BEHAVIOUR OF ENDOSULFAN AND LINDANE DURING SEDIMENT ELUTRIATE AND WATER SPIKE TOXICITY TESTS UNDER SALINE CONDITIONS

Potential exposure to chemicals in the ecosystem can be predicted from a set of physicochemical analyses conducted for mobility and degradation. Standard elutriate toxicity tests proposed at 1:4 (v/v) of undisturbed sediment be mixed with water has been validated to be used as a conservative predictor of dredging site dissolved chemical concentrations. Sediment samples obtained from the Chantaburi estuary were spiked with endosulfan and lindane and subjected to elutriate process under 16‰ salinity. The average dissolution potential was as low as 0.23% for endosulfan and 1.84% for lindane indicating strong affinity for hydrophobic contaminants in the Chantaburi estuary sediment. The relationship of dose dependent endosulfan and lindane dissolution in sediment showed gradual decrease of dissolution as the spiked concentration of sediment increased, indicating mass action effect on hystresis sites. The negative non-linear power regression indicated a better relationship and the coefficients of determination (R 2 ) for endosulfan and lindane were 0.97 and 0.87, respectively. This indicated that dissolution of endosulfan and lindane into the water column from Chantaburi estuary sediment was minimal. The results of this study confirmed that after vigorous resuspension event of sediment (= elutriate), α-endosulfan was the dominant fraction followed by β-endosulfan and endosulfan sulfate in order to cause biological effects. In contrast to elutriates, endosulfan compounds measured in seawater after 96 h spiking were biased towards β-endosulfan compared to α-endosulfan indicating preferential loss of αendosulfan, thus lowering the true potential in the water column. The mean total endosulfan and lindane concentrations remained in toxicity test matrices at 96 h were 7.52% and 15.54%, respectively. Some of the possible explanations for this finding could be due to possible loss of toxicants through volatilization and/or adsorption to the exposure vessels.