Two indicators to help the decision-makers

In 2014, Jonathan Richir and Sylvie Gobert also developed two indicators making it possible to take account of the level of pollution of a marine site with regard to trace elements. The first, called TEPI (Trace Element Pollution Index) makes it possible to compare the overall level of pollution of the different sites, regardless of the list of trace elements studied and/or the bioindicator used. The second called TESVI (Trace Element Spatial Variation Index) gives an overall view of the variability of the levels of contamination by a trace element on a greater or lesser scale. “TEPI was recently applied to the Mediterranean basin”, explains the head of the Laboratory (2). “By integrating 110 sampling sites for posidonia, it was possible to draw a map that was colour-coded in blue red, green, yellow and orange according to the level of pollution in trace elements. These kinds of tools are very useful. It helps to improve the presentation of graphs which can sometimes be complicated to understand by an unqualified individual. It also makes it possible to offer a more comprehensive view of the state of a site or area, and to reply directly to the requests of the managers of marine or coastal sites, whether they belong to private or public agencies for water or the environment. European water directives require the development of such synthetic instruments that can help these individuals to choose which measures to prioritize”. The work of the ULg laboratory now also presents the advantage of being able to integrate the well-known trace elements (cadmium, lead, mercury...) and those that are less well-known. Vanadium is a typical example of this. This trace element is an excellent indicator of pollution by hydrocarbons and is very present near port facilities such as refineries.

The application of TEPI and TESVI has yielded a somewhat astonishing result. While the data collected for posidonia shows a markedly high level of pollution in trace elements for the Southern part of Europe, the data relative to mussels show a less-pronounced pollution concerning the same elements. The further south you go, that is to say, nearer to the coast of Africa, the more the data relative to mussels shows a high level of pollution from trace elements. “Our theory is that the mussels, which are artificially kept in cages in open water, show a positive but recent development of the water column in Europe thanks to the effect of treatment and purification installations for used water that have been installed on the land and directives limiting the release of contaminants into the coastal environment. On the other hand, having been excessively polluted for decades, the sediments off European coasts have not yet shown clear signs of improvement”. In the waters off African coasts which are far less well equipped in purification infrastructures, mussels show a high level of pollution of the water column while the sea sediments seem to be relatively unaffected in comparison to Europe. “This kind of comparative observation, once scientifically validated, presents the advantage of attracting the attention of those decision-makers who are behind the most efficient regulations. At a time when some consider that the purification measures to be taken are too extreme, this is greatly to be welcomed... At least we know which direction to take even though efforts made take a long time to deliver tangible results”.

Renewed vigilance

However, the downside is that while environmental problems related to lead in the environment are steadily decreasing in Europe and in most of the developed countries (mainly due to the fact that it has been removed from petrol), we can reasonably expect to see an increase in pollution that is directly linked to the use of rare trace elements which are used in the manufacture of computer devices and mobile phones, at least in the short-term: as we all know, this market is booming throughout the world. “In the period between 1984 and 2012, the mining of vanadium and the production of bismuth (Editor’s note: a sub-product of the extraction of other metals) have doubled throughout the world. There is risk in the short-term of finding non-negligible quantities of these trace elements in the marine environment following badly managed recycling and recuperation operations. Here, I am specifically thinking of the illegal burning of waste that is adjudged to be of little interest from an economic point of view, or the polluting activites of recycling industries working outside any established or applied standards framework. In the end, all these pollutants run the risk of making their way to the seas and oceans”. The warning has been served: posidonia, mussels, urchins and other bioindicators are still invaluable to researchers.

(2) In addition, the TEPI and TESVI Tools are currently being applied to polychaetes (small benthic worms) in the Channel and the North Sea for the first time which should result in this method being used across this region in the long term.