Decontaminate and recover the soil that has hosted a polluting activity during decades is a long, complex and expensive process, which is many times very hard to face by enterprises or the public administration. Researchers from the University of Oviedo lead a European project that evaluates and polishes the application of the so-called "green technologies" in the recovery of soils contaminated by arsenic or heavy metals. The experts take advantage of the abilities of certain micro-organisms and plants that act as decontaminating agents in tthe terrains. The project is framed in the environmental research line developed by the Cluster of Energy, the Environment and Climate Change promoted by the Campus of International Excelence.

The first results of the work prove the high potential that some plants commonly found in our region have as gatherers of heavy metals and arsenic. This is the case of the birch (Betula celtiberica), the willow (Salix atrocinerea and Salix caprea) and the yellowhead (Ditrichia viscosa), or leguminous plants such as the Melilotus alba. Moreover, the experts have detected the presence of certain endophyte bacteria that resists high concentrations of arsenic and the existence of fungi that favor the processes of decontamination. These advances open the door to using these biological techniques for soils that have been catalogued as contaminated for more than a decade.

The project entitled Innovative and Demonstrative Arsenic Remediation Technologies for Soils (I+DARTS) is funded through the LIFE+ program of the European Union, whose aim is to promote research for the conservation of nature and the protection of the environment. Alongside the University of Oviedo, the Principality of Asturias and Sogener work in the project I+DARTS. The project also has collaborators in research centers of Poland, Sweden and Spain.

The multidisciplinary team of the University of Oviedo, coordinated by Professor José Luis Rodríguez Gallego, has been working since 2012 in three different contaminated sites of Asturias to test in a real scale the results of their research. These places are the tip of El Terronal (Mieres), the site of the old factory of Nitrastur (Langreo) and the old mercury mine of Olicio (Cangas de Onís). The three sites have remains of arsenic in their sub-soil, there is mercury in two of them and in one of them there is an anomalous concentration of lead.

"In truth, we have found very heterogenous sites and this has proved to be a difficulty", Professor Rodríguez Gallego explains. "There are very different terrain compositions in a short distance and this complicates our actions, but we have also been surprised by the great capacity of the environment to regenerate", he concludes.

These methods can be used to lower the cost of recovery in terrains that have been catalog as contaminated for years

The goal of the experts is to perfect the use of biological recovery techniques that allow them to make more environmentally sustainable and economic the decontamination of great industrial sites that were declared contaminated soils years ago. The option chosen until very recently was to dig these sites and remove the contaminated soil, or rather encapsulate it. Both options are complex and costly processes, which in many cases make the cleaning an unviable process. The recovery through these biological techniques may reduce these costs and substantially diminish the environmental impact of the process.

15 researchers from different departments of the University of Oviedo currently collaborate in the project. The leaders of each field of the project are:

• INDUROT: Miguel Ángel Álvarez (Phytostabilization)
• Research Group on the Sub-Soil and the Environment: Jorge Loredo (Electrokinetics)
• Research Group on Technology, Biotechnology and Environmental Geochemistry: Aida González (Phytoextraction), Ana Isabel Peláez (Bioremediation) y Juan María Menéndez (Soil Cleaning).

Banner image:

Premises of the factory of Nitrastur in La Felguera (Langreo). Photo: Luis de Lorián.