A gas chromatographic instrument for measurement of hydrogen cyanide in the lower atmosphere

Hydrogen cyanide (HCN) is thought to be a unique, long lived atmospheric tracer for biomass burning emissions. Very few in-situ measurements of HCN have been made at Earth’s surface to date, yet they are critically needed to better evaluate the processes governing the distribution of HCN in the global atmosphere and to assess contributions of biomass burning to the composition and chemistry of ambient air. We developed a gas-chromatographic (GC) instrument with an aim to improve capabilities for measurement of HCN in the lower atmosphere. The main features of the instrument are (1) a cryogen-free cooler for sample dehumidification and enrichment, (2) a porous polymer PLOT column for analyte separation, (3) a flame thermionic detector (FTD) for sensitive and selective detection and (4) a dynamic dilution system for calibration. The instrument was deployed for a ~4 month period from January-June, 2010 at the AIRMAP atmospheric monitoring station Thompson Farm 2 (THF2) in rural Durham, New Hampshire, USA. A subset of the measurements will be presented with a detailed description of the instrument features and performance characteristics. The results demonstrate that the instrument is capable of making long term in-situ measurements of HCN in the lower atmosphere.