Concentrations of ultra"ne, "ne and PM particles in three European cities

Total number concentrations, number concentrations of ultra"ne (0.01}0.1 m) and accumulation (0.1}0.5 m) particles, as well as mass concentration of PM particles and blackness of PM "lters, which is related to Black Smoke were simultaneously monitored in three European cities during the winter period for three and a half months. The purpose of the study was to describe the di!erences in concentration levels and daily and diurnal variations in particle number and mass concentrations between European cities. The results show statistically signi"cant di!erences in the concentrations of PM and the blackness of the PM "lters between the cities, but not in the concentrations of ultra"ne particles. Daily PM levels were found to be poorly correlated with the daily total and ultra"ne number concentrations but better correlated with the number concentration of accumulation particles. According to the principal component analysis airborne particulate pollutants seem to be divided into two major source categories, one identi"ed with particle number concentrations and the other related to mass-based information. The present results underline the importance of using both particle number and mass concentrations to evaluate urban air quality. 2001 Elsevier Science Ltd. All rights reserved.