Acid and alkaline deposition in precipitation on the western coast of Sardinia, Central Mediterranean (40 degrees N, 8 degrees E)

The ionic composition of 53 precipitation samples collected at a coastal site in western Sardinia (Torregrande) was measured in order to determine concentrations and fluxes of the major ions. Precipitation events were sampled over a two year period, Oct'92/Oct'93 and Oct'93/Oct'94. Despite the proximity to the African continent and the detection of Saharan inputs reflected in high pH values and high Ca-nss fluxes, there is evidence for acidic rain with over 54% of the events having pH values <5.6. This would suggest long-range transport of anthropogenic inputs, as there is no obvious local source. Within the study period, a marked decrease in median pH is recorded at Torregrande in '93/'94, decreasing from 5.94 to 5.18. This is coupled with an increase in total annual flux of NO3 from 27 to 63 mu g/cm(2), making the average flux of NO3 in the two years comparable with that at Capo Carbonara (48 mu g/cm(2)). Particulate fluxes at Torregrande show a marked inter- as well as intra-annual variability, from 70 to 200 <mg/cm(2). Variations of pH seems to be partially due to the total particulate as well as Ca-nss fluxes. A statistic of Saharan enriched rain episodes of the two sites showed a peak transport season in April-May and October which is two times greater st Capo Carbonara Rainfall on the west coast, therefore, appears to be less affected by Saharan dust than rainfall on the southern coast and therefore shows greater signs of acidification due to anthropogenic inputs.