空品區總量管制之硫氧化物許可排放量分析

Abstract

近年來政府積極研擬總量管制相關策略，以彌補過去單以濃度為法規標準的缺失，兼顧排放量對空氣品質之影響，執行該策略，首先須訂定總量及分配基準，同時考量公平性及效率，並須考量空間及個別污染物情況等因子，惟目前並無固定的流程來決定。 本研究因而發展一個系統化程序，來決定空氣中硫氧化物之許可排放量。該程序首先評估空品區在不考量外區量、污染排放不確定性、誤差及未知量等影響下的容許增量，由於以擴散模式模擬所需電腦分析時間的限制，本研究以空氣品質較惡劣之代表天數中，選取類似全年風場之代表風場共36天，並利用ISC模式進行擴散模式，然後分析及比較在不同的等去除率下，日平均與小時不合乎容許增量計算基準的受體點情形，決定日及小時平均不合格比率，作為決定總量的依據，但由於等去除率法的經濟效率較差，故本研究另以每一污染源對所有不合格受體點之總影響定義為污染源的顯著影響係數(significant impact coefficient，SIC)，再進而基於SIC、排放量、及人口密度等因子分別建立各污染源新的去除率決定函數，以得到經濟效率較佳的總排放量及各污染源容許排放量。 本研究以桃竹苗空品區為案例區，並依中鼎公司所建立之排放資料進行模擬，比較與討論等去除率法及本研究所提SIC等方法所決定之總量及分配量的優缺點與適用性，結果發現以SIC相關因子決定之去除函數較等去除率法有明顯較高的成本效益，至少減少10%以上總削減量，即可於較嚴格不合格率條件下符合要求，且由於考量hot spot問題，可求得較適當的總量管制基準量，以利於推行總量管制。

Total-mass-based emission management (TEM) is an important air quality protection strategy recently initiated. This new strategy is intended to redeem the shortcoming of the traditional concentration-based regulation implemented in the past. Before implementing such a strategy, appropriate total-mass and emission allowance allocation should be efficiently determined based on a desired air quality level. Currently, no widely accepted procedure is available to determine total-mass and emission allowance. A systematic procedure is therefore proposed in this study. The total-mass allowance is determined by the uniform-removal (UR) method, based on daily- and hourly-average concentrations simulated by the ISCST model and violation ratios for critical receptors. Since allowance determined by the UR method is not economically efficient, the significant impact coefficient (SIC) for total pollution contribution on all critical receptors from each source is defined in this study. Emission allowance determined based on SICs and population density can improve both economic efficiency and exposure risk, while compared with the UR method. A case study for the Tao-hsu-miao airshed SOx control is implemented. Results obtained from the UR and SIC methods are compared and discussed for their advantage, disadvantage, and effectiveness. According to the results, results obtained from the SIC method are more cost efficient than those obtained from the UR method, about 10% reduction for the studied case. Further, the SIC method can significantly improve the air quality at locations that seriously suffer from air pollution (hot-spot). The proposed SIC method is expected to provide appropriate emission allowance to facilitate the implementation of the TEM strategy.