PESTICIDE LOSS SIMULATION AND RISK ASSESSMENT INWATERSHED SYSTEMS

摘要

There have been growing concerns over the negative effect of pesticide usage on thehuman health and the environment sustainability. It has been found out that pesticides, widely used in theworld, threaten ecosystems and even may reduce human sperm count. Pesticide residues afterapplication can be discharged into water bodies, which result in deterioration of surface water quality andpose a high potential risk to the public health.An integrated modeling system was developed and applied to simulate the pesticide losses fromagricultural land and assess the risks of pesticide pollution on the public health within the watershedsystems. Based on the pesticide transport properties, a pesticide loss model (PeLM), combined with thedistributed hydrological model and soil leach model, is employed to estimate the pesticide losses throughsurface runoff. Various processes of pesticide transport in the environment were considered. Theseprocesses include emission from soil as well as chemical, biological and photo degradation, dissolutionfrom granule into water, adsorption/desorption, runoff, and leaching. The GIS and database techniqueswere combined into the modeling frame to tackle with the data management and results representation.Furthermore, a hybrid risk assessment model was proposed to evaluate the preliminary and site-specificenvironment risks based on the simulation results. An exposure dose model was incorporated into thefuzzy risk assessment approach to achieve an integrated risk level of pesticide for the target location. Theexposure assessment process was conducted to quantitatively and qualitatively evaluate the exposure tovarious hazardous contaminants. It describes the intensity, frequency, and duration of contact, and oftenevaluates the rates at which the chemical crosses the boundary (chemical intake or uptake rates). Riskcharacterization was performed, which is the summation of the data compiled in the risk assessmentprocess including the uncertainties associated with each stage and the presentation of a risk estimate. Aset of membership functions was set up according to the properties of pesticides and related criteria. Acase study was conducted for verifying the proposed model. The study area is the Thames River Basin,southern Ontario, where pesticide pollution was founded since 1980's. Atrazine, a widely used herbicide,was selected as the study target. The atrazine loss through surface runoff in the Thames River Basin waspredicted and the peak concentrations at the river mouth were determined. The risk impacts on the localhuman health were analyzed and evaluated. The study results and the related recommendations providevaluable information for supporting decision of pesticide management and pollution control.