LABORATORY AND FIELD-EVALUATION OF AN IMPROVED GLASS HONEYCOMB DENUDER FILTER PACK SAMPLER

A new and improved glass honeycomb denuder/filter pack sampler has bee n designed to measure atmospheric particles and gases. The new sampler combines the features of a previously developed glass honeycomb denud er sampler with a new inlet that minimizes loss of sampled gases on th e inlet surfaces. Another novelty of the improved design is that the h oneycomb denuders are entirely made of glass, instead of consisting of a large number of tubes sealed in an outer glass tube with epoxy resi n. The new inlet was designed to reduce the residence time of the air sample as well as the overall surface area available for gas reaction. Although inlets of various materials were tested, the PTFE Teflon coa ted inlet was found to minimize loss of sampled gases. The honeycomb s ampler with the improved inlet was characterized in two different fiel d studies. Outdoor concentrations of nitric acid (HNO3), nitrous acid (HONO), ammonia (NH3), Sulfur dioxide (SO2), and fine-particle sulfate (SO42-), ammonium (NH4+), strong acidity (H+) and fine particulate ma ss determined using the honeycomb denuder sampler (HDS) were compared to those determined with a collocated Harvard/EPA annular denuder syst em (HEADS). The average collection of the HEADS sampler was in excelle nt agreement (e.g. within +/- 10% or less) with that of the honeycomb sampler for all the gas and particle phase species in the comparison s tudies. Results from the laboratory and field tests suggest that the n ew honeycomb denuder sampler with the improved inlet is suitable for s ampling atmospheric particles and gases. In addition, it has the advan tage of being more compact than annular denuder/filter pack systems, w hich makes the sampler more practical for large-scale monitoring studi es.