人為活動對淡水河流域溶解氮濃度空間變異之影響

經濟合作暨發展組織發布的政策重點中敘述了水體污染的氮排放到水體的量從2000年到2050年將增加35%-46%。臺灣河川的單位面積溶解無機氮輸出居世界之冠，且主要受到人口密度的影響，但較少針對其污染來源之研究。本研究先以基隆河為例，在2017年10月24日至2018年3月27日間，于基隆地區設置36個測站，每月量測電導度及凱氏氮，探究河川流經都市對水質的影響；再以2009年7月于淡水河全流域所採集之水樣，分析其硝酸鹽之氮氧同位素之空間變異，探究河水中之污染來源。相關研究成果將可提供環境政策制訂時的參考，進一步對河川氮排放量的減少有所貢獻。結果發現基隆地區的水質項目中電導度與森林有高度負相關，卻與建築、公共遊憩等土地利用有正相關的趨勢，顯示水中離子濃度變化受到人為活動程度之影響；而在凱氏氮則與人口密度、建築、其他類土地利用在spearman等級相關係數中有相對高的相關性，基隆地區水質的空間變異無明顯趨勢，推測受到污水接管程度之影響，暗示污水接管對改善水質之影響，氮排放量計算結果發現，基隆地區以大武崙、深澳坑溪的單位面積排放量最高。淡水河流域硝酸鹽的氮氧同位素分析結果發現，河水中的硝酸鹽其可能來源主要來自於尿素氮肥、土壤氮及糞便或污水管線三種端源，當集水區人口密度高於50人/平方公里，水質有受到糞便或污水管線來源之影響，反之則主要來自於尿素氮肥或土壤氮，此結果可做為未來環境管理的參考依據。

關鍵字

氮；同位素；淡水河；基隆河； d18O ； d15N

並列摘要

OECD had published that the nitrogen flux from land to water will increase by 35%-46% in 2000 to 2050. The yields of dissolved inorganic nitrogen for rivers in Taiwan are among the highest in the world, controlled by the population density. However, there are relatively rare studies investigating the sources of nitrogen in the water. In this study, the Keelung area was firstly used as an example aiming to realize spatial variations in dissolved nitrogen concentration. Monthly water samples were taken at 36 stations from 2017/10/24 to 2018/3/27, and electric conductivity (EC) and Kjeldahl nitrogen (TN) was measured. Second, the basin-wide water samples were taken in Danshui Watershed in 2009/7, and d15N-NO3 and d18O-NO3 were measured to identify the source of nitrogen. The results revealed that EC were negatively correlated to forest land use but positively correlated to building and public land use, indicating the contributions of human activities to the ions in river. In terms of the Spearman's rank correlation coefficient, it was found that TN was more positively linked to population density, building, and land use defined as others in the land use map. It was found that the treatment of sewage may be one of the factors reducing the nitrogen concentration in Keelung river. As for the pollution source identified by 15N-NO3 and 18O-NO3, the nitrate in the water mainly came from NH4+ fertilizer, sewage and waste, and soil. When the population density within watershed was more than 50 people/ km2, the signature of sewage and waste can be found in the water. On the other hand, when population density was less than 50 person/ km2, the water quality was more influenced by NH4+ fertilizer and soil.

並列關鍵字

Nitrogen ； isotope ； Danshui river ； Keelung river ； d18O ； d15N

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人為活動對淡水河流域溶解氮濃度空間變異之影響

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