Titolo della tesi: Defending soil health: potentialities of microbial bioresources isolated from a decommissioned military site in the detoxification of soil co-contamination
Ecosystem, human, plant and animal heath are inextricably linked to the health of
soil, so much that maintaining and restoring soil health is an increasingly crucial
challenge for humans in the context of climate changes. The centrality of maintaining soil functions, i.e. the critical processes that allow soil to provide its ecosystem services, is well understood, and a growing number of studies is focusing on the capability of soil of performing such functions simultaneously, meaning that soil is a multifunctional, complex system. In this context, policy makers and researchers are working on defining indicators to assess soil health, a first step to promote the necessary monitoring and restoring actions, as threats to soils are an ever-growing concern, exacerbated by climate change impacts.
In fact, the latest estimates report that 33% of soil worldwide are moderately to severely degraded and that only in the EU 60% of the totality of soil are impacted by at least one degrading process, including soil contamination. The scale of such contaminations is hard to define, as inventorial data are still being collected and in some cases is spread among different institutions, limiting the capacity of nations and intergovernmental agencies to act. To tackle this challenge the EU has started a multi-action effort that includes passing new legislations and creating a centralized inventory of contaminated sites, that currently accounts for more than 650,000 sites impacted by polluting activities and 240,000 currently investigated for suspected soil contamination. Furthermore, concerns are raising due to the increasingly reported contamination by both inorganic and organic compounds, the so-called “co-contaminations”, due to limits imposed on the currently available restoration technologies. Moreover, co-contaminations are reported in what are usually considered areas of minor interests, such as mining fields and military areas. An often-overlooked aspect in the assessments of impacted soil is the link between soil health and the soil biota. In fact, soil biota and in particular soil microbial communities perform key roles in maintaining soil multifunctionality and are heavily impacted by soil co-contaminations. At the same time, soil microbiomes represent largely unexplored sources of bioresources for novel nature-based solutions to tackle co-contamination in a more sustainable way. In this context, collaborations with sectors historically less involved in environmental restoration, such as the military one, can represent an invaluable chance at identifying and implementing non-disruptive solutions to
environmental issues.This thesis objective was to identify and evaluate potential microbial treatments for the detoxification of soil in a decommissioned military site. Therefore, the activities focused on different key aspects: the isolation of soil
fungal and bacterial communities from a decommissioned military site,
historically co-contaminated by organic and inorganic compounds, combined
with the analysis of diversity of fungal communities; the selection of effective
microbial bioresources followed by the evaluation of functional traits of selected
fungal isolates; the formulation of microbial consortia, reported for their superior
bioremediation capabilities in co-contamination contexts; lastly, the evaluation of
the effectiveness of the formulated microbial treatments in less controlled
condition, through a microcosm experiment. The data collected in this study not only allowed the assessment of the potentialities of the microbial bioresources, some of which are reported for the first time for their bioremediation potential, but also provided an initial contribution to the knowledge of microbial communities in co-contaminated sites and in military sites, including a comparison between bulk soil community and the rhizosphere microbiome of an autochthonous tolerant plant. Lastly, the microbial consortia formulated using the identified bioresources proved to be effective in reducing soil toxicity, as confirmed by a batch of standardized ecotoxicological assays. Based on the results of this thesis, the selected biological treatments are optimal candidates for future implementations as bioresources for remediation and detoxification of co-contaminated soils, making a small yet important contribution to the global efforts to restore soil health.