屏東縣地下水受含氯污染使用限制地區監測式自然衰減法評估計畫
| 中文摘要 | 屏東縣潮州鎮崙東里新開寮地區於民國89年調查發現地下水中含有氯揮發性有機物，經調查後關切污染物為1,1-二氯乙烯（超過管制標準），於93年公告為地下水受污染使用限制地區（以下簡稱本場址），亦曾經檢測出有四氯乙烯、三氯乙烯等污染，但於近年監測皆未有超過監測標準。 由於本場址較靠近屏東平原東側，位於屏東沖積平原之上游區，整體含水層達約地表下200公尺，由於該地區幅員廣闊且污染物為含氯有機物，皆造成整治之困難性，近來之監測資料污染範圍已有往下游移動之趨勢，對於較下游人口稠密之區域，包含附近社區以及更下游之潮州鎮區域，可能逐漸產生影響。因此，屏東縣政府環境保護局提出監測式自然衰減法（Monitored Natural Attenuation, MNA）評估計畫（以下簡稱本計畫），探討本場址自然降解可行性並擬定分區管理策略。 本計畫已完成合約執行項目與數量，分析結果顯示關切汙染物1,1-二氯乙烯於上游監測井皆未超過第二類地下水監測標準，而中、下游部分點位超過第二類地下水污染管制標準，污染團前緣並未到達下游邊界監測井，且3處聚落公用水井分析結果皆未超過第二類地下水污染監測標準，經評估非致癌健康風險屬於可接受之風險範圍；地下水模式模擬20年污染移動的結果顯示，污染團可能往下游移動約700公尺，但並未到達更下游人口密集區；地下水微生物分析顯示本場址具有豐富活體微生物量，於大雨後可觀察到顯著的總菌數及活體菌量的上升，惟本場址在水質監測呈現好氧的狀態，這將不利於現地微生物降解1,1-二氯乙烯。經過污染趨勢統計分析顯示1,1-二氯乙烯濃度污染團大致呈現穩定或衰減狀態，推測本場址的污染物削減作用可能來自於地下水物理性的稀釋作用，具備MNA的條件。建議上游區域可採用MNA工法，並針對列管區域長期低於地下水監測標準可考慮解除列管；中游區域於適當位置增設監測井及採用現地工法進一步降低污染；下游區域邊界監測井持續執行MNA且監控邊界污染物是否持續往更下游移動。 | ||
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| 中文關鍵字 | 地下水、含氯污染、監測式自然衰減法 | ||
基本資訊
| 專案計畫編號 | 經費年度 | 112 | 計畫經費 | 3425 千元 | |
|---|---|---|---|---|---|
| 專案開始日期 | 2023/07/07 | 專案結束日期 | 2023/12/20 | 專案主持人 | 張立鵬 |
| 主辦單位 | 屏東縣政府環境保護局 | 承辦人 | 卓威廷 | 執行單位 | 裕山環境工程股份有限公司 |
成果下載
| 類型 | 檔名 | 檔案大小 | 說明 |
|---|---|---|---|
| 期末報告 | 屏東縣地下水受含氯污染使用限制地區監測式自然衰減法評估計畫.pdf | 16MB |
Assessment Plan for Monitoring Natural Attenuation of Chlorine Contamination in Restricted Groundwater Utilization Areas in Pingtung County
| 英文摘要 | In 2000, the groundwater in the Xinkailiao area of Lundong Village, Chaozhou Township, Pingtung County, Taiwan, was discovered to contain chlorinated volatile organic compounds. The main chlorinated volatile organic compound in this water was later found to be dichloroethylene, whose level exceeded the maximum permissible limit in the groundwater control standards of Taiwan; therefore, the aforementioned area was declared a groundwater use restriction zone (hereinafter referred to as “the Study Site”). Tetrachloroethylene and trichloroethylene were also detected in the aforementioned area; however, in recent years, the detected levels of these compounds have not exceeded the corresponding maximum permissible limits in the groundwater control standards of Taiwan. The Study Site lies on the eastern side of the Pingtung Plain and upstream of an alluvial plain. The aquifer at this site extends as far as 200 m below the surface. Because of the vastness of the Study Site and the existence of chlorinated organic matter in its groundwater, groundwater remediation at this site is difficult. Recent monitoring data indicate that the contamination zone is moving downstream, which may lead to gradual impacts on densely populated areas, such as neighboring communities and the Chaozhou Township. Consequently, the Pingtung County Environmental Protection Bureau proposed the Monitored Natural Attenuation Plan (hereinafter referred to as “the Plan”) to examine the feasibility of natural degradation at the Study Site and to formulate a zoning-based groundwater management strategy for this site. The contracted tasks and work quantities of the Plan have been completed. According to analysis results, the dichloroethylene level did not exceed the maximum permissible limit in the control standards for Category 2 groundwater in upstream monitoring wells but exceeded this limit in midstream and downstream monitoring wells. The contaminant had not yet reached the monitoring wells at the downstream boundary. A groundwater analysis at three locations with settlements indicated the contaminant levels in the groundwater of these locations did not exceed the corresponding permissible limits for Category 2 groundwater in the groundwater standards. Moreover, the noncarcinogenic health risks of this groundwater were within an acceptable range. The results of a groundwater model simulating the movement of dichloroethylene suggest that over 20 years, this contaminant may move 700 m downstream over time but will not reach the densely populated areas located further downstream. An analysis of groundwater microbes revealed that the Study Site was rich in viable microbial biomass and that the total bacterial count and viable microbial biomass at this site increase considerably after heavy rains; however, the groundwater at the Study Site was found to be aerobic and therefore inconducive to the local microbial degradation of dichloroethylene. A statistical analysis of pollution trends revealed that the dichloroethylene level at the Study Site is stable or weakening, possibly because of dilution, which represents an example of MNA. This study recommends the adoption of MNA practices in upstream regions at the Study Site and the removal of areas exhibiting satisfactory groundwater quality for long periods from monitoring lists. In midstream areas, monitoring wells can be added where required, and on-site methods can be used for reducing contamination. At the boundary of the downstream area, MNA should continue to be practiced at monitoring wells, and the downstream movement of contaminants should still be monitored. | ||
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| 英文關鍵字 | groundwater, MNA , chlorinated volatile organic compounds | ||