Influence of the Southeast Asian biomass burnings on the atmospheric persistent organic pollutants observed at near sources and receptor site

Persistent organic pollutants (POPs) such as PCDD/Fs, PCBs, PBDD/Fs, PBBs and PBDEs are bio-accumulative, toxic, and susceptible to long-range transport (LRT). This study is the first that comprehensively discusses the long-range atmospheric transport behavior of these five groups of POPs. The main goal is to investigate the atmospheric characteristics of these POPs at the biomass burning sites of Chiang Mai in Thailand, and Da Nang in Vietnam, as well as the influence of the Southeast Asian biomass burnings on the Lulin Atmospheric Background Station (LABS) in Taiwan. Biomass burning in Southeast Asia is usually carried to remove the residues of agricultural activities. The ambient air in Da Nang seems to be more seriously affected by the local biomass burnings than that in Chiang Mai. The elevated atmospheric brominated POP (PBDD/Fs, PBBs and PBDEs) concentrations in Da Nang were attributed to the biomass burning and viewed as mostly unrelated to the local use of brominated flame retardants. In the spring of 2010, the mean atmospheric concentrations in LABS during the first and second Intensive Observation Periods (IOPs) were 0.00428 and 0.00232 pg I-TEQ Nm−3 for PCDD/Fs, 0.000311 and 0.000282 pg WHO-TEQ m−3 for PCBs, 0.000379 and 0.000449 pg TEQ Nm−3 for total PBDD/Fs, 0.0208 and 0.0163 pg Nm−3 for total PBBs, and 109 and 18.2 pg Nm−3 for total PBDEs, respectively. These values represent the above concentrations due to the Southeast Asian biomass burnings. The affected atmospheric POP concentrations at the LABS were still at least one order lower than those in other atmospheric environments, except for the PBDE concentrations during the first IOP (109 pg Nm−3), which was surprisingly higher than those in Taiwanese metal complex areas (93.9 pg Nm−3) and urban areas (34.7 pg Nm−3). Atmospheric POP concentrations do not seem to dramatically decrease during long-range transport, and the reasons for this need to be further investigated.