Measurements of non-volatile aerosols with a VTDMA and their correlations with carbonaceous aerosols in Guangzhou, China

Simultaneous measurements of aerosols of varying volatilities and carbonaceous matters at an urban site of Guangzhou, China were conducted in February and March 2014 using a Volatility Tandem Differential Mobility Analyzer (VTDMA) and an Organic Carbon/Elemental Carbon (OC/EC) Analyzer. In VTDMA, selected aerosols of 40 to 300 nm in mobility diameter were heated at elevated temperatures up to 300°C and the size distributions of the residual particles were measured. Size dependent distributions were observed for both non-volatile and volatile materials (VM). The 40 nm particles were dominated by particles that completely vaporized (CV) at 300°C, with an average number fraction of about 0.4. Particles larger than 80 nm were dominated by the medium and low volatility (MV and LV, respectively) fractions, with average number fractions of 0.5 and 0.15 respectively. VM did not contribute separately to number fraction but contributed to over 50 % of the total volume fraction for all sizes. In both number and volume fractions, diurnal variation was only observed for the high volatility (HV) group, CV and VM in 40 nm particles, likely because these particles were related to fresh emissions. The little diurnal variation of larger particles could be attributed to non-locally aged aerosols. Closure analysis between the residual mass of LV + MV and mass of EC or EC+OC2-4 (sum of EC, OC2, OC3, and OC4 of the OC/EC Analyzer) suggests that non-volatile materials measured by the VTDMA likely contain less volatile OC.