南投名間地下水NO3-之來源與轉化

Abstract

本研究分析南投名間農作區與城鎮區共12口水井及一處湧泉水樣的NO3- 之濃度及氮、氧同位素組成，以了解名間地區地下水NO3- 污染狀況，探討地下水中NO3- 的來源及轉化。結果顯示在2004年6月至2005年9月研究期間，約有54%水樣之NO3- 濃度高於飲用水標準這些超標的地下水主要發生在農作區內，其NO3- 之來源主要是土壤有機物和化學肥料少部份來自動物性堆肥。基本上，本研究區地下水、。之濃度及氮氧同位素特微反映不同來源氮之硝化作用，以及後續不同來源氮之混合作用的影響。農作區地下水中並未顯示發生造成NO3- 濃度降低之脫氮或同化作用：反之，城鎮區之地下水則很明顯曾受到同化作用。 This study analyzed the concentration, and nitrogen and oxygen isotope compositions of groundwater's NO3(superscript-), including twelve wells and one spring in agricultural and urban regions of Ming-Jian, Nantou Colunty. The purpose was to better understand NO3(superscript-) pollution and discuss possible NO3(superscript-) sources and transformation. The results indicate that nearly 54% of NO3(superscript-) contaminated samples exceeded the criterion for drinking water during the studied period (June 2004 to September 2005), especially in the agricultural region. The sources of NO3(superscript-) in polluted groundwater are mainly related to soil nitrogen and chemical fertilizer, in addition to minor animal manure. The concentration and nitrogen and oxygen isotopic compositions of groundwater NO3(superscript-) in the studied area are mainly controlled by the nitrification from varied nitrogen sources and the subsequent mixing process between the varied sources. Denitrification/assimilation that could reduce the NO3(superscript-) concentration in groundwater is not evidenced in the agricultural region studied, but the assimilation is significant in urban groundwater.