Abstract View
Environmentally Persistent Free Radicals and Reactive Oxygen Species Measurements in the Size-Segregated Ambient Particles Collected at the Highway and Urban Site
BRIAN HWANG, Ting Fang, Randy Pham, Jinlai Wei, Heejung Jung, Manabu Shiraiwa, University of California, Irvine
Abstract Number: 98
Working Group: Health-Related Aerosols
Abstract
Recent studies show people who live close to the highway has about 5 % higher chance of developing dementia and asthma. Although the exact mechanism in how emissions from the highway can cause these adverse health effects are poorly understood, previous studies suggest oxidative stress by reactive oxygen species (ROS) generated from the inhaled particles play an important role in the development of respiratory and neurological illness. Transition metals such as iron and copper which are found to be abundant in the tire/brake wear and road dust particulate matter (PM) can be a significant source of ROS. These transition metals can react with organic hydroperoxides emitted from the tailpipe or hydrogen peroxides in the lung fluid to generate ROS through Fenton-like reactions. Environmentally persistent free radicals (EPFRs) which are stable radicals with similar chemical characteristics as semiquinones are often found in combustion generated PM. EPFRs can also generate ROS through the redox reaction with iron and copper. The exact sources of EPFR and ROS and their abundance near or next to highway PM are hardly quantified.
In this study, PM2.5 and size-segregated ambient particles were collected at the near road sites and urban background location in the South Coast Air Basin using a high volume PM2.5 sampler and a micro-orifice uniform deposition impactors (MOUDI) respectively. EPFRs are directly measured from the particles on filters using an electron paramagnetic resonance (EPR) spectrometer. The preliminary results show EPFRs in the highway PM2.5 are 2 – 4 times higher than the urban background. At the highway site, EPFR concentrations are found to be highly correlated with CO and NO2 mixing ratios, suggesting that EPFRs may be mainly emitted from the tailpipe. Interestingly, negative correlation between EPFRs and O3 was observed, suggesting O3 or photolysis may play a role to quench EPFRs or inhibit their production. We also conducted ROS measurements to measure OH·, O2·, and organic radicals from particle water extracts using EPR combined with a spin-trapping technique.