NITRIC-ACID, PARTICULATE NITRATE AND AMMONIUM PROFILES AT THE BAYERISCHER-WALD - EVIDENCE FOR LARGE DEPOSITION RATES OF TOTAL NITRATE

Chemical measurements at five levels within and above a predominantly spruce forest at the Bayerischer 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 th e forest canopy for particulate nitrate was nearly as large as that fo r nitric acid. Cascade impactor data indicate a major reason for the l arge particulate nitrate deposition rates may have been its 2-2.5 mum 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 b e in sufficient supply to cause ammonia emission from this spruce fore st canopy. At some other European forest sites, where ambient air nitr ate concentrations are higher, the dry plus wet removal of total nitra te may be sufficient to cause nitrogen availability to be substantiall y greater than its biotic demand.