Brussels, May 2003
An EU project has discovered that pollutants from seawater are being pumped into coastal soil, causing contamination of freshwater.
Previously, scientists believed that toxic organic pollutants found in sewage, oil and industrial waste were not sufficiently soluble to flow into fresh groundwater. However, the SALTRANS project has found that the situation is quite the reverse:
Funded under the energy, environment and sustainable development (EESD) section of the Fifth Framework Programme (FP5), SALTRANS is in the final stages of examining methods to assess the flow of sal****er through heterogeneous and fractured layers of porous stone, known as aquifers, into groundwater. With a total budget of 2.4 million euro, the project involves researchers from three Member States (France, Spain and the UK), as well as Switzerland and Israel.
To prove their theory, project coordinator Brian Berkowitz and his colleagues set up two glass cells, one containing contaminated seawater or contaminated freshwater, and the other containing uncontaminated freshwater. A layer of porous sand was then placed between the cells.
Pollutants from the contaminated freshwater were seen to seep slowly into the cell containing the clean freshwater. However, in the case of the contaminated salt water, the experiment showed that the pollutants passed through to the freshwater at a much greater speed.
The project consortium refers to this as a 'salt pump' mechanism. 'In such a scenario contaminated seawater acts not only as a source but also as a driving force that magnifies transport of contaminants into the freshwater,' says Professor Berkowitz.
He adds that because 'contaminated marine environments are active, open systems in which waves, tidal movements, streams, and mixing occur continuously, high CCAS [carrying capacity of the aqueous solution] can be expected.' In other words, the more the sal****er is mixed up, the more pollutants it can carry.
The consortium's discovery suggests that not only will engineers, hydrogeologists and those living in arid regions have to deal with the impact of salt intrusion, but it is also now a case of pollutant intrusion to be tackled.
The team of scientists continue to study water-deficient regions such as the coastal region of Mallorca and the Llobregat delta in Barcelona, in order to ensure a cross section of geological sites with salt intrusion problems are represented. They will also assess whether the scenario alters depending on tides, salt, groundwater and types of pollutants.
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