Temporal and spatial variation of the chemical composition of PM10 at urban and rural sites in the Basel area, Switzerland

Particulate matter measurements of different size fractions (PM4, PM10, TSP ) were performed in the Basel area (Switzerland) at seven urban sites throu ghout 1997 and at two urban and two rural sites during the following year ( April 1998-May 1999). Based on a sample of filters which was chemically ana lyzed, we investigated the chemical composition of PM10 both within the cit y of Basel and among urban and rural sites. The temporal and spatial variab ility of the chemical composition of PM,, was evaluated taking into account additional data from meteorology and further air pollutants. The chemical analyses of PM10 showed that carbonaceous substances (elemental carbon, org anic matter) and inorganic substances of secondary origin such as sulfate, nitrate and ammonium were the most abundant component of PM,, in the Basel area (approximately 60-70%). Difference in the PM,, concentration between u rban and rural sites was larger during the cold season than during the warm season. This was mainly due to the presence of an inversion layer between the city and the more elevated rural sites resulting in higher concentratio ns of nitrate, ammonium and organic matter in the city during the cold seas on. The higher PM,, concentration on workdays compared to weekends was most ly a result of the temporal variation of the concentration of Ca, elemental carbon, Ti, Mn, and Fe, indicating that these compounds are for the most p art caused by regional human activities. Although total PM,, mass concentra tion was found to be in general uniformly distributed within the city of Ba sel, the chemical composition was more variable due to specific sources lik e road traffic and other anthropogenic emissions. (C) 2001 Elsevier Science Ltd. All rights reserved.