ATMOSPHERIC CONCENTRATIONS AND DEPOSITION OF NITROGEN AND MAJOR IONS IN CONIFER FORESTS IN THE UNITED-STATES AND FEDERAL-REPUBLIC-OF-GERMANY

Emission densities of air pollutants are higher in Europe than in the U.S. as a whole, suggesting similar differences in atmospheric deposition. We determined air concentrations and deposition during the warm season at conifer forests in Tennessee and northern Germany. Our results confirmed major differences in both chemistry and fluxes. Atmospheric and precipitation concentrations of all ions except H+ were higher at the German site, most significantly for the nitrogen species. The much higher levels of NH4+ at this site reflect higher emissions of NH3, which was the species largely responsible for the lower levels of H+. Total airborne nitrate was dominated by HNO3 in Tennessee. In Germany we found comparable amounts of HNO3 and aerosol NO3-, the concentration of which varied seasonally, apparently in response to agricultural emissions of NH3 that reacted to form NH4NO3. Total deposition of all major ions was much higher at the German site, particularly for the nitrogen species, which exhibited a marked edge effect in throughfall. Dry deposition was determined from air concentrations by using a canopy resistance model and from a statistical model of throughfall fluxes, each of which yielded comparable fluxes for several ions. Dry deposition contributed 10-70% of the ion input and was most important at the German site. Both forest canopies absorbed 40-50% of total deposited nitrogen, primarily from dry deposition. © 1990.