A Na2CO3-coated denuder and filter for determination of gaseous HNO3 and particulate NO−3- in the atmosphere

Measurement of Atmospheric Pollutants Relevant to Dry Acid Deposition

The transfer of acid gases and particles from the atmosphere to the earth's surface, where they exert adverse environmental effects, is called acid deposition. Relevant removal processes occur during dry weather conditions, during the formation of clouds or by scavenging of falling rain or other hydrometeors. The first removal process is called acid dry deposition while the last two, known as rainout and washout, respectively, are lumped together into the phenomenon of acid wet deposition.

Trends in Atmospheric Trace Gas Measurement Instruments with Membrane-based Gas Diffusion Scrubbers

A diffusion scrubber (DS) is an excellent tool for gas analysis, and there are many types of DS devices, varying both in structure and construction. In this paper, recent work on atmospheric trace gas measurements by means of DS devices are reviewed. Theoretical considerations on representative DSs are summarized first. Then, the characteristics of the key material, a gas-diffusion membrane, are discussed, and recent improvements and novel scrubbers for highly effective collection are outlined. A chromatograph is a suitable tool for the multi-gas analysis of collected species. On the other hand, solid-state fluorescence/absorbance detectors have been developed for the continuous measurement of target gases. The methods based on DS collection and subsequent detection have high sensitivities, and the detection limits can be in the low-pptv levels. Accordingly, they are capable of measuring background levels, and detecting very low levels of contaminants in a cleanroom. Miniaturized advanced DS units, perhaps the next generation of DS devices, are introduced at the end of this review. DS systems have contributed significantly to our knowledge of the atmospheric dynamics and atmospheric chemistry.