bluuebunny/crossref_metadata_2025 huggingface dataset:
Heavy Metal Displacement in a Sandy Soil at the Field Scale: I. Measurements and Parameterization of Sorption
Authors: Streck Thilo , Richter Jörg
Published: July 2010

Downward displacement of cadmium (Cd) and zinc (Zn) at the field scale was investigated in a sandy soil irrigated under controlled conditions for 29 yr with a total of 12.8 m3 m−2 of municipal wastewater. On a 0.86 ha grid a total of 720 samples was taken from 0 to 1.2 m depth. Cadmium and Zn contents were determined in all samples by extraction with 0.025 M ethylene‐diamine‐tetra‐acetic acid (EDTA) on the assumption that this fraction represents the solution and sorbed phases in soil. Solution phase concentrations of 480 samples were estimated by equilibrating the samples with 0.0025 M CaCl2. Heavy metal downward displacement is spatially highly variable. Five percent of EDTA‐extractable Cd and Zn were found below 0.7 and 0.9 m depth, respectively. Spatial variability of heavy metal load as measured by recovered mass per unit area reflects the geometry of irrigation systems employed. Measured sorption equilibria could be well described as a function of organic C content and pH by extending the Freundlich equation.
Boric and Silicic Acid Adsorption and Desorption by a Humic Acid
Authors: Meyer Michael L. , Bloom Paul R.
Published: July 2010

Boron is an essential plant nutrient having a narrow range between concentrations that cause deficiency or toxicity symptoms in plants. Boric acid (B[OH]3) and silicic acid (Si[OH]4) have many chemical similarities and both are thought to be associated with organic matter in soils. The objectives of this study were to investigate the variation in boric and silicic acid adsorption and desorption in low ash humic acid over a range of B and Si concentrations and pH values. Borate adsorption by humic acid increased significantly from pH 3.67 to 8.70. The data fit the Freundlich equation better than the Langmnir model at high pH; however, both fit well at pH < 7. Adsorption was greatest at pH 8.5 to 10 and decreased at pH >10. The constant capacitance model predicted B adsorption and the pH maximum using catechol as the adsorbing ligand and published stability constants. The predicted adsorption envelope was narrower than experimental data. This could be due to variation in stability constants that result from variation in substitution on other sites on the aromatic ring. Inclusion of glucose and salicylate in the adsorption model would also broaden the adsorption envelope by increasing adsorption at pH > 9 and < 9, respectively. Desorption of B from humic acid appears to show hysteresis effects at pH 7.6 but not at pH 8.15 and 8.7. Generally, B will be easily released from HA as solution concentrations decrease. Silicic acid did not adsorb in humic acid. The stability constant of Si‐catechol humate complexes is apparently too low for adsorption of Si to occur at the pH and solution concentrations used in this experiment.
Pig Slurry Amendment and Herbicide Coapplication Effects on s‐Triazine Mobility in Soil: An Adsorption‐Desorption Study
Authors: Businelli Daniela
Published: July 2010

Amendments with pig slurry containing dissolved organic matter (PSDOM) and herbicide coapplication are agronomical practices that can influence the mobility of herbicides through the soil profile, thus enhancing the risk of groundwater pollution. Batch equilibrium experiments were conducted on a clay loam soil to quantify the influence of these practices on the sorption and desorption of three s‐triazine herbicides: atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐l,3,5‐triazine), prometryn (2,4‐bis (isopropylamino)‐6‐methylthio‐1,3,5‐triazine), and terbuthylazine (2‐tert‐butylamino‐4‐chloro‐6‐ethylamino‐ 1,3,5‐triazine). Soil adsorption and desorption capability for atrazine was reduced when it was applied with the other two s‐triazines in the batch experiment solution. The PSDOM treatment immediately after atrazine application had a greater enhancing effect on its desorption than treatment with a 0.01 M CaCl2 solution alone. No enhanced desorption effect was observed on any of the three s‐triazines when PSDOM treatment was carried out after repeated 0.01 M CaCl2 treatments. Soil treatment with PSDOM before atrazine application enhanced soil adsorption capability for the herbicide. On calculating the balance between the adsorbed and desorbed atrazine in the PSDOMtreated soil, a fourfold increase of the atrazine retained was observed. Therefore, to reduce the risk of groundwater s‐triazine pollution, pig slurry should be applied to the soil before herbicide treatment.
Spatial Variability of Throughfall in a Subtropical Rain Forest in Taiwan
Authors: Lin Teng‐Chiu , Hamburg Steven P. , King Hen‐Biau , Hsia Yue‐Joe
Published: July 2010

Eight rainfalls were intensively sampled in a subtropical rain forest in northeastern Taiwan. This study, carried out at Fu‐shan Experimental Forest was designed to examine variability of throughfall characteristics. The volume and chemistry of the throughfall associated with individual rains have a high degree of spatial variability, with throughfall chemistry more variable than volume. When data from all of the storms were combined, there was lower variability than that seen with individual storms, largely as a result of a lack of consistent storm to storm spatial variation. Thus, individual storms cannot be used to represent the seasonal or annual pattern of spatial variation in throughfall chemistry or volume of the study forest. Twenty samples were required to estimate throughfall volume within 10% of the population mean with 95% confidence for individual storms. Yet, more than 100 samples were required to estimate the throughfall chemistry of some ions (e.g., H+). When the data from all eight storms were combined, 7, 20, and 25 samples were necessary to estimate throughfall volume, ion concentrations, and ion fluxes (except for Mg2+ and H+) within 10% of the population mean with 95% confidence. In the absence of estimates of spatial variation, differences in sampling protocols among throughfall studies make comparisons of throughfall characteristics difficult. In this study three funnels were used in tandem to capture small scale variability at each sample location, thus reducing spatial variability of throughfall chemistry.
Fate of Carbon‐14 Diazinon during the Composting of Yard Trimmings
Authors: Michel Frederick C. , Reddy C. Adinarayana , Forney Larry J.
Published: July 2010

The fate of lawn care pesticides during the composting of yard trimmings is largely unknown. In this study we investigated the fate of diazinon (0,0‐diethyl 0‐[2‐isopropyl‐6‐methyl‐4‐pyrimidinyl] phosphorothioate), the most widely used lawn care pesticide, during the composting of a mixture of leaves and grass (2:1 w/w). The yard trimmings were amended with [Δ‐2‐14C] labeled diazinon (10 mg kg−1 wet wt.) and composted in a laboratory scale compost system for 54 d. During composting, 48% of the initial total organic matter (OM) was lost as CO2, the pH increased from 6.2 to 8.2, the oxygen uptake rate declined from 3.5 to 0.09 (mg O2 g OM−1 h−1), the humification index dropped from 1.0 to 0.37, and 11% of the 14C‐diazinon was mineralized to 14CO2. Initially most of the added 14C‐diazinon was ether extractable (83%) but <1% was ether extractable after composting. A water extract of the finished compost contained 36% of the added 14C. Thin layer chromatography and mass spectrometry analyses of this water extract indicated that the 14C was in the form of 2‐isopropyl‐6‐methyl 4‐hydroxy pyrimidine (IMHP) a hydrolysis product of diazinon. The remaining 14C was either unextractable (32%), or was associated with a high molecular weight fraction of a 0.1M NaOH/Na4P2O7 extract of the finished compost (19%). Volatilization of diazinon was negligible (0.2%). The results show that during the composting of yard trimmings, a relatively small amount of diazinon is mineralized to CO2, while a majority of the diazinon is converted to potentially leachable, but less toxic IMHP, high molecular weight residues, and unextractable residues that are presumed to have low bioavailability.
Kinetics of Cadmium Release from Soils as Influenced by Organic Acids: Implication in Cadmium Availability
Authors: Krishnamurti G. S. R. , Cieslinski G. , Huang P. M. , Van Rees K. C. J.
Published: July 2010

The low‐molecular‐weight organic acids (LMWOAs) secreted by plant roots modify the mobility of Cd through formation of soluble complexes in the soil rhizosphere; the kinetics of Cd release as influenced by organic acids and its impact on Cd bioaccumulation remains to be established. The influence of LMWOAs (10−3 and 10−2 M), viz., acetic, citric, oxalic, fumaric, and succinic acids, which are present in the soil rhizosphere, on the kinetics of Cd release from selected soils (Luseland, Waitville, and Jedbergh) of Saskatchewan, Canada, was investigated at 25°C and at an ionic strength of 0.1 M NaNO3. It was observed that the Cd release from the soils increased initially up to a reaction period of about 2 h and then slowly decreased with time. With time, the LMWOAs were apparently microbially degraded and the soil solution Cd2+, which was transformed from the Cd‐LMWOA complexes by microbial degradation, was adsorbed onto the negatively charged soil particles. Increasing amounts of Cd were released from the soils to the soil solution with the renewal of LMWOAs after every 2 h. The short‐term (reaction period of 0.25 to 1 h) kinetics of Cd release from the soils was described by a parabolic diffusion kinetic model. The overall diffusion coefficient of the Cd release from the soil and the Cd released by the renewal of LMWOAs followed the same trend as the Cd availability index of the soils: Luseland >> Waitville > Jedbergh. Thus, the results presented in this investigation indicate the importance of the kinetics of the Cd release from the soils by the LMWOAs excreted by root exudates in understanding the availability of soil Cd.
Identification of Coniferous Forests with Incipient Nitrogen Saturation through Analysis of Arginine and Nitrogen‐15 Abundance of Trees
Authors: Näsholm Torgny , Nordin Annika , Edfast Ann‐Britt , Högberg Peter
Published: July 2010

Stands of Norway spruce [Picea abies (L.) Karst.] differing in throughfall N deposition and NO3− leaching were investigated to determine if arginine concentrations and δ15N abundances of needles could be used to predict NO3− leaching from stands. Twenty‐three stands, all located in southern Sweden, were sampled and five of these had average NO3− concentrations > 0.1 mg NO3−‐N L−1 in soil water at a 50‐cm depth. Arginine concentrations and δ15N abundances of needles were significantly higher for sites that exhibited NO3− leaching. The δ15N enrichment (ε), i.e., difference between foliage and soil organic matter in δ15N, showed less variation than δ15N of needles alone in regressions against NO3− leaching and was, thus, a better predictor of leaching. All sites that exhibited N leaching had arginine concentrations > 5 µmol g dw−1 and ε > −0.5 (‰) and thus, there was strong correlation between arginine and ε values. To test if arginine accumulation, as such, can affect the δ15N of needles, arginine and δ15N were determined for Scots pine (Pinus sylvestris L.) trees given different amounts of N fertilizer. Although fertilization caused a dramatic increase in arginine concentrations of needles, no immediate change in δ15N was observed. A hypothesis is proposed to explain the causal linkage between elevated arginine and δ15N of needles and leaching of N. Thus, arginine accumulation in trees corresponds to decreased uptake rates of NH4+ leaving NH4+ ions available for nitrification. During nitrification, discrimination against the heavier takes place resulting in a depleted NO3− pool and enriched NH4+ pool. Preferential uptake of NH4+ by conifer trees will then lead to elevated 15N abundance of needles. It is concluded that N leaching coniferous forests can be identified through analysis of arginine and δ15N of needles.
Laboratory‐Scale Measurements and Simulations of Effect of Application Methods on Soil Methyl Bromide Emission
Authors: Gan J. , Yates S. R. , Spencer W. F. , Yates M. V. , Jury W. A.
Published: July 2010

Methyl bromide (bromomethane, MeBr), which originates from the oceans, fumigation, and a few other sources, is reportedly contributing to the ozone depletion in the stratosphere. Due to the heavy reliance on this fumigant in the production of many crops, it is of particular importance to accurately quantify the atmospheric input of MeBr arising from agricultural uses, and develop feasible measures to minimize these emissions. In this study, we determined the effect of two important application variables, surface tarp and injection depth, on MeBr transport and transformation in the soil and its emission from the soil surface under controlled conditions. Following 20‐ and 30‐cm injections, covering the soil surface with 1‐mil (0.025 mm) high‐density polyethylene film resulted in an average of 48% reduction in MeBr emission. Increasing the injection depth from 20 to 60 cm caused a decrease in MeBr emission of 54% under untarped conditions and 40% under tarped conditions. The influence of application methods on MeBr atmospheric emissions should be considered when estimating the contribution of agricultural fumigation to the overall atmospheric MeBr burden on a global scale. The results also indicate that MeBr emission after soil fumigation may be substantially minimized by using surface tarpaulins and deep injections.
Nitrogen Cycling in Piedmont Vegetated Filter Zones: II. Subsurface Nitrate Removal
Authors: Verchot Louis V. , Franklin E. Carlyle , Gilliam J. Wendell
Published: July 2010

Subsurface flow often constitutes the major pathway for movement of dissolved nutrients such as NO3‐N from agricultural fields. The objectives of this study were (i) to determine the changes in shallow groundwater chemistry along a piezometric gradient from agricultural fields, across grass‐vegetated field edges and through adjacent forest on two Piedmont watersheds and (ii) determine the relative importance of dilution, denitrification, and plant uptake in subsurface NO3 attenuation. We monitored changes in groundwater chemistry at three depths along a piezometric gradient from an agricultural field through a grass field edge and through a forested filter zone (FFZ). We measured marked decrease in nitrate concentrations from 8 to 10 mg L−1 at the field edge to almost 0 at the forest edge; Cl concentrations remained within the range of 8 to 10 mg L−1, suggesting that dilution was not an important factor in NO3 concentration reductions. At a third site, we introduced NO3‐N and a conservative tracer, bromide, into the soil profile at both the grass‐vegetated field border and the forested area, to determine mechanisms responsible for the observed decrease in NO3‐N concentrations. Using ion concentration ratios we determined that nitrate attenuation in the grass‐vegetated field edge was low compared to the forest. Nitrate loss in the forest was almost exclusively through denitrification; plant uptake was insignificant in these experiments. Although grass‐vegetated field borders were less effective than riparian forests at NO3‐N removal, considerable reductions were observed in these areas on the experimental watersheds. Similar reductions would be expected over shorter distances in riparian forests.
Agricultural Chemicals in Alluvial Aquifers in Missouri after the 1993 Flood
Authors: Heimann D. C. , Richards J. M. , Wilkison D. H.
Published: July 2010

Intense rains produced flooding during the spring and summer of 1993 over much of the midwestern USA including many agricultural areas of Missouri. Because of potential contamination from floodwater, an investigation was conducted to determine the changes in concentrations of agricultural chemicals in water samples from alluvial wells in Missouri after the flood. Water samples from 80 alluvial wells with historical data were collected in March, July, and November 1994, and analyzed for dissolved herbicides, herbicide metabolites, and nitrate (NO3). There were no statistically significant differences in the distribution of alachlor ((2,chloro‐2′‐6′‐diethyl‐N‐[methoxymethyl]‐acetanilide), atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1, 3, 5 triazine), and nitrate concentrations between pre‐ and postflood samples (α = 0.05). The detection frequency of alachlor and atrazine in postflood samples was generally lower than the frequency in preflood samples. Analyses of agricultural chemicals in water samples from an intensely sampled well field indicate significant differences between the distribution of dissolved P concentrations in pre‐ and postflood samples (α = 0.05). However, no significant differences were detected between the pre‐ and postflood distributions of NO3 or ammonia concentrations. Because of the numerous sources of temporal variability and the relatively short record of water‐quality data for the study wells, a cause‐and‐effect relation between changes in agricultural chemical concentrations and a single factor of the 1993 flood is difficult to determine. Based on the results of this study, the 1993 flood did not cause widespread or long‐term significant changes in concentrations of agricultural chemicals in water from alluvial aquifers in Missouri.
Selenium Speciation of Marine Shales, Alluvial Soils, and Evaporation Basin Soils of California
Authors: Martens D. A. , Suarez D. L.
Published: July 2010

The surface exposed shales of the Moreno and Kreyenhagen Formations are considered to be the sources of selenium (Se) that have enriched soils of the west‐central San Joaquin Valley of California. Although the total Se content for the source shales and the resulting alluvial, seleniferous soils has been reported, the distribution of Se oxidation states has not been determined in these materials. This study investigates the Se speciation trends in the seleniferous source shales, the adjacent alluvial soils, the San Luis Drain sediment to the Kesterson evaporation pond soils. The surface‐exposed Moreno shales (5.21 mg total Se kg−1) had half of the Se content of the less exposed Kreyenhagen shale (10.94 mg total Se kg−1). The elemental Se (Se0) concentration was similar in the two shales, but the selenate (Se + VI), selenite (Se + IV), and selenide (Se‐II) concentrations were lower in the Moreno shale as compared with the Kreyenhagen shale. The Se in the San Luis Drain sediment (83.8 mg total Se kg−1) was enriched in the Se0 and the Se‐II fractions (91.4% of Se inventory). The soils of the Kesterson evaporation pond 4 (47.8 mg total Se kg−1), 7 (6.7 mg total Se kg−1), and 11 (5.4 mg total Se kg−1) were also enriched in Se with 86, 76, and 48% of the Se inventory present in the Se0 and Se‐II fractions, respectively. The organic C content also decreased in the sequence, San Luis Drain, Kesterson pond 4, 7, and 11, from 33.3, 26.7, and 19.3 g C, to 15.1 g C kg−1 soil material, respectively, suggesting a relationship between Se concentrations and organic C levels. A linear relationship between the sum of (Se‐II and Se0)‐Se and organic C levels (R2 = 0.96*; significant at the 0.05 level) was noted for the analyzed San Luis Drain sediment and the Kesterson soils. For the nine soil materials, an exponential relationship (R2 = 0.96) was determined for the sum of (Se‐II and Se0)‐Se and organic C contents, suggesting that the Se in the materials tested was highly associated with the soil organic matter fraction. An additional 12 Se analyses and organic C contents from Se contaminated semiarid and irrigation drainage water evaporation basin soils obtained from the literature closely fit the exponential function established for the nine soil materials. The results suggest that an initial release of organic‐associated Se would be expected with increased C oxidation, along with a slower, long‐term release of the refractory Se, due to the reversion of the former Kesterson wetland evaporation pond ecosystem back to a native semiarid grassland.
Arsenic Transport in Contaminated Mine Tailings following Liming
Authors: Jones C. A. , Inskeep W. P. , Neuman D. R.
Published: July 2010

The practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize arsenic (As), due to the pH dependence of As sorption reactions on oxide minerals and layer silicates. The objectives of this study were to determine the effects of liming on As mobility in mine tailings and identify possible mechanisms controlling As mobilization with increased pH. Six mine tailing samples obtained from an abandoned copper smelter near Anaconda, Montana were analyzed for total As and soluble constituents using saturated paste extractions. Concentrations of soluble As among the six samples did not correlate with total As, but were more closely related to pH. Saturation indices with respect to known metal arsenate solid phases suggested that metal arsenate solid phases were not controlling soluble As in these samples. Two low pH samples (pond tailings and reprocessed tailings) were chosen for more detailed chemical characterization and unsaturated column transport experiments before and after liming. Soluble As concentrations measured in column effluent increased by factors of 10 (reprocessed tailings, RT) to 400 (pond tailings, PT) following liming. Sequential extractions of these tailing samples showed that the PT contained significantly higher “labile” As relative to the RT, consistent with amounts of As mobilized after liming. Further characterization of these samples using scanning electron microscopy (SEM) and energy dispersive analysis of x‐rays (EDAX) suggested that these samples do not contain discrete metal arsenate solid phases. Based on this suite of experimental data, increased mobility of As with liming appears to be consistent with the pH dependence of sorption reactions of As on Fe oxide minerals rather than dissolution‐precipitation reactions involving As.
Aerobic Degradation Potential Assessment from Oxygen and Carbon Dioxide Soil Gas Concentrations in Roadside Soil
Authors: Ostendorf D. W. , DeGroot D. J. , Pollock S. J. , Long L. J.
Published: July 2010

The application of calcium magnesium acetate [CMA; Ca0.3Mg0.7‐(C2H3O2)2] to highways as a deicing agent induces aerobic acetate degradation by microorganisms in the capillary fringe, which may reduce O2 demand in the underlying groundwater. We assessed this aerobic degradation potential by computing the diffusive fluxes of O2 and CO2 from measured soil gas concentrations in the unsaturated zone of a mildly acidic roadside soil. The fluxes were relevant to the potential assessment because O2 is consumed and CO2 is generated by the aerobic degradation of organic substrates such as acetate. Soil gas O2 and CO2 were measured on a monthly basis in tubing clusters in the unsaturated zone over a 2‐yr period using portable meters. Quasi‐steady gaseous diffusion models were calibrated with the data, showing that O2 diffused into the fringe at a rate that was proportional to the exiting diffusive flux of CO2. The modeled fluxes were consistent with an independent estimate of acetate‐based microcosm reaction rates in the capillary fringe. Roadside soils have the potential to significantly degrade CMA under aerobic conditions before the deicing agent reaches the water table, thus reducing O2 demand in the groundwater.
Fate of Methabenzthiazuron in Calcareous Soils from Southeastern Spain
Authors: Romero T. E. , Barifouse M. M. , Rasero F. S. , Peña H. A. , de la Colina G. C. , Dios C. G.
Published: July 2010

Adsorption, incubation, and soil column experiments with methabenzthiazuron [1‐(1,3‐benzothiazol‐2‐yl‐)‐1,3‐dimethylurea] (MBT) were carried out on soils from the surrounding fertile plain of Granada (southeast Spain). The isotherms of MBT adsorption followed the Freundlich model. Due to the similar physico‐chemical and mineralogical properties of the soils from this area, the Kf values were only correlated with soil clay content, smectite content, and soil surface area. Methabenzthiazuron degradation did not occur in the soils, under our experimental conditions, for incubation periods of up to 42 d. Methabenzthiazuron was not detected in the eluates from the clay and silt loam soil columns; it was retained in the first 3‐cm layer and the retardation factor values, R, were 24 and 14, respectively. A computation model simulating a uniform flow of water and instantaneous adsorption‐desorption equilibrium is suitable for the description of MBT in the G‐8 soil but showed an overestimation in the G‐11 soil column.
Field Assessment of Sludge Metal Bioavailability to Crops: Sludge Rate Response
Authors: Logan T. J. , Lindsay B. J. , Goins L. E. , Ryan J. A.
Published: July 2010

We conducted a field study (1991–1995) of trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations in two crops, corn (Zea mays L.) and lettuce (Lactuca sativa L.) as affected by a one‐time application of an anaerobically digested sewage sludge to Miamian silt loam (fine, mixed, mesic Typic Hapludalf) in Columbus, OH to determine the nature of the uptake response over a wide range of sludge application rates (0, 7.5, 15, 30, 60, 90, 120, 150, 188, 225, and 300 Mg/ha dry solids). Cadmium, Cu, Ni, Pb, and Zn sludge concentrations were 46, 433, 67, 185, and 2334 mg/kg, respectively. Soil pH did not vary significantly with sludge application (6.1–7.5), while electrical conductivity, total C and total organic N increased linearly with sludge application and declined over time. Soil metals extracted with 0.005 M EDTA in 0.01 M Ca(NO3)2 increased linearly with total soil concentration and generally declined over time. Cadmium, Cu and Zn concentrations in corn increased significantly with sludge application, while Ni and Pb levels were low compared to the control. Cadmium, Cu, and Zn concentrations in corn exhibited a plateau‐type response that could be modeled with the Mitscherlich equation. Lettuce concentrations increased linearly with sludge application for Cd, Cu, and Zn in all years, and linear regression slopes generally declined and stabilized after the first 2 yr.
Automated Gas Chromatographic System for Rapid Analysis of the Atmospheric Trace Gases Methane, Carbon Dioxide, and Nitrous Oxide
Authors: Loftfield N. , Flessa H. , Augustin J. , Beese F.
Published: July 2010

To study the fluxes of the radiative active trace gases CH4, CO2, and N2O, a gas sampling and analytical device was developed. It is a useful tool for accurate gas sampling in the field and enables the subsequent fully automated analysis of the gas samples in the laboratory. The computer‐controlled analytical system consists of a gas chromatograph equipped with a flame ionization detector (FID), an electron capture detector (ECD), and a pressure‐controlled autosampler for 64 sample containers. The system automates sample injection, the analysis of CH4, CO2, and N2O in each sample and the subsequent evacuation of the sample containers. It is equipped with a second alternative sample inlet for manual syringe injection. This inlet is suitable for analyzing small volumes of gas samples (3 mL). The gas sampling system for use in the field consists of evacuated sample bottles (100 mL) with Teflon cocks combined with a small battery‐driven field sampler with a pressure sensor. This device enables an on‐site control of the vacuum integrity of the sample bottles during sampling and purging of the dead volumes between the sampler induction pipe and the sample container.
Atrazine Sorption at the Field Scale in Relation to Soils and Landscape Position
Authors: Novak J. M. , Moorman T. B. , Cambardella C. A.
Published: July 2010

Understanding the spatial variation of herbicide sorption in soils is important in determining the potential for leaching at the field scale. Our objectives were to determine the spatial variability of atrazine sorption (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) at the field scale and to relate sorption partition coefficients (Kd) to landscape position and soil survey map units. Atrazine sorption was measured on 241 surface samples from a 6.25‐ha field using batch‐equilibration methods. Field‐scale variability in atrazine sorption coefficients was described using spherical semivariograms. Less than 20% of the total semivariance in atrazine Kd values was found at lag distances <10 m, indicating there was relatively little variability at this scale. Multiple regression analyses using pooled data revealed that atrazine sorption was influenced by soil organic C, pH, and, to a lesser extent, soil clay. We also evaluated the relationship of atrazine sorption to landscape position and soil series. Less atrazine was sorbed by soils from upland shoulder slopes than by soil in level and depressional areas (potholes). Soils from foot slope and back slope landscape positions were intermediate in atrazine sorption. The magnitude of atrazine sorption by soils in different landscape positions was also related to variations in soil organic C content, pH, and clay content. The greater sorption of atrazine by soils in the pothole depressions may reduce transport of this herbicide to tile lines that commonly drain these soils. Field‐scale maps of atrazine sorption based on landscape position more effectively predicted the actual distribution of the Kd values determined by kriging, than did maps based on soil series.
Modeling Alachlor Transport in Saturated Soils from No‐till and Conventional Tillage Systems
Authors: Xue S. K. , Chen Shulin , Selim H. M.
Published: July 2010

Batch and transport experiments with alachlor were conducted in soils from no‐till and conventional tillage systems. Alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] adsorption was described with equilibrium and multireaction models (MRM), and alachlor transport was evaluated with a multireaction transport model (MRTM) in undisturbed soils. In batch experiments, alachlor retention was greater in no‐till soil, based on the parameters of equilibrium adsorption models, than in soil with conventional tillage. This is due to the increase in organic matter. The MRM improved fitting of adsorption data compared with the equilibrium model. Preferential flow in no‐till led to earlier tritium and alachlor breakthrough and higher hydrodynamic dispersion coefficients, compared with conventional tillage. The breakthrough concentrations in no‐till soils are spread more widely over time than in conventional tillage soils, which showed a steady high peak concentration. The MRTM adequately described alachlor transport in soils of both systems. There was no significant difference in alachlor retention capacity between undisturbed soils of no‐till and conventional tillages, and among different cover crops, based on overall parameters fitted from alachlor breakthrough curves (BTCs) in undisturbed soil columns. The higher recovery and lack of irreversible reaction indicated that no‐till soils may have reduced bound alachlor residue during transport.
Temperature Dependence of Linuron Sorption to Three Different Agricultural Soils
Authors: Brücher Jörg , Bergström Lars
Published: July 2010

The temperature dependence of sorption of the herbicide linuron (N′‐(3,4‐dichlorophenyl)‐N‐methoxy‐N‐methylurea) was investigated in three texturally different soils (two sandy soils and one clay soil), each of which had been divided into three layers (0–30, 30–60, and 60–90 cm). Four different temperatures were used, ranging from 277 to 296 K (4–23°C). The sorption tests were conducted according to the Organization for Economic Cooperation and Development (OECD) standard batch‐equilibrium method, in which sieved soil was gently shaken with aqueous linuron solution for 16 to 25 h. In most cases, the sorption isotherms obtained could be described satisfactorily with the Freundlich sorption function. Analyses based on the derived isotherms and calculated Kd values revealed some general patterns: (i) sorption changed significantly (Kd values changed by a factor up to 15 at low linuron concentrations) over the investigated temperature range in all soils; (ii) the nonlinearity of the isotherms increased with decreasing temperature in the sandy soils, but decreased in the clay soil; and (iii) the temperature dependence of sorption was generally stronger at lower linuron concentrations. Based on the sorption data, the free energy and heat of sorption were calculated. These results were then used to describe sorption at any temperature and concentration within the ranges investigated.
Management Practices to Conserve Soil Nitrate in Maize Production Systems
Authors: Zhou Xiaomin , MacKenzie Angus F. , Madramootoo Chandra A. , Kaluli J. Wambua , Smith Donald L.
Published: July 2010

Residual soil N following maize (Zea mays L.) harvest is susceptible to leaching over winter. There is no available information regarding the combination of intercropping system and water table control to conserve soil N in maize production systems. A 2‐yr study was conducted to examine the effects of cropping systems (monocrop maize, and maize intercropped with annual Italian ryegrass [Lolium multiflorum Lam.]) and water table controls (free drainage, or subirrigation to establish water table depths at 70 and 80 cm below the soil surface) on conserving soil N, under climatic and soil conditions of southwestern Québec. The resulting six treatments were fertilized in the spring with 270 kg N ha−1. The effects of adding fertilizer at 0, 180, and 270 kg N ha−1 on monocrop maize with free drainage were also investigated. Soil cores of 1 m in depth were collected in the spring and fall of 1993 and 1994. In 1993, intercropping decreased the amount of NO−3‐N in the top 1 m of the soil profile by 47% (92.3 kg N ha−1) relative to monocropped maize at harvest time. Water table depth had less effect on soil NO−3‐N content than cropping system. Both increasing water table depth and monocrop maize enhanced downward movement of NO−3‐N during the growing season and following spring. More NO−3‐N was present in freely drained subsoil under maize given 270 kg N ha−1 than under maize given 180 kg N ha−1.
Correction of Limed‐Biosolid Induced Manganese Deficiency on a Long‐Term Field Experiment
Authors: Brown Sally , Angle J. S. , Chaney R. L.
Published: July 2010

Land application of lime‐stabilized biosolids has been reported to cause Mn deficiency in wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.]. Deficiencies were observed on a long‐term biosolid research experiment in Beltsville, MD, that had been established on a Galestown sand (sandy, siliceous, mesic Psammentic Hapludult) in 1976 with lime‐stabilized biosolids applied at 224 and 448 Mg ha−1. For the present study, a randomized complete block experiment was set up in plot areas of the original study. Soil amendments included MnO at 50, 100, and 200 kg ha−1, and MnSO4 at 200 kg ha−1. Plots were split with random half plots receiving a foliar application of MnSO4 at 0.5 kg ha−1 Mn. Soybean and wheat were double cropped for two seasons (1993–1995). Measured indexes of deficiency included youngest emerged blade (YEB) and grain Mn, plant chlorophyll, and yield. Wheat exhibited severe Mn deficiency for both seasons in the 224 Mg ha−1 biosolid plots. Only plants grown in the MnSO4‐amended soils were not deficient in Mn. Foliar Mn spray also alleviated Mn deficiency. Although soybean plants were not Mn deficient, plants in the MnSO4‐treated plots had higher YEB Mn concentrations. Soil extractions to reflect phytoavailable Mn, including Mehlich 1 (M1), Mehlich 3 (M3), and DTPA were conducted on moist soils. Results from M3 and DTPA extractions mirrored plant response. The M1 extraction did not predict plant response indicating that this extraction is not appropriate for predicting Mn deficiency in coarse‐textured high pH soils.
Phytoextraction of Cadmium and Zinc from a Contaminated Soil
Authors: Ebbs S. D. , Lasat M. M. , Brady D. J. , Cornish J. , Gordon R. , Kochian L. V.
Published: July 2010

To identify populations with the ability to accumulate heavy metals, approximately 300 accessions pertaining to 30 plant species were grown for 4 wk in a hydroponic media that approximated the nutrient and heavy metal composition of a soil contaminated with moderate levels of cadmium (Cd), copper (Cu), and zinc (Zn). The results indicated that several Brassica spp. exhibited moderately enhanced Zn and Cd accumulation. Selected accessions of Brassica juncea (L.) Czern, B. napus L., and B. rapa L. were then grown in pots with heavy metal‐contaminated soil to compare the Zn and Cd phytoextraction by these species to that of Thlaspi caerulescens J. & C. Presl, a known Zn and Cd hyperaccumulator, and two grass species, Agrostis capillaris L. and Festuca rubra L. The three Brassica spp. were the most effective in removing Zn from the contaminated soil, primarily because they produced more than 10 times the shoot biomass produced by T. caerulescens. When the soil was amended with Gro‐Power, a commercial soil amendment that improves soil structure and fertility, removal of Zn by plant shoots doubled to more than 30 000 mg Zn pot−1 (4.5 kg). The results suggest that for phytoremediation of metal‐polluted soils to be successful, a strategy should be considered that combines rapid screening of plant species possessing the ability to tolerate and accumulate heavy metals with agronomic practices that enhance shoot biomass production and/or increase metal bioavailability in the rhizosphere.
Persistence of Organic Contaminants in Sewage Sludge‐Amended Soil: A Field Experiment
Authors: Wilson S. C. , Alcock R. E. , Sewart A. P. , Jones K. C.
Published: July 2010

Digested sludge was applied to plowed arable and pasture grassland plots and losses of specific volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐p‐dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorophenols (CPs) monitored over 260 d. Sludge addition increased soil concentrations of all compounds in the plowed plot. VOCs, PCBs, and CPs concentrations declined to control plot values within 128 d of sludge amendment. Volatilization and biodegradation were considered important loss processes for these compounds. However, PCDD/F and of non‐o‐PCB 77 concentrations did not change consistently and remained elevated above control plot concentrations throughout the monitoring period. At Day 260 410 ± 53 ng ΣPCDD kg−1 and 250 ± 10 ng ΣPCDF kg−1 was detected in the sludged plot compared to 68 ± 9 ng ΣPCDD kg−1 and 170 ± 7 ng ΣPCDF kg−1 in the control plot. Data from the pasture plot has highly variable and differences between most contaminant concentrations in the sludged and control plots were insignificant. This was attributed to adherence of much of the applied sludge to vegetation rather than direct application to the soil surface and has important implications for elevated dietry intake of certain persistent organic compounds such as the PCDD/Fs. Further research is needed to evaluate the importance of sludge adherence to vegetation for human exposure to a range of contaminants detected in sludge. Contaminant movement to depth (20 cm) was not detected within 260 d for compounds monitored (VOCs and PCDD/Fs).
Fate of Summertime Airborne Organophosphate Pesticide Residues in the Sierra Nevada Mountains
Authors: Aston Linda S. , Seiber James N.
Published: July 2010

This study examines the processes of dilution, degradation, and sorption to plant foliage of organophosphate (OP) pesticides during the summertime in an air corridor originating in the southern Central Valley of California and moving into the nearby Sierra Nevada mountains. Residues of chlorpyrifos, methidathion, and their oxons were examined in air and pine needles at three sites in the southern Sierra to delineate the role these processes play in the atmospheric fate of these residues. At the site closest to the Central Valley, we found relatively high levels of parent OPs and oxons in needle and air samples. At higher elevations needles contained lesser amounts of OP residues and at lower frequency, while air primarily contained the oxon form. With increasing elevation the ratio of thion to oxon form of chlorpyrifos in air decreased from 1.85 to 0.46 indicating that atmospheric oxidation was occuring. Based on the amounts of foliar deposition found, we estimate that during summer months nearly 16 kg of chlorpyrifos and its oxon may enter Sequoia National Park plant foliage. We deduce that for airborne OP insecticides, foliar deposition is a significant summertime fate process, along with atmospheric degradation and dilution.
Transport and Transformation of Urea and Its Derivatives through a Mineral Subsoil
Authors: Swensen Berit , Singh Bal Ram
Published: July 2010

The transport and transformation potential of N compounds derived from urea, applied as a deicing agent during the winter period, have been investigated in a coarse, heterogeneous glacial‐contact deposit in southeast Norway. The hydrolysis of urea to ammonium‐N (NH+4‐N) and subsequent oxidation to nitrate‐N (NO−3‐N) was monitored by extraction of soil water from five depths (from 70 to 220 cm) in a lysimeter trench. Urea transport through a soil profile is normally negligible, although urea is a hydrophilic, uncharged molecule. In this study, urea was rapidly transported to at least 220 cm. The measured urea‐N concentrations varied from 2 to 50 mg L−1 throughout the profile. This transport was explained by minimal hydrolytic activity because of soil temperatures close to 0°C, and by different preferential flow mechanisms being important during the snowmelt period. Urea hydrolysis occurred at all depths. The NH+4‐N formed in this in situ hydrolysis was oxidized to NO−3‐N. The nitrification started immediately and was most rapid at the 70‐ and 105‐cm depth, but was detectable at all depths down to 220 cm 120 d after solute application. Nitrification also occurred during the winter following the urea application. One year after the urea application, about 40% of the applied urea‐N was recovered as NO−3‐N in the unsaturated zone (0–450 cm), and it is estimated that at least 50% of the applied N will reach the groundwater as NO−3‐N.
Shallow Groundwater Denitrification Rate Measurement by Acetylene Block
Authors: Bragan R. J. , Starr J. L. , Parkin T. B.
Published: July 2010

We field tested a short term, in situ method for measuring highly variable shallow groundwater denitrification rates using a methodology developed in an earlier, laboratory phase of this study. A pulse of tracer solution was injected and subsequently sampled within well clusters 50 cm in radius. The injectate contained dissolved acetylene (C2H2) to block denitrification at the nitrous oxide (N2O) stage of reduction. Six well clusters were established at two depths along a riparian area transect through field, grass, and woodland ecotypes. Bromide tracer, C2H2, and accumulated N2O were monitored at sample wells downgradient from each injection well. Adequate C2H2 concentrations (0.43 mM) to block N2O reduction between injection and sample wells were attained in five of the six well clusters tested. Acetylene peak concentrations moved laterally an average of 19% more slowly than the Br peak, N2O peak concentrations an average of 8% after C2H2 peaks. Highest denitrification rates of 2.8 and 3.3 mg N L−1 d−1 were observed near the surface of the water table within the grass buffer and riparian forest. Shallow groundwater denitrification rates in the adjoining field and 2 m deep into the saturated zone at all three ecotypes were <25% of the highest rates. Acetylene block procedures were thus used to determine in situ denitrification rates within a few days time with little disruption of soil structure or associated microbial communities. Portable equipment allows application at remote sites independent of line power and road access.
Iron‐Related Phosphorus in Overfertilized European Soils
Authors: Ruiz J. M. , Delgado A. , Torrent J.
Published: July 2010

Iron‐related P forms directly influence the amount of phosphate released from soils and sediments, particularly when subjected to reduction. In this work, we examined such P forms in 12 overfertilized, widely different European soils by using various single and sequential extraction techniques, including the use of a mild and a strong reductant (ascorbate and dithionite, respectively). Reductant‐soluble P (defined as the amount of P released by the specific action of a strong reductant) ranged from 2 to 63% of the total amount of P extracted by the sequential extraction procedure of Olsen and Sommers. More than 50% of reductant‐soluble P was released by the specific effect of ascorbate in most of the soils studied. The results of the sequential extractions suggest that, on average, about one‐half of the reductant‐soluble P was occluded in Fe oxides. Poorly crystalline and crystalline Fe oxides generally contained similar amounts of occluded P in absolute terms. However, P/Fe mole ratios were higher in poorly crystalline than in crystalline Fe oxides (X̄ = 5.9 and 1.7 × 10−2, respectively). We suggest that fertilizer P may have been occluded in Fe oxides, particularly in the poorly crystalline forms. The contribution of the parent material, pedogenesis, and fertilization to occluded P build‐up is difficult to assess. Though obtained in vitro, our results suggest that reduction of overfertilized soil materials in aquatic environments can release significant amounts of P; these in turn increase saturation of reduction‐resistant P‐adsorbing surfaces and thus help increase the P equilibrium concentration in solution.
Spatial and Temporal Variability of Herbicides in a Claypan Soil Watershed
Authors: Ghidey F. , Alberts E. E. , Lerch R. N.
Published: July 2010

The spatial and temporal variability of herbicides during the growing season were studied on a 35‐ha watershed located in the claypan soil region of north‐central Missouri. Soil samples were collected from the 0‐ to 5‐cm soil depth in 1993, and 0‐ to 5‐, 5‐ to 10‐, and 10‐ to 15‐cm soil depths in 1995 and analyzed for atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) and alachlor (2‐chloro‐N‐(2,6‐diethl‐N‐(methoxymethyl) acetanilide) concentrations. The effects of rainfall, topography, soil pH, cation exchange capacity (CEC), and organic matter (OM) content on the spatial distribution of herbicides were evaluated. There was no spatial dependency between samples taken immediately after herbicide application; however, spatial dependency was observed in the following sampling periods. During the year, <2.5% of atrazine and 2.0% of alachlor applied to the soil was lost in runoff, and the movement of herbicides below the layer of application was also very low throughout the sampling period. Atrazinc and alachlor concentrations in the soil decreased rapidly during the growing season. Concentrations measured 4 and 8 wk after application were <20 and 5% for atrazine, and <10 and 3% for alachlor, respectively, of those measured immediately after application. The study showed that the spatial and temporal variability of herbicide concentration was a function of the interaction between soil pH and the sorptive capacity of the soil (CEC and OM content). These findings are useful for site‐specific crop management to increase the efficiency of herbicide application and also to reduce the loss of excess herbicides to surface runoff.