Laboratory-based validation of a passive sampler for determination of the nitrogen stable isotope ratio of ammonia gas

Abstract

Nitrogen stable isotope ratio (δ15N) analysis of ammonia gas (NH3) by using a passive sampler is expected to be useful for determining sources of NH3 and for examining environmental dynamics. However, the use of passive samplers for determining the δ15N values of NH3 obtained has not been well validated in laboratory. Here, we evaluated the reliability of the passive sampler under various simulated environmental conditions in the chamber. When the amount of NH3 collected by the sampler was <70 μg, the δ15N value obtained was approximately 10–15‰ lighter than the δ15N value of a reference NH3 gas value regardless of type of passive sampler, the temperature, or sampling chamber size. Thus, when using a passive sampler to collect NH3, if the amount of NH3 collected is < 70 μg, it is necessary to add approximately 10–15‰ to the measured value. This finding will enable determination of more accurate δ15N values, which will be meaningful for future air research.