FIELD INTERCOMPARISON OF FILTER PACK AND DENUDER SAMPLING METHODS FOR REACTIVE GASEOUS AND PARTICULATE POLLUTANTS

Atmospheric sulphate, nitrate, chloride and ammonium species have been measured with colocated filter pack and denuder samplers. In general the total amount of a species collected by the two types of sampler was almost the same, although there was evidence of better inlet efficiency for particles in the filter pack sampler. The filter pack gives slightly higher measurements of the volatile species HNO3, HCl and NH3 than the denuder, with a corresponding lower measure of particulate NO3-, Cl- and NH4+, attributable to volatilization of ammonium salts from the filter pack pre-filter. In the context of most ambient measurements, the divergences between the techniques are small, and it is argued that differences in these measurement techniques are inevitably site, operator and apparatus-specific and data from one site or research group cannot readily be extrapolated to other sites. © 1990.