Thermochemical, Cloud Condensation Nucleation Ability, and Optical Properties of Alkyl Aminium Sulfate Aerosols

Alkyl aminium sulfates have been postulated to constitute important components of nucleation and accumulation mode atmospheric aerosols. In this study we present laboratory data on the thermochemical, cloud condensation nuclei (CCN) activity, and optical properties of selected aminium sulfate compounds of atmospheric relevance (monomethyl aminium sulfate (MMAS), dimethyaminium sulfate (DMAS), trimethylaminium sulfate, monoethylaminium sulfate (MEAS), diethylaminium sulfate (DEAS), and triethylaminium sulfate (TEAS)). We found that the vapor pressure of these aminium salts is 1-3 orders of magnitude lower than that of ammonium sulfate and as such they can contribute to new aerosols and secondary aerosols formation. We infer that these species have very high CCN activity, with hygroscopicity parameter that is similar to that ammonium sulfate. Finally, between 360 and 420 nm, these aminium sulfate salts scatter light less efficiently than ammonium sulfate, and do not absorb light. These derived parameters can contribute to the better understanding and characterization of the role that these compounds play in atmospheric chemical reactions, gas-solid partitioning and their possible contribution to the microphysical and radiative effects of atmospheric aerosols.