bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenoloxidase‐Mediated Interactions of Phenols and Anilines with Humic Materials
Authors: Dec Jerzy , Bollag Jean‐Marc
Published: July 2010

Phenoloxidases present in terrestrial systems may contribute to the formation of humus through random coupling of a variety of aromatic compounds, including xenobiotic chemicals. Because of their structural similarity to natural substrates originating mainly from ligdin decomposition, xenobiotic phenols and anilines can be readily incorporated into the soil organic matter, a phenomenon referred to as binding. The underlying mechanism of binding involves oxidation of the xenobiotic substrates to free radicals or quinone products that subsequently couple directly to humus or to naturally occurring phenols that also are subject to oxidation. The oxidation can be mediated by soil phenoloxidases as well as by abiotic catalysts. The ability of the enzymes to mediate the oxidation was demonstrated in a number of model studies, in which selected pollutants were incubated with humic monomers or natural humic acids in the presence of different phenoloxidases (laccase, peroxidase, tyrosinase). Analysis of the formed complexes by mass spectrometry and 13C nuclear magnetic resonance (NMR) spectroscopy left no doubt about the formation of covalent bonds between the pollutants and humic materials. Some bonds were formed at the chlorinated sites, leading to partial dehalogenation of the aromatic contaminants. Experimental data indicated that bound phenols and anilines were unlikely to adversely affect the environment; their release from humic complexes by soil microorganisms was very limited and once released, they were subjected to mineralization. For those reasons, phenoloxidases, which proved capable of mediating the underlying reaction, are currently considered as a tool for enhancing immobilization phenomena in soil.
Enzyme‐Clay Interactions and Their Impact on Transformations of Natural and Anthropogenic Organic Compounds in Soil
Authors: Naidja A. , Huang P. M. , Bollag J.‐M.
Published: July 2010

Soil is a living system in which enzymes are present either free in solution or bound to clay and clay‐humus complexes. Enzyme‐clay interactions play a key role in transforming organic compounds in soil environments where the decomposition and synthetic processes are largely catalyzed by enzymes. Scientific evidence indicates that mineral colloids take part in the catalysis of degradative and synthetic reactions of organic compounds. Such information is essential to understanding the role of mineral colloids, the hidden half of the enzyme‐mineral colloid complexes, in catalytic reactions. Despite the abundant literature on the enzyme interactions with pure crystalline aluminosilicates, the nature of enzyme association with soil constituents, including both clean and coated clay minerals and other mineral colloids, and the effect on soil processes still remain unclear. This study integrates the existing information, including recent findings on enzyme‐mineral colloid interactions and their effect on natural and anthropogenic organic compound transformation in soil. Further, the study focuses on the catalytic role of enzyme‐clay complex surfaces in toxic industrial and agricultural compound bioremediation in soil and water environments.
Transformation of Chlorinated Hydrocarbons Using Aquocobalamin or Coenzyme F430 in Combination with Zero‐Valent Iron
Authors: Morra Matthew J. , Borek Vladimir , Koolpe Jonathan
Published: July 2010

More effective methods are necessary for the remediation of soils, sediments, and ground waters contaminated with halogenated organic compounds. Our objective was to determine the feasibility and utility of using a tetrapyrrole‐Fe(0) mixture for reductive dehalogenation of synthetic organic contaminants. Aquocobaiamin or coenzyme F430 was combined with Fe(0) in aqueous systems containing either a single chlorinated compound or mixtures of chlorinated compounds, and substrate disappearance was monitored using gas chromatography‐mass spectrometry (GC‐MS). Zero‐valent iron effectively dehalogenated CCl4 at low to neutral pH values, while increases in CCl4 dehalogenation resulting from inclusion of tetrapyrrole catalysts along with Fe(0) occurred only at basic pH values. Rates of CCl4 disappearance increased with additional aquocobalamin, but reached a maximum and decreased at higher aquocobalamin concentrations. Overall dehalogenation rates may thus be a function of Fe(0)'s limited reactive surface area. There was a trend for both tetrapyrrole catalysts to promote the disappearance of halogenated compounds in a mixed substrate containing 20 compounds. Studies with five individual substrates likewise showed trends for increased substrate removal with F430 beyond that for Fe(0) alone. This increase is most important for compounds such as 1,2‐dichloroethane and 1,4‐dichlorobenzene that are not readily dehalogenated by Fe(0). Chloride concentrations in the reaction mixtures indicated that reductive dehalogenation was the dominant process responsible for substrate disappearance. Use of a combination of aquocobalamin or coenzyme F430 and Fe(0) may effectively promote dehalogenation, thus producing fewer products and more complete dehalogenation of the target substrates than can be achieved using only one of the abiotic reductants alone.
Management and Crop Residue Influence Soil Aggregate Stability
Authors: Martens Dean A.
Published: July 2010

Soil management is one of the most important factors influencing the structure of soils. The interaction of management (including tillage and crop rotation history) with soil biochemistry, soil aggregation, and soil humus composition was determined in a native prairie and a producer field situation in 1997. A comparison of a native prairie and an adjacent conventional corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.] rotation on the same soil type found that the Webster soil (fine‐loamy, mixed, superactive, mesic Typic Endoaquoll) after soybean (C3 plant) was lower in monosaccharide content and protein content as determined by ion chromatography, and lower in phenolic acid content than the Webster soil after corn (C4 plant) or in native prairie as determined by gas chromatography. A wet, nested sieve aggregate stability measurement determined that the prairie soil had a higher mean aggregate size (1.85 mm) when compared with the soil in the presence of decomposing corn (1.0 mm) or soybean (0.34 mm) residues. Mean aggregate size was found to be correlated with soil monosaccharide content (r = 0.75), total soil protein content (r = 0.995***), total soil phenolic acid content (r = 0.997***), and alkaline extractable humic substance content (r = 0.98**). Alkaline extractable humic substances were correlated with the phenolic acid content of the humic substances (r = 0.996***). The results suggest that the decrease in soil stability after soybean growth was due to a decrease in the content of soil humic substances caused by the substantially lower phenolic acids content (humic acid precursors) in the soybean residue.
Ammonia Emission from a Large Mechanically‐Ventilated Swine Building during Warm Weather
Authors: Ni Ji‐Qin , Heber Albert J. , Lim Teng T. , Diehl Claude A. , Duggirala Ravi K. , Haymore Barry L. , Sutton Alan L.
Published: July 2010

Ammonia (NH3) emission from a grow‐finish swine (Sus scrofa) building with an underfloor manure storage pit was evaluated during warm weather from 26 June to 25 September. Average daily mean (ADM, covering all measurement days) outdoor temperature was 21.8°C. Ammonia concentrations, ventilation rates, and temperatures were continuously measured or recorded and 88 d of reliable data were obtained. Air samples were taken at wall and pit exhaust fans and in the pit headspace. The NH3 concentrations were monitored on‐site with a chemiluminescence NH3 analyzer. Ventilation rates were calculated based on operation of five wall fans, four pit fans, and the fan static pressure. The NH3 emission rates were calculated by multiplying simultaneously measured NH3 concentrations and ventilation rates of wall and pit exhaust fans. The ADM of building NH3 concentration (mean concentration of all sampling locations) was 3.9 mg m−1. The ADM building NH, emission (sum of the emissions from all ventilation fans) was 11.2 kg d−1, equivalent to 145 g d−1 per AU (animal unit = 500 kg animal weight). The ADM emission per AU was higher than other reported values, probably due to warmer temperatures and higher ventilation rates. The building NH3 concentrations were inversely proportional to the indoor temperatures (r = −0.66) and ventilation rates (r = −0.59) and correlated well to total pig weight (r = 0.49). The building NH3 emission rates were correlated to total pig weights (r = 0.52) and ventilation rates (r = 0.41) and were not well correlated to indoor temperatures (r = 0.12).
Binding of Mercury(II) to Reduced Sulfur in Soil Organic Matter along Upland‐Peat Soil Transects
Authors: Skyllberg Ulf , Xia Kang , Bloom Paul R. , Nater Edward A. , Bleam William F.
Published: July 2010

The binding of Hg2+ in organic matter of soils and waters controls the transport and transformations of Hg in terrestrial and aquatic ecosystems. We developed a competitive complexation method using the strong complexation of Hg2+ by Br− for determining the Hg2+ binding strength in organic soils at native and elevated Hg concentrations. The distribution coefficients determined in KBr suspensions for sorption of native Hg2+ to soil organic carbon (SOC) (KSOC) are in the range of 1022 to 1023. The KSOC significantly decreased with increased additions of Hg2+ and with decreasing pH. Using data for reduced organic S concentrations determined by x‐ray absorption near‐edge structure spectroscopy (XANES), we calculated surface complex formation constants on the order of 1032 for a model site having acidity constants of mercaptoacetic acid. This value is in fair agreement with the tabulated value of 10345 for Hg2+ binding in mercaptoacetic acid. At native Hg concentrations, formation constants and KSOC values were similar for different types of soil organic matter along transects from uplands into wetlands, despite varying concentrations of Hg and reduced organic S. Our adsorption data are consistent with the conclusions from our previous extended x‐ray absorption fine structure spectroscopy (EXAFS) study that in a humic acid and soil, Hg2+ ions bond in two‐fold coordination involving one reduced S and one O or N.
Long‐Term Changes in the Extractability and Bioavailability of Zinc and Cadmium after Sludge Application
Authors: McGrath S. P. , Zhao F. J. , Dunham S. J. , Crosland A. R. , Coleman K.
Published: July 2010

Changes in the extractability and uptake by crops of sludge metals in a long‐term field experiment, started in 1942, were measured to assess whether Zn and Cd are either fixed by the sludge/soil constituents or are released as the sludge organic matter (OM) decomposes. Total and 0.1 M CaCl2‐extractable concentrations of Zn and Cd in soil and total concentrations in crops were measured on archived crop and soil samples. Extractability of Zn as a proportion of the total ranged from 0.5 to 3% and that of Cd from 4 to 18%, and were higher in sludge‐amended than farmyard manure or fertilizer‐amended soils. Over a 23‐yr period after 1961, when sludge was last applied, the extractability of both metals fluctuated, but neither decreased or increased consistently. The relationships between total soil and crop metal concentrations were linear, with no evidence of a plateau across the range of soil metal concentrations achieved. The slopes of the soil‐plant relationships depended on the type of crop or crop part examined, but were generally in the order red beet (Beta vulgaris L.) > sugar beet (Beta vulgaris L.) > carrot (Daucus carota L.) > barley (Hordeum vulgare L.). However, there also were large seasonal differences in metal concentrations in the crops. It is concluded from the available evidence that up to 23 yr after sludge applications cease, Zn and Cd extractability and bioavailability do not decrease.
Duplicate Sampling of Surface Films and Associated Pond Water for Herbicides
Authors: Waite D. T. , Cessna A. J. , Grover R. , Woodsworth E. J.
Published: July 2010

This paper describes the variability of herbicide concentrations in the surface film and subsurface water of small, artificial prairie ponds (dugouts) as determined by comparing duplicate samples. Duplicate surface film samples were collected using a horizontally held glass plate and washed into a collection bottle with dichloromethane. Subsurface water samples were collected by plunging bottles into the pond to a depth of approximately 0.25 m. The samples were collected weekly from two dugouts in 1989 and from one dugout in 1990. Samples were analyzed for 2,4‐D, dicamba, bromoxynil, MCPA, triallate, trifluralin, and diclofop using a gas chromatograph interfaced with a mass selective detector. The average variability of the surface film samples was ±40% of the average of the pair with a confidence interval of 97% (p = 0.05). The average variability of the subsurface water samples was ±25% of the average of the pair with a confidence interval of 71% (p = 0.05). Possible reasons for the variability, including the nonhomogeneity of the surface film, are discussed.
Salinity, Boron, and Irrigated Pecan Productivity along New Mexico's Rio Grande Basin
Authors: Picchioni G. A. , Karaca H. , Boyse L. G. , McCaslin B. D. , Herrera E. A.
Published: July 2010

We surveyed 15 commercial irrigated orchards of ‘Western’ pecan [Carya illinoinensis (Wangenh.) K. Koch] along a 120‐km stretch of the middle Rio Grande basin in southern New Mexico. Our intent was to determine if high salinity and boron (B) broadly threaten pecan cultivation in this region. Ten of the fifteen sites were found to be on soils considered too saline for pecan trees (>2–3 dS m−1 in the soil saturation extract of the upper 0–60 cm of soil depth). Of these 10 sites, 4 had saturation extract Na concentration exceeding 20 mM, which is at or about the concentration corresponding to pecan seedling rootstock growth suppression. A laboratory study showed that cell membranes of excised, subapical seedling root segments from ‘Riverside’ pecan were damaged by about twice the salinity of the saturation extract at the highest salinity sites (9 dS m−1). At all sites, midsummer leaflet B concentration surpassed the published accepted range for pecan of about 50 to 100 mg B kg−1 dry weight, especially at the sites with higher soil salinity. Evaluation of two nearby sites (low salinity and B and high salinity and B orchards) showed that the higher salinity and B were associated with 25% lower yield efficiency, 3% lower percentage kernel, 13% lower mass per nut, and a 9 to 16% reduction in the tree's capacity to recycle N and P into perennial storage organs. The findings bring attention to the sustainability of current irrigation and soil management practices in much of this concentrated pecan producing region.
Nutrient and Fecal Coliform Discharge from Coastal North Carolina Golf Courses
Authors: Mallin Michael A. , Wheeler Tracey L.
Published: July 2010

Water quality investigations were conducted at five golf courses in southeastern North Carolina to determine levels of pollutants contributed by the courses to adjacent coastal streams. In general, nitrate levels were greater in streams leaving the courses compared with streams entering the courses, but concentrations varied considerably among courses. Ammonium concentrations increased in passage through most of the courses. Orthophosphate concentrations were elevated on midcourse sites on two courses, but were low in the outflow water except at one course. The golf courses studied were not significant sources of fecal coliform bacteria to nearby waterways; in fact, passage through some courses served to reduce coliform loads entering from upstream suburbs. Recent rainfall and fertilization application influenced outfall nitrate concentrations only at some courses. Landscape management practices appeared to play a critical role in determining nutrient concentrations in the outfall and at midcourse sites. Nutrient addition bioassay experiments conducted in one of the coastal creeks receiving golf course effluent demonstrated that nutrient concentrations as low as 50 to 100 µg nitrate N L−1 were capable of causing significant phytoplankton biomass increases. Nitrate levels in the outflow streams were at or above concentrations causing significant increases in phytoplankton biomass in our bioassay experiments. These coastal creeks host spring and summer algal blooms; thus, some golf course discharge nutrient concentrations are at levels great enough to contribute to eutrophication problems in estuarine waters. Vegetated buffer zones, wet detention ponds, and wooded wetland areas led to considerably lower nutrient output than sites lacking such management practices and should be used whenever possible to protect nutrient‐sensitive receiving waters.
Herbicide Application Method Effects on Napropamide Complexation with Dissolved Organic Matter
Authors: Nelson S. D. , Letey J. , Farmer W. J. , Williams C. F. , Ben‐Hur M.
Published: July 2010

Napropamide [2‐(α‐naphthoxy)‐N,N‐diethyl propionamide] has been shown to form soluble complexes with dissolved organic matter (DOM). Batch equilibrium and soil column leaching studies were performed to evaluate the effect of a drying event following herbicide application on napropamide‐DOM complex formation. Napropamide was applied directly to the soil and allowed to dry and compared with studies where the herbicide was not allowed to dry. In batch studies the presence of napropamide‐DOM complexes was inferred from reduced sorption coefficients measured on extracts of treated soils as compared with those from aqueous solutions. In column studies, drying was shown to induce herbicide movement with the wetting front even when preferential flow pathways were eliminated. The formation of napropamide‐DOM complexes was verified by dialysis tubing techniques. Increased napropamide movement through soil was the result of stable napropamide‐DOM complexes that lacked an adsorption affinity. Although less than 6% of the total herbicide applied moved by facilitated transport, this amount of rapidly mobile pesticide could significantly increase the potential for ground water contamination. Results suggest that preventing the applied herbicide solution from drying before irrigation could reduce or eliminate the threat of facilitated transport of napropamide by DOM. We suggest that a short irrigation period after herbicide application could allow for herbicide movement beyond the soil surface to deter drying while preventing deep movement of pesticide with the water front.
Water Dynamics and Nutrient Leaching through a Cropped Ferralsol in the Loyalty Islands (New Caledonia)
Authors: Duwig Céline , Becquer Thierry , Vogeler Iris , Vauclin Michel , Clothier Brent E.
Published: July 2010

On the South Pacific islands, the change from traditional to more intensive agricultural practices is leading to more fertilizer use, both extensively and intensively. Nutrient leaching should be minimized to avoid plant deficiencies and ground water pollution. The fate of nitrate and potassium under corn (Lea mays L.) and perennial grass (Rhodes grass, Chloris gayana Kunth.) was monitored during three wet seasons on a Ferralsol soil from Mare in the Loyalty Islands. In 1995,130 and 41% of the applied NO−3 and K+, respectively, leached beyond the root zone. Split application of the fertilizers in 1996 decreased the amounts leached to 48 and 11%, respectively. This reduction occurred even though the rainfall nearly doubled from 1995 to 1996. Nitrate and potassium transport, however, can be decreased due to their retention by this Ferralsol. Nitrate can be adsorbed on the positively charged surface of aluminum and ferric oxides. Due to the rapid drainage under tropical rainfall, however, this phenomenon is not very effective. Potassium is usually tightly fixed on 2:1 clay minerals, but these are nonexistent in our soil. Potassium also is bound to humic substances and the organic matter reaches 15% in the subsoil of this Ferralsol. Leaching of K+ was retarded compared with NO−3, but was still quite high compared with others studies on tropical soils.
Characterizing Kinetics of Sequential Selenium Transformation in Soil
Authors: Guo Lei , Jury William A. , Frankenberger William T. , Zhang YiQiang
Published: July 2010

The speciation of selenium (Se) in a Hanford sandy loam was measured as a function of time at two soil water contents under aerobic and anaerobic conditions to evaluate the kinetics of selenium transformation. The stepwise reaction coefficients describing sequential selenium transformation were determined using an inverse method based on a five‐compartment model that included selenate, selenite, elemental Se, organic Se, and gaseous Se as the major Se species (or fractions). Transformation of Se was less affected by soil water content at ≥21.5%, but was distinctively faster under anaerobic conditions where O2 was displaced with N2 gas. During the incubation period of 49 to 52 d, between 27.9 and 74.9% of the total selenium, initially present as selenate, was reduced to elemental or organic Se species. Although volatilization of Se required a reduced precursor, the rate of volatilization was not correlated to the rate of reduction. No volatilization of Se was detected under anaerobic conditions, suggesting that O2 was a critical factor controlling the methylation of Se, the reaction that converts nonvolatile Se species into gaseous forms.
Selenium Volatilization from a Soil—Plant System for the Remediation of Contaminated Water and Soil in the San Joaquin Valley
Authors: Lin Z.‐Q. , Schemenauer R. S. , Cervinka V. , Zayed A. , Lee A. , Terry N.
Published: July 2010

Selenium (Se) contamination of agricultural drainage water is a major environmental problem facing California agriculture. To demonstrate the potential effectiveness of biological volatilization in removing Se from contaminated water and soil, Se volatilization was determined under field conditions from a soil—plant (Salicornia bigelovii Torr.) treatment system in the San Joaquin Valley, California. Volatile Se was collected using an open‐flow sampling chamber system, biweekly during the S. bigelovii growing season from February to September 1997, and monthly from September 1997 to January 1998. The rate of Se volatilization fluctuated under different field conditions during the study year, with an overall mean of 155 ± 25 µg Se m−2 d−1. Biological volatilization removed 62 mg Se m−2 yr−1, which accounted for 6.5% of the annual total Se input (958 mg Se m−2 yr−1) to the S. bigelovii field. Forward trajectory analysis showed that the air mass that passed through the research area generally moved quickly out of the San Joaquin Valley within the first 24 h, probably transporting airborne Se from the research site toward the eastern Sierra Nevada in spring and fall, the southern mountainous areas in summer, and the Coast Mountain region in winter. This study suggests that biovolatilization represents an environmentally sound technology for managing Se‐contaminated soil and agricultural drainage water. Future research will focus on establishing new means for enhancing Se volatilization in the field.
Movement of Bromide, Nitrogen‐15, and Atrazine through Flooded Soils
Authors: Kelly Walton R. , Wilson Steven D.
Published: July 2010

In order to study the movement of agrichemicals in a flooded system under controlled conditions, we performed two tracer tests on a 3‐ by 8‐m plot that was deliberately flooded twice during the study: once in fall 1996 and again in fall 1997. Each test was monitored through the summer following flooding. Hydraulic head data continuously collected while the site was flooded indicate that a downward vertical hydraulic gradient predominated throughout the entire depth monitored (4.5 m), although there was also a horizontal gradient. Atrazine, bromide, and nitrate enriched in 15N were sprayed at the surface in the center of the plot prior to each flooding. Water samples were taken from multi‐level samplers to depths up to 4.6 m for tracer analysis seven times throughout the flooding cycle. The atrazine, bromide, and 15N moved rapidly after flooding, in a nearly vertical direction, greater than 4.5 m in less than 24 h. After 24 h, concentrations of the three applied chemicals decreased with time, 15N most rapidly and atrazine least rapidly. Most of the atrazine (65%) remained bound in the top 50 cm of soil, but the rapid movement of the dissolved atrazine indicates the potential for ground water contamination when flood events coincide with atrazine presence in soils. The presence of dissolved sulfide indicated suboxic conditions in the submerged soil, which were conducive to denitrification reactions, thus nitrate appears to be of less concern than atrazine.
Virus Transport through Saturated Sand Columns as Affected by Different Buffer Solutions
Authors: Chu Yanjie , Jin Yan , Yates Marylynn V.
Published: July 2010

To accurately examine the mechanisms that control virus retention and transport in porous media, it is essential to perform experiments under environmentally relevant conditions. Laboratory studies of virus transport are generally conducted using buffered solutions. However, there are no standards for the concentration and composition of the solution, making comparisons between different studies difficult. Our objective was to systematically investigate the effects of the ionic strength and composition of buffer solutions on adsorption of viruses during transport through saturated sand columns. Two phosphate buffered saline solutions (PBS and PBS2) and one artificial ground water (AGW) were used and experiments were conducted under saturated, steady state flow conditions. Bromide tracer and bacteriophages φX174 and MS‐2 were introduced into saturated sand columns as step inputs and their concentrations in the outflow samples were determined. Change in ionic strength did not affect the behavior of φX174, whereas MS‐2 was largely removed in the high ionic strength PBS buffer (0.16 M) but moved through the columns in the low ionic strength PBS2 and AGW buffers (0.002 2M). An additional experiment conducted under an ionic strength gradient (from 0.002 to 0.2 M) using PBS indicated that the outflow concentration of MS‐2 decreased slowly from an ionic strength of ∼0.03 M, reached a minimum at an apparent critical value of ∼0.1 M, and then increased gradually. This study also suggests that metals or metal oxides on sand surfaces can cause significant virus removal under high ionic strength conditions.
Watershed‐Level Uncertainties: Implications for Phosphorus Management and Eutrophication
Authors: Hession W. C. , Storm D. E.
Published: July 2010

Eutrophication is often the critical problem associated with surface waters having impaired water quality. Managing eutrophication in lakes and reservoirs typically involves the control of phosphorus inputs since it is often the limiting nutrient and because nitrogen and carbon are difficult to control. Management activities to address water quality impairment require a watershed‐level approach. However, uncertainty and stochasticity are ubiquitous in watershed‐level assessment and management. We describe and demonstrate a method for incorporating uncertainty analyses in watershed‐level modeling using Wister Lake in Oklahoma as an example. Natural stochasticity, parameter error, and error due to aggregation of data are quantified separately to allow for a comparison of the various sources of uncertainty in modeling activities. Parameter error was found to be the greatest contributor to overall output uncertainty. Several example management scenarios are presented to illustrate the utility and flexibility of including uncertainty quantification in watershed‐level management and decision making.
Fecal Bacteria in the Waters of an Upland Area in Derbyshire, England: The Influence of Agricultural Land Use
Authors: Hunter Colin , Perkins Joy , Tranter Jamie , Hardwick Paul
Published: July 2010

Long‐term data on the dynamics of sanitary indicator bacteria in fresh waters is limited. This paper provides a data record of fluctuations in fecal bacterial concentrations in the waters of an upland area of northern England that can be examined in relation to agricultural land use practices and standards for contact recreation. Concentrations of fecal coliforms (FCs) were monitored in the waters of semi‐improved sheep pasture on the edge of a limestone karst system in north Derbyshire, England for a 21‐mo period. Data were obtained for three small streams and six water inflows to streams, comprising the end points of shallow subsurface tile drainage networks and natural, semi‐permanent, channelized overland flows. All sites showed significant contamination by fecal indicator bacteria. A consistent pattern of seasonal FC concentration change was observed at all sites, with concentrations generally highest during the summer and lowest during the winter. This may be explained by land use factors, including higher summer sheep stocking densities and the application of farmyard manure and sewage sludge. Correlations between changes in bacterial concentration at inflow sites and downstream changes in streamwater concentration were generally highly significant, providing strong empirical evidence for the assumed causal relationship between inflow and streamwater quality. The degree of fecal bacterial contamination of the streams, particularly during summer months, may constitute a real health risk to recreational cavers using parts of the limestone karst system into which the streams drain.
Modeling of Sulfate Adsorption on Andisols for Implementation in the SAFE Model
Authors: Fumoto Tamon , Sverdrup Harald
Published: July 2010

Sulfate adsorption models were investigated in this study to simulate the pH dependence of SO2−4 and H+ adsorption on Andisols and thereby show the effects on acidification and recovery processes of Andisols. An extended constant capacitance model (ECCM), which assumed protonation of surface ‐OH groups and outer‐sphere complexation of SO2−4, proved valid to simulate SO2−4 and H+ adsorption on Andisols when evaluated using batch experiment data of SO2−4 and base cation adsorption at pH 4 to 5 and low ionic strengths. According to the ECCM calculation, SO2−4 adsorption was reproduced by an empirical equation using SO2−4 and H+ concentrations and H+ adsorption was approximated by another empirical equation using pH and SO2−4 adsorption. Since these two empirical equations are quite simple, they will be an efficient SO2−4 adsorption submodel in SAFE, the dynamic soil chemistry model to simulate the soil acidification and recovery processes.
Asymmetrical Distribution and Dissipation of Band‐Applied Atrazine in Soil
Authors: Dowdy R. H. , Dolan M. S. , Lamb J. A. , Koskinen W. C.
Published: July 2010

Movement of herbicides, particularly atrazine [2‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is of great interest, as farming systems are designed to protect water quality. The effects of time and precipitation on the distribution of atrazine banded over corn (Zea mays L.) rows were measured for 2 yr in a ridge‐tillage corn‐soybean [Glycine max (L.) Merr.] rotation. The soil was a Zimmerman fine sand (mixed, frigid Lamellic Udipsamment). During the growing season, soil atrazine was determined at 0.1‐m horizontal intervals perpendicular to the row to a depth of 0.3 m. Within the first 22 days after treatment (DAT), atrazine concentrations decreased 65% in the application zone and had not leached below 0.075 m. A 60‐mm rain between 22 and 29 DAT first moved atrazine into the 0.075‐ to 0.15‐m depth increment. By 60 DAT and 240 mm of accumulated rain, atrazine concentrations had decreased by an estimated 90% in the zone of application. Atrazine movement appeared to be greater on the windward side of the row. An estimated 98% of applied atrazine was dissipated by the end of the first growing season and by the end of the second year, detections of residual atrazine were very limited and confined to the zone directly below the treated area. Significant horizontal movement of atrazine was never observed. Atrazine was not detected in soil samples below 0.6 m to a depth of 2.4 m.
Removal of Atrazine and Deisopropylatrazine from Water by Montmorillonite‐Phosphate Crosslinked Compounds
Authors: González‐Pradas E. , Villafranca‐Sánchez M. , Del Rey‐Bueno F. , Ureña‐Amate M. D. , Fernández‐Pérez M.
Published: July 2010

To assess the potential use of two montmorillonite‐(cerium [Ce] or zirconium [Zr]) phosphate crosslinked compounds in removing organic pollutants from water, the adsorption of atrazine (6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine) and one of the major metabolites of atrazine in water, deisopropylatrazine (6‐chloro‐N4‐ethyl‐1,3,5‐triazine‐2,4‐diamine), has been studied at 25°C using batch experiments. The influence of the presence of 0.01 M KCl in the medium was also investigated for a better understanding of variables affecting the adsorption of these organic compounds. Experimental data points have been fitted to the Langmuir equation, with the results indicating a higher adsorption for deisopropylatrazine than for atrazine on both adsorbents in saline and nonsaline medium. Variation of the uptake of atrazine and the metabolite in the solution of 0.01 M KCl shows an enhanced adsorption of deisopropylatrazine on both samples compared w th that of atrazine. Fourier‐transformed infrared (FTIR) spectroscopic studies reveal that at the pH generated by the adsorbents (3.7 and 3.9 for Ce and Zr—montmorillonite compounds, respectively), atrazine and its metabolite interact with the surface of the adsorbents. X‐ray diffraction analysis showed that the compounds studied are intercalated into the adsorbents. For the compounds considered, the cerium—montmorillonite adsorbent shows a higher capacity of adsorption compared with zirconium—montmorillonite adsorbent, so it might be particularly useful in removing atrazine and, to a greater extent, deisopropylatrazine from water.
Mechanism of Degradation of Methyl Bromide and Propargyl Bromide in Soil
Authors: Papiernik Sharon K. , Gan Jianying , Yates Scott R.
Published: July 2010

The degradation of methyl bromide (MB) and propargyl bromide (PB) was investigated in soil and water to obtain information on the mechanism of degradation. It has been suggested that primary alkyl halides (including MB and the potential alternatives PB and methyl iodide) can undergo SN2 nucleophilic substitution with nucleophilic sites on soil organic matter (i.e., ‐NH2, ‐NH, ‐OH, ‐SH). The pattern of product formation observed in this study provides more direct evidence that fumigants that are primary alkyl halides can alkylate soil organic matter and that this may be a significant mechanism of degradation in soil. Degradation in water samples (hydrolysis) formed Br− and the corresponding alcohol (propargyl alcohol from PB, methanol from MB) in equimolar amounts. The rate of hydrolysis was not significantly different from the rate of Br− formation for both MB and PB. Degradation in two soils resulted in the formation of Br−, but very little production of the corresponding alcohol, indicating that some mechanism other than hydrolysis must be occurring in the soil. Degradation of MB and PB was much more rapid in the higher‐organic‐matter clay loam soil than in the sandy loam soil. Spiking 14C‐labeled MB to soil resulted in the formation of nonextractable (soil‐bound) 14C, which increased as the extractable 14C decreased. Microbial oxidation was not significant in these soil samples, which were sterilized through autoclaving and/or treatment with high concentrations of fumigants. These results provide further experimental evidence that MB, PB, and similar compounds can alkylate soil organic matter.
Strychnine Uptake by Cereals and Legumes Grown in the Glasshouse and Field
Authors: Oliver D. P. , Kookana R. S. , Rogers S. L. , Sinclair R. G. , Roberts G. , Cook C.
Published: July 2010

Strychnine‐coated wheat grain was used as bait in broad‐acre agriculture in Australia to control severe mouse damage during 1993 to 1995. To establish whether plants could take up strychnine, glasshouse experiments were conducted on wheat (Triticum aestivum L.), barley (Hordeum vulgare L), lupine (Lupinus angustifolius L.), pea (Pisum sativum L.) and faba‐bean (Vicia faba L.). Strychnine uptake was also determined by growing plants from germinated baits. In the glasshouse experiments strychnine was detected in lupine grain (<80–2500 µg kg−1) and in straw from wheat, barley, pea, faba‐bean, and lupine (<40–390 µg kg−1) when these plants were grown adjacent to 1 or 3 baits, equivalent to 36 to 107 times the recommended field rate, respectively. Strychnine was also detected in straw from the germinated baits (<40–2233 µg kg−1). Field experiments were then conducted to study strychnine uptake by wheat, barley, lupine, chickpea (Cicer arietinum L), pea, and canola (Brassica napus var. napus) under more realistic conditions. In the field strychnine was detected in only 3 samples of pea straw (10, 24, and 58 µg kg−1) where the bait was applied after flowering at eight times the recommended rate. This is probably due to bait lodging in the pea straw rather than from plant uptake of strychnine. The study has shown potential plant uptake of strychnine, but at the recommended rate of application under field conditions (3 baits m−2) it is unlikely that strychnine concentrations in the crops studied will exceed the detection limits (10–50 µg kg−1). Nevertheless, the existing programs monitoring strychnine levels in crops treated with baits should be maintained.
Hazards to Wildlife from Soil‐Borne Cadmium Reconsidered
Authors: Beyer W. Nelson
Published: July 2010

Cadmium is a toxic element that should be included in environmental risk assessments of contaminated soils. This paper argues, however, that hazards to wildlife from cadmium have often been overstated. The literature contains only meager evidence that wild animals have been seriously harmed by cadmium, even at severely contaminated sites. Although some researchers have reported that wildlife have accumulated concentrations of cadmium in their kidneys that were above suggested injury thresholds, the thresholds may be disputed, since they were well below the World Health Organization criterion of 200 mg/kg (wet weight) of cadmium in the renal cortex for protecting human health. Recent risk assessments have concluded that soil cadmium concentrations less than 1 mg/kg are toxic to soil organisms and wildlife, which implies that background concentrations of cadmium naturally found in soils are hazardous. An examination of the databases used to support these assessments suggested that the toxicity of cadmium has been exaggerated.
Temporal Stability of Spatial Patterns of Nitrous Oxide Fluxes from Sloping Grassland
Authors: Velthof G. L. , van Groenigen J. W. , Gebauer G. , Pietrzak S. , Jarvis S. C. , Pinto M. , Corré W. , Oenema O.
Published: July 2010

Insight into the temporal and spatial variability of nitrous oxide (N2O) fluxes from soils is required to set up efficient sampling protocols of N2O fluxes and to set up strategies to reduce N2O fluxes. The aim of the present study was to assess the temporal stability of the spatial pattern of N2O fluxes along a transect (400 m) on a fertilized sloping grassland soil. Geostatistical analyses of flux chamber measurements over 4 d showed a clear spatial dependency of N2O fluxes. The spatial variability of N2O fluxes was much higher than the temporal variability during the 4 d. Despite the decreasing magnitude of the fluxes in time, the spatial pattern persisted during 4 d, that is, fluxes were always highest at the steepest part of the transect. The 15N natural abundance (δ15N) in soil N was significantly correlated with N2O fluxes, indicating a long‐term effect of N loss as N2O on the 15N abundance in the soil. It was suggested that topography played a role in the observed spatial patterns of N2O fluxes and Δ15N in soil N. The study showed that despite the persistent spatial pattern of N2O fluxes, flux magnitude may strongly fluctuate in time. Therefore, it is often not possible to combine N2O flux measurements made at different times in order to obtain enough data for geostatistical analysis.
Nitrous Oxide Production from Urea Granules of Different Sizes
Authors: Tenuta Mario , Beauchamp Eric G.
Published: July 2010

Three laboratory experiments were conducted to determine if urea granule size or a high concentration of urea prills influence N2O production in soil. Urea hydrolysis results in a localized increase in soil pH and an increase in ammonia concentration. Such conditions may adversely affect the nitrification process, thereby increasing the N2O to NO−3 product ratio. Also, if anaerobic conditions should occur, the N2O to N2 product ratio during denitrification may increase. In general, under aerobic conditions, increasing the urea granule size from a powder to prill (commercial granules) and to larger granules resulted in increased N2O production. The increase in N2O production as granule size increased was accompanied by an increase in NO−2 concentration. The accumulation of NO−2 and the lower rates of disappearance of NH+4, or appearance of NO−3, indicated that the nitrification process was adversely affected. The appearance of N2O was delayed with increasing granule size. A high concentration of urea prills produced a similar but greater effect than large granules. The appearance and rapid production of N2O was closely related to the rapid disappearance of hydroxylamine and the presence of NO−2. The failure to detect hydroxylamine in urea granule‐treated soil may have been due to its rapid oxidation to N2O. The proportion of the added urea N transformed to N2O increased with granule size but did not exceed 1.24% of the urea added. A high concentration of urea prills resulted in 2.80% converted to N2O−N.
Effect of Competing Anions on the Adsorption of Arsenate and Arsenite by Ferrihydrite
Authors: Jain Amita , Loeppert Richard H.
Published: July 2010

The competitive adsorption of arsenate and arsenite and the effect of phosphate and sulfate on adsorption of arsenate and arsenite by ferrihydrite were investigated in the pH range of 3 to 10 and at varying initial ligand concentrations. In dual anion systems, arsenate retention was greater at low pH compared with greater arsenite retention at high pH. In systems with arsenate and arsenite concentrations ≤2.08 molAs kg−1fer each, the effect of arsenate on arsenite sorption was more pronounced than vice versa. On the contrary, at arsenate and arsenite concentrations of 3.47 molAs kg−1fer each, arsenate did not influence arsenite sorption but arsenite substantially reduced arsenate adsorption. The different sorption behavior of arsenite at low and high arsenite concentrations might be due to surface polymerization of adsorbed arsenite at high concentrations. The presence of phosphate resulted in a significant reduction in arsenate and arsenite adsorption by ferrihydrite, with strong dependence on pH and phosphate concentration. The effect of phosphate on arsenate adsorption was greater at high pH than at low pH, whereas the opposite trend was observed for arsenite. Results indicated that arsenate and phosphate compete for the same surface sites, with a moderate preference for arsenate adsorption. There was evidence of the presence of some surface sites that exhibited much higher affinity for arsenite than phosphate. The presence of sulfate did not influence arsenate adsorption but resulted in a considerable reduction in arsenite adsorption below pH 7.0, with the largest reduction at the lowest pH.
Operationally Defined Metal Fractions in Road Deposited Sediment, Honolulu, Hawaii
Authors: Sutherland R. A. , Tack F. M. G. , Tolosa C. A. , Verloo M. G.
Published: July 2010

Road deposited sediments (RDSs) in urban watersheds represent key storage areas for potentially contaminated materials and they are also the primary source of nonpoint pollutants entering aquatic systems. In addition to their association with degradation of stormwater quality, exposure to contaminated RDS has also been implicated in a variety of health issues, particularly among children. Limited data are available to characterize the geochemical properties of RDSs, specifically the association of metals with operationally defined solid fractions. To address this a new optimized four‐step (acid extractable [AEx], reducible, oxidizable, and residual) sequential extraction procedure was applied to 13 road sediments from an urban watershed in Oahu, Hawaii. Eight elements were examined (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) in the <2‐mm fraction. Data indicate that more than 50% of Al, Co, Fe, Mn, and Ni was associated with the residual fraction and reflects lithogenic‐pedogenic control. Of the three remaining trace metals that are considered to be anthropogenically enhanced, Cu was dominantly associated with the residual fraction (45%), followed by the oxidizable fraction (26%). Lead was primarily associated with the reducible fraction with a mean of 71%, a value among the highest so far reported in the literature. Zinc had only one‐fifth of its total concentration in the residual fraction, but one‐third in the most mobile and/or bioavailable fraction (AEx), which is susceptible to release into solution with decreases in pH.
Nitrogen‐15 and Bromide Tracers of Nitrogen Fertilizer Movement in Irrigated Wheat Production
Authors: Ottman M. J. , Tickes B. R. , Husman S. H.
Published: July 2010

In irrigated agricultural systems, NO3 leaching is believed to result from high fertilizer rates combined with the need to periodically leach salts from surface soil horizons. The purpose of this research is to estimate N fertilizer movement in the soil of commercial fields of flood‐irrigated wheat (Triticum spp.) while documenting best management practices (BMPs). Potassium bromide and 15N labeled ammonium sulfate were applied as tracers of N fertilizer movement to 1‐ × 1‐m microplots replicated 9 or 10 times in three commercial fields of flood‐irrigated wheat. The soil was sampled at harvest to a depth of 2.4 to 4.0 m. More fertilizer was applied at two out of three sites and more irrigation water was applied at all sites than recommended by BMPs. Bromide recovery in the soil and plant tissue at harvest was 29, 68, and 61% of that applied at the three sites. Most of the 15N measured in the soil profile was contained in the 0‐ to 0.3‐m increment of soil. Recovery on 15N in the soil and plant tissue at harvest was 54, 54, and 69% of that applied. The Br recovery data suggests that 32 ± 28% (standard deviation) of the 15N applied may have leached. The highest leaching potential was measured at the site that adhered to BMPs for N fertilizer management but had the most permeable soil. Nitrate leaching in flood‐irrigated wheat production seems inevitable even if BMPs for N fertilizer management are followed.