bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of a Prototype Decision Support System for Selecting Trench Cap Designs
Authors: Paige G. B. , Stone J. J. , Lane L. J. , Yakowitz D. S. , Hakonson T. E. 
Published: July 2010

AbstractA computer‐based prototype decision support system (PDSS) to assist the risk manager in selecting an appropriate trench cap design for waste disposal sites is evaluated. The selection of the “best” design among feasible alternatives requires consideration of multiple and often conflicting objectives. The methodology used in the selection process consists of: selecting and parameterizing decision variables, using data, simulation models, or expert opinion; selecting feasible trench cap design alternatives; ordering the decision variables and ranking the design alternatives. The simulation models incorporated in the PDSS are the Hydrologic Evaluation of Landfill Performance (HELP) model which is used to simulate the trench cap water balance and the Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) erosion component that is used to simulate trench cap erosion. The decision model is based on multi‐objective decision theory and uses a unique approach to order the decision variables and rank the design alternatives. The PDSS is evaluated using the Hill Air Force Base landfill cover demonstration project. The water balance and surface erosion of four alternative landfill cover designs were monitored for a 4‐yr period. Two of the cover designs were used to calibrate and test the simulation models. The results of the PDSS, using both data from all four designs and long‐term simulations from two of the designs, illustrate the relative advantages of each of the cover designs and which cover is the “best” alternative for a given set of criteria and a particular importance order of those decision criteria.
Carbofuran Degradation and Metabolite Incorporation during Solid State Fermentation
Authors: Willems Hans P. L. , Berry Duane F. , Mullins Donald E. 
Published: July 2010

AbstractWe investigated the suitability of solid state fermentation (SSF) as a means to dispose of carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate). The fate of [U‐ring‐14C] labeled carbofuran was determined in incubation chambers containing either sphagnum peat moss (limestone‐amended) or a peanut hulls/peat moss/steam‐exploded wood (1:1:1) mixture (PPW). Ethyl acetate‐extractable, and alkali soluble and insoluble fractions were evaluated for radioactivity following either a 4‐ or 8‐wk incubation period at 35°C. The majority of the radioactivity (80–98% of applied activity) was associated with the matrix materials at the end of the incubation period for both matrix materials with no significant mineralization observed. For peat, the majority of radioactivity was associated with the alkali insoluble fraction (63.5%), with only 8% of the applied activity found in the ethyl acetate extract after 8 wk. For the PPW mix, 71% of the applied radioactivity was recovered in the ethyl acetate extract, whereas 11% of the applied activity was found in the alkali insoluble fraction after 8 wk. The metabolite carbofuran‐7‐phenol, detected in the ethyl acetate extracts of the peat and PPW mix following 4 and 8 wk of incubation, was susceptible to oxidative coupling in the presence of horseradish peroxidase (HRP) and H2O2, suggesting that this metabolite had become covalently bound to organic matter during humic substance formation. These results may provide the basis for the development of an effective and economical method for detoxification or containment of waste pesticide residue.
Atmospheric Deposition to a Low‐Elevation Spruce‐Fir Forest, Maine, USA
Authors: McLaughlin James W. , Fernandez Ivan J. , Richards Karen J. 
Published: July 2010

AbstractA spruce‐fir forest in central‐Maine, USA, has been the site of dry and wet atmospheric deposition measurements since 1988. Precipitation flux of hydrogen ions (H+) and sulfate (SO2−4) decreased by 24 and 42%, respectively, during the study period, but no temporal trends occurred for precipitation H+ or SO2−4 concentrations. Decreased precipitation fluxes were likely due to a 33% decrease in precipitation amounts during the latter years of the study. Both H+ and SO2−4 concentrations and fluxes in throughfall decreased, corresponding to decreases in dry deposition of those constituents. No nitrate (NO−3) concentration or flux trends occurred in precipitation, throughfall, or dry deposition. Hydrogen, NO−3, and NH+4 had a negative net canopy exchange (NCE) attributable to N deficiency at this site and acid neutralization in the canopy. Sulfate and magnesium (Mg2+) were conservative and had no NCE. Calcium (Ca2+) and potassium (K+) had a positive NCE due to canopy leaching. A comparison of bulk and wet‐only precipitation collectors showed that SO2−4, Ca2+, and K+ concentrations were greater in solutions from a bulk collector compared with a wet‐only collector. The differences were partially attributable to dry deposition. Throughfall H+, Ca2+, and dissolved organic carbon (DOC) concentrations were higher in weekly wet‐only collections composited monthly, compared with weekly bulk collections composited either weekly or monthly. Nitrate concentration, however, was lowest in the wet‐only throughfall collections. Differences likely resulted from spatial variability. Ongoing research is attempting to further define trends apparent to date, and to determine the mechanisms controlling these characteristics.
Fate of Dissolved Toluene during Steady Infiltration through Unsaturated Soil: I. Method Emphasizing Chloroform as a Volatile, Sorptive, and Recalcitrant Tracer
Authors: Allen‐King Richelle M. , Gillham Robert W. , Barker James F. 
Published: July 2010

AbstractChloroform can be used as a volatile, sorptive, and recalcitrant tracer compound relative to volatile and transformable organic compounds, such as toluene, in aerobic unsaturated soil column experiments. Chloroform concentrations <4 mg/L did not affect the rate of toluene oxidation and chloroform itself was not transformed aerobically. In the current experiments, chloroform was applied at lower concentrations than the degradable compound. Chloroform was used to estimate the column mass balance without degradation so that mass loss for the degradable compound in the column could be confidently attributed to transformation. Consistent numbers of viable heterotrophic microorganisms in soil samples from column experiments with and without chloroform added suggest that the added chloroform did not have a negative effect on the soil microorganism population.
Fate of Dissolved Toluene during Steady Infiltration through Unsaturated Soil: II. Biotransformation under Nutrient‐Limited Conditions
Authors: Allen‐King Richelle M. , Gillham Robert W. , Barker James F. , Sudicky Edward A. 
Published: July 2010

AbstractBiotransformation rates for dissolved toluene in unsaturated sandy soil were determined in dynamic column infiltration experiments. Transformation rates under N‐limited conditions and in the presence of sufficient oxygen were 8 to 35 mg (kg d)−1 and appeared to follow zero order kinetics. Toluene‐degrading microoganisms were demonstrated to increase significantly in both activity and numbers with exposure to toluene. Relatively low CO2 production to oxygen consumption ratios were observed during these experiments suggesting incomplete toluene mineralization. Over the ranges tested, water flux (20–80 cm d−1) and toluene concentration (4–46 mg L−1) appeared to have a secondary control on rate relative to nutrient and/or oxygen limitations. Under conditions where the oxygen concentration was near zero due to removal by toluene degradation in the soil columns, the transformation rate was sufficiently low to be insignificant relative to column residence time.
Biodegradation of 3‐Chlorobenzoate as Affected by Rhizodeposition and Selected Carbon Substrates
Authors: Haby Paul A. , Crowley David E. 
Published: July 2010

AbstractThe plant rhizosphere has been hypothesized to generally increase the population numbers and activity of soil microorganisms that degrade various xenobiotic contaminants. However, the relative importance of increased C availability in the rhizosphere to microorganisms that directly metabolize xenobiotics as a C source for growth or that degrade xenobiotics through growth‐linked metabolism and cometabolism is not well understood. We hypothesized that when a xenobiotic can be used directly as a growth substrate, the rhizosphere would have relatively little influence on the catabolizer population since the substrate provides an independent nutritional niche. However, increased C levels in the rhizosphere might enhance the numbers of microorganisms that degrade the xenobiotic through cometabolism or metabolism that is linked to growth on other substrates. To further examine this hypothesis, experiments were conducted with soil containing indigneous microorganisms capable of degrading the model compound 3‐chlorobenzoate (3‐CB). The results showed degradation of 3‐CB in 1:1 soil/water slurries from ryegrass rhizosphere soil that had not been previously exposed to 3‐CB had a faster initial rate of 3‐CB degradation than nonrhizosphere soil. This rhizosphere effect could be simulated in nonrhizosphere soil using glucose, mannitol, or benzoate. A long‐term experiment further showed that the population size of microorganisms that degraded 3‐CB in the absence of supplemental C (catabolizers), and those that degraded 3‐CB in the presence of supplemental C, for example, via growth‐linked metabolism or cometabolism, were enriched by 40‐ and 250‐fold, respectively, in rhizosphere soil. In contrast, planted and nonplanted microcosms that were repeatedly exposed to 3‐CB over 24 wk were similarly enriched for 3‐CB degraders, which had a MPN of 4 × 108 g−1 soil. Our results suggest that under conditions where there is not constant exposure of the microbial population to 3‐CB as a C source, C provided by rhizodeposition may primarily enhance the population numbers of microorganisms that degrade 3‐CB by cometabolic or growth‐linked metabolism, and thereby promote rapid depletion of 3‐CB from soil during short term or low level exposure to the xenobiotic.
Use of XAS to Determine the Chemical Speciation of Bioaccumulated Manganese in Potamogeton pectinatus
Authors: Lytle C. M. , Lytle F. W. , Smith B. N. 
Published: July 2010

AbstractManganese (Mn) accumulation was measured in Potamogeton pectinatus L. (sago pondweed) over a growing season. Leaf tissue Mn content increased from 120 mg kg−1 in June to 4990 mg kg−1 by October. Our objective was to chemically speciate bioaccumulated Mn in P. pectinatus with x‐ray absorption spectroscopy (XAS). Differences were found in Mn valence in leaf tissue between June, October, and January when compared to model inorganic Mn compounds. Manganese in June leaf tissue was most like [Mn2+ (H2O)6]. By October, average valence of Mn in leaf and root tissues was similar to Mn3O4. However, there was little agreement in the chemical structure of Mn in these tissues and Mn3O4. Senescent leaf tissue in January differed from October because the valence had shifted back toward Mn2+. The Mn3+ fraction had leached from leaf tissue between October and January. This coincided with a decrease in total Mn concentration during this same period. Manganese bioaccumulation in this aquatic species occurs in two phases: (i) Mn2+ is bound in finite sites and coordinated by water, (ii) once filled, Mn2+ is oxidized and stored as a Mn3+ oxide within the plant that can be leached upon senescence.
A Site‐Specific Farm‐Scale GIS Approach for Reducing Groundwater Contamination by Pesticides
Authors: Mulla D. J. , Perillo C. A. , Cogger C. G. 
Published: July 2010

AbstractIt has been proposed to vary pesticide applications by patterns in surface organic C to reduce the potential for contamination of groundwater. To evaluate the feasibility of this “precision farming” approach, data for carbofuran concentrations from 57 locations sampled to a depth of 180 cm were fit to the convective‐dispersive equation. Fitted values for pore water velocity (v) ranged from 0.17 to 1.92 cm d−1, with a mean of 0.68 cm d−1. Values for dispersion (D) ranged from 0.29 to 13.35 cm2 d−1, with a mean of 3.49 cm2 d−1. Values for the retardation factor (R) ranged from 1.28 to 6.83, with a mean of 2.57. With this data, risks of pesticide leaching were estimated at each location using the attenuation factor (AF) model, and dispersion based leached factor (LF) model. Using the AF model gave two locations with a very high pesticide leaching risk, 32 with a high pesticide leaching risk, 15 with a medium risk, 6 with a low risk, and 2 with no risk. Using the LF model, 6 had a high risk, 13 had a medium risk, 18 had a low risk, and 20 had no risk. Pesticide leaching risks were not correlated with any measured surface soil properties. Much of the variability in leaching risk was because of velocity variations, so it would be incorrect to assume that surface organic C content controls the leaching risk.
Scale‐Dependency of Solute Transport Modeling/GIS Applications
Authors: Wagenet R. J. , Hutson J. L. 
Published: July 2010

AbstractThe movement of water through the soil profile and the consequent displacement and transformation of chemicals dissolved in the water is a key concern in preventing water quality degradation, with its eventual impact on living systems, both human and otherwise. Predictions of the effect of a particular water and chemical management system at the soil surface will lead to more enlightened control of chemicals introduced into the environment as pesticides, fertilizers, or waste products. The use of geographic information systems (GIS) in concert with simulation modeling of soil leaching processes is becoming more widespread as a procedure applied to environmental chemical fate issues. The use of GIS has brought to the forefront the spatial scale of such databases as soil survey, elevation, climate and land use, and their use in the modeling process. An accompanying concern is the spatial scale at which any simulation model is assumed to be accurate, and the spatial scale at which both model input and field‐verification data should be generated. Such modeling presently consists of a number of approaches, some useful at several spatial scales, and others more limited by the assumptions inherent in their development. This paper discusses these issues, and presents two case studies as examples.
Estimating Recharge Rates for a Groundwater Model Using a GIS
Authors: Fayer M. J. , Gee G. W. , Rockhold M. L. , Freshley M. D. , Walters T. B. 
Published: July 2010

AbstractSome of the defense wastes at the Hanford Site in southeastern Washington State are stored in the vadose zone. It is possible that natural recharge could mobilize and transport the contaminants in these wastes to the groundwater, as well as influence groundwater velocities and directions. The objective of this study was to estimate the areal distribution of natural recharge for use as a boundary condition for a groundwater flow and transport model. A geographic information system (GIS) was used to identify all possible combinations of soil type and vegetation and assign to each an appropriate estimate of recharge. The strategy was to assign estimates based on field data and supplement with simulation results only when necessary. The estimated rates varied from 0.7 to 127.1 mm/yr. The order of preference for assigning estimates was lysimetry > water content measurements > tracers > modeling, based on qualitative estimates of the relative error of each method as applied. The GIS software was used to estimate the annual recharge volume attributable to specific soil‐vegetation combinations. The total annual recharge volume was 8.47 × 109 L for the 765 km2 portion of the site containing the major waste storage areas. This volume is from 2 to 10 times higher than estimates of runoff and groundwater flow from adjacent higher elevations and is equivalent to facility discharges in 1992. The recharge map showed the impact of a 1984 fire on increasing recharge; it also illustrated the higher recharge rates associated with disturbed soils in the waste storage areas.
Using GIS in Simulation of Nitrate Leaching from Heterogeneous Unsaturated Soils
Authors: Wu Q. Joan , Ward Andrew D. , Workman Stephen R. 
Published: July 2010

AbstractSolute transport within and through unsaturated soils are important processes that can affect agricultural systems and groundwater supply and contamination. Nitrate (NO−3) leaching from three 10‐ha experimental plots under different agricultural practices was studied. A Geographic Information System (GIS) model, ARC/INFO was used to help decompose the three hydrologic environments into 34 subenvironments. Each subenvironment was discretized vertically as three modeling units. Within each modeling unit, soil physical and chemical properties were described by a random multivariate normal (MVN) vector with conditional probability. A one‐dimensional, field‐scale, continuous flow model, Groundwater Loading Effects of Agricultural Management Systems (GLEAMS), was then stochastically applied to each subenvironment by using generated MVN realizations for every modeling unit. Observed NO−3 leaching below 1‐m depth was estimated with a mass balance approach based on suction lysimeter data. The observed NO−3 loads were then compared to predictions from the stochastic simulation. Statistical analysis of the effects of agricultural practice and soil type on NO−3 leaching was conducted based on modeling results. Observed and predicted results showed (i) no significant difference between mean values of observed and predicted mean NO−3 leaching below the 1‐m depth; (ii) agricultural practice and soil type as well as their interaction had an effect on NO−3 leaching; and (iii) a large amount of spatial variability with respect to NO−3 leaching. The results are important for better understanding solute leaching from heterogeneous agricultural fields and useful in decision making.
Atrazine Loss in Runoff from No‐Tillage and Chisel‐Tillage Systems on a Houston Black Clay Soil
Authors: Pantone D. J. , Potter K. N. , Torbert H. A. , Morrison J. E. 
Published: July 2010

AbstractHerbicide concentration and mass load of runoff depends, to a large extent, on soil management. This study was conducted to determine how tillage impacts herbicide losses in runoff from a vertisol soil on the Blackland Prairie of Texas. Atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] was applied at a rate of 2 kg a.i. ha−1 to a Houston Black clay soil (fine, montmorillonitic, thermic Udic Pellustert) in 1993 at the Blackland Research Center in Temple, TX. For 4 yr, the test area was under continuous management using a wide‐bed system with a wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum [Sorghum bicolor (L.) Moench] rotation. Tillage treatments consisted of no‐tillage or chisel‐tillage. All experiments were repeated four times. A rainfall simulator with an intensity of 12.5 cm h−1 was used to apply rainfall 24 h after the atrazine application. Sediment and runoff samples were collected during five time periods (from runoff initiation to 5, 5 to 10, 10 to 20, 20 to 30, and 30 to 40 min). No differences in atrazine concentrations were found among treatments in either the runoff water or sediment from any of the five time periods; however, crop residues prevented surface seal development and erosion resulting in reduced runoff and sediment losses. No‐tillage treatments significantly reduced runoff and sediment yield, rather than the atrazine concentration of the runoff, resulting in a 42% decrease of the atrazine load in the runoff and a 77% decrease in atrazine associated with the sediment. As a percentage of the total amount applied, runoff accounted for <2% of the atrazine. Sediment‐transported atrazine was much less important and represented <0.03% of the total amount applied.
A Comparison of Distribution Tests and Relevant Point and Interval Estimators
Authors: Haarstad Ketil 
Published: July 2010

AbstractThis is a study of samples from natural, terrestrial environments, with coefficients of variation ranging from 4 to 211%. To select estimators, physical and chemical sample distributions are separated into three categories: normal (N), lognormal (LN), and nonparametric (NP) distributions. The type of distribution is given by (i) the Lilliefors procedure of the Kolmogorov‐Smirnov test (KST), (ii) the Shapiro‐Wilk test (SWT), or (iii) the Skewness test (ST). For 46 samples, 14 (30%) were NP, 14 (30%) were LN, and 18 (39%) were N, based on test (i). Test (ii) gave 14 (30%) NP, 19 (41%) LN, and 13 (28%) N. Only 29 of the 46 samples could be tested by Method (iii) due to the limit on minimum sample size of 25:11 (38%) were NP, 9 (31%) LN, and 9 N. The KST and SWT disagreed in 35% of the samples, whereas KST and ST disagreed in 24% of the samples. The SWT disagreed with ST results in 10% of the samples, when categorizing the distributions at a significance level of 5%. The ratio between the selected point estimator and the mean varied from 13 to 249%, with mean values of 73% for NP and 112% for LN. The ratio between the selected interval estimator and the range varied from 2 to 71%. It is not possible to characterize one of the distribution tests as superior to the others based on the results from this study.
A Versatile Sun‐lit Controlled‐Environment Facility for Studying Plant and Soil Processes
Authors: Tingey David T. , McVeety Bruce D. , Waschmann Ron , Johnson Mark G. , Phillips Donald L. , Rygiewicz Paul T. , Olszyk David M. 
Published: July 2010

AbstractA new environmental‐tracking, sun‐lit controlled‐environment facility (terracosm) that can control and manipulate climatic and edaphic factors while maintaining natural environmental variability was developed to study the effects of environmental stresses on a model ecosystem (i.e., plant and soil processes). An analysis of terracosm performance data indicates that the terracosms simulated natural seasonal and diurnal changes in atmospheric CO2, air and soil temperatures, vapor pressure deficit (VPD), and soil moisture. The terracosm performance data indicate that between 92 and 100% of the hourly CO2 concentrations are within ±50 µmol mol−1 of the target concentrations for both ambient and elevated treatments (1 Nov. 1993 through 30 Nov. 1994). Air temperatures are within 2°C of the target temperature between 85 and 100% of the hours for both ambient and elevated temperature treatments. The VPD was approximately the same (0.09 kPa difference between treatments) in the ambient and elevated temperature treatments. Distributed process control was implemented to minimize downtime. Terracosm downtime, periods when terracosm environmental conditions could not be reliably controlled, varied between 2.4 and 2.8% of all hours, and was equally distributed between biological sampling and equipment problems.