INTERCOMP2000, a campaign to assess the comparability of methods in use in Europe for measuring aerosol composition

In the period 4–14 April 2000, the comparability of methods in use in Europe for measuring aerosol composition was tested. The intercomparison was organised in the framework of the Eureka-EUROTRAC-II subproject AEROSOL and took place at the IfT research station near Melpitz. The origin of the aerosol was highly variable, ranging from very “clean marine” (with PM10=7.6 μg m−3) to quite polluted continental (PM10=32.4 μg m−3), respectively. The focus of the intercomparison was the collection and analysis of those aerosol components for which artefacts occur in sampling and/or analysis, e.g., nitrate and carbon. It was the first field campaign for testing the comparability of the methods in use for measuring aerosol-carbon in Europe. Nineteen collectors were used for its sampling. The average concentration of total carbon (TC) was 2.9 μg m−3 with an overall relative standard deviation of 15%. The concentrations derived from sampling with cascade impactors were on average 77 (±10)% of those obtained with the filters. For elemental carbon (EC), differences of more than a factor of three between methods were observed at a low concentration level. The various optical methods for black carbon (BC) showed good comparability. The concentrations of organic carbon (OC) differed by up to a factor of 2.3. The comparability of nitrate was better than that of carbon, with a random difference between samplers with a mean standard deviation of 0.3 μg m3 day−1, independent of the concentration. The average PM10 nitrate level was 3.6 μg m−3. The same variability of 0.3 μg m−3 was applied for ammonium, which corresponds to a higher relative difference because of the lower absolute values (average ammonium level 2.1 μg m−3). The mass of the individual aerosol components should add up to that of the directly measured mass. This mass closure, within the error limits of such an exercise, was indeed observed. Carbon-containing compounds (35%), ammonium nitrate (35%) and ammonium sulphate (25%) were the dominant species in PM2.5.