預警監測井網效率探討

台灣近幾十年來工商業快速發展，開闢了許多工業區以及科學園區，但是部分工業區因廠商管理不夠完善，造成工業區的土壤及地下水受到污染。為了有效預防工業區可能衍生的土壤及地下水污染，我國環保署於99年修正土污法第六條第三項，給予目的事業主管機關應定期檢測土壤及地下水品質狀況之責任。而針對地下水污染問題，環保署及經濟部陸續於全國各大工業區規劃地下水預警監測井網，以瞭解各工業區之背景地下水污染潛勢。本研究利用 MODFLOW 程式模擬地下水流，配合 MT3DMS 模擬污染物之傳輸，模擬在一個假設的工業區場址中，當污染團滲入地下水時溶質傳輸的狀況，探討監測井的捕捉率，捕捉率大致上就是監測井能夠捕捉到規定濃度的機率。以三種主要變因以及四種不同情境進行討論，分別為延散度比值、流速快慢、距離洩漏污染源的遠近、警戒濃度以及洩漏時間長短。模擬結果顯示當流速越快且延散度比值越高時，從圖中可以得知其監測井口數-捕捉率發展趨勢遠比其他狀況時還要快。然而在研究中也能發現延散度比值對於結果不會有太大影響，只有在流速比較快時才能看的出來其差異所在，亦即流速越快時會對延散度比值越敏感，流速越慢時會對距離遠近越敏感。模擬結果也顯示出，以早期發現為前提下，模擬時間3個月且偵測濃度為10 ppb是最快且最具經濟效益的，比較符合最佳化的定義，但是否會造成錯誤的警訊需要再加強；而模擬時間6個月且偵測濃度為25 ppb是最慢且最不符合經濟效益的。

關鍵字

TCE ； DNAPL ；污染； MODFLOW ；模擬；捕捉率；警戒濃度；監測井網設計；污染物傳輸

並列摘要

Due to rapid growth of economy in recent decades, the amount of industrial area had increased dramatically. However, in some of those industrial zones, faulty managements may lead to soil and water pollution. In order to prevent possible soil and groundwater pollution in industrial areas effectively, EPA revised “Soil Pollution Law” in 2010 to give the target business authority the responsibility to check the quality of soil and groundwater regularly. In addition, in response to the groundwater pollution, EPA and the Ministry of Economy have continued to plan early-warning monitoring well networks in major industrial areas to understand the potential of groundwater pollution in the background of each industrial zone. The research studied the migration of chlorinated solvent plume in aquifer by simulation with MODFLOW and MT3DMS. The hypothetical industrial site was chosen to be the target of case study in this research. Groundwater in the aquifer beneath the hypothetical industrial site is contaminated with TCE. The capture rate was simulated to study the result on the efficiency of groundwater monitoring well network by modifying the number of wells. In addition, three main causes and four different scenarios were discussed, including the ratio of transverse dispersivity and longitudinal dispersivity, the flow rate, the horizontal distance between the source of pollution released and the well, the value of warning concentration, and the length of time. The results show when the flow rate is faster and the dispersion ratio is higher, it can be seen from the figure that the slope of the number of monitoring wells-capture rate diagram is much faster than other conditions. However, it can also be found in the research that the dispersion ratio does not have much effect on the results. The difference can only be seen when the flow rate is relatively fast. Namely, The faster the flow rate, the more sensitive it will be to the ratio of dispersion; the slower the flow rate, the more sensitive it will be to the distance. The results also show that under the premise of early detection, the simulation time of 3 months and the warning concentration of 10 ppb is the fastest and most economical, which is more in line with the definition of optimization; however, whether it will cause false warnings needs to be strengthened. On the other hand, the simulation time of 6 months and the warning concentration of 25 ppb is the slowest and least economical.