bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistence of Carbofuran and Molinate in Flooded Rice Culture
Authors: Johnson W. G. , Lavy T. L.
Published: July 2010

Field studies were conducted on silt loam and silty clay soils to determine the persistence of carbofuran (2,3‐dihydro‐2,2‐dimethyl benzofuran‐7‐yl methylcarbamate) and molinate (S‐ethyl hexahydro‐1H‐azepine‐1‐carbothioate) in the soil and water associated with rice (Oryza sativa L.) production in Arkansas. Paddy‐rice plots were established with earthen levees surrounding each plot and standard cultural practices were followed concerning rice production. Granular formulations of these pesticides were applied 4 d following establishment of the permanent flood at the tillering stage of rice growth. Samples of water and soil were taken at various intervals until 49 days after application (DAA) and analyzed with gas chromatography. Carbofuran was not detected in paddy water after 28 DAA. By 21 DAA, >90% of the applied molinate had dissipated, but detectable levels (0.0012 mg L−1) of residues remained in paddy water through 49 DAA. Both pesticides dissipated rapidly from paddy soil for approximately the first 14 DAA, probably due to solubilization of the granules into the overlying paddy water. Both pesticides had estimated time required for dissipation of 50% of the initial concentration (DT50s) of 10 d in paddy water and paddy soil. Molinate dissipation from paddy soil slowed dramatically after the initial rapid phase. The carbofuran metabolite 3‐keto carbofuran (2,3‐dihydro‐2,2‐dimethyl‐3‐ketobenzofuranyl‐N‐methyl carbamate) was not detected in any water samples, but was detected in 6% of the soil samples. The metabolite 3‐hydroxy carbofuran (2,3‐dihydro‐2,2‐dimethyl‐3‐hydroxy‐benzofuranyl‐N‐methyl carbamate) was detected in 2% of the water samples and 7% of the soil samples. In both cases the concentrations found were slightly above the lower limits of detectability (0.005 mg L−1 for water and 0.01 mg kg−1 for soil).
Persistence of Triclopyr and 2,4‐D in Flooded and Nonflooded Soils
Authors: Johnson W. G. , Lavy T. L. , Gbur E. E.
Published: July 2010

Field studies were conducted on silt loam and silty clay soils to determine the persistence of triclopyr ([(3,5,6‐trichloro‐2‐pyridinyl) oxy] acetic acid) and 2,4‐D (2,4‐dichlorophenoxy acetic acid) in the soil and water associated with rice (oryza sativa L.) production in Arkansas. Liquid formulations of these herbicides were applied postemergence to (i) paddy rice, (ii) rainfed lowland rice, and (iii) bare ground. Samples of soil and water were taken at various intervals until 49 days after application (DAA) and analyzed by gas chromatography. Dissipation of both herbicides was rapid with initial dissipation of 50% of the initial concentration, DT50s, in paddy water, dryland‐rice soil, and bareground soil being 10 d or less. Neither herbicide was detected in water later than 28 DAA. Both herbicides were slightly more persistent in soil than in water. 2,4‐D was slightly more mobile in the soil of all three cultural systems.
Physical and Chemical Characteristics of Selected U.S. Municipal Solid Waste Composts
Authors: He Xin‐Tao , Logan Terry J. , Traina Samuel J.
Published: July 2010

Municipal solid waste (MSW) composting has been increasingly recognized as a promising alternative for solid waste management. Because of the variation in both geographic origin (thus feed stock) and composting technology, the properties of MSW composts generated in various regions are likely to be different. In this study, 10 composts were collected from different facilities throughout the USA. Elemental composition and some physical properties were determined. Trace elements and organic C were partitioned into water soluble, exchangeable, complexed, organically bound, mineral particulate, and residue forms based on sequential extraction with H2O, 1 M KCl, 0.1 M Na4P2O7, 0.1 M NaOH, and 4 M HNO3, respectively. Substantial variabilities were observed in both chemical and physical properties among the MSW composts generated in different facilities. Our results indicate that the trace element contents of MSW composts are in general lower than the average trace elements reported for sewage sludges, and below the pollutant concentrations (PC) for sewage sludges regulated by USEPA. The exception is for Pb, which was higher in some of the MSW composts than the average Pb content in sewage sludges and exceeds the PC. Solid particulate was the dominant form of Cd, Mn, Cu, and Pb, but the majority of Zn was organically complexed. Both solid particulate and residue were dominant forms of compost Cr and Ni. The differences in distribution patterns of trace elements in the MSW composts studied indicate that these elements will vary in their potential mobility and bioavailability in the environment.
Phosphate Removal by Peat from Peat Mining Drainage Water during Overland Flow Wetland Treatment
Authors: Heikkinen Kaisa , Ihme Raimo , Osma Anna‐Mari , Hartikainen Helinä
Published: July 2010

Overland flow technique, which involves conducting wastewater across a natural mire, has during the recent years been widely used in Finland to decrease the loading of P and other elements from peat mining areas to the watercourses. In this study the applicability of laboratory tests in estimating the P retention by overland flow areas was assessed at a site in northern Finland. The ability of peat to retain PO4‐P was determined by adsorption isotherms, and the data were compared with the actual decreases in P loads obtained in the field. The PO4‐P retention curves obeyed rather well the conventional adsorption models, which suggests that sorption can be an important mechanism removing PO4‐P from the peat mining drainage water during overflow treatment. The Freundlich equation gave a better fit to the P sorption than did the one‐surface Langmuir model. The constants describing the sorption characteristics of the peat showed spatial and temporal variation. They indicated, however, that the theoretical effective P sorption time for the overland flow area can be 20 to 25 yr. The ability of peat to retain P increased with increasing concentrations of oxalate extractable Fe and Al. Sorption reactions were found to be important in the annual decreases in PO4‐P from drainage waters in an overland flow area, but their efficiency in removing P from the peat mining drainage water appears to depend on hydrological conditions. In the first experimental year, the sorption calculated from the isotherm data amounted to 60% of the retention obtained in the field. Owing to the high flow conditions in the second year, the decrease in the loading of P in the field was decisively lower than estimated.
An Alkaline Oxidation Method for Determination of Total Arsenic and Selenium in Sewage Sludges
Authors: Zhu Baojin , Tabatabai M. A.
Published: July 2010

A simple and precise method was developed for determination of total As and Se in sewage sludges by using hydride‐generation atomic absorption spectrometry (HGAAS). It involves boiling a 50‐mg sample with sodium hypobromite (NaOBr) solution to dryness in a sand bath (260–280°C), extraction of the As and Se in the digest with 1.25 M H2SO4, and determination of these elements by HGAAS after reducing As(V) and Se(VI) to As(III) and Se(IV), respectively. The proposed method gives quantitative recovery of As and Se in standard reference materials (96–103%) and of these elements added to sewage sludges (95–100%). The average results of As (9.8 mg/kg) and Se (7.5 mg/kg) in 12 sewage sludges determined by the proposed digestion method agreed closely with those obtained by the acid digestion methods recommended by USGS and USEPA. Tests with 13 metals indicated that, at the concentrations expected in sewage sludges, none of the metals interfered with determination of As and Se by the proposed method. A single operator can complete analysis of one of the elements in 40 samples in a normal working day, or both elements in 1.5 d.
Plant Growth Inhibition by Soluble Salts in Sewage Sludge‐Amended Mine Spoils
Authors: Rodgers Cassandra S. , Anderson Roger C.
Published: July 2010

The growth response of prairie switchgrass (Panicum virgatum L.) was compared in strip mine spoil amended with various levels of anaerobically digested waste‐activated sewage sludge (0, 56, 111, 222, or 333 dry Mg ha−1) and commercial fertilizer, pure sludge, and glasshouse soil. Plants were grown in a growth chamber and substrates were maintained at field capacity during the study. Soluble salt concentrations of the substrates increased linearly as a function of sludge amendment and were within the range known to inhibit the growth of many plant species at the high levels of sludge application. There was, however, a linear response of biomass production to increasing levels of sludge amendment. Maintaining substrates at field capacity apparently prevented the high concentration of soluble salts from inhibiting plant growth. The increased biomass yield associated with sludge application was likely due to the increased availability of inorganic nutrients associated with sludge amendment.
Competitive Surface Complexation Reactions of Sulfate and Natural Organic Carbon on Soil
Authors: Kooner Z. S. , Jardine P. M. , Feldman S.
Published: July 2010

The ecological implications of subsurface SO2−4 loading on nutrient cation leaching, acidification, and the destruction of concrete containers used to store low‐level radioactive waste, has been thoroughly addressed. Processes favoring SO2−4 adsorption by the subsurface matrix tend to alleviate these adverse ecological conditions and this has been investigated to a lesser extent. In this study, the adsorption of SO2−4onto several soil types with indigenous SO2−4 and organic carbon removed, was measured as a function of pH in the presence and absence of added natural organic matter (NOM). Sulfate adsorption was strongly pH dependent and the presence of >2 mg L−1 NOM resulted in a consistent decrease in sulfate adsorption over the pH range 4.5 to 8. The tendency of these soils to adsorb SO2−4 was related to their large quantity of Fe‐oxides and the presence of kaolinite in the <2‐µm clay fraction. A surface complexation model based on electrical double layer theory was used to model the adsorption behavior of sulfate. A single reaction involving the adsorption of SO2−4 onto positive or neutral surface sites (XOH + H+ + SO2−4 = XSO−4 + H2O) as an inner‐sphere complex proved successful in describing the adsorption of sulfate under the experimental conditions. The estimated value of the intrinsic equilibrium constant (K) for the above reaction was of the order 1010 suggesting strong sulfate adsorption. Estimated K values were found to be unaffected by the presence of added NOM. The spatial consistency and lack of NOM effects on the intrinsic equilibrium constants for SO2−4 adsorption is convenient for nutrient and contaminant transport modeling at the field‐scale.
Downstream Changes in Free Carbon Dioxide in an Upland Catchment from Northeastern Scotland
Authors: Dawson J. J. C. , Hope D. , Cresser M. S. , Billett M. F.
Published: July 2010

Significant losses of free carbon dioxide (CO2) to the atmosphere are likely to occur when soil‐water, supersaturated with free CO2, enters streams and equilibrates with atmospheric CO2. Spatial changes in dissolved free CO2 downstream from the river source should therefore demonstrate progressive equilibration with atmospheric CO2.

Data on the spatial and diurnal variation in the concentration of dissolved free CO2 are described for a small headwater stream draining an acidic heather [Calluna vulgaris (L.) Hull] moorland catchment in northeastern Scotland. The degree to which free CO2 exceeded the concentration expected for atmospheric equilibration decreased rapidly downstream, from an excess partial pressure (epCO2) of >10 at the source of the stream to ca. 1.5 over a distance of 2 km downstream, suggesting that free CO2 was being lost from the water by outgassing as the water equilibrated with atmospheric CO2. Diurnal variation of ±1.0 CO2 units was also measured at the lowest point in the stream, with levels of CO2 being highest during the early morning and late evening (measurements were not taken during times of darkness) and lowest in the period from late morning to midafternoon. An estimate of the flux of C as free CO2 suggests that it comprises ca. 10% of the combined fluxes of dissolved organic carbon (DOC) and particulate organic carbon (POC). These results suggest that outgassing from and transport within river systems of soil‐derived CO2 forms an important component of the C flux from terrestrial ecosystems back to the atmosphere or to the ocean.
Dilution of Nonpoint‐Source Nitrate in Groundwater
Authors: Altman Susan J. , Parizek Richard R.
Published: July 2010

Nonpoint‐source pollution from agriculture can cause the degradation of groundwater and surface water. Some studies conducted in Coastal Plain aquifers have shown NO−3 removal from groundwater due to assimilation by vegetation or denitrification before discharge to a stream is significant; relatively few have been conducted on other physiographic and geological regions within the Chesapeake Bay watershed. This study was conducted at the boundary of the Valley and Ridge and Appalachian Plateau physiographic provinces to understand how the hydrological and geochemical conditions in this region effect the transport and removal of NO−3. The groundwater flow system at the farm studied, located at the base of a valley, is influenced by one groundwater flow component parallel to the axis of the valley and a second flowing perpendicular to the axis having been recharged from topographic highs along the sides of the valley. The axis‐perpendicular component is transporting NO−3 and Cl− applied as fertilizers and manure on an upgradient field and also Cl− from salting of an adjacent road to the study site. The relatively nutrient‐free water from the axis‐parallel component dilutes NO−3 and Cl− concentrations at the site from seasonal averages of 11 mg N/L and 90 mg Cl/L to levels <0.4 mg N/L and 1 mg Cl/L, respectively. Some evidence exists for NO−3 removal from groundwater <3 m belowground; however, it is difficult to confirm the removal process with dilution dominating the system.
Aerodynamic Measurements of Methyl Bromide Volatilization from Tarped and Nontarped Fields
Authors: Majewski Michael S. , McChesney Michael M. , Woodrow James E. , Prueger John H. , Seiber James N.
Published: July 2010

Methyl bromide (MeBr) is used extensively in agriculture as a soil fumigant and there is growing concern over the role it may play in the depletion of stratospheric ozone. Methyl bromide is applied using various techniques and very little is known about how much of the applied fumigant volatilizes into the atmosphere after the application. This field study was designed to estimate the post‐application methyl bromide volatilization loss rates from two different application practices. The fields were approximately 6 km apart in Monterey County, California, and were treated in conformity with local practices as of 1992. The MeBr was injected at a depth of 25 to 30 cm. One field was covered simultaneously with a high‐barrier plastic film tarp during the application, and the other was left uncovered, but the furrows made by the injection shanks were bedded over. Volatilization fluxes were estimated using an aerodynamic‐gradient technique immediately following the completion of the application process and continued for 9 d for the tarped field and 6 d for the nontarped field. The cumulative volatilization losses from the tarped field were 22% of the nominal application within the first 5 d of the experiment and about 32% of the nominal application within 9 d including the one day after the tarp was removed on Day 8 after application. In contrast, the nontarped field lost 89% of the nominal application by volatilization in 5 d. The volatilization rate from the tarped field was shown to be significantly lower than the nontarped field at a 95% confidence level.
Critical Evaluation of Models and Their Parameters
Authors: Addiscott Tom , Smith Jo , Bradbury Nicky
Published: July 2010

Some form of critical evaluatory procedure for models is needed to maintain the integrity of modeling and to ensure that the increasingly widespread use of models does not result in the propagation of misleading information. The term validation must be used with the clear understanding that no model can be validated in the sense that it has been unequivocally justified. All that can be achieved is to show how small the probability is that the model has been refuted. Whether this probability is acceptable is a subjective decision. The type of statistical test that is appropriate depends on the quality of the data against which the model is tested. Using a procedure that compares the sums of squares that result from the model not fitting the data with the sums of squares due to error in the data, gives a stringent test, but it requires the replication of measurements. Rigor is as important in evaluating parameters as it is in testing models. Direct measurement is the best option, but where a parameter has to be obtained by fitting, the statistical procedures used for validation are appropriate. In general, the further the data used for parameterization are removed from the data to be simulated the better. Problems can arise in both parameterization and validation if the model is nonlinear regarding its parameters, and the latter have appreciable variances. Parameterization and validation become more difficult as the complexity of the model or the scale at which it is used increase.
Methyl and Total Mercury in Boreal Wetland Plants, Experimental Lakes Area, Northwestern Ontario
Authors: Moore T. R. , Bubier J. L. , Heyes A. , Flett R. J.
Published: July 2010

A review of Hg concentrations cited in the literature reveals values in the general sequence: grassland herbs < trees and shrubs < aquatic macrophytes < Sphagnum < mosses < lichens < fungi, excluding those samples collected near point sources of environmental Hg. Samples of vegetation collected from wetland and upland catchments in the Experimental Lakes Area contained from 4 to 160 μg total Hg (THg) kg−1 and 0.1 to 139 μg methyl Hg (MeHg) kg−1. The lowest concentrations of both THg and MeHg were found in the leaves and needles of trees and shrubs, and the highest concentrations occurred in bryophytes, both feather mosses and Sphagnum. Analysis of sections of the mosses revealed larger concentrations of MeHg in the upper live section, whereas THg concentrations increased slightly down the stem into the dead portions. In terms of broad ecological grouping, THg and MeHg concentrations increased the closer the plant's habitat to the water table, though certain upland mosses also contained very large THg and MeHg concentrations. When combined with biomass data, the vegetation of an ombrotrophic wetland contained an average of 30 μg THg m−2 and 0.4 μg MeHg m−2, dominantly (45 and 73%, respectively) in the mosses. These values are similar to that contained in the peat porewater, but small compared to the estimate of the stock of THg and MeHg contained in the 1.7 m thick peat (12 000 and 200 μg m−2, respectively).
The Cadmium Content of British Wheat Grain
Authors: Chaudri A. M. , Zhao F. J. , McGrath S. P. , Crosland A. R.
Published: July 2010

The Cd content of wheat (Triticum aestivum L.) grain samples collected representatively from the major wheat growing regions of Britain in 1982, 1992, and 1993 was measured. Geographical distributions of grain Cd content were compared with the total Cd concentration in soils of England and Wales. The ranges and mean grain Cd concentrations for 1982, 1992, and 1993 were (mg kg−1 dry weight, DW) 0.016 to 0.18, mean 0.052; 0.008 to 0.27, mean 0.042; and 0.004 to 0.31, mean 0.038, respectively. There was about a 20% decrease in mean grain Cd concentration from 1982 to 1992–1993. The proportion of samples above the World Health Organization's (WHO) limit of 0.12 mg Cd kg−1 DW was 4% for 1982 and 1992 and 2% for 1993. The geographical distribution of these high Cd grain samples corresponded with areas where the total soil Cd concentrations were significantly above background concentrations. Differences between wheat varieties were small and significant (P < 0.001) only for 1992. The concentration of Cd in white flour was significantly correlated with that in wholemeal flour (r = 0.95), and bran Cd was significantly correlated with white flour Cd (r = 0.87). On average, the concentration of Cd in bran was twice that in wholemeal flour, and white flour contained about 31% less Cd than wholemeal flour. The estimated daily dietary Cd intake in the United Kingdom (UK) through the consumption of wheat‐based products was about 8 μg Cd per person or about 11% of the WHO's limit of 70 μg Cd d−1. The Cd content of the vast majority of British wheat grain would not constitute a health hazard to the population of the UK or elsewhere.
Evaluation of Techniques to Improve White Pine Establishment on an Appalachian Minesoil
Authors: Torbert John L. , Burger James A. , Probert Timothy
Published: July 2010

Several reclamation‐reforestation techniques were studied on a reclaimed surface mine in southern West Virginia to develop practical guidelines for the establishment of eastern white pine (Pinus strobus L.) forests interplanted with black locust (Robinia psuedoacacia L.). The study was designed to investigate (i) two herbaceous ground cover mixes (a conventional erosion control cover and a tree‐compatible reforestation cover); (ii) the effectiveness of establishing white pine and black locust by direct seeding versus hand‐planting; and (iii) the effect of fertilizing white pine with a fertilizer tablet. The study was established on a 40% slope with a minesoil derived primarily from an acidic (pH 4.8), oxidized sandstone. With an experimental variance from the West Virginia Department of Environmental Protection, final surface grading was minimized to avoid compaction. The reforestation ground cover was sparser than the conventional cover during the first year and denser after 5 yr, but the difference was not statistically significant and did not affect tree establishment. Although some white pines were established by direct seeding (2 kg/ha), their distribution was irregular. Black locusts were readily established by direct seeding (0.5 kg/ha), but the number of trees established was excessive and interfered with the growth of planted pine. Overall, growth of planted pine was very good, and fertilizer tablets did not result in significantly larger pines after 5 yr. Based on results from this study, the most practical way to establish a productive white pine‐black locust plantation is to plant pine seedlings and interplant or spot‐seed locusts between pines.
Water Flow through Intact Soil Columns: Measurement and Simulation Using LEACHM
Authors: Smith W. N. , Reynolds W. D. , de Jong R. , Clemente R. S. , Topp E.
Published: July 2010

An evaluation of the water flow submodel, LEACHW, of the LEACHM solute transport model was conducted using profiles of volumetric water content, θ(z), and hydraulic head, H(z), measured under steady sated and near‐saturated flow conditions in two large, intact, soil columns. The hydraulic conductivity (K)‐water content (θ)‐pressure head (ψ) relationships, K‐θ‐ψ, required by LEACHW were obtained by fitting the Van Genuchten functions to measurements of sated hydraulic conductivity (Ks) and θ vs. ψ obtained: (i) using in‐situ TDR and tensiometer measurements, with the θ‐ψ data being collected during the initial column wetting; and (ii) using the traditional saturated flow‐desorption technique on intact soil core subsamples collected from the columns at the end of the experiment. The LEACHW model provided reasonably accurate predictions of the θ(z) and H(z) profiles, regardless of whether the in‐situ or soil core‐based K‐θ‐ψ relationships were used, and regardless of whether sated or near‐saturated flow occurred. The LEACHW predictions were substantially more accurate, however, when the K‐θ‐ψ relationships derived from the in‐situ measurements were used. It was concluded that the LEACHW model, coupled with independently measured K‐θ‐ψ functions, could provide reasonably accurate predictions of steady θ(z) and H(z) profiles in large, intact soil columns, regardless of whether the soil macropores are largely water‐conducting (sated flow) or largely nonwater‐conducting (near‐saturated flow). It also appears that in‐situ Ks and θ‐ψ measurements, with the θ‐ψ data collected during initial wetting, may provide more appropriate K‐θ‐ψ relationships for use in water and solute transport models than the traditional saturated flow‐desorption method using intact soil core subsamples.
Modeling pH‐Dependent Sulfate Adsorption in the Bs Horizons of Podzolized Soils
Authors: Gustafsson Jon Petter
Published: July 2010

A model was developed that predicted the pool of adsorbed SO4 in the Bs horizons of northern Scandinavia as a function of pH and the solution SO4 concentration, assuming that 2 H+ are consumed for every SO2−4 adsorbed. To accomplish this, a sequential leach procedure with acid MgSO4 was used which facilitated the determination of SO4 adsorption capacity and the characterization of the adsorption isotherm. The Temkin equation showed the best fit within the range of SO4 concentrations used in this study. The variability between different soils in terms of adsorption capacities and isotherm slopes was modeled using linear and multiple regressions with other soil characteristics. Model results showed good agreement with other experimental observations in northern Scandinavia. The model, however, underestimated SO4 adsorption for soils from southern Scandinavia, which may be because of regional differences in, for example, adsorbent crystallinity. Furthermore, the results show that most pristine soils in northern Scandinavia retain 20 to 40% as much SO4 as they would retain if they were located in a severely acidified area. Therefore SO4 desorption following a decreasing atmospheric S deposition would only involve part of the adsorbed SO4. Only a small hysteresis effect was observed when the adsorption isotherm was compared to the desorption isotherm for one soil.
Phosphorus Leaching from Soils Containing Different Phosphorus Concentrations in the Broadbalk Experiment
Authors: Heckrath G. , Brookes P. C. , Poulton P. R. , Goulding K. W. T.
Published: July 2010

Total P (TP), total particulate P (TPP), dissolved reactive P (DRP), and dissolved organic P (DOP) were determined in waters from pipedrains (at 65‐cm depth) from the Broadbalk Experiment at Rothamsted. Soils that have received either no P, P in farmyard manure (about 40 kg P ha−1) or superphosphate (up to 35 kg P ha−1) annually for >150 yr, now contain 0.5 M NaHCO3‐extractable P concentrations (Olsen‐P) in the plow layer (0‐ to 23‐cm depth) between 5 and 100 mg kg−1 soil. Our aim was to determine if significant quantities of P could be detected in the drainage water and their relationship to soil P concentrations. On five occasions between October 1992 and January 1994, both TP and DRP from plots receiving superphosphate frequently exceeded 1 mg L−1 and were high compared with literature data. Ranging between 66 and 86% of TP, DRP was the largest fraction in drainage water. It remained low (<0.15 mg L−1) from plots below 60 mg Olsen‐P kg−1. There was then a rapid increase in DRP up to the maximum Olsen‐P concentration. A simple linear Split‐Line Model described this relationship very well for all drainage events. This implies that up to 60 mg Olsen‐P kg−1 soil (the change point), P was retained strongly in the plow layer. Above this, P losses in the drainage water were much more closely related to Olsen‐P than commonly suggested. The mechanisms could either be preferential flow or rapid transport of P in forms less susceptible to sorption but finally measured as DRP. The results suggest enhanced P losses through subsurface runoff on heavy soils, once a certain plow layer concentration of Olsen‐P is exceeded.
Effects of Domestic Wastewater Spray Irrigation on Denitrification Rates
Authors: Monnett G. T. , Reneau R. B. , Hagedorn C.
Published: July 2010

Spray irrigation of domestic wastewater has potential as an effective on‐site wastewater treatment and disposal method for soils that have limited renovation capacity. Nitrogen removal via denitrification from spray irrigation can fluctuate due to the alternating aerobic and anaerobic conditions caused by irrigation frequency. The objectives of this study were (i) to determine the effect of domestic wastewater application rates and frequencies within a 24‐h period on nitrous oxide (N2O‐N) emissions from soil columns measured by the acetylene block technique, and (ii) to determine the influence of wastewater irrigation on the denitrification capacity of the soil. Treatments used two effluent application rates (1.25 and 2.5 cm wk−1) and three daily irrigation frequencies (1, 2, and 3 times d−1) and a no‐effluent control. Increased effluent application and splitting the effluent into two or three applications d−1 increased levels of N2O‐N emissions as compared with the control. Single daily doses of effluent produced low levels of N2O‐N emissions over the 24‐h measuring period, whereas more frequent applications produced rapid increases in N2O‐N emissions directly after effluent application. Gaseous losses of N averaged 5.3 and 26.2% of the applied N at the 1.25 and 2.5 cm wk−1 effluent loading rates, respectively. The denitrifying capacity of the soils was limited by both N and C. Maintaining effluent in the upper, more microbially active part of the soil column through split applications was important to N removal via denitrification.
Sorption of Nonionic Organic Compounds by Kentucky Bluegrass Leaves and Thatch
Authors: Lickfeldt D. W. , Branham B. E.
Published: July 2010

Soil organic matter and plant litter layers are largely responsible for the immobility of organic compounds in agronomic environments. The objective of this research was to determine the sorption of nonionic organic compounds by turfgrass leaves and thatch and to correlate the sorption data with water solubilities (Sw) and octanol/water partition coefficients (Kow). Batch suspension experiments for phenanthrene, fenarimol (α‐(2‐chlorophenyl)‐α‐(4‐chlorophenyl)‐5‐pyrimidinemethanol), 1,2,4‐trichlorobenzene, ethoprop (o‐ethyl s,s‐dipropyl phosphorodithioate), and acetanilide (acetylaminobenzene) with Sw from 1 to 5405 mg L−1 were completed on Kentucky bluegrass (Poa pratensis L. cv. Touchdown) leaves and thatch. The resulting linear sorption isotherms (r2 > 0.922) for these organic compounds are consistent with a partitioning mechanism between water and leaves or thatch. The partition coefficients (K) for thatch ranged from 6.32 for acetanilide to 793 for phenanthrene. The K coefficients for leaves ranged from 3.53 for acetanilide to 2520 for phenanthrene. Sorption coefficients normalized for organic C content of the sorbent (Koc) were smaller for leaves and thatch than Koc values for soil organic C. The sorption coefficients for Kentucky bluegrass leaves had linear relationships with both the Sw and Kow of the organic compounds. The K values for Kentucky bluegrass leaves could be predicted from Sw and Kow, but values for thatch were highly variable. Both leaves and thatch were strong sorbents for organic compounds and should be expected to have a significant impact on the sorption and fate of chemicals applied to turf.
Biotechnology By‐Products as Sources of Nitrogen for Plants
Authors: Zhu B. , Tabatabai M. A. , Henning S. J.
Published: July 2010

Recent developments in the biotechnology industries have resulted in production of large quantities of by‐products with potential uses as soil amendments and as sources of nutrients for plant growth and development. Many of these by‐products contain significant concentrations of organic and inorganic N that can be used by plants. This study evaluated, under greenhouse conditions, seven by‐products produced by four biotechnology industries in Iowa for their N‐supplying potentials to plants, and the results were compared with a conventional N fertilizer, urea‐ammonium nitrate (UAN). Corn (Zea mays L.) was grown on three Iowa surface soils treated at eight rates of N ranging from 0 to 500 mg of total N pot−1 (1 kg of soil) and harvested after 34 d. Results showed that both dry matter and N yield increased with increasing the rate of N in the by‐products applied to soil. Dry matter and N yield responses were similar among the three soils, but differed greatly among the by‐products studied. The by‐products FSL and FSG were superior N sources. Significant increases in dry matter and N yields were obtained by application of SMB, SS, Mycel, and HSOM. Among the seven by‐products studied, PC was a poor N source for corn. The by‐product HSOM was very acidic, and FSL and FSG contained high concentrations of NH+4. Addition of these by‐products to soils decreased the soil pH with increasing application rate. Results showed that some biotechnology by‐products are potential sources of N for plants and are useful as soil amendments.
Methyl Bromide Diffusion and Emission through Soil Columns under Various Management Techniques
Authors: Jin Yan , Jury William A.
Published: July 2010

The proposed phaseout of methyl bromide (MeBr) in 2001, while undertaken for environmental reasons, has important economic implications. At the present time, very little is known about how much MeBr escapes from fumigated soils into the atmosphere, or about methods for reducing this loss in an economically feasible manner. In this study we report the results of a series of experiments on MeBr diffusion and emission through soil columns under various management techniques. Column experiments were conducted to evaluate the effectiveness of commonly used polyethylene films in preventing MeBr emission into the atmosphere, and were analyzed with a mathematical model to estimate the soil gas diffusion coefficient (Dsg) and the mass transfer coefficients (h) for different polyethylene films. Additional experiments were then conducted to evaluate the effect of adding various amounts of irrigation water after injection and tarping on total MeBr emission into the atmosphere. The films were found to be only marginally effective in preventing MeBr emission from fumigated soils, while irrigating and then covering the soil with the film was much more effective in reducing MeBr loss.
Phosphorus Status of Forest and Agricultural Soils from a Watershed of High Animal Density
Authors: Simard R. R. , Cluis D. , Gangbazo G. , Beauchemin S.
Published: July 2010

The objective of this work was to study the impact of animal density on P status in soils from the Beaurivage River Watershed, Quebec, Canada. Twenty‐five samples from A, B, and C horizons from the five most representative soil series were taken from sites under forest, hay fields of dairy farms, and farms with a known surplus of on‐farm manure N (SN). Profiles were characterized for water‐soluble P (Pw), Mehlich‐3 extractable P (M3P), and fractions. The Pw was 3.6 times larger in agricultural than in forest soils in the A horizon. Excessive amounts of 66.5 mg kg−1 of M3P and of 95 mg kg−1 Resin‐P were found in the plow layer of agricultural soils and M3P was increased, on average, by 10 mg kg−1 in the C horizon compared with forest soils. The accumulation of added P has lead to an increase in labile (Resin + NaHCO3 + NaOH‐Po) P pools in the A horizon, whereas the resilient (total labile P) pools were the major sinks in B and C horizons. For SN farms, total P was increased by 435 mg kg−1 in the A, 86 mg kg−1 in B, and by 141 mg kg−1 in the C horizon compared with forest soils. Dairy farms soils had labile P contents similar to those from SN farms but were less enriched in resilient‐Pi forms. The observed large P loads in surface horizons and Pw increases in the subsoil of the agricultural soils probably contribute to the contamination of surface waters in this watershed.
On the Use of Virus Transport Modeling for Determining Regulatory Compliance
Authors: Yates Marylynn V. , Jury William A.
Published: July 2010

The U.S. Environmental Protection Agency (USEPA) has developed a draft Ground Water Disinfection Rule (GWDR) proposing that all public water systems using groundwater must disinfect the source water from each of its wells unless the wells meet one of the “natural disinfection” criteria they have developed or the system qualifies for a variance. A water utility that wished to avoid chemical or physical disinfection of its well water and did not meet the prescribed horizontal or vertical setback distances would have the option of using a virus transport model to determine whether there was adequate “natural disinfection” in their system. We think that this procedure is unwise, because there is enormous uncertainty in the estimates of the parameters required by the transport model. This uncertainty is amplified nonlinearly into the model prediction of maximum virus concentration the USEPA wishes to use as the basis for regulatory decisions. For typical levels of uncertainty in the input parameters, we predict that the concentration uncertainty will span many orders of magnitude, rendering model estimates of natural disinfection useless for regulatory purposes.
Contaminant Release from Solidified Radioactive Wastes Buried in Unsaturated Sediments: Lysimeter Study
Authors: Jones T. L. , Serne R. J.
Published: July 2010

A lysimeter facility has been used since 1984 to monitor the leaching of buried waste forms under natural, arid conditions. The facility includes 10 bare‐soil lysimeters (183 cm diam. by 305 cm deep) containing buried waste forms solidified with Portland III cement, masonry cement, bitumen, and vinyl‐ester styrene. From 1984 through 1992, an average of 45 cm of water (27% of area precipitation) have leached through the lysimeters. To date, tritium, 60Co, and 137Cs have been identified in the lysimeter leachate samples. From 1984 through 1992, >4000 µCi of tritium, representing 76 and 71% of inventory (not decay corrected), have been leached from the two waste forms containing tritium. Cobalt‐60 (<0.1% of original Co inventories) has been found in the leachate from each of all six of the waste forms that originally contained >1 mCi of inventory. Mobile Co is believed to be chelated with organic compounds, such as EDTA, present in the waste. Trace amounts of 137Cs have occasionally been identified in leachate from two waste forms since 1991. Qualitatively, the field leaching results confirm laboratory studies, suggesting that tritium is readily leached from cement, and that 60Co is generally leached more from cement than from vinyl‐ester styrene. These data suggest that empirical source‐term models should predict leaching based on the amount of water flowing past the waste form, not based on time.
Remediation of Acid Soils by Using Alkaline Biosolids
Authors: Sloan J. J. , Basta N. T.
Published: July 2010

Alkaline biosolids may be suitable as a liming amendment for acid soils. The efficacy of two alkaline biosolids, lime‐stabilized sewage sludge (LS) and N‐Viro Soil (NV), for remediating soil acidity and Al toxicity in strongly acid soils were evaluated. For comparison, soils were also treated with unlimed anaerobically digested sewage sludge (SS) and agricultural lime (L). Three acid soils were amended with LS, NV, SS, and L and incubated at 25°C. Soil solution was extracted at 1, 30, 90, and 180 d incubation and analyzed for pH, electrical conductivity (EC), dissolved organic carbon (DOC), Al, Mn, Ca, Mg, Na, K, F, Cl, PO4, NO3, and SO4. In general, soil pH increased linearly with amendment rate for all soils and all amendments. The magnitude of increase in soil pH after 6 mo for the four amendments followed the order L ≃ NV>LS>>SS. All amendments decreased soluble Al, but lime‐containing amendments (LS, NV, and L) decreased soluble Al below detection limits (<0.4 mmol L−1). The largest decreases in exchangeable Al were associated with lime‐containing amendments. Lime‐containing amendments reduced soluble Mn but unlimed sewage sludge had no effect on soil solution Mn. Soluble Al speciation using MINTEQA2 showed that all rates of lime‐containing amendments (LS, NV, and L) decreased Al3+ activity to nontoxic levels (<10 mmol L−1). Saturation indices indicated sewage sludge amendments may have resulted in precipitation of Al as alunite [KAl3(OH)6(SO4)2·H2O]. Although SS decreased phytoavailable Al, alkaline biosolids caused greater reductions in potentially phytotoxic Al than nonalkaline biosolids (SS).
Effect of Aliphatic Nonaqueous Phase Liquids on Naphthalene Biodegradation in Multiphase Systems
Authors: Gamerdinger A. P. , Achin R. S. , Traxler R. W.
Published: July 2010

Biodegradation of naphthalene by a Coryneform bacterium was examined in multiphase aqueous slurry systems containing a nonaqueous phase liquid (NAPL). The evolution of 14CO2 provided an index of biodegradation under aerobic conditions. The effect of NAPL hydrophobicity was evaluated by considering a homologous series of n‐alkanes (C6–C16). Experiments were conducted in NAPL‐water and soil‐NAPL‐water systems where the inoculum was pre‐incubated with a sandy aquifer material. Relative to aqueous systems, conversion to CO2 increased in the presence of decane, dodecane, and hexadecane. Biodegradation was apparent, but decreased in the presence of octane, and was negligible in the presence of hexane. Thus biodegradation was sustained in multiphase systems where log Kow of the NAPL was >5, and was inhibited in systems where the log Kow of the NAPL was <4. Naphthalene partitioning between water and each of the NAPLs was similar, indicating that the observed differences in biodegradation among the homologous series were not due to differences in naphthalene distribution. Naphthalene sorption to the sandy aquifer material was minimal and the aquifer material did not significantly modify biodegradation. Mineralization rates were reduced in multiphase systems when compared with aqueous systems; CO2 production curves were described with a first‐order kinetic model. Reduced mineralization rates in soil‐NAPL‐water systems can be explained by the lower aqueous phase concentration. This was not the case in the NAPL‐water system, suggesting a direct effect of the NAPL on the bacteria.
Zinc Concentrations in Groundwater at Different Scales
Authors: Stein A. , Varekamp C. , van Egmond C. , van Zoest R.
Published: July 2010

An extensive database of the concentrations of heavy metals in phreatic groundwater was used to study the spatial variability of Zn. This paper focused on the Zn concentrations in relation to soil survey variables. Three scales of observation were distinguished: provincial level (1:1 000 000), city level (1:100 000), and parcel level (1:10 000). Use of classification of the study area based on digitized maps was investigated. A Geographic Information System (GIS) was used to overlay and investigate different sources of information. The variance of Zn in groundwater decreased by 50% when going from provincial to parcel scale. The results indicate that Zn variation is dominated by short‐range variation. Significant differences in Zn contents were found for Zn grouped by seepage (infiltration vs. deep seepage) and geology. Classification according to seepage yielded reduced coefficients of variation within several seepage class. At the city level, significant differences in Zn were found for soil and land use. The sample semivariogram showed that Zn exhibits a spatial dependence different from that of electrical conductivity (EC) and pH. This may be explained by the distribution of soil groups on the soil map of scale 1:50 000. At the most detailed level, no significant differences in Zn were found between soil units or land use categories. The distinction of significantly different concentrations allows a flexible setting of background threshold values.
Chromosomal Damage Induced by Herbicide Contamination at Concentrations Observed in Public Water Supplies
Authors: Biradar D. P. , Rayburn A. Lane
Published: July 2010

Herbicide contamination of natural resources, specifically groundwater, has drawn considerable public attention in recent years. Although deleterious effects of herbicides at large dosages have been well documented, information is lacking about the possible effects of herbicide levels that are found in public water supplies. Chromosomal damage is examined by flow cytometry on Chinese hamster ovary (CHO) cells that are exposed to three herbicides (atrazine, simazine, and bentazon) at concentrations deemed safe by the U.S. Environmental Protection Agency (USEPA) for drinking water. A known clastogen (ara‐C) is also included as a reference for comparing the magnitude of chromosomal damage caused by herbicides. Chromosomal damage was assessed by measuring the coefficient of variation (CV) and percent chromosomes present in the larger chromosome distribution peaks. Exposure to atrazine (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) increased the CV of the largest chromosome distribution peak at concentrations considered safe by the USEPA. Chromosomes exposed to both simazine (6‐chloro‐N,N′‐diethyl‐1,3,5‐triazine‐2,4‐diamine) and bentazon (3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide) did not exhibit chromosomal damage. Further analyses carried out on atrazine concentrations about equal to levels found in public water supplies revealed the potential of atrazine to induce chromosome breakages in CHO cells. Atrazine concentrations that were manyfold greater than the contamination limits exhibited a true clastogenic nature like ara‐C. The results provide evidence for further investigations as to the potential health risk of consuming water contaminated with atrazine.
Uptake and Translocation Studies in Balsam Fir Seedlings with 54Mn and 65Zn Radioisotopes Applied to Soil Surfaces
Authors: Lin Z.‐Q. , Barthakur N. N. , Schuepp P. H. , Kennedy G. G.
Published: July 2010

Pathways of heavy metal deposits in balsam fir [Abies balsamea (L) Mill.] seedlings were investigated by simultaneously applying 54Mn and 65Zn radioisotopes on soil surfaces. Downward movement of 54Mn and 65Zn in soils was documented to the 14 to 16 cm depth 70 d after application. One‐year‐old needles and 3‐yr‐old twigs concentrated more radioisotopes than older needles and younger twigs, respectively, with the sample specific activity (kBq kg−1) of 54Mn 5 to 10 times higher than that of 65Zn. The activity in seedlings on the 70th d of the experiment was 5.2% of the total remaining activity for 54Mn (6290 kBq) and 2.6 % for 65Zn (6031 kBq). The distribution of 54Mn in the seedling was 31% in roots, 31% in twigs, 26% in stems, and 12% in needles, while roots retained 86% of 65Zn. No appreciable migration of elements from internal tissues to epicuticular wax layers was found when shoots were washed in chloroform. The maximum leaching ratio was below 0.5 and 1.0% for 54Mn and 65Zn, respectively, when shoots were washed in simulated acid rain for 5 min.
The Effects of Substrate Type, Surface Water Depth, and Flow Rate on Manganese Retention in Mesocosm Wetlands
Authors: Stark Lloyd R. , Williams Frederick M. , Wenerick William R. , Wuest Paul J. , Urban Christopher
Published: July 2010

A wetland mesocosm experiment was conducted to determine the effects on Mn retention of substrate type, surface water depth, and flow rate. The main objective of this experiment was to determine if sustained Mn retention could be accomplished under the specific experimental treatments, to recommend design parameters for the construction of field wetland systems for Mn treatment. Crushed limestone was clearly superior to spent mushroom substrate (SMS) with respect to Mn retention. The presence of a layer of free surface water detracted from Mn treatment, while lower flow rates enhanced Mn treatment. Sustained Mn retention was achieved using crushed limestone as the substrate coupled with an absence of surface free water, when inlet water had a pH of 7.0 and no appreciable Fe. Substrate metal extractions indicated that most of the Mn was retained as oxide‐bound Mn (72%), with most (88%) of the Mn retained at the surface of the wetland. Limestone “wetlands” are therefore recommended in the treatment of Mn in neutral‐pH mine water containing no Fe.