Methods to calculate critical loads for heavy metals and persistent organic pollutants

Basic principles of methods for calculating critical loads of the heavy metals lead, cadmium, copper, zinc, nickel, chromium and mercury and persistent organic pollutants (POPs) for soils and surface waters are described briefly. The methods are basedon the implicit assumption that environmental quality criteria do exist for the metals and POPs. The computation models described are based on the concept of equilibrium partitioning between dissolved and adsorbed phases in homogeneously mixed soil, surface water and sediment compartments in a steady-state situation. The various sources of uncertainty inherent in the various assumptions are discussed in detail.