Ecological remediation and sustainable management of an urban industrial site: case of an historical pollution by inorganic potentially toxic elements (Pb, Cd, Cu, Zn, Sb and As)

Abstract

Rehabilitation of brownfields in urban areas is a major challenge for the sustainable development of cities. Management and conversion of these sites, imposed by regulation, however, require the development of tools for environmental risk assessment and health and sustainable remediation techniques. This thesis focused on the establishment of multidisciplinary tools for the sustainable management of polluted site, with the particular case of rehabilitation recycling of lead batteries with a mainly historical lead pollution and other inorganic pollutants (Cd, Sb, As, Cu and Zn), currently defined as Metal Trace Elements (MTE). While trying to answer questions of applied research, this work has sought to investigate the mechanisms involved in the soil-plant pollutants to strengthen the consideration of the overall quality of soil management for industrial sites. In addition to the tools and procedures conventionally used to assess, control and reduce environmental and health risks caused by polluted soils; measures of bioavailability (plants and humans) and ecotoxicity (different bioassays: inhibition of the mobility of Daphnia magna, Microtox® and induction of bioluminescent bacteria and microbiology) have been developed with the aim to refine the classification of contaminated soils in terms of dangerousness. Moreover, green manure plants (borage, phacelia and mustard), commonly used in agriculture or by gardeners because they improve the bio-physico-chemical properties of soils with a root system and a large production of root exudates were tested for re-functionalization of polluted soils. Finally, the mechanisms involved in the fate of pollutants in the rhizosphere and their microorganisms in the plant were studied. The main results provide some answers and ways of improving the management of soils contaminated by metals and metalloids. (1) First, the size separation for soil fractions allows a significant reduction in tonnages of contaminated material and therefore costs for the landfill excavated soil with a gain result in terms of ecological footprint. (2) Then, calculation for the differents polluted soil samples of eco-scores based on the results of ecotoxicity tests can discriminate more accurately compared to physicochemical parameters required by the regulations. Differences in sensitivity were observed depending on the nature of the bioassay, the origin of the sample, physico-chemical properties and total concentrations of pollutants. (3) Unlike phacelia, borage and mustard improve soil respiration, ecotoxicity and reduce theamount of bioaccessible and total lead in soil, respectively by phytostabilisation and storage in roots (Pb, Sb) or phytoextraction and storage in aerial parts. Further, these plants could be field tested for use in phytoremediation of brownfields and gardens moderately polluted. Depending on the nature of the metal, the type of soil and plant, compartmentalization and speciation of the pollutant differ, and in conjunction with agronomic characteristics of soil and rhizosphere microbial activity. Molecular screening and meta-analysis of microbial genomics have enabled highlight differences in bacterial communities studied by species and growing conditions