High-resolution sedimentary records of some organochlorine pesticides in Yamzho Yumco Lake of the Tibetan Plateau: Concentration and composition

Sediment cores from lakes have been used to reconstruct the historic deposition of persistent organic pollutants (POPs), especially in remote alpine areas. To reconstruct the deposition history of organochlorine pesticides (OCPs) in the Tibetan Plateau (TP), two sediment cores from Yamzho Yumco Lake were drilled and dated with high-resolution, from which 23 OCPs were analyzed in greater detail. Regarding several legacy compounds, concentration peaks in the cores were observed in the 1970s, corresponding to the heavy usage of these compounds around the world. In addition, another peak was found at the end of the 1990s, which was explained as the addition of OCPs released from melting glaciers or the cryosphere due to global warming. Furthermore, it was found that the transformation or degradation of OCPs after deposition in the lake was limited by comparing the values of isomeric ratios at different times, such as (DDD+DDE)Sigma DDTs, o,p'-DDT/p,p'-DDT and beta-HCH/Sigma HCHs. Such results ensure that the detected OCPs in the lake sediments really reflect their characteristics at the time of deposition. On the other hand, weak environmental self-purification of the OCPs made them last longer in the TP than in other regions. Reasonably, the fragile ecological environment of the TP would be threatened not only by legacy POPs that remain in the sediments and soils but also by POPs released from melting glaciers or the cryosphere in the next few decades under the influence of global warming. Our research provides an insight into the influence of global warming and glacial melting on the environment of the TP, and further work to gain a better understanding of the environmental processes of POPs in the TP is ongoing. (C) 2017 Elsevier B.V. All rights reserved