Chlorpyrifos is an organophosphate insecticide widely used in India for urban and domestic pest control, and as a termiticidal control in foundations of buildings, household as well as in agricultural settings. It is used erratically by pest controllers in foundations around buildings, yards, crevices through drilling, spraying etc. While it is recommended at 1 L/m2of 20% EC formulation by BIS in different stages of treatment in foundations for household practices. In agricultural practices, farmers use chlorpyrifos arbitrarily, most likely due to ignorance or out of concern that pesticide formulations have been adulterated and may not actually have the labeled amounts of active ingredient. This overuse leads to severe contamination of the soil, possibly endangering groundwater and additionally the resultant agricultural produce may carry high pesticide residues. In view of large application of chlorpyrifos, an attempt has been made to study the leaching of chlorpyrifos in neutral and acidic soil for risk assessment of groundwater contamination and assessment of dose for chlorpyrifos treatment according to the pH of the soil. Open top lysimeters were installed for neutral and acidic soil. Field conditions were simulated in the lysimeters by putting gravel and pebbles at the bottom, and deposition of soil profile above it as collected from the field at three different depth levels. A constant head of water was maintained in levels representative of annual rainfall. Leachate samples were collected at regular intervals. After extraction and clean up, analysis of the leachate samples was carried out with 7820 A GC. Leaching of Chlorpyrifos for single and double dose treatment was found to be 37.74% and 85.16%, respectively in neutral soil and 51.52% and 91.15%, respectively in acidic soil. Leaching was found to be significantly higher in acidic soil, compared with neutral soil indicating higher possibility of groundwater contamination in acidic soil.

Risk assessment of groundwater contamination by chlorpyrifos through lysimetric studies in neutral and acidic soil

246th National Meeting (2013)

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