Phase transitions and heterogeneous chemistry of tropospheric aerosols

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In general our research will focus on atmospheric chemistry with an overall goal of improving the understanding of important processes in the atmosphere.The first part of our proposed research will explore the conditions at which atmospheric aerosol particles transform from liquid to solid and vice versa.  In other words, we will explore phase transitions of aerosol particles that are of atmospheric importance.  In these studies we will focus on mixed organic-inorganic particles at temperatures relevant for the free troposphere, which is the region of the atmosphere between approximately 1 km and 18 km in height. Knowledge of the particle phase (i.e. solid or liquid) is necessary to predict the reactivity of particles and also the impact of particles on climate. Our laboratory studies may also be important for predicting the formation of cirrus clouds in the atmosphere.  The second part of our proposed research will explore reactions between gas-phase species and aerosol particles, termed heterogeneous chemistry.  Specific reactions to be studied include the reaction between N2O5 and aqueous aerosol particles coated with organic films and NO3 radicals with organic particles.  Information from these studies may lead to improved predictions of N2O5, NO3, and O3 concentrations in the atmosphere.   Our research may also be important for predicting the lifetime of organic particles in the atmosphere and for predicting the fate of toxic species such as polycyclic aromatic hydrocarbons, which are abundant in the atmosphere.