Insights Into Formation and Aging of Secondary Organic Aerosol From Oxidation Flow Reactors: A Review

Purpose of Review

This review aims to provide a comprehensive examination of oxidation flow reactor (OFR) studies and their applications in both laboratory and field investigations. OFRs play a crucial role in understanding secondary organic aerosol (SOA) formation and aging processes in the atmosphere. By evaluating the advancements and limitations of OFR technology, this review seeks to identify key research directions and challenges for future studies in atmospheric chemistry and air quality research.

Recent Findings

In recent years, OFR has emerged as an encouraging alternative to smog chambers for SOA study. The high oxidative capacity and short residence time of OFR enable its wide application in both laboratory and field studies. Research utilizing OFR has uncovered the critical role of semi-volatile and intermediate-volatility organic compounds (S/IVOCs) in the formation of SOA from various sources, including vehicle emissions, biomass burning, cooking activities, and non-traditional emissions such as volatile chemical products. Notably, field studies have observed considerable variability in the SOA formation potential across different environments globally, generally showing higher formation potential in urban areas compared to rural and forest regions.

Summary

OFR studies have significantly advanced our understanding of SOA formation and aging processes, identifying key precursors, evaluating influencing factors, and quantifying SOA formation potential. However, challenges remain in unraveling detailed mechanisms due to the complexity of SOA sources and properties. Future OFR research should focus on innovations in OFR design, study non-traditional emissions, conduct long-term field observations, develop standardized calibration procedures, and establish SOA yield parameterization schemes for S/IVOCs.