Chemical composition of rainwater in eastern France

Rainwater sampled weekly at nine sites in eastern France from October 1991 to March 1992 has been analysed for major ions (Cl-, NO3-, SOs2-, NH4+, Na+, K+, Mg2+ and Ca2+), pH and conductivity. The major elements are SO42- and Cl- for the anions and NH4+ and Ca2+ for the cations. The major ion concentrations are higher in urban areas, especially at Colmar (no. 2), where rainfall amounts are low. Surprisingly, the acidity is higher at the sites in rural areas [i.e. mean pH of 4.4 for Ban sur Meurthe (no. 7)] and lower in the urban areas [mean pH of 5.0 for Strasbourg (no. 1) and pH of 5.7 for Colmar (no. 2)]. This is probably due to the presence of CaCO3 in the ''loess'', which is the major constituent of soils in the upper Rhine valley. The relationship between the chemical composition of rain and air-mass trajectories for four humid weeks which presented only one rain event are also examined.