Evaluation of Dry/Wet Deposition of PCDD/Fs in Northern Taiwan via Automated and Traditional Samplers

• Main Authors: Kung-ting Liu, 劉恭廷
• Other Authors: Moo-been Chang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/56200069732834950955

碩士 === 國立中央大學 === 環境工程研究所 === 96 === PCDD/Fs emitted to atmosphere may eventually fall to water body or environment during atmospheric diffusion and impact human health. Dioxin is a substance of high boiling point and is adsorbed enormously on the solid phase in environment and the particles become its main transportation media. Therefore, monitoring the atmospheric deposition of particles may provide the information regarding the extent of its PCDD/F effects on water body and people’s health. This study focuses on the understanding of the dry/wet deposition of PCDD/Fs in northern Taiwan via automated and traditional samplers. The main advantages of this method include: (1) obtaining more accurate data regarding deposition flux of PCDD/Fs from atmosphere to land; (2) the combination of two types of samplers can help to clarify the possible under-estimation of deposition flux achieved with the traditional samplers. In addition, the deposition velocity and scavenging ratio during sampling process are also calculated so that we may find out how efficient PCDD/Fs falls on to the surface receptor in northern Taiwan and the removal efficiency of PCDD/Fs while raining. The deposition flux of PCDD/Fs collected by traditional sampler ranged from 54- 220 pg/m2-day (2.0-9.9 pg TEQ/m2-day), while the deposition flux of PCDD/Fs collected by automated sampler was much higher, ranging from 239-490 pg/m2-day (15.0-25.8 pg TEQ/m2-day). Furthermore, the relative difference of PCDD/F deposition flux between the measurement of automated and traditional samplers increased with increasing atmospheric temperature. It is also interesting to find the relative difference of lowly chlorinated PCDD/Fs were higher than that of highly chlorinated PCDD/Fs. This study also investigates the influences of dry/wet deposition on sampling time and rainfall. The results indicate that wet deposition flux was higher than dry deposition flux. Dry deposition flux was measured as 149-224 pg/m2-sunny day (11.1-16.5 pg TEQ/m2-sunny day) while wet deposition flux was 690-10100 pg/m2-rainy day (36.8-228 pg TEQ/m2-rainy day). As indicated by this finding, wet deposition can remove PCDD/Fs in a more significant way than dry deposition. Furthermore, the average PCDD/Fs deposition velocity and scavenging ratio in northern Taiwan are calculated as 0.26 cm/s and is 1.4×105, respectively.