资源环境科技发展态势分析平台

This manuscript presents a rigorous examination of the equilibrium radius ratio of hygroscopic aerosol particles that are solution drops of ideal and actual inorganic solutes for a range of solute masses in the relative humidity range 99-100%. Analysis is presented first for ideal solutes over a range of solute masses for different hygroscopicities, providing a theoretical framework for the subsequent analysis of actual solutes. Dimensionless quantities are used to reduce the Kohler equation to one with no free parameters and an approximate solution is presented. Next analysis is presented for three common inorganic solutes of atmospheric importance: sodium chloride, ammonium sulfate, and sulfuric acid, with a range of solute masses considered for each substance. The extent to which nonideality is important for these solutes over the ranges of relative humidities and solute masses considered is examined. A simple but accurate single-parameter expression is presented for the equilibrium radius ratio as a function of relative humidity that contains the dependences on solute mass and composition for these solutes. The accuracy of this expression is quantified and factors that limit this accuracy are discussed. The expression is accurate to within 5% over most of the range of mass-equivalent dry radii from 10 to 250nm and relative humidities from below 99 up to 100%, over which the equilibrium radius ratio varies by more than a factor of 5, and it remains finite at 100% relative humidity. Finally, measurements of hygroscopic growth of aerosol particles in this relative humidity range are discussed.