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

Abstract

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.