A. van der Meulen

PM10: Results of a One-Year Monitoring Survey in the Netherlands

A comprehensive field assessment has been made of the measurement performance of PM10 inlets. Both precision and comparability are approximately 4 percent, complying well with the requirements of the proposed Federal Reference Method (FRM). Fluctuations in sampling efficiency play a dominant role. Hence, both comparability and precision can be interpreted in terms of changes in the 50 percent cutoff diameter D50. In this way a D50 performance of about 0.7 ..mu..m is deduced, clearly within the proposed FRM requirement of D50 = 10 +/- 1 ..mu..m. There exists no fixed linear relationship between PM10 and TSP (total suspended particulate matter): different average situations yield different regression coefficients (Western Europe: 0.7 and USA: 0.5). Furthermore, there are different conversion factors, representative of average (0.5-0.7) or episodic situations of high concentration levels (0.8-0.9). Hence, TSP air quality standards should not be replaced by PM10 ones simply by using the regression results from various national studies because this could yield unequal stringent PM10 standards.

Results of two-and-half years of measurement of acidic aerosols andgases in The Netherlands

Abstract Concentrations of acidifying aerosols sulfate, nitrate, ammonium andhydronium and the gases S0 2 , HNO 2 , HNO 3 and NH 3 have been measured with an annular denuder/filterpack system for 2.5 years at three sites in the Netherlands. For each component at each site the minimum, maximum, average and 95-percentileconcentration have been calculated. Although sometimes, especially during smog episodes, high concentrations were found, these values were alarming with respect to direct health effects. By regression analysis of concentrations of each component at different sites and different components at the same site the reaction and transport of these gases and aerosols have been studied. It seems that acidic aerosols have a relatively long residence time in the atmosphere. Comparison of the measured results with those obtained by othermeasuring methods showed good agreement for S0 2 and on the average 20% difference for all aerosol components.