Description: We will develop, demonstrate, and optimize a front-end ammonium reactor (NHxR) for the fast, precise, and accurate measurement of gas-phase ammonia (NH3) and particle-phase ammonium ion (NH4+) by fast, high-flow Cavity Enhanced Absorption Spectroscopy (CEAS). We address Focus Area 9, Sub Topic S1.08 Value Proposition: There is a need to measure the total atmospheric NHX load (NH3+NH4+), with significant ecosystem implications including eutrophication, air quality, and indirectly on atmospheric radiative balance. Current NH3 analyzers miss most of the atmospheric NH3 load, present as fine aerosols. The Innovation: The front-end NH4+ reactor cycles between a line that passes gas phase NH3 to the CEAS analyzer, and then a line where NH4+ aerosols are converted to NH3. A key innovation is flow path material, for which the literature is confused, with significant differences between Teflon formulations (factor of 10 difference in adsorption for PFA versus PTFE by one study). This fast, in situ, analyzers, will enable measurements at dramatically lower per sample cost and far greater data density than aerosol samplers. The ability to measure both NH3 and NH4+ sufficiently rapidly will allow characterization of the strong heterogeneity exhibited by these short-lived species with localized emissions. The NHxR is developed in collaboration with Los Gatos Research, a major manufacturer of state-of-the-art trace gas analyzers with extensive market awareness and well-established clients. BRI retains intellectual property to the NHxR and will license the NHxR for manufacture, potentially by LGR. LGR partnership provides significant commercialization advantages. Dr. Leifer (BRI - Team leader), has led multi-institution, multiple-aircraft NASA campaigns. BRI conducts numerous field studies to solve real-world problems, field expertise that aids in solution-development to meet NASA and market needs.

Benefits: The NHxR will interest research labs (academic, industry, agency labs), regulatory agencies (local, state, national agencies), and agriculture, specifically intensive husbandry and poultry operations. The NHxR will be commercially accessible (pricing comparable to typical air quality analyzers) requiring low technical expertise and minimal maintenance and calibration time. The envisioned applications are stationary air monitoring and mobile monitoring on automobiles and/or small airplanes. Commercial agricultural interests include stationary applications in enclosed cow and poultry sheds where concentrations can be far higher than outside ambient - with just the NH3 load (neglecting NH4+) reaching 8 ppm in cattle houses, to 18 ppm in pig houses and to 30 ppm in poultry houses in Northern Europe. Human exposure limits are 25 ppm. Industry trends are for greater agricultural animal density, intensifying these problems. Although workers can wear masks, animals inhale the full atmospheric NHX load. Current analyzers are negatively biased, missing the NH4+ load. An NHxR-CEAS could actively modulate exhaust fans, thus improving worker conditions and livestock health and productivity. Other NHxR opportunities include industrial stack emission monitoring (power plants, refineries) where ammonia is a waste product, but are not a first focus. Other opportunities exist by extension to other sticky gases, such as nitrogen dioxide / nitric acid and sulfur dioxide / sulfuric acid.

A number of NASA satellite platforms are focused on aerosols for which the NHxR can help understand formation mechanisms as well as improving our understanding of the relationship between space-based NH3 retrievals from satellites like AIRS and IASI to total atmospheric ammonia (NHx) load, which is the parameter that impacts ecosystems. Current NASA orbital instruments measuring aerosol products include MODIS, VIIRS, CALIPSO, etc., which will be added to by future missions such as PACE and candidate missions like HySpIRI. In all cases, better understanding of aerosol formation mechanisms and size distributions will improve interpretation of satellite-derived aerosol optical depth, the relationship between environmental controls and aerosol formation (which impacts all other satellite products via atmospheric radiative transfer corrections) and ecosystem impacts. Additionally, there could be future planetary applications. For example, future Titan atmospheric explorer missions where NH3 plays an important role in aerosol formation or even Jupiter's Great Red Spot where NH3 also is proposed to form aerosols. After miniaturization of the NHxR design, it could play a role in future space missions as a front end to a CEAS or other planetary science analyzer.