Development of an In Situ Thermal Desorption Gas Chromatography Instrument for Quantifying Atmospheric Semi-Volatile Organic Compounds

摘要

Semi-volatile organic compounds (SVOCs) play a significant role in the formation of secondary organic aerosol, but their atmospheric abundance and chemical composition are poorly understood. We have developed a new system for the thermal desorption aerosol gas chromatograph (TAG) that extends its capability to quantitatively speciate SVOCs (semi-volatile TAG) having vapor pressures lower than tetradecane (C_(14)) with hourly time resolution. The key component is a passivated stainless steel fiber filter that quantitatively collects both gas and particle phase organic compounds. A separation between gas and particle phase collection is determined through a difference method by periodically sampling ambient air through a multichannel charcoal denuder that efficiently removes gas-phase compounds. Measurements made with this new instrument will provide constraints on the abundance, chemical composition, and gas-to-particle partitioning of atmospheric SVOCs and provide opportunities to improve our understanding of secondary organic aerosol formation in the atmosphere.