Abstract
In this study, a new assessment of river environment using carbon and nitrogen stable isotope analysis is proposed. The stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in the sediments between river mouth and upstream end are measured at seven rivers in Okinawa Prefecture, Japan. The result indicates that δ15N is affected by nutrient load from catchment area and δ13C is determined by the mixing ratio of terrestrial organic matter. The prediction equations of δ13 C and δ15N in the riverbed sediments are proposed and applied to the observation results. The predicted value have a good agreement with the observed value, indicating that δ13C and δ15N reflect the characteristics of catchment area, and are useful to evaluate the river environment.
