應用地化模式模擬蘭陽平原含砷地下水之傳輸與宿命

Geochemical simulation on the fate and transport of groundwater arsenic in Lanyang Plain

楊宗穎(Tzung-Ying Yang)

指導教授 ： 劉振宇 ； 陳世楷

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00654

摘要

地下水為蘭陽平原重要的水資源之一。本研究主要目的係探討蘭陽平原含砷地下水之傳輸宿命。先應用地下水流動模式MODFLOW建立蘭陽平原地下水流流場，並以地下水觀測井水位資料加以驗證，另以PHREEQC地化模式決定地下水平衡狀態下主要物種生成與飽和指數。再應用HYDROGEOCHEM地化傳輸模式模擬三種情境地下水中砷等物種的傳輸歷程，包括改變抽水量、垃圾掩埋場滲漏及蘭陽溪沿岸生雞糞的大量施用。研究結果顯示，三種情境模擬結果均顯示砷濃度變化明顯，自扇頂至扇尾隨模擬時間的增加而增加，由於扇尾地下水趨於還原環境，導致該區砷濃度明顯上升。此外，在礁溪溫泉使用量大增之情況下，會造成該區之地下水位大幅下降。而在垃圾掩埋場持續滲漏之情況下可明顯看出砷汙染團之形成，並往外擴延。蘭陽溪沿岸長期施用生雞糞亦會造成地下水之嚴重砷汙染。建議應於扇頂及蘭陽溪沿岸增設觀測井加強監測，而政府相關單位亦應擬定適當的管理措施以保育此地區之地下水資源。

關鍵字

砷 ； 蘭陽平原 ； HYDROGEOCHEM ； 地下水

並列摘要

Groundwater is one of the most important water resources in Lanyang plain. The objectives of this study are to evaluate the fate and transport of arsenic (As) in groundwater of the Lanyang plain. The lithological profiles and hydraulic parameters were collected from Central Geological Survey and Water Resources Agency of Taiwan to establish the conceptual hydrogeological settings. The groundwater flow model MODFLOW was first applied to establish the groundwater flow field which was calibrated by using the groundwater level data. The geochemical equilibrium model PHREEQC was adopted to determine the major species and saturation index by using water quality data from monitoring well. The 3-dimensional hydrogeochemical transport model HYDROGEOCHEM was then applied to assess the anthropogenic influences on the fate and transport of As under various scenarios including different pumping rate, landfill leakage, and the application of poultry litter along the Lanyang river. All simulated results show that under these scenarios the concentrations of arsenic increases with the simulation time from the proximal-fan to the distal-fan, and the most significantly change was found in the distal-fan due to the more reducing environment. High As concentration of observed in the distal-fan area. Additionally, as the groundwater pumping amount increased 1.5 times, the groundwater level was significantly decreased in Chiao-Shi area. The results also showed that the continuous leakage of the landfill resulted an extensively developed As plume outside the landfill. And the long-term application of poultry litter along the Lanyang river also cause the severe As pollution of the groundwater. It is suggested that the setup of observation wells in proximal-fan and along the Lanyang river can effectively monitor groundwater quality. Moreover, the relevant governmental agencies should formulate effective measures to conserve the groundwater resources in Lanyang plain.

並列關鍵字

Arsenic ； Lanyang plain ； HYDROGEOCHEM ； Groundwater

參考文獻

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