Agricultural Development and Environmental Research American and Czechoslovak Perspectives: Proceedings of a Bilateral Workshop (1987) / Chapter Skim
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'ASSESSMENT OF GROUNDWATER CONTAMINATION PROBLEMS IN AGRICULTURAL AREAS'
'ASSESSMENT OF GROUNDWATER CONTAMINATION PROBLEMS IN AGRICULTURAL AREAS'
Pages 65-75
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From page 65... ...
The sources of contamination are many and have included chemical spills in railway or highway accidents; chemical leaks from underground storage tanks, wastewater treatment ponds, and sewage disposal systems; chemical leachate from land disposal of industrial wastes; and pesticide movement from the soil surface after application. Contaminants include synthetic organic chemicals and inorganic pollutants, particularly nitrates and heavy metals.
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From page 66... ...
The assessment procedures desired depend upon the approaches available to control the problem. Available control options include: 1.
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From page 67... ...
In the first option, contaminated drinking water supplies can be treated for removal of pesticide residues. An effective monitoring program must be maintained to identify treatment needs and confirm continued treatment effectiveness.
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From page 68... ...
BMPs for soil erosion have proven to be effective in preventing soil loss and are known to be beneficial in controlling surface water pollution from agricultural runoff. BMPs for pesticides are not as well developed but include methods such as application timing, slow release formulations, chemical substitution, and integrated pest management.
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From page 69... ...
RESEARCH APPROACHES Assessment methodologies that can predict the behavior of pesticides in the environment is the goal of the research approach adopted by EPA. The major phases of the approach include: • identification and mathematical description of physical, chemical, biological, and transport processes that transform pesticides within soils and groundwater; • characterization of the environmental properties that influence pesticide behavior in soil/groundwater systems; • characterization of pesticide use patterns within the environment; • development of simulation models for predicting leaching and groundwater transport; • conduct of field model validation studies; • demonstration of assessment methodologies.
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From page 70... ...
Molecular diffusion and advective mixing combine to spread contaminant plumes. • Volatilization: Pesticide escape to the atmosphere is important in surface soil layers and may play a dominant role in determining the mass of pesticide available for leaching.
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From page 71... ...
Detailed field monitoring studies that enable complete characterization of the soil environment and subsequent measurement of the fate and movement of pesticides are necessary. Comparison of these data with the predicted values produced by models demonstrate the uncertainties inherent in the modeling process and may identify model errors or incomplete understanding of the underlying processes.
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From page 72... ...
All phases of these research approaches are currently underway within EPA. The multidisciplinary approach of combining elements of laboratory, field, and mathematical analyses has produced groundwater assessment tools now in use for regulating pesticides.
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From page 73... ...
The environmental properties that influence aldicarb leaching and transport included precipitation, evaporation, soil water content, hydraulic conductivity, soil organic matter, pH, and gradient. Statistical characterization of these properties was combined with citrus production and chemical use data to delineate systems requiring analysis as shown in Figure 1.
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From page 74... ...
The relevant environmental and chemical use data were developed from soil data bases and census data. Finally, the results were communicated to regulators who developed the control policies designed to permit continued use of aldicarb while preventing unacceptable groundwater contamination.
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From page 75... ...
75 iooo r < EC LLl o 42 ug/l No Decay 200 400 600 D1STANCE (feet) 800 1000 FIGURE 2 Concentration in downgradient well from citrus groves for the worst case year in ten years.
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