Methods for the Determination of Stable Isotope Ratios of Multiple Nitrogen Species in Rainwater Using Distillation and Evaporation

Nitrogen (N) isotope ratios (δ 15 N) of multiple N species including ammonium (NH 4 + ), nitrate (NO 3 − ), dissolved organic N (DON), and total dissolved N (TDN) can serve as indicators of the sources of wet N deposition. However, methods for sequential analysis of these multiple N species are not well developed. In this study, methods for the determination of δ 15 N of these multiple N species were proposed through a traditional distillation method for NH 4 + and NO 3 − , direct evaporation for TDN, and an isotope mass balance equation for δ 15 N-DON. A series of experiments were conducted 1) to find evaporation conditions including pH (