A COMPARATIVE STUDY OF THE PRECIPITATION ACIDITY IN TWO CITIES IN CANTABRIA (SPAIN) WITH DIFFERENT DEGREES OF INDUSTRIALIZATION AURELIA BONET*, NIEVES D~AZ-CANEJA *.1, ISABEL GUTIERREZ**, ANTONIO MARTINEZ***, and EUGENIO VILLAR* (Received August 15, 1987; revised January 27, 1988) Abstract. A study was carried out on the pH values obtained from bulk (wet and dry) precipitation samples collected simultaneously in two cities in Cantabria (Spain), Santander and Torrelavega over a period of a year. It was observed that the annual weighted average values for the pH of precipitation, 4.42 and 4.21, respectively, differ significantly although the difference is less than that existing between their pollution levels. The difference is greater when total annual H ÷ depositions are compared. The study also demon- strated the strong influence of long-range transport effect on acidity and to a lesser degree the effect of mid-range transport. 1. Introduction The increase in the acidity of precipitation in any of its forms, something which has been observed in extensive areas of the world over the last 25 yr, and the analysis of its harmful effects have given enormous importance to the study of what is called acid rain, which may have a tremendous impact on the environment. The considerable decrease in the fish population of certain lakes and gulfs is believed to be influenced by acid rain. There is also evidence of the existence of damage to vegetation (Likens, 1976). Increased precipitation acidity speeds up the corrosion of construction materials of buildings, monuments, works of art, etc., and from recent studies it has also been deduced that acid aerosols in high concentrations are a threat to human health (Frezieres et aL, 1982). It is also important to find out to what extent human activities influence the pH of precipitation, as an additional effect to that produced by natural sources such as marine sprays, volcanic emissions or dust on the earth's surface, as well as the possible contribution to the acidity of precipitation in a given place of pollution originating in other regions. In the present study the results obtained from the pH value of bulk precipitation samples collected at two sites with different degrees of industrialization, Santander and * Department of Fundamental Physics, Faculty of Science, University ofCantabria, Avda. Los Castros s/n, 39005 Santander, Spain. ** Department of Medical Physics, Faculty of Medicine, University of Cantabria, Cardenal Herrera Oria s/n, 39011 Santander, Spain. *** Data Processing Section, National Institute of Agrarian Research, P.O. Box 8111, Madrid, Spain. 1 Author for all correspondence. Water, Air, and Soil Pollution 38 (1988) 181-188. © 1988 by Kluwer Academic Publishers.