Field comparison of a personal cascade impactor sampler, an optical particle counter and CEN-EU standard methods for PM10, PM2.5 and PM1 measurement in urban environment

The need to evaluate personal exposure to aerosol instead of simply measuring outdoor concentrations is now evident. In this connection, Personal Cascade Impactor Samplers (PCIS) and Optical Particle Counters (OPC) are likely to be widely deployed in the near future because their characteristic light weight and low cost make them suitable for the purpose by minimizing interferences in human activities. The study here presented assesses the performances of the two aforementioned instruments by making a comparison with CEN-EU standardized procedures in 24h concurrent measurements of urban PM10, PM2.5 and PM1. The comparison between PM concentrations measured by OPC and CEN-UE standard procedure showed an unsatisfactory agreement: systematic differences, dependent on PM concentration, were evidenced with an underestimation of PM by OPC in the days with low concentrations and an overestimation at higher levels of PM concentration. On the contrary, PCIS can be considered statistically equivalent to CEN-EU standard methods for the determination of PM10, PM2.5 and PM1 with 95% confidence level except that systematic errors in the determination of water soluble inorganic ions (ion chromatography) and some relevant metals (ICP-MS) were evidenced, which could be mainly attributed to a different size cut-off and particle bouncing-off phenomena inside the multi-stage sampler. However, the seasonal mean concentrations of those species measured with PCIS and CEN-EU standard methods were substantially comparables. Thus, PCIS can be considered reliable in studies of PM characterization focused on personal exposure and effects of urban aerosol.