Delhi is capital of India and is one of the most populated cities with 12,886 hectare areas of farming, providing greenery to the city but the fate of agrochemicals used is not known. A study was undertaken to know the pesticide residues in the Yamuna River flowing near the farming area by surface runoff and also in the groundwater by leaching. Groundwater samples were collected from eight tubewells of different vegetable crops. Organochlorine pesticides analysed were a-HCH, �-HCH, ?-HCH, d-HCH, endosulfan-I, endosulfan-II, endosulfansulfate, dicofol, p,p'-DDE and p,p'-DDT and their residues ranged from 0.005 - 10.72 �g/L and 0.005 - 1.440 �g/L in surface and groundwater samples. Organophosphate pesticides analysed were phorate, dimethoate, phosphamedion, methyl parathion, malathion, chlorpyriphos, quinalaphos, profenophos, and ethion and residues ranged from 0.007 - 2.707 �g/L and 0.004 - 39.6 �g/L in surface and groundwater samples, respectively. However, all the synthetic pyrethroids analysed (�-cyfluthrin, fenpropathrin, lemda cyhalothrin, a-cypermethrin, deltamethrin, fenvelerate) were found Below Detectable Limit (BDL). While the herbicide analysed were alachlor, fluchloralin, butachlor, and pendimethalin; residues ranged from 0.030 - 1.756 �g/L and 0.030 - 0.464 �g/L in surface and groundwater samples, respectively. It has been observed that even the banned pesticides like DDT, BHC, and endosulfan were found above MRL value. Their presence in water bodies is either due to their long persistence or their use is continued in the form of adulterated pesticides. In another lysimeter study, leachate from unlined drain samples collected near above farming areas did not show presence of pesticide residues, but certain parameters like calcium hardness, total hardness, total dissolved solids, nitrite, nitrate, electrical conductivity, and heavy metals were found to be present much above the WHO permissible limits. Rigorous extension services and strict enforcement and regulation are required to monitor the pesticide usage and promote Integrated Pest Management techniques (IPM) and switching to new safe molecules like synthetic pyrethroids.

Pesticide residues in surface and groundwater of Delhi near farming area

248th National Meeting (2014)

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