Emissions within the three major valleys of the Wasatch Front are expected to be heterogeneous, with the largest urban emissions in the Salt Lake Valley and the largest agricultural emissions in the Cache Valley. Aircraft flights across all 3 valleys at different times of day will characterize the spatial distribution of NH3, HNO3 and NOx, together with the key intermediates in NOx oxidation. Comparison of these data to thermodynamic aerosol models will help to determine which reagents are limiting and where. Further, the aircraft measurements at different times of day will characterize transport of trace gases and aerosols, to assess the efficiency of residual layer transport in the distribution of pollutants and / or inter-valley coupling.
Morning, afternoon and night flights will characterize the chemical and meteorological evolution of boundary layer breakup, re-establishment, and overnight residual layer chemistry and transport. Rates of chemical reactions may be a strong function of altitude at all times of day. Vertical profiles will probe this chemical composition for an integrated analysis of boundary layer structure and chemistry.
Flights over large bodies of water at various altitude ranges should be feasible. These flights will characterize the vertical structure of winds over the lakes the transport pollutants, as well as the chemical composition at different altitudes.
Deployment of the AMS will provide unprecedented detail in the measurement of organic aerosol composition to the northern Utah valleys. Furthermore, the iodide CIMS instrument will provide measurements of oxygenated organic and nitrogen containing compounds that are characteristic of residential wood combustion sources. The spatial distribution of these organic aerosol and oxygenated VOCs, together with the daily time evolution, will provide accurate data on the primary and secondary organic aerosol source from residential wood combustion.
Aircraft measurements can be compared to emissions inventories developed by UDAQ to assess the emission sources responsible for PM2.5. This comparison will benefit from local 3D air quality modeling capabilities of investigators in Utah, at the EPA or USDA, or at NOAA. Identification of a modeling component to this study will be a critical need going forward.