bluuebunny/crossref_metadata_2025 huggingface dataset:
Volatile Organic Vapor Diffusion and Adsorption in Soils
Authors: Petersen L. W. , Rolston D. E. , Moldrup P. , Yamaguchi T.
Published: July 2010

Knowledge of the relationship between DP/D0 (diffusion coefficient in soil divided by diffusion coefficient in free air) and the volumetric soil‐air content, ɛ, is important when modeling gaseous movement of volatile organic compounds (VOCs) in soils. The effective diffusion (i.e., diffusion and retardation) of trichloroethylene (TCE), toluene and freon in Yolo silt loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthent) were measured in a two‐chamber diffusion apparatus. The experiments were conducted on packed soil cores over a range of water contents. Vapor retardation factors were calculated from soil parameters and equilibrium partition coefficients. Partition coefficients were measured in batch experiments. It was found that for water contents higher than four molecular layers of water surface coverage, solid/vapor partition coefficients, KD′, were consistent with values predicted by Henry's Law constants (KH), and aqueous/solid partition coefficients, KD. For less than four molecular layers of water, sorption increased by orders of magnitude. The vapor retardation factors, along with the measured effective diffusion, allowed a calculation of diffusion coefficients (DP) for the investigated species by using the analytical solution to diffusion in a two‐chamber apparatus. Values of the ratio DP/D0 were generally higher than the values predicted by the Millington‐Quirk equation, and lower than the values predicted by the Penman equation. Compared with the nonreactive tracer freon, DP/D0 values for TCE and toluene agreed very well for higher water contents. Values obtained for air‐dry soil, however, were under‐predicted. The experimental work for determination of the effective diffusion of reactive tracers can, therefore, for sufficiently high water contents be limited to the determination of Dp/D0‐ɛ relations for a nonreactive tracer and measurement of KD, KD′, and KH values for the reactive tracers.
Oxygen Respirometry to Assess Stability and Maturity of Composted Municipal Solid Waste
Authors: Iannotti D. A. , Grebus M. E. , Toth B. L. , Madden L. V. , Hoitink H. A. J.
Published: July 2010

The stability and maturity of compost prepared from municipal solid waste (MSW) at a full‐scale composting plant was assessed through chemical, physical, and biological assays. Respiration bioassays used to determine stability (O2 and CO2 respirometry) were sensitive to process control problems at the composting plant and indicated increasing stability with time. Radish (Raphanus sativus L.) and ryegrass (Lolium perenne L.) growth bioassays revealed that immature compost samples inhibited growth. Growth of ryegrass in poring mix prepared with cured compost not amended with fertilizer was enhanced as compared to a peat control. Garden cress (Lepidium sativum L.) seed germination, used as an indicator of phytotoxicity, revealed inhibition of germination at all compost maturity levels. The phytotoxicity was thought to be salt‐related. Spearman rank‐order correlations demonstrated that 02 respirometry, water‐soluble organic C, and the water extract organic C to organic N ratio, significantly correlated with compost age and best indicated an acceptable level of stability. Oxygen respirometry also best predicted the potential for ryegrass growth, and an acceptable level of compost maturity.
Sulfate Sorption in Soils under Acid Deposition: Modeling Field Data from Forest Liming
Authors: Prenzel Jürgen , Meiwes Karl‐Josef
Published: July 2010

Sulfate sorption can modify the reaction of a soil to acid depositions. Different models of this process exist. In a preceeding paper the adsorption isotherm and the solubility product modeling approach have been compared and a solubility product model has been introduced. The latter model is tested using a forest liming experiment. Concentration data from canopy drip and seepage covering a 20‐yr observation period are used as 3‐yr moving averages. The model assumes a steady seepage flow and uses only one 1‐m compartment. The model considers joint chemical equilibria for gibbsite, jurbanite, cation exchange, and complexation. The seepage pH and concentrations of Al and sulfate under the unlimed reference plot can be modeled if a reduced CEC and a free parameter function for alkalinity production are used. The sulfate desorption caused by liming can be explained by the model. It is concluded that sorbed sulfate contributes to the lime requirement of an acidified soil.
Treatment of Contaminated Soils with Organoclays to Reduce Leachable Pentachlorophenol
Authors: Brixie J. M. , Boyd S. A.
Published: July 2010

The toxicity characteristic leaching procedure (TCLP, method 1311) (USEPA, 1990) was used to evaluate the effectiveness of nine organoclays in reducing the leachability of pentachlorophenol (PCP) from three highly contaminated (3000–5000 mg kg−1) soils from wood treatment facilities. The soils differed in their PCP, oil and grease, and organic C contents. The organoclays were smectite exchanged with quaternary ammonium cations of the form [(CH3)3NR]+ or [(CH3)2NR2]+ where R is an aliphatic or aromatic hydrocarbon. A cement‐based solidification agent (Sorbond) was also added to the soil to evaluate its effects on the leachability of PCP. Organoclays with large (>C10) aliphatic R groups (organophilic organoclays) were compared with those with small aromatic or aliphatic groups (adsorptive organoclays). The adsorptive organoclays were much less effective than the organophilic clays in reducing PCP levels in the TCLP leachate. The organophilic clays dramatically reduced the leachability of PCP from all of the soils. The most effective clay tested was the dimethyldicocoammonium smectite; a 20% addition of this organoclay to the soil resulted in leachable PCP levels below the detection limit (0.2 mg L−1). The addition of Sorbond to the soil increased both the pH (from 4.95 to 12.00) and the PCP concentrations (from 6.8 to 100.8 mg L−1) in the leachate. However, when Sorbond was added with an organophilic clay, the PCP concentration was decreased below detection limits despite the increase in pH. These results demonstrate the potential effectiveness of organoclays for reducing the leaching of PCP from highly contaminated soils.
Atrazine Adsorption in Sandy Soils of Wisconsin
Authors: Seybold C. A. , McSweeney K. , Lowery B.
Published: July 2010

Previous studies have shown the mobility of atrazine [2‐chloro‐(4‐ethylamine)‐6‐(isopropylamino)‐s‐triazine] to be greatly different between characteristically similar sandy soils in Wisconsin. This study was conducted to determine if there are differences in atrazine adsorption capacity between sandy soils from Wisconsin, and if differences exist, what soil properties might be contributing to these differences. Atrazine distribution coefficients (Kd) were determined, and amounts of selected soil constituents (i.e., organic matter, clay, Fe oxides) were characterized by horizon in five sandy soils from different geographic regions of Wisconsin. The Kd values were strongly and significantly correlated to the OC content (r2 = 0.84). Also, clay contents in the lower subsoil horizons were significantly correlated to the Kd (r2 = 0.51). The organic fraction is the most important constituent for adsorption of atrazine in these sandy soils that contain small amounts of organic matter and clay. The Koc (Kd × 100/%OC) values varied considerably among soils and within soils with depth, and is attributed to differences in the ability of organic matter to adsorb atrazine and in contributions from clay minerals in the lower subsoil horizons. The pattern of Koc variation with depth is consistent across all soils. Surface soils that developed under forest have much larger Koc values than those that developed under prairie vegetation. We suggest that the larger atrazine adsorption capacity of organic matter in soils originally formed under forest vegetation contributes to the lower mobility of atrazine observed in these soils.
Utility Right‐of‐Way Contaminants: Polycyclic Aromatic Hydrocarbons
Authors: Wan Michael T.
Published: July 2010

Utility right‐of‐way (ROW) ditches flowing into salmon (Oncorhynchus spp.) streams in the Lower Mainland and Vancouver Island of British Columbia, Canada, were sampled in 1990 and 1991 to determine the presence of polycyclic aromatic hydrocarbons (PAHs). Ditches of parklands, farmlands, and railway ROWs were also sampled to establish background and reference PAH concentrations. While PAHs were not detected in ditches of parklands, they were found in farmlands and in utility and railway ROW ditches. Concentrations of PAHs averaging 5.6 µg/L and 0.79 mg/kg were found in ditch water and sediments of farmlands, respectively. In utility ROW ditches, PAHs in water adjacent to treated poles averaged 551.7 µg/L, compared with a mean level of 23.2 µg/L 4 m downstream; in sediments collected from the same sites, the mean concentration of PAHs was 15 mg/kg and 3.3 mg/kg, respectively. Soils at the base of utility poles showed a mean PAH concentration of 3076 mg/kg, while wood chips/splinters from treated wood poles and railway ties contained about 62 000 mg/kg and 16 000 mg/kg PAHs, respectively. Levels of PAHs found in ditch water adjacent to treated poles did not exceed the 96‐h LC50 (lethal concentration of a chemical to 50% of the test fish population) of salmonids and aquatic invertebrate. The biological implications to these animals of exposure to low level PAH‐contaminated ditch sediments are discussed.
Comparison of Water Movement and Quality in Earthworm Burrows and Pan Lysimeters
Authors: Shipitalo M. J. , Edwards W. M. , Redmond C. E.
Published: July 2010

Although a number of investigators have suggested that earthworm burrows can affect water movement and quality, little attempt has been made to directly measure their effect in the field. Using individual samplers, we monitored flow in Lumbricus terrestris L. burrows for 11 mo in adjacent no‐till and conventionally tilled watersheds used for the continuous production of corn (Zea mays L.). Tension‐free pan lysimeters were used to assess the composition and amount of bulk subsurface flow in each watershed and SrBr2·6H2O tracer was broadcast on a 25‐m2 area surrounding the samplers. In both watersheds the earthworm burrows functioned as preferential flow paths collecting more water, NO3‐N, Br, NH4‐N, and Sr than an equivalent area of soil overlying the pan lysimeters. Transport through the bulk soil was less in the tilled than in the no‐till watershed, and the burrows in the tilled watershed were less effective flow paths than those in the no‐till watershed, apparently due to disruption by tillage. Based on an estimated 1.6 million burrows (≥5‐mm diam.) per hectare, the amount of water, NO3‐N, Br, and Sr transported in these macropores was small, representing <5% of the totals measured using pan lysimeters. Data from burrow samplers and pan lysimeters installed in five farmer‐owned, no‐till fields under different soils and production practices supported the results obtained in the no‐till experimental watershed.
Estimating Herbicide Partition Coefficients from Electromagnetic Induction Measurements
Authors: Jaynes D. B. , Novak J. M. , Moorman T. B. , Cambardella C. A.
Published: July 2010

A potential method for reducing pesticide leaching is to base application rates on the leaching potential of a specific chemical and soil combination. However, leaching is determined in part by the partitioning of the chemical between the soil and soil solution, which varies across a field. Standard methods of measuring the pesticide‐soil partitioning coefficient (Kd) are too expensive and slow for routine field mapping. Therefore, alternative methods for mapping Kd must be found if variable application methods are to be successful. We investigated the use of noncontacting electromagnetic induction measurements as surrogate measures of Kd. We measured the partition coefficient for atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), apparent electrical conductivity by electromagnetic induction (Em), and mass fraction of soil organic carbon (foc) on a 250 by 250 m grid with a 25 m spacing. Both Kd and foc were lognormally distributed, while Em was poorly described by either a normal or lognormal distribution. Maps of the measured parameters showed similar spatial patterns, having low values on well‐drained soils and high values on poorly drained soils. Correlation coefficients between Kd and Em and Kd and foc were 0.575 and 0.686, and showed distinct spatial patterns. Spatial structure as indicated by correlograms indicated that each parameter was spatially dependent to distances of about 80 m. Simple relationships of Kd = 176 foc and Kd = exp(0.0336 Em) were found between the data. Maps of Kd estimated from foc or Em were similar to measured Kd, but more diffuse. Electromagnetic induction measurements failed to predict the observed high K6d values. The advantage of using Em measurements to map Kd is that it is a rapid, easy, and inexpensive method once it has been calibrated.
Measurement of Trichloroethylene Diffusion as a Function of Moisture Content in Sections of Gravity‐Drained Soil Columns
Authors: McCarthy Kathleen A. , Johnson Richard L.
Published: July 2010

Experiments were conducted on discrete sections of gravity‐drained sand columns to determine the relationship between the effective diffusion coefficient of trichloroethylene and moisture content in variably saturated porous media. The columns were gravity drained to closely approximate field conditions and the moisture content within each column ranged from field capacity near the top to saturation near the bottom. Measured effective diffusion coefficients were compared with theoretical coefficients calculated using Millington's expression for tortuosity, modified to incorporate diffusion in both the gas and aqueous phases. Agreement between the measured and theoretical effective diffusion coefficients was good for all moisture contents investigated.
Release of Nitrogen and Phosphorus from Poultry Litter
Authors: Robinson J. S. , Sharpley A. N.
Published: July 2010

In areas of intensive poultry production, large amounts of litter produced are often applied as fertilizer to local agricultural land. To assess the agronomic and water quality implications of poultry litter applications, we quantified the effects of recurring, simulated rainfall (5 × 50‐min rainfalls of 2.54 cm h−1) alternated with different drying temperatures (4, 20, 30, and 35°C for 1 h) on the release of dissolved N and dissolved P from two types of poultry litter (pine bark shavingsand wheat straw‐based). Amounts of litter leached were equivalent to a 10 Mg ha−1 application, containing an average of 360 kg N ha−1 and 158 kg P ha−1. A total of 74 kg ha−1 NH4‐N, which accounted for >95% of the dissolved N, and 14 kg ha−1 inorganic P were released by the end of five rainfalls (averaged for the two types of poultry litter, and for all drying temperatures). Although the pattern of N and P release from litter was similar for all drying periods, the magnitude of losses was a function of drying temperature. The average portion of total N present in the litters released as NH4‐N during five rainfalls decreased from 22% for litter dried at 4°C to 18% for litter dried at 3S°C. This decrease was attributed to an increase in N volatilization at the higher temperature. Conversely, the portion of litter P released as dissolved inorganic P, increased from 8% at 4°C to 10% at 35°C. Thus, the influence of drying temperature on the release of N and P should be considered when determining the optimum timing of poultry litter application. It is suggested that the timing of poultry litter application should coincide with active periods of crop growth to combine maximum agronomic productivity with minimum edge‐of‐field losses of N and P to surface and groundwaters. As much as 60% of the N and 40% of the P released during the five rainfalls was lost during the first rainfall. This initial rapid N and P release stresses the importance of avoiding litter applications during periods of heavy rainfall.
Nutrient‐Loss Trends for Vegetable and Citrus Fields in West‐Central Florida: I. Nitrate
Authors: McNeal B. L. , Stanley C. D. , Graham W. D. , Gilreath P. R. , Downey D. , Creighton J. F.
Published: July 2010

Vegetable and citrus production in west‐central Florida is reportedly of considerable eutrophication hazard to local groundwater and surface‐water bodies, including a 33 000‐ha drinking‐water supply reservoir (Lake Manatee) near the coast of the Gulf of Mexico. Nitrate‐N levels were assessed for three vegetable‐production seasons during 1990 and 1991 using a combination of multilevel samplers into the shallow (surficial) aquifer beneath selected vegetable fields and citrus groves, coupled with piezometric wells around each field's periphery to assess direction and rate of groundwater flow. The NO3‐N concentrations beneath vegetable sites showed sizeable spikes (up to 130 mg L−1 NO3‐N), especially early in the season and at season's end, though almost exclusively at <1‐m depth. These concentrations did not persist, however, with the overwhelming majority of samples from most vegetable sites evidencing NO3‐N concentrations below 1 mg L−1. At citrus sites from the same area, NO3‐N concentrations in the surficial water table (located 2–4 m below the soil surface in this case) have evidenced high (20–40 mg NO3‐N L−1) and persistent levels throughout the entire sampling period. This zone of NO‐N enrichment commonly extends 2 to 3 m into the surficial aquifer before NO3‐N concentrations decline to <10 mg L−1 once more. Rates of lateral movement off‐site averaged 20 to 40 m yr−1 for the vegetable sites and 200 to 400 m yr−1 for the more undulating citrus sites. It is postulated that gaseous denitrification losses naturally remediate the periodic spikes in NO3‐N concentrations beneath the vegetable sites because of the high water tables maintained at such locations, whereas denitrification in the deep sands beneath typical citrus sites proceeds much more slowly due to such limitations as a soluble‐C energy source and/or a suitable microbial population. The results have implication with respect to shallow water table vs. deeply rooted crop‐production systems from the same geographic area, wherever such pairings may occur.
Nitrogen Loss from Coffee Agroecosystems in Costa Rica: Leaching and Denitrification in the Presence and Absence of Shade Trees
Authors: Babbar Liana I. , Zak Donald R.
Published: July 2010

Coffee (Coffea arabica L.) management in Costa Rica is changing from traditional agroecosystems, where coffee is grown beneath a tree overstory, to management systems where shade trees are removed and N fertilizer is applied at high rates (ca. 300 kg N ha−1 yr−1). Although fertilization increases coffee bean production, it also increases the potential for substantial loss of N to groundwater and the atmosphere. We investigated NO−3 leaching and the factors controlling denitrification in shaded and unshaded coffee plantations in the Central Valley of Costa Rica; both plantation types were fertilized with 300 kg N ha−1 yr−1. Nitrate leaching was quantified using porous ceramic cup lysimeters placed 60 cm below the soil surface. Losses were estimated by multiplying the soil water NO−3 concentration by the monthly soil water excess, determined as the difference between precipitation and actual evapotranspiration. In addition, a laboratory experiment was conducted to investigate the influence of NO−3, C, and O2 availability on N2O production and total denitrification (N2O‐N + N2‐N). Annual leaching losses of NO−3 were almost three times greater in unshaded plantations (24 kg NO−3‐N ha−1 yr−1) than those in shaded plantations (9 kg ha−1 yr−1). In contrast, mean total denitrification rates in control soil samples from shaded plantations were 60% higher (732 µg N2O‐N kg−1 d−1) than in unshaded plantations (455 µg N2O‐N kg−1 d−1). Carbon additions elicited the largest increase in denitrification, generating nearly a threefold increase (+ C = 8396 µg N2O‐N kg−1 d−1; −C = 2985 µg N2O‐N kg−1 d−1) in both plantation types. Anaerobic conditions also significantly increased denitriflcation (+ O2 = 4331 µg N2O‐N kg−1 d−1; µO2 = 6656 µg N2O‐N kg−1 d−1). In both plantation types, the potential for N loss via NO−3 leaching was small compared with that for gaseous N loss.
Atrazine and Metolachlor Loss in Surface and Subsurface Runoff from Three Tillage Treatments in Corn
Authors: Gaynor J. D. , MacTavish D. C. , Findlay W. I.
Published: July 2010

Conservation tillage with residue management has been proposed as the most effective means to reduce soil deterioration in southwestern Ontario. Two conservation tillage treatments, ridge (RT) and zero (ZT) tillage, were compared with conventional moldboard plow (CT) tillage from 1987 to 1990 for atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methyethyl)‐1,3,5‐triazine‐2,4‐diamine], deethylatrazine [6‐chloro‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] loss in surface runoff and tile discharge. Twenty‐five to 44% of the annual rainfall resulted in total field runoff (surface runoff or tile discharge). Conservation tillage increased surface runoff 42% and decreased tile discharge 15% compared with conventional tillage, but total field runoff was the same from all treatments. Runoff events shortly after herbicide application produced the greatest herbicide concentrations and losses in both surface runoff and subsurface drainage. Averaged over years, herbicide concentration in surface runoff and tile discharge was, respectively, 1.3 and 1.8 times greater from conservation than conventional tillage. Conservation tillage altered the source of herbicide loss compared with conventional tillage, but environmental factors after herbicide application were more important in determining total herbicide loss than tillage. Deethylatrazine was found in both surface runoff and tile drainage and accounted for 10 to 27% of combined atrazine and drethylatrazine loss.
Radium in Phosphogypsum Leachates
Authors: Rutherford P. M. , Dudas M. J. , Arocena J. M.
Published: July 2010

Phosphogypsum (PG) is an acidic by‐product of the phosphate fertilizer industry, and is produced in large quantities by the wet phosphoric acid process. Most PG is sluiced out to repositories, forming large stockpiles. Phosphogypsum is composed mainly of gypsum (Ca‐SO4·2H2O), but contains impurities of environmental concern such as F−, acids, trace elements, and naturally occurring radionuclides, which originate from the phosphate rock used in processing. Possible movement of these impurities into groundwater is an issue. 226Radium is the major source of radioactivity in PG produced from sedimentary phosphate rock. Few studies have addressed the leachability of 226Ra because solid solutions of Ra, Ba, and Sr are very insoluble. The objective of this study was to investigate the concentrations of 226Ra, Ba, and Sr in leachate generated from PG produced from Togo phosphate rock. Phosphogypsum was extracted 30 times with deionized distilled (d.d.) H2O over 30 d. Extractable 226Ra was maximal (0.55 Bq L−1) for Day 1 but remained relatively constant between Day 2 and Day 30. Minimum extractable 226Ra (0.23 Bq L−1) occurred on the Day 30 extraction but still exceeded the current U.S. drinking water standard. Solid phase 226Ra increased between Day 0 (850 Bq kg−1) and Day 30 (1120 Bq kg−1). The 226Ra/Ba ratios in the solid phase and in the extractable liquid phase were nearly equal over the last half of the extraction period. If this relationship holds for other PGs, then solution 226Ra activities can be estimated if solid‐phase 226Ra/Ba ratios are known and Ba solution concentrations are known or estimated.
Fingerlike Wetting Patterns in Two Water‐Repellent Loam Soils
Authors: Dekker Louis W. , Ritsema Coen J.
Published: July 2010

In soils with fingered flow, surface‐applied solutes can reach the groundwater more rapidly than in the case of homogeneous wetting. So far, fingered flow has been thought to be restricted to fine over coarse‐textured soils and homogeneous sandy soils. The present study was undertaken to demonstrate the occurrence of fingerlike wetting patterns in a silt loam and in a silty clay loam soil, and to investigate the influence of dry bulk density and water repellency on the observed soil moisture patterns. Fingerlike patterns were photographed and soil water contents determined by intensive soil core sampling. In both soils, dry bulk density was not a main factor in inducing wet fingerlike patterns and high water content variability. The degree and persistence of potential water repellency were measured on soil samples using the alcohol percentage test and the water drop penetration time (WDPT) test. Spatial variability of degree and persistence of potential water repellency and, accordingly, of soil water contents were high. The actual water repellency was measured on field‐moist samples to obtain critical soil water content values. The soil is wettable above and water‐repellent below these values.
Plant Uptake and Determination of Arsenic Species in Soil Solution under Flooded Conditions
Authors: Onken B. M. , Hossner L. R.
Published: July 2010

Previous studies have not identified the different As species present in soil systems and determined if effective differences exist between As species with respect to plant parameters such as growth rate and As uptake. This study determined the species and concentrations of As present in soil solution of flooded soils and correlated them to As concentration, P concentration, and growth rate of plants grown in treated soils. Rice (Oryza sativa L.) was grown in two soils treated with 0, 5, 15, 25, 35, and 45 mg As kg−1 soil added as either Na‐arsenate or Na‐arsenite. Soil solution samples and plant samples were collected over a period of 60 d. The As concentration of rice plants best correlated to the mean soil solution arsenate concentration in a Beaumont clay (fine, montmorillonitic, thermic Entic Pelludert) and to the mean soil solution arsenite concentration in a Midland silt loam (fine, montmorillonitic, thermic Typic Ochraqualf). In both soils, plant P concentration was best correlated to the amount of As added to the soil rather than any soil solution As concentration. Plant weight was best correlated to the mean soil solution arsenate concentration in both soils. The rate of As uptake by plants increased as the rate of plant growth increased. Plants grown in soils treated with As had higher rates of As uptake for similar rates of growth when compared with plants in untreated soils. However, growth per unit of As uptake was higher for plants in untreated soils than plants in As treated soils.
Water Contamination by Ammonium Nitrogen Following the Spreading of Hog Manure and Mineral Fertilizers
Authors: Gangbazo G. , Pesant A. R. , Barnett G. M. , Charuest J. P. , Cluis D.
Published: July 2010

Inappropriate fertilization practices in regions where livestock manure exceeds crop requirements may cause pollution by NH+4‐N) during snowmelt. Annual and seasonal NH+4‐N losses were evaluated for three consecutive years from 45 m2 corn (Zea mays L.) and timothy (Phleum pratense L.) and red and white clover (Trifolium repens L.) erosion plots that had annually received the recommended chemical fertilizer rates of 180 and 55 kg N ha−1, respectively, plus hog manure at twice those rates. Total N applications for corn and forage were 540 and 165 kg ha−1 except for a check plot receiving only fertilizer. The hog manure was surface‐applied in three different ways: all in the fall, all in the spring, and in a split application with about one‐half in each season. Corn plots receiving fall‐applied manure were immediately rototilled while plots receiving spring‐applied manure were ratotilled prior to planting. Each plot was equipped to collect runoff and drainage water separately throughout the whole year. Total NH+4‐N losses in both runoff and drainage water from autumn application were greater than for the two other application methods for corn and the forages. Plots receiving chemical fertilizer plus hog manure had a significant increase in NH+4‐N losses as compared with the plots receiving fertilizer only. Due to the fall manure effect, NH+4‐N loads increased by three‐fold after the first year (1.11–3.43 kg ha−1), by 1.46 times between the first and the second year, and by 1.14 times between the second and the third year for corn when compared with the fertilizer only treatment and exceeded the standard of 0.5 mg L−1 for raw water. Similar trends were measured for the forages. Most NH+4‐N was lost during the autumn and winter periods for corn. For both crops, there was an increase in loss from fall to winter and a decrease both from winter to spring and from spring to summer.
Pesticides in Eastern North Carolina Rural Supply Wells: Land Use Factors and Persistence
Authors: Maas R. P. , Kucken D. J. , Patch S. C. , Peek B. T. , Van Engelen D. L.
Published: July 2010

Water samples were collected from 171 rural domestic well supplies in eastern North Carolina and analyzed for eight pesticides. Information on borehole depth, well‐easing depth, distance to nearest pesticide mixing area, types of pesticides used, and distance to nearest field application was obtained for each site. Four herbicides [alachlor, 2‐chloro‐2′‐6′diethyl‐N‐(methoxymethyl)‐acetanilide; atrazine, 2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine; metolachlor, 2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide; trifluralin, α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine] were detected in the samples, with detection frequencies of 8.8, 8.2, 3.6, and 1.8%, respectively. About 15% of the samples contained at least one of these herbicides, with resampling indicating persistence throughout the year. Only alachlor concentrations were in excess of maximum contaminant levels (MCLs; 2.0 μg L−1) or Health Advisory Levels (HALs; 0.4 μg L−1) established by the U.S. Environmental Protection Agency (USEPA). Neither atrazine nor alachlor detection exhibited statistical correlation with well depth, although both were rarely detected in wells >100 feet deep. Atrazine concentrations and detection frequencies did not correlate with distance to nearest application site, while alachlor had a significantly greater detection frequency for wells further from the nearest application site. For nearly one‐half of the wells with detectable atrazine and alachlor, there was no reported usage of either herbicide on the same farm during the previous three years, possibly indicating herbicide transport in groundwater or long times before degrading. No statistically significant relationships were observed between the presence of alachior or atrazine, and distance from the well to the nearest pesticide handling and storage area. Although inconclusive by itself, this indicates that at least some contamination originated from other than point‐source spills. Nitrate‐N concentrations in well water were poor predictors for atrazine and alachlor presence in this study.
A Natural Gradient Transport Study of Selected Herbicides
Authors: Widmer S. K. , Spalding R. F.
Published: July 2010

The behavior of trace quantities of commonly detected herbicides and herbicide degradates was investigated in a shallow sand and gravel aquifer. In 1991, a solute pulse containing approximately 15 mg L−1 bromide, 3 μg L−1 atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), 2 μg L−1 alachlor (2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)‐acetanilide), 10 μg L−1 cyanazine (2‐[[4‐chloro‐6‐(ethylamino)‐S‐triazin‐2‐yl]amino]‐2‐methylpropionitrile), and 10 μg L−1 metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide) was injected into a shallow aquifer near Fremont, NE. The plume was monitored for 2 mo following injection using an array of multilevel samplers. A second injection in 1992 included approximately 10 mg L−1 bromide, 1 μg L−1 butachlor (2‐chloro‐2′,6′‐diethyl‐N‐(butoxy methyl) acetanilide), and 3 μg L−1 atrazine, deethylatrazine (DEA) (2‐amino‐4‐chloro‐6‐isopropylamino‐1,3,5 triazine) and deisopropylatrazine (DIA) (2‐amino‐4‐chloro‐6‐ethylamino‐1,3,5 triazine). This plume was monitored for 3 mo. Retardation factors (Rs) were determined for each herbicide by comparing concentration profiles to those of the conservative tracer; Rs were calculated as the ratio of first central moments. Results indicated only slight retention of all injected compounds. Retardation factors for atrazine, DEA, DIA, cyanazine, alachlor, and metolachlor were less than 1.3, with butachlor being slightly more retained (R = 1.65). Persistence of the injected compounds was estimated by the decrease with time in area under the breakthrough curves. Atrazine, DEA, DIA, cyanazine, and metolachlor showed no detectable loss. Losses of alachlor and butachlor were approximately 40 and 70%, respectively, in a 2‐mo period.
Feasibility of Cyclic Reuse of Saline Drainage in a Tomato‐Cotton Rotation
Authors: Shennan C. , Grattan S. R. , May D. M. , Hillhouse C. J. , Schachtman D. P. , Wander M. , Roberts B. , Tafoya S. , Burau R. G. , McNeish C. , Zelinski L.
Published: July 2010

Use of saline drainage water for crop irrigation has been proposed as a strategy to reduce drainage volume and conserve good quality water. Over a 6‐yr period, two cyclic drainage‐water reuse practices were tested in a 3‐yr rotation of processing tomato (Lycopersicon esculentum L.) and cotton (Gossypium hirsutum L.). In both practices, drainage water (ECi = 7.4 dS m−1 and 0.74 mmol L−1 B) was applied to processing tomato after first bloom to take advantage of salt‐induced enhancement of fruit quality and increased crop salt tolerance at later developmental stages. In one practice, drainage water was also applied to the following cotton crop after thinning. Nonsaline water was used for irrigation at all other times and throughout for the control. When saline water was applied once every 3 yr, yields of both crops were unaffected. Tomato yields were generally lowest when saline water was applied 2 out of 3 yr, but saline water improved tomato fruit quality by increasing °Brix in most years. Changes in soil chemical and physical quality may limit long‐term reuse. Both B and salts accumulated in the soil over time, particularly at depth (60–140 cm), whereas Se was more readily leached and showed greater fluctuations in the rootzone with irrigation treatment. Calculations using reclamation formulae estimated that for low B drainage water, the amount of drainage wager used exceeded that of nonsaline water needed to return soil ECe to control levels, resulting in significant water savings. For high B drainage water, more than twice the amount of nonsaline water was needed to fully reclaim the profile than was saved by reuse. However, moderately B‐tolerant crops could be successfully grown during the reclamation period, making cyclic reuse for at least 6 yr an attractive option for growers facing limited supplies of nonsaline water supplies, or as a means to reduce effluent volumes.
Soil Characteristics of Oak Stands along an Urban‐Rural Land‐Use Gradient
Authors: Pouyat Richard V. , McDonnell Mark J. , Pickett S. T. A.
Published: July 2010

Urban‐rural land‐use gradients are environmental gradients determined by human‐built structures and human activity. Although gradients of land use are readily measurable, little is known about the effects of urbanization on forest soil properties. In this research, soil properties were quantified in oak stands (Quercus sp.) along an urban‐rural transect in the New York City metropolitan area. A suite of 25 soil chemical properties were subjected to a Principal Component Analysis to ordinate stands. The first principal component (PC1) accounted for 42.3% of the variation. Positive loadings of PC1 corresponded to high concentrations of Pb, Cu, Ni, Ca, Mg, and K; high total soluble salt concentrations; high organic matter; high total N; and slightly more soil acidity. Stands located closer to the urban core had positive loadings on PC1; sites located beyond 30 km of the urban core had negative loadings. The variation accounted for by PC1 was significantly explained (P < 0.005) by measures of urban development quantified along the transect, including percent urban cover (r2 = 0.735), population density (r2 = 0.700), traffic volume (r2 = 0.778), and road density (r2 = 0.700). Of the heavy metals measured, Cu and Pb showed a 2.5‐ to fourfold increase in concentration from the rural to the urban land use types, with maximum concentrations for Cu reaching 49.3 mg kg−1 and Pb 181.4 mg kg−1 in the urban sites, repectively. More transects must be established in this and other metropolitan areas to build a data base to develop predictive models of ecosystem change, given the amount and type of urban development in a landscape.
Evaluation of Nitrogen Availability in Irradiated Sewage Sludge, Sludge Compost and Manure Compost
Authors: Wen Guang , Bates Thomas E. , Voroney R. Paul
Published: July 2010

A field experiment was conducted during 2 yr to determine plant availability of organic N from organic wastes, and effects of gamma irradiation on organic N availability in sewage sludge. The wastes investigated were: digested, dewatered sewage sludge (DSS), irradiated sewage sludge (DISS), irradiated, composted sewage sludge (DICSS), and composted livestock manure (CLM). The annual application rates were: 10, 20, 30, and 40 Mg solids ha−1. Fertilizer N was added to the control, to which no waste was applied, as well as to the waste applications to ensure approximately equal amounts of available N (110 kg N ha−1) for all treatments. Lettuce (Lactuca indica L.), petunias (Petunia × hybrida Vilm.), and beans (Phaseolus vulgaris L.) were grown in 1990 and two cuts of lettuce were harvested in 1991. Crop yields and plant N concentrations were measured. Assuming that crop N harvested/available N applied would be approximately equal for the control and the waste treatments, the N from organic fraction of the wastes, which is as available as that in fertilizer, was estimated. With petunia in 1990 and the combination of first and second cut of lettuce in 1991, the percentage ranged from 11.2 to 29.7 in nonirradiated sludge, 10.1 to 14.0 in irradiated sludge, 10.5 to 32.1 in sludge compost and 10.0 to 19.7 in manure compost. Most often, the highest values were obtained with the lowest application rates. Yields of petunia and N concentrations in second cut lettuce in 1991 were lower with irradiated sludge than with nonirradiated sludge suggest that the availability of organic N in digested sludge may have been reduced after irradiation. Irradiation of sludge appears to have released NH+4‐N. The availability of organic N, however, appears to have been reduced by irradiation by greater amount than the increase in NH+4‐N.
Potential Microencapsulation of Pyrite by Artificial Inducement of Ferric Phosphate Coatings
Authors: Evangelou V. P.
Published: July 2010

Pyrite in mining waste is initially oxidized by the atmospheric O2, releasing acidity and Fe2+. At a pH below 3.5, Fe2+ is rapidly reoxidixed by Thiobacillus ferrooxidans to Fe3+, which oxidizes pyrite at a much faster rate than O2. Commonly, the approach used in preventing pyrite oxidation in the field involves the use of limestone. This approach, however, has a short span of effectiveness because the surfaces of pyrite particles in mining waste are still exposed to the atmospheric O2 after treatment. The objective of this study was to examine the feasibility in controlling pyrite oxidation by creating an FePO4 coating on pyrite surfaces to block access of the atmospheric O2 to pyritic surfaces. The coating methodology involved leaching pyrite using a chromatographic column with a 1 cm i.d. and a flow rate of 0.5 mL min−1 at 40°C with a PO4 solution containing hydrogen peroxide (H2O2); when this solution reached pyrite surfaces, H2O2 oxidized the surface portion of pyrite and released Fe3+ so that Fe phosphate precipitated and formed a passive coating on pyritic surfaces. This laboratory‐scale study demonstrated that Fe phosphate coatings on pyritic surfaces could be established with a solution containing as low as 10−4 tool L−1 phosphate and 0.03 mol L−1 H2O2 and that the FePO4 phosphate coating could effectively protect pyrite from oxidizing further.
Swine Manure Nitrogen Conservation in Storage using Sphagnum Moss
Authors: Barrington S. F. , Moreno R. Garcia
Published: July 2010

Sphagnum peat moss, floating on swine manure in storage, was tested during three summers as an N conservation method in experimental tanks which measured 0.75 m in diameter and 3.0 m deep. Three depths of floating peat moss (0, 10, and 20 cm) were tested. The swine manure was analyzed prior to the tests and after 14 wk of storage, from June to mid‐September. An average of 54, 60, and 76% total N conservation was observed for the respective treatments. Twenty centimeters of peat moss significantly reduced manure N losses and manure evaporation during storage.
Analysis of the Cadmium Flux in Sweden with Special Emphasis on Landfill Leachate
Authors: Flyhammar Peter
Published: July 2010

Cadmium (Cd) fluxes and sinks in Sweden have been analyzed. Emphasis was focused on landfills since they contain large amounts of Cd and constitute one of the biggest potential environmental future risks. Today, the Cd content of Sweden is reduced because of large export of Cd in zinc (Zn) concentrate (approximately 800 Mg Cd yr−1). Another large anthropogenic flow is the import of various secondary and consumer goods (approximately 100 Mg Cd yr−1). Today, the atmospheric deposition (16 Mg Cd yr−1) is nearly the same as diffuse consumption emissions (14 Mg Cd yr−1). Other anthropogenic discharges, such as industrial emissions to air and water, leachate from landfills, waste and storm water, have been reduced approximately one order of magnitude, since the late 1960s and early 1970s. The use of Cd and Cd‐contaminated primary goods (ores, metal concentrate, scrap etc.) have resulted in two large sinks within the Swedish society, one short‐term sink (Cd in serviceable products) and one long‐term sink (Cd accumulated in landfills). Since Cd outflows from existing landfills are much smaller than the inflows, the stored Cd is increased rapidly. Presently, these emissions are small on a regional scale, but the effects may be severe on the immediate surroundings.
Effects of Ozone and Water Deficit on Field‐Grown Soybean: II. Leaflet Nonstructural Carbohydrates
Authors: Miller Joseph E. , Vozzo Steven F. , Patterson Robert P. , Pursley Walter A. , Heagle Allen S.
Published: July 2010

Ozone (O3) and water deficit can suppress photosynthesis, growth, and yield of crops, and both may alter plant carbohydrate status. Little is known, however, concerning the combined effects of these stresses on C assimilation and nonstructural carbohydrate reserves in field‐grown plants. Soybean [Glycine max (L.) Merr. ‘Young’] plants were subjected to two soil moisture regimes (providing well‐watered and periodically water‐deficient conditions) and three levels of O3 in open‐top field chambers throughout the growing season. The O3 concentrations were 0.018, 0.059, and 0.085 µL L−1 (seasonal mean 12 h d−1 concentration). Leaflet carbohydrate concentrations were measured periodically during the growing season. Total soluble carbohydrates (TSCs) (sucrose and hexose) and starch were measured in the center leaflet of the sixth trifoliolate from the apex. Ozone stress suppressed leaflet concentrations of TSCs and starch on most sampling dates. Impacts of water deficit were less consistent, but starch concentrations usually increased when effects were significant. Interactions between the two stresses occurred infrequently, although water stress reduced the negative effects of O3 on sucrose and TSCs when the data were analyzed over the season. Ozone treatment also slightly increased the proportion of sucrose compared to starch in the total nonstructural carbohydrate (TNC) pool. The response of seasonal mean TNC concentrations, seasonal mean NCER, and seed yield to O3 followed similar patterns, although TNCs were suppressed more on a relative basis than NCER or yield.
Free‐Air Carbon Dioxide Enrichment of Cotton: Root Morphological Characteristics
Authors: Prior S. A. , Rogers H. H. , Runion G. B. , Kimball B. A. , Mauney J. R. , Lewin K. F. , Nagy J. , Hendrey G. R.
Published: July 2010

The response of plants to rising global CO2 concentration is of critical research interest but one neglected aspect is its effect on roots. Root morphological changes in cotton [Gossypium hirsutum (L.) ‘Delta Pine 77’] were examined in a 2‐yr field study. The test crop was grown under two water regimes (wet, 100% of evapotranspiration [ET] replaced and dry, 75% [1990] and 67% [1991] of ET replaced) and two atmospheric CO2 concentrations (ambient = 370 µmol mol−1 and free‐air CO2 enrichment [FACE] = 550 µmol mol−1). A FACE technique that allows for CO2 exposure under field conditions with minimal alteration of plant microclimate was used. Excavated root systems were partitioned into taproot and lateral roots at two growth phases (vegetative and reproductive). Vertical root‐pulling resistance was determined at the second sampling; this measure was higher because of CO2 enrichment but was unaffected by water stress. Water stress affected root variables only at the second sampling; water stress reduced taproot variables more than lateral variables. The larger diameter taproots seen at all sample dates under FACE exhibited large increases in dry weight and volume. FACE often increased lateral root number and lateral dry weights were higher at all sample dates. The development of more robust taproot systems in CO2‐enriched environments may allow for greater carbohydrate storage for utilization during periods such as boll filling and to ensure root growth for continued exploration of the soil profile to meet nutrient and water demands during peak demand periods.
Late Fall Site‐Specific Soil Nitrate Upper Limits for Groundwater Protection Purposes
Authors: Van Der Ploeg R. R. , Ringe H. , Machulla Galina
Published: July 2010

For temperate regions, such as Germany, a simple management model is developed, with which NO3 seepage losses during winter can be estimated, when the amount and distribution of soil NO3 in late fall are known. The semi‐analytical, one‐dimensional model is developed for homogeneous soils. The model is derived for steady‐state flow conditions at a constant soil water content (field capacity). Essential part of the model is a solute transport equation based on mixing‐cell theory. Sample calculations show that when the height Δz of the mixing‐cells is chosen such that Δz = 2D/v, where D is the soil dispersion coefficient and v is the pore water flow velocity, mixing‐cell model results compare well with results from convective‐dispersive models. The advantage of mixing‐cell models compared with convective‐dispersive models is that mixing‐cell model solutions frequently appear as simple mathematical expressions. With the model sample calculations concerning NO3 seepage losses during winter were carried out for a variety of site conditions. The calculations show that NO3 seepage losses vary considerably, even when the initial amount and the distribution of the soil NO3‐N are the same. The calculations also show that if a limit is set for the total amount of tolerable NO3 seepage losses during winter, site‐specific late fall upper limits for soil NO3‐N can be derived. A table of such values, for a wide range of site‐conditions, is presented.