bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field‐Scale Nitrogen and Phosphorus Losses from Hayfields Receiving Fresh and Composted Broiler Litter
Authors: Vervoort R. W. , Radcliffe D. E. , Cabrera M. L. , Latimore M. 
Published: July 2010

AbstractComposting broiler litter may increase the amount of stable organic components and reduce contamination of ground‐ and surface‐water with N and P from excessive land applications. Limited research has been done comparing field‐scale losses of nutrients from broiler litter applied to hayfields. This project determined field‐scale N and P runoff losses from fresh and composted litter applied to hayfields. Two rates of broiler litter, 10 Mg ha−1 yr−1 (1X) and 20 Mg ha−1 yr−1 (2X), and a mix of 10 Mg ha−1 yr−1 of broiler litter and 50 Mg ha−1 yr−1 of composted litter (1X + C), were split‐applied in April and September for 2 yr. Surface runoff and subsurface flow were monitored for inorganic and total N and P. Nitrate concentrations in subsurface flow remained below the USEPA standard of 10 mg L−1 for all treatments. Average dissolved reactive P (DRP) concentrations were statistically higher under the 1X + C treatment, followed by the 2X and 1X treatments, reaching a maximum of 8.5 mg L−1 under the 1X + C treatment. Differences between field and plot‐scale results were most likely controlled by the timing of application and occurrence of the first rainfall event. Concentrations of resin‐extractable P (Pr) in soil increased under all treatments, indicating accumulation of P after only 2.5 yr of application. In this research, the amount of P applied was the principal determinant of the DRP concentration in the surface runoff. Composting broiler litter increased the amount of stable organic components.
Distribution of Trace Elements in Soil from Repeated Sewage Sludge Applications
Authors: Berti W. R. , Jacobs L. W. 
Published: July 2010

AbstractWe studied the horizontal and vertical distribution in a soil profile (Metea sandy loam; loamy, mixed, mesic Typic Hapludalf) of trace elements as a result of their loading at phytotoxic levels to cropland. Municipal sludges containing high concentrations of Cd, Cr, Cu, Pb, Ni, and Zn were applied to cropland from 1977 to 1986 at three rates plus an untreated control. Total elemental analysis of soils collected in 1989 and 1990 indicated that lateral distribution of trace elements had occurred. This lateral distribution was most likely a result of the physical movement of soil particles with agronomic operations. The elements, however, were not distributed below the sampling depth of from 15 to 30 cm. Mass balance calculations resulted in average trace element recoveries that ranged from 45 to 155% of the total applied. These calculations were highly variable, indicative of the highly variable nature of sludge composition, lack of total uniform sludge applications, soil movement due to tillage operations, and sampling methods. Because of the potential errors associated in mass balance calculations, recoveries that have been calculated in this and other studies that deviate substantially from 100% should reasonably be expected. Direct examination of the relatively few ways in which trace elements are lost from a soil (i.e., plant uptake, soil movement via tillage, water and wind erosion, and deep leaching) may be more meaningful than mass balance calculations to determine the fate of trace elements applied to soil.
Reduction of Selenite to Elemental Selenium by Enterobacter cloacae SLD1a‐1
Authors: Dungan R. S. , Frankenberger W. T. 
Published: July 2010

AbstractThe facultative anaerobic bacterium Enterobacter cloacae strain SLD1a‐1 (ATCC‐700258) was studied in washed cell suspensions to assess optimal conditions required for the reduction of selenite (SeO32−) to elemental selenium (Se0). Enterobacter cloacae using glucose (1.4 mM) as an electron donor removed 79% of the added SeO32−(7.9 mM) from solution in 2.5 h. Optimal SeO32− reduction occurred at a pH of 6.5 and a temperature of 40°C. Carbohydrate sources arabinose, xylose, and sorbose were found to significantly enhance SeO32− reduction over that of glucose. The reduction of SeO32− at 7.9 mM was inhibited by nitrate at levels 1 to 100 times greater, nitrite at levels 5 and 10 times greater, while sulfite at levels of two to four times greater was found to stimulate the reduction of SeO32−. Enterobacter cloacae grows on anaerobically incubated plates containing NO3− as the sole terminal electron acceptor and acetate as the electron donor. Use of SeO32− as the terminal electron acceptor during anaerobic respiration did not support growth and could only be reduced to Se0 when NO3− was present.
Sorption, Degradation, and Mineralization of Carbaryl in Soils, for Single‐Pesticide and Multiple‐Pesticide Systems
Authors: Nkedi‐Kizza P. , Brown K. D. 
Published: July 2010

AbstractSorption, degradation, and mineralization of carbaryl (1‐naphthyl N‐methylcarbamate) alone and in mixtures with atrazine(2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and diuron (N′‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea) were characterized for two topsoils and their respective subsoils. In general, differences in sorption and transformation between single and multiple‐pesticide systems were less than differences due to soil type and between topsoil and subsoil. For a given soil, the topsoil containing more organic carbon (OC) than the subsoil exhibited a larger value for the Freundlich sorption coefficient (Kt). Similarly, a larger value for the soil solution degradation rate coefficient (k1) was obtained from topsoil than subsoil, likely due to greater microbial activity in the topsoil. However, for all soils, sorption of carbaryl on soils considerably increased the magnitude of the degradation half‐life (t1/2) for carbaryl in either single‐pesticide or multiple‐pesticide systems. In soils that contained <10 g kg−1 OC content, the effect of multiple‐pesticide systems was to enhance the mineralization of carbaryl. This was attributed to cometabolism. This study shows that carbaryl chemodynamic parameters (Koc and t1/2 values) can be used to adequately analyze the fate of carbaryl in the environment even when carbaryl exists in a mixture with atrazine and diuron.
River‐Groundwater Exchanges, Bank Filtration, and Groundwater Quality: Ammonium Behavior
Authors: Doussan C. , Ledoux E. , Detay M. 
Published: July 2010

AbstractIn many countries, bank‐filtrated water is an important component of the drinking water production. In this case, most of the water pumped from the alluvial aquifers originates from the adjacent river. Bank‐filtration is generally considered beneficial both quantitatively and qualitatively. However, in some cases bank filtration can cause deleterious effects to groundwater quality. This paper describes such a case, focusing on ammonium (NH4) concentrations. The data were gathered at an experimental bank‐filtration site which is part of a large well field along the Seine River (France). At this site, groundwater was sampled along a flow line path and pore water of river bed sediments was collected with peepers or by centrifuging core samples. The pore waters of the superficial river bed sediments have high ammonium concentrations (>30 mg NH4 L−1) whereas, in the groundwater, these concentrations are lower (≤20 mg NH4 L−1), with higher concentrations near the bank. The high NH4 concentration in the sediment is related to the heavy organic load in the river and the mineralization of this organic matter by benthic microflora. Among the different mechanisms that influence NH4 transport and retention in the porous medium, it emerges that sorption by the alluvial sediments (Kd = 1 − 10 × 10−3 m3 kg−1), or even the chalk (Kd = 48 × 10−3 m3 kg−1) seems to be effective in retaining NH4. This is illustrated by a model of NH4 transfer with retardation adapted to the conditions of the site. Precipitation of NH4 salts is probably not involved in regulating NH4 concentrafion at this site.
Phosphorus Flux between Sediment and Overlying Water in Lake Okeechobee, Florida: Spatial and Temporal Variations
Authors: Moore P. A. , Reddy K. R. , Fisher M. M. 
Published: July 2010

AbstractTotal P is increasing over time in the waters of Lake Okeechobee, Florida, but the concentrations do not correlate with external loads. The objectives of this study were to determine: (i) the P flux from various sediment types within the lake, (ii) the factors that control direction and magnitude of P flux, and (iii) the amount of P associated with various inorganic P phases within the sediment. Phosphorus flux was measured from intact sediment cores taken from eight sites that represent major sediment types and major inflows of Lake Okeechobee at four time periods in 1989–1990. At the same location‐times, dissolved reactive phosphorus (DRP) in porewater was determined using porewater equilibrators and/or sediment cores. Results indicate that P flux from sediments is very sensitive to changes in O2 status of the overlying water, with anaerobic conditions promoting large P fluxes. Despite steep porewater DRP gradients in sediments (varying from 0.1 mg P L−1 at the sediment/water interface to more than 1 mg P L−1 at lower depths), P flux was not regulated by such gradients. Such lack of dependence of P flux on DRP gradients highlights the role redox reactions (involving Fe) can play in P chemistry in the top few centimeters of the sediment. Internal P loads (i.e., flux from bottom sediments) were found to be approximately equivalent to external P loads (≈1 mg P m−2 d−1).
The Fate and Transport of Viruses through Surface Water Constructed Wetlands
Authors: Chendorain Michael , Yates Marylynn , Villegas Frank 
Published: July 2010

AbstractColiphage removal efficiency and the effects of wetland hydrology on virus transport were determined for constructed wetlands in San Jacinto, CA. Mathematical models were used to further characterize virus transport. MS2, an F‐specific RNA (FRNA) coliphage was used as a model for human enteric viral behavior. Two wetland types were studied, a one‐phase cell and three‐phase cell. These wetlands received unchlorinated secondary effluent at a constant rate. The mean residence time in the wetlands was 9 ± 3 d as determined using bromide as a conservative tracer. Assuming 100% porosity, a plug flow model predicts this mean residence time within the experimental standard deviation (8 d). This suggests that a negligible volume was occupied by vegetation and settled solids. The convection‐dispersion equation adequately simulated the residence time distribution of the conservative tracer. MS2 removal in the wetlands was experimentally determined to be 97 ± 3%. There was no distinction between the two wetland types in terms of removal efficiency. The average coliphage decay rate was calculated to be 0.44 per day. However, the error involved with using the first order decay rate was high, 83 ± 12%. Therefore, first order decay does not adequately describe removal processes within the wetland. Most virus removal occurred within the first 3 m (k = 4.0 ± 1.8 d−1) with a removal efficiency of 85.3 ± 0.6%. The remainder had a decay rate of 0.20 ± 0.17 d−1 with a removal efficiency of 56 ± 33%.
Electromagnetic Survey of Cornfield with Repeated Manure Applications
Authors: Eigenberg R. A. , Nienaber J. A. 
Published: July 2010

AbstractWaste management sites are subject to nutrient buildup from storage, treatment, and repeated application of manure. Methods are needed to quickly assess a site or field location to survey nutrient levels and estimate risk potential. Electromagnetic (EM) conductivity methods have been shown to be sensitive to areas of high nutrient levels (Eigenberg et al., 1996) and offer promise to provide field assessments. In this report, high density electromagnetic field mapping is described as a method to isolate and detect areas of nutrient buildup in a cornfield receiving waste management research treatments. Various manure and compost rates have been applied to this research field for replacement of commercial fertilizer with the treatment assignments remaining identical over a 4‐yr period. Electromagnetic conductivity measurements were able to differentiate (P < 0.0001) the N check treatment (commercial application rate) vs. manure applied at the recommended P rate, compost applied at the P rate, and compost applied at the N rate. The N check treatment and the manure applied at the N rate treatment resulted in nearly identical mean values for EM readings and were not statistically distinguishable. Analysis of soil cores (NO3, Cl, P, K, SO4, NH4, Na, electrical conductivity, and soil moisture content) randomly located within each treatment were compared to EM readings at the same locations. The Pearson correlation coefficients revealed strong (P = 0.02 or better) correlations for all constituents except NH4 (P = 0.308). Treatment effects were significant (P < 0.05) for all soil constituents except NH4 and water content.
Responses of Soil Respiration to Clipping and Grazing in a Tallgrass Prairie
Authors: Bremer Dale J. , Ham Jay M. , Owensby Clenton E. , Knapp Alan K. 
Published: July 2010

AbstractSoil‐surface CO2 flux (Fs) is an important component in prairie C budgets. Although grazing is common in grasslands, its effects on Fs have not been well documented. Three clipping treatments: (i) early‐season clipping (EC); (ii) full‐season clipping (FC); and (iii) no clipping (NC); which represented two grazing strategies and a control, were applied to plots in a tallgrass prairie in northeastern Kansas, USA. Measurements of Fs were made with a portable gas‐exchange system at weekly to monthly intervals for 1 yr. Concurrent measurements of soil temperature and volumetric soil water content at 0.1 m were obtained with dual‐probe heat‐capacity sensors. Measurements of Fs also were obtained in grazed pastures. Fs ranged annually from 8.8 × 10−3 mg m−2 S−1 during the winter to 0.51 mg m−2 s−1 during the summer, following the patterns of soil temperature and canopy growth and phenology. Clipping typically reduced Fs 21 to 49% by the second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual Fs were 4.94, 4.04, and 4.11 kg m−2 yr−1 in NC, EC, and FC treatments, respectively; thus, dipping reduced annual Fs by 17.5%. Differences in Fs between EC and FC were minimal, suggesting that different grazing strategies had little additional impact on annual Fs. Daily Fs in grazed pastures was 20 to 37% less than Fs in ungrazed pastures. Results suggest that grazing moderates Fs during the growing season by reducing canopy photosynthesis and slowing translocation of carbon to the rhizosphere.
Incorporating Temperature Effects on Pesticide Degradation into a Management Model
Authors: Wu Jinquan , Nofziger D. L. 
Published: July 2010

AbstractThe impact of agrochemicals on groundwater quality has been the subject of considerable research and public debate. Mathematical models often are used to predict the fate of these chemicals and to develop regulations. In this research, we modified the pesticide degradation component of a management model to estimate soil temperature with depth and time and to incorporate the effect of temperature variation on the pesticide degradation rate. Estimated pesticide mass leaching beyond a depth of 1 m was two or more orders of magnitude greater when the temperature effect was incorporated into the model. Predicted soil temperatures at four different depths using measured surface soil temperatures followed the seasonal temperature variation of observed data with an average deviation <0.3°C. Among the input parameters analyzed, the amount of pesticide leached was most sensitive to uncertainties in activation energy of a degradation reaction, reference half‐life, and annual mean soil temperature. Uncertainty in annual change in surface soil temperature had a moderate impact on the simulated amount of pesticide leached. Uncertainties in damping depth and time lag of annual minimum temperature had little effect. Uncertainties in model parameters can result in differences on the order of one‐ to fourfold in simulation output. Although these are large, they are clearly much less than the differences of 2 to 8 orders of magnitude, which can occur if temperature effect is ignored. We conclude that models used for pesticide risk assessment should incorporate temperature effects on degradation. The algorithm presented here can be incorporated readily into many leaching models.
Charge Properties and Nitrate Adsorption of Some Acid Southeastern Soils
Authors: Eick Matthew J. , Brady Warren D. , Lynch Colleen K. 
Published: July 2010

AbstractNumerous studies have been conducted examining nitrate (NO3) leaching losses from agricultural land. Simulation models have been developed that allow one to predict the potential of NO3 to leach to groundwater. However, many of these models treat NO3 as a conservative tracer and do not evaluate surface chemistry. This study evaluated the surface charge properties and NO3 adsorption capacity of four acid southeastern subsoils. Significant anion exchange capacity and NO3 retention was found for two of the soils. Point of zero net charge (PZNC) was determined using an ion exchange method. Values of 3.1 and 3.6 were determined for two of the soils while PZNC values were not quantifiable for the other two soils in the pH range of 3 to 7. Nitrate adsorption isotherms were measured on untreated and chloride‐saturated soils. Nitrate adsorption maxima determined from the linearized form of the Langmuir equation ranged from 1.40 to 2.13 cmolc kg−1. Coefficients of determination (R2) and adsorption maxima increased after chloride saturation. This was attributed to competition from anions such as sulfate, fluoride, and phosphate. Net positive charge and NO3 retention were found to depend on the type and quantity of both variable and permanent charged minerals present in the soil and the composition of the exchange complex. These results demonstrated that acid subsoils high in variable charge minerals may have the potential to retard NO3 movement to groundwater. Therefore, simulation models may need to account for NO3 adsorption when modeling NO3 movement in acid soils dominated by variable charge minerals.
Effects of Precipitation and Air Temperature on Phosphorus Fluxes from Rhode River Watersheds
Authors: Correll David L. , Jordan Thomas E. , Weller Donald E. 
Published: July 2010

AbstractWe studied fluxes of total P, total phosphate, and total organic P from seven contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 25 yr. These watersheds have perched aquifers so all groundwater discharges as well as surface runoff were measured at V‐notch weirs equipped with volume‐integrating, flow‐proportional samplers. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160‐yr weather records in the region. Annual total‐P area yields from the overall watershed varied 28‐fold, correlations of all P‐species fluxes with precipitation were highly significant, and power function regressions of precipitation vs. P‐flux explained from 42 to 55% of the variance in the latter. Phosphorus fluxes from a cropland watershed were much higher and more variable with volume of precipitation, while fluxes from a forested watershed were much lower and primarily composed of organic P. Correlations of P fluxes with precipitation were higher in the spring. Annual and seasonal P concentrations also often increased significantly with precipitation. Variations in seasonal mean air temperature sometimes explained significant amounts of variance in P fluxes, especially phosphate from cropland. A regression model was used to construct graphical and tabular summaries.
Efficiency of a Subsurface Constructed Wetland System Using Native Southwestern U.S. Plants
Authors: Maschinski Joyce , Southam Gordon , Hines Jeff , Strohmeyer Scott 
Published: July 2010

AbstractA small‐scale three‐cell (in series) subsurface (SSF) constructed wetland that used 16 previously untested native Arizona plants was found to be effective in the treatment of secondary waste at high elevation (2350 m) in northern Arizona. Fifteen of the 16 plant species survived in at least one of the cells in the system. Plant survival depended on their position in the cells, with increased survival rates downstream from the effluent input to cell 1, on water depth, and on individual species selection. The wetland was effective in removing both chemical pollutants (total Kjeldahl nitrogen [TKN], ammonia, nitrate, total kjeldahl phosphorus [TP], and phosphate) and bacteriological indicator organisms of human pathogens (total coliforms and fecal coliforms). The fecal coliform counts of the effluent exiting the third cell were below the recreational full‐body contact (swimming) standard (200 cfu/100 mL) in 14 out of the 15 mo of operation. The TKN and TP concentrations were reduced by 84 and 73%, respectively compared to nutrients entering the system. The loss of N suggests that a combined nitrification/denitrification process is active in the wetland. However, after 9 mo of operation, nitrate levels began to increase beyond the target of 1 mg/L indicating that nitrification rates are exceeding denitrification rates and that the wetland cells are aerobic. The constructed wetland system effectively conserves water. Because it is used to irrigate plantings near the constructed wetland, the nutrient concentrations in the effluent aid plant growth.
Denitrification as a Sink for Dissolved Nitrous Oxide in a Freshwater Riparian Fen
Authors: Blicher‐Mathiesen Gitte , Hoffmann Carl Chr. 
Published: July 2010

AbstractDenitrification as a sink of dissolved nitrous oxide (N2O) was investigated in a freshwater riparian fen. In a 15‐m transect extending from the hillslope and into the fen the groundwater concentrations of nitrate (NO−3) declined from 1.8 mM NO−3 (25 mg L−1) to less than 0.01 mM NO−3, dissolved oxygen (O2) and nitrous oxide (N2O) declined from approximately 110 µM O2 (3.5 mg O2 L−1) and 4.0 µM N2O‐N (56 µg N L−1), respectively, to zero and the dissolved N2 concentration increased by 589 µM N2‐N (8.2 mg N L−1). The NO−3 reduction was 0.42 µM cm−3 d−1 or 7.71 µM cm−2 d−1 in sediment columns with continuous upward groundwater flow through the sediment. Concomitant with NO−3 reduction, N2O was produced at a rate of 54.4 nM N2O‐N cm−2 d−1 in this same 18‐cm narrow sediment zone. However, the N2O produced was subsequently reduced at the same rate closer to the sediment surface. In 15NO−3 experiments on chloramphenicol‐treated anaerobic sediment slurries, the denitrifying enzyme activity (DEA) was estimated to be 118 ± 16.7 nmol N (N2‐N + N2O‐N) g fresh weight 1−1 d−1, of which 36% accumulated as N2O. Thus, in this permanently water‐covered riparian fen, denitrification served as a sink for both the dissolved N2O in groundwater recharging the fen and the N2O produced within the riparian sediment.