Size-resolved gas-particle partitioning characteristics of typical semi-volatile organic compounds in urban atmosphere
Siqi Wang, Yuan-Jie Hu, Yongfang Yuan, Ze-Chao Hu, Chen-Chou Wu, Lian‐Jun Bao, Eddy Y. Zeng
Abstract
Understanding particle size distribution and size-resolved gas-particle partitioning of semi-volatile organic compounds (SVOCs) is important for characterizing their fate in atmosphere. However, the size-resolved gas-particle partitioning characteristics of SVOCs has not been adequately considered. To address this issue, the present study collected gaseous and size-fractioned particulate samples both in and outside of schools, offices, and residences in three districts of different urbanization levels in a megacity, Guangzhou, South China during two seasons. Typical SVOCs, including 15 polycyclic aromatic hydrocarbons (PAHs), six organophosphate esters and seven phthalic acid esters were measured. Emission sources, physicochemical properties , and environmental conditions at the sampling sites considerably impacted the spatiotemporal distribution patterns and particle size distribution of target SVOCs. Not all observed gas-particle partition coefficients ( K p ) of target SVOCs were negatively correlated with subcooled liquid-vapor pressures ( P L 0 ), probably because certain factors, such as the non-exchangeable part of the particle-bound SVOCs, were not considered in traditional gas-particle partition theories. Particle size was an important factor affecting gas-particle partitioning. Adsorption was the dominant mechanism for PAHs with high molecular weight in different particle modes. A new model was established to predict size-resolved K p of PAHs with high molecular weight based on P L 0 and particle size.