Partitioning of Reactive Oxygen Species Among Indoor Surfaces

Zhenduo Yao, GLENN MORRISON, UNC-Chapel Hill

     Abstract Number: 487
     Working Group: Indoor Aerosols

Abstract
The presence of peroxides, ozonides and other reactive oxygen species (ROS) has been observed on indoor surfaces. Initiated by ozone and possibly other oxidants, ROS has been shown to form on surfaces coated with skin lipids and cooking oils. Models predict that some of the ROS formed have physico-chemical properties that allow them to partition from indoor surfaces to aerosols. This process can thereby lead to inhalation exposure of indoor-generated ROS, and the possibility of deposition deep in the respiratory system. In this research, we explored the potential for ROS formed on indoor surfaces to partition via gas-phase transport to a separate condensed phase. A simulated surface lipid mixture (SLM), comprising squalene, fatty acids, triglycerides, and cholesterol was applied to a glass slide and was exposed to ozone in a reactor at ozone concentrations ranging from 100 to 350 and times from 2-16 h. After exposure, a second glass plate coated with dioctyl sebacate (DOS) was positioned 1mm above the SLM coating in a custom frame for several hours. ROS formed on the SLM coating at a molar yield (ROS formed/ozone deposited) of 0.5. ROS that partitioned to the DOS film was not strongly associated with ROS on the SLM. We observed an inverse relationship between partitioned ROS (in the DOS film) and the ozone concentration during the SLM exposure, for the same exposure time. For all conditions, we observed a positive relationship between partitioned ROS and the ratio of ozone deposited to ozone concentration. This suggests that ozone itself forms ROS that is less likely to partition, while other processes, perhaps autoxidation, form ROS that is more likely to partition.