Tool boxes for soil bioremediation assessment in heavy metal polluted areas

The thesis is divided into seven separate chapters, each of them has a specific purpose. The first chapter is a general introduction. It is based on the accurate bibliographic research and aims to clarify main issues concerning soil and heavy metals (e.g. the concept of soil quality and its indicators, heavy metals bioavailability, the plant-microorganisms interactions in soils, the possible sustainable methods for soil remediation). The general goal of the thesis and the specific aims of the experimental researches are described in chapter 2. The third chapter entitled “Set up a tool box of soil quality bioindicators” describes which “experimental tools” were chosen to assess the soil quality improvement during the bioremediation processes. In the following fourth chapter “Heavy metal bioavailability in soil and bioaccumulation into soil microbial biomass” the methods selected to measure the heavy metal bioavailability and accumulation into soil microbial biomass are described. The fifth and sixth chapters show as the previously selected soil bioindicators respond to two different bioremediation systems. The fifth chapter “Changes of soil quality in a phytoremediation system of a former dump” refers to a phytoremediation system applied to an ex-dump located in “Madonna dell’Acqua”, Municipality of San Giuliano Terme - Pisa (Italy). The discussions of the obtained results are important to evaluate the efficiency of this soil reclamation technology. The sixth chapter, entitled “Use of Plant Growth-Promoting Bacteria to enhance heavy metals phytoremediation in mining soils: a preliminary study under Umbrella project” refers to a pot experiment conducted to test the efficiency of the microbial-assisted phytoremediation based on the soil inoculation of different selected Plant-Growth-Promoting Bacteria. This preliminary test useful for the next pot experiments of the European Umbrella project, was conducted to convey a reflection about the use of PGPB applied to mining soils during a phytoremediation process. Finally, in the general discussion of the seventh chapter, the most important results are summarized and general conclusions are reported, focusing on the aspects of bioremediation to be developed and improved.