天然水中硝酸盐氮氧同位素测试技术研究进展

Advances of the research of isotopic analysis technology for nitrate in natural water

水环境的硝酸盐污染是一个全球性环境问题。识别水环境中硝酸盐的来源及其转化,对更好地管理水质是十分重要的。硝酸盐的稳定氮氧同位素组成可有效识别水环境中NO 3-来源及其转化。本文总结了典型的测定硝酸盐中稳定氮氧同位素组成的方法:石墨燃烧法、AgNO3-离子交换法、细菌反硝化法、亚硝酸盐去除联合细菌反硝化法、两步化学还原法、连续选择性细菌还原法,同时对这些方法的优缺点进行了评述。最后分析了检测技术中存在的共同问题及其发展方向:δ18O精确度仍有提高的潜力;把NO 3-从水中独立提取出来进行三氧同位素的测试方法还需改进和提高;水样的采集、保存有待进一步改进。

Nitrate pollution in water environment is a global environmental problem.It is very important for managing water quality to identify the source and transformation of nitrate in water,which could be identified with the help of the nitrogen and oxygen isotope composition of nitrate.The typical measurement methods for nitrate nitrogen and oxygen isotope composition are summarized as follows： graphite combustion,AgNO3-ion exchange method,bacterial denitrification method,the method combined bacterial denitrification with nitrite removal in water,two-step chemical reduction method and the bacterial reduction method with sequential selection,and the advantages and disadvantages of the above methods are commented.The existed problems and the development aspects of the isotopic analysis technology for nitrate are analyzed as following： It is of the potential to improve the measurement precision of δ^18O;The triple oxygen isotope analysis of nitrate should be enhanced;The collecting and saving technique for water samples should be further improved.