Assessment of Pesticide Contamination in Ground Water from Intensive Agricultural Sites, Using Gas Chromatography-Mass Spectrometry.

A methodology proposed by US EPA (8081-B) is adopted with some modifications for low level pesticide residue analysis in ground water samples. The method is based on liquid-liquid extraction and gas chromatography with electron capture detector (GC-ECD), and confirmed by gas chromatography-mass spectrometry (GC-MS). For this study, different classes of pesticides were selected, both recent and old persistent molecules, namely organochlorine and pyrethroid insecticides. Pesticide residues could be detected in the low- to sub-ppb range (0.5 ppb and below) with good precision (0.071-0.12%, average 0.06-0.71% R.S.D.) and extraction efficiency (78-93%) for the majority of analytes. This methodology has been applied in a monitoring program of water samples from an intensive agricultural area in five districts of Maharashtra (India). The pesticides detected in the two-year sampling program (2008/2009) were Alpha HCH, Beta HCH, lindane, Delta HCH, p,p'-DDE, o'p-DDD, Alpha Endosulphan, Beta Endosulphan and endosulfan sulphate. A survey of the type of pesticides being used in the area, along with the crop pattern, has also been done. The outcome of the study would be useful in predicting the pathway of pesticides from agricultural field to consumer end, and persistence of pesticides in the water bodies.