bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respirable‐Dust Production from Agricultural Operations in the Sacramento Valley, California
Authors: Clausnitzer H. , Singer M. J. 
Published: July 2010

AbstractAir quality in California's intensively farmed Central Valley violates regulatory particulate matter limits nearly year‐round. Little is known about the amount of fugitive dust produced by individual agronomic operations. This study measured the respirable fraction, covering particles ≤4 µm in aerodynamic diameter and the influences of climate, soil, and implement conditions on dust production. Respirable dust was collected at the implement from 18 cultural operations for a complete annual crop cycle on 22, 4097‐m2 plots, 11 km west of Davis, CA. Plots included conventional and organic corn (Zea mays L.) and tomato [Lycopersicon lycopersicum (L.) Karsten] fields as well as fields with a winter cover crop or fallow plots followed by wheat (Triticum aestivum L.). The 266 samples were collected with standard cyclone samplers mounted directly on each implement as the dust source (average height of 94 cm above ground). Sampling near the dust source measured the relative respirable‐particulate‐matter production from each operation. The highest average respirable‐dust concentration was 10.3 mg/m3 air from soil ripping and land planing, carried out on dry surface soil. The lowest dust concentration was from disking of corn stubble (0.3 mg/m3) into soil during the wet season. Approximately 64% of all operations were performed during hot and dry weather, producing 83% of the annual respirable dust for this three‐crop system. Among the measured environmental and implement conditions, air temperature, soil moisture, wind speed, and tractor speed were significantly correlated with the dust concentration in an exponential model.
Prediction of Methyl Bromide Flux from Area Sources Using the ISCST Model
Authors: Ross L. J. , Johnson B. , Kim K. D. , Hsu J. 
Published: July 2010

AbstractGrowing concern about atmospheric exposure of humans to pesticides has led to increased air monitoring in California. Air monitoring data typically consist of measurements made downwind from point or area sources. The utility of monitoring at fixed stations is limited for establishing buffer zones to protect neighboring populations from pesticide exposure. A modeling approach designed to use these data would provide the flexibility needed to establish buffer zones. The Industrial Source Complex Short Term (ISCST) model is a gaussian plume dispersion model that predicts air concentrations around point or area sources using emission rates (flux) and meteorological conditions as model inputs. The flux data, however, are typically not collected in the field nor available in the literature. In order to use the field data currently available, we developed a procedure using methyl bromide (MeBr) concentrations around two area sources and the ISCST model, to back‐calculate flux. In addition, MeBr flux was measured concurrently by cooperators conducting an independent study. Air concentrations, together with actual meteorological data, were used as inputs to the ISCST model. Flux of MeBr was then back‐calculated using a two step process: (i) an arbitrary flux value of 100 µg m−2 s−1 was used as an initial input value. Resultant air concentrations predicted by the model were then regressed on air concentrations measured offsite and (ii) the resultant regression coefficient was then used to adjust the arbitrary flux to a back‐calculated flux. Using another regression analysis, back‐calculated and measured flux rates were found to be significantly correlated, indicating this approach may be suitable for indirect estimation of flux. Implications for the use of this method in establishing buffer zones designed to protect human health are discussed.
Methyl Bromide Emissions from a Covered Field: III. Correcting Chamber Flux for Temperature
Authors: Yates S. R. , Gan J. , Ernst F. F. , Wang D. 
Published: July 2010

AbstractAn experiment was conducted to investigate the environmental fate and transport of methyl bromide (MeBr) in agricultural systems. Part of this experiment involved the use of three flow‐through chambers to estimate the MeBr flux through a sheet of clear polyethylene plastic covering the field. Using the chamber data, the total mass lost to the atmosphere was estimated to be 96% of the applied mass, and the results were highly variable between chambers (i.e., standard deviation of 298 kg or 35%). The air temperature inside the chamber was found to be much higher than the air temperature outside and was highly correlated with the diurnal variation in incoming solar radiation. Since the diffusion through polyethylene film was found to be strongly dependent on the temperature, a method was developed to correct the chamber flux density data for enhanced diffusion caused by increases in the temperature inside the chamber. After correcting for temperature, the estimated total MeBr emission was reduced to approximately 59% (21% standard deviation) of the applied amount, which is about 5% less than was measured using other methods. When chambers are used to measure volatilization of MeBr or other fumigants from fields covered with a sheet of polyethylene plastic, the chambers should be designed to minimize internal heating or some method should be used to correct the volatilization rate for the effects of temperature.
A Tracer Test to Determine the Fate of Nitrate in Shallow Groundwater
Authors: Starr J. L. , Sadeghi A. M. , Parkin T. B. , Meisinger J. J. 
Published: July 2010

AbstractThe effectiveness of shallow groundwater areas to serve as a sink for NO3 is affected by many biological and physical properties. However, the direct impact of these properties on the fate of NO3 in shallow groundwater is not well understood, especially where the soils are intermittently saturated. This study was conducted to assess in situ reaction and transport of NO3‐N in an intermittent shallow groundwater system. Tracer experiments were conducted within an imposed constant flowing shallow groundwater. A constant‐head, single injection well technique was adapted for this study using multilevel soil water samplers placed at 14 locations around the center injection well. The use of Br as a tracer for NO3‐N in these constant‐flow experiments provided the means to assess in situ NO3‐N removal both with and without added C. In experiments without added C, an average NO3 removal rate of 0.33 g N m−2 d−1 was estimated. In a second experiment with dextrose added as an added C source, an average NO3 loss rate 1.06 g N m−2 d−1 was observed. The observed response to added dextrose indicates that the N removal processes were primarily microbial in origin, i.e., the NO3 was denitrifled or immobilized into microbial biomass.
Wood and Combination Wood‐Fired Boiler Ash Characterization
Authors: Someshwar Arun V. 
Published: July 2010

AbstractAshes resulting from the combustion of wood residues in industrial boilers are characterized relative to (i) macroelement compositions, (ii) trace and heavy metal microelement compositions, (iii) organics, and (iv) polychlorinated dibenzo‐dioxins and ‐furans (PCDD/Fs). Ash compositions, both macro‐ and microelements, are compared with coal ash and limestone. Microelements in wood ashes are also compared with other potential soil amendments such as pulp mill sludges. The impact of burning sludge and combinations of coal and wood residue on ash metal concentrations is presented. Levels of PCDD/Fs in ash resulting from combustion of 100% inland wood residue, salty wood, or bleached mill sludge with wood residue are reviewed, as are the levels of PCDD/Fs in ashes and soot resulting from residential wood combustion. The concentrations of metals in wood ash are comparable to other potential soil amendments. The concentration in wood ash of common organics of environmental concern appears to be negligible. The levels of PCDD/Fs in the ash appear to have a direct correlation with extraneous sources of chloride in the wood fuel.
Nitrogen Transport from Tallgrass Prairie Watersheds
Authors: Dodds W.K. , Blair J. M. , Henebry G. M. , Koelliker J. K. , Ramundo R. , Tate C. M. 
Published: July 2010

AbstractDischarge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha−1 yr−1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14–0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO−3N and total N (r values = −0.43 and −0.20, respectively). Low N concentration is typical of these streams, with NH+4‐N concentrations below 1.0 µg L−1, NO−3‐N ranging from below 1.4 to 392 µg L−1, and total N from 3.0 to 714 µg L−1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.
Zinc and Cadmium Toxicity to Alfalfa and Its Microsymbiont
Authors: Ibekwe A. M. , Angle J. S. , Chaney R. L. , van Berkum P. 
Published: July 2010

AbstractThe availability of heavy metals in soil depends on their speciation in solution and chemical activities of free metals. To examine the sensitivity of alfalfa (Glycine max L.), its microsymbiont, and the process of N2 fixation to Zn2+ and Cd2+ activities, a growth chamber study was conducted. Nutrient solution was used with the chelator, EGTA, to buffer Zn2+ and Cd2+ activities. The activities of Zn2+ and Cd2+ ranged from pZn2+ = 8.0 to 5.0 and pCd2+ = 10.5 to 8.0 mol L−1. Plants grown in pZn2+ = 5.25 and 5.0; and pCd2+ = 8.75 and 8.65 were stunted and chlorotic with interveinal necrosis. In these treatments, shoot concentrations of Zn and Cd averaged about 300 and 50 mg kg−1, respectively. This resulted in a 20 and 90% yield reduction for plants grown in pZn2+ = 5.25 and 5.0, respectively. Yield reduction was 50 and 75% for pCd2+ = 8.75 and 8.65, respectively. Plants supplied with mineral N had about 40% greater shoot yield than plants inoculated with rhizobia. No nodulation occurred at pZn2+ = 5.0, but at pZn2+ = 5.25 and pCd2+ = 8.75 and 8.65, there was a delay in nodulation. All nodules formed were mostly effective in N2 fixation. Enumeration of viable cells showed a significant decline of total cell counts from 105.5 cell mL−1 in the control to 105.1 and 104.8 at the highest Zn2+ and Cd2+ activities, respectively. At the activities studied, Cd was more toxic to rhizobia than Zn. However, at the highest activities, toxicity of metals were so severe that root development was inhibited and in some cases resulted in plant death. These results suggest that toxicity of Zn and Cd was greater to plants than to rhizobia.
Persistence of Metribuzin and Metabolites in Two Subarctic Soils
Authors: Conn J. S. , Koskinen W. C. , Werdin N. R. , Graham J. S. 
Published: July 2010

AbstractPersistence and leaching of 14C‐metribuzin [4‐amino‐6‐(1,1‐dimethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one] and metabolites were determined in Tanana (loamy, mixed, nonacid Pergelic Cryaquept) and Beales (sandy, mixed Typic Cryochrept) silt loam soils under irrigated potato (Solanum tuberosum L.) and dryland barley (Hordeum vulgare L.) conditions in the subarctic. Overall, dissipation of total 14C (metribuzin and metabolites) was significantly slower (P > 0.05) in Tanana than Beales soil over the first 105 d, but by 468 d, the 14C remaining (51% of applied) did not differ (0.05 < P) between soils. Initial degradation of metribuzin was rapid in both soils but was not significantly different between soils (0.05 < P). At 35 after application 24% of applied metribuzin remained. At the end of the study (468 d), 5.0% of the applied metribuzin was still present. Unextractable residues accounted for the greatest amount of 14C remaining in the soils. Of the extractable metabolites, greater amounts of desaminometribuzin were found in both soils than diketometribuzin or desaminodiketometribuzin. More water moved through the irrigated than nonirrigated soil as evidenced by bromide movement. Also, more 14C moved to 15 to 22.5 cm depth in the irrigated than in the nonirrigated soil, but <1% of applied 14C was detected below 22.5 cm for both soils and irrigation treatments. Rapid metribuzin degradation in combination with sorption processes minimized leaching of total metribuzin residues through these subarctic surface soils.
Transient Diffusion, Adsorption, and Emission of Volatile Organic Vapors in Soils with Fluctuating Low Water Contents
Authors: Petersen L. W. , El‐Farhan Y. H. , Moldrup P. , Rolston D. E. , Yamaguchi T. 
Published: July 2010

AbstractLaboratory experiments were conducted on large packed soil columns (15 cm diam., 40 cm length) under unsaturated conditions. Trichloroethene (TCE) was introduced at the bottom of the columns. The emissions of TCE from the soil surface were monitored. The soil‐water content at the soil surface was changed by alternating dry and water‐saturated air sweeping over the column surface, thus changing the vapor sorption capacity of the soil. The retardation of VOC gas transport, due to the change in adsorption capacity with change in soil‐water content, was determined by sampling the soil‐air and the sweep air flushing the column headspace. Soil‐water content was monitored by the time‐domain reflectometry (TDR) technique. The transport of VOC gases from experiment initiation until steady‐state was simulated using a numerical simulation model, in which diffusion and equilibrium partition theory were incorporated. Measured and simulated concentration profiles as well as volatilization fluxes agreed very well. The decrease in soil‐water content, caused by sweeping dry air over the column surface, resulted in an increase in the soil adsorption capacity up to several orders of magnitude (mainly in the top few centimeters of soil). Both increase and decrease in soil‐water content affected the volatilization flux manifested in large rapid peaks of TCE volatilizing from the surface. This behavior was likewise simulated using a numerical model with changing diffusion coefficients and retardation factors as function of soil‐air content, and good agreement was obtained between model simulations and measured data.
Transport of Anthropogenic Uranium from Sediments to Surface Waters During Episodic Storm Events
Authors: Batson Vicky L. , Bertsch P. M. , Herbert B. E. 
Published: July 2010

AbstractRemobilization of sediment‐associated uranium (U) from contaminated floodplain sediments to a stream adjacent to a nuclear weapons processing facility during episodic rain events was investigated. In addition, U solid phase associations in suspended sediments were assessed by a sequential chemical extraction procedure to gauge U chemical lability. Mass flux estimates determined from base flow measurements potentially underestimate the amount of U transported from contaminated terrestrial sources to surface water systems. Erosional processes can effectively mobilize sediment‐associated contaminants during storms or flooding. During the various storm events measured, approximately 1500 to 2800% more U was exported to Upper Three Runs Creek (UTRC) relative to base flow measurements. Sequential extraction results suggest the suspended sediment load transports the bulk of U in labile forms predominantly as acid soluble (specifically adsorbed), MnO2 occluded and organically bound phases. This implies that U may be available to the ecosystem under a range of environmental conditions likely to be encountered within depositional environments (e.g., Eh and pH) or as a result of industrial processes. This study demonstrates the need to evaluate contaminant transport during storm events from exposed contaminated sediments, or from industrial waste stockpiles subject to erosion.
Cadmium Uptake for Swiss Chard Grown on Composted Sewage Sludge Treated Field Plots: Plateau or Time Bomb?
Authors: Chang A. C. , Page A. L. , Hyun Hae‐nam 
Published: July 2010

AbstractTwo hypotheses have been proposed to describe the phytoavailability of potentially toxic metals in sewage sludge treated soils. The plateau theory argues that the metal adsorption capacity added with sludge will persist as long as the metals of concern persist in the soil and the metals would remain in chemical forms not readily available for plant uptake. Therefore, the metal concentrations of plant tissue will reach a plateau as sewage sludge mass loading increases and remain at this plateau after termination of sludge application. The sludge time bomb hypothesis postulates that a soil's metal adsorption capacity is augmented by soil organic matter added as sewage sludge. This capacity, however, will revert back to its original background level with time following termination of sewage sludge application as mineralization of organic matter releases metals into more soluble forms, thus a time bomb. We employed a set of experimental data obtained from a 10‐yr field‐based sewage sludge land application experiment to evaluate the hypotheses of the plateau and the time bomb. The evaluation involved analysis of Cd concentration of Swiss chard grown on soils that either received sewage sludge application continuously or no longer received sewage sludge application. The results indicate that necessary conditions for plateau and time bomb to take place may be found. But an actual plateau or time bomb was not evident from 10 yr of experimental data in which the sewage sludge application reached 2880 Mg ha−1.
Transport of Bromide under Intermittent and Continuous Ponding Conditions
Authors: Ashraf M. S. , Izadi B. , King B. 
Published: July 2010

AbstractAn understanding of water and chemical transport through the soil is crucial for the development of proper irrigation and nutrient management practices. Because of natural heterogeneity and variability of soils, results often cannot be extrapolated between sites and from laboratory to field. In this study, transport of bromide (Br−) was investigated in a silt loam soil under intermittent and continuous ponding conditions using 10 pairs of stations in a 0.40‐ha field. Each station consisted of a double ring infiltrometer and three solution samplers installed at 30, 60, and 100 cm depths. A 3‐cm pulse of KBr− with an average Br− concentration of 500 ppm was applied to each station. Upon depletion of the pulse, 8 cm of water was ponded in each infiltrometer. For the continuous ponding stations, water was added daily and infiltrated volume was recorded. For each intermittent treatment, the time between subsequent irrigations was equal to the time for complete 8 cm infiltration plus 7 d of redistribution time. Solution samples were collected from all samplers on a daily basis for 3 mo, and analyzed for bromide concentration in the lab. At 30‐cm depth, the mean tracer velocities for intermittent and continuous ponding treatments were larger than piston flow velocities by factors of 2.05 and 1.57, respectively. Solute velocities decreased with depth for both treatments. Nutrient management models based on piston flow velocities may overestimate the mass of available nutrients to plants in the root zone.
Long‐Term Study of Volatile Organic Compound Recovery from Ampulated, Dry, Fortified Soils
Authors: Minnich Marti M. , Zimmerman John H. , Schumacher Brian A. 
Published: July 2010

AbstractOur objective was to evaluate the stability and extractability of volatile organic compounds (VOCs) when fortified on dry soils and stored in sealed ampules. Two desiccator‐dried soils were fortified with eight neat VOCs, benzene, toluene, ethylbenzene, o‐xylene, 1,1,1‐trichloroethane (TCA), trichloroethene (TCE), tetrachloroethene (PCB), and 1,1,2,2‐tetrachloroethane (TTCA) at 800 ng each VOC/g soil. The fortified soil was portioned into ampules, sealed, and stored in the dark at 25°C for up to 56 wk. Replicate ampules were analyzed after 2 d and 2, 4, 8, 13, 34, and 56 wk by two extraction procedures modified from the U.S. Environmental Protection Agency's (USEPA's) low‐ and high‐level purge‐and‐trap procedures (SW‐846 Methods 5030/8021).The modified high‐level procedure (1‐h methanol extraction at 25°C prior to purge‐and‐trap analysis) yielded significantly higher recoveries of all compounds on both soils as compared with the low‐level procedure, with the exception of benzene on the Charleston soil. Moreover, when measured by the high‐level procedure, concentrations of benzene, toluene, ethylbenzene, and o‐xylene (BTEX) remained relatively unchanged during the 56‐wk study. The results indicate that the 1‐h, 25°C methanol extraction was sufficient for extraction of the BTEX compounds from these soils. For the chlorinated compounds, regression analysis demonstrated significant trends of changing concentrations over time. Recoveries of TCA decreased at a rate of 3 and 4 ng/g/week and recoveries of TTCA decreased at rates of 8 and 17 ng/g/week on the Hayesville and Charleston soils, respectively. PCE concentrations did not show any significant concentration changes, while TCE concentrations increased at 6 and 7 ng/g/week for the Hayesville and Charleston soils, respectively. We submit that the 1‐h, 25°C methanol extraction was inadequate for removal of the chlorinated compounds. Additionally, we postulate that dehydrochlorination of TTCA to form TCE occurred in desiccator‐dried soil.
Herbicide Persistence and Mobility in Recharge Lake Watershed in York, Nebraska
Authors: Ma L. , Spalding R. F. 
Published: July 2010

AbstractElevated levels of herbicides in surface and groundwater are a concern in the Cornbelt in the USA. This study was conducted to interpret the herbicide behavior in a watershed system using data collected from runoff, Recharge Lake, and groundwater influenced by agriculture and lake seepage. The York Ground Water Recharge Project was constructed on a tributary of Beaver Creek, which drains a 3327‐ha watershed of primarily row‐cropped heavily irrigated farmland. The estimated average runoff is 1.48 × 106 m3 yr−1 under a precipitation norm of 635 mm yr−1. Maximum atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) inputs to Recharge Lake occurred in May and June runoff events and resulted in average lake concentrations of 36 and 17 µg L−1 in 1993 and 1994, respectively. Only about 0.28 and 0.19% of total applied atrazine was lost to runoff in 1993 and 1994, respectively. The deethylatrazine (DEA) to atrazine molar ratio (DAR) decreased rapidly over a period of several hours in runoff samples, which is consistent with inputs from recently atrazine‐treated soil. After the spring runoff, herbicide levels in Recharge Lake rose rapidly in response to the runoff event, then diminished gradually over a period of months. Atrazine concentrations in Recharge Lake decreased exponentially with time. Degradation half‐lives were 237 d (r = 0.93) in 1993 and 209 d (r = 0.91) in 1994. Adjusted DEA concentrations in Recharge Lake remained relatively constant, indicating little evidence for biotic degradation and suggesting that abiotic degradation of atrazine to hydroxyatrazine (2‐hydroxy‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) was the most likely major degradative pathway in Recharge Lake.