Sedimentary records of historical occurrence and sources of 21 organochlorine pesticides in Lake Taihu, China

Abstract

PURPOSE: Sediments are natural archives to record the occurrence and sources of organochlorine pesticides (OCPs). Most previous studies on historical occurrence and sources of OCPs in China only focused on DDTs and HCHs. Comprehensive knowledge of historical occurrence and sources of persistent OCPs in China are scarce. MATERIALS AND METHODS: One 20-cm sediment core was collected from the third largest freshwater lake (Lake Taihu) in China, then sliced every 1 cm, dated with ¹³⁷Cs and ²¹⁰Pb, and used for the analysis of 21 OCPs. Isomer ratios and principal component analysis (PCA) were applied to apportion the historical sources of the OCPs in this lake. RESULTS AND DISCUSSION: Three concentration peaks of OCPs were observed in the middle-late 1950s, early-middle 1980s, and the middle 2000s. The average concentration of ΣDDX was 238.55 ± 55.43 ng gdw⁻¹ from 1948 to 2012. p,p′-DDT was the dominant congener of DDX, mostly derived from the legacy technical DDT. The average concentration of ΣHCHs, aldrin, heptachlor epoxide, endosulfan sulfate, methoxychlor, heptachlor, trans-chlordane, cis-chlordane, endosulfan I, endrin, diendrin, endosulfan II, diendrin aldehydrate, and diendrin ketone were 24.56 ± 6.90, 10.35 ± 3.26, 9.51 ± 1.88, 7.37 ± 1.81, 7.01 ± 2.82, 2.60 ± 0.81, 0.63 ± 0.24, 3.21 ± 1.25, 1.04 ± 0.29, 3.89 ± 2.61, 5.67 ± 1.59, 1.07 ± 0.19, 1.09 ± 0.22, and 1.32 ± 0.33 ng gdw⁻¹. CONCLUSIONS: Dicofol and p,p′-DDT-containing anti-fouling paints may be responsible for the current input of p,p′-DDT. Most of the HCHs were derived from the legacy technical HCHs, but there was input of lindane as well. PCA indicated that the legacy technical DDTs, HCHs, heptachlor, chlordane, aldrin, and endrin, the current input of p,p′-DDT, methoxychlor, and endosulfan, and microbial transform of γ-HCH to α-HCH were the dominant sources for the 21 OCPs in Lake Taihu.