Environ. Sci. Technol. 2000, 34, 1919-1925
Concentrations and Estimated Soot Content of PM1, PM2.5, and PM10 in a Subarctic Urban Atmosphere† MARKO J. VALLIUS Department of Environmental Sciences, University of Kuopio, P.O. Box 1627, FIN-70100 Kuopio, Finland, and Unit of Environmental Epidemiology, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland JUHANI RUUSKANEN* Department of Environmental Sciences, University of Kuopio, P.O. Box 1627, FIN-70100 Kuopio, Finland AADU MIRME University of Tartu, Institute of Environmental Physics, U ¨ likooli Str 18, EE2400 Tartu, Estonia JUHA PEKKANEN Unit of Environmental Epidemiology, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland
Mass concentrations of ambient particulate matter were measured in terms of daily average values of PM1, PM2.5, and PM10 for 6 months during the winter of 1996-1997 at a fixed sampling site in Helsinki, Finland, along with meteorological parameters and particle number concentrations in the size range 0.01-1 µm. In addition, the PM filters were subjected to reflectometric analysis to determine absorption coefficients for the various fractions of urban particulate matter. The data were divided into two periods (winter and spring) in order to study more closely seasonal phenomena that have an effect on air pollution patterns. The variations in PM10 and PM2.5 concentrations differed in pattern during resuspended dust episodes, whereas those in PM1 concentrations followed those in PM2.5 fairly well throughout the 6-month measurement period. Thus it seems that PM1 does not provide much additional information on mass concentrations relative to PM2.5. Number concentrations in the ultrafine particle size range from 0.01 to 0.1 µm, especially in wintertime, were much better correlated with absorption coefficients than with any of the three PM mass-based concentrations, indicating that Black Smoke particles are related to that size range. The results also indicate that coarse particle concentrations in ambient air are affected more by seasonal factors than are fine particle concentrations.
Introduction A number of studies carried out during the late 1980s and the 1990s have shown a statistically significant connection * Corresponding author phone: 358-17-163227; fax: 358-17163230; e-mail:
[email protected]. † This work was carried out within the framework of the project “Exposure and risk assessment for fine and ultrafine particles in ambient air” (ULTRA) funded under the EU ENVIRONMENT Program Contract ENV4-CT95-0205. The project was coordinated by the Unit of Environmental Epidemiology, National Public Health Institute, P.O. Box 95, 70701 Kuopio, Finland. 10.1021/es990603e CCC: $19.00 Published on Web 04/12/2000
2000 American Chemical Society
between particulate air pollution and various adverse human health effects (1-6). These findings have also attracted more attention to the methods that are being used to measure particulate matter (PM) in ambient air. The “correct” cutoff size for the fine PM measurement method has been a subject of lively discussion when planning new PM standards recently introduced, in both Europe and the U.S.A. A wide spectrum of factors have an effect on concentrations and other properties of airborne particles in a given sampling location, including local source profiles and source activities, and characteristic seasonal meteorological conditions. The fine fraction of urban airborne particles, smaller than 2.5 µm, comprises mostly primary and secondary anthropogenic combustion products originating mainly from traffic and energy production. Because of their origin, fine particles are usually more carbonaceous in nature than coarse particles, containing both organic (OC) and elemental carbon (EC). Fine particles, especially those containing elemental carbon, are responsible for most of the visibility degradation in the atmosphere, and the carbonaceous particulate fraction largely controls the soiling factor of the urban suspended particulate matter. Diesel exhaust particles, which have very high soiling factor compared to other combustion derived particles (7), have an especially pronounced effect on the blackness of the urban PM. These are predominantly below 0.1 µm in diameter, and almost all of the particles are below 1 µm (8, 9), which enables them to penetrate deep into the human respiratory system when inhaled. While fine (
