The zinc release by corrosion and run-off from galvanized steel guard rail in the Netherlands is estimated at about 44 t/y. The zinc from this source is distributed over a relatively small area of land, the so-called 'drip zone' immediately below the guard rail. About 63 per cent of this drip zone is situated within the central reservation of highways and the other 37 per cent is within 5.7 m from the carriage way of highways, defined as the 'free zone'. Based on the usage pattern and design rules for the central reservation and the soft border, it can be stated that these areas belong to the technosphere and not to the surrounding environment. Therefore, a risk assessment is not required within the scope of the EU Directive on existing chemicals, but care should be taken to prevent further distribution to the environment. The local zinc load at the drip zones is relatively high, and as the zinc occurs as salts that are easily soluble in water it may eventually infiltrate the deeper subsoil layers. In certain crossings, the run-off from the road and from the guard rails cannot be infiltrated into the soil of the road border but needs to be collected by a drainage system. The discharge of this drainage water to local surface water requires a case-by-case evaluation of the local impact. In general, it may be concluded that unless a large amount of surface water is present to create sufficient dilution, some type of treatment is required to prevent ecotoxic effects in the surface water.
Emission and distribution of zinc from galvanized steel safety fences in the Netherlands
2003
4 Seiten, 1 Tabelle, 12 Quellen
Aufsatz (Konferenz)
Englisch
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