Distribution and source of organochlorine pesticides (OCPs) in the sediments of Poyang Lake

The concentrations of typical organochlorine pesticides (OCPs) (DDTs, HCHs, PCP-Na, and HCB) were measured to understand distribution and source of OCPs in surface and columnar sediments of Poyang Lake in 2006. And OCPS concentrations in surface sediment in 2017 were made a comparison with those in 2006 at several same sampling sites. OCPs showed higher concentrations in main stream than in river mouths (entrance of river flow into lake) of the lake. The average concentrations of HCHs and DDTs were 4.63 ± 3.86 and 20.15 ± 26.86 ng/g in surface sediments in 2006, respectively. Concentrations of OCPs in 2017 were lower than in 2006, such as HCHs average 1.98 ± 2.04 ng/g and DDTs average 4.87 ± 1.48 ng/g in 2017, indicating historical residual and degradation. The primary isomers of HCHs and DDTs in the lake were α-HCH, γ-HCH and p,p′-DDD, respectively. HCHs were from historical residual and lindane application. DDTs were from historical residual. PCP-Na total concentrations in surface sediment were 77.36 ng/g in 2006 and 44.04 ng/g in 2017. The concentration of HCB residues in surface sediment was 0.92 ± 0.90 ng/g in 2006 and 0.42 ± 0.38 ng/g in 2017. The concentrations of OCPs in columnar sediments showed annual variations, and the peak concentrations occurred in 1953, 1961, 1974, 1982, and 1995, showing close relations with onset of production OCPs pesticide in 1950s and its later prohibition in 1980s and a large number agricultural cultivated land decrease in 1990s in China. The concentrations of HCB in columnar sediments were average 2.33 ± 1.26 ng/g. OCPs of columnar sediments were from historical residues and lindane input. The main contamination of OCPs was PCP-Na and p,p′-DDD in Poyang Lake. On the whole, the combination of surface samples (0–5 cm in depth) and columnar samples (0–38 cm in depth) in a single study would give insight into OCPs pollution levels in different years (temporal resolution) and in different regions (spatial resolution) in Poyang Lake.