bluuebunny/crossref_metadata_2025 huggingface dataset:
A Quantitative Estimation of the Complexation of Small Organic Molecules with Soluble Humic Acids
Authors: Clapp C. E. , Mingelgrin U. , Liu R. , Zhang H. , Hayes M. H. B.
Published: July 2010

Small organic molecules, such as the commonly used herbicides napropamide [N,N‐diethyl‐2‐(1‐naphthyloxy) propionamide] and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), complex with soluble humic acids (HAs), producing a marked effect on apparent solubility, availability, and mobility. The overall objective of the present paper is to propose a procedure by which the extent of complexation of small organic molecules with stable humic acids can be quantitatively estimated. Experiments were carried out to investigate the effects of HA and herbicide concentrations, pH, and ionic composition and strength on the extent and nature of complexation using an equilibrium dialysis procedure and 14C‐labeled herbicides. The relative strength of complexes of napropamide with a series of HAs from a wide range of sources, determined at a concentration of 2.0 mg HA mL−1, was in the order of soil > peat > water. Complexation of the herbicides with the soil HA was greater for napropamide than for atrazine (Kc at pH 6.5, 0.83 and 0.12 mL mg−1, respectively). As solubility of molecules in water increases, complex formation usually decreases. However, the complexation of napropamide and atrazine did not correlate inversely with their solubility. Environmental conditions, such as pH and ionic strength and composition, as well as the source of the HAs, had a strong effect on the complexation of the investigated pesticides. The relationship between complexation and the above factors suggests that it is their effect on coiling of the HA strands, which determines the extent of complexation.
Removal of Atrazine from Aqueous Solution by Natural and Activated Bentonite
Authors: González‐Pradas E. , Villafranca‐Sánchez M. , Gallego‐Campo A. , Ureña‐Amate D. , Fernández‐Pérez M.
Published: July 2010

To evaluate the potential use of bentonite in removing atrazine [2‐chloro‐4‐ethylamino‐6‐isopropilamino‐1,3,5‐triazine] from water, the adsorption of atrazine on bentonite desiccated at 383 K untreated, and acid‐treated with H2SO4 solutions over a concentration range between 0.25 × 103 cmol L−1 and 1.00 × 103 cmol L−1, from aqueous solution at 303 K has been studied by using batch experiments. In addition, column experiments were carried out with the bentonite samples treated with the 1.00 × 103 cmol L−1 H2SO4 [B‐A (1.00)] using two aqueous atrazine solutions at C = 5.91 mg L−1 and C = 9.78 mg L−1 concentrations. The experimental data points have been fitted to the Langmuir equation to calculate the adsorption capacities (Xm). Values for Xm ranged from 0.07 g kg−1 for the untreated bentonite up to 13.4 g kg−1 for the [B‐A (1.00)] samples. The removal efficiency (R) ranged from 2.71% for the B‐N up to 83.5% for B‐A (1.00). The batch experiments show that the acid‐treated bentonite is more effective than the natural bentonite in relation to the adsorption of atrazine. The column experiments show that the B‐A (1.00) sample might be reasonably used in removing atrazine, the column efficiency increasing from 47.5% for the C = 9.78 mg L−1 aqueous solution of atrazine up to 63.4% for the C = 5.91 mg L−1 one.
Herbicide Contamination of Prairie Springs at Ultratrace Levels of Detection
Authors: Wood John A. , Anthony Donald H. J.
Published: July 2010

Natural springs provide an opportunistic subject for assessing aquifer contamination. To determine the frequency and level of aquifer contamination by herbicides in the Canadian prairie, a study of natural springs draining small surficial aquifers a few hectares in area was carried out in southern Saskatchewan. All but one of the aquifers investigated received herbicide applications either for agricultural purposes or brush control. Elevated tritium isotope activities (10–60 TU) confirmed recent recharge of these aquifers. No wells were present on these aquifers. Therefore, the possibility of contamination by direct entry down wells was eliminated from the study. Large volume extraction technology permitted detections of herbicides at ng L−1 levels. This is the first study of herbicides in natural springs in Canada. Herbicides were detected in 23% of samples collected. The most frequently detected analytes being atrazine (6‐chloro‐N2‐ethyl‐N4‐(isopropyl)‐1,3,5‐triazine‐2,4‐diamine), picloram (4‐amino‐3,5,6‐trichloropicolinic acid) and 2,4‐D ((2,4‐dichlorophenoxy)acetic acid), with detections in 12, 7, and 7% of samples collected, respectively. The results show that shallow aquifer contamination occurs in the absence of wells. However, the levels detected were in the ng L−1 (ppt) range, which is much less than levels commonly reported in most well surveys. None of the herbicide concentrations exceeded any guidelines for drinking water, livestock, irrigation, and aquatic life including Canadian, Provincial, World Health Organization, and USEPA guidelines.
Runoff of Two Sulfonylurea Herbicides in Relation to Tillage System and Rainfall Intensity
Authors: Afyuni M. M. , Wagger M. G. , Leidy R. B.
Published: July 2010

The use of sulfonylurea herbicides is increasing because they are used at very low rates and offer greater weed management flexibility in pre‐ and postemergence programs. Information is needed on the off‐site movement of these compounds under different tillage systems. Our objective was to evaluate the runoff potential of chlorimuron ethyl {(2‐[[[[(4‐chloro‐6‐methoxy‐pyrimidin‐2‐yl) amino]carbonyl]‐amino]sulfonyl] benzoic acid)}, nicosulfuron {(2[[(4,6‐dimethoxypyrimidin‐2‐yl) aminocarbonyl]aminosulfonyl]‐N, N‐dimethyl‐3‐pyridinecarboxamide)}, and bromide in conventional (CT) and no‐tillage (NT) production systems under simulated rainfall. The soil types were a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Paleudult) at a Coastal Plain location and a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) at a Piedmont location. The first simulated rainfall event (30 min) consisted of a low (1.27 cm h−1) or high (5.08 cm h−1) rate applied 24 h after herbicide and bromide application. One week later, the high rainfall rate was repeated on all plots. Consistently greater runoff occurred with CT compared to NT. Runoff differences between tillage systems were more pronounced for the second rainfall simulation and also with the Piedmont soil. The average herbicide losses from the initial high rainfall simulation were 1.2 and 2.2% of the total application (0.014 kg ha−1) for CT and NT, respectively, at the Coastal Plain location. Similar results were obtained at the Piedmont location. Mean herbicide losses during the second rainfall simulation represented <0.2% of the applied rate. There were no detectable concentrations of either herbicide found in the sediment phase of runoff. On the basis of these results, it is not expected that chlorimuron or nicosulfuron pose a significant threat to the environment via transport in runoff.
Sorption and Degradation of Alachlor in Soil and Aquifer Material
Authors: Clay S. A. , Moorman T. B. , Clay D. E. , Scholes K. A.
Published: July 2010

Herbicides may contaminate groundwater when used over shallow aquifers. Alachlor [2‐chloro‐N‐methoxymethyl‐N‐(2,6‐diethylphenyl)‐acetamide] is widely used in corn (Zea mays L.) and soybean (Glycine max L.) for grass control in eastern South Dakota where depth to groundwater ranges from <2 to >20 m. Sorption and degradation of alachlor, two processes that control its fate in the environment, were measured in laboratory batch equilibrium and incubation studies. Surface soil and sediment samples from above and below the water table (∼6 m below the soil surface) were collected following aseptic procedures. Alachlor sorption to the surface A horizon soil (silty clay loam) was about 13 times greater than sorption to the 2C horizon soil (sand and gravel). About 2.5% of the alachlor was completely mineralized after 112 d in surface soil, whereas <0.5% was mineralized in the 2C horizon soils. The addition of C (lyophilized algae biomass) increased ring mineralization and polar metabolite formation in all samples. These data indicate that bacterial populations in the Big Sioux aquifer are sufficiently diverse to degrade complex organic molecules. Carbon was the factor most limiting alachlor metabolism in subsurface sediments.
Phosphate Availability and Inorganic Transformation in an Alum Sludge‐Affected Soil
Authors: Cox A. E. , Camberato J. J. , Smith B. R.
Published: July 2010

Land application of alum sludge is a disposal alternative. A greenhouse experiment was conducted to determine (i) alum sludge effects on phosphorus (P) availability and inorganic P forms, and (ii) the relationship between inorganic P fractions and P availability. Alum sludge slurry (0, 4.45, 8.9, and 17.8 g solid kg−1 soil) was surface applied to wheat (Triticum aestivum L.) grown in a Yauhannah soil (fine‐loamy, siliceous, thermic Aquic Hapludults) at four P rates (0, 6.5, 11, and 22 mg kg−1 soil). After the first wheat crop, the sludge was mixed throughout the soil and a second crop grown. Surface‐applied sludge decreased wheat dry matter (DM) and P uptake. When incorporated, 4.45 g kg−1 alum decreased DM and P uptake. Phosphate application increased DM and P uptake of the first wheat crop, but had no effect on the second crop. Surface‐applied sludge increased Al‐P, Fe‐P, and Ca‐P in the 0‐ to 7.5‐cm soil depth, but not in the 7.5‐ to 15‐cm soil depth. Loosely boond‐P and Al‐P increased with P rate. Phosphorus uptake and DM of the first wheat crop were positively related to loosely bound‐P and Mehlich 1‐P. Dry matter of the second wheat crop was positively related to loosely bound‐P and Mehlich 1‐P and P uptake was positively related to loosely bound‐P. Aluminum‐P was negatively related to P availability indices. In alum sludge‐affected soils applied P is immobilized mainly as Al‐P, and Mehlich 1‐P and loosely boond‐P are reliable estimators of P availability.
Solid‐Phase Extraction of Aldicarb and its Metabolites from Water and Soil
Authors: Johnson K. A. , Harper F. D. , Weisskopf C. P.
Published: July 2010

Extraction methods using solid‐phase extraction (SPE) cartridges are generally preferred over traditional liquid‐liquid extraction methods when they are available. Solid‐phase extraction methods require less preparative work, thus increasing sample through‐put. A SPE method using a graphite carbon sorbent was developed to extract low concentrations (1–40 µg/L) of the polar pesticide, aldicarb [2‐methyl‐2‐(methylthio)propionaldehyde O‐(methylcarbamoyl) oxime], and its oxidative metabolites, aldicarb sulfoxide [2‐methyl‐2‐(methylsulfinayl)propionaldehyde‐O‐(methylcarbamoyl) oxime] and aldicarb sulfone [2‐methyl‐2‐(methylsulfonyl) propionaldehyde‐O‐(methylcarbamoyl) oxime] from water samples. The analytes were removed from a 150‐mL water sample by the SPE cartridge and eluted with 2 mL of methanol. Recoveries from water for all three compounds exceeded 90% with coefficients of variation ranging from 3 to 9%. An extraction method was also developed to extract aldicarb and its metabolites from soil using water as the extractant. The analytes are then recovered from the water using the same SPE method referred to above. Recoveries from soil for all three compounds ranged from 80 to 95%. Our SPE method also worked well (recoveries >95%) for two other carbamates, methomyl [S‐methyl N‐[(methylcarbamoyl)oxy]thioacetimidate] and oxamyl [N′, N′‐dimethyl‐N‐[(methylcarbamoyl)oxy]‐1‐thiooxamimidate] tested and should work with other polar compounds once they are in the aqueous phase.
Time Dependency of Triticonazole Fungicide Sorption and Consequences for Diffusion in Soil
Authors: Beigel C. , Barriuso E. , Di Pietro L.
Published: July 2010

Diffusion is a key process regarding the redistribution in soils of systemic pesticides applied in seed treatments. We investigated the influence of nonequilibrium sorption on the diffusivity of triticonazole fungicide [(1RS)‐(E)‐5‐(4‐chlorophenyl‐methylen)‐2,2‐dimethyl‐1‐(1H‐1,2,4‐triazol‐1‐ylmethyl)‐cyclopentan‐1‐ol] in loam clay soil from Grignon, France (Typic Eutrochrept). Triticonazole diffusion coefficients were measured in saturated soil columns for time periods ranging from 1 to 25 d. Nonequilibrium sorption was evaluated from measurement of apparent desorption coefficients, and from estimation of apparent partition coefficients from a diffusivity model. Triticonazole availability was also evaluated based on successive aqueous and methanol extractions, and measurement of the nonextractable residues fraction. Triticonazole diffusion in soil was characterized by a strong time‐dependence. Apparent diffusion coefficient decreased from 0.05 cm2 d−1 at 2 d to 0.02 cm2 d−1 at 25 d. Triticonazole apparent sorption coefficient increased with time of diffusion, from 5 L kg−1 at 1 d to 10.5 L kg−1 at 25 d, which was greater than the batch equilibrium value of 4.35 L kg−1. The measured and calculated results were very close, showing that nonequilibrium sorption was the key process responsible for the decrease in triticonazole apparent diffusion rate. The availability of the diffusing residues diminished constantly with time. The water‐extractable fraction corresponding to the more available residues decreased from 31% at 1 d to 17% at 25 d, while a resistant fraction was rapidly formed representing 9% after 25 d. Triticonazole slow desorption behavior was attributed to rate‐limiting intrasorbent diffusion.
Rain Pattern and Soil Moisture Content Effects on Atrazine and Metolachlor Losses in Runoff
Authors: Zhang X. C. , Norton L. D. , Hickman M.
Published: July 2010

Herbicide concentration in runoff varies dramatically within a storm, therefore storm pattern is postulated to have a significant impact on herbicide loss. We evaluated the effects of storm pattern and soil moisture content on herbicide loss in runoff, and used our data to validate the uniform mixing concept for modeling herbicide transfer to runoff. Atrazine and metolachlor were surface applied to air‐dried soil at rates of 1.12 and 2.24 kg/ha, respectively. Two soils (Cecil sandy loam and Miami silty loam), four storm patterns (uniform, advanced peak, intermediate peak, and delayed peak), and two moisture levels (wet and dry) were used. Dissolved herbicide losses from the advanced peak were twice those from the other patterns for both herbicides for Cecil soil. The significance of rain pattern effects was reduced for Miami soil, but metolachlor loss from the advanced peak was 1.9 times that from the delayed peak. Rain pattern affected sediment‐bound herbicide loss, but no consistent trend was shown for both soils. Under wet conditions a greater potential for dissolved and sediment‐bound herbicide losses was shown for both herbicides on Miami soil than on Cecil soil. Measured herbicide concentrations in runoff decreased exponentially with cumulative rainfall depth, and were adequately described by the uniform mixing model. Results show that information on intensity distribution and transient infiltration rate is needed to better predict both instantaneous and total herbicide losses during a storm.
Influence of Buffers on Pesticide and Nutrient Runoff from Bermudagrass Turf
Authors: Cole J. T. , Baird J. H. , Basta N. T. , Huhnke R. L. , Storm D. E. , Johnson G. V. , Payton M. E. , Smolen M. D. , Martin D. L. , Cole J. C.
Published: July 2010

Buffer length (0, 2.4, and 4.9 m), mowing height (1.3 and 3.8 cm), and solid‐tine aerification were evaluated to reduce pesticide and nutrient runoff from bermudagrass [Cynodon dactylon (L.) Pers.] turf on a Kirkland silt loam (fine, mixed, thermic Udertic Paleustolls) with a 6% slope. Nitrogen, P, chlorpyrifos [o,o‐diethyl o‐(3,5,6‐trichloro‐2‐pyridinyl) phosphorothioate], and the dimethylamine salts of 2,4‐D (2,4‐dichlorophenoxyacetic acid), mecoprop [2‐(2‐methyl‐4‐chlorophenoxy) propionic acid], and dicamba (3,6‐dichloro‐o‐anisic acid) were applied at standard use rates on plots located upslope of buffers. A portable rainfall simulator applied precipitation rates of 51 or 64 mm h−1 for 75 to 140 min within 24 h after chemical application. Soil moisture before simulated rainfall in July 1995 was low and pesticide and nutrient loss to surface runoff was <3% and 2% of applied, respectively. Highest concentrations of pesticides and nutrients in runoff water were 314 µg L−1 for 2,4‐D and 9.57 mg L−1 for PO4‐P from the treatment containing no buffer. In August, 165 mm of natural rainfall fell 7 d before simulated rainfall and pesticide and nutrient loss to surface runoff was increased to 15 and 10% of applied, respectively. Highest concentrations of pesticides and nutrients in runoff water were 174 µg L−1 for 2,4‐D and 8.14 mg L−1 for PO4‐P from the treatment containing no buffer. Overall, buffers were effective in reducing pesticide and nutrient runoff due in part to dilution. In most instances, buffer mowing height, length (2.4 vs. 4.9 m), and aerification did not significantly affect pesticide and nutrient runoff.
Predicting Nitrate Concentrations in Northern Ireland Rivers Using Time Series Analysis
Authors: Stronge K. M. , Lennox S. D. , Smith R. V.
Published: July 2010

Lough Neagh is an important natural resource, being the largest single source of potable water for Belfast. Its catchment area covers about one‐third of the land area of Northern Ireland. Six inflow rivers drain 88% of the total catchment, which has a land usage of grassland and rough grazing that is similar to Northern Ireland as a whole. This report examines the causes of the year‐to‐year variation in river NO−3 concentrations that have been the focus of European Community (EC) legislation. A multiple regression model has been developed which explains 74% of the variation in NO−3 concentrations for the time period 1974 to 1994. Based on a knowledge of the Northern Ireland annual utilized metabolizable energy (UME) for grazing livestock and N fertilizer sales, the model employs the efficiency of fertilizer usage as an independent variable. Additional independent variables are climatic: previous summer rainfall, sun hours in the winter and rainfall for the period January to June. Based on a worst case scenario, employing the extreme values for these climatic variables and the least fertilizer efficiency ratio, the predicted NO−3 concentration is only 4.4 mg N L−1, which is well below the EC maximum admissible level of 11.3 mg N L−1 for drinking water.
Seasonal and Long‐Term Changes in Nitrate‐Nitrogen Content of Well Water in Oklahoma
Authors: Phillips S. B. , Raun W. R. , Johnson G. V.
Published: July 2010

To ensure that NO3‐N concentrations in groundwater do not exceed the maximum contaminant level (MCL; 10 mg L−1), drinking water supplies are continuously sampled and analyzed. Water sampling and analytical methods have changed during the past 40 yr, and failure to apply the errors associated with those methods places researchers at risk of reporting invalid NO3‐N changes. The objectives of this research were to compare analytical procedures, seasonal samplings, and storage methods for well water NO−3N analyses using historical and recent well water data, to identify where changes in NO3‐N concentration have taken place and possible reasons for the changes; and to determine if age of water, well depth, and NO3‐N concentration are related. Benchmark NO3‐N analyses were obtained for 46 water wells which were then sampled each season (fail, winter, spring, and summer) over a 2‐yr period. For each sampling, four samples were taken from each well; two were frozen immediately (common today) and two were stored at ambient temperature (benchmark procedure). Nitrate‐N was determined on subsamples from all four samples using phenoldisulfonic acid (benchmark procedure) and automated Cd reduction (common today). This work suggests that a minimum difference of 6.15 mg NO3‐N L−1 is required before declaring significant differences between historical and current well water NO3‐N levels.
Acid‐Base Properties of a Limed Pyritic Overburden during Simulated Weathering
Authors: Doolittle James J. , Hossner L. R.
Published: July 2010

Surface‐mine reclamation is often hindered by the formation of acid minesoil and acid mine drainage from FeS2 oxidation. Surface soils containing FeS2 are often treated with crushed limestone (predominately CaCO3) to prevent acid minesoil formation. The main objective of this study was to evaluate the long‐term effectiveness of liming pyritic minesoil to prevent the formation of acid minesoil and acid mine drainage. Pyritic minesoils that did not receive lime became acidic very rapidly and produced acidic leachate. Almost all of the FeS2 in this treatment oxidized during the first 200 d. The addition of lime at a rate of 25% of the theoretical acid‐base account (ABA) significantly slowed FeS2 oxidation, but rapid oxidation ensued after the added lime was neutralized. Treatments receiving a liming rate of 50% ABA or greater remained neutral to alkaline throughout the study. Acid‐base values and residual FeS2‐CO3 data, however, indicate that the lime was dissolving from the system faster than the FeS2 was oxidizing, and all the treatments would eventually become acidic. The results indicate that the liming of a pyritic overburden to an ABA of 125% is not a sustainable solution to preventing acid minesoil and acid mine drainage.
Characterization of Volatile Organic Emissions and Wastes from a Swine Production Facility
Authors: Zahn J. A. , Hatfield J. L. , Do Y. S. , DiSpirito A. A. , Laird D. A. , Pfeiffer R. L.
Published: July 2010

Analytical methods for monitoring the volatile organic compound (VOC) emissions, for defining atmospheric transport coefficients, and for monitoring solution phase chemistry have been developed to define processes regulating emission of malodorous and other VOCs from a high odor swine production facility. Of the 40 organic compounds identified in liquid and outdoor air samples from the swine production facility, 27 VOCs were confirmed to contribute to decreased air quality in the vicinity of the facility. Specifically, C2 through C9 organic acids demonstrated the greatest potential for decreased air quality, since these compounds exhibited the highest transport coefficients and highest airborne concentrations. Flux measurements suggested that the total rate of nonmethane VOC emissions from the deep basin swine waste storage system was 500‐ to 5700‐fold greater than established nonmethane VOC fluxes from nonanthropogenic sources. The volatilization rate of malodorous and other VOCs from the stored swine waste was positively correlated with wind velocity between 0.2 and 9.4 m s−1, and a maximum concentration of VOCs present in the air was observed to occur at a wind velocity of 3.6 m s−1. Experimental Henry's law coefficients adequately predicted the transport efficiency observed for some of the VOC emissions measured from air samples taken at 0, 25, and 100 m from the swine waste storage basin; however, results indicated that laboratory‐based extraction procedures, currently used to estimate malodor potential for swine slurry samples, provide an inaccurate representation of malodorous and other airborne VOCs actually present in the air near swine production facilities.
Sewage Biosolids Cumulative Effects on Extractable‐Soil and Grain Elemental Concentrations
Authors: Barbarick K. A. , Ippolito J. A. , Westfall D. G.
Published: July 2010

While land application of sewage biosolids is the most expedient method of recycling plant nutrients, concern over trace element additions resulted in U.S. Environmental Protection Agency (USEPA) beneficial‐use regulations. We studied 11‐yr biosolids addition effects on ammonium bicarbonate diethylenetriaminepentaacetic acid (AB‐DTPA) and 4 M HNO3 extractable levels of soil Cd, Cu, Mo, Ni, P, Pb, and Zn, and the relationship between the soil‐extractable concentrations and grain concentrations. The soils at our four dryland wheat (Triticum aestivum L.) sites were Aridic Paleustolls (Weld and Platner loam). For each application, we used four rates of biosolids (0, 7, 14, and 28 Mg ha−1) from the Littleton/Englewood, CO Wastewater Treatment Plant. We tested linear, quadratic, and either exponential‐rise (plateau) or exponential‐decay models for AB‐DTPA‐ and 4 M HNO3‐extractable concentrations compared with the cumulative quantity of biosolids‐borne element added and with elemental grain concentrations. Models for AB‐DTPA‐extractable Cu, P, Pb, and Zn and 4 M HNO3‐extractable Cu and P vs. the cumulative quantity added produced R2 values ≥ 0.46. For grain concentrations, only the models for AB‐DTPA vs. grain Zn produced an R2 ≥ 0.50. For monitoring soil levels of Cd, Cu, Mo, Ni, P, Pb, and Zn in Paleustolls (common soils in the western Great Plains dryland wheat areas) that continuously receive biosolids, we recommend AB‐DTPA over 4 M HNO3 soil extractions. The AB‐DTPA extractions also provide soil fertility information (NO3‐N and plant available P, K, and micronutrients).
Changes in the Distribution of Selenium Oxidation States with Sample Storage
Authors: Martens D. A. , Suarez D. L.
Published: July 2010

Significant changes in the distribution of selenium (Se) oxidation states of fresh soil were noted with oven‐drying (90°C) or with outdoor storage (>5 yr) in compromised plastic containers compared with small changes in Se oxidation state distribution in air‐dried samples. Compromised outdoor storage resulted in a 25% increase in the selenate (Se6+) concentrations with a concomitant 18.4 and 5.7% decrease in elemental Se and selenite (Se4+) concentrations, respectively, on a total Se basis. Substantial increases in phosphate‐soluble selenide from 15.7% of total Se for fresh seleniferous alfalfa (Medicago sativa L.) to 32.6% phosphate‐soluble Se were noted with air‐dried alfalfa. The results indicate that air‐drying will not substantially alter the distribution of soil Se oxidation states, but will result in a significant increase in the concentration of phosphate‐soluble Se in seleniferous alfalfa residue.
Leaching and Preferential Flow of Clopyralid under Irrigation: Field Observations and Simulation Modeling
Authors: Elliott J. A. , Cessna A. J. , Best K. B. , Nicholaichuk W. , Tollefson L. C.
Published: July 2010

Pesticide leaching is a potential problem on irrigated land in Saskatchewan. This study examined a worst case scenario for leaching of the herbicide, clopyralid. Herbicide concentrations were measured in water samples from suction lysimeters and tile drain effluent during and after a leaching irrigation to remove salts. Clopyralid was found throughout the soil profile within 20 d of application and was detected in the first water flowing in the tile drains. Approximately 1.5% of the applied clopyralid was lost in the tile drain effluent. The presence of higher concentrations of clopyralid in tile drain water samples at 2 m than in lysimeter water samples taken from 1.5 and 1.8 m was attributed to preferential transport. Another indication of preferential flow was the disparity between measured soil hydraulic characteristics and the timing of the arrival of water in the tile drains. Good agreement between observed and simulated clopyralid distributions was obtained using a bimodal flow scenario with the LEACHM model. It assumed that 40% of the applied water moved through preferential flowpaths with saturated hydraulic conductivities two orders of magnitude greater than the bulk soil. Chemical moving with this water did not penetrate the soil matrix and was not accessed by suction lysimeters. The remaining 60% of applied water moved through the soil matrix according to measured hydraulic characteristics. The modeling approach described herbicide concentrations in the soil matrix and preferential flow from a large field integrated by tile drainage but would not be applicable in soil column studies or small plots.
Phosphate and Tritium Transport through Undisturbed Subsoil as Affected by Ionic Strength
Authors: Jensen Marina Bergen , Hansen Hans Christian Bruun , Hansen Søren , Jørgensen Peter Rene , Magid Jakob , Nielsen Niels Erik
Published: July 2010

Storm flow can cause serious subsurface losses of dissolved orthophosphate from soils that under low flow conditions effectively retain orthophosphate (Pi). To test if storm flow loss of Pi can be related to preferential flow and/or decrease in ionic strength of mobile solution we applied combined pulses of H232PO−4 (32p) and tritium (3H2O) to an undisturbed column of clayey subsoil (diam. 0.5 m, height 0.73 m) subjected to water saturated steady flow with either distilled water (0.003 mS cm−1) or a dilute salt solution (0.2 mS cm−1). The pulse applications resulted in narrow breakthroughs of 32P with peak arrivals after displacement of only 2 to 4% of the total water content. In comparison, the 3H2O‐breakthrough curves had peak arrivals after displacement of 8 to 18% of the total water content and showed extensive tailing. In distilled water approximately twice as much phosphate was transported through the column than in the diluted salt solution, although the recovery percentage in both cases was <1% of the applied 32P‐mass. Slicing of the column after dye application confirmed the presence of heterogeneous flow paths. The results suggest that the positive correlation observed between concentration of dissolved Pi and field effluent discharge rate is restricted to rainfall intensities that initiate preferential flow, and that the Pi‐transport is increased the more dilute the percolating solution remains.
Kinetic Isotope Effects in Production of Nitrite‐Nitrogen and Dinitrogen Gas during In Situ Denitrification
Authors: Bates H. K. , Martin G. E. , Spalding R. F.
Published: July 2010

In multistep redox reactions, stable isotopes of the product species can provide insight into the complexities of the reaction. A method was developed that chromatographically separated nitrite (NO−2) from nitrate (NO−3) in quantities that permitted isotopic analysis both N species. Only a 3% peak‐to‐peak crossover contamination was measured in the column eluates during chromatographic separation using 15N‐enriched NO−2. During in situ microcosm‐amended denitrification, low δ15N values of NO−2 ranging from −2 to 4‰ verified that NO−2 produced early persisted throughout much of the reaction. Significant isotopic depletion of the residual NO−3 plus NO−2 fraction resulted. This depletion effect was reflected in lower apparent isotopic‐enrichment factors (flatter slopes) in plots of δ15N vs. In [NO−3 + NO−2] than those vs. In [NO−3] alone. Dinitrogen concentrations produced during the reaction were determined by measuring δAr/N2 values and showed that significant N2 losses occurred in the latter part of the reaction due to supersaturated conditions. The δ15N values for the N2 produced during denitrification ranged from −5.2‰ to higher values of +17‰ when the reaction was ∼70% complete. A slope reversal in δ15N of produced N2 followed when NO−2 reduction became more dominant, as isotope dilution of product N2 occurred. At the culmination of the reaction, the δ15N value of N2 approached but did not return to the original δ15N value of the NO−3. The results caution the blind use of Ar/N2 ratios in groundwaters that initially contain high NO−3 levels and emphasize the importance of NO−2 in environmental sampling.
Denitrification in Cultivated and Noncultivated Riparian Areas of Grass Cropping Systems
Authors: Horwath William R. , Elliott Lloyd F. , Steiner Jeffrey J. , Davis Jennifer H. , Griffith S. M.
Published: July 2010

The factors that affect denitrification of fertilizer N were determined in cultivated riparian (CR) soils cropped to perennial ryegrass (Lolium perenne L.) and noncultivated naturally vegetated riparian soils (NCR) of poorly drained grass cropping systems in western Oregon. Denitrification activity in the NCR was low compared with the CR using the Acetylene Inhibition method. The CR soil denitrification activity was consistent over the growing season, averaging between 269 and 280 g N2O‐N ha−1 d−1 during the measurement period depending on soil type. Denitrification activity was positively correlated to soil NH4‐N level in the CR. The greater denitrification activity of the CR likely reflects fertilizer applications in contrast to no fertilizer addition to the NCR. Nitrate‐N levels in the CR averaged 5 to 12 times higher than those of the NCR. Nitrate did not appear to encroach from the CR into the NCR by subsurface water movement. The microbial biomass was four times larger in the NCR soils and may have functioned as a significant sink for N reducing denitrification activity. Multivariate factor analysis using orthogonal factor rotation showed that approximately 83% of the observed variance in denitrification was explained by grouping experimental variables by microbial activity, N2O‐N emission, temperature, and nitrification. The grouping of soil variables was useful in explaining the importance of different soil processes in regulating denitrification. These denitrification activity data demonstrate the possibility for significant N losses, amounting to 12.5% of the applied fertilizer N, from poorly drained cropping systems.
Chromate Extraction from Surfactant‐Modified Zeolite Surfaces
Authors: Li Zhaohui
Published: July 2010

Surfactant‐modified zeolites (SMZ) as permeable barriers for remediation of chromate contaminated groundwater have shown great promises due to their low cost, excellent hydraulic conductivity, and instantaneous chromate sorpfion. However, the stability of chromate sorbed on SMZ surfaces need to be evaluated. In addition, effective extractants for chromate extraction may lead a way to regenerate the chromate‐saturated SMZ. In this research 10 different published methods were tested for chromate extraction. The sorbed chromate is relative resistant to most extractants, a prerequisite for SMZ to be used as permeable barriers. The methods using phosphate buffer and using hydroxide solution extracted <10% of the spiked and sorbed chromate. On the other hand, a carbonate‐hydroxide solution as the extractant removed 90 to 100% sorbed chromate. The maximum extraction of chromate by the carbonate‐hydroxide solution may indicate that it is the high concentration of carbonate that makes the substitution of sorbed chromate by carbonate possible, while the high pH resulting from NaOH addition ensures that the dominating anion species is CO2−3 instead of HCO−3.
Agricultural Phosphorus and Eutrophication: A Symposium Overview
Authors: Daniel T. C. , Sharpley A. N. , Lemunyon J. L.
Published: July 2010

Phosphorus in runoff from agricultural land is an important component of nonpoint‐source pollution and can accelerate eutrophication of lakes and streams. Long‐term land application of P as fertilizer and animal wastes has resulted in elevated levels of soil P in many locations in the USA. Problems with soils high in P are often aggravated by the proximity of many of these areas to P‐sensitive water bodies, such as the Great Lakes, Chesapeake and Delaware Bays, Lake Okeechobee, and the Everglades. This paper provides a brief overview of the issues and options related to management of agricultural P that were discussed at a special symposium titled, “Agricultural Phosphorus and Eutrophication,” held at the November 1996 American Society of Agronomy annual meetings. Topics discussed at the symposium and reviewed here included the role of P in eutrophication; identification of P‐sensitive water bodies; P transport mechanisms; chemical forms and fate of P; identification of P source areas; modeling of P transport; water quality criteria; and management of soil and manure P, off‐farm P inputs, and P transport processes.
Cadmium Solubility and Phytoavailability in Sludge‐Treated Soil: Effects of Soil Organic Carbon
Authors: Hyun Hae‐nam , Chang A. C. , Parker D. R. , Page A. L.
Published: July 2010

Slow mineralization of organic matter in sewage sludge‐treated soil could release metals into more labile forms, which would then be more available for plant absorption. We examined the effect of soil organic matter decomposition on the phytoavailability of Cd in soils which, prior to this experiment, received 0 (control), 22.5, 45, 90, 180 Mg ha−1 yr−1 of sewage sludge for 6 yr. At the commencement of the experiment, one‐half of the experimental plots continued to receive sewage sludge application`at the prescribed rates. Sewage sludge application in the other half of the plots was terminated. All treated soils were cropped to Swiss chard (Beta vulgaris) twice each year for 10 yr and the soil was sampled after each crop harvest. When sewage sludge applications were teenated, the soluble Cd concentrations of the sludge‐treated soil were higher than those in the control soils and did not decline significantly over the next 10 yr. With continuous sludge applications, the soluble Cd concentration of sludge‐treated soils increased with each incremental addition of sludge for the same 10 yr. In soils receiving continuous sewage sludge inputs, the organic C content continued to rise with sludge inputs. After the termination of sludge application, organic C content of the sludge‐treated soils decreased by approximately 40% over the 10‐yr study. There was no indication that the soluble Cd concentration or the phytoavailability of Cd in the sludge‐treated soils increased as the organic C in these soils declined over the 10 yr following termination of sewage sludge application.
Effect of Polyaromatic Hydrocarbons in Soil on Arbuscular Mycorrhizal Plants
Authors: Leyval C. , Binet P.
Published: July 2010

The rhizosphere of plants plays a role in the bioremediation of soils polluted with organic pollutants such as polyaromatic hydrocarbons (PAHs). Arbuscular mycorrhizal (AM) fungi provide a direct link between soil and plant roots, but very little is known of the interactions between PAHs and AM fungi. We studied the effect of PAHs on mycorrhizal colonization in polluted soil, and the effect of AM fungi on plant growth in these soils. Leek (Allium porrum L.), maize (Zea mays L.), ryegrass (Lolium perenne L.), and clover (Trifolium subterraneum L.) were grown in pots containing a soil artificially contaminated with increasing concentrations of anthracene or mixed with an industrial soil polluted with PAHs. Mycorrhizal colonization by the indigenous AM population of the nonpolluted soil was not significantly affected by the addition of anthracene up to 10 g kg−1. However, mycorrhizal colonization of clover and leek decreased when the industrial soil was added to the nonpolluted soil, while maize and ryegrass colonization was not affected. The effect of PAHs on plant survival and growth depended on plant species. Inoculation of ryegrass with Glomus mosseae improved plant survival and plant growth in the industrially polluted soil. At 5 g of PAH kg−1 only mycorrhizal plants survived. Mycorrhizal fungi may contribute to the establishment and maintenance of plants in PAH‐polluted soils.
Acceleration of 1,3‐Dichloropropene Degradation by Organic Amendments and Potential Application for Emissions Reduction
Authors: Gan J. , Yates S. R. , Crowley D. , Becker J. O.
Published: July 2010

Emissions of the fumigant 1,3‐dichloropropene (1,3‐D) can result in degradation of air quality in certain areas. The high emission potential of 1,3‐D is caused by its rapid diffusion and comparatively slow degradation in soil. One approach to reduce the emission is to enhance the surface soil's capacity to degrade 1,3‐D. We investigated the capability of two organic amendments, a composted manure (CM) and a biosolid‐manure mix (BM), to accelerate 1,3‐D degradation in soil. Degradation of 1,3‐D was significantly enhanced in amended soils compared to the unamended soil, and the degree of acceleration varied with the type as well as the rate of amendment. Compost manure was more effective in stimulating 1,3‐D degradation than the less decomposed BM; even at an amendmen/soil ratio as low as 1:40 (w/w), degradation in the CM‐amended soil was two times faster than that in the unamended soil. The acceleration in CM‐amended soils was a combined result of enhanced chemical and microbial degradation, since sterilization only partially reduced the enhanced degradation. The reduction of 1,3‐D emissions by surface application of organic amendments was illustrated in a column experiment: 1,3‐D emission loss after injection at 30 cm was 30% from an unamended Arlington sandy loam (a coarse‐loamy, mixed, thermic Haplic Durixeralf), but decreased to only 16% in the column containing 5% CM in its top 5‐cm layer.
Effect of Application Methods on 1,3‐Dichloropropene Volatilization from Soil under Controlled Conditions
Authors: Gan J. , Yates S. R. , Wang D. , Ernst F. F.
Published: July 2010

Emissions of fumigants can be an important source of air pollution at soil fumigation sites, and the high emission rates result partly from the use of application methods that are high in volatilization potential. In this study, we compared volatilization of fumigant 1,3‐dichloropropene (1,3‐D) fr.om a sandy loam in 60‐cm packed columns after applied by different methods. The most volatilization was found with injection into uncovered soil at a shallow depth (e.g., 56% loss for the 20‐cm injection) and application via surface drip irrigation (>90%). Volatilization fluxes and cumulative losses, however, rapidly decreased as the injection depth was increased, and the total loss was only 27% for the 40‐cm injection. The commonly used polyethylene plastic was ineffective in reducing the volatilization because of its high permeability to 1,3‐D. Water application after the 20‐cm injection resulted in substantially reduced volatilization, but the least loss (22%) was obtained when an emulsifiable formulation of 1,3‐D, Telone SL, was drip‐applied to the subsurface at 20 cm. Our results indicate that variables most influencing 1,3‐D volatilization are injection depth and water management. By optimizing these variables, application methods with low emission potential can be developed.
The Fate of Groundwater Ammonium in a Lake Edge Wetland
Authors: Lusby Fleur E. , Gibbs Max M. , Cooper A. Bryce , Thompson Keith
Published: July 2010

The removal of ammonium—nitrogen (NH4‐N) from groundwater flowing through a grey willow (Salix cinerea) and native raupo (Typha orientalis) lake edge wetland was investigated over 10 mo. Monthly groundwater sampling showed that more than 95% of incoming NH2‐N was removed by the wetland. Laboratory assays found that the potential for NH4‐N removal by nitrification and subsequent denitrification was significantly higher in the organic surface sediments than in deeper, sandy, root zone sediments. In a laboratory 15N‐tracer experiment, Salix cinerea and Typha orientalis readily assimilated NH2‐N from the root zone and were found to enhance the natural diffusion of NH4‐N up through the organic sediment layer and into the overlying water. Estimated rates of removal of NH2‐N by coupled nitrification‐denitrification and plant assimilation were 8 to 9 mg of N m−2 d−1 and 9 to 46 mg of N m−2 d−1, respectively. Assimilated N, returned to the overlying water‐sediment surface via litter fall may be subject to sequential mineralization, nitrification, and denitrification, resulting in gaseous N loss. Sixty‐five percent of the 15N in Salix leaf litter was transformed in such a way. The results of this study indicate that plants play a central role in the NH4‐N processing capacity of wetlands. The relevance of our findings to constructed wetland design is discussed.
Field Response of Soil Physical Properties to Sewage Sludge
Authors: Lindsay Billie J. , Logan Terry J.
Published: July 2010

An anaerobically digested sewage sludge was applied to a Miamian silt loam (fine, mixed, mesic Typic Hapludalfs) at rates of 0, 7.5, 15, 30, 60, 90, 120, 150, 188, 225, and 300 Mg/ha. Surface soils (0–15) cm were sampled 4 yr after sludge application and analyzed for bulk density, particle density, porosity, saturated hydraulic conductivity, moisture retention, aggregate stability, shrinkage, liquid and plastic limits, and total C. Bulk density significantly decreased, and porosity, moisture retention at 5.9 kPa, 33 kPa, and 1.5 MPa, percentage water stable aggregates, mean weight diameter of aggregates, and liquid and plastic limits increased with increasing sludge application. Sludge application had no significant effect on particle density, available water, saturated hydraulic conductivity, and shrinkage. Physical property responses to sludge application were linear except aggregate stability and mean weight diameter of aggregates that showed a maximum effect at 60 Mg/ha sludge application rate. Organic C increased linearly with sludge application, and 4 yr after application there was three times as much C in the 300 Mg/ha plots as in the zero sludge control plots. It is likely that many of the observed differences in soil physical properties are due to effects of added organic matter and these effects have persisted for at least 4 yr.
Transport and Persistence of Pesticides in Alluvial Soils: I. Simazine
Authors: Cogger C. G. , Bristow P. R. , Stark J. D. , Getzin L. W. , Montgomery M.
Published: July 2010

Pesticide leaching is a concern in the alluvial valleys of western Washington, where high‐value crops are grown in soils with water tables <m deep. We conducted this project to determine the long‐term leaching pattern of simazine [2‐chloro‐4,6‐bis‐(ethylamino)‐s‐triazine] applied to red raspberry (Rubus idaeus L.) and strawberry (Fragaria × ananassa Duch.). Simazine was applied to strawberry and raspberry in paired plots at two sites. Strawberry received a split application (total 2.2 kg ha−1) in August and November, and raspberry received a single 4.5 kg ha−1 application in November. We applied simazine yearly from 1986 to 1989, and sampled soil (to 180 cm) and shallow groundwater monthly until April 1991, and at one site again in 1994. Most of the simazine remained in the surface 15 cm of the soil or degraded, but small amounts moved downward. Preferential flow soon after application was not the main cause of downward movement. Simazine was persistent, with disappearance half lives of 128 and 175 d at the two sites the first year. Some simazine remained in the soil 4 yr after the final application. Simazine was most mobile beneath raspberry at one site. This site had finer texture and slightly more organic matter, but a lower Kd for simazine than the other site. Small amounts of simazine reached shallow groundwater beneath both crops. The observed simazine leaching peak was more asymmetric than the peak predicted by the PRZM‐2 model, an indication of nonequilibrium adsorption‐desorption effects on simazine movement.