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

Abstract

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 -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.

Atmospheric Deposition Modeling of Polychlorinated Dibenzo-p-dioxins, Dibenzofurans and Polychlorinated Biphenyls in the Ambient Air of Southern Taiwan. Part II. Wet Depositions and Total Deposition Fluxes

“…The highest level of φ for SVOCs was observed in winter, while the lowest one can be found in summer (Huang, 2011b). Consequently, SVOCs are expected to be scavenged most efficiently in cold weather (Huang, 2011b). Furthermore, the values of S tot increased with the substituted number of chlorine rising, which is according to the observations of gas-particle partitioning of SVOCs in atmosphere (Huang, 2011a, b).…”

“…Furthermore, ambient temperature also affects the gas particle distribution of SVOCs. The total PCDD/Fs and PCBs bound to particles increased with decreasing temperature, as the previous study shows (Koester and Hltes, 1992;Mandalakis and Stephanou, 2004;McLachlan and Sellström, 2009;Huang, 2011b). The highest level of φ for SVOCs was observed in winter, while the lowest one can be found in summer (Huang, 2011b).…”

“…Wet deposition is the removal of particles in atmosphere by precipitation (rainfall and cloud droplets) and precipitation scavenging accounts for the majority of removing SVOCs from atmosphere by wet deposition (Huang, 2011b). Wet deposition flux of SVOCs is a combination of both vapor dissolution into rain and removal of suspended particulates by precipitation (Bidleman, 1988;Koester and Hltes, 1992).…”

Atmospheric Deposition of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Two Cities of Southern China

“…The annual rainfall was 1091.1 mm in Nanjing, and was strongest in July (263.5 mm) and August (158.8 (Tseng et al, 2014). The amount of precipitation in Nanjing was less than that in Guangzhou, but the amount of wet deposition was similar, thus demonstrating that wet deposition is not only affected by rainfall, but also by factors such as particulate matter concentration, temperature, and wind speed (Wang et al, 2010;Huang et al, 2011b).…”

“…Wet deposition is the removal of particles in the atmosphere by precipitation (rainfall and cloud droplets), and precipitation scavenging accounts for the majority of removing PCDD/Fs from the atmosphere by wet deposition (Huang, 2011b). Wet deposition flux of PCDD/Fs is a combination of both vapor dissolution into rain and removal of suspended particulates by precipitation (Bidleman, 1988;Koester and Hites, 1992).…”