Chemistry Department 5011 Seminar

Thursday, March 4, 2021

Habeeb Al-Mashala

Formation and Fate of a Newly Identified Species from the Oxidation of Dimethyl Sulfide

Dimethyl sulfide (DMS) from marine sources is emitted into the atmosphere and oxidized into one of several chemical species, including sulfuric acid, which plays an important role in the formation of atmospheric particle and their subsequent growth into cloud condensation nuclei. However, the branching ratios and the lifetimes of these species in models developed for the oxidation mechanism of DMS are variable, leading to uncertainty on their climate effects as well as implications to atmospheric models. Using data obtained from NASA’s Atmospheric Tomography Mission flights, the presence of hydroxyperoxymethyl thiformate (HPMTF) predicted by theory has been discovered in abundance in the marine boundary layer. HPMTF has been shown to be a significant reservoir of sulfur in the atmosphere, and it may also contribute to enhancing the formation of new atmospheric particles. The formation of HPMTF from the methylthiomethylperoxy radical has also been investigated computationally and involves a hydrogen shift. While HPMTF is abundant in the atmosphere, it is an intermediate which terminates to sulfur dioxide and undergoes fast uptake into clouds. All of this contributes to a better understanding of the chemistry in the marine atmosphere, the sulfur cycle, and its relation to cloud formation.