BULK, WET AND DRY DEPOSITION ON A FORESTAL AREA IN THE SPANISH BASQUECOUNTRY

During a three-year period (1988-91) we measured bulk and wet deposits of the main contaminants in the municipality of Olatea, a forestal ar ea in the Comunidad Autonoma Vasca, and we estimated the dry deposit, using the results obtained from the first two. The SO42- ion, with 51. 3 kg.ha-1.yr-1, is the ion which appears most in the bulk deposit foun d, whilst the Cl- and SO42- ions, with levels of 62.0 and 34.9 kg.ha-1 .yr-1, are those which appear most in wet deposit. The NO3-, SO42-, Na + and Mg2+ ions are usually deposited during wet processes, whilst the NH4+, K+ and Ca2+ are done so during dry deposit. We have observed dr ops in the Cl- ion and, to a lesser degree, in the NH4+ ion in the bul k deposit as a result of the evaporation processes which these ions ma y undergo in the bulk deposit. The SO42- and Ca2+ ions vary their depo sition form depending upon the type of retrotrajectory of the cloud ma ss.