Metals are normally present in the ecosystem at low concentration. Their presence at high concentration (above the regulation limits) can be due to a pollution event, particularly frequent in proximity of factories like galvanic or steel plant or to an accidental leak of organic compound (es hydrocarbons) which would cause the leaching of iron, manganese or arsenic normally present in soil.
Depending on where a metal contamination occurs (water or soil), the approach for a remediation treatment is different:
- Groundwater: in situ metal precipitation
- Soil: soilwashing with natural biosurfactants
Each metal is characterized by a biogeochemical cycle which regulates its presence in the environment.
In groundwater, a good strategy to neutralize a toxic metal is to change its oxidation state. This can turn a dangerous, persistent and mobile species, into a poorly bioavailable and immobile element that has lost most of its toxic character .
This result can be achieved by controlling parameters in groundwater as the redox potential, the pH, and the dissolved oxygen.
The metal contamination of soils and sediments can be considerably decreased by washing the matrix with surfactant solutions obtained with a natural process.
These surfactants exert on the metal a chelating function, carrying it in solution and effectively removing it from the solid matrix.