Bioremediation for heavy metal contaminated brownfields
The development of eco-friendly technologies for soil decontamination is of considerable importance in the achievement of environmental pollution control. Specifically, brownfields contaminated with heavy metals are causing concern, because the biogeochemical behavior of metals is influenced by the soil characteristics of the polluted sites. Ectomycorrhizal (ECM) symbiosis of metal resistant organisms can represent a beneficial association for the improvement of soil quality in order to re-establish vegetation in brownfields. Pine (Pinus sylvestris) growth in the presence of the ECM fungi Paxillus involutus and Pisolithus tinctorius was tested in regard to exposure at different heavy metal concentrations. Mycorrhized pine seedlings have been investigated as a bioremediation system by assessing metal uptake and distribution within plant tissues. Electron microscopy revealed metal accumulation on the surface of the colonized root, inside the root and inside the needle crown. The formation of biominerals was investigated by electron diffraction, and identified pyromorphite within plant tissue. The biominerals were extracellularly embedded in the plant cell wall with indications for mineralization during cell wall growth. Biomineralization potential was discussed in terms or bioreduction, biosorption and bioaccumulation processes that might have been involved by the investigated organisms. Since the bioremediation system proved its efficiency, the ecological implications of ECM associations have been highlighted for afforestation strategies of metal polluted sites.