1999 Progress Report: Pesticide Transport in Subsurface and Surface Water Systems

EPA Grant Number: R825433C052
Subproject: this is subproject number 052 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Pesticide Transport in Subsurface and Surface Water Systems
Investigators: Marino, Miguel
Institution: University of California - Davis
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1996 through September 30, 2000
Project Period Covered by this Report: October 1, 1998 through September 30, 1999
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


Investigates the fate of non-point source (NPS) pesticides in subsurface and surface water by developing a systematic procedure and practical analytical tool, applicable at a watershed scale, for evaluation of the leaching potential of pesticide residues to groundwater and the potential threat of pesticide emissions to adjacent rivers/streams.

Progress Summary:

Because of the ubiquitous nature and potential chronic health and environmental effects, NPS contamination has become a focal point of public attention, particularly regarding the pollution of both subsurface and surface water resources. This project focuses on pesticide-induced contamination in surface runoff, soil solution, groundwater, and river/stream. Pesticide leaching leads to contamination of subsurface water systems. Due to pesticide loading from surface runoff, erosion, and groundwater percolation to an adjacent river/stream, the related surface water system may also be polluted. From a systematic point of view, the integrity of the hydrologic system and the spatial and temporal dynamic connections of all components associated with water, sediments, and pesticide transport are emphasized. This research is oriented by evaluating the potential negative impact of pesticide residues on water resources and the relevant ecosystem and predicting future exposure levels of pesticide residues under different land-use and agricultural practices so as to circumvent further deterioration by using modeling techniques.

The analytical integrated model proposed in this research to analyze the fate and transport of pesticide residues in the surface and subsurface environment would require less volume of data to provide quick decisions on land use, pesticide application, and agricultural management. With the help of this model, long-term prediction of pesticide exposure levels in ground water and surface water systems can be analyzed, which subsequently would provide input for health risk models or ecological models focusing on the impact of pesticide residues on the fauna and flora in rivers/streams.

Pesticide contamination potential to the hydrologic system, including both subsurface and surface water, is largely based on a combination of mobility and transformation properties. These two properties are influenced by a set of physical, (bio)chemical, and physiological processes such as infiltration (rainfall and irrigation water), evapotranspiration, crop-root uptake, advection, dispersion, sorption, decay, and volatilization. They are also controlled by the hydrogeological settings and agricultural practices, such as formation structure, properties of media and boundary conditions, as well as the timing and amount of pesticide application. Hence, understanding the interaction between the different processes and modeling them at the local and regional scale is an important step toward preventing or minimizing deterioration of water resources and the related ecosystem and conducting risk assessment associated with human health and environmental quality.

Currently, an analytical integrated model to determine the fate and transport of pesticide residues has been developed. The integrated model consists of the models of the surface zone, crop root zone, vadose zone, aquifer and river/stream which are connected by a lumped bridge model. The entire soil profile is divided into the surface zone, root zone, and vadose zone. A thin surface zone is defined to facilitate the modeling of the interaction between overland flow and soil solution, and corresponding processes, such as runoff and erosion. Complete mixing, uniform soil and hydraulic properties, and one-dimensional downward soil water movement are assumed in each soil zone model. Pesticide transport and transformation in three phases--dissolved, adsorbed, and vapor--are considered. The modeled processes in soil include leaching, linear-equilibrium sorption, linear-equilibrium liquid-vapor partitioning, and first-order degradation. In addition, runoff and erosion losses of pesticide residues and volatilization from the soil surface to atmosphere are considered in the surface zone. The SCS (Soil Conservation Service) method is applied to estimate the runoff; the Modified Universal Soil Loss Equation (MUSLE) is used to calculate the eroded sediment yield and the film theory is employed in the computation of volatilization. In the root zone model, crop-root uptake of the pesticide residues is estimated by using the water uptake rate of crop and transpiration stream concentration factor. For the aquifer, a two-dimensional analytical transport model is used and solved analytically to describe advection and dispersion of a reactive solute and steady-state groundwater flow is assumed. The pesticide transport in a river is simulated by a connected multi-reach model, which vertically consists of a water column and an active bed. Pesticide residues in dissolved or adsorbed phases are loaded to a river reach from the upstream inflow, runoff, erosion, and groundwater percolation. The pesticide residues in dissolved and/or adsorbed phases are subject to first-order degradation, linear-equilibrium sorption, volatilization, settling, resuspension and sedimentation. Due to the significant change in the temperature of the river water, the effect of the water temperature on the pesticide transport is taken into account in the river model. Finally, a lumped bridge model is used to link the subsurface and surface pesticide transport models. The developed model is able to provide time series of pesticide concentrations in all soil zones and both temporal and spatial variations in the concentration of pesticide residues in groundwater and the water column and active bed of the adjacent river.

The connected soil-aquifer model has been tested with a set of pesticides having different physical and chemical properties in different soils under different climatic and application conditions, to assess the long-term prediction of pesticide residues at supply wells on a hypothetical system. Also, the soil-aquifer-river integrated model has been applied to a simplified hydrologic system and its performance has been compared with an existing, widely used and tested numerical counterpart, which couples PRZM2 (simulating the transport of pesticide residues in soil zones) with MT3D interfaced with MODFLOW (groundwater flow and transport simulation codes). The comparison indicates that the results calculated by analytical integrated model and the numerical models are in good agreement.

Future Activities:

Eventually, a risk-based assessment of pesticide-induced water contamination and its negative effect on ecosystems will be carried out. To enhance the existing model, the hydrodynamic component of the integrated model, which simulates water movement in soil, aquifer, and river as well as their interactions will be developed. The CSTRs-in-series model structure (continuous stirred tank reactors) will be employed in the soil and river models to describe more detailed spatial variations in the concentration of pesticide residues. Eventually, a watershed-scale pesticide transport modeling system will be established to account for multi-site pesticide-induced contamination by developing a higher level bridge model to coordinate and connect all branch models in a watershed. As an important part of this project, the integrated model will be applied to one-site and/or multi-site problems in the Sacramento River watershed. The existing contamination induced by some pesticide residues will be examined and the future pollution trend will be predicted under different management practices in order to evaluate their effects on vulnerability of water resources to the pesticides. For the purpose of test and verification of the model, the results produced by the integrated model will also be compared against the observed values. Furthermore, based on comprehensive hydrodynamic and water quality modeling, watershed-scale assessment of the related ecosystem under some environmental stresses (especially for pesticides) will be performed by linking the models developed by different research groups.

Supplemental Keywords:

RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Water & Watershed, Aquatic Ecosystem, Fate & Transport, Monitoring/Modeling, Environmental Microbiology, Biochemistry, Terrestrial Ecosystems, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Watersheds, fate and transport, aquatic, watershed management, ambient particle properties, ecosystem assessment, Sacramento River, sediment transport, pesticides, restoration strategies, modeling, watershed influences, hydrology, wetland restoration, integrated watershed model, chemical kinetics, aquatic ecosystems, environmental stress, source load modeling, watershed sustainablility, material transport, groundwater contamination, ecosystem stress, ecology assessment models, ecological impact, agrochemicals, vadose zone, ecological research, watershed restoration

Progress and Final Reports:

Original Abstract
  • 1997
  • 1998
  • Final Report

  • Main Center Abstract and Reports:

    R825433    EERC - Center for Ecological Health Research (Cal Davis)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
    R825433C002 Sacramento River Watershed
    R825433C003 Endocrine Disruption in Fish and Birds
    R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
    R825433C005 Fish Developmental Toxicity/Recruitment
    R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
    R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
    R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
    R825433C009 Modeling Ecosystems Under Combined Stress
    R825433C010 Mercury Uptake by Fish
    R825433C011 Clear Lake Watershed
    R825433C012 The Role of Fishes as Transporters of Mercury
    R825433C013 Wetlands Restoration
    R825433C014 Wildlife Bioaccumulation and Effects
    R825433C015 Microbiology of Mercury Methylation in Sediments
    R825433C016 Hg and Fe Biogeochemistry
    R825433C017 Water Motions and Material Transport
    R825433C018 Economic Impacts of Multiple Stresses
    R825433C019 The History of Anthropogenic Effects
    R825433C020 Wetland Restoration
    R825433C021 Sierra Nevada Watershed Project
    R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
    R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
    R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
    R825433C025 Regional Movement of Toxics
    R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
    R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
    R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
    R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
    R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
    R825433C031 Pre-contact Forest Structure
    R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
    R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
    R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
    R825433C035 Border Rivers Watershed
    R825433C036 Toxicity Studies
    R825433C037 Watershed Assessment
    R825433C038 Microbiological Processes in Sediments
    R825433C039 Analytical and Biomarkers Core
    R825433C040 Organic Analysis
    R825433C041 Inorganic Analysis
    R825433C042 Immunoassay and Serum Markers
    R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
    R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
    R825433C045 Microbial Community Assays
    R825433C046 Cumulative and Integrative Biochemical Indicators
    R825433C047 Mercury and Iron Biogeochemistry
    R825433C048 Transport and Fate Core
    R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
    R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
    R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
    R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
    R825433C053 Currents in Clear Lake
    R825433C054 Data Integration and Decision Support Core
    R825433C055 Spatial Patterns and Biodiversity
    R825433C056 Modeling Transport in Aquatic Systems
    R825433C057 Spatial and Temporal Trends in Water Quality
    R825433C058 Time Series Analysis and Modeling Ecological Risk
    R825433C059 WWW/Outreach
    R825433C060 Economic Effects of Multiple Stresses
    R825433C061 Effects of Nutrients on Algal Growth
    R825433C062 Nutrient Loading
    R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
    R825433C064 Chlorinated Hydrocarbons
    R825433C065 Sierra Ozone Studies
    R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
    R825433C067 Terrestrial - Agriculture
    R825433C069 Molecular Epidemiology Core
    R825433C070 Serum Markers of Environmental Stress
    R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
    R825433C072 Molecular Monitoring of Microbial Populations
    R825433C073 Aquatic - Rivers and Estuaries
    R825433C074 Border Rivers - Toxicity Studies