Online Water-to-Air Ammonia and Amine Flux Measurement System using Chemical Ionization Mass Spectrometry
CHRISTINE TROLLER, Coty Jen, Carnegie Mellon University
Abstract Number: 76
Working Group: Instrumentation and Methods
Abstract
Ammonia (NH₃) and alkylamines play critical roles in atmospheric aerosol chemistry, influencing cloud formation, Earth's radiative balance, and air quality. Despite significant contributions from water-based sources, associated emissions of ammonia and alkylamines remain poorly characterized, especially in freshwater environments. Here, we present a novel flux measurement system (FMS) coupled with a hydronium chemical ionization mass spectrometer (CIMS) for real-time quantification of ammonia and alkylamine (i.e., methylamine, dimethylamine, and trimethylamine) fluxes from water samples up to 16 liters in volume. The FMS CIMS system overcomes challenges associated with the high polarity of these compounds, allowing for online gas-phase measurements with minimal sampling loss. We validate the system using model solutions under varying operational conditions and characterize the fluid dynamics within the FMS. Flux experiments were conducted using aqueous solutions with total liquid concentrations of ammonia and alkylamines ranging from 10-5 to 10-9 M, carrier gas varying from 2.9 to 29 cm min-1, and model solution volumes of 8 and 16 liters, to assess how these parameters influenced flux. We compare measured fluxes to theoretical fluxes predicted by Henry’s Law, which best represents the conditions inside the FMS. The FMS was also used to evaluate ammonia and amine contamination in reverse osmosis water. Our findings demonstrate that the FMS CIMS can reliably capture water-to-air fluxes of ammonia and alkylamines, filling a crucial gap in understanding aquatic contributions to atmospheric nitrogen chemistry. This system provides a useful new tool for investigating gaseous fluxes in aquatic systems, with important implications for atmospheric modeling and environmental health assessments.