AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
The NOx Effect on the Chemical Composition And DTT Response of Water-soluble Secondary Organic Aerosols
HUANHUAN JIANG, Zechen Yu, Myoseon Jang, University of Florida
Abstract Number: 392 Working Group: Health Related Aerosols
Abstract As a major fraction of particulate matter (PM), secondary organic aerosol (SOA) is supposed to be a significant contributor to the adverse health effects of PM. A well-known toxicity mechanism of PM in biological systems is that its redox activity leads to the production of reactive oxygen species (ROS) and then a cascade of inflammation responses. Metals, quinones, and PAHs are supposed to significantly contribute to the ROS generation. However, there are no metals in SOA, and the amount of quinones and PAHs in SOA are relatively low compared to those in PM. In order to have a deep insight into the mechanisms of SOA toxicity, its compositions and potential toxicity are needed to be characterized. In this study, SOA was produced via the photooxidation of four different hydrocarbons (toluene, 1,3,5-trimethylbenzene, isoprene and alpha-pinene) in the presence of different NO$_x conditions using a large outdoor photochemical smog chamber. The ability of SOA to consume dithiothreitol (DTT), a surrogate biological reducing agent SOA, was used as an indicator of SOA toxicity and estimated by mass-normalized DTT consumption rate, i.e. the DTT activity. The compositions of SOA were characterized by a series of chemical assays, such as the DTT enhancement assay, Griess assay and peroxide assay. The results showed that no significant NO$_x effect observed on the DTT activity of 135-TMB SOA and alpha-pinene SOA. The DTT activity of toluene SOA with relative high NO$_x condition is higher than SOA with low NO$_x conditon. However, the opposite trend appeared with isoprene SOA. The chemical assays showed that concentration of PAN types compounds in aerosol phase was relatively low, and conjugated carbonyls, and peroxides were main contributors to the DTT activity of SOA.