Nitric acid, particulate nitrate and ammonium profiles at the Bayrischer Wald. Evidence for large deposition rates of total nitrate

Chemical measurements at five levels within and above a predominantly spruce forest at the Baverischer Wald (Bavarian forest) National Park, Germany, site show that particulate nitrate, as well as nitric acid, is rapidly removed to the forest canopy. The rate of dry removal to the forest canopy for particulate nitrate was nearly as large as that for nitric acid. Cascade impactor data indicate a major reason for the large particulate nitrate deposition rates may have been its 2-2.5 mu m mean diameter. Dry removal of total nitrate may be sufficient to cause nitrogen saturation at this forest site. In combination with nitrogen wet deposition, the nitrogen available for biotic demand appears to be in sufficient supply to cause ammonia emission from this spruce forest canopy. At some other European forest sites, where ambient air nitrate concentrations are higher, the dry plus wet removal of total nitrate may be sufficient to cause nitrogen availability to be substantially greater than its biotic demand.