a 1% conversion of TBT to either Bu2Sn2+ or to BuSn3+. When added, at 10 mg L−1, to autoclaved porewater, an appreciable portion of the toxicant became associated with residual particulate matter (the fraction removed by centrifugation at 10 000 × g but not by 3 000 × g) with only approximately 9% remaining in the supernatant fluid. When 0.5 mL of TBT‐resistant culture was added to the identical matrix and incubated, the TBT in the supernatant phase was reduced below the limit of detection and only 40% was recovered in the particulate/microbial cell fraction. Thus, both particulate materials and microbial growth immobilized TBT serving to limit its concentration in the surrounding water.
Hydrologic Controls in Nitrate, Sulfate, and Chloride Concentrations
Authors: Schnabel R. R. , Urban J. B. , Gburek W. J. 
Published: July 2010

AbstractNitrate‐nitrogen, SO4, and Cl concentrations and discharge rates from a small, upland watershed in east central Pennsylvania were analyzed in the context of a layered aquifer. A pattern of greater NO3‐N concentrations during periods of greater discharge was generally followed by declining concentrations during hydrograph recession. The coincident temporal pattern of NO3‐N and discharge appears hydrologically controlled because both NO3‐N and SO4 exhibited similar patterns even though there are important differences in their behavior and reactivity in biologically controlled systems. Chemical concentration patterns in stream flow arose from flow through a two‐layer geologic system in which NO3‐N and SO4 concentrations were different between layers. The substantially lower concentrations observed in the deeper water were attributed to recharge from areas with forest and mixed land uses. Discharge from this deeper layer supported the lowest flows and the lowest chemical concentrations observed in stream flow. Increases in stream flow resulted from greater discharge from the shallower groundwater layer. Adding discharge from the shallower groundwater resulted in higher chemical concentrations in stream flow. Nitrate‐nitrogen concentration estimated with a mixing cell model, in which concentration changes result from dilution only, closely matched measured concentration.
An Innovative Approach to Estimate Bioavailable Phosphorus in Agricultural Runoff Using Iron Oxide‐Impregnated Paper
Authors: Sharpley Andrew N. 
Published: July 2010

AbstractThe transport of bioavailable phosphorus (BAP) in agricultural runoff can accelerate the eutrophication of receiving water bodies. Bioavailable P is comprised of dissolved P (DP) and bioavailable particulate phosphorus (BPP). Although several algal assays and chemical extractions have been proposed to estimate BAP, procedural and theoretical limitations have restricted their widespread use. This study evaluates the use of Fe oxide‐impregnated paper strips (Fe‐oxide strips) to estimate the potential BAP content of runoff from 20 agricultural watersheds in the Southern Plains during 1988 to 1990. In the proposed method, BAP and DP are determined by shaking 50 mL of unfiltered or filtered runoff, respectively, with one Fe‐oxide strip for 16 h. Phosphorus is removed from the strip by 0.1 M H2SO4 and measured, with BPP calculated as the difference between BAP and liP. Growth of Selenastrum capricornutum was related (r2 = 0.63–0.96) to the BPP content of runoff sediment in 2‐ to 29‐d incubations. Bioavailable PP estimated by the proposed strip method and more widely used NaOH extraction, closely followed a 1:1 relationship. Averaged for all runoff events, strip DP was 90 and 75% of DP determined by standard direct methods, for watersheds with and without tillage, respectively. The lower estimates of strip DP may be partially attributed to a greater transport of acid‐hydrolyzable organic and condensed DP in runoff from no‐till compared to tilled watersheds. Acting as a P sink, the strip method may have a stronger theoretical basis than chemical extraction in estimating algal‐available P in agricultural runoff. In addition, the simplicity of the proposed Fe‐oxide strip method will allow BAP estimation with limited resources and may facilitate evaluation of the impact of agricultural runoff on the biological productivity of receiving waters.
Sewage Sludge Proteins: I. Extraction Methodology
Authors: Lerch R. N. , Barbarick K. A. , Azari P. , Sommers L. E. , Westfall D. G. 
Published: July 2010

AbstractThe extraction and quantitation of sewage sludge proteins is a pre‐requisite to evaluating their role as labile C and N sources in sludge‐amended soil. The objective of this study was to develop extraction methodology for the routine quantitation of sewage sludge proteins. Seven sewage sludges were obtained and prepared by oven drying at 55 °C followed by extensive grinding and mixing to produce homogenous samples. Proteins were extracted using H2O, 10% (v/v) Triton X‐100 (a non‐ionic detergent), and 1 M NaOH, and they were analyzed using the Lowry protein assay with bovine serum albumin standards. Protein contents of extracts ranged from (in g kg−1, dry wt. basis): (i) H2O, 1.3 to 24; (ii) 10% Triton X‐100, 3.6 to 59; and (iii) 1 M NaOH, 53 to 280. Water and detergent‐extractable proteins were less than, and base‐extractable proteins were within, literature values reported for total sludge proteins. The coefficients of variation (CV) for each extractant and all sludges were, with one exception, below 6%. The three methodologies provided precise and reproducible data for the extraction of sewage sludge proteins. The detergent extraction procedure is recommended for routine use because of its shorter extraction time.
A Mechanical Stage‐Height Stormflow Sampler
Authors: Riekerk Hans 
Published: July 2010

AbstractA vacuum‐powered sequential stormflow sampler with intake valves controlled by floats during both rising and falling water levels was developed and tested. The rising float assembly of each subunit triggered a mouse‐trap valve that opened two vacuum lines, one of which directly collected a water sample. Simultaneously, a needle valve in the float pipe closed and kept the second intake line primed. The weight of the float assembly in the falling water level opened the second intake line to collect a water sample. Differences in time‐series data from field trials of the stage‐height sampler with six subunits ascending at 15‐cm intervals as compared with a time‐controlled sampler varied an average of 21 %.
Slope Effects on Cadmium Load of Eroded Sediments and Runoff Water
Authors: Korentajer L. , Stern R. , Aggasi M. 
Published: July 2010

AbstractLittle information is available on the effects of slope on Cd load of runoff water emanating from the Cd‐contaminated soils. A laboratory rainfall simulator study was conducted to assess the effects of slope on runoff, sediment yield, and Cd load of runoff water and eroded soil sediments. The experiment was conducted with three Cd‐amended soils (20 mg kg−1) of varying degrees of erodibility, i.e., Msinga clay loam (Paleudalf, low erodibility), Jozini sandy loam (Haploustalf, moderate erodibility), and Mngazi clay (Pelloxerert, high erodibility), using four slopes (10, 20, 30, and 40%) and three replicates. A Cd‐adsorption experiment and sequential extraction techniques were employed to characterize Cd soil affinity and Cd partitioning in soil. Cadmium runoff losses varied from 4.6 to 58.5% of the applied Cd. Sediment Cd accounted for over 93% of the total Cd load of the runoff slurry. The Cd load of runoff increased with an increasing degree of soil erodibility, reflecting the effects of increased removal of a Cd‐contaminated surface soil layer. With increasing slope, sediment yield and sediment‐associated Cd increased. Slope did not have a significant effect on the soluble Cd load of runoff water. In the Jozini soil, an increase in slope resulted in a sharp decrease in the clay and Cd enrichment ratios (the ratios between clay and Cd contents of the sediment and their respective contents in the soil of origin). In the other two soils enrichment ratios were unaffected by slope. Soluble Cd load of runoff water was less than 28% of the mobile (extractable with 1 M NH4NO3) Cd content of the soils. Differences in soluble Cd load could not be accounted for by the differences in the soils' Cd sorption characteristics or their mobile Cd content, suggesting that these parameters are inappropriate for estimating the extent of soluble Cd losses from the soils.
Estimating Phosphorus in Agricultural Runoff Available to Several Algae Using Iron‐Oxide Paper Strips
Authors: Sharpley A. N. 
Published: July 2010

AbstractThe transport of bioavailable P (BAP) in agricultural runoff can stimulate freshwater eutrophication. Previous research has shown that the amount of P removed by Fe‐oxide impregnated paper strips (Fe‐oxide strips) is related to the growth of Selenastrum capricornutum in laboratory incubations. As only one algal type was used, additional assays were conducted to determine if Fe‐oxide strips can estimate the potential bioavailability of P in runoff to Anabaena, Ankistrodesmus, and Euglena, which are common in eutrophic waters of the Southern Plains. Algal growth was related (P > 0.001) to the amount of P extracted from runoff sediment by Fe‐oxide strips. For a given strip P content of runoff sediment, algal cell count increased in the order Anabaena, Euglena, Selenastrum, and Ankistrodesmus. Thus, the amount of P removed from runoff by Fe‐oxide strips, estimates the BAP content of runoff that may be potentially available for uptake by several common freshwater algae.
Boron and Selenium Removal in Boron‐Laden Soils by Four Sprinkler Irrigated Plant Species
Authors: Bañuelos G. S. , Cardon G. , Mackey B. , Ben‐Asher J. , Wu L. , Beuselinck P. , Akohoue S. , Zambrzuski S. 
Published: July 2010

AbstractHigh concentrations of B and Se found in some arid environments are detrimental to sustainable agriculture. Vegetation management may be a remediation strategy designed to reduce soil B and Se concentrations to nontoxic levels. Two separate field experiments were conducted to study B and Se uptake in four different plant species grown in soil containing high concentrations of B (water‐extractable B ranging from 1–10 mg kg−1 soil) and Se (total soil Se ranging from 0.1–1.2 mg kg−1 soil). The four species were Brassica juncea L. Czern and Coss (Indian mustard), Festuca arundinacea Schreb cv. Fawn (tall fescue), Lotus corniculatus L. (birdsfoot trefoil), and Hibiscus cannibinus L. (kenaf). In the 1990 experiment, there were no differences in either tissue B or Se concentrations among the species. The mean tissue concentration was 105 mg B kg−1 dry matter (DM) and 0.75 mg Se kg−1 DM, respectively. In the 1991 experiment, mean shoot tissue concentrations of B ranged from a low of 96 mg kg−1 DM in tall fescue to a high of 684 mg B kg−1 DM in leaves from kenaf. Indian mustard accumulated the greatest amount of Se (>1 mg Se kg−1 DM), while the mean tissue concentration among the other three species was 0.36 mg Se kg−1 DM. For both experiments, soil samples were taken prior to planting and after harvest for each species to a depth of 0 to 30 and 30 to 60 cm, and analyzed for water‐extractable B and total Se. Summary data from all species indicated that extractable soil B and total Se concentrations were reduced between 0‐ to 60‐cm soil depth by 52 and 48% in 1990, and by 24 and 13% in 1991, respectively. Planting any of the four species tested in B‐laden soils may lead to a reduction in both B and Se concentrations in the soil.