Intercomparison of Aerosol Spectrometers for Ambient Air Monitoring

Abstract

Three aerosol spectrometers measuring the number concentration distribution of particles in the diameter range 0.01 to 2.5 ¹m were compared by running them side-by-side for 385 h under ambient air conditions in Erfurt, Germany in October 1997. From the spectral data the measured hourly number concentrations in 3 size fractions, the ultra ne fraction (0.01-0.1 ¹m), the accumulation fraction (0.1-0.5 ¹m), and the coarse fraction (0.5-2.5 ¹m), were analyzed. The systematic component of the difference between the instruments was assessed as the geometric mean of the ratio of the measured concentrations (GMR) and the random component as the geometric standard deviation of this ratio (GSR). Previous statistical methods to compare instruments were developed further. A nonlinear multivariate regression method was used to compare the aerosol distribution consisting of several size fractions. Also, the imprecision of the individual instruments (GSI) was estimated. Comparing the instruments within the ultra ne and accumulation fractions, both the GMRs and GSRs ranged between 1.06 and 1.23 and correlations were above 0.98. In the coarse fraction, the GMR of the number concentrations ranged between 0.25 and 4.19, the GSRs between 1.81 and 2.61, and the correlations between 0.72 and 0.85. The GSIs of the instruments were below 1.2 for all fractions but the coarse fraction. To explore possible differences in the classi cation of particles into the accumulation and coarse fractions, coarse fractions were regressed with the coarse and the accumulation fractions of the other instruments. Using a conversion based on this regression, the GSRs between instruments were minimized to 1.35 and the GSI to below 1.3. In conclusion, the aerosol spectrometers were in good agreement in the ultra ne and accumulation size fractions. The differences in the measured number concentrations in the coarse fraction were effectively corrected by using a regression method taking into account also the concentration in accumulation fraction, which suggests possible differences in particle sizing at 0.5 ¹m.

Variability of particulate matter concentrations along roads and motorways determined by a moving measurement unit

“…The accuracy of particle concentration measurements for PM 2.5 is within 20% as was estimated by comparing these instruments with other aerosol counters and spectrometers (Khlystov et al, 2001;Mirme et al, 2002). Hinds and Kraske (1986) showed that the LAS-X sampling efficiency decreases for this fraction: about 30% loss of 10 mm particles at the sampling rate of 5 cm 3 s À1 .…”

Concentrations of ultrafine, fine and PM2.5 particles in three European cities

“…As the aerosol spectrometers were based on di!erent measurement principles and there is no standard instrument available for making comparative measurements of the particle fractions of interest, side by side comparison of the three spectrometers was performed prior to the "eld measurement campaign Mirme et al, 2000). The side by side comparison tests were also made in a laboratory with three di!erent kinds of arti"cial test aerosols .…”

Effects of particulate air pollution on blood pressure and heart rate in subjects with cardiovascular disease: a multicenter approach.

“…In each city, concentrations of ambient air pollutants were measured at a fixed monitoring site representing urban background levels according to the ULTRA SOPs (Pekkanen and Timonen 2000). Size distributions of particle number concentrations were measured with aerosol spectrometers, which had been compared thoroughly in previous side-by-side ambient air measurements Mirme et al 2002;Tuch et al 2000). Fractions of number concentrations in different size classes were determined to form one size class for UFP, (particles in the size range of 0.01-0.1 µm) and one for accumulation mode particles (ACP), (particles in the size range of 0.1-1.0 µm existing networks.…”