Response of a grassland ecosystem to air pollutants. VI. The chemical climate: concentrations and potential flux densities of relevant criteria pollutants.

Of the so-called criteria air pollutants, ozone (O3) and sulfur dioxide (SO2) are relevant to agriculture due to their known toxic (O3, SO2) and fertilizing (SO2) potentials. A proper entity to describe pollutant doses in dose-response relationships is the cumulative flux density absorbed by the respective receptor systems. For nutrient budgets the whole ecosystem acts as receptor; for toxicological considerations, stomatal uptake has to be considered primarily. In Central Europe, the atmospheric inputs of oxidized S (SO2, SO3(2-) and SO4(2-)) have declined from the past, and at present are generally below the nutrient requirements of agroecosystems. In contrast, the phytotoxic potential of O3 has increased during the last decade. Pollutant absorbed doses and weighted concentrations were used to describe the risk potential. It could be shown that these two differ significantly.