Simultaneously Sampling of NH3, HNO3, HNO2, HCl. SO2 And H2O2 in Ambient Air by A Wet Annular Denuder System

Abstract

The automated wet denuder developed at ECN, is based on air sampling by an aqueous solution present in the annulus of a rotating annular denuder. After a sampling time of 35 minutes at a flow rate of 30 1.min-1, automatically the absorption solution is pumped into a sample tube and the denuder is recoated. The obtained solutions are analyzed off-line. The limits of detection for NH3, HNO3, HNO2, HCl and SO2 are 0.1 µg.m-3, and for H2O2 0.01 µg.m-3. During an intercomparison experiment for the measurement of HNO3 and nitrate-containing aerosols in ambient air at Rome from 19 to 23 September 1988, ECN participated with a parallel wet annular denuder system. Advantages of the wet annular denuder are demonstrated by the detection of a strong diurnal variations of HNO3 and NH3 concentrations at Rome. The reproducibility better than 5 % between the parallel denuders for NH3 and HNO3 show the potential use of wet denuders for gradient measurements. Results of experiments in The Netherlands for the simultaneously measurement of NH3, HNO3, HNO2, HC1, SO2 and H2O2 over a year demonstrate the application of the wet denuder as a field instrument.