加油站土壤氣體及地下水監測模擬

Abstract

加油站地下儲油槽與輸油管線會隨著使用年限的增加，使得老舊之油槽或輸油管線容易出現裂隙並發生油品洩漏。為了避免油品洩漏之量過多與洩漏時間過長而造成嚴重污染，因而必須設置監測設備進行油品洩漏偵測，然而於油品污染團傳輸之過程中會受地質條件、障礙物(油槽)等影響，使得傳輸路徑與距離皆受影響並間接影響監測井之監測效果。為了瞭解監測井於不同洩漏情境與土層狀態間相互關係，因此本研究以數值模擬軟體(TMVOC)模擬各種不同之洩漏情境與地層狀況，以探討監測井可能的最佳配置方式與監測範圍。研究結果顯示地下水位較高者(2 m)之土壤氣體監測井其靈敏度較地下水位低者(5 m)為高；監測井距離油品洩漏點近者(3 m內)其效果較佳；而土層透水係數大、孔隙率小者其污染團之傳輸速率較快，對於土壤氣體之監測亦能有較大之幫助。地下水體之監測相較於土壤氣體而言其整體效果不佳，然而若監測井距離油品洩漏點較遠處時，則土壤氣體之效果反而不如地下水體監測井。

The potential of leakage of USTs of gasoline station increases with their service life. In order to avoid serious pollution, monitoring measures are employed to provide early warning. Among the monitoring methods, soil gas and groundwater monitoring detect the leaked product directly. The pathway of leaked gasoline flows and diffuses and thus, in turn the effectiveness of soil gas and groundwater monitoring, may be affected by the existence of USTs of gasoline station. In this study, numerical simulation with the software TMVOC was performed in order to assess the effectiveness of soil gas and groundwater monitoring. The results show that both soil gas and groundwater monitoring are more effective if the site has a shallow groundwater table and the soil has higher hydraulic conductivity and lower porosity. The effectiveness of soil gas monitoring is better than groundwater monitoring in general, when soil gas and groundwater monitor well are far away leakage then the groundwater monitoring is better than soil gas.