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1991, JAWRA Journal of the American Water Resources Association
ABSTRACT: An evaluation of the intermedia movement of pesticides applied under various land management systems already in place, or to be implemented, under the Conservation Reserve and Conservation Compliance programs is presented. The simulation modeling approach followed in this analysis consists of a mathematical programming model and leaching/surface runoff, Pesticide Root Zone Model (PRZM) models. Special care was taken to ensure that the physical model was sensitive to the chemical characteristics of individual pesticides and the important physical changes brought about by different agricultural practices. Results show that, although these programs as now planned, increase farm income and achieve soil conservation goals, they may adversely affect ground water quality. Also, depending on soil and location characteristics, there are tradeoffs between surface and ground water quality implications. Hence, if these programs are to address water quality problems, the recommended pr...
jpa, 1992
The likelihood of groundwater contamination by agricultural chemicals differs widely across the USA as critical factors, such as rainfall, soil type, and depth to groundwater vary. The potential financial impacts of chemical use restrictions also differ regionally. An evaluation was conducted on the environmental and economic impacts of alternative chemical pest control methods and irrigation practices used by producers in the High Plains region of Oklahoma. The EPIC-PST computer model was used to simulate simultaneously the effect of different agricultural management practices on crop yields and pesticide losses by surface runoff, sediment movement, and leaching under irrigation. As an example, to control greenbugs [Schizaphis graminum (Rondani)] in grain sorghum [Sorghum bicolor (L.) Moench], the use of ethyl parathion (0,0-diethyl 0-4-nitrophenyl phosphorothioate) instead of carbofuran (2,3-dihydro-2,2dimethyl-7-benzofuranyl methylcarbamate) potentially may reduce environmental impacts, but at the expense of income from grain production. On the other hand, to control stalk borers (Papaipema nebris) in corn (Zea mays L.), positive environmental and economic impacts may result from the use of permethrin [(3-phenoxyphenyl)methyl(I)cis,trans-ethenyl-2,2dimethylcyclopropane-carboxylate] instead of carbofuran. Simulation results also indicate that surface irrigation could result in larger leaching losses of chemicals than would sprinkler irri
Abstract: Contribution of pollution from pesticides is often located to minor areas within a field. Areas with coarse textured materials in the soil profile often represent” hot spots” with high risk of leaching, but also areas with example structured clay soils may be “hot spots”. Other areas can be slopes or bottoms in depressions on plateaus were water can be ponded in wet periods or in springtime before the frost has disappeared from the soil profile.
Environmental Toxicology and Chemistry, 2002
As part of a process to improve confidence in the results of regulatory modeling, predictions of pesticide root zone model (PRZM) 3.12 were compared with measured data collected in nine different runoff field studies. This comparison shows that PRZM 3.12 provides a reasonable estimate of chemical runoff at the edge of a field. Simulations based on the best choices for input parameters (no conservatism built into input parameters) are generally within an order of magnitude of measured data, with better agreement observed both for larger events and for cumulative values over the study period. When the model input parameters are calibrated to improve the hydrology, the fit between predicted and observed data improves (results are usually within a factor of three). When conservatism is deliberately introduced into the input pesticide parameters, substantial overprediction of runoff losses occur. Recommendations for future work to improve regulatory models include implementation of more sophisticated evapotranspiration routines, allowing for seasonal variation of various model parameters (such as curve numbers, crop cover, and Manning's surface roughness coefficients), better procedures for estimating site-specific degradation rates in surface and subsoils, and improved sorption routines.
Environmental Toxicology and Chemistry, 2002
As part of a process to improve confidence in the results of regulatory modeling, predictions of the pesticide root zone model (PRZM) 3.12 were compared with measured data collected in nine different field leaching studies. Reasonable estimates of leaching were obtained with PRZM 3.12 in homogeneous soils where preferential flow is not significant. The PRZM 3.12 usually did a good job of predicting movement of bromide in soil (soil and soil pore-water concentrations were generally within a factor of two of predicted values). For simulations based on the best choices for input parameters, predictions of soil pore-water concentrations for pesticides were usually within a factor of three and soil pore-water estimates within a factor of 11. When the model input parameters were calibrated to improve the simulation of hydrology, predicted pesticide concentrations in soil pore water were usually within a factor of two of measured concentrations. Because of the sensitivity of leaching to degradation rate, the most accurate predictions were obtained with pesticides with relatively slow degradation rates. When conservative assumptions were used to define input pesticide parameters, predictions of pesticide concentrations were usually a factor of two greater than when using the best estimate of input parameters without any built-in conservatism.
1990
Agricultural chemicals (fertilizers and pesticides) leached from the fields of Colorado and other parts of the United States are increasingly attacked as a major source of groundwater pollution. Leaching causes loss of fertilizers from the root zone and may cost the average farmer a significant portion of profits. Farmers and regulatory agencies need a tool to help manage these chemicals. Unfortunately, no such tool has been available until recently. Opus and PRZM, computer simulation programs, have the potential for assisting the Colorado farmer with chemical management decisions. Although they are written for areas where irrigation is not the main source of a crop's water, this study shows that they can be adapted to fit a sprinkler irrigated, farm. To evaluate these models, chemicals were applied to an experimental facility, and their movements through the soil root zone (45.7 cm, 18 inches) were monitored. Water was applied as rainfall through an overhead sprinkling system. Soil moisture was monitor~d along with chemical concentrations. Data gathered from monitoring were compared to results obtained from PRZM and Opus, without model calibration, in order to determine the usefulness of such models in a realistic setting. Comparisons showed that Opus predicted changes in soil moisture and chemical concentrations, even though it was not able to predict the
1990
Production of adequate supplies of food and fiber currently requires that pesticides be used to limit crop losses caused by insects, pathogens, weeds and other pests. Although pesticides are necessary in today' s agriculture, they can be a serious problem if they reach and contaminate ground water, especially where drinking water needs are met by ground water. The relative reduction of potential ground-water contamination due to agricultural use of pesticides was analyzed for particular sites in Utah. The potential reduction of pesticides in ground water was considered by utilizing alternative irrigation systems, water management practices and pesticides. A one-dimensional simulation model, CMLS (Chemical Movement in Layered Soils), was utilized to simulate the movement of pesticides through soils. A hydraulic irrigation model (Kinematic-wave) was used to estimate water infiltration through the soil profile for alternative furrow lengths and inflow rates. The study indicates tha...
Environmental Science and Pollution Research, 1994
A validation exercise of the SoilFug model using field runoff data from Rosemaund Farm (UK) is described. A comparison has been made of modelled and measured concentrations of several pesticides in surface water and soil during and after specific rain events following application. The field experiments were designed to obtain data on rainfall, outflows of water, pesticide application rates and concentrations in soil and water. The results were satisfactory for the undissociated pesticides (atrazine, carbofuran, dimethoate, isoproturon, lindane, simazine and trifluralin), whose concentrations in water were mostly predicted within an order of magnitude of measured data. The results for the dissociated pesticides (dichlorprop, MCPA, mecoprop) were less satisfactory, giving generally much higher predicted concentrations in water. The use of the SoilFug model is suggested for the calculation of predicted environmental concentrations (PECs) in water, since it generally produces acceptable results from a relatively small set of input data, most of which is generally available.
Environmental monitoring and assessment, 2018
Global agricultural intensification has led to increased pesticide use (37-fold from 1960 to 2005) and soil erosion (14% since 2000). Conservation tillage, including no-till (NT), has been proposed as an alternative to conventional plow till (PT) to mitigate soil erosion, but past studies have reported mixed results on the effect of conservation tillage on pesticide loss. To explore the underlying factors of these differences, a meta-analysis was conducted using published data on pesticide concentration and load in agricultural runoff from NT and PT fields. Peer-reviewed articles (1985-2016) were compiled to build a database for analysis. Contrary to expectations, results showed greater concentration of atrazine, cyanazine, dicamba, and simazine in runoff from NT than PT fields. Further, we observed greater load of dicamba and metribuzin, but reduced load of alachlor from NT fields. Overall, the concentration and the load of pesticides were greater in runoff from NT fields, especial...
Ecological Modelling, 1982
Mathematical models currently available for describing pesticide dynamics in soils were reviewed. Processes included in this review were: retention (adsorption-desorption), transformations (chemical and/or biological degradation), and convective-dispersive transport with soil-water. A large number of simulation models, with varying degrees of complexity and scope, are presently available. However, verification and extensive use of these models has generally been difficult owing to inadequate methods of measuring and/or estimating the necessary model input parameters. The ability to formulate and numerically solve complex simulation models apparently exceeds our ability to verify these models using the limited experimental data base presently available. Given the uncertainties of model parameters and the field-scale soil heterogeneity, deviations of a factor of two or more between measured and simulated results may be common. Therefore, for general use, simple models with a minimum number of inputs may provide a sufficiently accurate description of pesticide dynamics in agricultural ecosystems. Only limited amounts of field data are presently available to verify even the simple process-orientated models.
Journal of Environment Quality, 2012
This paper proposes a hydrological modeling framework to define achievable performance standards (APSs) for pesticides that could be attained after implementation of recommended management actions, agricultural practices, and available technologies (i.e., beneficial management practices [BMPs]). An integrated hydrological modeling system, Gestion Intégrée des Bassins versants à l'aide d'un Système Informatisé, was used to quantify APSs for six Canadian watersheds for eight pesticides: atrazine, carbofuran, dicamba, glyphosate, MCPB, MCPA, metolachlor, and 2,4-D. Outputs from simulation runs to predict pesticide concentration under current conditions and in response to implementation of two types of beneficial management practices (reduced pesticide application rate and 1-to 10-m-wide edge-of-field and/or riparian buffer strips, implemented singly or in combination) showed that APS values for scenarios with BMPs were less than those for current conditions. Moreover, APS values at the outlet of watersheds were usually less than ecological thresholds of good condition, when available. Upstream river reaches were at greater risk of having concentrations above a given ecological thresholds because of limited stream flows and overland loads of pesticides. Our integrated approach of "hydrological modeling-APS estimation-ecotoxicological significance" provides the most effective interpretation possible, for management and education purposes, of the potential biological impact of predicted pesticide concentrations in rivers.
European Journal of Agronomy, 2010
Agricultural practices, such as subsurface drainage, irrigation and tillage, may significantly affect pesticide leaching and, consequently, the risk of groundwater contamination. The aim of the present study was to investigate the impact of different irrigation systems on herbicide leaching to shallow groundwater through direct monitoring at the field scale in northern Italy over a 3-year period. Concentrations of the herbicide terbuthylazine (TBA) and its metabolite desethylterbuthylazine (DES) were monitored on 10 farms cropped with maize and irrigated by sprinkler, basin and border systems. Considering the results grouped according to the different irrigation systems, the mean TBA and DES concentrations was lower than the arbitrary non-health based legal limit of 0.1 g/L using sprinkler and border systems, while it was 0.19 and 0.30 g/L respectively for TBA and DES using basin systems.
Environmental Geosciences, 2002
In recent years pesticide vulnerability assessments have become increasingly important due to the increased detections of pesticides in groundwater. It is common to use simple vulnerability models that rank pesticides based on their leachability. A model sensitivity study was conducted using the leaching potential index model to evaluate the relative importance of input-parameter variability on the model predicted vulnerability. Parameters that were analyzed included organic-carbon content, depth to groundwater, soil-water velocity, soil bulk density, water content, organic-carbon partition coefficient, and pesticide degradation half-life. Results indicate that the calculated vulnerabilities are most sensitive to organic-carbon content, depth to groundwater, and vertical soil-water velocity. The sensitivity of the model to organic-carbon partition coefficient and biochemical half-life depends on the range of values given in the literature. Predicted vulnerabilities are not sensitive to bulk density and water content. This information should be useful to planners and regulatory officials who wish to determine the most important parameters to obtain measurements for when economic resources are limited.
JAWRA Journal of the American Water Resources Association, 1989
ABSTRACT: The potential surface water and ground water quality tradeoff implications from the nonpoint source provisions of the 1987 Water Quality Act are investigated in this paper using a national linear programming model developed at Iowa State University and modified by the Economic Research Service and the Leaching Evaluation of Agricultural Chemicals (LEACH) Handbook developed by the U.S. Environmental Protection Agency. The linear programming model is used to maximize net farm revenue using optimal combinations of crop rotations and tillage practices for each region of the United States given natural resource constraints. The LEACH handbook is used to determine the relative potential for pesticides to leach below the root zone for different soil types, hydrologic conditions, pesticides used, and tillage practices. The results indicate that imposing a surface water quality erosion constraint aimed at reducing sediment concentrations results in a larger decrease in farm income ...
Journal of Hydrology, 2000
Models are developed which describe leaching of pesticides in the root zone and the intermediate vadose zone, and flushing of residual solute mass in the aquifer. Pollutants' loss pathways in the soil, such as volatilization, crop uptake, and biochemical decay, are emphasized, and the effect of local dispersion and nonequilibrium transport in mobile-immobile phases is analyzed. It is shown that the effect of diffusive transfer on the leached mass fractions is dependent on the volume fraction of the immobile phase, adsorption, the apparent mass-transfer rate coefficient, the first-order decay rate in the immobile zone. Error analysis indicates that complete-mixing models can be used to simulate leaching fractions of the pollutant when the Peclet number, P r , is greater than one. However, ignoring the effect of dispersion may underestimate leaching significantly when P r Ͻ 1, such as for volatile compounds. Potential application of the models to the design of groundwater protection zones is investigated, analysis and application results demonstrate the dependence of the size of protective buffer on potential loss pathways in the soil environment, the size of the source area, and aquifer geometric, hydraulic and biochemical properties. Potential use of the models for the management of pesticides is also investigated with implication on hazardous waste land treatment.
Water Resources Research, 1994
A simulation/optimization model is developed for maximizing irrigated crop yield while avoiding unacceptable pesticide leaching. The optimization model is designed to help managers prevent non-point source contamination of shaHow groundwater aquifers. It computes optimal irrigation amounts for given soil, crop, chemical, and weather data and irrigation frequencies. It directly computes the minimurn irrigated crop yield reduction needed to prevent groundwater contamination. Constraint equations used in the model maintain a layered soil moisture volume balance; describe percolation, downward unsaturated zone solute transport and pesticide degradation; and limit the amount of pesticide reaching groundwater. Constraints are linear, piecewise linear, nonlinear, and exponential. The problem is solved using nonlinear programming optimization. The model is tested for different scenarios of irrigating corn. The modeling approach is promising as a tool to aid in the development of environmentally sound agricultural production practices. It allows direct estimation of trade-offs between crop production and groundwater protection for different management approaches. More frequent irrigation tends to give better crop yield and reduce solute movement. Trade-offs decrease with increasing irrigation frequency. More frequent irrigation reduces yield loss due to moisture stress and requires less water to fill the root zone to field capacity. This prevents the solute from moving to deeper soil layers. Yield-environmental quality trade-offs are smaller for deeper groundwater tables because deeper groundwater allows more time for chemical degradation.
2004
Pesticides are one type of pollutant found in California’s surface waters at levels that may be harmful to the aquatic ecosystem. When toxicity occurs, pesticide loadings and surface water pesticide concentrations must be reduced to levels that are not harmful to aquatic life. Factors affecting the potential for a pesticide to move “offsite” from a treated area include field soil properties, climate, grower management practices, and the physical and chemical properties of the active ingredient. This publication provides information to assist pesticide users in evaluating their choice of pesticide products on the basis of the potential to impact surface water quality.
1992
A methodology is presented that permits simultaneous consideration of the economics of production and groundwater contamination hazard o~ pesticide use. An example is constructed for weed control in soybean (Glycine max) production at Clayton, North Carolina. A cost/groundwater hazard frontier is, developed that can be used to identify and illustrate the cost tradeoffs.' of selecting alternative. weed control. strategies that reduce the risk of a.dverse health. .
Journal of the American Water Resources Association, 1989
Ground water quality is an environmental issue of national concern. Agricultural activities, because they involve large land areas, often are cited as a major contributor of ground water contamination. It appears that some degree of ground water contamination from agricultural land use is inevitable, especially where precipitation exceeds evapotranspiration. For this reason, and because agriculture differs significantly from point sources of pollution, farmers, policymakers, and scientists need alternative management strategies by which to protect ground water. Mathematical models coupled to geographic information systems to form expert systems can be important management tools for both policymakers and agricultural producers. An expert system can provide farmers, researchers, and environmental managers with information by which to better manage agricultural production systems to minimize ground water contamination. Significant research is necessary to perfect such a system, necessitating interim ground water management strategies that include not only a strong research program, but educational and public policy components as well.
Journal of the American Water Resources Association, 1992
Protection of ground water quality is of considerable importance to local, state, and federal governments. This study uses a 15-year mathematical programming model to evaluate the effectiveness of low-input agriculture, under alternative policy scenarios, as a strategy to protect ground water quality in Richmond County, Virginia. The analysis considers eight policy alternatives: cost-sharing for green manures, two restrictions on atrazine applications levels, chemical taxation, a restriction on potential chemical and nitrogen levels in ground water only and in surface and ground water, and two types of land retirement programs. The CREAMS and GLEAMS models were used to estimate nitrate and chemical leaching from the crop root zone. The economic model evaluates production practices, policy constraints, and water quality given a long-term profit maximizing objective. The results indicate that low-input agriculture alone may not be an effective ground water protection strategy. The policy impacts include partial adoption of low-input practices, land retirement, and the substitution of chemicals. Only mandatory land retirement policies reduced all chemical and nutrient loadings of ground water; however, they did not promote the use of low-input agricultural practices.
Agricultural and Resource Economics Review, 1997
A multiyear regional risk programming model was used in evaluating the impacts of different environmental policies on cropping systems, input use, nonpoint source pollution, farm income, and risk. A direct expected utility maximizing problem (DEMP) objective with a Von Neuman Morgenstern utility function was used in deriving optimal cropping systems. A biophysical simulation model provided input for the optimization. Three types of policies—taxing, regulating the aggregate, and regulating the per acre level—were studied for two farm inputs—nitrogen and atrazine. It was observed that policies had varied and multiple cross-effects on pollutant loads, farm income, and risk. This information is crucial in developing successful policies toward improving water quality. If an appropriate input policy is chosen, both targeted and nontargeted pollutant loads can be managed. The three policies varied in their effects on pollutant loads and involved tradeoffs in water quality and economic attr...
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