bluuebunny/crossref_metadata_2025 huggingface dataset:
Pesticide Risk Reduction on Crops in the Province of Ontario
Authors: Gallivan G.J. , Surgeoner G.A. , Kovach J.
Published: June 2010

We analyzed the changes in pesticide use and risk in the Province of Ontario, Canada, from 1973 to 1998 to monitor the success of Food Systems 2002, a program to reduce pesticide use by 50%. Pesticide risk was calculated by multiplying the amount of pesticide used (kilograms of active ingredient) by the Environmental Impact Quotient (EIQ), a score for the potential risk of pesticides to farmworkers, consumers, and the environment. Pesticide use increased by 46% from 1973 to 1983. From 1983, the baseline year for Food Systems 2002, to 1998, pesticide use decreased by 38.5% and risk declined 39.5%. The reductions in pesticide use and risk were primarily on corn (Zea mays L.) and tobacco (Nicotiana tabacum L.), the crops with the highest pesticide use in 1983. Total pesticide use on soybean [Glycine max (L.) Merr.] did not change, but the mean application rate (kg ha−1) decreased by 57%. Corn and soybean account for 65% of pesticide use, but have a relatively low pesticide use and risk per hectare and per tonne of production. Total pesticide use on tobacco, fruits, and vegetables was lower than on corn or soybean, but the pesticide use and risk per hectare were much higher. Small reductions in pesticide use on corn and soybean may allow a 50% reduction in pesticide use, but greater reductions in risk can be achieved by reducing the use of “high risk” pesticides on fruit and vegetables.
Spray Deposition of Two Insecticides into Surface Waters in a South African Orchard Area
Authors: Schulz Ralf , Peall Sue K.C. , Dabrowski James M. , Reinecke Adriaan J.
Published: June 2010

Drift from pesticide spray application can result in contamination of nontarget environments such as surface waters. Azinphos‐methyl (AZI) and endosulfan (END) deposition in containers of water was studied in fruit orchards in the Western Cape, South Africa. Additionally, attention was given to the contamination in farm streams, as well as to the resulting contamination of the subsequent main channel (Lourens River) approx. 2.5 km downstream of the tributary stream inlets. Spray deposit decreased with increasing distance downwind and ranged from 4.7 mg m−2within the target area to 0.2 mg m−2at 15 m downwind (AZI). Measured in‐stream concentrations of both pesticides compared well with theoretical values calculated from deposition data for the respective distances. Furthermore, they were in the range of values predicted by an exposure assessment based on 95th‐percentile values for basic drift deposition (German Federal Biological Research Centre for Agriculture and Forestry [BBA] and USEPA). Pesticide deposition in the tributaries was followed by a measurable increase of contamination in the Lourens River. Mortality of midges (Chironomusspp.) exposed for 24 h to samples obtained from the AZI trials decreased with decreasing concentrations (estimated LC50from field samples = 10 μg L−1AZI; lethal distance: LD50= 13 m). Mortality in the tributary samples averaged 11% (0.5–1.7 μg L−1AZI), while no mortality was discernible in the Lourens River samples (0.041 μg L−1). The sublethal endpoint failure to form tubes from the glass beads provided was significantly increased at all sites in comparison with the control (analysis of variance [ANOVA], Fisher's protected least significant difference [PLSD],p< 0.01).
EPIC Tile Flow and Nitrate Loss Predictions for Three Minnesota Cropping Systems
Authors: Chung S.W. , Gassman P.W. , Huggins D.R. , Randall G.W.
Published: June 2010

Subsurface tile drains are a key source of nitrate N (NO3–N) losses to streams in parts of the north central USA. In this study, the Erosion Productivity Impact Calculator (EPIC) model was evaluated by comparing measured vs. predicted tile flow, tile NO3–N loss, soil profile residual NO3–N, crop N uptake, and yield, using 4 yr of data collected at a site near Lamberton, MN, for three crop rotations: continuous corn (Zea mays L.) or CC, corn–soybean [Glycine max (L.) Merr.] or CS, and continuous alfalfa (Medicago sativa L.) or CA. Initially, EPIC was run using standard Soil Conservation Service (SCS) runoff curve numbers (CN2) for CC and CS; monthly variations were accurately tracked for tile flow (r2 = 0.86 and 0.90) and NO3–N loss (r2 = 0.69 and 0.52). However, average annual CC and CS tile flows were underpredicted by −32 and −34%, and corresponding annual NO3–N losses were underpredicted by −11 and −52%. Predicted average annual tile flows and NO3–N losses generally improved following calibration of the CN2; tile flow underpredictions were −9 and −12%, whereas NO3–N losses were 0.6 and −54%. Adjusting a N parameter further improved predicted CS NO3–N losses. Predicted monthly tile flows and NO3–N losses for the CA simulation compared poorly with observed values (r2 values of 0.27 and 0.19); the annual drainage volumes and N losses were of similar magnitude to those measured. Overall, EPIC replicated the relative impacts of the three cropping systems on N fate.
Effect of Dissolved Organic Matter from Sludge and Sludge Compost on Soil Copper Sorption
Authors: Zhou L.X. , Wong J.W.C.
Published: June 2010

Interaction of Cu with dissolved organic matter (DOM) is an important physicochemical process affecting Cu mobility in soils. The aim of this study was to investigate the effects of DOM from anaerobically digested dewatered sludge and sludge compost on the sorption of Cu on an acidic sandy loam and a calcareous clay loam. In the presence of DOM, Cu sorption capacity decreased markedly for both soils, especially for the calcareous soil. The Cu sorption isotherms could be well described by the Freundlich equation (r2 = 0.99), and the binding intensity parameter of soils in the presence of sludge DOM was lower than compost DOM. An increase in DOM concentration significantly reduced the sorption of Cu by both soils. Within the Cu and DOM concentration range studied, the decrease in Cu sorption caused by sludge DOM was consistently greater than that of compost DOM. This might be attributed to the greater amount of hydrophobic fraction of DOM in the compost. Moreover, the reduction of Cu sorption caused by DOM was more obvious in the soil with higher pH. In addition, the sorption of Cu increased with an increase in pH for both soils without the addition of DOM, while Cu sorption in the presence of DOM was unexpectedly decreased with an increase in pH at a pH >6.8. This implied that DOM produced by sludge or other C‐enriched organic wastes heavily applied on calcareous soils might facilitate the leaching loss of Cu because of the formation of soluble DOM–metal complexes.
Adsorption of Cadmium on Biosolids‐Amended Soils
Authors: Li Zhenbin , Ryan James A. , Chen Jiann‐Long , Al‐Abed Souhail R.
Published: June 2010

Debate exists over the biosolid phase (organic or inorganic) responsible for the reduction in phytoavailable Cd in soils amended with biosolids as compared with soils amended with inorganic salts. To test the importance of these two phases, adsorption isotherms were developed for soil samples (nine biosolids‐amended soils and their five companion controls) and two biosolids samples from five experimental sites with documented histories of biosolids application. Subsamples were treated with 0.7 M NaClO to remove organic carbon. Cadmium nitrate was added to both moist soil samples and their soil inorganic fractions (SIF) in a 0.01 M Ca(NO3)2 solution at three pH levels (6.5, 5.5, and 4.5), and equilibrated at 22 ± 1°C for at least 48 h. Isotherms of Cd adsorption for biosolids‐amended soil were intermediate to the control soil and biosolids. Decreasing pH did not remove the difference between these isotherms, although adsorption of Cd decreased with decreasing pH level. Organic matter removal reduced Cd adsorption on all soils but had little influence on the observed difference between biosolids‐amended and control soils. Thus, increased adsorption associated with biosolids application was not limited to the organic matter addition from biosolids; rather, the biosolids application also altered the adsorptive properties of the SIF. The greater affinity of the inorganic fraction of biosolids‐amended soils to adsorb Cd suggests that the increased retention of Cd on biosolids‐amended soils is independent of the added organic matter and of a persistent nature.
Laboratory Degradation Studies of Bentazone, Dichlorprop, MCPA, and Propiconazole in Norwegian Soils
Authors: Thorstensen Christian W. , Lode Olav
Published: June 2010

Laboratory degradation studies were performed in Norwegian soils using two commercial formulations (Tilt and Triagran‐P) containing either propiconazole alone or a combination of bentazone, dichlorprop, and MCPA. These soils included a fine sandy loam from Hole and a loam from Kroer, both of which are representative of Norwegian agricultural soils. The third soil was a highly decomposed organic material from the Froland forest. A fourth soil from the Skuterud watershed was used only for propiconazole degradation. After 84 d, less than 0.1% of the initial MCPA concentration remained in all three selected soils. For dichlorprop, the same results were found for the fine sandy loam and the organic‐rich soil, but in the loam, 26% of the initial concentration remained. After 84 d, less than 0.1% of the initial concentration of bentazone remained in the organic‐rich soil, but in the loam and the fine sandy loam 52 and 69% remained, respectively. Propiconazole was shown to be different from the other pesticides by its persistence. Amounts of initial concentration remaining varied from 40, 70, and 82% in the reference soils after 84 d for the organic‐rich soil, fine sandy loam, and loam, respectively. The organic‐rich soil showed the highest capacity to decompose all four pesticides. The results from the agricultural soils and the Skuterud watershed showed that the persistence of propiconazole was high. Pesticide degradation was approximated to first‐order kinetics. Slow rates of degradation, where more than 50% of the pesticide remained in the soil after the 84‐d duration of the experiment, did not fit well with first‐order kinetics.
Application of Calorimetry to Microbial Biodegradation Studies of Agrochemicals in Oxisols
Authors: Critter Silvana A.M. , Airoldi Claudio
Published: June 2010

Calorimetry was used to monitor the inhibitory effect caused by the bipyridynium diquaternary salts paraquat, diquat, and phosphamidon on microbial activity in a Red Latosol soil (Oxisol). The thermal effect was recorded on samples composed of 1.50 g of soil, 6.0 mg of glucose, 6.0 mg of ammonium sulfate, and different masses of an inhibitor ranging from zero to 8.00 mg, under a controlled moisture content of 35%. Thermal effects of each pollutant on the degradation curves of glucose in the soil were compared. Increasing amounts of the inhibitor caused a decrease in the thermal effect from −2234 to −1987 kJ mol−1for paraquat, −1670 to −1306 kJ mol−1for diquat, and −2239 to −589 kJ mol−1for phosphamidon. The last xenobiotic agent caused a significant inhibitory effect on the microbial activity of the soil. The results of relative efficiency, η = ΔH/ΔH′, referring to the enthalpic value with (ΔH) and without (ΔH′) agrochemical in the soil, exhibited a significant correlation. From this correlation obtained for the ranges 2.00 to 8.00, 1.30 to 8.00, and 1.20 to 5.80 mg of the agrochemicals paraquat, diquat, and phosphamidon, respectively, the following η values were calculated: 0.993 to 0.894, 0.668 to 0.522, and 0.896 to 0.236, respectively, during the degradation of glucose in the soil. The largest relative efficiency for paraquat implies that this agrochemical can be metabolized by microbial activity.
Phenanthrene Degradation in Soils Co‐Inoculated with Phenanthrene‐Degrading and Biosurfactant‐Producing Bacteria
Authors: Dean Stacy M. , Jin Yan , Cha Daniel K. , Wilson Sviatlana V. , Radosevich Mark
Published: June 2010

Contaminant sorption within the soil matrix frequently limits biodegradation. However, contaminant bioavailability can be species‐specific. This study investigated bioavailability of phenanthrene (PHE) to two PHE‐degrading bacteria (Pseudomonas strain R and isolate P5‐2) in the presence of rhamnolipid biosurfactant and/or a biosurfactant‐producing bacterium, Pseudomonas aeruginosa ATCC 9027. Pseudomonas strain R mineralized more soil‐sorbed PHE than strain P5‐2, but in aqueous cultures the rate and extent of PHE mineralization by P5‐2 exceeded that by P strain R. In Fallsington sandy loam (fine‐loamy, mixed, active, mesic Typic Endoaquult) (high PHE‐sorption capacity) the addition of rhamnolipid increased PHE mineralization by P strain R. Phenanthrene mineralization in soils inoculated with P5‐2 was minimal and no enhancement in PHE degradation was observed when biosurfactant was added. Co‐inoculation of Fallsington sandy loam with the biosurfactant producer did not affect PHE mineralization by isolate P5‐2, but significantly enhanced PHE mineralization by P strain R. The enhancement of PHE mineralization could not be explained by P. aeruginosa–mediated PHE degradation. The addition of rhamnolipid at concentrations above the critical micelle concentration (CMC) resulted in enhanced PHE release from test soils. These results suggest that the PHE‐degrading strains were able to access different pools of PHE and that the biosurfactant‐enhanced release of PHE from soils did not result in enhanced biodegradation. The results also demonstrated that bacteria with the catabolic potential to degrade sorbed hydrophobic contaminants could interact commensally with surfactant‐producing strains by an unknown mechanism to hasten the biodegradation of aromatic hydrocarbons. Thus, understanding interactions among microbes may provide opportunities to further enhance biodegradation of soil‐bound organic contaminants.
Analysis of Irrigation Systems Using Sustainability‐Related Criteria
Authors: Manoliadis Odysseus G.
Published: June 2010

Sustainable agricultural development as a desired goal in irrigation management is a result of recent public awareness of the scarcity of water for food production. In order to incorporate sustainability‐related criteria in the analysis of irrigation systems, the present study aims at introducing environmental indices that represent irrigation water conservation and satisfactory production and income for farmers under stress conditions. An experiment was conducted in Chania, Greece, during the irrigation periods of 1989 and 1990. The irrigation water delivered to 40 experimental plots and the relevant soil moisture content at the root zone were recorded. The data, collected in real time, were used for the calculation of the corresponding environmental indices. The variation of indices in time and space was high, and demonstrated that up to 13% of water was delivered to crops, 82% was yield loss, and 84% was economic return. The study indicated that environmental indices could be easily computed by means of routinely collected data, and could also be incorporated into decision‐making approaches, such as compromise programming, in order to develop policies for irrigation water allocation.
Nitrate and Chloride Loading to Groundwater from an Irrigated North‐Central U.S. Sand‐Plain Vegetable Field
Authors: Stites W. , Kraft G.J.
Published: June 2010

Groundwater pollution and associated effects on drinking water have increased with the expansion of irrigated agriculture in north‐central U.S. sand plains. Controlling this pollution requires an ability to measure and predict pollutant loading by specific agricultural systems. We measured NO3 and Cl loading to groundwater beneath a Wisconsin central sand plain irrigated vegetable field using both a budget method and a new monitoring‐based method. By relying on frequent monitoring of shallow groundwater, the new method overcomes some limitations of other methods. Monitoring‐based and budget methods agreed well, and indicated that loading to groundwater was 165 kg ha−1 NO3–N and 111 kg ha−1 Cl for sweet corn (Zea mays L.) in 1992, and 228 kg ha−1 NO3–N and 366 kg ha−1 Cl for potato (Solanum tuberosum L.) in 1993. Nitrate N loading was 56 to 60% of available N, or 66 to 70% of fertilizer N. Sweet corn NO3 loading was about typical for this region, but potato NO3 loading was probably 50% greater than typical because heavy rains provoked extra fertilizer application. Our results imply that typical NO3–N loading would be 119 kg ha−1 for sweet corn and 203 kg ha−1 for potato, even with strict adherence to University Extension fertilizer recommendations. To keep average groundwater NO3–N within the 10 mg L−1 U.S. drinking water standard, each irrigated vegetable field would need to be offset by five to eight times as much land supplying NO3–free groundwater recharge.
Phosphorus Runoff from Two Water Sources on a Calcareous Soil
Authors: Aase J.K. , Bjorneberg D.L. , Westermann D.T.
Published: June 2010

Phosphorus (P) in irrigation runoff may enrich offsite water bodies and streams and be influenced by irrigation water quality and antecedent soil surface conditions. Runoff, soil loss, and P fractions in runoff using reverse osmosis (RO) water or mixed RO and well water (RO/Tap) were studied in a laboratory sprinkler study to evaluate water source effects on P transport. A top‐ or subsoil Portneuf silt loam (coarse‐silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid), either amended or not amended with manure and/or with cheese whey, with Olsen P from 20 to 141 mg kg−1and lime from 108 to 243 g kg−1, was placed in 1.5 × 1.2 × 0.2‐m‐deep containers with 2.4% slope and irrigated three times from a 3‐m height for 15 min, applying 20 mm of water. The first irrigation was on a dry loose surface, the second on a wet surface, and the third on a dry crusted surface. Surface (ca. 2 cm) soil samples, prior to the first irrigation, were analyzed for Olsen P, water‐soluble P (Pws), and iron‐oxide impregnated paper–extractable P (FeO‐P) analyses. Following each irrigation we determined runoff, sediment, dissolved reactive phosphorus (DRP) in a 0.45‐μm filtered sample, and FeO‐P and total P in unfiltered samples. Soil surface conditions had no effect on P runoff relationships. Water source had no significant effect on the relationship between DRP or FeO‐P runoff and soil test P, except for DRP in RO runoff versus water‐soluble soil P (r2= 0.90). Total P in RO runoff versus soil P were not related; but weakly correlated for RO/Tap (r2< 0.50). Water source and soil surface conditions had little or no effect on P runoff from this calcareous soil.
Inverse Analyses of Transport of Chlorinated Hydrocarbons Subject to Sequential Transformation Reactions
Authors: Casey Francis X.M. , Šimůnek Jiří
Published: June 2010

Chemical and biological transformations can significantly affect contaminant transport in the subsurface. To better understand such transformation reactions, an equilibrium–nonequilibrium sorption transport model, HYDRUS‐1D, was modified by including inverse solutions for multiple breakthrough curves resulting from the transport of solutes undergoing sequential transformations. The inverse solutions were applied to miscible‐displacement experiments involving dissolved concentrations of trichloroethylene (TCE) undergoing reduction and/or transformations in the presence of zero‐valent metal porous media (i.e., iron or copper‐coated iron filings) to produce ethylene. The inverse model solutions provided a reasonable description of the transport and transformation processes. Simultaneous fitting of multiple breakthrough curves of TCE and ethylene placed additional constraints on the inverse solution and improved the reliability of parameter estimates. Confidence intervals of optimized parameters were reduced significantly in comparison with those obtained by fitting TCE breakthrough curves independently. Further evidence for accurate parameter estimates was given when the parameter values agreed with previously reported values from independent batch and degradation experiments. Optimized values of the normalized degradation rates for the equilibrium (1.4 × 10−4 to 7.2 × 10−5 L h−1 m−2) and nonequilibrium (1.2 × 10−4 to 5.5 × 10−5 L h−1 m−2) models compared well with values (0.03 to 6.5 × 10−5 L h−1 m−2) obtained from previous studies. The estimated TCE–iron sorption coefficients (0.52 to 2.85 L kg−1) were also consistent with a previously reported value (1.47 L kg−1).
Spatio–Temporal Patterns of Soil Phosphorus Enrichment in Everglades Water Conservation Area 2A
Authors: DeBusk W.F. , Newman S. , Reddy K.R.
Published: June 2010

The Florida Everglades have undergone significant ecological change resulting from anthropogenic manipulation of historical regimes of hydrology, nutrient loading, and fire. Water Conservation Area 2A (WCA‐2A) in the northern Everglades has been a focal point for the study of ecological effects of nutrient loading, especially phosphorus (P), from the nearby Everglades Agricultural Area (EAA). The overall objective of our study was to evaluate recent (1990 to 1998) changes in the spatial extent and patterns of soil P enrichment in Everglades WCA‐2A. Surface soil was sampled to a depth of 10 cm at 62 sites within WCA‐2A during 1998 for analysis of total phosphorus (TP) content. Geostatistical methods were used to create an interpolated grid of soil TP values across WCA‐2A. Comparison of the results of this study with a similar study performed in 1990 showed that the extent of soil P enrichment in surface soil and sediments increased between 1990 and 1998, as evidenced by increased coverage of highly P‐enriched soil near the primary surface inflows and a general increase in the concentration of soil TP in the interior regions of WCA‐2A. Approximately 73% (31777 ha) of the total land area of WCA‐2A was considered P‐enriched (soil total P > 500 mg kg−1) in 1998, compared with 48% of the land area (20829 ha) in 1990, an average increase of 1327 ha yr−1Study results indicate that the soil P enrichment “front” has advanced further into the relatively unimpacted interior of WCA‐2A during the past several years.
A Modified Risk Assessment to Establish Molybdenum Standards for Land Application of Biosolids
Authors: O'Connor George A. , Brobst Robert B. , Chaney Rufus L. , Kincaid Ron L. , McDowell Lee R. , Pierzynski Gary M. , Rubin Alan , Van Riper Gary G.
Published: June 2010

The USEPA standards (40 CFR Part 503) for the use or disposal of sewage sludge (biosolids) derived risk‐based numerical values for Mo for the biosolids → land → plant → animal pathway (Pathway 6). Following legal challenge, most Mo numerical standards were withdrawn, pending additional field‐generated data using modern biosolids (Mo concentrations <75 mg kg−1) and a reassessment of this pathway. This paper presents a reevaluation of biosolids Mo data, refinement of the risk assessment algorithms, and a reassessment of Mo‐induced hypocuprosis from land application of biosolids. Forage Mo uptake coefficients (UC) are derived from field studies, many of which used modern biosolids applied to numerous soil types, with varying soil pH values, and supporting various crops. Typical cattle diet scenarios are used to calculate a diet‐weighted UC value that realistically represents forage Mo exposure to cattle. Recent biosolids use data are employed to estimate the fraction of animal forage (FC) likely to be affected by biosolids applications nationally. Field data are used to estimate long‐term Mo leaching and a leaching correction factor (LC) is used to adjust cumulative biosolids application limits. The modified UC and new FC and LC factors are used in a new algorithm to calculate biosolids Mo Pathway 6 risk. The resulting numerical standards for Mo are cumulative limit (RPc) = 40 kg Mo ha−1, and alternate pollutant limit (APL) = 40 mg Mo kg−1 We regard the modifications to algorithms and parameters and calculations as conservative, and believe that the risk of Mo‐induced hypocuprosis from biosolids Mo is small. Providing adequate Cu mineral supplements, standard procedure in proper herd management, would augment the conservatism of the new risk assessment.
Spatiotemporal Variability of Wet Atmospheric Nitrogen Deposition to the Neuse River Estuary, North Carolina
Authors: Whitall David R. , Paerl Hans W.
Published: June 2010

Excessive nitrogen (N) loading to N‐sensitive waters such as the Neuse River estuary (North Carolina) has been shown to promote changes in microbial and algal community composition and function (harmful algal blooms), hypoxia and anoxia, and fish kills. Previous studies have estimated that wet atmospheric deposition of nitrogen (WAD‐N), as deposition of dissolved inorganic nitrogen (DIN: NO−3, NH3/NH+4) and dissolved organic nitrogen, may contribute at least 15% of the total externally supplied or “new” N flux to the coastal waters of North Carolina. In a 3‐yr study from June 1996 to June 1999, we calculated the weekly wet deposition of inorganic and organic N at eleven sites on a northwest–southeast transect in the watershed. The annual mean total (wet DIN + wet organics) WAD‐N flux for the Neuse River watershed was calculated to be 956 mg N/m2/yr (15026 Mg N/yr). Seasonally, the spring (March–May) and summer (June–August) months contain the highest total weekly N deposition; this pattern appears to be driven by N concentration in precipitation. There is also spatial variability in WAD‐N deposition; in general, the upper portion of the watershed receives the lowest annual deposition and the middle portion of the watershed receives the highest deposition. Based on a range of watershed N retention and in‐stream riverine processing values, we estimate that this flux contributes approximately 24% of the total “new” N flux to the estuary.
Movement of Coliform Bacteria and Nutrients in Ground Water Flowing through Basalt and Sand Aquifers
Authors: Entry James A. , Farmer Neal
Published: June 2010

Large‐scale deposition of animal manure can result in contamination of surface and ground water and in potential transfer of disease‐causing enteric bacteria to animals or humans. We measured total coliform bacteria (TC), fecal coliform bacteria (FC), NO3, NH4, total P, and PO4in ground water flowing from basalt and sand aquifers, in wells into basalt and sand aquifers, in irrigation water, and in river water. Samples were collected monthly for 1 yr. Total coliform and FC numbers were always higher in irrigation water than in ground water, indicating that soil and sediment filtered most of these bacteria before they entered the aquifers. Total coliform and FC numbers in ground water were generally higher in the faster flowing basalt aquifer than in the sand aquifer, indicating that the slower flow and finer grain size may filter more TC and FC bacteria from water. At least one coliform bacterium/100 mL of water was found in ground water from both basalt and sand aquifers, indicating that ground water pumped from these aquifers is not necessarily safe for human consumption according to the American Public Health Association and the USEPA. The NO3concentrations were usually higher in water flowing from the sand aquifer than in water flowing from the basalt aquifer or in perched water tables in the basalt aquifer. The PO4concentrations were usually higher in water flowing from the basalt aquifer than in water flowing from the sand aquifer. The main concern is fecal contamination of these aquifers and health consequences that may arise from human consumption.
A Transport Model with Coupled Ternary Exchange and Chemisorption Retention for Hydrazinium Cations
Authors: Mansell R. S. , Bloom S. A. , Downs W. C.
Published: June 2010

A numerical model was developed to describe the fate and transport of hydrazinium N2H+5and competing Ca2+and H+cations applied in acidic solutions to columns of Ca2+/H+–saturated sandy soil during steady saturated flow conditions. Instantaneous ternary H+–Ca2+–N2H+5cation exchange using the Gaines–Thomas approach was combined with second‐order, irreversible, kinetic chemisorption of exchange‐phase N2H+5ions as major retention mechanisms for N2H+5Exchange‐mediated chemisorption is assumed to occur as chemical binding of N2H+5ions located on carboxyl‐group exchange sites to nearby carbonyl groups, consequently decreasing the effective soil cation exchange capacity (CEC). Comparison of simulated and observed breakthrough curves (BTCs) for concentrations of N2H+5and Ca2+ions in column effluent was used in model evaluation. The cation transport model with cation exchange coupled with exchange‐mediated chemisorption provided a valid first approximation for N2H+5transport.
A Desorption–Dissolution Model for Metal Release from Polluted Soil under Reductive Conditions
Authors: Davranche Mélanie , Bollinger Jean‐Claude
Published: June 2010

Various natural or provoked situations can cause significant variations in redox conditions that can induce reductive dissolution of soil components. When this happens, heavy metals that may be bound to solid phases are released. A surface desorption–dissolution model, which takes into account the effect of reductive conditions on surface site density, was established. This model is based on conventional reactions of surface hydroxyl groups, surface complexation reactions with cations and double‐layer theory. The solid dissolution rate was taken into account, by following changes in total surface site number (i.e., cation exchange capacity [CEC]) under reductive conditions. This term was introduced in an electrostatic desorption model. Curves obtained by this calculation provided a good fit of experimental data as shown by statistical parameters. Experimental data corresponded to Pb and Cd released from a cultivated soil under reductive conditions induced by sodium ascorbate.
Phosphorus Export from an Agricultural Watershed: Linking Source and Transport Mechanisms
Authors: McDowell Richard , Sharpley Andrew , Folmar Gordon
Published: June 2010

Many source and transport factors control P loss from agricultural landscapes; however, little information is available on how these factors are linked at a watershed scale. Thus, we investigated mechanisms controlling P release from soil and stream sediments in relation to storm and baseflow P concentrations at four flumes and in the channel of an agricultural watershed. Baseflow dissolved reactive phosphorus (DRP) concentrations were greater at the watershed outflow (Flume 1; 0.042 mg L−1) than uppermost flume (Flume 4; 0.028 mg L−1). Conversely, DRP concentrations were greater at Flume 4 (0.304 mg L−1) than Flume 1 (0.128 mg L−1) during stormflow. Similar trends in total phosphorus (TP) concentration were also observed. During stormflow, stream P concentrations are controlled by overland flow–generated erosion from areas of the watershed coincident with high soil P. In‐channel decreases in P concentration during stormflow were attributed to sediment deposition, resorption of P, and dilution. The increase in baseflow P concentrations downstream was controlled by channel sediments. Phosphorus sorption maximum of Flume 4 sediment (532 mg kg−1) was greater than at the outlet Flume 1 (227 mg kg−1). Indeed, the decrease in P desorption between Flumes 1 and 4 sediment (0.046 to 0.025 mg L−1) was similar to the difference in baseflow DRP between Flumes 1 and 4 (0.042 to 0.028 mg L−1). This study shows that erosion, soil P concentration, and channel sediment P sorption properties influence streamflow DRP and TP. A better understanding of the spatial and temporal distribution of these processes and their connectivity over the landscape will aid targeting remedial practices.
Prediction of Soil Organic Partition Coefficients by a Soil Leaching Column Chromatographic Method
Authors: Xu Feng , Liang Xinmiao , Lin Bingcheng , Su Fan , Schramm Karl‐Werner , Kettrup Antonius
Published: June 2010

The soil organic partition coefficient (Koc) is one of the most important parameters to depict the transfer and fate of a chemical in the soil–water system. Predicting Koc by using a chromatographic technique has been developing into a convenient and low‐cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol–water eluents was developed to predict the Koc of hydrophobic organic chemicals (HOCs), over a log Koc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent k′w could be obtained by linearly extrapolating capacity factors in methanol–water eluents (k′) with various volume fractions of methanol (φ). The important effects of solute activity coefficients in water on k′w and Koc were illustrated. Hence, the correlation between log Koc and log k′w (and log k′) exists in the soil. The correlation coefficient (r) of the log Koc vs. log k′w correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log Koc–log k′ correlations were no less than 0.968, with φ ranging from 0 to 0.50. The smaller the φ, the higher the r Therefore, it is recommended that the eluent of smaller φ, such as water, be used for accurately estimating Koc Correspondingly, the r value of the log Koc–log k′w correlation on a reversed‐phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict Koc indirectly from a correlation with k′w than the reversed‐phase liquid chromatographic (RPLC) one.
Toxicity of Ozonated Animal Manure to the House Fly, Musca domestica
Authors: Masten Susan J. , Kim‐Yang Hyesoon , Walker Edward D. , Roman Hugo , Yokoyama Melvin T.
Published: June 2010

Swine manure slurries were ozonated at a dosage of 1 g/L and tested for their toxicity to the house fly (Musca domestica). The observed toxicity of ozonated swine manure was consistent and independent of origin of the swine manure. A dose (dilution) response curve was performed. A 50% dilution in the ozonated swine manure slurry resulted in 90% reduction in toxicity. Neither the synthetic nor ozonated synthetic swine manure, both of which contained higher concentrations of formaldehyde and three other unidentified carbonyl compounds than the ozonated swine manure, were toxic to the flies. Ozonated swine manure slurry was centrifuged and passed through a 0.45‐μm filter. The liquid phase was as toxic as the unfiltered slurry; as such, the toxicant appears to be present in liquid phase. Neither ammonia, hydrogen sulfide, formaldehyde, nor other simple aldehydes appeared to be the toxic agent. The toxic agent appears to be a polar chemical compound and is concentrated in the urine. Several possible compounds have been identified. The toxicity of untreated and ozonated manure slurries from different livestock was compared. Six animal manure slurries (beef and dairy cattle, horse, poultry, sheep, and swine) were ozonated (dosage of 1 g/L) and tested for toxicity to the house fly. Ozonated dairy cattle manure slurry showed 78% mortality after 72 h, whereas ozonated swine manure slurry achieved a 100% mortality rate in 48 h. Neither the unozonated dairy nor swine manure slurries, nor any of the other raw or ozonated manure slurries, were toxic to the flies.
Oxidation of Phenolic Acid Derivatives by Soil and Its Relevance to Allelopathic Activity
Authors: Ohno Tsutomu
Published: June 2010

Previous studies have suggested that phenolic acids from legume green manures may contribute to weed control through allelopathy. The objectives of this study were to investigate the oxidation reactions of phenolic acids in soil and to determine the subsequent effects of oxidation upon phytotoxicity. Soils were reacted for 18 h with 0.25 mmol L−1 benzoic and cinnamic acid derivative solutions and Mn release from the suspension was used as a marker for phenolic acid oxidation. The extent of oxidation in soil suspensions was in the order of 3,4‐dihydroxy‐ > 4‐hydroxy‐3‐methoxy‐ > 4‐hydroxy‐ ≅ 2‐hydroxy–substituted benzoic and cinnamic acids. The same ranking was observed for cyclic voltammetry peak currents of the cinnamic acid derivatives. This suggests that the oxidation of phenolic acids is controlled by the electron transfer step from the sorbed phenolic acid to the metal oxide. A bioassay experiment showed that the 4‐hydroxy‐, 4‐hydroxy‐3‐methoxy‐, and 3,4‐dihydroxy–substituted cinnamic acids were bioactive at 0.25 mmol L−1 concentration. Reaction with soil for 18 h resulted in the elimination of bioactivity of these three cinnamic acids at the 5% significance level. The oxidative reactivity of phenolic acids may limit the potential of allelopathy as a component of an integrated weed management system. However, the initial phytotoxicity after soil incorporation may coincide with the early, critical stage of weed emergence and establishment, so that allelopathic phenolic acids may still play a role in weed management despite their reactivity in soil systems.
Field‐Scale Remediation of a Metolachlor‐Contaminated Spill Site Using Zerovalent Iron
Authors: Comfort S. D. , Shea P. J. , Machacek T. A. , Gaber H. , Oh B.‐T.
Published: June 2010

Pesticide spills are common occurrences at agricultural cooperatives and farmsteads. When inadvertent spills occur, chemicals normally beneficial can become point sources of ground and surface water contamination. We report results from a field trial where approximately 765 m3 of soil from a metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] spill site was treated with zerovalent iron (Fe0). Preliminary laboratory experiments confirmed metolachlor dechlorination by Fe0 in aqueous solution and that this process could be accelerated by adding appropriate proportions of Al2(SO4)3 or acetic acid (CH3COOH). The field project was initiated by moving the stockpiled, contaminated soil into windrows using common earth‐moving equipment. The soil was then mixed with water (0.35–0.40 kg H2O kg−1) and various combinations of 5% Fe0 (w/w), 2% Al2(SO4)3 (w/w), and 0.5% acetic acid (v/w). Windrows were covered with clear plastic and incubated without additional mixing for 90 d. Approximately every 14 d, the plastic sheeting was removed for soil sampling and the surface of the windrows rewetted. Metolachlor concentrations were significantly reduced and varied among treatments. The addition of Fe0 alone decreased metolachlor concentration from 1789 to 504 mg kg−1 within 90 d, whereas adding Fe0 with Al2(SO4)3 and CH3COOH decreased the concentration from 1402 to 13 mg kg−1 These results provide evidence that zerovalent iron can be used for on‐site, field‐scale treatment of pesticide‐contaminated soil.
Runoff Loss of Pesticides and Soil: A Comparison between Vegetative Mulch and Plastic Mulch in Vegetable Production Systems
Authors: Rice Pamela J. , McConnell Laura L. , Heighton Lynne P. , Sadeghi Ali M. , Isensee Allan R. , Teasdale John R. , Abdul‐Baki Aref A. , Harman‐Fetcho Jennifer A. , Hapeman Cathleen J.
Published: June 2010

Current vegetable production systems use polyethylene (plastic) mulch and require multiple applications of agrochemicals. During rain events, runoff from vegetable production is enhanced because 50 to 75% of the field is covered with an impervious surface. This study was conducted to quantify off‐site movement of soil and pesticides with runoff from tomato (Lycopersicon esculentum Mill.) plots containing polyethylene mulch and a vegetative mulch, hairy vetch (Vicia villosa Roth). Side‐by‐side field plots were instrumented with automated flow meters and samplers to measure and collect runoff, which was filtered, extracted, and analyzed to determine soil and pesticide loss. Seasonal losses of two to four times more water and at least three times as much sediment were observed from plots with polyethylene mulch (55.4 to 146 L m−2 and 247 to 535 g m−2, respectively) versus plots with hairy vetch residue (13.7 to 75.7 L m−2 and 32.8 to 118 g m−2, respectively). Geometric means (±standard deviation) of total pesticide loads for chlorothalonil (tetrachloroisophthalonitrile) and α‐ and β‐endosulfan (6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzodioxathiepin 3‐oxide) for a runoff event were 19, 6, and 9 times greater from polyethylene (800 ± 4.6, 17.6 ± 3.9, and 39.1 ± 4.9 μg m−2, respectively) than from hairy vetch mulch plots (42 ± 6.0, 2.8 ± 5.0, and 4.3 ± 4.6 μg m−2, respectively) due to greater concentrations and larger runoff volumes. The increased runoff volume, soil loss, and off‐site loading of pesticides measured in runoff from the polyethylene mulch suggests that this management practice is less sustainable and may have a harmful effect on the environment.
Contrasting Nitrate Adsorption in Andisols of Two Coffee Plantations in Costa Rica
Authors: Ryan M. C. , Graham G. R. , Rudolph D. L.
Published: June 2010

Fertilizer use in coffee plantations is a suspected cause of rising ground water nitrate concentrations in the ground water–dependent Central Valley of Costa Rica. Nitrate adsorption was evaluated beneath two coffee (Coffea arabica L.) plantations in the Central Valley. Previous work at one site had identified unsaturated zone nitrate retardation relative to a tritium tracer. Differences in nitrate adsorption were assessed in cores to 4 m depth in Andisols at this and one other plantation using differences in KCl‐ and water‐extractable nitrate as an index. Significant adsorption was confirmed at the site of the previous tracer test, but not at the second site. Anion exchange capacity, X‐ray diffraction data, extractable Al and Si, and soil pH in NaF corroborated that differences in adsorption characteristics were related to subtle differences in clay mineralogy. Soils at the site with significant nitrate adsorption showed an Al‐rich allophane clay content compared with a more weathered, Si‐rich allophane and halloysite clay mineral content at the site with negligible adsorption. At the site with significant nitrate adsorption, nitrate occupied less than 10% of the total anion adsorption capacity, suggesting that adsorption may provide long‐term potential for mitigation or delay of nitrate leaching. Evaluation of nitrate sorption potential of soil at local and landscape scales would be useful in development of nitrogen management practices to reduce nitrate leaching to ground water.
Fate of Dimethyldiselenide in Soil
Authors: Zhang Yiqiang , Frankenberger William T.
Published: June 2010

Volatilization of dimethyldiselenide (DMDSe) is one of the most important processes for removing selenium (Se) from Se‐contaminated environments. However, the fate of DMDSe in soil is not known. In this study, we monitored the changes of DMDSe in the head space of soil samples spiked with known amounts of DMDSe gas, and fractionated and speciated the resulting Se forms in soil. Dimethyldiselenide was highly dissolved in water in a closed air–water system and was highly sorbed onto soil in a closed air–soil system. Chemical and biological transformations of DMDSe in soil converted a large amount of DMDSe to nonvolatile Se compounds. Elemental Se [Se(0)] and nonvolatile organic Se were the major forms of Se transformed from spiked DMDSe. Microbial conversion of DMDSe to dimethylselenide (DMSe) in soil increased the production of DMSe. Calculation of the mass recovery showed that about 85 to 93% of the added DMDSe was recovered as Se(0), organic Se, organic material Se (OM‐Se), Se(IV), and volatile organic Se in the head space in the non‐autoclaved soils and 50 to 70% of the added DMDSe was recovered in the autoclaved soils. These results indicate that DMDSe is not a stable form of Se, and it may be one of the important precursors of DMSe in the soil environment.
Selenium Stable Isotope Ratios in California Agricultural Drainage Water Management Systems
Authors: Herbel Mitchell J. , Johnson Thomas M. , Tanji Kenneth K. , Gao Suduan , Bullen Thomas D.
Published: June 2010

Selenium stable isotope ratios are known to shift in predictable ways during various microbial, chemical, and biological processes, and can be used to better understand Se cycling in contaminated environments. In this study we used Se stable isotopes to discern the mechanisms controlling the transformation of oxidized, aqueous forms of Se to reduced, insoluble forms in sediments of Se‐affected environments. We measured 80Se/76Se in surface waters, shallow ground waters, evaporites, digested plants and sediments, and sequential extracts from several sites where agricultural drainage water is processed in the San Joaquin Valley of California. Selenium isotope analyses of samples obtained from the Tulare Lake Drainage District flow‐through wetland reveal small isotopic contrasts (mean difference 0.7‰) between surface water and reduced Se species in the underlying sediments. Selenium in aquatic macrophytes was very similar isotopically to the NaOH and Na2SO3 sediment extracts designed to recover soluble organic Se and Se(0), respectively. For the integrated on‐farm drainage management sites, evaporite salts were slightly (approximately 0.6‰) enriched in the heavier isotope relative to the inferred parent waters, whereas surface soils were slightly (approximately 1.4‰) depleted. Bacterial or chemical reduction of Se(VI) or Se(IV) may be occurring at these sites, but the small isotopic contrasts suggest that other, less isotopically fractionating mechanisms are responsible for accumulation of reduced forms in the sediments. These findings provide evidence that Se assimilation by plants and algae followed by deposition and mineralization is the dominant transformation pathway responsible for accumulation of reduced forms of Se in the wetland sediments.
Influence of Manure Application on Surface Energy and Snow Cover
Authors: Kongoli C.E. , Bland W.L.
Published: June 2010

Winter landspreading is an important part of manure management in the U.S. Upper Midwest. Although the practice is thought to lead to excessive P runoff losses, surprisingly little has been learned from field experiments or current water quality models. We captured knowledge gained from winter manure landspreading experiments by modifying a mechanistic snow ablation model to include manure. The physically based, modified model simulated the observed delay in snow cover disappearance and surface energy balance changes caused by application of the manure. Additional model simulations of surface energy balance estimates of radiation and turbulent fluxes showed that during intense melting events the manure on top of snow significantly reduced the energy available for melt of the snow underneath, slowing melt. The effect was most pronounced when snowmelt was driven by both relatively high solar radiation and turbulent heat fluxes. High absorbed shortwave radiation caused significant warming of the manure, which led to substantial losses in turbulent fluxes and longwave radiation. Simulations of snowmelt also showed that manure applications between 45 and 100 Mg ha−1 significantly reduced peak snowmelt rates, in proportion to the manure applied. Lower snowmelt rates beneath manure may allow more infiltration of meltwater compared with bare snow. This infiltration and attenuated snowmelt runoff may partially mitigate the enhanced likelihood of P runoff from unincorporated winter‐spread manure.