PERSISTENT ORGANOCHLORINE RESIDUES IN FISH SAMPLES COLLECTED FROM THAMIRABHARANI RIVER

This study was undertaken to investigate the levels of organochlorine pesticides (OCPs) in surface water and sediments of the Thamirabarani river system, Southern India. Samples were collected from five sampling sites, viz, Papanasam, Vannarapettai, Srivaikuntam, Cheranmadevi and Punnakayal, and tested for OCPs by gas chromatography-Electron capture detector (GC-ECD) following QuEChERS extraction procedure. Fishes such as catla, rohu, tilapia, mackerel and sardine were collected from the sampling sites.  The GC recoveries of spiked samples were between 80 to 96%. 17 organochlorines (OCs) namely alpha-HCH, gamma-HCH, delta-HCH, heptachlor, heptachlorepoxide, endosulfan I, endosulfan II, endosulfan sulphate, p,p'-DDE, pp' DDD, pp' DDT, dieldrin, aldrin endrin, endrin-aldehyde, methoxychlor and methoxychlor epoxide were identified and quantified. A 100% incidence was recorded for gamma-HCH, delta-HCH, heptachlor, aldrin, gamma-chlordane, alpha-endosulfan, dieldrin and p,p'-DDT, while 75% incidence was recorded for the metabolites, p,p'-DDE and endosulfan-sulfate. The concentrations of OCs ranged from 0.3 to 71.3 µg/kg and were however, below the Australian Maximum Residue Limits (MRL) of 50 to 1000 µg/kg for fresh water fish. The occurrence of OCPs in fish muscle tissues ranged from 0.001 to 24.02 µg kg^-1, and this was comparatively lower than their presence in water and sediment. The most abundant OCPs were endosulfan (0.57 to 20.23 µg kg^-1) and endrin (0.32 to 6.89 µg kg^-1). Endrin concentration ranged between 0.58 to 5.70 µg kg^-1 with more accumulation recorded in rohu. The distribution pattern of DDTs,

HCH, endosulfan and other OCPs in the present study shows heterogenic nature of nonpoint source of pollution.