Solid Aerosol Formation from the Reaction of Ammonia with Greenhouse gases (GHG)

Abstract. Ammonia is perceived to be one of the major precursors to fine particulate matter (PM_2.5) in concentrated animal feeding operations (CAFOs). The contribution of precursor gases to PM2.5 emissions have not been extensively studied in the past and very limited data are available. This study investigates the aerosol formation resulting from the reactions of ammonia with other precursor gases in an experimental concentric flow reactor at ambient conditions. Nonphotochemical reactions were conducted at both dilute and high reactant concentrations to determine the resulting amount of solid aerosol products. Solid aerosols were characterized based on the identified compounds using Fourier Transform infrared analysis and particle size distribution (PSD). Pure gas mixing conditions (w/o air) resulted into a higher average PM production rate of 1.15 mg min^-1at 2% ammonia concentration. A decrease in the production rate was observed in the presence of dry air and carbon dioxide at ambient temperature and pressure. The resulting PM were primarily white crystalline and yellowish in color. Ammonium salts such as its sulfates and sulfites were predominant in all of the PM samples. About 65-95% of the total PM produced belong to the PM2.5 cut. The protocol developed in measuring PM2.5 from precursor gases in the laboratory can be tested on an actual agricultural facility. This can possibly provide an alternative way of measuring actual secondary PM2.5 emissions rather than relying on modelled results for PM2.5 permitting.