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7C - Role of environmental science in influencing sustainable development (WE7/13) An emission mass balance study of heavy metals in surfacewater as a tool for environmental policy. Nouwen, Johan1, Van Hooste, Hugo2, 1 Vito, Flemish Institute for Technological Research, Mol, Belgium2 VMM, Flemish Environment Agency, Erembodegem, Belgium ABSTRACT- Heavy metals occur naturally in the environment. In increased concentrations, however, they can be toxic for man and environment dependent on their bioavalability. As heavy metals are not degradable and consequently accumulate in biological tissue, their effects will usually only appear after a long term. Hence, their emissions into the surface water have to be reduced and conventions have been made in the framework of the various North Sea Conferences. Direct discharges to surface water and indirect discharges via sewage plants by diverse sectors – industry (steel, textile,...), households (corrosion of pipes, gutters, natural origin,...), energy (petroleum refineries,...), agriculture, commerce and services (waste incineration,...) – are distinguished. For each of these sectors discharges to surface waters are relatively well known due to monitoring campaigns and the obligatory environmental reporting of companies in Flanders. Some emissions by point sources (e.g. dentists) and diffuse sources (erosion, run-off and drift in agricultural areas, precipitation and dry deposition from the atmosphere, traffic and transport, corrosion of building materials) are hardly known. These emissions at large were quantified using a mass balance study. An attempt for estimation of the different diffuse sources was made. In Flanders, the known emissions in the surface water were and still are tackled by a directional permit policy. Reduction of releases by diffuse sources are de facto not considered. Since the emissions by known sources are already seriously reduced, the relatively contribution of the diffuse sources to the overall emissions into the surface water is getting increasingly important. Reduction of these emissions via an appropriate policy is not straight forward and requires further identification and quantification. Key words: diffuse sources, heavy metals, emissions, mass balance |
