CHEMICAL-COMPOSITION OF FOGWATER IN AN URBAN AREA - STRASBOURG (FRANCE)

To investigate the acidity and to identify the predominant compounds, this work presents the chemical analysis of 18 fogwater samples collec ted during the year 1991 in Strasbourg, in the east of France. For eac h fog event, two droplet size categories (2-6 mu m and 5-8 mu m) have been separately collected and Id ionic components have been analysed. These two fraction sizes were chosen because they correspond approxima tely to the size range that can penetrate the human lung and they may have possible health effects. The dominant species were NH4+, NO3-SO42 - and Cl-, with a maximum level of 12640, 17270, 21620 and 13540 mu eq litre(-1), respectively. For most of the fog events the highest conce ntrations of all analysed species were observed in the 2-6 mu m drople ts. pH values ranged between 2.79 and 5.70 and the fogwater acidity wa s governed by three strong acids, H2SO4, HNO3 and HCl and was partiall y neutralised by NH3 and probably by the presence of CaCO3 in the 'loe ss', which is the major constituent of soils in the upper Rhine valley . In other respects the acetate/formate ratio (methanoate/ethanoate), generally lower than 1, indicates an important pollution due to automo bile exhaust, although the Pb concentrations are moderate due to the g eneral use of unleaded gasoline in France since 1989. (C) 1997 Elsevie r Science Ltd.