Atmospheric pollution monitoring using CO2‐laser photoacoustic spectroscopy and other techniques

The subject of air pollution monitoring is reviewed. First, we discuss the main conventional techniques currently applied to the detection of gaseous air pollutants, as well as the state of the art of novel detection schemes. We distinguish between nonspectroscopic and spectroscopic methods. Spectroscopic techniques are of primary interest since they offer several advantages, e.g., the simultaneous monitoring of numerous substances. Photoacoustic (PA) spectroscopy represents a promising spectroscopic technique due to its intrinsically high sensitivity, the large dynamic range, and the comparatively simple experimental arrangement. Emphasis is put on detection selectivity which often may restrict the range of applications of the technique for pollution monitoring due to the lack of powerful, continuously tunable IR laser sources. The theoretical aspects of PA spectroscopy with respect to trace gas detection and multicomponent analysis are thus discussed in detail. Some characteristics of a portable PA system built by us are outlined in order to illustrate the usefulness of such systems.