REVIEW OF DEPOSITION MONITORING METHODS

Deposition monitoring may generally serve at least one of the followin g purposes: (a) determining ecosystems at risk, (b) evaluating tempora l and spatial trends. (c) developing numerical models, or (d) estimati ng deposition effects. In this paper, an overview of available knowled ge about monitoring methods is given. Furthermore, it is tried to illu strate the (dis)agreement between results obtained using different met hods. It might be concluded that throughfall, micro meteorological met hods (supplemented/supported by inference) and watershed balance metho ds (S saturated systems) yield similar estimates of the annual mean to tal deposition of sulphur, within generally acceptable uncertainly lim its (approximately 30%). A larger uncertainty exists to estimate reduc ed or oxidised nitrogen and base cation fluxes. It is clear that for i ndividual ecosystems deposition in general, and dry deposition in part icular, can still not be quantified with sufficient accuracy. The vari ous methods have different advantages and drawbacks and the choice of a certain method for estimation of the flux of a specific pollutant to a specific ecosystem may in many cases depend on the purpose of the s tudy and on requirements on accuracy and costs.