Response of a grassland ecosystem to air pollutants: III--The chemical climate: Vertical flux densities of gaseous species in the atmosphere near the ground

The establishment of element balances for ecosystems presupposes a knowledge of the amounts of the respective element exchanged between the ecosystem and the atmosphere near the ground by determining their vertical flux densities. Any adequate approach to calculate flux densities of gaseous species in the atmosphere has to use micrometeorological techniques. The authors applied the ratiometric method, which is described in detail. Results of flux density calculations for sulfur dioxide, nitrogen dioxide, nitric oxide and ammonia obtained during two years of measurement are discussed with regard to their role in element balances. Flux densities and deposition velocities of ozone are interpreted as functions of meteorological parameters as well as of the biological activity of the canopy. The latter is characterized by the flux density and flux-to-concentration ratio of carbon dioxide.