Organochlorine pesticides in the sedimentary core of the southern Tibetan Plateau: The missing pieces induced by lateral remobilization

• Published in: Environmental pollution (1987) 2018-02, Vol.233, p.340-347
• Main Authors: Li, Jun, Yuan, Guo-Li, Duan, Xu-Chuan, Sun, Yong, Yu, Hong-Hui, Wang, Gen-Hou
• Format: Article
• Language: English
• Subjects: Atmospheric deposition; China; DDT - analysis; Endosulfan - analysis; Environmental Monitoring; Geologic Sediments - chemistry; Hydrocarbons, Chlorinated - analysis; Lakes - chemistry; Lateral remobilization; Lindane - analysis; Organochlorine pesticides; Pesticides - analysis; Sedimentary core; Soil; Tibet; Tibetan plateau
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2017.10.078

The sedimentary core in remote alpine lakes has been recognized as an ideal proxy to reconstruct the emission and air deposition histories of persistent organic pollutants (POPs). Nevertheless, POPs formerly stored in a catchment might also contribute to the variation in the lake sediment by lateral remobilization. In this study, to reveal the relative importance of lateral remobilization, we measured the vertical profiles and isomeric ratios of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and endosulfan in a dated sedimentary core collected from Lake Yamzho Yumco in the southern Tibetan Plateau. In addition to the flux peaks in the 1970s corresponding to the heavy atmospheric deposition of DDTs and HCHs, these pollutants’ fluxes displayed rebounds in the flood periods, with characteristic low ratios of DDT/DDE (α-/β-HCH). This might indicate a massive remobilization of “weathered” pesticides from catchment soil to the lake because of strong hydro-dynamics. Moreover, the relative contribution of lateral remobilization to the lake sediment in the past decades was recognized through the correlation between DDT/DDE (α-/β-HCH) ratios and ∑DDT (∑HCH) fluxes. The results showed that the lateral remobilization contributed to 20–42% of the total fluxes. This study discriminated the air deposition from the contribution of lateral remobilization, which improves current understanding of the vertical POPs profiles in the sedimentary core. [Display omitted] •A highly time-resolved record of OCPs was determined in a lake of the TP.•The contribution of atmospheric deposition was differentiated from that of lateral remobilization.•The remobilization of OCPs from catchment to Lake Yamzho Yumco was quantified.•OCP compositions were significantly influenced by remobilization dynamics. In the sedimentary core of the TP, the relative importance of lateral remobilization was identified for POPs, which was supported by the unique isomeric ratios.