bluuebunny/crossref_metadata_2025 huggingface dataset:
Major Herbicides in Ground Water: Results from the National Water‐Quality Assessment
Authors: Barbash Jack E. , Thelin Gail P. , Kolpin Dana W. , Gilliom Robert J.
Published: June 2010

To improve understanding of the factors affecting pesticide occurrence in ground water, patterns of detection were examined for selected herbicides, based primarily on results from the National Water‐Quality Assessment (NAWQA) program. The NAWQA data were derived from 2227 sites (wells and springs) sampled in 20 major hydrologic basins across the USA from 1993 to 1995. Results are presented for six high‐use herbicides—atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), cyanazine (2‐[4‐chloro‐6‐ethylamino‐1,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile), simazine (2‐chloro‐4,6‐bis[ethylamino]‐s‐triazine), alachlor (2‐chloro‐N‐[2,6‐diethylphenyl]‐N‐[methoxymethyl]acetamide), acetochlor (2‐chloro‐N‐[ethoxymethyl]‐ N‐[2‐ethyl‐6‐methylphenyl]acetamide), and metolachlor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]acetamide)— as well as for prometon (2,4‐bis[isopropylamino]‐6‐methoxy‐s‐triazine), a nonagricultural herbicide detected frequently during the study. Concentrations were <1 μg L−1 at 98% of the sites with detections, but exceeded drinking‐water criteria (for atrazine) at two sites. In urban areas, frequencies of detection (at or above 0.01 μg L−1) of atrazine, cyanazine, simazine, alachlor, and metolachlor in shallow ground water were positively correlated with their nonagricultural use nationwide (P < 0.05). Among different agricultural areas, frequencies of detection were positively correlated with nearby agricultural use for atrazine, cyanazine, alachlor, and metolachlor, but not simazine. Multivariate analysis demonstrated that for these five herbicides, frequencies of detection beneath agricultural areas were positively correlated with their agricultural use and persistence in aerobic soil. Acetochlor, an agricultural herbicide first registered in 1994 for use in the USA, was detected in shallow ground water by 1995, consistent with previous field‐scale studies indicating that some pesticides may be detected in ground water within 1 yr following application. The NAWQA results agreed closely with those from other multistate studies with similar designs.
Using Rank‐Order Geostatistics for Spatial Interpolation of Highly Skewed Data in a Heavy‐Metal Contaminated Site
Authors: Juang Kai‐Wei , Lee Dar‐Yuan , Ellsworth Timothy R.
Published: June 2010

The spatial distribution of a pollutant in contaminated soils is usually highly skewed. As a result, the sample variogram often differs considerably from its regional counterpart and the geostatistical interpolation is hindered. In this study, rank‐order geostatistics with standardized rank transformation was used for the spatial interpolation of pollutants with a highly skewed distribution in contaminated soils when commonly used nonlinear methods, such as logarithmic and normal‐scored transformations, are not suitable. A real data set of soil Cd concentrations with great variation and high skewness in a contaminated site of Taiwan was used for illustration. The spatial dependence of ranks transformed from Cd concentrations was identified and kriging estimation was readily performed in the standardized‐rank space. The estimated standardized rank was back‐transformed into the concentration space using the middle point model within a standardized‐rank interval of the empirical distribution function (EDF). The spatial distribution of Cd concentrations was then obtained. The probability of Cd concentration being higher than a given cutoff value also can be estimated by using the estimated distribution of standardized ranks. The contour maps of Cd concentrations and the probabilities of Cd concentrations being higher than the cutoff value can be simultaneously used for delineation of hazardous areas of contaminated soils.
Accumulation, Distribution, and Toxicity of Copper in Sediments of Catfish Ponds Receiving Periodic Copper Sulfate Applications
Authors: Han F.X. , Hargreaves John A. , Kingery William L. , Huggett Duane B. , Schlenk Daniel K.
Published: June 2010

Copper sulfate (CuSO4) is applied periodically to commercial channel catfish (Ictalurus punctatus) ponds as an algicide or parasiticide. Current understanding of the chemistry of copper in soil–water systems suggests that copper may accumulate in pond sediments, although the forms and potential bioavailability of copper in catfish pond sediments are not known. This study investigated the accumulation and distribution of copper in the sediment of catfish ponds receiving periodic additions of CuSO4 · 5H2O. All ponds were constructed in Sharkey (very‐fine, smectitic, thermic Chromic Epiaquert) soil. Nine 0.40‐ha ponds received 59 applications of 2.27 kg CuSO4 · 5H2O per application per pond over 3 yr; no CuSO4 · 5H2O applications were made to nine additional ponds. Total Cu concentration in the sediments of CuSO4 · 5H2O‐amended catfish ponds (172.5 mg kg−1) was four to five times higher than that in the sediments of nonamended ponds (36.1 mg kg−1). Copper accumulated in catfish pond sediments at a rate of 41 μg kg−1 dry sediment for each 1 kg ha−1 of CuSO4 · 5H2O applied to ponds. Copper in the sediments of amended ponds was mainly in the organic matter–bound (30.7%), carbonate‐bound (31.8%), and amorphous iron oxide–bound (22.1%) fractions with a considerable fraction (3.4%; 3 to 8 mg kg−1) in soluble and exchangeable fractions. This indicates that Cu accumulates differentially in various fractions, with proportionally greater initial accumulation in potentially bioavailable forms. However, toxicity bioassays with amphipods (Hyallela azteca) and common cattail (Typha latifolia L.) indicated that the effect of exposure to amended or nonamended pond sediments was not different.
Elevated Lead and Zinc Contents in Remote Alpine Soils of the Swiss National Park
Authors: Nowack Bernd , Obrecht Jean‐Marc , Schluep Mathias , Schulin Rainer , Hansmann Werner , Köppel Victor
Published: June 2010

Weathering of bedrock and pedogenic processes can result in elevated heavy metal concentrations in the soil. Small‐scale variations in bedrock composition can therefore cause local variations in the metal content of the soil. Such a case was found in the remote alpine area of the Swiss National Park. Soil profiles were sampled at an altitude of about 2400 m, representing soils developed above different bedrocks. The concentration of lead in the profiles was found to be strongly dependent on the metal content in the bedrock underlying the soil and was strongly enriched in the top 10 cm. The dolomitic bedrock in the study area contains elevated lead concentrations compared with other dolomites. Dissolution of dolomite and accumulation of weathering residues during soil formation resulted in high lead concentrations throughout the soil profile. The enrichment of lead in the topsoil, however, is largely attributed to atmospheric input. The isotopic signature of the lead clearly indicates that it is mainly of natural origin and that atmospheric deposition of anthropogenic lead contributed to about 20 to 40% to the lead concentration in the topsoil on the bedrock with elevated lead concentrations. In the soils on bedrock with normal lead concentrations, the anthropogenic contribution is estimated to be about 75%. Also, zinc was very strongly enriched in the topsoil. This enrichment was closely correlated with the organic matter distribution in the profiles, suggesting that recycling through plant uptake and litter deposition was a dominant process in the long‐term retention of this metal in the soil.
Assessment of the Risk of Phosphorus Loading Due to Resuspended Sediment
Authors: Koski‐Vähälä J. , Hartikainen H.
Published: June 2010

Resuspension is a multiphase phenomenon where suspended solids encounter water layers differing in physico–chemical properties that affect the reactions of phosphorus (P). The role of resuspended sediment as a sink or source of dissolved P was determined in a laboratory study of P desorption–sorption equilibria. Gradual mixing was simulated using decreasing solid concentrations and varying environmental conditions (pH, redox, ionic strength). To describe the P exchange when the particles encounter dissimilar water layers, the extent of P sorption to or desorption from solids was expressed as a function of P concentration in the bath solutions. The equilibrium phosphorus concentration (EPC), at which there is no net P release from or retention to the particles, proved to be a suitable parameter for assessment of P load risk. Under oxic conditions at pH 7, commonly prevailing in lakes, the EPC values ranged from 11 to 27 μg P L−1 The larger the water volume the suspended material was mixed with, the higher the P concentration, allowing desorption to occur. As for chemical factors affecting P mobilization, EPC followed the order: pH 7 < pH 7 anoxic < pH 9. A separate extraction experiment revealed that elevated pH enhanced P mobilization more as the concentration of solids decresed. The results demonstrate that high pH (a common characteristic in eutrophic lakes during summer), when linked with intensive resuspension, may markedly increase the internal P loading risk. As for the risk assessment, the quantification of the internal P loading would be improved by isotherm studies combined with field observations.
Precipitation and River Water Chemistry of the Piracicaba River Basin, Southeast Brazil
Authors: Williams Michael R. , Filoso Solange , Martinelli Luiz A. , Lara Luciene B. , Camargo Plínio B.
Published: June 2010

Annual precipitation and river water volumes and chemistry were measured from 1995 to 1998 in a mesoscale agricultural area of southeast Brazil. Precipitation was mildly acidic and solute concentrations were higher in the west than in the east of the basin. Combustion products from biomass burning, automobile exhaust, and industry typically accumulate in the atmosphere from March until October and are responsible for seasonal differences observed in precipitation chemistry. In river waters, the volume‐weighted mean (VWM) concentrations of major solutes at 10 sites across the basin were generally lower at upriver than at downriver sampling sites for most solutes. Mass balances for major solutes indicate that, as a regional entity, the Piracicaba River basin was a net sink of H+, PO3−4, and NH+4, and a net source of other solutes. The main stem of the Piracicaba River had a general increase in solute concentrations from upriver to downriver sampling sites. In contrast, NO−3 and NH+4 concentrations increased in the mid‐reach sampling sites and decreased due to immobilization or utilization in the mid‐reach reservoir, and there was denitrification immediately downriver of this reservoir. Compared with tributaries of the Chesapeake Bay estuary, the Piracicaba River is affected more by point‐source inputs of raw sewage and industrial wastes than nonpoint agricultural runoff high in N and P. Inputs of N and C are responsible for a degradation of water quality at downriver sampling sites of the Piracicaba River drainage, and water quality could be considerably improved by augmenting sewage treatment.
Herbicide Transport to Surface Waters at Field and Watershed Scales in a Mediterranean Vineyard Area
Authors: Louchart Xavier , Voltz Marc , Andrieux Patrick , Moussa Roger
Published: June 2010

The contamination of soil and runoff water by two herbicides, diuron [N′‐(3,4‐dichlorphenyl)‐N,N‐dimethylurea] and simazine (6‐chloro‐N,N′‐diethyl‐1,3,5‐triazine‐2,4‐diamine), were monitored on two fields, one no‐till and one tilled. Experiments were carried out in a 91.4‐ha watershed in southern France during the 1997 growing season in order to understand the patterns of pesticide transport from field to watershed. The persistence of the herbicides in soil was prolonged due to the climatic conditions. At the field scale, annual herbicide loads were due to overland flow and amounted to 65.6 and 6.3 g ha−1 of diuron for the no‐till and tilled field, respectively, and to 29.6 and 1.83 g ha−1 of simazine. Maximum herbicide concentrations exceeded 580 μg L−1 during the first storm event after application and decreased thereafter but remained for 8 mo above 0.1 μg L−1 At the watershed outlet, estimated annual loads amounted to 4.12 g ha−1 of diuron and 0.56 g ha−1 of simazine. Among them, 96% of the losses in diuron and 83% of those in simazine were caused by the fast transmission through the network of ditches of the overland flow exiting the fields. For diuron, which was sprayed over most of the vineyards, its in‐stream concentrations during storm flow were close to those at the outlet of the fields. The herbicide loads in baseflow were smaller than 0.2 g ha−1 The patterns of the loads at the field and watershed scales suggested that a major part of the herbicides leaving the fields reinfiltrated to the ground water by seepage through the ditches, and was there degraded or adsorbed.
Factors Affecting the Ratio of Cation Exchange Capacity to Clay Content in Lignite Overburden
Authors: Stewart W.M. , Hossner L.R.
Published: June 2010

Unusually high cation exchange capacity (CEC) values relative to clay content are frequently reported for lignite overburden and minesoils. The CEC to percent clay ratio is commonly greater than one and would require that the average charge of the clay fraction be greater than 100 cmolckg−1A comparison of methods for particle‐size distribution suggests that the major reason lignite overburden samples have CEC to percent clay ratios greater than one is incomplete dispersion of aggregates of clay minerals or shale fragments. Preliminary investigations revealed the presence of shale fragments, smectite, and partially weathered mica in the silt fraction. Methods commonly used in soil textural analysis underestimated clay content by approximately 24%. The silt fraction may, therefore, provide a “hidden” source of CEC. Another important factor influencing the CEC to percent clay ratio was the presence of organic materials (lignite) in the samples. Lignite may make a significant contribution to CEC in overburden materials. In a study designed to estimate the pH‐dependent charge of both the mineral and organic fractions, the CEC of overburden organic constituents was determined to be approximately 158 cmolckg−1at pH 8.2. The high CEC to percent clay ratio in lignite overburden and minesoils may be resolved by adjusting methods for clay determination to optimize dispersion and by accounting for CEC due to organic materials. An alternative approach is to use existing methodology and use correction factors to account for incomplete dispersion of clay minerals and the charge contributions of organic materials.
Tracing Nitrate Transport and Environmental Impact from Intensive Swine Farming using Delta Nitrogen‐15
Authors: Karr Jonathan D. , Showers William J. , Gilliam J.Wendell , Andres A.Scott
Published: June 2010

Natural‐abundance δ15N showed that nitrate generated from commercial land application of swine (Sus scrofa domesticus) waste within a North Carolina Coastal Plain catchment was being discharged to surface waters by ground water passing beneath the sprayfields and adjacent riparian buffers. This was significant because intensive swine farms in North Carolina are considered non‐discharge operations, and riparian buffers with minimum widths of 7.6 m (25 ft) are the primary regulatory control on ground water export of nitrate from these operations. This study shows that such buffers are not always adequate to prevent discharge of concentrated nitrate in ground water from commercial swine farms in the Mid‐Atlantic Coastal Plain, and that additional measures are required to ensure non‐discharge conditions. The median δ15N‐total N of liquids in site swine waste lagoons was +15.4 ± 0.2‰ vs. atmospheric nitrogen. The median δ15N‐NO3 values of shallow ground water beneath and adjacent to site sprayfields, a stream draining sprayfields, and waters up to 1.5 km downstream were +15.3 ± 0.2 to +15.4 ± 0.2‰. Seasonal and spatial isotopic variations in lagoons and well waters were greatly homogenized during ground water transport and discharge to streams. Neither denitrification nor losses of ammonia during spraying significantly altered the bulk ground water δ15N signal being delivered to streams. The lagoons were sources of chloride and potassium enrichment, and shallow ground water showed strong correlation between nitrate N, potassium, and chloride. The 15N‐enriched nitrate in ground water beneath swine waste sprayfields can thus be successfully traced during transport and discharge into nearby surface waters.
Immobilization of Cesium‐137 and Uranium in Contaminated Sediments Using Soil Amendments
Authors: Seaman John C. , Meehan T. , Bertsch P.M.
Published: June 2010

Batch and dynamic leaching methods were used to evaluate the effectiveness of hydroxyapatite (HA), illite, and zeolite, alone and in combination, as soil additives for reducing the migration of cesium‐137 (137Cs+) and uranium (U) from contaminated sediments. Amendment treatments ranging from 0 to 50 g kg−1were added to the sediment and equilibrated in 0.001MCaCl2After equilibration, the treatment supernatants were analyzed for137Cs+, U, PO4, and other metals. The residual sediments were then extracted overnight using one of the following: 1.0MNH4Cl, 0.5MCaCl2, or the Toxicity Characteristic Leaching Procedure (TCLP) extractant. Cesium was strongly sorbed to the contaminated sediments, presumably due to interlayer fixation within native illitic clays. In fact,137Cs+was below detection limits in the initial equilibration solutions, the CaCl2extract, and the TCLP solution, regardless of amendment. Extractants selective for interlayer cations (1.0MNH4Cl) were necessary to extract measurable levels of137Cs+Addition of illitic clays further reduced Cs+extractability, even when subjected to the aggressive extractants. Zeolite, however, was ineffective in reducing Cs+mobility when subjected to the aggressive extractants. Hydroxyapatite was less effective than illite at reducing NH+4–extractable Cs+Hydroxyapatite, and mixtures of HA with illite or zeolite, were highly effective in reducing U extractability in both batch and leaching tests. Uranium immobilization by HA was rapid with similar final U concentrations observed for equilibration times ranging from 1 h to 30 d. The current results demonstrate the effectiveness of soil amendments in reducing the mobility of U and Cs+, which makes in‐place immobilization an effective remediation alternative.
In Situ Stabilization of Soil Lead Using Phosphorus
Authors: Hettiarachchi G.M. , Pierzynski G.M. , Ransom M.D.
Published: June 2010

In situ stabilization of Pb‐contaminated soils can be accomplished by adding phosphorus. The standard remediation procedure of soil removal and replacement currently used in residential areas is costly and disruptive. This study was carried out to evaluate the influence of P and other soil amendments on five metal‐contaminated soils and mine wastes. Seven treatments were used: unamended control; 2500 mg of P/kg as triple superphosphate (TSP), phosphate rock (PR), acetic acid followed by TSP, and phosphoric acid (PA); and 5000 mg of P/kg as TSP or PR. A significant reduction in bioavailable Pb, as determined by the physiologically based extraction test (PBET), compared with the control upon addition of P was observed in all materials tested. Increasing the amount of P added from 2500 to 5000 mg/kg also resulted in a significantly greater reduction in bioavailable Pb. Phosphate rock was equally or more effective than TSP or PA in reducing bioavailable Pb in four out of five soils tested. Preacidification produced significantly lower bioavailable Pb compared with the same amount of P from TSP or PR in only one material. Reductions in Pb bioavailability as measured by PBET were evident 3 d after treatment, and it may indicate that the reactions between soil Pb and P occurred in situ or during the PBET. No further reductions were noted over 365 d. X‐ray diffraction data suggested the formation of pyromorphite‐like minerals induced by P additions. This study suggests that P addition reduced bioavailable Pb by PBET and has potential for in situ remediation of Pb‐contaminated soils.
Assessment of Metal Availability in Smelter Soil Using Earthworms and Chemical Extractions
Authors: Conder Jason M. , Lanno Roman P. , Basta Nicholas T.
Published: June 2010

Chemical immobilization is a relatively inexpensive in situ remediation method that reduces soil contaminant solubility, but the ability of this remediation treatment to reduce heavy metal bioavailability and ecotoxicity to soil invertebrates has not been evaluated. Our objectives were to (i) assess the ability of chemical immobilization amendments (municipal sewage sludge biosolids and rock phosphate) to reduce metal bioavailability and toxicity in a toxic metal‐contaminated smelter soil and (ii) evaluate soil extraction methods using Ca(NO3)2 solution or ion‐exchange membranes coated with diethylenetriaminepentaacetic acid (DTPA) as surrogate measures of metal bioavailability and ecotoxicity. We treated a soil contaminated by Zn and Pb milling and smelting operations and an uncontaminated control soil with lime‐stabilized municipal biosolids (LSB), rock phosphate (RP), or anaerobically digested municipal biosolids (SS) and evaluated lethality of the remediated soils to earthworm (Eisenia fetida Savigny). Lime‐stabilized municipal biosolids was the only remediation amendment to successfully immobilize lethal levels of Zn in the smelter soil (14‐d cumulative mortality ≤15%). Calcium nitrate–extractable Zn in the lethal Zn smelter soil–amendment combinations was 11.5 to 18.2 mmol/kg, compared with the nonlethal LSB amended soil (0.62 mmol/kg). The Ca(NO3)2–extractable Zn‐based median lethal concentration (LC50) of 6.33 mmol/kg previously developed in Zn‐spiked artificial soils was applicable in the remediated smelter soils despite a 14‐fold difference in total Zn concentration. Chelating ion‐exchange membrane uptake among the soils was highly variable (mean CV = 39%) compared with the Ca(NO3)2–extraction (mean CV = 1.9%) and not well related to earthworm toxicity.
Factors Controlling Sediment and Phosphorus Export from Two Belgian Agricultural Catchments
Authors: Steegen A. , Govers G. , Takken I. , Nachtergaele J. , Poesen J. , Merckx R.
Published: June 2010

Sediment and total phosphorus (TP) export vary through space and time. This study was conducted to determine the factors controlling sediment and TP export in two agricultural catchments situated in the Belgian Loess Belt. At the outlet of these catchments runoff discharge was continuously measured and suspended sediment samples were taken during rainfall events. Within the catchments vegetation type and cover, soil surface parameters, erosion features, sediment pathways, and rainfall characteristics were monitored. Total P content and sediment characteristics such as clay, organic carbon, and suspended sediment concentration were correlated. Total sediment and TP export differ significantly between the monitored catchments. Much of the difference is due to the occurrence of an extreme event in one catchment and the morphology and spatial organization of land use in the catchments. In one catchment, the direct connection between erosive areas and the catchment outlet by means of a road system contributed to a high sediment delivery ratio (SDR) at the outlet. In the other catchment, the presence of a wide valley in the center of the catchment caused sediment deposition. Vegetation also had an effect on sediment production and deposition. Thus, many factors control sediment and TP export from small agricultural catchments; some of these factors are related to the physical catchment characterisics such as morphology and landscape structure and are (semi)permanent, while others, such as vegetation cover and land use, are time dependent.
Effects of Dissolved Organic Matter from Animal Waste Effluent on Chlorpyrifos Sorption by Soils
Authors: Huang Xinjiang , Lee Linda S.
Published: June 2010

The increased use of animal waste–derived effluents for irrigation could result in the enhanced movement of pesticides through complexation with dissolved organic materials. Batch equilibrium studies were conducted to measure the interaction among soil, chlorpyrifos [O,O‐diethyl O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate], and dissolved organic matter (DOM) from poultry, swine, and cow waste–derived lagoon effluents. All DOM was found to have a strong affinity for chlorpyrifos, resulting in reduced sorption of chlorpyrifos by soil, thus the potential for DOM‐enhanced mobility. Effluent DOM was observed to sorb to soils. Thus, for increasingly higher soil mass to solution volume ratios, the effect of chlorpyrifos association with water‐borne DOM on sorption decreases significantly. For high soil mass to solution volume ratios typical of soil profiles in the landscape, the potential for DOM‐enhanced transport will be greatly attenuated. Dissolved organic matter concentration and the nonpolar nature of DOM in the lagoon effluent decreased with increasing residence time in the cells of the lagoon system, thus reducing the potential for DOM‐enhanced transport.
Anaerobic Degradation of Atrazine and Metolachlor and Metabolite Formation in Wetland Soil and Water Microcosms
Authors: Seybold C.A. , Mersie W. , McNamee C.
Published: June 2010

The half‐lives, degradation rates, and metabolite formation patterns of atrazine (6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine) and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] were determined in an anaerobic wetland soil incubated at 24°C for 112 d. At 0, 7, 14, 28, 42, 56, and 112 d, the soil and water were analyzed for atrazine and metolachlor, and their major metabolites. The soil oxidation–reduction potential reached −200 mV after 14 d. Degradation reaction rates were first‐order for atrazine in anaerobic soil and for metolachlor in the aqueous phase. Zero‐order reaction rates were best fit for atrazine in the aqueous phase and metolachlor in anaerobic soil. In anaerobic soil, the half‐life was 38 d for atrazine and 62 d for metolachlor. In the aqueous phase above the soil, the half‐life was 86 d for atrazine and 40 d for metolachlor. Metabolites detected in the anaerobic soil were hydroxyatrazine and deethylatrazine for atrazine, and relatively small amounts of ethanesulfonic acid and oxanilic acid for metolachlor. Metabolites detected in the aqueous phase above the soil were hydroxyatrazine, deethylatrazine, and deisopropylatrazine for atrazine, and ethanesulfonic acid and oxanilic acid for metolachlor. Concentrations of metabolites in the aqueous phase generally peaked within the first 25 d and then declined. Results indicate that atrazine and metolachlor can degrade under strongly reducing conditions found in wetland soils. Metolachlor metabolites, ethanesulfonic acid, and oxanilic acid are not significantly formed under anaerobic conditions.
Degradation of Soil Fumigants as Affected by Initial Concentration and Temperature
Authors: Ma Q.L. , Gan J. , Papiernik S.K. , Becker J.O. , Yates S.R.
Published: June 2010

Soil fumigation using shank injection creates high fumigant concentration gradients in soil from the injection point to the soil surface. A temperature gradient also exists along the soil profile. We studied the degradation of methyl isothiocyanate (MITC) and 1,3‐dichloropropene (1,3‐D) in an Arlington sandy loam (coarse‐loamy, mixed, thermic Haplic Durixeralf) at four temperatures and four initial concentrations. We then tested the applicability of first‐order, half‐order, and second‐order kinetics, and the Michaelis–Menten model for describing fumigant degradation as affected by temperature and initial concentration. Overall, none of the models adequately described the degradation of MITC and 1,3‐D isomers over the range of the initial concentrations. First‐order and half‐order kinetics adequately described the degradation of MITC and 1,3‐D isomers at each initial concentration, with the correlation coefficients greater than 0.78 (r2 > 0.78). However, the derived rate constant was dependent on the initial concentration. The first‐order rate constants varied between 6 and 10× for MITC for the concentration range of 3 to 140 mg kg−1, and between 1.5 and 4× for 1,3‐D isomers for the concentration range of 0.6 to 60 mg kg−1, depending on temperature. For the same initial concentration range, the variation in the half‐order rate constants was between 1.4 and 1.7× for MITC and between 3.1 and 6.1× for 1,3‐D isomers, depending on temperature. Second‐order kinetics and the Michaelis–Menten model did not satisfactorily describe the degradation at all initial concentrations. The degradation of MITC and 1,3‐D was primarily biodegradation, which was affected by temperature between 20 and 40°C, following the Arrhenius equation (r2 > 0.74).
Seasonal Leaching and Biodegradation of Dicamba in Turfgrass
Authors: Roy J.W. , Hall J.C. , Parkin G.W. , Wagner‐Riddle C. , Clegg B.S.
Published: June 2010

The leaching of surface‐applied herbicides, such as dicamba (2‐methoxy‐3,6‐dichlorobenzoic acid), to ground water is an environmental concern. Seasonal changes in soil temperature and water content, affecting infiltration and biodegradation, may control leaching. The objectives of this study were to (i) investigate the leaching of dicamba applied to turfgrass, (ii) measure the degradation rate of dicamba in soil and thatch in the laboratory under simulated field conditions, and (iii) test the ability of the model EXPRES (containing LEACHM) to simulate the field transport and degradation processes. Four field lysimeters, packed with sandy loam soil and topped with Kentucky bluegrass (Poa pratensis L.) sod, were monitored after receiving three applications (May, September, November) of dicamba. Concentrations of dicamba greater than 1 mg L−1 were detected in soil water. Although drying of the soil during the summer prevented deep transport, greater leaching occurred in late autumn due to increased infiltration. From the batch experiment, the degradation rate for dicamba in thatch was 5.9 to 8.4 times greater than for soil, with a calculated half‐life as low as 5.5 d. Computer modeling indicated that the soil and climatic conditions would influence the effectiveness of greater degradation in thatch for reducing dicamba leaching. In general, EXPRES predictions were similar to observed concentration profiles, though peak dicamba concentrations at the 10‐cm depth tended to be higher than predicted in May and November. Differences between predictions and observations are probably a result of minor inaccuracies in the water‐flow simulation and the model's inability to modify degradation rates with changing climatic conditions.
Oxidation Kinetics of the Combustible Fraction of Construction and Demolition Wastes
Authors: Chang Ni‐Bin , Lin Kuen‐Song , Sun Y.‐P. , Wang H.Paul
Published: June 2010

Proper disposal of construction and demolition wastes (CDW) has received wide attention recently due to significantly large quantities of waste streams collected from razed or retrofitted buildings in many metropolitan regions. Burning the combustible fractions of CDW (CCDW) and possibly recovering part of the heat content for economic uses could be valuable for energy conservation. This paper explores the oxidation kinetics of CCDW associated with its ash characterization. Kinetic parameters for the oxidation of CCDW were numerically calculated using thermal gravimetric analysis (TGA) and the resultant rate equations were therefore developed for illustrating the oxidation processes of CCDW simultaneously. Based on three designated heating rates, each of the oxidation processes can be featured distinctively with five different stages according to the rate of weight change at the temperature between 300 K and 923 K. In addition, Fourier transform infrared (FTIR) spectroscopy was employed, associated with a lab‐scale fixed‐bed incinerator for monitoring the composition of flue gas. Carbon dioxide (CO2) was found as a major component in the flue gas. The fuel analysis also included an ash composition analysis via the use of X‐ray powder diffraction (XRD), atomic absorption (AA) spectroscopy, inductively coupled plasma–atomic emission spectroscopy (ICP–AES), and scanning electron microscopy–energy dispersive spectroscopy (SEM–EDX). The ash streams were identified as nonhazardous materials based on the toxicity characteristic leaching procedure (TCLP). Overall, the scientific findings gained in this study will be helpful for supporting a sound engineering design of real‐world CCDW incineration systems.
The Influence of Vegetation on Sedimentation and Resuspension of Soil Particles in Small Constructed Wetlands
Authors: Braskerud B.C.
Published: June 2010

When initiatives to mitigate soil erosion are insufficient or fail, constructed surface flow wetlands (CWs) could be a final buffer to reduce pollution before reaching recipients. The objective of this study was to determine the influence of CW vegetation on the retention of soil particles from arable land. Retention was measured with water flow‐proportional sampling systems in the inlet and outlet, sedimentation traps, and sedimentation plates in four small CWs over a period of 5 yr. The surface area of the CWs was 265 to 900 m2, and the average hydraulic loads were 1.2 to 3.4 m d−1 Watershed areas were 0.5 to 1.5 km2 Annual soil particle retention was 30 to 80% or 14 to 121 kg m−2 Results show that macrophytes stimulate sediment retention by mitigating resuspension of CW sediment. Five years after construction, resuspension had decreased approximately 40% and was negligible. As vegetation cover increases, the influence of macrophytes on soil particle retention reaches a level where other factors, such as hydraulic load and sediment load, were more important. Macrophytes increased the hydraulic efficiency by reducing short‐circuit or preferential flow. However, vegetation did not have any influence on the clay concentration in the sediment. Hence, a possible stimulation of particle flocculation was not detected. Vegetation makes it possible to use the positive effect of a short particle settling distance in shallow ponds by hindering resuspension.
Phosphorus Sorption Characteristics of Estuarine Sediments under Different Redox Conditions
Authors: Pant H.K. , Reddy K.R.
Published: June 2010

Phosphorus (P) plays a major role in eutrophication of aquatic systems. Estuarine sediments could function as sources or sinks for P to the overlying water column depending upon their physico–chemical characteristics. Understanding of P sorption phenomena in estuarine sediments is important in regulating the P availability in estuaries. Phosphorus sorption characteristics of sediments from the Indian River Lagoon, Florida, USA, were determined to examine the role of selected physico–chemical properties of the sediments on soluble reactive P status in estuary water. Mean equilibrium P concentrations (EPCo) of 0.75 mg L−1 and mean P sorption maxima (Smax) of 32.2 mg kg−1 were obtained under anaerobic conditions, compared with EPCo of 0.05 mg L−1 and Smax of 132.7 mg kg−1 under aerobic conditions. The higher EPCo values under anaerobic conditions and the greater Smax values under aerobic conditions were associated with amorphous and poorly crystalline iron. These results suggest that sediments enriched with amorphous and poorly crystalline forms of iron act as an excellent reservoir for P by adsorbing excessive P in aerobic sediment zones and releasing it upon burial under anaerobic conditions. This study also indicates that P compounds in sediments independently maintain equilibrium with P in solutions. Thus, heterogeneous systems like soil and sediment simply behave as a mixture of homogeneous surfaces as far as their P sorption characteristics are concerned, and hence can be successfully described by the Langmuir and Freundlich models.
Screening for Organotin Compounds in European Landfill Leachates
Authors: Mersiowsky I. , Brandsch R. , Ejlertsson J.
Published: June 2010

As industrial chemicals, organotin compounds are predominantly applied as polyvinyl chloride (PVC) stabilizers and biocides. They are widely encountered in environmental samples and may be introduced into landfills by disposal of municipal solid waste or sewage sludge. In the present study, leachate samples were obtained from several sanitary landfill sites in Sweden, Italy, and Germany. These samples were analyzed by means of a highly sensitive and species‐selective method for methyltin, butyltin, and octyltin species. In total, twelve samples from eight different landfill sites at various ages were investigated. The findings of all target compounds range between less than the limit of detection at 0.1 μg/L and, at maximum, 4 μg/L. Only octyltin compounds can be attributed to PVC products with any certainty, whereas for methyltin and butyltin compounds alternative and less distinct sources exist. Organotin compounds are subject to microbial transformation, such as dealkylation and methylation processes. Consequently, caution should be exercised when attributing findings to potential sources and deriving any predicted environmental concentrations.
Degradation of Biomacromolecules during High‐Rate Composting of Wheat Straw–Amended Feces
Authors: Veeken A. H. M. , Adani F. , Nierop K. G. J. , de Jager P. A. , Hamelers H. V. M.
Published: June 2010

Pig (Sus scrofa) feces, separately collected and amended with wheat straw, was composted in a tunnel reactor connected with a cooler. The composting process was monitored for 4 wk and the degradation of organic matter was studied by two chemical extraction methods, 13C cross polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and pyrolysis gas chromatography–mass spectrometry (GC–MS). Wet‐chemical extraction methods were not adequate to study the degradation of specific organic compounds as the extraction reagents did not give selective separation of hemicellulose, cellulose, proteins, and lignins. A new method was proposed to calculate the contribution of four biomacromolecules (aliphatics, proteins, polysaccharides, and lignin) from the 13C CPMAS NMR spectrum. Pyrolysis GC–MS allowed identification of the composition of the biomacromolecules. The biomacromolecules showed different rates of degradation during composting. High initial degradation rates of aliphatics, hemicellulose, and proteins were observed, where aliphatics were completely degraded and hemicellulose and proteins were partly recalcitrant during the four weeks of composting. The degradation rate of cellulose was much lower and degradation was not completed within the four weeks of composting. Lignin was not degraded during the thermophilic stage of composting but started to degrade slowly during the mesophilic stage. A combination of 13C CPMAS NMR and pyrolysis GC–MS gave good qualitative and semiquantitative assessments of the degradation of biomacromolecules during composting.
Nutrient Attenuation by a Riparian Wetland during Natural and Artificial Runoff Events
Authors: Casey Ryan E. , Klaine Stephen J.
Published: June 2010

Due to chronic nutrient enrichment of surface water, wetlands adjacent to land managed with fertilizer have been studied to determine their role in nutrient dynamics. We sampled golf course runoff and determined the loads of NO−3 and PO3−4 transported during storms and the attenuation of those loads when runoff passed through a riparian wetland. All sampled storm events contained NO−3 (2 to 1470 g NO3–N per event) and PO3−4 (1 to 4156 g PO4–P per event). Extensive nutrient attenuation occurred when water passed through the riparian wetland. In 11 events, NO−3 and PO3−4 attenuation averaged 80 and 74%, respectively. In subsequent experiments, we created a stream of water flowing into the wetland and amended it with NO−3, PO3−4 and Br−, creating an artificial runoff event. The experiments were conducted using conditions similar to those of natural runoff events. We observed rapid and complete attenuation of PO3−4 immediately after runoff water infiltrated into the wetland subsurface. No PO3−4 was observed in discharge from the wetland. Nitrate attenuation occurred following a lag phase of several hours that was probably due to reactivation of denitrifying enzymes. Nitrate attenuation was initially less than 60% but increased to 100% in all experiments. We observed extensive dilution of runoff water in the wetland subsurface indicating mixing with pre‐event ground water in the wetland. The results indicated that intermittent inputs of NO−3 and PO3−4 could be successfully attenuated in the wetland on the time scale of natural storm events.
Phosphorus Loading in the Frome Catchment, UK: Seasonal Refinement of the Coefficient Modeling Approach
Authors: Hanrahan Grady , Gledhill Martha , House William A. , Worsfold Paul J.
Published: June 2010

This paper describes the results of an export coefficient modeling approach to predict total phosphorus (TP) loading in the Frome catchment, Dorset, UK from point and diffuse sources on a seasonal (monthly) basis in 1998 and on an annual basis for 1990–1998. The model predicted an annual TP load of 25605 kg yr−1, compared with an observed (measured) value of 23400 kg yr−1 Monthly loads calculated using the export coefficient model agreed well with monthly observed values except in months of variable discharge, when observed values were low, probably due to infrequent, and therefore unrepresentative, sampling. Comparison between filterable reactive phosphorus (FRP) and TP concentrations observed in the period 1990–1997 showed that trends in FRP could be estimated from trends in TP. A sensitivity analysis (varying individual export coefficients by ±10%) showed that sewage treatment works (STWs) (3.5%), tilled land (2.7%), meadow–verge–seminatural (1.0%), and mown and grazed turf (0.6%) had the most significant effect (percent difference from base contribution) on model prediction. The model was also used to estimate the effect of phosphorus stripping at STWs in order to comply with a pending change in the European Union wastewater directive. Theoretical reduction of TP from the largest STW in the catchment gave a predicted reduction in TP loading of 2174 kg yr−1 This illustrates the value of this seasonal export coefficient model as a practical management tool.
Chloride Persistence in a Deiced Access Road Drainage System
Authors: Ostendorf David W. , Peeling David C. , Mitchell Travis J. , Pollock Samuel J.
Published: June 2010

Three years of field data, classical linear reservoir theory, and a new dissolution model confirm the hypothesis that residual chloride from highway deicing applications dissolves into precipitation throughout the year. The measured input includes 52 storm hyetographs and logs of salt and premix applications on an access road with a closed drainage system subject to runoff, interflow, and baseflow. The output data feature discharge and conductivity in an outlet weir measured continuously from February 1998 to May 2000. Individual storm hydrographs and pollutographs yield calibrated first flush dissolved chloride concentrations and residual solid chloride loads that persist at appreciable levels over the entire period of record. The storm calibrations imply a source strength ω of 2.01 × 10−6 s−1 that accurately models chloride dissolution kinetics through three salt seasons on the access road. This ω rests on physically plausible values for the depression storage depth ζ (3 mm) and porosity n (0.40) that store the residual chloride.
Using Phosphorus Concentration in the Soil Solution to Predict Phosphorus Desorption to Water
Authors: Torrent José , Delgado Antonio
Published: June 2010

The growing concerns about water eutrophication have made it urgent to restrict losses of phosphorus (P) from agricultural soils and to develop methods for predicting such losses. In this work, we used the paradigm of P sorption–desorption curves to confirm the hypothesis that the amount of dissolved reactive phosphorus (DRP) released to a dilute electrolyte tends to be proportional to the concentration of DRP in the soil solution raised to a power that decreases with increasing solution to soil ratio (W). The hypothesis was tested for a group of 12 widely ranging European agricultural soils fertilized with P in excess of crop needs. Phosphorus desorption was studied under near‐static and turbulent conditions in laboratory experiments. The concentration of DRP in the 1:1 soil to water extract (P1:1) was used as a proxy for the DRP concentration in the soil solution. The amount of desorbed P was found to be correlated with P1:1 raised to a power that decreased from 0.7 to 0.9 at W = 100 to 0.2 to 0.4 at W = 10000. Correlation was not improved by introducing additional variables related to P sorption–desorption properties. Olsen P was found to be of lower predictive value than P1:1 Also, the index of degree of soil saturation with phosphorus (DSSP) based on oxalate extraction failed to predict P desorption. The fact that P1:1 seemingly predicts P desorption accurately for a wide range of soils makes it potentially useful in areas of high soil diversity.
Atmospheric Methyl Tertiary Butyl Ether (MTBE) at a Rural Mountain Site in California
Authors: Schade Gunnar W. , Dreyfus Gabrielle B. , Goldstein Allen H.
Published: June 2010

Methyl tertiary butyl ether (MTBE) was measured in air samples collected at hourly intervals near Blodgett Forest Research Station on the western slope of the Sierra Nevada, California, in July 1997, October 1998, and June through September 1999. Mixing ratios ranged from below the detection limit (< approximately 0.01 ppbv) to 0.5 ppbv, but were generally less than 0.3 ppbv. At these mixing ratios partitioning of MTBE into surface waters would lead to MTBE concentrations of less than 0.2 μg L−1 As expected, MTBE mixing ratios were highly correlated with other anthropogenically emitted hydrocarbons. Based on the observed diurnal cycle of MTBE and its ratio to 2‐methyl‐butane (isopentane), we estimated the average regional daytime oxidant concentration to be (9 to 13) × 106 OH radicals per cubic centimeter, consistent with our earlier estimates for this region. Furthermore, MTBE ratios to toluene, another ubiquitous anthropogenic hydrocarbon, were generally consistent with regional transport and dilution, as well as atmospheric oxidation. Exceptions, pertaining to MTBE mixing ratios below or close to the detection limit, were associated with the influence of marine air masses that did not experience anthropogenic hydrocarbon input from California. With all these constraints in place, evidence for an additional atmospheric loss process, such as nonreversible deposition of MTBE, could not be established, and we conclude that any deposition is slow compared with removal from the atmosphere by the OH radical.