臺北關渡平原農地砷及鉛含量分別介於8-458mg kg^(-l)及23-600mg kg^(-1),在現有農耕地中此含量已屬於異常之高。爲確定砷及鉛來源及影響範圍,本研究以多頻感應耦合電漿質譜儀(MC-ICP-MS)檢測環境介質灌溉水源與土壤的鉛同位素比值206Pb/207Pb、208Pb/207Pb,經空間群集分析,並藉由地理資訊系統展示,比對歷史的圖層資料以鑑定砷及鉛的來源。結果顯示,因天然地球化學特性,地熱谷溫泉砷及鉛含量偏高,而關渡平原農地東南側熱區之土壤則是過去引用地熱谷水源灌溉長期累積,導致今日農地砷及鉛濃度異常。
In Guandu Plain, the paddy soils hold anomalously high level of 8-458 mg kg^(-1) for arsenic and 23-600 mg kg^(-1) for lead. We propose to use lead isotope ratios, 206Pb/207Pb and 208Pb/207Pb, determined by multi-collector inductively coupled plasma mass spectroscopy (MC-ICP-MS), to distinguish pollution sources. Using geographical information system (GIS) technology, a significant spatial cluster relationship is observed for sample lead isotope ratios. Results show that the migrations of As and Pb are primarily influenced by geochemical processes. The hot-spot areas for As and Pb located in the southeast parts of Guandu Plain arose from the long-term irrigated the water mixed with hot spring from the Thermal Valley.