The National Reference Laboratory for Air Quality (NRL) ensures the high quality of air quality measurements in Finland by organising audits and intercomparison campaigns. In this project, the conformity of the particulate matter measurements was evaluated with a particular focus on the measurement used for calculating the average exposure index (AEI) of Finland. The representativity and applicability of the AEI measurements made at the Kallio station in Helsinki were evaluated. It was noticed that the results of the Kallio measurement represent well the average fine particle (PM2.5) concentrations and the yearly based trend of fine particles in Finland. In addition, the yearly average concentrations of fine particles have been smaller than the AEI limit value of 8.5 µg/m3, at all individual urban background stations in Finland since year 2015. The measurement results made with the PM monitor used for AEI measurement, i.e. TEOM 1405 analyser at the Kallio station, were compared to the results from the reference method that follows the standard SFS-EN 12341:2014. It was noticed that the uncertainty requirement of 25% was reached and therefore the quality of the measurement is sufficient to use it for the calculation of AEI. However, the fine particle concentrations were generally very low and therefore the requirements given in the standard SFS-EN 16450:2017 for an intercomparison against the reference method were not perfectly fulfilled. This report presents also results from intercomparison measurements made for automated continuous measurement systems (AMS). At the Virolahti station and at the Mäkelänkatu station in Helsinki, PM10 and PM2.5 measurements were compared. In Kuopio and in Lahti, intercomparison measurements were made for PM2.5 only. Based on the results from these intercomparisons, the calibration coefficients both for PM10 and PM2.5 were defined for the first time in Finland for a FIDAS 200 analyser that is a new PM monitor in the Finnish market. It was concluded that FIDAS 200 analysers can be used for the PM measurements in Finland when the calibration coefficients are applied for the data; however, one must note that the presented calibration coefficients do not fulfil the requirements given for the demonstration of equivalence (DoE). Nevertheless, these coefficients are recommended to be used until the official coefficients will be delivered from the next DoE campaign. Two AMS (SHARP 5030 and TEOM 1405) were compared to the reference method for the measurements of PM10 and PM2,5 in Virolahti and in Helsinki, respectively. It was revealed that the calibration coefficients based on the DoE in Kuopio (2014–2015) do not always fit ideally at different locations and seasons due to differences in the environmental characteristics of the measurement sites. Therefore, NRL recommends that DoE should be organised every five years and in between the DoE’s so called ongoing-intercomparison measurements should be carried out continuously. In the ongoing-intercomparison, suitability of the calibration coefficients from DoE will be verified in different locations with varying environmental characteristics. The ongoing-intercomparison campaigns should take place at one site from a half a year to one year and after that, the campaign should continue at a different location similarly. This would ensure that the influence of seasonal differences to the suitability of coefficients will be verified at each measurement site.
The European Standard Reference Method systematically underestimates particulate matter in stack emissions
