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, δ15N and δ18O of moss nitrate (NO3−) were measured to elucidate the sources of NO3− trapped in natural mosses. Oven drying at 55–70 °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.

► Plant [NO3−] has been used to get insights into forest N saturation.
► However, detailed protocols were not established for plant [NO3−] analysis.
► Moreover, nitrogen/oxygen isotopic ratios of plant NO3− cannot be measured.
► We developed a new protocol for concentration and isotopic measurement of plant NO3−.
► The new method can open a new window to use these parameters for NO3− physiology.