Volatility of water-soluble organic carbon in ambient aerosols

• The water-soluble organic carbon (WSOC) in the fine particles has a higher volatility than that in the coarse particles.
• The WSOC is more volatile than the WIOC in the fine particles.
• The volatilities of the coarse-mode WSOC and WIOC are similar and between those of the fine-mode WSOC and WIOC.
• Adsorption of gaseous organic compounds on a quartz fiber filter influences the measurements of high-volatile carbon.
• The volatility of the water-soluble organic compounds is significantly influenced by their molecular weight.

To examine the evaporation and its application to understand the chemical properties, formation mechanisms, and sources of the water-soluble organic carbon (WSOC) in ambient aerosols, field measurements of carbonaceous compounds in the aerosols were conducted at an urban site in a provincial city, Kofu, Japan. The WSOC in the fine particles evaporated with heating at lower temperature than that in the coarse particles, whereas the water-insoluble organic carbon (WIOC) in the fine particles remained at higher temperature compared with that in the coarse particles. In the fine particles, the WSOC would be more volatile than the WIOC. In the coarse particles, on the other hand, the volatility of the WSOC would be similar with that of the WIOC, and both would have the volatility between the fine-mode WSOC and WIOC. Significant parts of the WSOC were not evolved at 340 °C in air. Adsorption of gaseous organic compounds on quartz fiber filters influenced the measurements of the total carbon and WSOC, especially the carbon evolved at and lower than 120 °C. The evaporation of single standards of four typical water-soluble organic compounds was also examined, of which the results indicated a significant contribution of low molecular weight organic compounds to the WSOC, especially the fine-mode WSOC.