Evaluation of pesticide impact rating index (PIRI) model as a pesticide risk indicator

Abstract

Systematic methods for assessment of potential risk of pesticides to the environment can be consideredas valuable tools in decision-making and policy formulation. Pesticide Impact Rating Index (PIRI) isa user-friendly simple risk indicator and it can be used to rank pesticides in terms of their mobility. Thepredictions given by using PIRI for the pollution potential of pesticides on shallow ground waterbodies of Kalpitiya area in Sri Lanka was compared with the field experiments. Cultivated areas ofKalpitiya peninsula were selected for field trials.

Oxytluorfen for onions, Chlorpyrifos, Diazinon, Dimethoate, Carbofuran, Carbaryl, Mcthornyl,Irnidacloprid, Fenthion and Captan for chili were applied in replicates at recommended applicationrates for particular crops. Each area was irrigated at the rate of 20 mm/day. The soil considered wasthe sandy soil with the organic matter of 1.6±0.2%. Residue levels of applied pesticides were measuredusing Gas Chromatographic and High Performance Liquid Chromatographi methods in irrigation wellsin 100 m diameter area at 3 m depth for 3 months in one week intervals from the time of pesticideapplication. The detected pesticides were confirmed using Gas Chromatographic MassSpectrophotometric method.

Out of applied pesticides, Dirnethoate, Carbofuran, and Chlorpyrifos leached 3 m water table in 24±4days, 25±3 days and 3 5±6 days respectively after application of each pesticide. The field monitoringresults were 74% compatible with the predictions from PIRI. This indicates that PIRI can be used asa simple risk indicator model for the prediction of pesticide risk to water bodies.