高科技園區有害空氣污染情境分析及綜合風險評估

Abstract

新竹科學園區所排放的有害空氣污染物(Hazardous Air Pollutants, HAPs)可能影響周遭民眾健康，本研究因而建立一套系統流程評估分析HAPs於周遭地區之濃度分佈及暴露風險。研究流程主要包括案例區重點污染物選取與相關資料建立、模式模擬與比較、情境分析、風險評估及周界期望濃度分析等五大部分，重點污染物主要依據案例區監測結果及其有害程度篩選。模式主要採用ISCST3及AERMOD二模式模擬園區周界HAPs分布情形，並比較兩套模式模擬之差異；依據各年不同排放量之HAP情境模擬結果分析HAPs的空間分佈；再進一步依各情境HAPs空間分佈及採用致癌及非致癌風險值，分別評估單一污染物及多污染物對於周界居民可能造成的風險。且針對有較顯著危害性HAP以等去除率分析欲達周界期望濃度值所需之理想減量率。 本研究分別以2008至2010年各年檢測資料配合不同情境，且建立較接近實際排放總量之情境S，並以二模式進行模擬，結果顯示各HAP較高濃度皆發生於低風速下，較密集煙道口附近；情境S因排放量較高，模擬濃度值較高及影響區域皆較廣。由於ISCST3及AERMOD模式靜風時處理方式不同，使得二模式在低風速時模擬結果有顯著差異。根據模擬結果，砷污染物較高致癌風險主要發生於西方周界約0.1-0.6公里，唯砷污染物模擬值低於監測值，實際風險值應較高；情境S下氯氣污染物之長期危害性最為顯著，最大慢性危害指數為8.6，明顯高於其他重點污染物，顯示需加強氯氣污染物管制。周界濃度分析則發現砷污染物及氯氣污染物需減量90%左右方能使風險低於百萬分之一或HI值小於1。

Hazardous air pollutants (HAPs) emitted from Hsinchu Science-based Industrial Park (HSIP) may significantly affect the health of surrounding residents. A systematic procedure was thus established for analyzing HAP distributions and assessing residential exposure risks. The procedure includes five major steps: selection of major pollutants, model simulation, scenario analysis, risk assessment and expected ambient concentration analysis. Major pollutants were selected based on their emission quantites and TWA-TLV values. The ISCST3 and AERMOD models were applied to simulate spatial an temporal HAP distributions. Simulated distributions were used to analyze spatial HAP impacts on surrounding areas and results obtained based on both models were also compared. Lifetime incremental cancer risk and Hazard Index (HI) were applied to estimate residential cancer and noncancer exposure risks from both single and multiple HAPs. Finally, required reductions of emissions for achieving several expected ambient qualities were estimated based on the uniform removal method for HAPs with high potential hazard. Several scenarios were analyzed based on emission data sets in 2008- 2010, and scenario S was established to simulate actual emission. While a low speed wind occurs, high HAP concentration is likely to occur at the downwind areas of the spot with dense HAP sources. The result for scenario S shows higher HAP concentration and wider impact because its total emission quantity is significantly larger than those of other scenarios. Since ISCST3 and AERMOD use different definitions for calm wind, significant difference exists between the results simulated by both models under low speed winds. According to the simulated result, maximal arsenic concentration mainly occurs at area about 0.1-0.6km to the western boundary of HSIP. However, the actual risk may be higher because the simulated result is lower than monitored values. The maximal HI of chlorine is 8.6 and is significantly higher than other major HAPs. For arsenic and chlorine and to achieve the cancer risk not exceeding 10-6 or HI less than 1, about 90% reduction of all pollution sources is required.