Monitoring and Evaluation of Pesticide Residues in Aquatic Systems

Abstract

Pesticides are primarily used for crop protection in agriculture with global consumption of about two million tons per annum. Herbicides, insecticides, and fungicides are the major three classes of pesticides covering about 95% of the total pesticides use. Besides controlling the target pests, a large number of these pesticides adversely affect humans and other non-target organisms with acute and chronic toxic effects. Therefore, people who are professionally engaged in the process from pesticide production to application are most susceptible to various adverse health effects due to acute and chronic exposure. In addition, pesticides following application are circulated in various biotic and abiotic components of the environment including water. Moreover, a number of pesticides are persistent in the applied crops leading to residual toxicity in food. Consequently, the general population is also exposed to trace levels of pesticide residues through food and water. Therefore, regular monitoring of pesticide residues is indispensable for assessment of food and environmental safety.This chapter reviewed: (1) The processes facilitating distribution of pesticides from agro-ecosystem to hydro-system; (2) Analytical methods for monitoring of pesticide residue in water; (3) Status of pesticide residues occurring in aquatic system; (4) Reasons for frequent occurrence of organochlorine pesticides in water bodies; and (5) Methods for assessment of aquatic ecological risk due to pesticides. Following application in field, pesticides are transported to hydro-system through runoff, leaching and preferential water flow in dissolved and particulate phase. The multi residue methods based on chromatography with tandem mass spectrometry have been developed and validated for trace analysis of organic pollutants such as pesticides of diverse chemical classes in aquatic system. Over the past few decades, the residual level of various pesticides up to 5.7 μg/g level have been detected in aquatic system of different countries across the world. Most of the organochlorine pesticides, such as dichlorodiphenyltrichloroethane, hexachlorocyclohexane, and endosulfan failed to meet the guideline values, have been banned. The reasons for occurrence of banned organochlorine pesticides are attributed to: (i) the old sources and their transformation into stable isomeric products, (ii) sedimentation succeeded by re-suspension to release organochlorine pesticides; and also due to (iii) the continued use of the banned organochlorine pesticides to combat vector borne diseases. Potential risks to aquatic life are also evaluated by computing risk quotient, toxic unit, and various risk models for hazard analyses. Leaching potentiality of pesticides to pollute groundwater may also be evaluated using groundwater ubiquity score index. Social awareness, safe and judicious use of toxic pesticides, use of bio-pesticides, designing strict policies and effective remediation technologies are recommended to minimize the pesticide pollution in aquatic system.