梨山農作區水體中NO3（上標 -）之來源與轉化

Sources and Transformations of NO3(superscript -) in Waters of Li-Shan Agriculture Area

10.30058/SE.200606.0005

彭宗仁(Tsung-Ren Peng)；范家華(Chia-Hua Fan)

集水區 ； 梨山農作區 ； 氮氧同位素 ； NO3（上標 -） ； 轉化作用 ； Catchment ； Li-Shan agriculture area ； Nitrogen and oxygen isotopes ； NO3(superscript -) ； Transformation

土壤與環境

9卷1&2期（2006 / 06 / 01）

43 - 58

繁體中文

水是人類重要的資源，集水區常因密集的農作活動導致水體受污染，特別是NO3（上標 -）。梨山位於德基水庫上游集水區，是台灣重要的蔬菜和水果農業區。本研究除分析梨山農作區相關水體之NO3（上標 -）濃度，以了解該地區受NO3（上標 -）污染之科度外，同時也分析水體中NO3（上標 -）之氮、氧同位素組成，以辨別水體中NO3（上標 -）可能之來源及轉化作用。由水體中NO3（上標 -）之濃度及氮、氧同位素組成特徵值顯示，地表水中NO3（上標 -）之來源主要與降雨及土壤氮源有關；地下水中之NO3（上標 -）可能來自土壤氮源或動物排泄物，而約有52%地下水之NO3（上標 -）濃度高於飲用水水質標準。同位素證據同時顯示硝化作用是梨山農作區地地下水體中NO3（上標 -）之主要輸入作用，而NO3（上標 -）的輸出作用主要為水生藻類同化作用。因此，本研究區地下水NO3（上標 -）之濃度及氮、氧之同位素組成特徵為硝化作用、同化作用及不同氮源之NO3（上標 -）混合的共同作用結果。

Water is an important resource for people and is easily polluted by intensive farming in the watershed area, especially in NO3(superscript -) pollution. For understanding the extent of the pollution from NO3(superscript -), this study analyzed the NO3(superscript -) concentrations of the relevant waters in the Li-Shan agriculture area, which is located in the upstream catchment of Dekie reservoir and is an important cultivation area for vegetables and fruits in Taiwan. In addition, nitrogen and oxygen isotopic compositions of NO3(superscript -) in waters were determined to evaluate the potential sources and transformations of the NO3(superscript -) in water. The nitrogen and oxygen isotopic evidence indicates that sources of NO3(superscript -) in surface waters were mainly related to rainfall and soil nitrogen. Nearly 52% of NO3(superscript -) concentrations of groundwater are higher than the drinking water standard, and most NO3(superscript -) in groundwater was derived from soil nitrogen and animal excrement as evidenced by the isotopic characteristics. The isotopic characteristics indicate that the primary input and output for NO3(superscript -) in groundwaters are nitrification and assimilation, respectively; then, processes of nitrification and assimilation in addition with varied-sources mixing affect the isotopic compositions and concentrations for NO3(superscript -) in groundwaters.