Developments in the investigation of nitrogen and oxygen stable isotopes in atmospheric nitrate
Shah Saud, Shah Fahad, Shah Hassan
Abstract
Under the influence of human activities and the rapid development of industry and agriculture, atmospheric nitrate (NO−3) pollution is becoming increasingly serious and has become an environmental problem worldwide. The stable isotopic composition of atmospheric NO−3 (δ15N, δ18O, and Δ17O) can provide a strong basis for understanding the atmospheric nitrogen cycle to effectively control atmospheric NOx pollution. In this work, the δ15N values associated with different sources of atmospheric NO−3, the seasonal variation characteristics of δ15N-NO−3, and the main influencing factors are reviewed. The δ18O and Δ17O values of different oxidants in the atmosphere and the spatiotemporal distribution characteristics and possible influencing factors of the δ18O and Δ17O values of atmospheric NO−3 are summarised. In addition, key advances in NO−3 isotopic analysis technique is reviewed. Based on previous work, it is suggested that more attention should be given to the oxidative formation mechanism of NO−3 (spatio-temporal differences in the isotopic compositions of different types of oxidants), the δ15N composition of different NOx sources, and the processes of formation, transport, depositional/chemical loss ofatmospheric NO−3 with the help of observation and chemical models.