空氣污染排放交易抵換係數之適用性分析

Abstract

空氣污染排放交易是一個以市場誘因引導污染減量與技術提昇，且能兼顧經濟與環境保護雙重目標的政策。抵換制度乃是交易時排放權由賣方轉移至買方依一個抵換係數交易，以避免隨機交易，反而增加對環境及人們健康的衝擊。過去研究雖曾提出以污染源間之距離建立抵換係數，但並沒有分析其適用性，且未考量人口密度、環境品質及曝露風險，故本研究提出以人口密度、環境濃度、曝露風險等抵換因子建立抵換係數，並針對鄰近的上風污染源提出一個擴散影響修正函數，以反應對賣方區域增加的環境風險。環境濃度因子以未交易前之大氣污染物濃度為係數，此因子可避免特定區域因累積排放量而導致污染濃度過高。曝露風險因子為人口數與大氣中污染物濃度之乘積，此因子主要考量總曝露量，以減少交易後曝露量上升的情形。本研究建立一個交易模擬模式，依據不同抵換因子建立之抵換係數，以硫氧化物為案例污染物，分析不同扺換制度的差異，及探討各抵換因子的適用性。研究結果顯示，抵換因子並不能一體適用，不同抵換因子有其不同的適用情況，必須依據污染源之分佈及大小，選擇適當的抵換係數，方能有效改善空氣品質及曝露風險。

Air pollution emission trading (APET) is an economic incentive program that can effectively promote pollution reduction and technology advance. An offset ratio can be applied to reduce significant environmental and health impacts caused by inappropriate pollution load redistribution after implementing an APET program. Although an offset ratio determined based on the distances among emission sources was previously reported, population, ambient air quality and exposure risk were not considered. This study was thus initiated to explore and propose various offset ratio functions based on the distance and three essential factors of population density, ambient pollutant concentration, and exposure risk for reducing environmental and health risks after applying an APET program. The population density based function is proposed to avoid emission permits being transferred into highly populated areas. The ambient pollutant concentration based function is intended to avoid the occurrence of excessively high concentration areas due to cumulative impacts. And the exposure risk based function is used to avoid high human exposure for reducing health risk. An APET simulation model was established to implement several hypothetical case studies and to evaluate the applicability of each offset ratio function. As demonstrated by the results obtained for the illustrative cases, different offset ratio functions are applicable for different pollution source and population distributions. Carefully assessing the patterns of pollution source and population distributions is essential for selecting an appropriate offset function to improve air quality and decrease exposure risk.