近年隨工業發展，人為排放至環境中的污染源日漸增加，因降雨為清除空氣污染物的重要途徑，本研究於台南成大地科系館頂樓架設採集氣溶膠與雨水採集裝置，研究雨水和大氣氣溶膠中的碳、氮與親顆粒性的Pb-210與Po-210的地球化學行為，以追蹤污染物於大氣中的遷徙與變化。過去由於氣溶膠採樣濾紙孔徑的限制，前人研究僅探討至0.1 μm的細微顆粒，為了解小於0.1 μm的奈米顆粒在空污中所佔的比重與重要性，本研究在濾紙採樣裝置的末端，添加曝氣採樣裝置，以捕捉小於0.1 μm的奈米級氣溶膠，同時利用不同孔徑的濾紙，採樣介於0.1 μm至2.7 μm的細顆粒與大於2.7 μm的粗顆粒。本研究發現奈米級氣溶膠在Po-210活度佔15 ~ 25%的比例，在Pb-210則佔5 ~ 35 %；前人著重研究的細顆粒則在Po-210和Pb-210中佔14 ~ 18% 與17 ~ 20%。由此可見，奈米級氣溶膠在空氣污染中有著不可忽視的貢獻。降雨頻繁發生時，會以清除細微與奈米級顆粒為主，其中又以奈米級顆粒為降雨最主要的清除對象。而整體的空氣品質也受到氣團來源的影響，冬季因東北季風帶來大陸氣團，使Po-210與Pb-210在雨水中的濃度，在冬季會高於夏季。本研究另外研究了2015年9月至2016年8月雨水中的碳與氮，研究大氣中的碳氮來源，發現汽機車排放的顆粒相的黑碳會富集人為排放的無機氮，使台南地區雨水碳氮比值常年小於自然界碳氮比的6.625，僅在梅雨季與夏季降雨頻繁時，雨水中的碳氮比會較接近於6.625，此研究結果顯示台南地區空氣品質長期為人為污染的狀態。這現象也反映在Po-210與Pb-210的比值計算出的滯留時間中，因Pb-210會較富集於可溶的無機物，而Po-210則較富集於不可溶的有機物上，這使降雨事件頻繁發生時，會洗下較多的Pb-210，使殘留在大氣中的Po-210/Pb-210比值升高，導致氣溶膠與雨水在滯留時間上有增加的趨勢。

With the development of the industry in the recent, the anthropogenic pollution from coal and fossil combustion is increasing, and rainfall is one of the main ways to scavenge the pollutants. We collected the rainwaters and aerosol particles on the top floor of NCKU’s Earth Science building, and analyzed their carbon, nitrogen, particle-attached Pb-210 and Po-210 to trace the changes and transport of air pollutants. Due to the limitation of filter’s pore size (0.1 μm), previous studies can only focus on the fine particle aerosols (> 0.1 μm). To understand the distribution and contribution of nano-particles which are smaller than 0.1 μm, we added water-trapping collector behind the air filters for sampling the nano-particles in this study, and sampled the fine particles (0.1 to 2.7 μm) and coarse particles (> 2.7 μm) at the same time. We obtain that the contribution of Po-210 and Pb-210’s activities are 11 to 28% and 3 to 33% in nano-particles respectively, and are 1 to 27% and are 2 to 32% in fine particles. The contribution of nano-particles cannot be neglected. When rain events occur frequently, the fine and nano-particles are the main parts removed by rainwater in the atmosphere, especially on nano-particles. The source of air mass also affects the air quality, for example, the east-northern wind is probably bringing pollutants with the continental air mass in the winter season. So it causes the activity of Po-210 and Pb-210 in the winter season higher than the summer season. We also studied the carbon and nitrogen in the rainwaters from Sep, 2015 to Aug, 2016. To trace the source of additional carbon and nitrogen, we notice that the black carbon emitted from cars and motorcycles can be attached with the anthropogenic inorganic nitrogen. This results the TC/TN ratio in rainwaters less than 6.6, which is the TC/TN ratio from natural organism, in almost the whole year. The TC/TN ratio is close to 6.6 in the plum rain season and summer season, when the rain event happened frequently. It shows the air of Tainan area is under anthropogenic pollution for long periods. Rain events also can influence the residence time calculated from the Po-210/Pb-210 ratio, because the Pb-210 tends to attach on the soluble inorganic materials, and Po-210 tends to attach on the insoluble organic materials. Since more Pb-210 is washed out during the frequent rain events, the Po-210/Pb-210 ratio increasing, and their residence time become longer.

1. ASHRAE standards committee. Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. Available: https://www.ashrae.org/File%20Library/Technical%20Resources/Standards%20and%20Guidelines/Standards%20Addenda/52_2_2007_Supplement_FINAL.pdf (2008).
2. Aycik, G. A. (Ed.). New techniques for the detection of nuclear and radioactive agents. Springer Science & Business Media. (2009).
3. Bourdon, B., Turner, S., Henderson, G. M., & Lundstrom, C. C. Introduction to U-series geochemistry. Reviews in mineralogy and geochemistry, 52(1), 1-21. (2003).
4. Church, T. M., & Sarin, M. M. U-and Th-series nuclides in the atmosphere: supply, exchange, scavenging, and applications to aquatic processes. Radioactivity in the Environment, 13, 11-47. (2008).
5. Duce, R. A., Mohnen, V. A., Zimmerman, P. R., Grosjean, D., Cautreels, W., Chatfield, R., ... & Wallace, G. T. Organic material in the global troposphere. Reviews of Geophysics, 21(4), 921-952. (1983).
6. Dueñas, C., Fernández, M. C., Carretero, J., Liger, E., & Cañete, S. Deposition velocities and washout ratios on a coastal site (southeastern Spain) calculated from 7Be and 210Pb measurements. Atmospheric Environment, 39(36), 6897-6908. (2005).
7. Elliott, S., Blake, D. R., Duce, R. A., Lai, C. A., McCreary, I., McNair, L. A., ... & Turco, R. P. Motorization of China implies changes in Pacific air chemistry and primary production. Geophysical Research Letters, 24(21), 2671-2674. (1997).
8. Hsiao, A. J., Chen, L. H., & Lu, T. H. Ten leading causes of death in Taiwan: a comparison of two grouping lists. Journal of the Formosan Medical Association, 114(8), 679-680. (2015).
9. Junge, C. E. Radioaktive Aerosole. In Nuclear Radiation in Geophysics/Kernstrahlung in der Geophysik, Springer, Berlin, Heidelberg, 169-201. (1962).
10. Jacobi, W. Die natürliche Radioaktivität der Atmosphäre. Biophysik, 1(3), 175-188. (1963).
11. Kuroda, P. K., Daniel, P. Y., Nevissi, A., Beck, J. N., & Meason, J. L. Atmospheric residence times of strontium-90 and lead-210. Journal of Radioanalytical Chemistry, 43(2), 443-450. (1978).
12. KAPL,. Inc. Lockheed Martin. Chart of the nuclides. 16th ed. (2002).
13. Keith A. Sverdrup, Elisabeth Virginia Armbrust, Ginger Armbrust. An Introduction to the World's Oceans, Edition, 9, 375 (2008).
14. Lau, K. M., & Li, M. T. The monsoon of East Asia and its global associations—A survey. Bulletin of the American Meteorological Society, 65(2), 114-125. (1984).
15. Lelieveld, J. O., Crutzen, P. J., Ramanathan, V., Andreae, M. O., Brenninkmeijer, C. A. M., Campos, T., ... & Hansel, A. The Indian Ocean experiment: widespread air pollution from South and Southeast Asia. Science, 291(5506), 1031-1036. (2001).
16. Lee, H. N., Wan, G., Zheng, X., Sanderson, C. G., Josse, B., Wang, S., ... & Wang, C. Measurements of 210Pb and 7Be in China and their analysis accompanied with global model calculations of 210Pb. Journal of Geophysical Research: Atmospheres, 109(D22). (2004).
17. Moore, H. E., Poet, S. E., & Martell, E. A. 222Rn, 210Pb, 210Bi, and 210Po profiles and aerosol residence times versus altitude. Journal of Geophysical Research, 78(30), 7065-7075. (1973).
18. Ming, Y., & Russell, L. M. Organic aerosol effects on fog droplet spectra. Journal of Geophysical Research: Atmospheres, 109(D10). (2004).
19. McNeary, D., & Baskaran, M. Residence times and temporal variations of 210Po in aerosols and precipitation from southeastern Michigan, United States. Journal of Geophysical Research: Atmospheres, 112(D4). (2007).
20. Meow Track map of Typhoon Dujuan of the 2015 Pacific typhoon season. Available: https://en.wikipedia.org/wiki/Typhoon_Dujuan_(2015)#/media/File:Dujuan_2015_track.png (2015).
21. Ministry of Health and Welfare, Taiwan, Republic of China. Deaths in Taiwan. Available: https://dep.mohw.gov.tw/DOS/np-1776-113.html. (2017).
22. Nevissi, A. E. Measurement of lead-210, bismuth-210, and polonium-210 in environmental samples. Journal of Radioanalytical and Nuclear Chemistry, 148(1), 121-131. (1991).
23. Nazaroff, W. W. Radon transport from soil to air. Reviews of geophysics, 30(2), 137-160. (1992).
24. Porstendörfer, J. Properties and behaviour of radon and thoron and their decay products in the air. Journal of Aerosol Science, 25(2), 219-263. (1994).
25. Persson, B. R., & Holm, E. Polonium-210 and lead-210 in the terrestrial environment: a historical review. Journal of Environmental Radioactivity, 102(5), 420-429. (2011).
26. Redfield, A. C. The biological control of chemical factors in the environment. American scientist, 46(3), 230A-221. (1958).
27. Samuelsson, C., Hallstadius, L., Persson, B., Hedvall, R., Holm, E., & Forkman, B. 222Rn and 210Pb in the Arctic summer air. Journal of Environmental Radioactivity, 3(1), 35-54 (1986).
28. Turner, M. C., Krewski, D., Pope III, C. A., Chen, Y., Gapstur, S. M., & Thun, M. J. Long-term ambient fine particulate matter air pollution and lung cancer in a large cohort of never-smokers. American journal of respiratory and critical care medicine, 184(12), 1374-1381. (2011).
29. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources, effects and risks of ionizing radiation. (1988).
30. Wilson, W. E., & Suh, H. H. Fine particles and coarse particles: concentration relationships relevant to epidemiologic studies. Journal of the Air & Waste Management Association, 47(12), 1238-1249. (1997).
31. Wang, Z., Yang, W., Chen, M., Lin, P., & Qiu, Y. Intra-annual deposition of atmospheric 210Pb, 210Po and the residence times of aerosol in Xiamen, China. Aerosol and Air Quality Research, 14(5), 1402-1410. (2014).
32. World Health Organization. Global health observatory (gho) data: Top 10 causes of death. Available: http://www.who.int/mediacentre/factsheets/fs310/en/ (2017).
33. Zhang, J. J., & Smith, K. R. Household air pollution from coal and biomass fuels in China: measurements, health impacts, and interventions. Environmental health perspectives, 115(6), 848. (2007).