ABSTRACT
The development of cylindrical denuders has successfully overcome some of the inherent artifacts in the filtration technique. The concept of a denuder sampler is that air is drawn through a conduit, the gaseous components are removed by diffusion to the walls of the denuder while the particulate matter passes through the tube unaffected. The development of the annular denuder sampler overcame the limitations of cylindrical diffusion tubes. The effectiveness of the denuder diffusion sampler depends on a complete discrimination between the gas species and particulate matter. Diffusion denuder samplers have been used for measurements of dimethyl sulfate and monomethyl sulfuric acid in air and in power plant plumes. Nitric acid is one of the major acidifying components in the atmosphere and may be neutralized if sufficient ammonia is available and the meteorological parameters favor the formation of particulate nitrate. Carboxylic acids, such as formic and acetic acids, are formed in the atmosphere during photochemical smog episodes.
