Environmentally Persistent Free Radical Formation and Correlation with Ambient Pollutants in Fairbanks, Alaska during the ALPACA Campaign

KASEY EDWARDS, Sukriti Kapur, Ting Fang, Meeta Cesler-Maloney, Yuhan Yang, Ellis Robinson, Peter F. DeCarlo, Rodney J. Weber, William Simpson, Manabu Shiraiwa, University of California, Irvine

     Abstract Number: 534
     Working Group: Aerosol Exposure

Abstract
Environmentally Persistent Free Radicals (EPFRs) play an important role in chemical transformation of atmospheric aerosols and may cause adverse health effects due to their redox activity to produce reactive oxygen species (ROS). EPFR production and stabilization can be enhanced by environmental factors such as the presence of metals, combustion sources, and photochemistry. This study investigated the generation of EPFRs within a subarctic climate from ambient outdoor samples collected in Fairbanks, Alaska as part of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Campaign. Subarctic conditions in Fairbanks including reduced temperature and daylight hours may also affect the formation of particulate matter and chemical processes in the atmosphere. Daily EPFR concentrations were determined using EPR analysis of collected PM2.5 samples. A high volume Tisch PM2.5 sample collected filter samples for 23.5 hours daily. EPFR concentrations were on average 18±12 pmol m^-3, ~1.5 times higher than suburban concentrations but ~2 times lower than that found near a Southern California highway. EPFR concentrations in Fairbanks were found to equate to smoking one cigarette every two days in the winter. EPFR concentrations were well correlated with primary pollutants including carbon monoxide, nitrogen oxides, sulfur dioxide, and potassium (> 0.7 R²), indicating that EPFRs were associated with incomplete combustion and traffic emissions. EPFRs were found to be anti-correlated with O3 (> 0.6 R²). They were also found to correlate well with iron and titanium (> 0.6 R²), which is consistent with previous studies showing that EPFRs can be stabilized by transition metals. When looking at correlations of EPFR molar concentrations per particle mass, NOx remained the highest correlation, although substantially lower (> 0.3 R²). Our results indicate that although traffic and combustion sources are mostly likely the primary sources of EPFR generation, meteorological conditions strongly influence EPFR concentrations.