Atmospheric Deposition of Polychlorinated Dibenzo-p-dioxins/ Dibenzofurans in the Ambient Air at the Mountain Yangming

• Main Authors: Chun-WeiTu, 杜俊緯
• Other Authors: Ta-Chang Lin
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/kxufc3

碩士 === 國立成功大學 === 環境工程學系 === 104 === Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are carcinogenic persistent organic pollutants (POPs) that can bioaccumulate in the ecosystem, cause endocrines disruption and undergo long range transport in the atmosphere. Atmospheric deposition including those of dry and wet is a primary pathway for the transfer of POPs to terrestrial and aquatic ecosystems. In this study, the characteristics of PCDD/Fs in the ambient air at Mt. Yangming were simulated by the PM10 versus PCDD/Fs concentration regression analysis, gas-particle partition modeling, dry deposition, and wet deposition simulations. Dry and wet deposition fluxes were obtained from the combination of the PCDD/F concentrations, meteorological information, dry deposition velocities, and scavenging ratios. The dry deposition fluxes of PCDD/F-WHO2005-TEQ increase with decreasing temperature, while increase with higher degree of chlorine numbers on PCDD/F homologues. However, a wet deposition flux increase with stronger rainfall intensity. The congener profile of PCDD/F-WHO2005-TEQ indicates that total deposition fluxes, 2,3,4,6,7,8-HxCDF, 2,3,4,7,8-PeCDF dominate the deposition fluxes. The simulated PCDD/F concentration during 2014, at Yangming, ranged between 0.00725 and 0.0176 pg WHO2005-TEQ /Nm3, while those during 2015 ranged between 0.00761 and 0.0162 pg WHO2005-TEQ /Nm3. WHO2005-TEQ ratios of PCDDs to PCDFs at both year are all less than 1 (averaged 0.407), indicating that PCDF dominate the total toxicity. During 2014, at Yangming, the monthly dry deposition flux of total PCDD/Fs-WHO2005-TEQ ranged between 9.63 and 91.7 pg WHO2005-TEQ /m2 ∙month, while those during 2015 ranged between 12.2 and 61.0 pg WHO2005-TEQ /m2 ∙month. At the other hand, during 2014, at Yangming, the monthly wet deposition flux of total PCDD/Fs-WHO2005-TEQ ranged between 6.29 and 138.3 pg WHO2005-TEQ /m2 ∙month, while those during 2015 ranged between 4.95 and 79.3 pg WHO2005-TEQ /m2 ∙month. The annual total wet deposition flux of total PCDD/Fs- WHO2005-TEQ concentration at Yangming were 637.3 and 511.1 pg WHO2005-TEQ /m2 ∙year in 2014 and 2015, respectively. During 2014, at Yangming, the monthly total deposition flux of total (dry + wet) PCDD/Fs-WHO2005-TEQ ranged between 34.4 and 178.0 pg WHO2005-TEQ /m2 ∙month, while those during 2015 ranged between 28.1 and 119.1 pg WHO2005-TEQ /m2 ∙month. The annual total deposition flux of total PCDD/Fs-WHO2005-TEQ at Yangming were 969.7 and 803.6 pg WHO2005-TEQ /m2 ∙year in 2014 and 2015, respectively. At Yangming, during 2014, the fraction contribute by dry deposition ranged between 10.9% and 81.7%, while during 2015 ranged between 16.4% and 82.4%. Mean fraction contribute by dry deposition at Yangming were 35.7% and 39.2% in 2014 and 2015, respectively. The lowest fraction of individual PCDD/Fs dry deposition in total (dry + wet) deposition fluxes was found in fall in both years. It may be due to high rainfall intensity occurred in fall and also the day with precipitation were more in fall. The simulated results of this study combine with the previous measured data provided useful information for the future policy making and further studies. In Taiwan, more measured data associated with dry deposition velocity and wet scavenging is needed for a more precise and complete investigation in the future.