Atmospheric PM2.5 and Depositions of polychlorinated dibenzo-P-dioxins and dibenzofurans in Taitung County, Taiwan.

• Main Authors: JustusMutuku, 張克平
• Other Authors: Wen Jhy Lee
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/mbtexh

碩士 === 國立成功大學 === 環境工程學系 === 105 === Taitung lies on the South East side of Taiwan; geographically, it mostly consists of mountains and a coastal stretch. It has a tropical monsoon climate, the wet season runs from May to October, while the dry season runs from November to April. The region has a high humidity and its annual average temperature ranges from 22 to 25 0C. The tropical climate in Taitung region is different in the sense that it is more foggy than sunny. The main economic activities in Taitung are farming and tourism. Because of its sparse population, lack of urbanization and industrialization, Taitung County has managed to remain a pollution free zone compared to other regions of Taiwan. As a result, it has been left out on most of the studies on air pollution in Taiwan. This study focused on the roles of meteorological factors to the ambient air concentrations and depositions of Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) and particulate matters (PM2.5) in Taitung County, Taiwan. Wet and dry depositions of dioxins in the region were also quantified. The average annual PM2.5 concentrations ranged between 9.6 to 11.0 μg m-3. Taiwan applies the 2012 PM2.5 world air quality index as its standard for the EPA which is currently at 15 µg m–3. According to these standards, Taitung County did not exceed the set limits for the concentration of PM2.5 in ambient air for the entire study period. However, Guanshan station (11 µg m–3) had a higher concentration of PM2.5 compared to Taitung station (9.6 µg m–3). To quantify the concentration of dioxins in the atmosphere in Taitung County, Taiwan, a regression line relating the mass concentration of PCDDs/Fs to PM10 was plotted. Compared to other studies, the concentration of dioxins in Taitung County was lower than the other regions in Taiwan. The simulated concentration of dioxins in the atmosphere ranged between 0.0106 to 0.0117 pg WHO 2005-TEQ m–3. There was an upward trend in the concentration of the dioxins for the two years in the entire area of study concentrations in 2014 was 0.0106 while the concentration in 2015 was 0.0115 pg WHO 2005-TEQ m–3 . Temperature and atmospheric pressure were used to model the partitioning of dioxins into their gaseous and particulate phases for the four seasons of the year. Higher chlorinated dioxins (hexa-, hepta- and octa-chlorinated) were the dominant congeners in the particulate phase while the low chlorinated congeners (tetra- and penta-chlorinated dioxins) existed almost wholly in their gaseous phase. Total deposition in the Taitung County ranged between 58.2 and 189.5 pg WHO2005-TEQ m-2 month-1. Dry deposition was dominant in region compared to wet deposition and it ranged between 35.7 to 188.5 pg WHO2005-TEQ m-2 month-1 with the dry deposition velocities ranging between 0.17 and 0.52 cms-1. The average dry deposition velocity was 0.39 cms-1. Wet deposition was dependent on the number of days experiencing precipitation and it ranged between 0.39 to 30.3 pg WHO2005-TEQ m-2 month-1. The range of the scavenging ratios was between 1351 and 41197 for the entire study period.