bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Radionuclide Transport and Uptake in an Integrated Lysimeter Experiment: II. Application to Sodium‐22
Authors: Butler A. P. , Wheater H. S. 
Published: July 2010

AbstractA conceptual model of an integrated system of lysimeters is used to investigate the behavior of 22Na in soils and plants. The application of the model requires three stages of calibration relating to water fluxes, soil sorption, and root uptake. The water fluxes are calibrated against water level changes in a storage reservoir common to eight lysimeters used to support a winter wheat (Triticum aestivum L. cv. Pastiche) crop. The reservoir is part of a control system, which maintains a fixed water table in each of the lysimeters, thereby supplying contaminated water to the wheat crop. Measurements of total 22Na in soil are four orders of magnitude greater than in the harvested crop. This allows the equilibrium soil sorption coefficient, Kd, to be identified separately from a root uptake coefficient, α′, which characterizes the uptake of 22Na per unit area of root. The model was able to successfully simulate the time‐dependent behavior of 22Na concentrations in the various components of the water table control system, the lysimeter soil profiles, and the harvested crop. In particular, crop uptakes spanning nearly three orders of magnitude over five crop seasons were reproduced reasonably well. The model, therefore, represents a more physically realistic approach to soil‐to‐plant transfer from contaminated water tables than the traditional method of transfer factors. It also shows, for mobile radionuclides, the importance of characterizing correctly the soil water fluxes when using such an approach.
Denitrification Rates in a Wastewater‐Irrigated Forest Soil in New Zealand
Authors: Barton L. , McLay C. D. A. , Schipper L. A. , Smith C. T. 
Published: July 2010

AbstractDenitrification is considered to be an important N removal process in land‐based wastewater treatment systems, although in situ denitrification rates have rarely been reported. We investigated the contribution of denitrification to N removal in a land treatment system by measuring in situ denitrification rates for 12 mo in a Monterey pine (Pinus radiata D. Don) forest irrigated with tertiary‐treated wastewater. The variability of denitrification rates was investigated using a nested field design that divided the land treatment system into four spatial components (irrigation block, topographic position, field site, and sample plot) and two temporal components (sample period, sample day). Denitrification was measured using undisturbed soil cores collected daily, for six consecutive days on 21 occasions throughout the year. Soil moisture content, NO3 concentration, available C, denitrifying enzyme activity, and temperature also were measured. The annual denitrification rate in the irrigated soil was 2.4 kg N ha−1 yr−1, and only slightly higher than the unirrigated soil (1.7 kg N ha−1 yr−1). Temporal effects (i.e., seasonal and day‐to‐day variation) contributed more than spatial effects to the overall variation in denitrification rates. Multiple regression analysis showed that soil factors could only explain 29% of the variation in denitrification rates. Soil water‐filled porosity was low in the land treatment system, and less than the critical threshold value (74% water‐filled porosity) determined in a laboratory study. We concluded that denitrification in this land treatment system studied was limited by excessive aeration in the free‐draining soils.
Processes Governing Phosphorus Availability in Temperate Soils
Authors: Frossard E. , Condron L. M. , Oberson A. , Sinaj S. , Fardeau J. C. 
Published: July 2010

AbstractPhosphorus losses from agricultural soil to water bodies are mainly related to the excessive accumulation of available P in soil as a result of long‐term inputs of fertilizer P. Since P is a nonrenewable resource, there is a need to develop agricultural systems based on maximum P use efficiency with minimal adverse environmental impacts. This requires detailed understanding of the processes that govern the availability of P in soil, and this paper reviews recent advances in this field. The first part of the review is dedicated to the understanding of processes governing inorganic P release from the solid phase to the soil solution and its measurement using two dynamic approaches: isotope exchange kinetics and desorption of inorganic P with an infinite sink. The second part deals with biologically driven processes. Improved understanding of the abiotic and biotic processes involved in P cycling and availability will be useful in the development of effective strategies to reduce P losses from agricultural soils, which will include matching crop needs with soil P release and the development of appropriate remediation techniques to reduce P availability in high P status soils.
Site‐Specific Considerations for Managing Phosphorus
Authors: Schepers J. S. , Schlemmer M. R. , Ferguson R. B. 
Published: July 2010

AbstractNutrient management can be difficult for land receiving nonuniform and sometimes very large applications of animal manure. The objective of this research was to document spatial variability in soil P status and develop a management strategy to help producers avoid problems related to past manure management practices. A 60‐ha center‐pivot sprinkler irrigated cornfield was intensively sampled (12.2 by 24.4 m alternate grid) and analyzed for Bray‐1 P. The average Bray‐1 P concentration showed that only a maintenance application would be sufficient; however, 74% of the individual data points indicated a positive response to P fertilizer could be expected. A map revealed unusually high soil P concentrations around a previous farmstead. Other spatial patterns were related to depositional areas with relatively high organic matter content. Consultants are beginning to collect soil samples on a 100 by 100 m grid (1.0‐ha cells). The study field was separated into 1.0‐ha cells from which P availability maps were generated using data from a single point in the center of each hypothetical cell and compared to the map using data from the cell corners. These maps were similar in some respects but would result in considerably different variable‐rate P application maps. Results document the limitations and potential fallacies associated with grid sampling. A more reasonable approach might be to use a bare‐soil photograph, crop canopy image, or yield map to identify sampling areas with similar characteristics to define sampling zones. Every effort should be made to identify past manure history prior to soil sampling.
Phosphorus Management at the Watershed Scale: A Modification of the Phosphorus Index
Authors: Gburek William J. , Sharpley Andrew N. , Heathwaite Louise , Folmar Gordon J. 
Published: July 2010

AbstractWe considered hydrologic and chemical factors controlling P export from a 39.5‐ha mixed land use watershed in east‐central Pennsylvania, focusing our evaluation on watershed vulnerability to P loss. The spatial variations of P source factors, soil P, and P inputs from fertilizer and manure were evaluated. Distribution of Mehlich‐3 soil P on a 30‐m grid over the watershed showed that soil P varied with land use. Soils in wooded areas had low Mehlich‐3 P (<30 mg kg−1); grazed pasture had Mehlich‐3 P values between 100 and 200 mg kg−1; and cropped fields receiving manure and fertilizer applications were mostly >200 mg kg−1. Phosphorus sources and transport controls on P loss were evaluated by examining in‐stream P concentrations during storm hydrographs. Phosphorus concentrations decreased 50% downstream from headwaters to watershed outlet, and were more closely related to near‐stream (within 60 m) distribution of high‐P soils than to that of the whole watershed. This suggests that near‐stream surface runoff and soil P are controlling P export from the watershed. Based on these findings, we modified the Phosphorus Index (PI), a user‐oriented tool developed by the NRCS‐USDA to identify critical source areas controlling P export from agricultural watersheds. The modification separately evaluates P source and transport factors, and incorporates the hydrologic return period to describe contributing areas. The modified PI was applied to the watershed to illustrate interactions between P source and transport processes controlling P export, and approaches for managing P loss.
Controlling Soil Water Erosion and Phosphorus Losses from Arable Land in England and Wales
Authors: Chambers B. J. , Garwood T. W. D. , Unwin R. J. 
Published: July 2010

AbstractSoil water erosion and P losses were monitored annually in 13 erosion susceptible arable catchments (ca. 80 fields) in England and Wales between 1989 and 1994. Erosion was recorded in 38% of the 385 fields monitored, with ca. 80% of the erosion events occurring on land cropped to winter cereals. Three main factors were associated with the erosion events: poor crop cover (<15%), presence of valley floor features that concentrated surface runoff, and compacted tramlines/wheelings. The rainfall events causing erosion were generally greater than 15 mm/day (90% of cases), with maximum intensities >4 mm/h (94% of cases). Mean annual soil losses were 17 Mg/ha (median 0.48 Mg/ha). Annual edge‐of‐field P losses via soil (rill and gully) erosion from arable land were estimated at ca. 2300 Mg, equivalent to approximately 18% of estimated P losses from agricultural land in England and Wales. A number of erosion control techniques also were tested. The use of minimum (or noninversion) tillage techniques that leave straw on the soil surface were effective in reducing erosion, although there were some practical problems with crop establishment. Avoiding fine rolled seedbeds minimized slaking and capping at the soil surface, helping to maintain water infiltration rates and reduce runoff. Where winter cereals were grown, early drilling encouraged crop cover development during the autumn period, protecting the soil from the erosive impact of rainfall. To avoid wheeling compaction, tramlines were best set up after winter cereal crops had emerged and any trafficking delayed or avoided in the autumn.
A Conceptual Approach for Integrating Phosphorus and Nitrogen Management at Watershed Scales
Authors: Heathwaite Louise , Sharpley Andrew , Gburek William 
Published: July 2010

AbstractSince the late 1960s, point‐sources of water pollution have been reduced due to their ease of identification and treatment. As water quality problems remain and further point‐source measures become less cost‐effective, attention is directed toward reducing agricultural nonpoint‐sources of P and N. In the past, separate strategies for P and N were developed and implemented at farm or watershed scales. Because of differing biology, chemistry, and flow pathways of P and N in soil, these narrowly targeted strategies may lead to mixed results. In some cases, N management of manures has increased soil P and subsequent P enrichment of surface runoff, while no‐till has reduced P losses but increased nitrate leaching. Thus, an integrated approach to nutrient management is needed, with best management practices (BMPs) targeted to critical areas of a watershed that contribute most of the P and N exported. We have developed indices that identify critical sources and transport pathways controlling P and N export. These indices are applied to a mixed land use watershed in Pennsylvania. Areas most vulnerable to P loss are limited to small, well‐defined areas of the watershed (<20% of area) near the stream channel. In contrast to P, larger areas contribute to nitrate leaching and generally occur on the upper boundaries of the watershed (60%), where freely draining soils and high manure and fertilizer N applications are made. Thus, differing levels of nutrient management may be appropriate for different areas of a watershed.
Leaching Behavior of Various Trace Metals in Aqueous Medium from Two Fly Ash Samples
Authors: Kanungo S. B. , Mohapatra R. 
Published: July 2010

AbstractBy using the batch, continuous, and column leaching methods, an attempt has been made to study the behavior of various metal ions release in water from two fly ash samples collected from two thermal power plants in Orissa, India. The USEPA extraction procedure has been followed to determine the early release of several hazardous elements, and it has been observed that their concentrations are within the prescribed limits for both the fly ash samples. Batch leaching at different pH values shows that trace metal ions release decreases sharply with increase of pH from 3.0 to 8.0. Continuous leaching at the liquid/solid ratio of 20:1 shows that both the samples are mildly acidic in nature with pH value stabilizing at 5.4 to 5.9. This is because of the high Fe and low Ca contents in the samples, where the pH value is controlled by the cyclic release and Fe and Al hydrolysis. An attempt has been made to correlate percentage of decrease in metal ions concentration with those of constants of the formation of different hydrolytic species, namely MeOH+ and Me(OH)2 with increase in pH of the medium. A comparison between repeated leaching in columns using a low liquid/solid ratio and continuous leaching at a high liquid/solid ratio indicates that the general trend of dissolution of metals is essentially similar for both the methods.
Comparison of Three Nonparametric Kriging Methods for Delineating Heavy‐Metal Contaminated Soils
Authors: Juang Kai‐Wei , Lee Dar‐Yuan 
Published: July 2010

AbstractThe probability of pollutant concentrations greater than a cutoff value is useful for delineating hazardous areas in contaminated soils. It is essential for risk assessment and reclamation. In this study, three nonparametric kriging methods [indicator kriging, probability kriging, and kriging with the cumulative distribution function (CDF) of order statistics (CDF kriging)] were used to estimate the probability of heavy‐metal concentrations lower than a cutoff value. In terms of methodology, the probability kriging estimator and CDF kriging estimator take into account the information of the order relation, which is not considered in indicator kriging. Since probability kriging has been shown to be better than indicator kriging for delineating contaminated soils, the performance of CDF kriging, which we propose, was compared with that of probability kriging in this study. A data set of soil Cd and Pb concentrations obtained from a 10‐ha heavy‐metal contaminated site in Taoyuan, Taiwan, was used. The results demonstrated that the probability kriging and CDF kriging estimations were more accurate than the indicator kriging estimation. On the other hand, because the probability kriging was based on the cokriging estimator, some unreliable estimates occurred in the probability kriging estimation. This indicated that probability kriging was not as robust as CDF kriging. Therefore, CDF kriging is more suitable than probability kriging for estimating the probability of heavy‐metal concentrations lower than a cutoff value.
Transformation of Chlorinated Phenols and Anilines in the Presence of Humic Acid
Authors: Park Jong‐Woo , Dec Jerzy , Kim Jang‐Eok , Bollag Jean‐Marc 
Published: July 2010

AbstractIncubations of chlorinated phenols and anilines with oxidoreductive catalysts (peroxidase, laccase, tyrosinase, and birnessite) in the presence of humic acid led to oligomerization of the substrates or their binding to organic matter. The effect of humic acid on the overall transformation depended on the substrate, type of catalyst, and the concentration and source of humic acid. At low humic acid concentrations (<10 mg/L), the transformation of 4‐chlorophenol (4‐CP) was enhanced, but at higher concentrations of humic acid (>10 mM), no further enhancement occurred. The transformation of 4‐chloroaniline (4‐CA) was only slightly affected after the addition of humic acid. In experiments with 14C‐labeled substrates, 4‐CP was mainly bound to humic acid and formed few oligomers, whereas 4‐CA was largely subject to oligomerization with less binding to humic acid. Binding and oligomerization of 4‐CP did not change with increasing concentration of humic acid, but with 4‐CA, binding increased and oligomerization decreased. It appears that nucleophilic binding of 4‐CA depended largely on the availability of carbonyl and quinone groups in humic acid and, therefore, the distribution of the transformed substrate between oligomers and organic matter greatly depended on the source of humic acid.
Soil Fluxes of Carbon Dioxide, Nitrous Oxide, and Methane at a Productive Temperate Deciduous Forest
Authors: Bowden R. D. , Rullo G. , Stevens G. R. , Steudler P. A. 
Published: July 2010

AbstractWe measured CO2, N2O, and CH4 fluxes between soils and the atmosphere in ambient and N‐addition plots at a productive black cherry‐sugar maple forest in northwest Pennsylvania to examine the link between N‐cycling and trace gas fluxes. Fluxes were estimated the using in‐situ chambers. Net annual N mineralization was 121.0 kg N ha−1yr−1, and net nitrification was 85.8 kg N ha−1 yr−1, or 71% of net mineralization. Carbon dioxide (5.09 Mg C ha−1 yr−1) efflux and CH4 uptake (8.90 kg C ha−1 yr−1) were among the highest rates reported for temperate deciduous forests. Emissions of N2O (0.228 kg N ha−1 yr−1) were within the range of rates reported elsewhere, including locations with lower rates of N‐cycling. A short‐term study (May–Oct.) showed that N fertilization reduced both CO2 emissions and CH4 uptake (CO2 by 19%; CH4 by 24%). N2O effluxes in fertilized plots were not different from control plots. The relatively high rate of soil respiration corresponded to a high rate of N‐cycling; however, N2O emissions were not substantially greater than those measured at other locations, suggesting that rapid N‐cycling or N additions in temperate forests do not necessarily result in large emissions of N2O. Concurrent rapid rates of N‐cycling and high rates of CH4 uptake did not support the hypothesis that N‐cycling rates directly control CH4 uptake. Links between N‐cycling and CH4 oxidation are complex; the influence of N‐cycling on flux rates must consider not only the rate of cycling, but also the disposition of N‐cycling products, and the factors that influence rates of N dynamics.
Landfill Methane Oxidation Response to Vegetation, Fertilization, and Liming
Authors: Hilger Helene A. , Wollum Arthur G. , Barlaz Morton A. 
Published: July 2010

AbstractThis study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH4 oxidation. Columns filled with compacted sandy loam and sparged with synthetic landfill gas were used to simulate a landfill cover. Grass‐topped and bare‐soil columns reduced inlet CH4 by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady slate. Nitrate and NH4 amendments induced a more rapid onset of CH4 oxidation relative to KCl controls. However, at steady state, NH4 inhibited CH4 oxidation in bare columns but not in grassed columns. Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH4 oxidation. In all treatments, CH4 consumption increased to a peak value, then declined to a lower steady‐state value; and all gassed columns developed a pH gradient. Neither nutrient depletion nor protozoan grazing could explain the decline from peak oxidation levels. Ammonium applied to grassed cover soil can cause transient reductions in CH4 uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH4 inhibition indicates that results from bare‐soil tests may not always generalize to vegetated landfill caps.
Bioaerosol Transport Modeling and Risk Assessment in Relation to Biosolid Placement
Authors: Dowd Scot E. , Gerba Charles P. , Pepper Ian L. , Pillai Suresh D. 
Published: July 2010

AbstractA field study was performed in which bioaerosols were sampled at a field site undergoing land placement of anaerobically digested, de‐watered biosolid material. The data from these field studies were then used to generate microbial release rates from the biosolids for use in modeling bioaerosol transport. Continuous‐point sources represented by large biosolid piles (temporary storage before placement) in the field, and continuous‐area sources represented by large fields upon which biosolids were placed by spraying, were modeled using microbial transport models; and downwind microbial concentrations were generated. These quantified transport data were then entered into microbial dose‐response models in an attempt to characterize the risk of pathogenic bacteria and viruses infecting workers and nearby population centers. The risk of viral and bacterial infection to workers at biosolid land application sites is 3:100 and 2:100, respectively, under 2‐m/s wind conditions and 1 hr of exposure. The route of exposure proposed in this model is the transport, inhalation, deposition, and swallowing of bacterial or viral pathogens. Note that these risk models by nature would tend to overestimate the actual risk to populations (wastewater workers) consisting primarily of immunocompetent individuals. Under these low‐wind conditions, nearby population centers where such immunocompetent populations may exist (here considered to be 10 000 m from the land application sites) are predicted to be at little risk (1.95 × 10−:100) of infection from aerosolized bacteria and at no risk from aerosolized viruses.
Soil Solution Chemistry of a Fly Ash‐, Poultry Litter‐, and Sewage Sludge‐Amended Soil
Authors: Jackson B. P. , Miller W. P. 
Published: July 2010

AbstractMixing coal fly ash (FA) with organic wastes to provide balanced soil amendments offers a potential viable use of this industrial by‐product. When such materials are land‐applied to supply nutrients for agronomic crops, trace element contaminant solubility must be evaluated. In this study, major and trace element soil solution concentrations arising from application of fly ash, organic wastes, and mixtures of the two were compared in a laboratory incubation. Two fly ashes, broiler poultry litter (PL), municipal sewage sludge (SS), and mixtures of FA with either PL or SS were mixed with a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult) at rates of 32.3, 8.1, and 16.1 g kg−1 soil for FA, PL, and SS, respectively. Treatments were incubated at 22°C at 17% moisture content and soil solution was periodically extracted by centrifugation over 33 d. Initial soil solution concentrations of As, Mo, Se, and Cu were significantly greater in FA/PL treatments than the respective FA‐only treatments. For Cu, increased solution concentrations were attributable to increased loading rates in FA/PL mixtures. Solution Cu concentrations were strongly correlated with dissolved C (R2 > 0.96) in all PL treatments. Significant interactive effects for solution Mo and Se concentrations were observed for the FA/PL and may have resulted from the increased pH and competing anion concentrations of these treatments. Solution As concentrations showed a significant interactive effect for one FA/PL mixture. For the individual treatments, As was more soluble in the PL treatment than either FA treatment. Except for soluble Se from one FA/SS mixture, trace element solubility in the FA/SS mixtures was not significantly different than the respective FA‐only treatment.