Analysis of semi-volatile materials (SVM) in fine particulate matter

The mass fraction of semi-volatile materials (SVM) in fine particulate matter (PM2.5) was investigated at a subtropical urban aerosol observatory (TARO, 25.0 °N, 121.5 °E) in Taipei, Taiwan during August 2013. In particular, an integrated Denuder-FDMS-TEOM system was employed to study the effectiveness of the coupling of FDMS and TEOM instruments. The charcoal and MgO denuders used in this study performed a removal efficiency of 89 and 95% for positive interferences in OC and nitrate measurements, respectively, and did not induce a significant particle loss during the field campaign, suggesting that denuders should be considered as a standard device in PM2.5 instrumentation. Analysis on the mass concentration and speciation data found that, as a result of SVM loss, FRM-based measurement underestimated PM2.5 by 21% in our case. Coupling FDMS to TEOM significantly improved the bias in PM2.5 mass concentration from −25% to −14%. The negative bias in FDMS-TEOM was attributed to the failure of FDMS in recovering the mass of lost SVOMs in PM2.5. The results of this study highlight the significance of SVM in a subtropical urban environment, give a warning of underestimated health risk relevant to PM2.5 exposure, and necessitate further development of instrument and/or technique to provide accurate ambient levels of fine particulate matters.