Concentration of Organochlorine Pesticides in the Chao Phraya River, Thailand.

Abstract

Water samples from the Chao Phraya River, the main river in Thailand, were collected and analyzed during 1988-1995. The Organochlorine pesticides such as HCHs, DDTs, aldrin, dieldrin and chlordanes were determined. Aldrin and dieldrin occured frequently in water samples. The medians of concentrations of pesticides were approximately one order of magnitude higher than total HCHs and DDTs. Levels of aldrin were relatively high in the upstream while levels of DDTs were high in the urban area of Bangkok during 1989-1990. p, p'DDE levels were relatively high in 1992. Relatively high levels of endosulfan sulfate were frequently found in lower part of the river in 1995. The trends of the residue level of pesticides found were fluctuated along the river.