Atmospheric deposition of nitrogen and sulfur over southern Europe with focus on the Mediterranean and the Black Sea

Atmospheric deposition provides significant amounts of nutrients to the continental and marine ecosystems. Using the mesoscale WRF/CMAQ modeling system, the nitrogen (N) and sulfur (S) atmospheric deposition fluxes over the Mediterranean and the Black seas and continental Europe are evaluated for the year 2008. The annual N and S deposition fluxes are calculated to be 4.89 Tg(N) yr−1 and 2.07 Tg(S) yr−1 over continental Europe, 0.92 Tg(N) yr−1 and 0.52 Tg(S) yr−1 over West Mediterranean, 1.10 Tg(N) yr−1 and 0.84 Tg(S) yr−1 over East Mediterranean and 0.36 Tg(N) yr−1 and 0.17 Tg(S) yr−1 over the Black Sea. Inorganic N deposition fluxes are calculated to be about 3 times higher than gaseous organic N deposition fluxes. Comparison to available observations associates the annual mean model estimates with about 40 ± 30% of uncertainty depending on location. Dry deposition dominates over wet deposition for both N and S in agreement with the observations. Results suggest that an important fraction of the N deposited over the Mediterranean basin can be attributed to transported N species while S deposition is dependent more on the local emissions. In Black Sea and West Mediterranean Sea waters the calculated atmospheric N inputs are comparable to the N export measured by sediment traps whereas in the East Mediterranean N input exceeds by a factor of about 5 the N export. Our simulations show that the critical N load of 1 g(N) m−2 yr−1 is exceeded over 84% of the European forested areas.