Environmental Sciences Department Seminar

Isoprene emitted by the biosphere is the largest biogenic portion of the global budget of volatile organic compounds (VOC). Isoprene in the atmosphere is predominantly oxidized by the hydroxyl radical (OH). The oxidation of VOCs in the atmosphere contributes to the creation of ozone and secondary organic aerosol (SOA). Recent theoretical predictions and measurements have shown that small carbonyl compounds such as glyoxal, methyl glyoxal, hydroxyacetone and glycolaldehyde may be produced as co-product pairs from rapid isomerization of peroxy radicals in the first generation of isoprene oxidation. We investigated the temperature (260K, 298K and 330K) and NOx (near-zero NOx and high NOx (ppm level)) dependence of the first generation product yields from these isomerization pathways, and the implications of these findings on our understanding of the oxidation mechanism. Experiments combine the atmospheric simulation chamber at the National Center for Atmospheric Research with the CU Light Emitting Diode Cavity Enhanced Differential Optical Absorption Spectroscopy (CU LED-CE-DOAS) for the detection of glyoxal and methyl glyoxal; as well as Proton Transfer Reaction Mass Spectrometry for the detection of other isoprene oxidation products.