Laboratory and field evaluation of an improved glass honeycomb denuder/filter pack sampler

Abstract

A new and improved glass honeycomb denuder/filter pack sampler has been designed to measure atmospheric particles and gases. The new sampler combines the features of a previously developed glass honeycomb denuder sampler with a new inlet that minimizes loss of sampled gases on the inlet surfaces. Another novelty of the improved design is that the honeycomb denuders are entirely made of glass, instead of consisting of a large number of tubes sealed in an outer glass tube with epoxy resin. 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 coated inlet was found to minimize loss of sampled gases. The honeycomb sampler with the improved inlet was characterized in two different field studies. Outdoor concentrations of nitric acid (HNO 3), nitrous acid (HONO), ammonia (NH 3), sulfur dioxide (SO 2), and fine-particle sulfate (SO 4 2−), ammonium (NH 4 +), strong acidity (H +) and fine particulate mass determined using the honeycomb denuder sampler (HDS) were compared to those determined with a collocated Harvard/EPA annular denuder system (HEADS). The average collection of the HEADS sampler was in excellent agreement (e.g. within ± 10% or less) with that of the honeycomb sampler for all the gas and particle phase species in the comparison studies. Results from the laboratory and field tests suggest that the new honeycomb denuder sampler with the improved inlet is suitable for sampling atmospheric particles and gases. In addition, it has the advantage of being more compact than annular denuder/filter pack systems, which makes the sampler more practical for large-scale monitoring studies.