Research Projects

Recent emissions tests have determined that primary organic aerosols (POA) generated from combustion sources behave like a series of semi-volatile compounds when the particulate phase concentrations range between 100–10,000 µg/m3. The data available for atmospherically relevant concentrations below 30 µg/m3 are sparse and the data below 10 µg/m3 are missing entirely. The simple absorption theory that appears to explain the behavior of gas-particle distribution of condensable organics at high concentrations may not be accurate at atmospherically relevant concentrations. It is likely that other processes such as chemical and physical adsorption onto elemental carbon and partitioning into the aqueous phase play significant roles at lower concentrations. The objective of the proposed research is to identify the dominant partitioning mechanism for POA emitted from diesel- and gasoline-powered vehicles. The results of experiments conducted at atmospheric concentrations will determine if the simple absorption theory can be extrapolated to the real atmosphere. These findings will have broad application within regional air quality models and global climate models used to evaluate the efficiency of emissions control programs on PM.