Post Date: 27 January 2022

Characterization of oxygenated organic molecules in Hong Kong: sources, formation and impacts

Abstract

Nucleation and particle growth are two critical processes that contribute to secondary organic aerosol (SOA) and therefore affect human health and climate. Oxygenated organic molecules (OOMs) are recently discovered to drive the early particle growth and significantly contribute to SOA formation, but their components, precursors, formation pathway and role in the particle growth process remains unclear. Here, we investigate the schemes from volatile organic compounds (VOCs) to OOMs, and further to SOA by integrating insights from field campaign, chemical mechanisms and aerosol growth model. Based on the understanding of OOMs formation pathway, two swift methods are developed to identify OOMs functional groups and precursors using their molecular information. And about 68% of OOMs can be tracked and categorized as carbonyls (8%), hydroperoxides (7%), nitrates (17%), peroxyl nitrates (10%), di-nitrates (13%), ring-retaining species (6%) and terpenes (7%). We also show that the oxidation of anthropogenic VOCs dominates OOM formation, with ca. 40% contribution from aromatics, and another ca. 40% contribution from alkanes. A new particle formation (NPF) case study demonstrates that OOMs play a dominant role in the growth process of particles between 20 and 70 nm and could constitute 68 % of the SOA mass growth. Overall, our research overviewed the characteristics of OOMs in Hong Kong and highlighted OOMs position in the particle growth process.