Background Intense ore and metal production and transformation in Europe have led to large flows of heavy metals and metaloids into rivers. Countries have established general methodologies for studying and managing contaminated sites, but large sites require adapted solutions to tackle specific technical and economic challenges. The gold mining site of Salsigne, La Combe du Saut - located to the north of Carcassonne and south of the Black Mountains in South-West France – was the most important of its kind in Europe. Since early in the 20th Century, hydrometallurgy and pyrometallurgy were used to extract gold from mined ore, releasing around 10 000 tonnes per year - at the peak of production – of arsenic trioxide into the surrounding area, as well as metals such as lead and copper. Since the end of mining activities in 2004, evaluations have estimated around 2 million m3 of waste and pollution at the site over an area of 53 ha. Pollution is given by the presence of ore that contains various metals (lead, copper, etc.) but = arsenic is the main pollutant to focus on. The principal pollution flows from the site into the environment are caused by: soil erosion by water runoff and direct spillage of arsenic into the Orbiel during heavy rainfall (1,300 kg/year ). slow percolation of water through the waste from the site towards the underground water of the Orbiel (300 kg/year). transportation of pollution by dust (particularly windy area).Objectives The Difpolmine project aimed to reduce pollutant flows through both water and air in the area of the former Salsigne and Combe du Saut mines. It planned to develop a new cleaning system that would use, but also go beyond traditional cleaning treatments of excavation, confinement and solidification. In particular, it sought to optimise water management systems in the area and investigate the feasibility of an adapted soil phytostabilisation methodology to minimise residual and diffuse pollution and its subsequent impact. Phytostabilisation consists in using plants which are able to contain, degrade or eliminate pollutants such as metals and pesticides from the medium in which they are contained. Whilst the project looked to demonstrate the applicability of this technique to the specific conditions of the project area in France, it also aimed to prove its transferability to a different mining site in Hungary: a closing zinc and lead mine at Gyöngyösoroszi. It thus hoped to provide an example and source of information for managers of metal-polluted sites in a range of countries and sites. Results The LIFE project Difpolmine successfully tested at laboratory and pilot-plot levels the use of adapted phytostabilisation and water management techniques to reduce water and soil pollution from the sites of former metal ore mines. The selection of the phytostabilisation plants was based on an inventory of the most characteristic plants of the area and the combination of different plants to do different jobs – such as fixing nitrogen from the air and providing good surface cover. Samples of soil from the Combe du Saut site were subjected to phytostabilisation tests in the laboratory to optimise the combination of different plants and soil additives. Steel shots were also chosen for testing as a means of immobilising arsenic through the absorption of arsenate by oxides of iron and manganese. The project partners developed a pollution transport model to simulate the water quality of rainwater run-off. A Geographic Information System – GIS – and behavioural laws were used to simulate water and arsenic flows and inform the design of a water-treatment system. The project tested the methodology on five site sub-plots over two years. Each plot was subdivided into two sections, with one treated with the seed mixture and one not. In most cases, steel shots were also added, but not in all. A system of covered gutters was used to collect the surface water from the subplots and send it to a water monitoring and collection station. Arsenic concentrations were measured in the sediments and in the water. The results of the laboratory and sub-plot tests were environmentally encouraging, particularly given the potential long-term nature of such a treatment and the limited implementation costs involved. The findings also enabled some optimisation of the models and methodology. The project contributed to the development of a full treatment plan for the Gyöngyösoroszi mine site in Hungary, based on a study of the adaptation of the project methodology to its particular characteristics. This shows the potential for use of adapted versions of this methodology across various sites around Europe. However, the project did not manage to test the phytostabilisation methodology at full-scale. This means that evaluation of its total effectiveness will only be possible outside the timeframe of the LIFE funding. This will be done by ADEME through an ongoing research project, Phytoperf. Further information on the project can be found in the project's layman report (see "Read more" section).