Isotopic studies of nitrates – a short review

Nitrogen is an essential element for life. One of its available forms are nitrates - the compounds playing a key role in the biogeochemical N cycle. However, excessive amounts of nitrates may be harmful to organisms and the environment, therefore in recent years the emphasis is on continuous monitoring of quality of consumed water. Nitrates from different sources have wide, but different ranges δ15N and δ18O. Also researchers observed typical changes in both delta values induced by biological processes and in the case of mixing water with anthropogenic nitrates. This is a reason why the isotopic analysis are often used to identify the source of contamination in a reservoir or to quantitatively describe the processes occurring in an ecosystem.In this review article, we present a model of the global nitrogen cycle, along with the latest data on the disturbances caused by human activity. We describe the processes occurring in the N cycle and biogeochemical mechanisms, which modify the nitrogen isotopic composition in their compounds. We also present a short description of analytical techniques utilized for studying isotopic compositions of nitrates. In addition, we discussed the methods for extraction and preparation of nitrates from freshwater and ocean water, by determining the δ15N,  δ18O and δ17O (or Δ17O) values. The final part is a description of applications of developed techniques for environmental research

Isotopic investigation of nitrates in Horyniec-Zdrój waters

In this work the isotopes of oxygen and nitrogen were determined in nitrates of water samples collected in Horyniec Zdrój and they allowed the preliminary indication of the source of NO3– ion. The obtained δ15N and δ18O values of nitrates dissolved in the Róża III therapeutic water are +2.1, +13.1 ‰, respectively. They indicate the origin of NO3- ion from bacterial decomposition of organic matter which is abundant in the aquifer.Interpretation of the processes affecting the chemical and isotopic composition of investigated waters was possible by taking into account earlier isotopic analyzes as well as chemical composition, geological structure and hydrogeological conditions prevailing in the aquifer. The results and discussion presented in this paper have excluded the possible influence of external contaminants in Horyniec-Zdrój waters used for therapeutic purposes