稳定同位素识别水体硝酸盐污染来源的研究进展

水体硝酸盐污染已经成为一个世界性的水质问题。为了确保供水安全和有效治理水环境中硝酸盐污染,准确识别水体中硝酸盐的污染来源显得尤为重要。近年来,硝酸盐稳定氮(δ15 N)和氧(δ18 O)同位素示踪技术被广泛用于识别水环境中硝酸盐的污染来源。然而,水环境中硝酸盐污染来源的复杂性和同位素分馏的影响,致使该项技术的应用存在一定的局限性。概括了硝酸盐中的δ15 N和δ18 O的典型值域范围,阐述了多种同位素技术联合识别水体中硝酸盐污染来源的方法以及应用模型定量解析硝酸盐污染源贡献率,最后,对该领域未来的发展方向进行了阐述。

RESEARCH ADVANCES IN IDENTIFYING NITRATE POLLUTION SOURCES OF WATER ENVIRONMENT BY USING STABLE ISOTOPES

Nitrate (NO₃^-) contamination of surface water and ground water is an environmental problem in many regions across the world. Nowadays, with rapid industrialization, economic and population growth and intensive human activities (such as the discharge of industrial and domestic sewage, increased use of N-containing organic and inorganic fertilizers, animal manure, leakage of fossil fuels, etc.), the concentration of nitrate has raised increasingly and posed a serious threat to water environment, thereby causing the widespread concern of hydrological ecologists. Increased nitrate concentration in the water body has a serious impact on human health and environments. In order to safeguard drinking water supplies and control contamination effectively, it is of great importance to effectively identify the nitrate pollution sources of water body. Nitrate pollution originates from multiple sources via different pathways as point or diffuse sources: mineral nitrogen fertilizers and animal manure in agriculture, domestic or industrial nitrogen-bearing wastewater, atmospheric deposition, mineralization of soil organic nitrogen and biological nitrogen fixation. The traditional methods to identify the nitrate pollution sources are by investigating land use types of study area and combining the characteristics of local water chemistry, however, the results are relatively rough. In recent years, stable nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) isotope data of NO₃^- have been frequently used to identify NO₃^- sources in water environment, because the isotopic composition of N and O in NO₃^- is generally different among various NO₃^- sources such as atmospheric N₂, soil, chemical fertilizers, and sewage and manure. Nevertheless, the stable isotope technology also has limitations because of the multiple NO₃^- sources and isotope fractionation caused by N-transformation processes. This review systematically summarizes the typical δ¹⁵N and δ¹⁸O-NO₃^- ranges of known NO₃^- sources, introduced the multiple isotope technology combined to identify NO₃^- sources in water environment, and presents mixing models and future development directions to quantify the contributions of different NO₃^- sources. Based on the previous researches about the application of stable isotope methods, we suggest that in the future it is important to combine multiple isotope technology to identify NO₃^- sources in water environment. In addition, future research hotspot will be quantification of the contribution of different sources of NO₃^- by using stable isotopes simultaneously, in combination with mathematical models.