台灣北部某水源區大氣汞物種濃度變化情形之研究

汞為我國土壤污染管制重金屬項目中唯一具揮發性、持久性及生物累積性的毒性汙染物,易藉由乾濕沉降到達表土與水體,並透過食物鏈的生物累積效應對人體健康與生態環境造成影響,其中汞的來源主要可分為人為排放源及自然排放源,都直接影響大氣汞的濃度變化;爰此,為瞭解臺灣地區之大氣汞物種,本研究調查台灣某水源區大氣汞物種變化情形。本研究總計完成九個月大氣汞物種自動連續監測作業(2015/11/24 至 2016/8/31),共取得 34,872 筆氣態元素汞、2,892 筆粒狀結合汞及 2,888 筆反應性汞調查資料,其平均濃度值分別為 2.15 ng/m3、9.09 pg/m3 及 2.60 pg/m3,與其他背景濃度研究文獻結果相似,顯示本研究石門水庫測站之汞濃度監測數值符合國際間認定之大氣汞背景值之定義範圍,受其他固定污染源干擾程度較低,但仍明顯受季節性因子如風向、溫度、紫外線強度影響造成每日大氣汞物種之變化;且於冬、春、夏三個季節中,以冬季大氣汞物種濃度最高,春季次之,夏季最小, 其大氣汞物種濃度分別於冬季 2.34 ng/m3、14.0 pg/m3 及 3.14 pg/m3,春季 2.30 ng/m3、8.28 pg/m3 及 2.09 pg/m3,夏季 1.80 ng/m3、4.65 pg/m3 及 2.35 pg/m3;為比較大氣汞物種自動連續監測與環保署公告手動採樣方法的差異,本研究執行空氣中汞採樣分析作業,共採集 32 組手動採樣分析之氣狀汞及 33 組粒狀汞樣品汞濃度分析,其濃度範圍分別為 1.45-3.23 ng/m3 及 4.65-103 pg/m3;相較於自動連續監測結果,氣狀汞濃度無明顯差異,而手動採樣之粒狀汞濃度明顯高於自動連續監測,研判與其粒狀汞樣品粒徑有關,自動連續監測設備所採集之粒狀汞樣品粒徑小於 2.5 μm,而手動採樣之粒狀汞樣品則係採集空氣中總懸浮微粒,但兩者粒狀汞濃度呈一致性,若自動連續監測之粒狀汞濃度偏高時,手動採樣分析之粒狀汞濃度亦有偏高之趨勢;本研究模擬推估之汞年乾沉降量為2.93 μg/m2,相較於中央大學雲與氣膠實驗室所同時採集之乾沉降量為 7.01 μg/m2 約為 50%低估,研判可能係因為模式並非開發給亞洲地區,缺乏許多參數,造成模擬數值之誤差。

關鍵字

大氣汞物種；自動連續監測系統；手動採樣系統；乾沉降

並列摘要

Mercury (Hg), one of the global pollutants, has caused severe impacts globally. Atmospheric Hg, the relative stable form in the atmosphere, was removed easily by the atmospheric mechanism due to the bio-accumulate via the food chain. There are three major atmospheric species, gaseous elemental Hg (GEM), reactive gaseous Hg (RGM), and particulate Hg (PHg). The anthropogenic emission sources and the natural emission sources were two major contributors of atmospheric Hg. Therefore, investigating the behavior of atmospheric Hg at a clean water reservoir might provide more knowledge on the Hg enrichment in the reservoir environment, from which water was used for drinking purpose. Results from atmospheric Hg continuous monitoring system were obtained during the sampling period. A 34,872 data amount of GEM was collected with 2.15 ng/m3 as the mean concentration. For RGM, a 2,888 data amount was collected with 2.06 ng/m3 as the mean concentration. For PHg2.5, a 2,892 data amount of PHg2.5 was also collected with 9.09 ng/m3 as the mean concentration. Comparison of other atmospheric Hg continuous monitoring sites was addressed that the concentrations of the study were considered as local background level. Elevated GEM concentrations at 7:00 am to 12:00 am and those decreased at 0:00 am to 7:00 am were exhibited in the study. Photochemical reactions may play an important role in elevated RGM at noon. The PHg2.5 did not show correlation with atmospheric coefficient. Comparison of the sampling method on GEM and PHg was addressed that 32 sample size of GEM and 33 sample size of PHg were collected in the study. The concentrations of GEM from the manual sampling system range from 1.45 to 3.23 ng/m3, and that of the automated speciation data were range from 1.39 to 2.93 ng/m3. The results of GEM and PHg showed high correlation between automated system and manual system by Pearson’s correlation. The simulation of dry deposition addressed that the yearly dry deposition of RGM and PHg was approximately 2.93 μg/m2. The results in the study were 50% underestimated to that of cloud and aerosol lab, namely 7.01 μg/m2. Due to the lack of adequate parameters, such as land use categories and leaf area index, the underestimated results were shown in the study.

並列關鍵字

atmospheric mercury speciation ； automated monitoring system ； manual sampling system ； dry deposition

參考文獻

Sheu, G.-R., Lin, C.-C., and Lin, N.-H. (2007). Monitoring of atmospheric mercury concentration at surface sites in Taiwan. Journal of Environmental Protection, 30(1).

Gabriel, M., Williamson, D., Brooks, S., and Lindberg, S. (2005). Atmospheric

Agnan, Y., Le Dantec, T., Moore, C.W., Edwards, G.C., and Obrist, D. (2016). New constraints on terrestrial surface-atmosphere fluxes of gaseous elemental mercury using a global database. Environmental Science & Technology, 50(2), 507-524. doi:10.1021/acs.est.5b04013

Ariya, P.A., Amyot, M., Dastoor, A., Deeds, D., Feinberg, A., Kos, G., Poulain, A., Ryjkov, A., Semeniuk, K., Subir, M., and Toyota, K. (2015). Mercury physicochemical and biogeochemical transformation in the atmosphere and at atmospheric interfaces: a review and future directions. Chemical Reviews, 115(10), 3760-3802. doi:10.1021/cr500667e

Ariya, P.A., Peterson, K., Snider, G., and Amyot, M. (2009). Mercury chemical transformations in the gas, aqueous and heterogeneous phases: state-of-the-art science and uncertainties. 459-501. doi:10.1007/978-0-387-93958-2_15

國際替代計量

台灣北部某水源區大氣汞物種濃度變化情形之研究

全文下載

主題瀏覽