Long-term measurements of size-segregated ambient aerosol in two German cities located 100km apart

Epidemiological studies suggest that exposure to sub-micrometer aerosol particles poses a health risk. In this study, we had the unique opportunity to investigate the comparability of the ambient aerosol measured at urban background stations in two cities located in one region. We compared particle number size distributions measured in Erfurt and Leipzig, Germany, over a 5-year period from February 1997 through August 2001. Our findings show that mean concentrations, size distributions and their diurnal variations of the ambient aerosol measured at urban background stations in two cities are very similar. Total particle number concentrations (10-800 nm) measured in Erfurt were only 9-20% higher compared to those measured in Leipzig. Average number concentrations in the size ranges 10-20, 20-50, 50-100, 100-200, and 200-800 nm differed by less than 50%. Diurnal variations in particle number distribution in summer and winter in Erfurt showed similar patterns to those in Leipzig. Evidence that the site in Erfurt was more influenced by local traffic compared to the site in Leipzig is the shifts in size distribution towards larger particles in Leipzig along with the 37-43% higher concentration of particles smaller than 30 nm in diameter and the two to three times elevated NO concentrations in Erfurt on workdays. Observed differences between Erfurt and Leipzig size distributions can be attributed to differences in horizontal distance to major roads, inlet heights, terrain, and climatic conditions. Our results suggest that the average urban background aerosol in two cities in the same region is similar if the major sources of the aerosol (traffic, domestic heating) in these two cities are similar. (C) 2003 Elsevier Ltd. All rights reserved.