應用AERMOD 模式於台灣之複雜地形之探討

Abstract

美國環保署已在2005 年，將AERMOD 公告為固定污染源的優選 擴散模式，來取代舊有的ISC 擴散模式；由於AERMOD 改變ISC 部 分的模擬演算公式與方法，如AERMOD 在複雜地形中煙流的傳輸過 程與處理方法和ISC 不同，其計算模擬範圍內每個受體點的臨界煙流 高度，此高度決定煙流是否越過或繞過地形；因此本篇研究主要探討 在複雜地形效應下兩模式的擴散情形及AERMOD 在台灣的適用性。 首先，比較兩種空氣品質模式原理如大氣穩定度、混合層高度的 計算和地表特性敏感度分析；接下來，以複雜地形條件下的電廠為模 擬案例，結果顯示：最大著地濃度均發生在地程較高的地方，且可以 預期的是，AERMOD所模擬結果大部分會比ISC模擬濃度低，而兩模 式的濃度差異會隨平均時間增加而變大，年平均值差異最大。再來測 試容許增量限值，AERMOD所模擬結果較可符合法規標準。 最後將電廠附近監測站作為受體點模擬並與觀測值做比較，由於 在夜間混合層高度會比煙囪有效高度低，所以比較兩模式於日間時段 模擬濃度與觀測值的相關性，而AERMOD 模式在對流條件下考慮三 煙流模式計算方法，在濃度分布上較ISC 接近觀測值。

AERMOD (AMS/EPA Regulatory Model) was officially promulgated as the U.S. EPA preferred dispersion model for industrial point sources on 2005. AERMOD’s model formulation contains many changes over its predecessor, ISC (Industrial Source Complex Model). As plume transport is handled differently in AERMOD than the COMPLEX portion of ISC. Calculating the dividing streamline height at receptor within a domain and determining whether a plume will rise over or diverge around it. On this study, both models are simulating the complex terrain effects and the applicability of AERMOD in Taiwan. First of all, the comparison theory of two air quality models, such as atmospheric stability, mixing layer height and sensitivity analysis of surface characteristics. Second, the simulation of power plant cases on complex terrain. The result: the maximum concentration often occurs on the higher ground level. It’s expected that the AERMOD results most of predicted lower concentrations than ISC. The differences between the two models tended to increase with averaging time, the largest differences were in the annual average. In testing the allowable pollutant increase limits (APIL), the amount of concentration is better less than regulatory standards by the AERMOD tested. Finally, the Monitoring station near the power plant as a receptor simulation and compared with the observed, due to the mixing layer height at night than the effective stack height is low. Comparing the two models during the daytime simulation of concentration and observed value relevance. But AERMOD model considers the computing three plume treatment of the convective boundary layer (CBL), the concentration distribution close to observed value than the ISC.