bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term RDX Sorption and Fate in Soil
Authors: Singh J. , Comfort S. D. , Hundal L. S. , Shea P. J.
Published: July 2010

Soils at former munitions production facilities are often contaminated with hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). Contamination can be excessive and soils often contain precipitated or solid‐phase RDX, resulting in soil solution concentrations at or near saturation. Sorption and long‐term fate must be understood to predict RDX availability and develop remediation strategies. We characterized RDX sorption and availability in Sharpsburg (a fine, montmorillontic, mesic Typic Argiudoll) surface soil by equilibrating the soil with 32 mg RDX L−1 (spiked with 14C‐labeled RDX) for 168 d; similar experiments were performed with contaminated and uncontaminated subsurface soils. Surface soils exhibited rapid RDX sorption with 34% of the 14C sorbed within 30 min. This sorbed fraction increased to only 37% at 168 d. During the 168‐d equilibration, readily available RDX (sorbed RDX extractable with 3 mM CaCl2) decreased from 75 to 52%, while potentially available RDX (acetonitrile‐extractable) increased from 24 to 32%. Carbon‐14 in the 0.5 M NaOH‐extractable organic matter fraction increased from 0.8 (T = 30 min) to 3.8% (T = 168 d). Little 14C was removed after eight extractions with 10% KOH in ethanol. Eight percent of the 14C‐label was unextractable (bound) residue at 168 d; no 14C‐bound residue formed in surface soil when solid‐phase RDX was present in the equilibrating solution. Our experiments indicated limited RDX sorption and transformation in the Sharpsburg surface and subsurface soils. Most of the sorbed 14C was potentially available for transport, indicating the importance of remediating RDX‐contaminated soil to protect groundwater quality.
Effects of Heavy Metal Contamination and Remediation on Soil Microbial Communities in the Vicinity of a Zinc Smelter
Authors: Kelly John J. , Tate Robert L.
Published: July 2010

Heavy metal contamination can impact soil ecosystems sufficiently to result in significant losses in soil quality. The negative impact of heavy metals results from their toxicity to biological processes, including processes catalyzed by soil microorganisms. Therefore, it is postulated that the soil microbial community could serve as an indicator of losses in soil quality due to heavy metal contamination and of changes in soil quality resulting from reclamation. In this study, the size, activity, and structure of microbial communities from remediated and unremediated soils in the vicinity of a Zn smelter were evaluated. Both total and soluble metal loadings in these soils increased with proximity to the smelter. Indicators of microbial activity (dehydrogenase activity) and viable population size (plate counts) were negatively affected by the elevated metal levels. Microbial community structure also varied with increasing contamination, as indicated by cluster analysis and principal component analysis of BIOLOG community metabolic profiles. Remediated soils at this site were treated by surface application of a mixture of sewage sludge and fly ash. Remediation resulted in a decrease in soluble metals and an increase in indicators of biological activity and viable population size. Remediated soils also showed metabolic profiles that were more similar to the least contaminated site, suggesting recovery of the microbial populations. These data suggest that the microbial community may be a useful indicator of changes in soil quality with management of these highly contaminated soils.
Salinity Trends in Surface Waters of the Upper Colorado River Basin, Colorado
Authors: Bauch Nancy J. , Spahr Norman E.
Published: July 2010

Dissolved‐solids data collected in the Upper Colorado River Basin upstream from Cameo, Colorado, and in the Gunnison River Basin were analyzed for trends in flow‐adjusted dissolved‐solids concentrations and loads for water years 1970 to 1993, 1980 to 1993, and 1986 to 1993. Trend results for flow‐adjusted periodic dissolved‐solids concentrations for the Colorado River Basin upstream from Cameo, CO, generally were downward or no trend was indicated. Trends in flow‐adjusted monthly and annual dissolved‐solids loads primarily were downward or absent. These trend results partly agree with the downward trends reported by a previous investigation for the Colorado River near Cameo site. In the Gunnison River Basin, trends in flow‐adjusted dissolved‐solids concentrations and loads were not detected for more than one‐half of the site/analysis‐period combinations. Of the trends that were present, most indicated decreases in concentrations and loads rather than increases. In both the Colorado River Basin upstream from Cameo, CO, and the Gunnison River Basin, trends in flow‐adjusted dissolved‐solids concentrations and flow‐adjusted monthly and annual dissolved‐solids loads may be affected by a variety of factors. These include channel evolution and hydrologic variation, water quality and flow rate of groundwater discharges and springs, sample size and period of record of dissolved‐solids data, and changes in land use in the basin.
Decreasing Nitrogen Leaching from Sandy Soil with Ammonium‐Loaded Clinoptilolite
Authors: Perrin T. S. , Boettinger J. L. , Drost D. T. , Norton J. M.
Published: July 2010

Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO−3) levels in surface and groundwaters. In this study, as a preface to a plant growth study, we compared N leaching from NH+4‐loaded clinoptilolite (A‐Cp) and (NH4)2SO4 (AS) in two media: a rounded quartz sand and a sandy soil. We hypothesized that quartz sand or soil amended with A‐Cp would leach significantly less N than these media amended with AS, and that more N would leach from smaller A‐Cp size fractions than from larger A‐Cp size fractions. Ammonium sulfate, or one of the three A‐Cp size fractions, small (<0.25 mm), medium (0.25–2 mm), or large (2–4 mm), was banded at a depth of 5 cm in leaching columns filled with inert quartz sand at a rate of 112, 224, or 336 kg N ha−1. The experiment was repeated with sandy soil in greenhouse pots at rates of 112 and 224 kg N ha−1. The columns and pots were leached for about 40 d with a simulated irrigation water. Significantly more N, as NH+4 and NO−3, leached from AS amendments than any of the A‐Cp amendments in both experiments. Results indicated that the larger the A‐Cp size fraction, the slower NH+4 is released from A‐Cp. Ammonium‐Cp slowly releases N and could significantly minimize N leaching from sandy soils compared to AS.
Field Evaluation of Calcium Sulfate as a Chemical Flocculant for Sedimentation Basins
Authors: Przepiora A. , Hesterberg D. , Parsons J. E. , Gilliam J. W. , Cassel D. K. , Faircloth W.
Published: July 2010

Sedimentation basins are built at construction sites to reduce the load of suspended solids in runoff water discharged into surface waters. However, these basins are not effective in reducing turbidity caused by fine suspended particles such as clay and silt. The objective of this field study was to evaluate the efficiency of moulding plaster (CaSO4 · 0.5 H2O) as a chemical flocculant for reducing the turbidity of water discharged from sedimentation basins equipped with a floating skimmer device. Following each of 14 rainfall events, sedimentation basins at two urban construction sites were either treated with moulding plaster or left untreated, and the turbidity and chemical properties of the impounded water and discharge water were monitored as the basins drained during a 50‐ to 70‐h time period. Each sedimentation basin was equipped with a floating skimmer device that discharged water at a controlled rate from 5‐cm below the surface of the impounded water. The turbidity of discharge water from untreated basins ranged from 100 to 1650 NTU (nephelometric turbidity units), while a surface‐applied moulding plaster treatment of 450 to 520 mg L−1 decreased the turbidity to <50 NTU. The time required for the discharge water from treated basins to reach either 100 NTU (2–20 h) or 50 NTU (5–52 h) was inversely proportional to the concentration of dissolved moulding plaster. Chemical flocculation using moulding plaster reduced the turbidity of discharge water to <50 NTU while producing dissolved SO4 concentrations of <250 mg L−1.
Interaction between Nitrous Oxide Formation and Methane Oxidation in Soils: Influence of Cation Exchange Phenomena
Authors: De Visscher Alex , Boeckx Pascal , Van Cleemput Oswald
Published: July 2010

Ammonium (NH+) inhibits the microbial oxidation of methane (CH4), and gives rise to the formation of nitrous oxide (N2O) in aerobic soils. However, the NH+4 concentration in the soil water is not necessarily proportional to the total NH+4 concentration in the soil, due to cation exchange or fixation phenomena. It was found that introducing the concept of ion exchange or fixation in kinetic models on CH4 consumption and N2O formation can increase our knowledge on these processes in soils. A fit of these kinetic models with experimental data showed a standard deviation of slightly more than 10%. The effects of NH+4 on CH4 oxidation and N2O formation can only be compared in soils with the same cation exchange capacity (CEC).
Microbial‐Mediated Reduction of Perchlorate in Groundwater
Authors: Herman David C. , Frankenberger William T.
Published: July 2010

Perchlorate has been widely used as a propellant in solid rocket fuel, and has recently been identified as a contaminant in both groundwater and surface waters. Perchlorate is recognized by the U.S. Environmental Protection Agency (USEPA) as a potential health risk, and the State of California has set a drinking water action level of 18 µg L−1. Incidents of groundwater contamination have been associated with industrial sites in California and Nevada that have been involved in the manufacturing or testing of solid rocket propellants. Microorganisms have been shown to be capable of reducing perchlorate (Cl O−4) to chloride (Cl−) and oxygen, thus transforming perchlorate into innocuous end‐products. Bioreactor processes for the remediation of perchlorate contaminated wastewater have previously been established. However, these systems were optimized for perchlorate concentrations in the grams per liter range, while groundwater contamination can be a million‐fold lower but still exceed the water quality action level. This literature review will focus on microbial‐mediated perchlorate reduction, and discuss issues of importance to the remediation of perchlorate‐contaminated groundwater.
Inorganic and Suspended/Dissolved‐Organic Nitrogen in Sierra Nevada Soil Core Leachates
Authors: Marcus J.A. , Miller W.W. , Blank R. R.
Published: July 2010

Watershed disturbance has been suggested as a possible mechanism for accelerated nutrient input into Lake Tahoe, California/Nevada. However, little is known regarding how nutrient discharge is coupled to physicochemical watershed processes. Recent investigations in the Lake Tahoe Basin have suggested that suspended/dissolved‐organic nutrient transport may play an important role in lake and tributary water quality. The mobility of inorganic and suspended/dissolved‐organic N in soils of a Lake Tahoe watershed was assessed using constant head permeameter leaching experiments with intact soil cores. We evaluated the interaction of plot condition (riparian, nonforested, and forested) and soil depth (0–15 and 15–30 cm) on magnitude and form of N discharge. Incremental leachate discharge was analyzed for concentrations of inorganic (NH4‐N and NO3‐N) and suspended/dissolved‐organic N. Leachate from the riparian soil cores had significantly higher (P < 0.05) concentrations and total discharge NO3‐N than that from the nonforested or forested areas. Loading of NH4‐N was more consistent among vegetative cover types, but the riparian leachate again contributed a significantly (P < 0.05) greater amount. Suspended/dissolved‐organic N was mobile and the most dominant form of N for nonforested and forested soil cores with discharge loading ratios (suspended/dissolved‐organic:inorganic) of 17:1 and 7:1, respectively. Although the loading ratio was approximately 1:1 for the riparian soil cores, the amount of suspended/dissolved‐organic N discharged was greatest. The mobility and presence of significant amounts of suspended/dissolved‐organic N indicate that this once unrecognized nutrient form is an important component in at least one Sierra Nevada watershed, and should be more fully investigated elsewhere.
Assessment of the Folin and Ciocalteu's Method for Determining Soil Phenolic Carbon
Authors: Ohno Tsutomu , First Paul R.
Published: July 2010

Previous studies have shown that phenolic compounds are potentially allelopathic and present at low concentrations in soil solution. This study was conducted to evaluate the Folin and Ciocalteu's method for determining concentrations of phenolic C in aqueous and citrate extracts of soils containing 7.1 to 57.9 g kg−1 organic C. Soils were reacted for 18 h with a 0.3 mM phenolic acid mixture or DI‐H2O to serve as a control. Folin and Ciocalteu's reactive‐phenolic C content in the DI‐H2O control extracts suggested positive interference from dissolved organic matter rather than free phenolic compounds desorbed from the native soils. The absorptivity of the Folin and Ciocalteu's reduced complex was 1128 ± 25 L mol−1 cm−1 for the phenolic acid mixture and 45 ± 8 L mol−1 cm−1 for soluble organic matter ligands. Although the method has much higher sensitivity to phenolic acids than to organic matter, the higher concentration of organic matter results in substantial background positive interference. However, multiple regression equations of corrected Folin and Ciocalteu's absorbance (phenolic‐treated absorbance minus deionized water control absorbance) regressed with solution parameters had excellent fits (R2 > 0.97). This suggests that interference correction is possible in aqueous extracts. The Folin and Ciocalteu's reactive‐phenolic C concentration in the citrate extracts of the phenolic acid mixture‐amended soils were not significantly different from the DI‐H2O control soil extracts indicating that the Folin and Ciocalteu's method is not suitable for use with soil citrate extractions. The large quantity of organic matter extracted by citrate probably masks absorbance due to any extracted phenolic compounds.
Treatment of Dilute Piggery Effluent with Vertical Flow Reed Beds
Authors: Parkes M. E. , McBride A. D. , Waalkens A.
Published: July 2010

Washwater from pig pens was led from a lagoon and treated in a series of vertical flow reed beds over 2 yr. A recirculation component was added in the second yr. Five‐day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), ammonium‐N (NH4‐N), and nitrate‐N (NO3‐N) were measured during the late winter/early spring periods for the 2 yr. Values of KBoD, to describe performance of horizontal flow reed beds, were determined for the vertical flow beds and compared with values derived from the literature. Maximum BOD5 removal was 96%, but averaged 65 and 61% over the first and second year periods, respectively. Performance of each stage, as indicated by percent removal of BOD5, was best described by an inverse logarithmic function of hydraulic load. Ponding was a problem, indicating a need for control of organic loading. Efficient nitrification was not achieved so that the treatment did not result in waste suitable for direct discharge to surface water.
Temperature Effect on Methyl Bromide Volatilization: Permeability of Plastic Cover Films
Authors: Wang Dong , Yates S. R. , Jury W. A.
Published: July 2010

Conventional methods of applying methyl bromide (MeBr) for soil fumigation can result in significant losses to the atmosphere, potentially contributing to the depletion of stratospheric ozone. It has been found that one of the major factors controlling MeBr volatilization is the permeability of the plastic cover films. Since the most commonly used agricultural film (i.e., polyethylene or PE) is not effective in containing MeBr, one practical method of reducing MeBr volatilization is to replace the PE film with one that is less permeable to MeBr. In this study, we document the temperature‐dependent permeability of standard PE and a new plastic film (Hytibar) that is considered to be virtually impermeable to MeBr. Functional relationships between temperature and the film permeability to MeBr were obtained from a calibration experiment under controlled conditions. A field experiment was conducted to determine MeBr volatilization dynamics from plots covered with the two different plastic films. diffusion‐based transport model was used to simulate the fate and transport of MeBr gas in the soil and volatilization into the atmosphere. In both the calibration and field experiment, the Hytibar film was found to be nearly impermeable to MeBr. Volatilization of MeBr was affected directly by temperature changes of the PE or Hytibar film in the calibration experiment. Under field conditions, MeBr emission was less affected by temperature, especially at large times after application. Model simulation predicted MeBr volatilization reasonably well for the PE covered field plot, but overpredicted the emission for the Hytibar plot.
Potential Sediment Denitrification Rates in Estuaries of Northern Gulf of Mexico
Authors: Flemer David A. , Lores Emile M. , Bundrick Charles M.
Published: July 2010

The three‐season average of sediment potential denitrification rates (PDRs) (i.e., NO−3 saturated; acetylene blockage method) for five study areas within urban bayous and bays in the Pensacola Bay area, Florida, ranged between 43 and 223 nmol of N g−1 h−1. Average PDRs extrapolated to a unit area basis approximated 500 to 1000 µmol of N m−2 h−1 that are relatively high values but comparable to those where conditions for denitrification are favorable. A regression model, based on a larger number of measured environmental factors for the spring than fall and winter indicated that NO−2 + NO−3 concentrations explained most of the total variability (R2: 27%; P < 0.003) in PDRs. The NO−2 + NO−3 concentrations were also predictive of PDRs (R2 ranged from 0.56–0.98; all P‐values <0.05) on four separate occasions for comparisons made within five study areas and three seasons. Sediment trace metal concentrations (e.g., Ni), based on published values, were high enough to cause reduction in PDRs through direct toxicity to denitrifiers at several stations. Sediment metals toxicities, based on published sediment quality guidelines, could occasionally cause a reduction in macrobenthic infaunal bioturbation and irrigation. Such a reduction could attenuate the flux of dissolved oxygen into sediments and cause a reduction in denitrification rates by limiting the coupled processes of nitrification and denitrification. Also, a reduction in the flux of NO−2 or NO−3, a substrate for denitrification, into sediments can directly limit denitrification rates.
The Quantitative Analysis of Sugar Maple Tree Rings by Laser Ablation in Conjunction with ICP‐MS
Authors: Watmough Shaun A. , Hutchinson Thomas C. , Evans R. Douglas
Published: July 2010

This study reports on the quantitative analysis of sugar maple (Acer saccharum Marsh.) tree rings by laser‐ablation ICP‐MS (LAS). Differences in ablation were corrected using 13C as an internal standard. Spatial variation in element distribution within individual tree rings was low, allowing individual tree rings to be used as calibration standards. The relative standard deviation (RSD) for element concentrations within tree rings were 15% for Mg, 15% for Ca, 9% for K, and 16% for Pb. This variation is likely due to element distribution and not the ablation process; the RSD for 13C was <4%. Tree cores were taken from three sugar maple trees adjacent to a major highway, 24 km east of Toronto. Concentrations of Ca, Mg, and K generally declined from pith to cambium, a feature commonly observed in tree boles. Peaks in Pb concentration, between 3 and 5 mg Pb kg−1, were found in tree rings formed between 1940 and 1970, although there was considerable year‐to‐year variation within each tree, and the timing and magnitude of the Pb peaks differed between trees. Lead concentrations decreased in wood formed after 1970 so that by the 1980s, Pb concentrations were around 1 mg kg−1, reflecting changes in Pb deposition into the woodland.
Controls on Fluxes of Trace Gases from Brazilian Cerrado Soils
Authors: Cofman Anderson Iris , Poth Mark A.
Published: July 2010

Tropical ecosystems play an important role in production or consumption of atmospheric trace gases including nitric oxide (NO), nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4). Here we describe field and laboratory experiments, performed during 1994, to determine the influence of fire on processes responsible for fluxes of gases from cerrado sites burned 17 and 45 d earlier, and a control site, last burned in 1974. Burning stimulated gross N mineralization but depressed nitrification rates; however, rates were sufficient to support NO fluxes observed in a 1992 study at the same site. Extractable nutrients and fluxes of NO and N2O from wetted and dry soils were measured prior to and for a 3‐d period following burning. Over this period NO2− declined to undetectable levels; NH+4 increased, and NO fluxes remained relatively constant, suggesting that nitrifiers replaced the NO2− reduced to NO. Soils at burned and unburned sites exhibited CH4 uptake, which was inhibited by CH3F, thereby converting soils from a strong sink to a weak source of CH4. Carbon dioxide fluxes did not increase, and there were no detectable fluxes of N2O following burning. In lab studies NO and N2O emissions were inhibited by autoclaving, suggesting that nitrification was key to their production. However, addition of NO2− to autoclaved soil resulted in large fluxes of NO but no detectable N2O, suggesting that chemodenitrification may have been responsible for NO but not N2O production. Further research is needed to determine whether NO is produced directly by nitrifier NO2− reduction or indirectly by chemodenitrification of NO2− produced by nitrifiers.
Selenium Uptake by Plants from Soils Amended with Inorganic and Organic Materials
Authors: Ajwa H. A. , Bañuelos G. S. , Mayland H. F.
Published: July 2010

Depending on its concentration and chemical form, Se functions as an essential element or potential toxicant to humans, livestock, and waterfowl. Application of seleniferous organic materials to soils may increase plant‐available Se content and pose health hazards. This study assessed Se uptake by two successive plantings of canola (Brassica napus cv. Westar) and multiple clippings of tall fescue (Festuca arundinacea L. cv. Fawn) grown in soils [Hanford sandy loam (coarse‐loamy, mixed, thermic Typic Durixeralfs) and Panoche clay loam (fine‐loamy, mixed, superactive, thermic Typic Torriorthents)] amended with 1.5 mg Se kg−1 soil as inorganic selenate (Se O42−) or seleniferous organic materials [alfalfa (Medicago sativa L.), Astragalus praelongus, or cattle (Bos tauris) manure] under growth chamber conditions. Tissues of canola and tall fescue accumulated much greater concentrations of Se from the inorganic SeO42− treatment compared to the treatments with seleniferous organic materials. The addition of crop residue or animal manure to the SeO42−‐treated soils considerably reduced Se accumulation by both plant species. In soils amended with seleniferous organic materials, more than 80% of the Se remained in soils after two plantings of canola and all clippings of tall fescue. The slow release of plant‐available Se in soils amended with seleniferous organic materials suggests the use of these materials to control the concentrations of Se in crops grown on nonseleniferous soils.
Sewage Sludge and Mycorrhizal Effects on Secar Bluebunch Wheatgrass in Mine Spoil
Authors: Thorne M. E. , Zamora B. A. , Kennedy A. C.
Published: July 2010

Establishing vegetation on mine spoil often requires amendments to supply nutrients and microorganisms to re‐establish attributes associated with developed soil. Arbuscular‐mycorrhizal fungi (AMF) and composted sewage sludge (CSS) were evaluated as possible minespoil amendments to create a topsoil substitute for revegetation of the Midnite Mine, Stevens County, Washington. Most original topsoil was buried and existing spoil is low in nutrients and organic matter and not capable of supporting desired vegetation. Secar bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Love × Elymus lanceolatus ssp. lanceolatus (Scribn. & J.G. Sm.) Gould] was grown in nonsterile spoil amended with 0.0, 6.2, 12.4, 24.5, and 49.0 g dry CSS per liter of spoil‐sand mix for 16 wk in a glasshouse experiment. Arbuscular‐mycorrhizal fungi treatments were spores of Glomus mosseae [(Nicol. & Gerd.) Gerdemann & Trappe] collected from native bluebunch wheatgrass plants, non‐native spores of Glomus intraradices (Schenck & Smith) and Entrophaspora sp. (Ames & Schneider), or no added spores. In addition, Secar was grown in nonsterile, stockpiled topsoil with both AMF treatments to compare to AMF present in the topsoil. Each CSS rate increase produced increased above‐ground and belowground plant growth. Secar growth was enhanced by native AMF in CSS‐amended spoil. Composted sewage sludge appeared to reduce AMF colonization; however, hyphae levels in plants with native AMF were unaffected. Plant growth was not affected by AMF treatments in stockpiled topsoil but AMF colonization was greater in plants with the topsoil alone. Benefits from CSS and selection of an effective AMF culture are evident.
Mineralization of Norflurazon in a Cranberry Bog Soil: Laboratory Evaluations of Management Practices
Authors: Savin Mary C. , Amador José A.
Published: July 2010

Norflurazon (4‐cldoro‐5‐(methylamino)‐2‐(α,α,α‐trifluoro‐m‐tolyl‐3(2H)‐pyridazinone) is a pre‐emergent herbicide used in cranberry (Vaccinium macrocarpon Air.) cultivation to control annual grasses, sedges, and broadleaf weeds. Cranberries are an economically important crop in New England, Wisconsin, and other parts of the northern USA. The biodegradation of norflurazon in the high organic matter, acidic soil characteristic of cranberry bogs has been shown to proceed slowly (Savin and Amador, 1998). The potential effects of cranberry cultivation practices—soil moisture control, fertilization, sand addition, and herbicide application rate—on mineralization of norflurazon in a bog soil were evaluated in a laboratory study. Optimal soil moisture for norflurazon mineralization was between 80 and 90% of water‐holding capacity (WHC) in soil from the Oi and A horizons. Saturating the soil reduced the rate of norflurazon mineralization significantly. By contrast, soil respiration was maximal at 25% of WHC in both horizons. Addition of inorganic P increased soil respiration, but did not affect norflurazon mineralization significantly. Addition of inorganic N plus P increased soil respiration in the A, but not Oi, horizon and significantly decreased norflurazon mineralization in the Oi horizon. Sand addition had no significant effect on norflurazon mineralization. Mineralization was affected by herbicide application rate, with the rate of mineralization increasing proportionally with increasing concentration from 0.75 to 7.5 mg norflurazon kg−1 soil. The mineralization of 14C‐norflurazon was slow for all of the agronomic practices evaluated, indicating that the potential for norflurazon to accumulate in cranberry bog soils may be high.
Decreases in Soil Microbial Function and Functional Diversity in Response to Depleted Uranium
Authors: Meyer Michael C. , Paschke Mark W. , McLendon Terry , Price David
Published: July 2010

A soil microcosm experiment was used to analyze effects of depleted uranium (DU) on soil function, and the concomitant changes in bacterial functional diversity. Uranium treatment levels were 0, 50, 500, 5000, 10 000, and 25 000 mg DU kg−1 soil. Three measures of soil function were made. Overall soil biological activity was assessed via measurement of soil respiration. Decomposition was assessed by measurement of mass loss of four different plant litter types: wood sticks, cellulose paper, high‐N grass, and low‐N grass. Mineral N availability in the microcosms was estimated using ion‐exchange resin bags. Functional diversity of the microcosms was analyzed through the use of the Biolog‐system of sole‐C‐utilization patterns. Soil respiration was the most sensitive measure of functional changes, with significant decreases observed starting at the 500 mg kg−1 treatment. No differences in N availability were observed across the U treatments. Litter decomposition was significantly decreased (P < 0.05) at the 25 000 mg kg−1 level relative to the control for all litter types except the high‐N grass. Wood decomposition was reduced by 84% at the 25 000 mg kg−1 treatment, cellulose paper by 68%, and low‐N grass by 15%. Decreases in the functional diversity of the bacterial community were related to the observed decrease in soil respiration, and to the greater effect on decomposition of the lower‐quality litter types.
Atrazine Interactions with Soil Humic Substances of Different Molecular Structure
Authors: Piccolo Alessandro , Conte Pellegrino , Scheunert Irene , Paci Maurizio
Published: July 2010

The mode of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] adsorption to humic substances is still uncertain, mainly because of the large heterogeneity of humus and its poor molecular characterization. In this study, four humic fractions were isolated from a peat and a volcanic soil by three different extraction mechanisms: charge repulsion (NaOH extraction), ligand exchange (pyrophosphate extraction, Na4P2O7), and hydrogen‐bonding disruption (extractions by aqueous mixture of acetone and dymethyl sulphoxide, DMSO). These four humic fractions showed consistent differences in molecular structure between the two soils. Humic fractions extracted by acetone had the largest content of aliphatic C, whereas those obtained by the pyrophosphate solution were richest in aromatic C. Sorption isotherms of 14C‐labeled atrazine conducted on the four humic fractions showed that, for both soils, the order of adsorption was acetone > NaOH > DMSO > Na4P2O7, whereas the order for desorption was the reverse. The relation between results of atrazine interaction and the molecular structure of humic matter indicates that the aliphatic C content of soil organic matter may be one of the parameters controlling atrazine adsorption to soils. Hydrophobic interactions and conformational flexibility in the aliphatic portions of humic matter controlled the adsorption of atrazine in the interior of humic self‐associated aggregates and the degree of desorption found both in water and methanol. Conversely, the conformational rigidity conferred to humic fractions by a large content of aromatic moieties appeared conducive only to surface adsorption and thus to easier herbicide desorption.
Distribution of Organochlorine Insecticides in Rivers of the Russian Federation
Authors: Zhulidov Alexander V. , Headley John V. , Pavlov Dmitriy F. , Robarts Richard D. , Korotova Larisa G. , Fadeev Valery V. , Zhulidova Olga V. , Volovik Yegor , Khlobystov Vladimir
Published: July 2010

There is a lack of information on organochlorine pesticides (OCPs) in waters of Russian rivers. This hampers evaluation of the transboundary transport. Studies were undertaken from 1988 to 1994 to: (i) characterize the levels and geographical distribution of OCPs in major Russian river basins, and (ii) determine trends in temporal dynamics of the waterborne contaminants. Russian rivers were contaminated by OCPs to an extent similar to that found in many countries one to two decades earlier. γ‐HCCH (1,2,3,4,5,6‐hexachlorocyclohexane) was the most widespread pesticide, followed by α‐HCCH, DHC (2,4,5,6,7,8,8‐heptachlor 4,7‐endo‐methylbicyclo [4,3,0]‐5‐nonene), HCB (hexachlorobenzene), DOT (1,1‐di (4′‐chlorphenyl)‐2,2,2‐trichlorethane), β‐HCCH, DDE (1,1‐di (4′‐chlorphenyl)‐2,2‐dichlorethylene), and DDD (1,1‐di (4′‐chlorphenyl)‐2,2‐dichlorethylene) based on data from the State Network of Environmental Monitoring (SNEM). Concentrations seldom exceeded maximum allowable concentrations (MACs) and mean concentrations met National Russian ambient water quality criteria. Highest exceedence (expressed as a percentage of the number of water samples) of the MAC occurred for γ‐HCCH (19%) and α‐HCCH (17.3%), with lower exceedences observed for DOT (4.3%), DDE (1.3%), and DDD (0.2%). Complementary observations were made using established QA/QC protocols. The latter studies showed that much lower exceedences had occurred: γ‐HCCH (2.4%), DDT (2.1%), α‐HCCH (2.0%), with negligibly low exceedences observed for DDE (0.4%), β‐HCCH (0.3%), and DDD (0.1%). In general, levels of OCPs in Russian inland water during 1991 to 1993 was similar to that found in Western countries a decade earlier.
Evaluating Management and Soil and Weather Contributions to Potential Nitrate Leaching from a Pennsylvania Dairy Farm using NLEAP
Authors: Saporito L. S. , Lanyon L. E.
Published: July 2010

Developing approaches to reduce nitrate‐N (NO3‐N) leaching from farms requires an understanding of the factors influencing the potential for NO3‐N leaching. An annual screening analysis, NLEAP, was used to determine NO3‐N leaching potential (NL) from a 110‐ha mixed crop and dairy farm in a central Pennsylvania limestone valley for each of 9 yr. The farmer management goal was to meet the animal and crop needs as much as posssible with internal farm resources. Nitrate‐N leaching potential was estimated from annual field N balances (NAL) and a yearly soil and weather factor (SWF) based on winter and summer rainfall, soil bulk density, rooting depth, and soil hydrologic group. Primary crops grown were corn (Zea mays L) and alfalfa‐timothy (Medicago sativa L.‐Phleum pratense L.). A geographic information system was used to calculate and map SWF, NAL, and NL The magnitutude and aerial distribution of field SWF was significantly different (Kolomogorov‐Smirnov, D‐max, p = 0.05) for most year‐to‐year comparisons. The excess of N inputs over outputs (field NAL) was low for all fields and did not vary significantly during the 9‐yr period. The NL was <25 kg ha−1 for 75% of the farm and <50 kg ha−1 for 85% of the farm for all years of the study. The careful and conservative N management strategy by the farmer, reflected in the consistently low NAL, had an overriding impact on potential NO3‐N leaching from the farm.
Corn Yield, Runoff, and Sediment Losses from Manure and Tillage Systems
Authors: Ginting D. , Moncrief J. F. , Gupta S. C. , Evans S. D.
Published: July 2010

One challenge in land application of manure is to maximize its benefit to crops without harming the environment. Our objective was to evaluate the impact of manure addition on corn yield, and sediment losses in snowmelt and rainfall runoff under moldboard plow (MP) and ridge tillage (RT) systems. Corn (Zea mays L.) grain yield and sediment losses in surface runoff after a one‐time spring application of (16.2 dry Mg ha−1) solid beef (Bos taurus) manure on a 12% slope Forman (fine‐loamy, mixed Udic Argiborolls)‐Buse (fine‐loamy, mixed Udorthentic Haploborolls) complex were measured from 1992 through 1994. In 1993, there was no effect of manure on grain yield irrespective of tillage because of high rainfall. Under average rainfall conditions in 1994, grain yield (10.2 Mg ha−1) in the manure RT treatment was 1.0, 0.9, and 0.7 Mg ha−1 greater than that in no‐manure RT, manure MP, and no‐manure MP treatments, respectively. Snowmelt runoff was not affected by manure application and it transported <0.1 Mg sediment ha−1. Manure reduced rainfall runoff by 10 mm in 1993 and 3.2 mm in 1994, which led to reduction in sediment loss of 2.5 and 0.2 Mg ha−1, respectively. The RT system resulted in lower rainfall runoff compared with the MP system for all 3 yr. Onetime manure application reduced rainfall runoff and associated sediment loss in both tillage systems. However, manure application was more effective in minimizing runoff and sediment losses during intense rainfall in the RT than in the MP system.
Degradation and Side Effects of Three Sulfonylurea Herbicides in Soil
Authors: Dinelli Giovanni , Vicari Alberto , Accinelli Cesare
Published: July 2010

Soil degradation and side effects of triasulfuron [3‐(6‐methoxy‐4‐methyl‐1,3,5‐triazin‐2‐yl)‐1‐(2‐(2‐chloroethoxy) phenylsulfonyl)‐urea],primisulfuron methyl [2‐(4,6‐bis(difluoromethoxy)‐pyrimidin‐2‐ylcarbamoylsulfamoyl)benzoic acid], and rimsulfuron [1‐(4,6‐dimethoxypyrimidin‐2‐yl)‐3‐(3‐ethylsulfonyl‐2‐pyridylsuifonyl)‐urea] were investigated under laboratory conditions in a pH 6.5 sandy loam soil. In microbially active and sterile soil, the degradation of the three sulfonylureas followed first‐order kinetics and was independent of the herbicide soil concentration up to 5 mg a.i. kg−1 of soil. In microbially active soil the mean half‐lives of triasulfuron (26.2 d), primisulfuron methyl (30.2 d) and rimsulfuron (7.5) were, respectively, 4.0 3.7, and 1.9 times lower than those in sterile soil, thus confirming the decisive contribution of biological processes in soil degradation of the three sulfonylureas. At the concentrations of 0.2 and 5 mg a.i. kg−1 of soil, no detrimental effects of the three sulfonylureas on soil respiration and dehydrogenase activity were detected. Indeed, soil amended with the three sulfonylureas at 5 mg a.i. kg−1 of soil showed a transient increase of both respiration and dehydrogenase activity. Results showed that triasulfuron, primisulfuron methyl, and rimsulfuron have probably no effects on soil microbial activities at the concentrations used in agricultural practice, which are approximately 1/10 of the lowest concentration tested in the present study.
Water Quality in Walnut Creek Watershed: Setting and Farming Practices
Authors: Hatfield J. L. , Jaynes D. B. , Burkart M. R. , Cambardella C. A. , Moorman T. B. , Prueger J. H. , Smith M. A.
Published: July 2010

Nonpoint‐source pollution has been linked to agricultural practices; however, there is a need for quantitative information describing the effect of specific farming practices on ground and surface water quality. Lack of information at the watershed scale limits our ability to make decisions about the effect of potential changes in either farming practices or landscape management that would enhance water quality. A multidisciplinary study was designed to evaluate the effect of farming practices on subsurface drainage, surface runoff, stream discharge, groundwater, volatilization, and soil processes that influence water quality. Walnut Creek watershed is a 5130‐ha intensively cropped area in central Iowa on the Des Moines Lobe landform region. Soils within the watershed are in the Clarion‐Nicollet‐Webster (Typic Hapludoll‐Aquic Hapludoll‐Typic Haplaquoll) soil association, and the underlying surficial material is glacial till. Land use is predominantly corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.] rotation. Fertilizer use, herbicide application, tillage practices, and crop selection were obtained through surveys of each field operator. Atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl]amino]‐2‐methylpropanenitrile], EPTC [S‐ethyl dipropyl carbamothioatel, and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methyiphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] are the primary herbicides used within the watershed at rates similar to those for the state. Nitrogen fertilizer was applied as anhydrous ammonia on 60% of the corn fields at an average rate of 153 kg ha−1 for the 1991–1994 period, but the frequency of corn fields receiving <112 kg ha−1 has increased.
Water Quality in Walnut Creek Watershed: Herbicides in Soils, Subsurface Drainage, and Groundwater
Authors: Moorman T. B. , Jaynes D. B. , Cambardella C. A. , Hatfield J. L. , Pfeiffer R. L. , Morrow A. J.
Published: July 2010

Herbicide transport in subsurface drainage can result in unacceptable levels of contamination in surface waters. This study assessed the extent of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3‐,5‐triazine‐2,4‐diamine] and metribuzin [4‐amino‐6‐(1,1‐dimethyethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one] transport to subsurface drainage and shallow groundwater. A corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation was used with corn receiving banded atrazine applications of 459 g ha−1 in 1992 and 561 g ha−1 in 1994. Soybean were treated with metribuzin at 420 g ha−1 in 1993 and 1995. Monthly flow‐weighted average concentrations of atrazine in drainage water did not exceed 3 µg L−1 and annual losses ranged from 0.02 to 2.16 g ha−1 during the 4‐yr study. Less than 3% of the groundwater samples contained atrazine concentrations exceeding the 3 µg L−1 maximum contaminant level for drinking water (MCL). Atrazine was detected more frequently in groundwater beneath the lowest parts of the field, despite greater than average sorption to soils in that area. Metribuzin was also found in groundwater, but only half as frequently as atrazine. The patterns observed in subsurface drainage and groundwater reflected the persistence of atrazine and metribuzin in soil. Atrazine was detected in >90% of surface soil samples up to 23 mo after application, whereas metribuzin was rarely detected during the second year following application. Atrazine was found far more commonly than metribuzin in soil below 30 cm depth.
Tributary Stream Infiltration as a Source of Herbicides in an Alluvial Aquifer
Authors: Burkart Michael R. , Simpkins William W. , Squillace Paul J. , Helmke Martin
Published: July 2010

Where Walnut Creek flows across the South Skunk River alluvial aquifer, it provides a potential source of herbicides and herbicide metabolites. This straightened reach of the creek loses water and dissolved contaminants to the alluvial aquifer through a layer of fine‐grained flood plain deposits. Estimates of potential flux of chemicals were based on measurements taken during baseflow in April 1994 before herbicides were applied to the watershed and in June 1994 after chemical application and when stream discharge included runoff and tile‐drainage water. Hydraulic head measurements between the creek and flood plain deposits and between the creek and aquifer confirmed the potential for downward groundwater flow during both sampling periods. Hydraulic conductivity estimates from slug tests were used to calculate an average linear groundwater velocity of 0.5 m d−1 in the fine‐grained flood plain deposits. At this velocity, contaminants could be advectively transported to the aquifer within 6 d. The potential for atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) flux to the aquifer from the creek was estimated to be between 60 and 3000 µg d−1 m−2. This rate is one to three orders of magnitude greater than the estimated flux via leaching beneath a typical field. If the process of vertical stream leakage occurs in many hydrologic settings, it may constitute a substantial source of herbicides to shallow alluvial aquifers in many areas of the Midwest.
Field‐Scale Metolachlor Volatilization Flux Estimates from Broadcast and Banded Application Methods in Central Iowa
Authors: Prueger J. H. , Hatfield J. L. , Sauer T. J.
Published: July 2010

Volatilization of pesticides has been considered to be a large part of the loss from fields after application; however, there have been relatively few studies conducted to quantify the amount lost to the atmosphere. This study was designed to evaluate volatilization rates of a preemergent herbicide Dual [a.i. metolachlor 2.24 kg ha−1 (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)‐acetamide)] from two fields (175 and 45 ha) in central Iowa under contrasting tillage operations and pesticide application scenarios. Metolachlor vapor was trapped using polyurethane foam plugs at six heights on a profile mast. Average concentrations were measured at each height every 2 h for the first 4 d after application, then every 4 h thereafter. Volatilization rates were calculated with a flux‐gradient technique using data from Bowen ratio and eddy correlation measurements. Flux profile concentrations of metolachlor were large during the first 24 h and quickly declined for the duration of the study. There was approximately a threefold greater cumulative volatilization loss of applied metolachlor from the broadcast (22%) treatment than from the banded treatment (6%) for the 10‐d study period. Metolachlor volatilization was affected by residue cover, spatial concentration on the surface, and timing of precipitation.
Development and Verification of a Model Simulating Ammonia Volatilization from Soil and Manure
Authors: Hengnirun S. , Barrington S. , Prasher S. O. , Lyew D.
Published: July 2010

The VOLAT model was developed to simulate ammonia volatilization in manure and soil and to be integrated as a submodel into a larger model called Manurial Nitrogen Management: Environmental Aspects (MANIMEA). The MANIMEA model simulated the transformation and transportation processes affecting N in manure‐amended soils. A major feature of MANIMEA is that the manure and soil can be considered as separate components. This is important because manure is usually left on the soil surface for a period following application and prior to its incorporation into the soil; a significant amount of ammonia is lost by volatilization during this period. The VOLAT model was based on a nonpoint source and used a first‐order governing equation. An overall rate constant was used to take into account the effects of temperature, soil cation exchange capacity (CEC), and the air flow rate on volatilization. The VOLAT model was verified by comparing it to an analytical solution and by using experimental conditions and data given in the literature. Comparison of results demonstrated similar trends with some differences that can be attributed to the ability of VOLAT to account for variations in temperature, CEC, and air flow rates.Simulations were done for two manure application methods: surface application and injection. Results demonstrated that VOLAT rendered a simulation of N loss through volatilization that fell within acceptable limits.
Modeling Evaluation of Alternative Management Practices and Reclaimed Water for Turfgrass Systems
Authors: King K. W. , Balogh J. C.
Published: July 2010

The use of reclaimed water for turfgrass irrigation is being implemented to conserve potable water supplies. Reclaimed water coupled with alternative management strategies may reduce offsite loadings of fertilizers and pesticides. The Environmental Policy Integrated Climate (EPIC) water quality model was used to evaluate alternative management practices and reclaimed water for a southern turfgrass system. One green and fairway were modeled for a 65‐yr period of climatic record with four treatments. Specifically, the treatments were normal water normal management (NWNM), normal water reduced management (NWRM), reclaimed water normal management (RWNM), and reclaimed water reduced management (RWRM). Surface and subsurface nitrate (NO3‐N), fenamiphos (ethyl 3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl)phosphoramidate), and MSMA (monosodium methanearsonate) losses were evaluated. Significant differences were predicted in NO3‐N runoff and leachate losses from green management. Mean annual NO3‐N losses from runoff were 2.85 kg ha−1 (NWNM) and 2.05 kg ha−1 (RWRM). Significant reductions in mean annual surface and subsurface NO3‐N losses from fairway conditions were simulated when comparing NWNM (5.11 kg ha−1 surface; 1.68 kg ha−1 subsurface) to RWRM (2.69 kg ha−1 surface; 0.90 kg ha−1 subsurface). The cited differences in NO3‐N losses in runoff and leachate from green and fairway conditions were attributed primarily to irrigation strategies and excess rainfall. Predicted average annual pesticide recovery in runoff and leachate was <0.01% of applied and no significant differences were predicted with respect to treatments. This modeling strategy provides valuable insight into the relative efficacy of implementing reduced management practices for turfgrass systems.