Sampling systems for isotope‐ratio mass spectrometry of atmospheric ammonia

Abstract

Passive and active ammonia (NH3) sampling devices have been tested for their nitrogen (N) capture potential and δ 15N fractionation effects. Several sampling techniques produced significantly different δ 15NH3 signals when sampling the same NH3 source released from field site fumigation campaigns. Conventional passive NH3‐monitoring systems have shown to provide insufficient N for isotope‐ratio mass spectrometry and various modified devices have been developed, based on existing diffusion tube designs, to overcome this problem. The final sampler design was then tested in a wind tunnel to verify that sampling NH3 in different environmental conditions did not significantly fractionate the δ 15N signal.