Evaluation of the gas collection of an annular denuder system under simulated atmospheric conditions

Abstract

Laboratory studies evaluated the performance of a combined gas and particle sampling instrument. Results of these investigations indicated that the system had the ability to reliably sample atmospheric gases. The sampler consists of a glass inlet/impactor, two Na 2CO 3-coated annular denuders to collect gaseous SO 2, HNO 3 and HNO 2, a citric acid-coated annular denuder to trap NH 3, and a filter pack to collect fine particles and artifact gases. The inlet walls may be extracted to measure the extent of gas deposition on the inlet surfaces. Inlet transmission efficiencies and denuder gas collection efficiencies indicated excellent performance under a wide range of simulated conditions. Laboratory experiments with SO 2, HNO 3 and NH 3 at various concentrations and relative humidities (10−90%) indicated that the annular denuders achieve collection efficiencies near 100%. Tests to investigate the deposition of SO 2, HNO 3 and NH 3 on the walls of the glass inlet showed a small loss (< 10%) of HNO 3 and NH 3. No loss of SO 2 on inlet walls was detected. By extracting the inlet walls the deposited HNO 3 and NH 3 can be recovered.