Present limitations and future prospects of stable isotope methods for nitrate source identification in surface- and groundwater

• Published in: Water research (Oxford) Vol. 43; no. 5; pp. 1159 - 1170
• Main Authors: Xue, Dongmei, Botte, Jorin, De Baets, Bernard, Accoe, Frederik, Nestler, Angelika, Taylor, Philip, Van Cleemput, Oswald, Berglund, Michael, Boeckx, Pascal
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2009; Elsevier
• Subjects: accuracy; Analysis; Applied sciences; cadmium; Chemical Fractionation; Exact sciences and technology; Groundwater; groundwater contamination; intensive farming; Isotope Labeling - methods; Kinetics; literature reviews; Nitrate; nitrates; Nitrates - analysis; nitrogen; Other industrial wastes. Sewage sludge; oxygen; point source pollution; Pollution; population density; Soil; Sources; Stable isotopes; Surface water; Wastes; water analysis; water pollution; water quality; Water Supply; Water treatment and pollution; World; Nitrate; Groundwater; Sources; Stable isotopes; Analysis; Surface water; Isotopic analysis; Uncertainty; Pollutant behavior; Identification; Nitrates; Nitrogen; Modeling; Water quality; Denitrification; Agriculture; Water pollution; Ion exchange; Population density; Speciation; Ground water
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2008.12.048

Nitrate (NO 3 −) contamination of surface- and groundwater is an environmental problem in many regions of the world with intensive agriculture and high population densities. Knowledge of the sources of NO 3 − contamination in water is important for better management of water quality. Stable nitrogen ( δ 15N) and oxygen ( δ 18O) isotope data of NO 3 − have been frequently used to identify NO 3 − sources in water. This review summarizes typical δ 15N- and δ 18O-NO 3 − ranges of known NO 3 − sources, interprets constraints and future outlooks to quantify NO 3 − sources, and describes three analytical techniques (“ion-exchange method”, “bacterial denitrification method”, and “cadmium reduction method”) for δ 15N- and δ 18O-NO 3 − determination. Isotopic data can provide evidence for the presence of dominant NO 3 − sources. However, quantification, including uncertainty assessment, is lacking when multiple NO 3 − sources are present. Moreover, fractionation processes are often ignored, but may largely constrain the accuracy of NO 3 − source identification. These problems can be overcome if (1) NO 3 − isotopic data are combined with co-migrating discriminators of NO 3 − sources (e.g. 11B), which are not affected by transformation processes, (2) contributions of different NO 3 − sources can be quantified via linear mixing models (e.g. SIAR), and (3) precise, accurate and high throughput isotope analytical techniques become available.