Using In-Situ Aerosol Optical Properties to Develop a Novel Air Quality Monitoring and Diagnostic Tool

Air quality in urban areas is degraded by locally emitted aerosols and gaseous precursors as well as aerosols that have been transported from other areas. Increased amounts of particulate pollutants are associated with respiratory and cardiac ailments as well as adverse birth outcomes. Aerosols also have an important impact on the Earth’s climate via direct and indirect effects. However, there is large uncertainty in how much of an impact aerosols actually have. The work presented here uses the optical properties of urban aerosols to create a new tool which has the potential to be used to differentiate aerosol source, as well as understanding the impact pollution has on the climate. The Cloud and Aerosol Spectrometer with Polarization (CASPOL) was operated in the field for the first time as a part of NASA’s Deriving Information of Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ). The CASPOL was mounted on top of the 70 meter tall Moody Tower and took continuous samples during the month of September 2013. Aerosol sources can be distinguished using the CASPOL data. When aerosol concentrations are greater than 100 L^-1, the CASPOL can distinguish aerosol source with only approximately one hour of data. Thus the CASPOL can be used as an air quality monitoring and diagnostic tool as it can determine aerosol source in near real time. To better understand the impact pollution has on the Earth’s climate, soot was generated in our laboratory and the optical properties were examined. Also, soot was used to generate ice crystals in the Texas A&M University Continuous Flow Diffusion Chamber (CFDC) which was used in conjunction with the CASPOL to measure the optical properties of ice nucleated on soot. The optical properties of freshly emitted soot were highly variable, but this could be caused to a sampling error which occurred. The CASPOL was able to distinguish between ice that was nucleated heterogeneously on soot and ice that was nucleated heterogeneously on mineral dusts, and homogeneously nucleated ice. Thus the CASPOL can help in the understanding of pollutions direct and indirect impacts on climate