Polluted deposition in Milan and in the district of Varese [LE DEPOSIZIONI INQUINATE A MILANO E NELLA PROVINCIA DI VARESE]

Mixed samples of both dry and wet depositions were collected and analysed in Milan as well as at Busto Arsizio, Varese and Luino in Northern Italy, during 1984. Very low pH values were found, particularly in the winter months. The mean annual pH values were the following: Milan 4.11, Busto A., 4.28, Varese, 4.46, Luino 4.57; a minimum of pH 3.3 was recorded in Milan in January. Acid deposition, which appears to be mainly due to sulphur dioxide and nitrogen oxides emitted during combustion, is damaging buildings, paintings and sculptures. Some masterpieces, recently restored in Milano, are seriously threatened with ruin. Acid rains have deleterious effect also on soil fertility by causing undesired changes in fundamental biological processes. An increased leaching of nutritive ions may take place, chiefly when soil is composed of non calcareous acidic minerals, and consequently the strong acids contained in rain water are not buffered.