Phytotechnologies to manage soils polluted by metals

Around the world, thousands of polluted sites are the legacy of decades of industrial activity. This phenomenon has given rise to societal concerns about potential health impacts. Among the various pollutants present in soils, trace metals (known as TMEs), such as lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), cobalt (Co), nickel (Ni), etc., are widely observed on a global scale due to their many uses and high persistence. (Eco)toxic at higher or lower concentrations depending on the nature of the element, and more or less bioavailable depending on their chemical speciation, these pollutants lead to degradation of soil ecosystems and potential health risks.

In Europe, structural changes in the industrial sector are leading to the closure of many operations and a consequent increase in the number of brownfield sites. In fact, the number of sites with potentially polluting activities, whether in operation or closed down, stands at around 3 million. . Nearly 250,000 sites in the mining, industrial and military sectors may require urgent treatment. If current trends continue, with no change in legislation, the above figures are set to rise by 50% by 2025. . Highly diversified and heterogeneous, these soils are major components of urban ecosystems. As a result, demographic and land pressures in urbanized areas are driving the reconversion of these wastelands, and making the management of polluted sites and soils a priority. The development of sustainable techniques for managing excavated soil and treating soil remaining on site is therefore a major challenge. The international SUITMA group (Soils in Urban, Industrial, Traffic, Mining and Military Areas) is working in this direction, bringing together various research teams working on this topic.

Unlike water or air quality, soil quality is not regulated by a framework law in Europe. This is due in particular to soil heterogeneity and the difference between total pollutant concentration and the bioavailable fraction. Soil quality will therefore be taken into account in a non-specific way in various texts relating to water, waste, classified installations for environmental protection (ICPE in France) or the management of chemical substances in Europe.