|Van Rooy, Paul - University Of California|
|Purvis-roberts, Kathleen - Claremont Colleges|
|Silva, Philip - Phil|
|Cocker Iii, David - University Of California|
Submitted to: American Association for Aerosol Research
Publication Type: Abstract Only
Publication Acceptance Date: 6/14/2019
Publication Date: 10/17/2019
Citation: Van Rooy, P., Purvis-Roberts, K., Silva, P.J., Cocker Iii, D. 2019. Oxidation of reduced sulfurs and amines: Characterization and mechanism development. American Association for Aerosol Research. Paper No. 12AC.4.
Technical Abstract: Gas-phase amines (trimethylamine, diethylamine, butylamine, ammonia) and reduced sulfur compounds (dimethysulfide, dimethyldisulfide) are both present over agricultural land and are both thought to be important to new particle formation and particle growth. Despite this, there is a lack of knowledge on how these compounds oxidize in the atmosphere individually nor is there a mechanism by which these compounds interact to form aerosol. To begin to fill this information gap, a 37.5 cubic meter Teflon chamber was utilized to run hydroxyl radical and nitrate radical oxidation experiments of each compound individually as well as interaction experiments containing at least one amine (100ppb) and one reduced sulfur (100ppb). Methanesulfonic acid is considered an important product of reduced sulfur oxidation however, under extreme dry conditions and in the presence or absence of NO_x, methanesulfonic acid did not form. Measurements made using the HR-TOF-AMS present sulfur-containing organic fragments, such as C_2 H_6 S and C_2 H_6 SO, that cannot be explained by the current mechanism. Only when humidity as well as NO_x was introduced into the chamber did methanesulfonic acid form. Interestingly, precursor decay was much faster in the presence of NO_x, indicating that O(^3 P) plays an important role in oxidation of reduced sulfurs during chamber experiments, which are often run at high NO_x concentrations. Addition of an amine to the system allows for MSA formation under dry, NO_x-free conditions. Interactions between amines and reduced sulfur compounds results in aerosol mass concentrations up to 10 times higher than individual precursor oxidation. The addition of humidity to interaction experiments resulted in up to 4 times the mass formed during dry experiments. An updated mechanism for reduced sulfur oxidation is proposed along with a particle-forming mechanism for amines in the presence of reduced sulfurs.