Seasonal Variation and Source Contribution to PM2.5 Oxidative Potential and Environmentally Persistent Free Radicals in Atlanta, GA at the ASCENT Site
MINHAN PARK, Ma. Cristine Faye Denna, Kasey Edwards, Ruizhe Liu, Sohyeon Jeon, Seongbin Jo, Anna Kaehr, Nga Lee Ng, Manabu Shiraiwa, Pengfei Liu, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 412
Working Group: Health-Related Aerosols
Abstract
Atmospheric fine particulate matter (PM2.5) is a global concern due to its impact on the environment and human health. Numerous toxicological and epidemiological studies have reported that PM2.5 is strongly associated with adverse human health effects, but variability in sources and physical and chemical properties can affect the associations. Reactive oxygen species (ROS) are an important factor in PM2.5 toxicity, causing oxidative stress and inflammation. Oxidative potential (OP), the capacity of PM to generate ROS, is widely used to assess PM2.5 health-relevant properties. However, as individual assays vary in sensitivity to specific chemical components, the use of multiple assays is necessary for comprehensive analysis of the overall OP of fine particles. This study aims to characterize seasonal variation in PM2.5 chemical composition and OP using the dithiothreitol (DTT) assay for water-soluble (WS) and all (total) PM2.5 and the hydroxyl radical (OH) production assay in synthetic lung fluid, and environmentally persistent free radicals (EPFR) concentrations. Ambient PM2.5 samples were collected in Atlanta, GA from December 2023 to November 2024 at the ASCENT (Atmospheric Science and Chemistry mEasurement NeTwork) site at South DeKalb, providing a suite of PM2.5 chemical speciation data. Volume-normalized water soluble and total- DTT (WS-DTTv and total-DTTv) showed higher values in winter, influenced by combustion-related components. In summer, WS-DTTv notably increased its contribution from 60% to 86% of total-DTTv, indicating enhanced photooxidation effects. Total-DTTv and WS-DTTv were correlated (r>0.5, p<0.05) with BC, NO3-, organics, and K. Total-DTTv was also correlated with Fe, Zn, Cu, CO, and SO2. The OH production assay was correlated with BC, NO3-, Fe, SO2, and NOx. EPFRv was correlated with BC, NO3-, Zn, SO2, CO, and NOx. All OPs and EPFR were correlate with BC (r= 0.6-0.8, p<0.05) and NO3- (r= 0.5-0.7, p<0.05). A multiple regression using sources identified by PMF analysis on Aerosol Chemical Speciation Monitors (ACSM) and real-time metal data was conducted to determine source contribution to OP and EPFR. The results showed that WS-DTTv and total-DTTv were associated with biomass burning organic aerosols (BBOA, 11%-24%), more oxidized oxygenated OA (MO-OOA, 40%-56%), and less oxidized OOA (LO-OOA, 24%-34%). Total-DTTv was also associated with hydrocarbon-like OA (HOA, 11%). The OH production assay was mainly associated with isoprene OA or secondary sulfate aerosols (IsopOA/S, 60%) and dust from brake/road dust from traffic emissions (40%). EPFRv was associated with MO-OOA (53%) and dust (47%). Combustion/traffic-related sources were commonly associated with all assays, suggesting that these sources were an important factor for PM2.5 OP and EPFR at the ASCENT Atlanta site. More results will be discussed in this presentation.