【摘要】 硝酸盐（NO₃^-）是北京地下水的主要污染物之一。本文分析了永定河冲积扇不同部位第四系地下水的水化学和氮、氧同位素特征,识别了地下水中NO₃^-的主要污染源,并定量评价了各种源的贡献。研究区地下水的NO₃^--N浓度介于1.32³7.44 mg/L,80%的地下水样NO₃^--N浓度超过我国《生活饮用水卫生标准》（20 mg/L）。地下水的δ15N-NO₃^-值介于+9.38‰⁺16.96‰,均值12.87‰,δ18O-NO₃^-值介于+3.13‰⁺21.18‰,均值+10.39‰,结合反硝化作用的识别,推断地下水中NO₃^-主要来自粪肥,部分来自NO₃^-化肥和大气降水。采用氮、氧同位素和物质平衡混合模型定量评价表明,粪肥对地下水NO₃^-的贡献为58%⁸1%,据此提出了保护和改善地下水水质的建议。更多还原

【Abstract】 Nitrate（NO₃^-） is one of the main contaminants in groundwater in Beijing. In this study,thecharacteristics of hydrochemistry, nitrogen isotope(¹⁵N- NO₃^-) and oxygen isotope(¹⁸O^- NO₃^-) in differentparts of the quaternary groundwater are analyzed in the Yongding River alluvial fan. The contaminant sourc-es of NO₃^-in the groundwater are identified,and the contributions of these different contaminant sources tothe NO₃^-are evaluated quantitatively. The concentrations of NO₃^--N in the groundwater range from 1.32 mg/L to 37.44 mg/L,The concentrations of NO₃^--N in 80% of the groundwater samples exceeded the drinkingwater standarnd of 20 mg/L. The values of15N-NO₃^-in groundwater range from +9.38‰ to +16.96‰ andthe mean value is +12.87‰. The values of18O-NO₃^-in groundwater range from +3.13‰ to +21.18‰ andthe mean value is +10.39‰. Combined with the identification of denitrification in groundwater,NO₃^-mainlycome from manure and partly come from chemical fertilizer and precipitation. Quantitative evaluation withisotope techniques and material balance model shows that manure contributes 58%⁸1% to the concentra-tion of NO₃^-in groundwater. On the basis of this study,the suggestion about how to protect and improvegroundwater quality is recommended.更多还原