Atmospheric nitrogen deposition on the east coast of Spain: relevance of dry deposition in semi-arid Mediterranean regions

Bulk deposition composition and pine branch washing were measured from April 1999 to March 2000 on the east coast of Spain. The main objective was to characterise N deposition patterns with special emphasis on dry deposition. Bulk deposition in the region is dominated by neutralisation processes by Ca2+ and HCO3−, ClNa of marine origin and a high correlation between NO3− and SO42−. SO42− concentrations show a decrease with respect to previous studies in the region in agreement with generalized sulfur emission decreases while the remaining ions, including NO3−, are higher due to their general increase as well as to the inclusion of dry deposition in bulk collectors in the present study. An enrichment in NO3− has been observed in dry deposition composition (branch washing) with respect to bulk deposition, while an impoverishment has been observed in the case of NH4+. Annual bulk deposition varies between 7.22–3.1 and 3.5–1.8 Kg ha−1 year−1 for S- SO42− and N- NO3−, respectively. N total deposition goes from 9.78 to 6.8 Kg ha−1 year−1 at most stations, with the lowest deposition at the control station and Alcoi. The relative dry deposition with respect to the total was over 40% at most stations, going up to 75 % at the southern station. N-deposition is expected to be higher considering that N-NH4+ deposition has been underestimated in this study.