Investigating the Low-NOx Isoprene Oxidation Pathway Through the First Generation Product: ISOPOOH
Tuesday, 16 December 2014
Our current understanding of oxidative processes in the atmosphere is guided by measurements of directly-emitted volatile organic compounds (VOCs) and their oxidation products. Mechanisms for this oxidation have been proposed based on these measurements. These mechanisms usually fall into two regimes: high-NOx and low-NOx (NOx = NO + NO2). High-NOx mechanisms are typical of urban environments while low-NOx mechanisms tend to dominate rural or remote areas. Understanding the low-NOx pathway presents a unique challenge. The first-generation products of this pathway are organic hydroperoxides. This class of atmospherically-relevant compounds are not commercially available and the synthetic methods used to prepare them are still underdeveloped. This work focuses on the synthesis and measurement of several isomers of isoprene hydroxyhydroperoxides (ISOPOOH), the main first-generation products of the low-NOx isoprene oxidation pathway. We present work that demonstrates that ISOPOOH is an interference in both GC and PTR-MS measurements, appearing as product of the high-NOx oxidation pathway. We suggest a possible mechanism for this interference and also discuss the implications of this interference on studies of OH reactivity, O:C ratios, OH recycling and SOA potential for these compounds. We also present results of the experiments investigating air-water partitioning and the condensed phase chemistry of these compounds.