應用逆大氣擴散模式推估離島工業區二氧化硫排放量

Abstract

隨著人民環境意識抬頭，空氣品質已經漸漸的受到重視，總量管制策略是透過推估污染排放量，達到量化污染源造成污染程度的功用，然而，目前國內常用的空氣污染排放量估算方法為排放係數法，係透過機械組件數量和機械排放係數計算，並沒有考量到實際觀測情形。本研究透過有美國環保署認可之優選大氣擴散模式—CALPUFF，建立研究區域之空氣污染模式，並採用逆大氣擴散模式，即結合環境觀測值運算，得到推估的排放量，並比較其與排放係數法所得結論。石化工業為國內二氧化硫主要的來源之一，本研究區域為雲林濱海地區，緊鄰離島石化工業區，於1998 年12 月正式啟用，本研究選定針對鄰近之麥寮、麥寮中學、台西、台西國中、崙背、宏崙國小、二林，七個一般空氣測站評估模擬結果。由於工業區位於研究區域之西部，本研究依據西風盛行月份選擇了研究時間2012 年7 月，並將模式依內建參數調整分為四組，NO.1、NO.2、NO.3、NO.4 欲比較其選項影響差異，並整理了工業區啟用前後各測站之環境SO2 濃度變化，並透過數值統計指標評估其準確度，並進而計算其SO2 總排放量。其結果顯示NO.3、NO.4 模擬成果在麥寮、台西、崙背、宏崙國小地區均較NO.1、NO.2 為佳，麥寮中學NO.4 模擬相關係數甚至高達0.75，麥寮測站NO.3一致性指標最高也高達0.55，而二林地區之模擬成效差，推估可能與其他研究地區不同的SO2 主要來源型態。估計2012 年7 月2 日~29 日，共28 天，SO2 推估總排放量採用NO.3、NO.4 之推估為880~893 噸，與環評核訂換算28 天排放量1224 噸較小，略大於工業區自我評估換算的28 天517 噸。然而因為雲林地區探空資料缺乏、一般測站資料不齊全、數位地型高層圖和土地利用資料有時間差異、土地參數準確度存疑等，以及研究結果標準差極高，種種皆代表研究仍有許多不確定性有待再克服。

In the last 20 years, the Yunlin offshore industrial park has significantly contributed to the economic development of Taiwan. Its annual production value has reached almost 12 % of Taiwan’s GDP in 2012. However, the offshore industrial park is considered the major source of air pollution to nearby counties, especially, the emission of sulfate dioxide (SO2). Although studies have found that exposures to high level of some SO2 have caused adverse health effects on both human and ecosystem, it is a critical issue in estimating SO2 emissions. Nowadays emission estimation techniques are usually used emissions factors in calculation. Because the methodology considered totality of equipment activities based on statistical assumptions, it would encounter great uncertainty between these coefficients. The methodology of this study attempts to estimate SO2 emission of the Yunlin Offshore Industrial Park using an inverse atmospheric dispersion model which is applied to the combination of CALPUFF dispersion model adopted by the United States Environmental Protection Agency (U.S. EPA) as a preferred model and observation data of SO2 at monitoring site in Yunlin district. After that, comparing the solution with observation data collected for the time before industrial operation in 1999 and after 2010 by the Taiwanese Environmental Protection Administration (TW EPA). This study work in group on 4 kinds of dispersion coefficient around 7 monitoring sites. It shows well simulation performance on Tai-si, Mai-liao, Lun-bei Villages. In contract, the results in Er-lin Township is not well associated with the simulation and monitoring where might suffer from other pollution source. Estimated SO2 emission in the study area from July 2, 2012 to July 29, 2012 is around 1612-880 ton which is a little lower than Environmental Impact Assessment’s approve but a little bit higher than industrial park’s self-announced. Despite of that, the study result already have lots of challenge. There are so much uncertainty about land use data, terrain data, upper air data, parameter, even model itself, the standard deviation shows high uncertainty.