Is the size distribution of urban aerosols determined by thermodynamic equilibrium? An application to Southern California

摘要

A size-resolved equilibrium model, SELIQUID, is presented and used to simulate the size-composition distribution of semi-volatile inorganic aerosol in an urban environment. The model uses the efflorescence branch of aerosol behavior to predict the equilibrium partitioning of the aerosol components between the gas phase and a size-resolved aerosol population over the entire RH domain. Predictions of SEL1QUID are compared against size-resolved composition measurements at different locations during the Southern California Air Quality Study. Based on the modeling results, the size distribution of sub-micrometer nitrate and ammonium can be determined by thermodynamic equilibrium when the RH > 60/100.