Emissions, sinks and gas to particle conversion of amines and ammonia

Abstract:

Nitrogen-containing base compounds, amines and ammonia, play important roles in formation of secondary aerosols in the atmosphere, but their sources, sinks and atmospheric transformation processes are not well understood. Also, there are very limited analytical methods that are capable of measuring pptv or sub-pptv level of amines and ammonia. We have developed a chemical ionization mass spectrometer (CIMS) that can detect amines and ammonia at the pptv and sub-pptv level with a 1 min of integration time. Here, we report ambient measurements of amines and ammonia made in a moderately polluted continental site (Kent, Ohio) and in a rural Southeastern U.S. forest (Centreville, Alabama). Our finding indicate that there are much more abundant gas phase amines (C1-C6) and ammonia in the polluted site than in the rural forest, highlighting the importance of constraining anthropogenic emission sources of amines. At both locations, concentrations of these base compounds show clear temperature dependence, indicating strong gas-to-particle conversion processes. Compared to ammonia, amines can partition into aerosol phases even more effectively due to lower saturation vapor pressures. Measurements in the clean rural forest show that transported biomass burning plumes are the major source of amines. These nitrogen-containing compounds effectively undergo wet deposition in the atmosphere due to high solubilities.