bluuebunny/crossref_metadata_2025 huggingface dataset:
Sorption‐Desorption and Solution Concentration of Phosphorus in a Fertilized Sandy Soil
Authors: He Z. L. , Alva A. K. , Li Y. C. , Calvert D. V. , Banks D. J.
Published: July 2010

There has been increasing concern about drinking water contamination and accelerated eutrophication of surface water bodies. A field experiment was conducted to assess leaching potential of PO4‐P in a Riviera fine sand (loamy, siliceous, hyperthermic Arenic Glossaqualf) under grapefruit (Citrus paradisi Macfad.) production that received 0 to 30 kg P ha−1 yr−1. The PO4‐P concentration was measured in soil solution sampled using suction lysimeters installed above (120 cm) and below (180 cm) the hardpan (argillic horizon). Phosphorus sorption‐desorption in soil samples from different depths of the soil profile was determined to understand the transport and leaching of P in the sandy soil. Phosphorus sorption capacity of the argillic horizon was much greater than the soil above and below it. The PO4‐P concentrations in soil solution varied from 0.031 to 0.976 and from 0.002 to 0.083 mg P L−1 at the 120‐ and 180‐cm depths, respectively. Solution PO4‐P concentrations generally increased with P application rates. The concentrations of P in solution at the 120‐cm depth were much greater than those at the 180‐cm depths, due to the greater P retention capacity of and restricted flow of P through the hardpan. This study demonstrates that leaching of P into groundwater was reduced by the presence of a hardpan in the Riviera fine sand. However, the water drained from the soil above the hardpan contains phosphorus and could be a potential P source to surface waters.
Soil Nitrate‐Nitrogen under Tomato following Tillage, Cover Cropping, and Nitrogen Fertilization
Authors: Sainju Upendra M. , Singh Bharat P. , Rahman Syed , Reddy V. R.
Published: July 2010

Management practices can influence NO3‐N content and movement in the soil. We examined the influence of 3 yr of tillage [no‐till (NT), chisel (CH), and moldboard (MB)], cover crop [hairy vetch (Vicia villosa Roth) (HV), and no hairy vetch (NHV)], and N fertilization (0, 90, and 180 kg N ha−1) on residual NO3‐N content and movement on a Norfolk sandy loam (fine‐loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill) in central Georgia. Because of low N recovery by tomato, NO3‐N content in the soil increased with depth, regardless of treatments, and ranged from 127 to 316 kg ha−1 at 0‐ to 120‐cm depth in the fall (September 1997). The content increased with increasing rate of N addition from cover crop residue and N fertilizer. From fall to spring (March 1998), 22 to 58% (37 to 129 kg NO3‐N ha−1) of this content was lost, mostly due to leaching. Greater loss occurred in NT than in CH or MB, with HV than with NHV, and with 180 or 90 than with 0 kg N ha−1. Similarly, greater loss at 0‐ to 60‐cm than at 60‐ to 120‐cm depth and significant correlation between soil NO3‐N and clay concentration with depth indicates that NO3‐N moved from the surface layer to the underlying clay layer, where it moved slowly. Nitrate‐N content and movement in the soil from cover crop residue and N fertilizer were similar. Minimum tillage reduced NO3‐N movement compared with NT, yet avoided the negative effects on soil and water quality associated with MB. Although HV increased tomato N uptake and recovery, it was not effective in reducing NO3‐N content and movement compared with N fertilizer.
Calibration of Paired Basins prior to Streambank Fencing of Pasture Land
Authors: Galeone Daniel G.
Published: July 2010

Streambank fencing is a best management practice that is targeted to reduce suspended sediment and nutrient inputs to streams by reducing direct inputs from animals, eliminating streambank trampling, and promoting streambank revegetalion. A paired basin study is being conducted in two small adjacent basins to determine the waler quality effects of streambank fencing. This article documents the 3‐yr calibration period between control and treatment basins prior to fence installation. Approximately 70% of land adjacent to streambanks in the study area is used as pasture. Nutrient quantities applied as manure, benthic‐macroinvertebrate communities, and the physical habitat of each stream were similar in both basins. Total N, P, and suspended sediment yields measured at the outlet of each basin averaged about 56, 2.8, and 2650 kg ha−1 on an annual basis. For both basins, about 90% of the total N yield was attributable to dissolved NO3‐N and about 90% of the total N yield occurred during nonstormflow; conversely, about 90% of the total P yield was attributable to stormflow and 60 to 65% of the total P yield was suspended. Regression equations developed between both basins for low flow and stormflow samples for nutrients, suspended sediment, and discharge indicated a significant relation for most constituents. Pretreatment relation between basins for low flow and stormflow samples would need to change by 6 and 14% for total N concentrations and 24 and 9% for total P concentrations in order for streambank fencing to significantly affect water quality in the treatment basin.
Trend Analysis of Nutrient Concentrations and Loads in Surface Water in an Intensively Fertilized Watershed
Authors: Bouraoui Fayçal , Turpin Nadine , Boerlen Pascal
Published: July 2010

Nutrient concentrations and loads from 1988 to 1997 at the surface‐water outlet of a heavily fertilized watershed in the Brittany region, west of France, were analyzed for trends. The 1240‐ha watershed is characterized by milk production and an increasing indoor pig and poultry production. A nonparametric statistical analysis performed on mean monthly and mean annual data detected no trend in nitrate and total P concentrations and loads from 1988 to 1997. When comparing data from the same month for each year of the study, a decreasing trend was detected in the November nitrate flow adjusted concentrations, and in the October maximum nitrate flow adjusted concentrations. An increasing trend was detected in the August total P flow adjusted concentrations. No trend was detected in the monthly and annual nitrate and total P loads. A multiple regression analysis showed that the annual nitrate concentration is positively correlated to the annual rainfall and to the percent area of corn (Zea mays L.). A nutrient global mass balance was constructed for 1988, 1991, and 1994 to explain the lack of an increasing trend in nutrient concentrations and loads despite an intensification of the pig production during these years. Results from this analysis showed that farmers have compensated for increased on‐farm production of nutrients from animal manure by purchasing less fertilizers; therefore, the total nutrient budget remained relatively stable.
Metamodeling Potential Nitrate Water Pollution in the Central United States
Authors: Wu JunJie , Babcock Bruce A.
Published: July 2010

This article presents a modeling system for identifying the spatial patterns of potential water pollution from N fertilizer use in the central USA. The model uses a geographic information system (GIS) and a statistical technique to integrate an environmental process simulation model with spatially referenced databases on crop management and resource characteristics. The potential for NO3‐N runoff and leaching was estimated for a total of 128 591 sites using information on soil, climate, crop, rotation, tillage, irrigation, and conservation practices at each site. For the entire study region, the average annual NO3‐N runoff and leaching, respectively, were estimated to be 5 and 3 kg ha−1, which accounted for about 7 and 4% of total N applied. The potential for NO3‐N runoff was relatively high in much of the Corn Belt, Kansas, and the Nebraska Platte River Basin, and the potential for NO3‐N leaching was relatively high in Ohio, Indiana, and southern Illinois and Missouri. Because much of the area with high leaching potential was tile drained, a large portion of the leached NO3‐N will be discharged to surface water, rather than continue downward to ground water. Finally, the model was applied to estimate the effects of a 25% reduction in N application rates and adoption of crop rotations on potential NO3‐N runoff and leaching.
Modeling Radionuclide Transport and Uptake in an Integrated Lysimeter Experiment: I. Model Development
Authors: Butler A. P. , Wheater H. S.
Published: July 2010

A model of a set of integrated lysimeters used to study radionuclide transport and uptake in vegetated soils is described. The experimental facility is conceptualized as a network of linked compartments. Observed water fluxes provide the basis for simulating the movement and distribution of radionuclides throughout the entire experimental system. The model incorporates a simplified representation of upward migration of radionuclides into an unsaturated soil followed by leaching. The transfer of radionuclides from the soil to the crop is represented using a dynamic root uptake submodel. The application of the lysimeter system model to data for the radionuclide 22Na is presented in an accompanying paper.
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

A 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

Denitrification 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

Phosphorus 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

Nutrient 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

We 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

Soil 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

Since 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

By 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

The 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

Incubations 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

We 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

This 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

A 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

Mixing 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.
A Wind Tunnel for Measuring Selenium Volatilization under Field‐Like Conditions
Authors: Dungan R. S. , Stork A. , Frankenberger W. T.
Published: July 2010

A wind tunnel was developed to measure the loss of volatile selenium (Se) from soil under field‐like conditions. The wind tunnel consisted of a volatilization chamber made of Plexiglas (2.4 m long × 0.8 m wide × 1.2 m high), which was set above a stainless steel lysimeter (0.5 m2 surface area × 0.8 m deep). High air exchange rates (avg. 700 air changes h−1) were used to simulate field‐like environmental conditions inside the wind tunnel. To monitor the fate and transport of the Se, radiolabeled 75Se as sodium selenite (Na275SeO3) was incorporated into the top 5 cm of soil. Volatile Sc was trapped on activated carbon filters and measured directly using gamma counting. A 135‐d bare‐soil experiment was carried out, during which 2.7% of the Se was released through volatilization without added C. The average flux rate of gaseous Se was 17 mg m−2 h−1, with a high of 72 mg m−2 h−1 occurring on Day 6. After 135 d, 59 and 34% of the 75Se was located in the 0 to 5 and 5 to 10 cm soil layers, respectively. A total of 84.5% of all applied 75Se was recovered. The purpose of this study was to improve estimates on Se volatilization from seleniferous soils and help close the gap between previous laboratory and field experiments.
Anthropogenic Inputs of Nitrogen and Phosphorus and Riverine Export for Illinois, USA
Authors: David Mark B. , Gentry Lowell E.
Published: July 2010

Agricultural nonpoint sources are important contributors of N and P to surface waters. We determined N and P net anthropogenic inputs for Illinois, examining changes during the last 50 yr and linkages to surface water export of N and P. Inputs (fertilizer, atmospheric deposition, and N2 fixation) were compared to exports (grain export, after accounting for animal and human consumption, plus animal product export) from 1945 through 1998 using state‐reported data on fertilizer sales, crop production, and human and animal populations. Large inputs of N were found beginning about 1965, coinciding with increased N fertilizer applications (about 800 000 Mg N yr−1). The N input (about 400 000 Mg N yr−1) was 8.6 million Mg N for the 1979 to 1996 crop years, with a corresponding riverine flux of 4.4 million Mg N (51% of net anthropogenic inputs discharged by rivers). Using literature estimates of field and in‐stream denitrification, we could account for nearly all of the missing N in a mass balance. For P, a different paflern was found for state net anthropogenic inputs with a large input from 1965 to 1990, and on average no net inputs since 1990. For rivers, we estimated that 16% of the total N load and 47% of the total P load was from sewage effluent. We estimate that Illinois contributed 15 and 10% of the annual total N and P loads of the Mississippi River, respectively, and that any reduction strategy in Illinois must address agricultural sources.
Effect of Mineral Colloids on Virus Transport through Saturated Sand Columns
Authors: Jin Yan , Pratt Ellen , Yates Marylynn V.
Published: July 2010

Studies have indicated that colloids are capable of adsorbing and enhancing the transport of a variety of contaminants in soil, fractured rocks, and ground water. The purpose of this study was to determine the role of mineral colloids on the fate and transport of viruses through porous media. Experiments were conducted to examine the influence of several mineral colloids [kaolinite, Ca‐montmorillonite (Ca‐M), and Na‐montmorillonite (Na‐M)] on the movement of a bacteriophage (MS2) through sand columns under saturated flow conditions. Input solution containing MS2 and Br− tracer was applied to the column as a pulse function while colloids were introduced as a step function. Effluent samples were collected in a fraction collector and analyzed for Br−, virus, and colloids. The convection‐dispersion equation (CDE), partially calibrated with the transport parameters measured from the Br− signal, was used to evaluate the transport characteristics of both the virus and colloids. Transport of both the colloids and MS2 through sand columns was described well by the CDE when a first‐order kinetic removal process was assumed. The bacteriophage MS2 was adsorbed by colloids to various degrees and in the order of fine Na‐M > coarse Na‐M > Ca‐M ∼ kaolinite. The amount of colloids transported through the columns followed the same order. The Na‐M greatly enhanced MS2 transport through the sand columns and the effect was more significant when the clay particles were ground into smaller sizes. The extent of colloid‐facilitated MS2 transport was clearly correlated with the extent of colloid transport and the number of viruses adsorbed to colloidal particles. To our knowledge, this study demonstrates for the first time the possible effect of colloids in facilitating virus transport through porous media.
A Multiplexed Fiber Optic Miniprobe System for Measuring Solute Transport in Soil
Authors: Ghodrati Masoud , Garrido Fernando , Campbell Chris G. , Chendorain Michael
Published: July 2010

A fiber optic miniprobe (FOMP) system has been recently developed, capable of measuring solute breakthrough curves (BTCs) in situ and in real time at a single point within the soil matrix. We have multiplexed this system to allow continuous operation of up to 20 of these FOMPs simultaneously. The system was used to measure replicated multipoint BTCs of a fluorescent tracer in a large silica sand column, and allowed verification of the multiplexed FOMP system's ability to measure transport at a point scale. We performed seven miscible displacement studies (runs) generating 140 BTCs to examine system performance, transport variability measured at a small scale, and the sensitivity of that variability to changes in initial pulse concentration (Co). The convective‐dispersive equation (CDE) was adequate to describe transport in the silica sand (r2 > 0.96). However, tails observed in all the BTCs were attributed to an immobile phase by fitting several BTCs to a resident concentration form of the mobile‐immobile model (MIM). The mass recovery of the tracer ranged from 73 to 127% with an average of 98%. Changes in column averaged transport parameters for the seven miscible displacement studies were minimal; however, there appears to be no consistency in transport at the measurement scale of the probes. Small changes in Co were not found to significantly alter or change the variability in transport parameters. The multiplexed fiber optic system was found to be an accurate tool for small‐scale characterization of solute transport in soil.
Biodegradation of Fuel Oil Hydrocarbons in the Rhizosphere of Maize
Authors: Chaîneau C. H. , Morel J. L. , Oudot J.
Published: July 2010

Plant roots provide suitable habitats for the growth of microorganisms. Particularly, the release of exudates by living roots enhances the microbial activity in the rhizosphereo This work was undertaken in the laboratory to study the biodegradation of fuel oil hydrocarbons (HC) in the presence of growing plants and to assess the effects of root exudates on biodegradation. Maize (Zea mays L.) plants were grown in soil microcosms for 120 d and in liquid (hydroponic) cultures for 40 d in presence and in absence of fuel oil added at slightly phytotoxic concentrations (soil: 3300 mg kg−1; hydroponic cultures: 850 mg L−1). Controls without plants permitted the quantification of the rhizosphere effects on HC removal. Concentration and chemical composition of residual HC were periodically determined. Higher degradation rates of saturated and aromatic HC were observed in soil in the presence of plants in the early stages of biodegradation when maize growth was exponential. No significant change was observed in the polar fraction. After 120 d, the biodegradation rates were identical in the presence or absence of plants. In hydroponic conditions, a stimulation in the degradation of saturates was observed until Day 40. No significant difference was detected in the aromatic fraction. The faster biodegradation of HC in the presence of plants was attributed to the changes in environmental conditions in the rhizosphere; e.g., increase of HC bioavailability, stimulation of bacterial populations due to plant exudation and effects on physical properties of soil. Competition for mineral nutrients between plants and microorganisms was shown.
Nitrogen Retention and Release in Atlantic White Cedar Wetlands
Authors: Zhu Wei‐Xing , Ehrenfeld Joan G.
Published: July 2010

The fate of N inputs to freshwater wetlands from enriched runoff, ground water, or atmospheric deposition reflects a variety of processes that determine the net retention of N or its release to downstream ecosystems. The history of N enrichment may affect the relative importance of different pathways. We compared the ability of sediments from Atlantic cedar wetlands in suburban and undisturbed watersheds to remove added inorganic N in laboratory incubations. Three pulses of NH4NO3, at 50 mg N L−1 concentration, were added at consecutive 2‐wk intervals as an analog of pulsed stormwater inputs. After each incubation, soils were leached with CaCl2 and inorganic N concentrations in the leachate were analyzed. The peats retained added N during the first incubation, but after the second and third, all soils released more N than had been added. Nitrate concentrations were always lower than ammonium concentrations. Soils from hollows and most hummocks retained added nitrate throughout the study, but all soils released ammonium. Soil extractable ammonium increased four to 10 times after the 6‐wk incubation, while extractable dissolved organic N (DON) decreased. There also was a net decrease of soil total Kjeldahl N (TKN). The patterns of retention and release of nitrate and ammonium were correlated positively with the N mineralization and nitrification rates of the soils. Our results suggest that wetland peats in suburban drainages may have limited ability to retain frequent, pulsed N inputs from runoff and high intrinsic N mineralization in N‐saturated sediments can become a cause of water quality degradation.
Nitrous and Nitrogen Oxide Emissions from Turfgrass Receiving Different Forms of Nitrogen Fertilizer
Authors: Maggiotto S. R. , Webb J. A. , Wagner‐Riddle C. , Thurtell G. W.
Published: July 2010

The use of N fertilizer in agriculture is considered an important source of atmospheric N2O and NOx. Choice of fertilizer type and management has been considered a method for mitigating these emissions. Micrometeorological methods were used to study the effect of inorganic N fertilizers urea (U), slow‐release urea (SRU), and ammonium nitrate (AN) on fluxes of N2O, NO, and NO2 from turfgrass field plots during three seasons, from 1995 to 1997 (total of 353 d of measurement). Daily average fluxes after fertilizations reached a maximum of 2091 ng N2O‐N m−2 s−1 after the first fertilization with AN in 1996. The fertilized plots had significantly higher emissions (P < 0.05) than the control plot, and the highest N2O emissions were from AN in 1995 and 1996, and from SRU in 1997. Daily fluxes of up to 186 ng NO‐N m−2 s−1 were measured within 1 wk following fertilization in 1997. The U plot had significantly higher NO emissions during all seasons compared with other fertilized plots. Fluxes of NOx during 1996 and 1997 were consistently downward, indicating that turfgrass was acting as a sink for NOx. NO2 uptake seemed to be directly related to NO emissions, and the U plot presented the highest NO2 uptake. Urea‐based fertilizers seem to minimize N2O emissions, although long‐term effects of SRU still need to be studied. The higher NO emissions from U‐based fertilized plots do not seem to be a problem, since NOx uptake occurred at higher rates than NO emission.
Two‐Dimensional Model Simulation of 1,3‐Dichloropropene Volatilization and Transport in a Field Soil
Authors: Wang D. , Knuteson J. A. , Yates S. R.
Published: July 2010

A modeling study was conducted to simulate 1,3‐dichloropropene (1,3‐D) emission and concentration distribution in soil profiles when the chemical was applied with subsurface drip irrigation with reduced rate. The purpose was to evaluate the effect on emission reduction as compared with conventional shank injection application. To compare with field measurements, simulated scenarios included a shallow drip application at 2.5 cm, covered with a polyethylene film; a deep drip application at 20.3 em with bare soil surface; and a conventional shank injection at 30.5 cm with a regular application rate. A convective and diffusive two‐dimensional model was used to simulate the simultaneous transport of 1,3‐D in both liquid and gaseous phases. Diurnal variations of soil temperature were predicted to calculate 1,3‐D diffusion coefficient and the Henry's constant. Predicted 1,3‐D emissions compared well with field measurements for the shallow and deep drip irrigation treatments. The model simulation underpredicted 1,3‐D emission in the shank injection plot, where other transport mechanisms such as gas phase convection likely occurred during and immediately after application. Results from the modeling study indicate that computer simulation can be used effectively to study the environmental fate and transport of 1,3‐D under conditions where vapor phase diffusion and liquid phase convection are the dominant transport mechanisms. Applying 1,3‐D with subsurface drip irrigation appeared to be useful for emission reduction.
Column System for Concurrent Assessment of Emission Potential and Pest Control of Soil Fumigants
Authors: Gan J. , Hutchinson C. , Ernst F. F. , Becker J. O. , Yates S. R.
Published: July 2010

Fumigation for soilborne pest and pathogen control is under close scrutiny because of its potential hazardous effects on the environment and on human health. Therefore, reduced‐risk yet effective fumigation practices are imperatively needed. We have developed a column system that allows an integrated evaluation of emission potential and efficacy of fumigants. The system consists of a large, packed soil column and a sampling chamber for measuring fumigant emissions at the soil surface. Nematodes (or other pests) can be inoculated into the column and their survival may be assayed after the treatment. This approach was used to evaluate the emission of 1,3‐dichloropropene (1,3‐D) and its efficacy against the citrus nematode Tylenchulus semipenetrans when ammonium thiosulfate, a 1,3‐D degrading fertilizer, was applied at the soil surface. Results closely comparable to field observations were obtained. Compared with field studies, the proposed method is rapid and inexpensive, and thus may be used for screening fumigation practices that have improved environmental safety and pest control performance.