This paper is the result of environmental geological survey engineering.

Objective Nitrogen (N) is a key nutrient across Earth's terrestrial ecosystems and one of the pollution elements that cause water eutrophication. Owing to the continuous improvements of analysis and testing techniques, nitrogen stable isotope technology has developed into a common research method and analysis mean, and has been widely used in nitrogen biogeochemical cycle, water eutrophication and groundwater pollution source identification.

Methods In this paper, the relevant literatures on nitrogen stable isotope in the field of ecological environment domestic and overseas in recent years were reviewed, and the research status of nitrogen isotope fractionation mechanism, nitrogen stable isotope analysis technology and nitrogen isotope applications in ecological environment were summarized, the development of remediation technologys of nitrate pollution in groundwater were briefly described.

Results (1) A mature system of nitrogen isotope mass spectrometry and nitrogen isotope tracer technology has been established. (2) Nitrification and denitrification are the main mechanisms of soil nitrogen conversion cycle. Nitrogen input is realized by biological nitrogen fixation, and nitrogen output is mainly through nitrogen gas or ammoniation produced by plants or microorganisms, which is accompanied by different degrees of nitrogen isotope fractionation. (3) Nitrogen isotopes can be used to measure soil nitrogen turnover rates and N₂O emission rates, improve biological nitrogen fixation, indicate changes in atmospheric nitrogen deposition, investigate the interaction between plant and soil and determine nitrogen uptake and utilization by plants, and identify crop area sources and pollution in groundwater and atmosphere.

Conclusions Future researches should focus on improving the ability of quantitative detection of uncertainty sources in the nitrogen cycle, identifying undiscovered nitrogen input, accumulation and loss pathways, and perfecting and developing ecosystem nitrogen cycle model.