The reactive chemistry of isoprene, the most abundant hydrocarbon emitted by the biosphere, has a controlling influence on the composition of the global atmosphere. We present here a unique dataset concerning the production of two major isoprene photooxidation products, methacrolein (MACR) and methyl vinyl ketone (MVK), over a range of atmospherically relevant nitric oxide (NO) levels. The chemical regime studied is intermediate between the typical ‘high-NO’ and ‘zero-NO’ limits typically studied in chambers, but that is constantly encountered in environments with intertwined biogenic and anthropogenic emissions and remains poorly characterized. The yield of MVK is enhanced by up to a factor of two whereas  the MACR production is rather constrained as NO approaches parts per trillion level. This NO-dependent behavior demonstrates that the interconversion and isomerization of isoprene peroxy radicals effectively compete with their bimolecular reactions at extended peroxy lifetimes. Simulations with a chemical transport model reveal that this thermodynamic controlled distribution of isoprene peroxy radicals that favors the production of MACR and MVK prevails over the majority of the Continental United States.  <br/><br/>

Probing isoprene photochemistry at atmospheric relevant nitric oxide levels

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.