Author(s)

N. Z. Jovanovic & C. Petersen

Abstract

Agriculture is one of the main sources of non-point source (NPS) pollution in South Africa. Research was therefore initiated on the development of an integrated modelling framework for prediction of agricultural NPS pollution from field to catchment scale. In that context, an Excel-based Pesticide Environmental indeX (PestEX) was developed that accounts for the main factors affecting mobility of pesticides and their potential for landing up in a water resource. A tiered approach was used to combine these factors based on their level of occurrence, namely local scale (pesticide drift; position of application in relation to streams and groundwater; general slope of the area; presence of impervious layers in soils and dominant flow direction; tillage practices; soil hydraulic properties; the impact of irrigation practices/rainfall distribution via overland flow and deep percolation; the presence of anti-erosion contours), catchment scale (pesticide properties like sorption, volatilization and decay; the presence of wetlands/buffer strips) and overarching level (pesticide application; sensitivity of the receiving environment). Each of these factors is assigned a rating (using fuzzy logic for numerical variables) and weighting to produce a pesticide mobility score. The normalized score allows comparison and minimization of environmental and pollution abatement costs. The PestEX calculator was demonstrated using data from an experimental site in the Western Cape (South Africa), where methomyl and tebuconazole were applied to dryland wheat, and their mobility to water bodies was scored. Potential users of this tool are the scientific community, farmers, pesticide consultants and the regulatory authority. Possible applications are in comparative analyses of environmental and pollution abatement costs of different chemicals for regulatory or marketing purposes, sensitivity analyses to assess the effects of different mitigation/

Keywords

environmental cost, environmental mobility, fuzzy logic, index, mitigation measures, non-point source pollution, pesticides, pollution abatement cost, water resources