中文摘要：

土壤原生氮、无机化肥和动物粪便等氮源中δ^15N富集程度存在差异，使得利用稳定同位素N（δ^15N／^14N）能有效识别地下水中NO3^-的来源。但N不是一个稳定的示踪剂，地下水中NO3^-的占δ^15N是N源的初始δ^15N值、后期进入含水层的迁移路径中和地下水流运动途径中不同形态的N之间相互转化过程，如矿化、吸附、硝化和反硝化作用，发生的同位素分馏作用后的综合反映。利用地下水中NO3^-的δ^15N确定其来源必须首先确定分馏作用是否发生及其反应程度。本文重点探讨了判断分馏作用是否发生及其反应程度的方法，总结了N同位素判别地下水NO3^-污染源方法的发展历程，并指出未来研究工作应该以硝酸盐在包气带中的迁移转化规律为重点。

英文摘要：

Stable isotopes of N （^15N/^14N） are broadly used in examining the source of nitrate in groundwater due to the difference of ^15N natural abundance of its contamination sources, e. g. , manure, soil and chemical fertilizer. Nevertheless, nitrogen is not a conservative tracer as its value is a function of its source and isotope fractionation by mineralization, adsorption, nitrification and denitrification that may occur during its generation or groundwater transportation. To identify the source of contamination, it is important to estimate whether the fractionation reaction has happened and what the extent is. In this article, we attempt to synthesize the existing techniques using N and O isotopes as indicators of contamination sources. Various methods of ascertaining existence and extent of the fractionation reaction are discussed. Further research is highlighted to improve the data collection and analysis when integrated N cycle and the water cycle are studied. Understanding of the transport and transformation processes of NO3^- in the unsaturated zone is also emphasized.