Nitrogen and oxygen isotope measurements of nitrate to survey the sources and transformation of nitrogen loads in rivers

This paper reviews the studies on evaluation of river environments in terms of water pollution, ecosystem disturbances, excess nutrient (nitrogen) loads, and developments in the isotopic measurements of nitrate and present an update and future perspectives regarding the application of nitrate isotopes to river nutrient assessments. Then, we present the advantages of simultaneous measurement of the nitrogen and oxygen isotopes of nitrate in streamwaters.Dual isotope measurement has recently been used to identify the sources and paths of nitrogen loading in several stream systems. The most recently developed high-resolution denitrifier method is a promising tool with which to investigate the detailed spatial and temporal variation and mechanisms of nitrogen loading and transformation in rivers