Atmospheric deposition atPinus radiatasites in the Spanish Basque country

Wet and bulk deposition samples were collected in an open field and under the forest canopy at two Pinus radiata sites in the Spanish Basque Country. Samples were analyzed for the major ions H+, Cl‐, NO3’, S04 2‐, Na+, NH,+, K+, Ca2+ and Mg2+. Concentration of all ions, except H*, increase considerably in forest samples of bulk and wet deposition. SO4 2‐ levels in the bulk deposition under forest canopy in one of the sites, are similar to those found in highly polluted areas in Europe. We have found differences between the two sites with respect to forest canopy capacity to neutralize the acid deposition. We have also observed the influence of the drought on pH values. Thus, pH values are higher in the two sites during drought periods (6.4 and 5.6 in rainfall and 6.6 and 5.4 in throughfall, at both sites), and lower when rainfall returns to normal values (5.1 and 5.4 in rainfall and 5.4 and 4.9 in throughfall at both sites).