洱海典型小流域丰水期农业面源氮污染来源解析

农业面源污染是近年来导致洱海水质不断恶化的主要因素。选取洱海地区典型小流域,分析了林地、耕地以及居民区地表径流中硝酸盐氮与铵态氮的氮、氧同位素特征,进而解析其来源。结果表明:林地径流中硝酸盐氮来源于大气降雨和土壤的比例分别为8.53%和91.47%,铵态氮来源于大气降雨和土壤的比例分别为19.78%和80.22%;耕地径流中硝酸盐氮来源于大气降雨、土壤和化肥的比例分别为5.90%,68.76%,25.34%,铵态氮则主要来源于土壤;居民区径流中硝酸盐氮来自于大气降雨、生活污水和动物粪便的比例分别为3.32%,55.42%,41.26%,铵态氮则主要来源于生活污水与动物粪便。研究成果为控制洱海流域农业面源污染提供了有效途径。

Sources of Agricultural Non-point Nitrogen Pollution in Typical Small Watershed of Erhai Lake in Abundant Water Period

Agricultural non-point source pollution is the main factor of the deterioration of water quality of Erhai Lake in recent years. We studied the inorganic nitrogen isotope characteristics in the surface runoff of forest land, cultivated land and residential area in a typical small watershed of Erhai Lake. Source analysis of inorganic nitrogen showed that 8.53% and 91.47% of nitrate nitrogen in forest runoff came from atmospheric rainfall and soil, respectively; 19.78% and 80.22% of ammonia nitrogen in forest runoff were from atmospheric precipitation and soil. For cultivated land, 5.90%, 68.76% and 25.34% of nitrate nitrogen came from atmospheric rainfall, soil, and fertilizer, respectively, while ammonia nitrogen mainly came from soil. In residential runoff, 3.32% of nitrate nitrogen was coming from atmospheric rainfall, 55.42% from domestic sewage, and 41.26% from animal feces, while ammonia nitrogen was mainly coming from domestic sewage and animal feces.