Variations of organochlorine pesticides and polychlorinated biphenyls in atmosphere of the Tibetan Plateau: Role of the monsoon system

Monsoon transport is an important process that influences the global transport of persistent organic pollutants. Only a few studies focused on the influence of monsoon on organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in the Tibetan Plateau. In this study, 19 samples were collected in Lhasa, the capital of Tibet Autonomous Region, using a high-volume air sampler. The average concentrations of α-HCH, γ-HCH, p-p′-DDT, p-p′-DDE, o-p′-DDT, α-endosulfan, β-endosulfan and PCBs (including PCB-28, 101, and 118) were 2.3, 10.3, 3.2, 2.9, 5.8, 6.3, 2.2, and 10.6 pg m^?3, respectively. The weak correlation coefficients between lnp (natural logarithm of partial pressure) and 1/T (reciprocal temperature) were obtained for DDTs and β-endosulfan (r² values ranged from 0.13 to 0.41). However, no significant correlations were obtained for HCHs and PCBs. These results suggested that both local emission and long-range atmospheric transport (monsoon) may influence the distribution of OCPs at Lhasa. In this study, peak concentrations of DDTs, endosulfans and PCBs were found in August, when Eastern Monsoon system occurred. However, the maximum concentrations of HCHs appeared in June (Indian Monsoon is the dominant air circulation pattern). Monthly variation of OCP/PCB levels was likely associated with the different air sources of monsoon system.