Pacifico, Lucia Rita (2025) COMPOSITIONAL ANALYSIS OF GEOCHEMICAL DATA FOR THE GENETIC STUDY OF RESIDUAL SOILS AND THE CHARACTERIZATION OF LOCAL BIODIVERSITY. [Tesi di dottorato]

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Abstract

Understanding soil geochemistry is fundamental for evaluating environmental quality, identifying contamination sources, and implementing sustainable land management strategies. This study applies Compositional Data Analysis (CoDA) to geochemical data to improve the interpretation of elemental distributions in residual soils from the Campania region (southern Italy), a geologically complex area influenced by both natural and anthropogenic processes. The research aims to refine geochemical background estimation, assess the bioavailability of Potentially Toxic Elements (PTEs), and investigate their transfer to agricultural crops. A dataset comprising over 7,000 topsoil samples was analysed to differentiate geogenic from anthropogenic contributions to soil chemistry. Traditional geochemical approaches often suffer from statistical limitations due to the closure problem inherent in compositional data. The application of CoDA techniques mitigates these biases, enabling a more accurate identification of elemental associations and contamination sources. A key focus was the soil-to-plant transfer of PTEs, assessed through the estimation of Transfer Factors (TFs) for primary agricultural products (PAPs), also applying multiple regression models to evaluate the influence of pedological parameters (e.g., grain size, organic matter content, pH, cation exchange capacity (CEC), and electrical conductivity) on the mobility and bioavailability of selected elements. The findings reveal element-specific differences in bioaccumulation potential, influenced by both soil chemistry and plant physiology. This has direct implications for food safety and agricultural sustainability in regions where soil contamination poses a potential health risk. Additionally, this study presents the Anthropigene method, an innovative approach to geochemical baseline assessment that relies on immobile elements to define natural geochemical conditions and indicator elements to trace anthropogenic inputs. By constructing spectral lines and calculating similarity percentages, this method provides a refined framework for identifying and quantifying contamination from urban and agricultural sources, addressing the limitations of conventional approaches. Furthermore, the research investigates wildfires as an underexplored source of PTE contamination in soils, focusing on deposition processes and the post-fire redistribution of trace elements. Case studies in wildfire-affected areas of Campania provide insights into the geochemical signature of combustion residues, highlighting their potential to alter soil chemistry and impact ecosystem resilience. Overall, this thesis advances the field of environmental geochemistry by integrating innovative analytical methodologies with large-scale geochemical datasets to improve contamination assessment, refine background estimation, and enhance our understanding of soil-plant interactions. These findings offer critical insights for geochemical monitoring, evidence-based environmental policies, and sustainable agricultural management in regions facing both geogenic and anthropogenic pressures.

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