Organochlorine pesticides,polybrominated biphenyl ethers and lead isotopes during the spring time at the Waliguan Baseline Observatory,northwest China: Implication for long-range atmospheric transport

Located in the center of the Asian continent, the Waliguan Baseline Observatory (WBO) is the highest and the most inland Global Atmospheric Watch (GAW) station in the world. In the present study, organochlorine pesticides (OCPs) and polybrominated biphenyl (PBDEs) were analyzed in the daily collected samples at the WBO from 2 April to 23 May 2005, in an attempt to investigate the long-range atmospheric transport (LRAT) of persistent organic pollutants (POPs) in northwest China. The mean concentrations of OCPs at WBO were slightly higher than the Arctic regions, and the concentrations of total PBDEs (8.3±4.0 pg m^?3) was comparable with other remote areas. The low temperature dependence of the POP concentrations in the air, and the absence of local use of these compounds implied LRAT to WBO. As suggested by backward air trajectory analysis, the high concentrations of γ-HCH, DDTs and PBDEs, during the sampled spring period, were mainly related to air mass passing over the neighboring countries (e.g., Russia, Kazakhstan). Additional evidence was also obtained by the lead isotopic composition analysis, which showed similar ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios as those of ores in these countries. The present results indicate that the WBO may serve as an excellent GAW station for monitoring the LRAT of POPs in the Asian continent.