Application of Group Contribution Methods to the Partitioning of Semi-volatile Organic Compounds on Atmospheric Particulate Matter

摘要

The gas-particle partitioning of a semi-volatile organic compound (SOC) to atmospheric aerosols with organic coating is strongly influenced by temperature (vapor pressure), relative humidity (RH), the chemical composition of the particulate matter, and the amount of organic material in the particulate matter. Experimental partitioning coefficients (K_p) of SOCs were measured using the outdoor Teflon~circleR film chambers and compared to theoretical calculated K_p values as determined from SOC vapor pressures and associated activity coefficients. A thermodynamic model based on group contribution methods was used to estimate the activity coefficients of SOCs in the organic liquid layer of different types of aerosols. Because the true K_p of an SOC in a given medium includes the activity coefficient term, the linearity between log K_p and log P deg_((L)) can be obtained by correcting measured K_p values by the activity coefficient of given SOC at a given temperature and humidity. In this work the partitioning of different types of SOCs on atmospheric particles consisting of liquid-like organic component, such as wood smoke, diesel soot, and secondary aerosol, was studied as a function of temperature and relative humidity in outdoor experimental chambers.