Sedimentary records of organochlorine pesticides in the Taihu Lake

The vertical distributions of organochlorine pesticides (OCPs) were investigated in two sediments cores collected from the Taihu Lake. Sedimentary records of OCPs in this region were reconstructed using 210Pb activity profiles. The OCPs deposited in the sediment were mainly of DDTs, Meiling (ML) Bay sediment pollution was earlier and heavier than Xukou (XK) Bay. In the core profiles (0-28 cm), sedimentary DDTs concentrations in the ML bay and XK bay were 1.2-12.0 ng/g, 0.4-6.0 ng/g and HCHs were 0.4-9.0 ng/g, 0.4-2.7 ng/g, respectively. An initial increase in OCPs deposition was observed since the 1960s, followed by the first peak around 1970. Sedimentary OCPs amounts remained relatively constant in XK bay before 1990. In ML bay however, OCPs amounts displayed increase trend since the early 1980s, and decreased a little after the production ban of technical HCHs and DDTs imposed in China in 1983. Since the 1990s, sedimentary OCPs concentrations increased sharp in two bays, which related closely with the loss of arable-land around Taihu region. The remobilization of 'weathered' DDTs had contributed to the rebounds of OCPs in recent years, reflecting the effect of human activity to the aquatic environment.