Chemistry of atmospheric wet deposition in Italy: Results from a five year study

In 1988-1992, the Italian Ministry of the Environment sponsored a coordination of studies on wet deposition, involving 44 institutions, 47 laboratories and 172 sampling stations. Analytical quality controls included annual intercalibration and validation of the results on the basis of the ionic balance and calculated conductivity. The stations were mainly located in urban and industrial sites in northern Italy, while in the south and islands they were mostly rural. Cluster analysis highlighted eight chemical categories, corresponding to different geographic situations. Wet deposition chemistry is characterized by high base-cation deposition, because of the episodic transport of Saharan dust. High acidity and high concentrations of sulfate, nitrate and ammonium appear in the northwest, while at other northern sites ammonium and calcium buffer acidity. Sulfate and ammonium, but not nitrate, concentrations are lower in the south and particularly in the Alpine stations, but are in any case higher than those measured in remoter areas.