Wet Deposition of Polychlorinated Dibenzo-p-dioxins/Dibenzofuran in a Rural Area of Taiwan

The annual variations of wet deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in atmosphere were measured at two sites (A and B) near two municipal solid waste incinerators (MSWIs) in southern Taiwan. Results showed that particle scavenging dominates in the wet deposition processes for the removal of PCDD/Fs from the atmosphere, the highest value was observed at the highest chlorinated congener. The ambient temperature and the amount of precipitation played an important role in the variation of PCDD/F deposition fluxes. It was found that temperature was inversely associated with the existence of particulate PCDD/Fs, indicating PCDD/Fs are scavenged most efficiently in cold weather. PCDD/F wet deposition fluxes in rainy seasons (from June to August) were significantly higher than those in dry seasons (from December to February), revealing a positive relationship between wet deposition flux and monthly rainfall. Additionally, the annual total (dry + wet) deposition fluxes of PCDD/Fs were 149 ng/m-year (5.02 ng I-TEQ/m-year) and 177 ng/m-year (5.11 ng ITEQ/m-year) for sites A and B, respectively, revealing that dry deposition was more dominant than the wet deposition for the atmospheric deposition of PCDD/Fs. Since atmosphere deposition is believed to be the main transfer pathway of PCDD/Fs into food chains, its impact on human exposure to PCDD/Fs is of great importance.