CONTINUOUS MONITORING OF ATMOSPHERIC HCL, HNO2, HNO3, AND SO2, BY WET-ANNULAR DENUDER AIR SAMPLING WITH ONLINE CHROMATOGRAPHIC ANALYSIS

An automated system for the collection, in-line preconcentration and a nalysis of acidifying atmospheric gases is described. Collection of HC l, HNO2, HNO3 and SO2 from ambient air is carried out with an annular wet denuder. After addition of an internal standard to the sample now and conductivity suppression, preconcentration of the sample flow is p erformed by pumping a measured volume of the sample flow through an an ion exchange concentrator column. Following the concentration step, th e anions of the corresponding acids are analyzed by ion chromatography with conductivity detection. The manifold described with two sample l oops and two concentrator columns operating in parallel allows automat ed collection and analysis of two air samples per hour. A computer pro gramme has been developed for automated performance. It allows the sys tem to run unattendedly during extended periods as all the functions, including data processing, are computer-controlled. Factors affecting the performance are reported. The detection limits achieved are 5.4, 1 2 and 17 ng/m(3) for HCl, HNO2, HNO3 and SO2 respectively, with relati ve standard deviations better than 4% at 1-2 mu g/m(3). Ambient measur ements for Petten. The Netherlands, are presented which show the capab ility of the system for continuous monitoring of atmospheric acidifyin g gases.