dc.description.abstract | Ambient volatile organic compounds (VOCs) are air pollutants, and also act as precursors of ozone and secondary organic aerosol (SOA). Elevated VOCs, ozone, and fine aerosol levels cause adverse effects on human health.
Knowing the composition of ambient VOCs is the prerequisite of understanding ozone formation and thus its containment strategy. However, the full-range analysis of ambient VOCs in the field is technically challenging, particularly for the more volatile compounds. In this study, a new porous material - activated charcoal NCLA9K4 - will be studied to quantitative enrich ambient level VOCs by a self-built cryogen-free thermal desorption device.
Special attention is given to the enrichment efficiency of the most volatile compounds, namely ethane, ethylene, propane, and propylene, since they are more easily to breakthrough. NCLA9K4, which has micropores (pore range = 0.5 nm ~ 30 nm, average pore size = 1.8 nm) and high specific surface area (3500 m2s-1), was compared with MCM-48 and commercial multi-carbon sorbents for their VOC enrichment capability.
Test of trapping was first performed by cooling the sorbent trap at -10 and -30℃. Further improvement in the Peltier cooling using a better heat-sink allowed a lower temperature of -40℃and; thus, better trapping efficiency for high boiling compounds.
The combination of using A9K4 and Carbosieve III to form a dual-sorbent bed and cooling at -40℃ was able to quantitatively analyze ambient C2-C3 compounds with R2 close to 0.999, RSD better than 3%, and detection limit at sub-ppbv level.
| en_US |