Evaluation of atmospheric PCDD/Fs at two high-altitude stations in Vietnam and Taiwan during southeast Asia biomass burning

Dioxin and dioxin-like compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are persistent organic pollutants (POPs) generated through human activities. In recent times, extreme weather events such as wild fires have significantly affected the remobilization and successive bioavailability of PCDD/Fs. In Seven South East Asian Studies (7-SEAS), a Southeast Asia biomass burning event that influenced the environmental outcome and transport of PCDD/Fs in Taiwan was investigated on the basis of a climate change situation. During the 7-SEAS campaign on 20–28 March, 2011, significantly high levels of atmospheric PCDD/Fs were observed at Lulin mountain in central Taiwan and in the source region of Northern Vietnam (Son La). Measurements indicated that the patterns of variation of atmospheric PCDD/Fs at both locations were similar, but with a time lag of approximately 2 to 3 days. At Mt. Lulin, there was a significant increase of PCDD/F concentrations from 3.69 to 11.1 fg I-TEQ m^–3 and 3.32 to 19.1 fg I-TEQ m^–3 to reach their peaks on 23 March and 26 March. In this study, a tracer simulation using the Weather Research and Forecasting model coupled with chemistry was conducted to investigate the effects of the Southeast Asia biomass burning. The combined results of air mass paths simulation and satellite data can be used as evidence supporting the hypothesis that the source of the increasing PCDD/F level is originated from biomass-burning regions in Indochina, particularly Northern Vietnam and Northern Thailand.