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Abstract :
[en] Within the periurban areas of big cities, soils are often contaminated by heavy metals spread by human activity: atmospheric fallouts due to industry and traffic, recycling of urban wastes (directly or after water treatment), fertilizers and pesticides used in agriculture… This is, among others, verified in the surroundings of Kunming (Yunnan, PR China) and Lille (Nord-Pas de Calais, France), areas with high density of population and traditional metallurgical industries. These areas have also intensive agricultural activities characterized by important vegetable productions, and are generally known as the "green belts" of the cities. These cultures, with short vegetative period, need high biodisponibility of nutrients, biodisponibility which may also occur for other unwanted elements existing in the soil, such as heavy metals. For evident human health reasons the quality of the crops must be ensured and their heavy metal content kept as low as possible, at least under the values of relevant legal thresholds. Thus, vegetables are particularly sensitive to the presence of heavy metals in the soils where they are growing.
It is therefore necessary to manage these soils in order to preserve public health or, more basically, the income of the farmers, as contaminated vegetables would not be marketable. Thus, for these large areas contaminated by diffuse pollution, bioremediation looks to be appropriate. But the kind of the bioremediation which will be applied has to be adapted to the severity of the soil pollution and to the intended land use. In this project, we have assessed the contents of Pb, Cd, Zn and Cu of soils and vegetables within the Chenggong county (near Kunming), and compared the results to the already known situation of the surroundings of two lead and zinc smelters located close to Lille. Then goals and ways of bioremediation have been discussed and the first steps of implementation experimented.