Organic and inorganic sampling artefacts assessment

During collection on filter-based aerosol samplers, organic and inorganic aerosol compounds both contribute to positive and negative artefacts, significantly affecting chemical analyses results for single species and PM mass concentrations, Up to now, Studies on organic or inorganic artefacts have been conducted in Europe but very scarce data are available for both in a single study. The field study was carried out in Milan, which is located in the Po valley (Northern Italy) one of the major pollution hot spots in Europe. As sampling artefacts depend on many factors, such as filter type, face velocity, sampling duration, and ambient conditions, in this field study two different filter types have been considered (i.e. quartz fibre filters and Teflon filters) for the assessment of both inorganic and organic artefacts during two different seasons (performing also some samplings at different flow-rates). Results showed that positive artefacts due to OC adsorption on quartz filters accounted for 39\% of the OC measured concentration in Summer, and 23\% in winter. Negative artefact due to nitrate volatilisation by the filters was 51\% on Teflon and 22\% on the quartz filters in summer, and no or negligible losses were observed in winter. A significant improvement in the PM mass comparability obtained in parallel samplings on different filters was obtained taking into account the artefact estimates performed in this study. (C) 2008 Elsevier Ltd. All rights reserved.