Preliminary insights into δ15N and δ18O of nitrate in natural mosses: A new application of the denitrifier method

Natural mosses have been employed as reactive and accumulative indicators of atmospheric pollutants. Using the denitrifier method, the concentration, delta N-15 and delta O-18 of moss nitrate (NO3-) were measured to elucidate the sources of NO3- trapped in natural mosses. Oven drying at 55-70 degrees C, not lyophilization, was recommended to dry mosses for NO3- analyses. An investigation from urban to mountain sites in western Tokyo suggested that moss (NO3-] can respond to NO3- availability in different habitats. NO3- in terricolous mosses showed isotopic ratios as close to those of soil NO3-, reflecting the utilization of soil NO3-. Isotopic signatures of NO3- in corticolous and epilithic mosses elucidated atmospheric NO3- sources and strength from the urban (vehicle NOx emission) to mountain area (wet-deposition NO3-). However, mechanisms and isotopic effects of moss NO3- utilization must be further verified to enable the application of moss NO3- isotopes for source identification. (C) 2011 Elsevier Ltd. All rights reserved.