Iannone, Antonio (2025) Comparison and integration on a regional scale of geochemical data from different environmental matrices using advanced statistical methods for the estimation of natural background levels and the assessment and ranking of environmental risk. [Tesi di dottorato]

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Abstract

This PhD thesis investigates key challenges in environmental geochemistry within the Campania region, an area characterized by complex geological and tectonic settings, active volcanic processes, and intense anthropogenic pressures. Building upon the extensive datasets produced by recent regional monitoring programs, the research develops and applies advanced operational workflows aimed at improving source discrimination, geochemical background and baseline estimation, and environmental risk assessment across multiple matrices, including topsoils, stream sediments, and drinking water. A comprehensive and reproducible multivariate statistical framework, based on the systematic application of Principal Component Analysis (PCA), was implemented to identify the dominant geochemical processes controlling the composition of more than 7000 topsoil samples. The integration of PCA with geospatial tools and colour composite maps enabled a refined interpretation of geogenic and anthropogenic contributions, including the identification of a distinct signature associated with the Somma–Vesuvius volcanic district, not previously resolved in earlier regional studies. To further enhance background estimation, the thesis incorporates local-scale geostatistical approaches through the application of the Getis–Ord Gi* hotspot statistic. This method allowed the detection of spatial clusters of anomalous concentrations and supported the exclusion of anthropogenic hotspots from background calculations, yielding consistent reference values compared with traditional purely data-driven approaches. A significant methodological innovation concerns the baseline estimation in fluvial environments. By integrating the Sample Catchment Basin (SCB) approach into sediment geochemical prospection within the Sarno River basin, the study accounts for lithological heterogeneity and sedimentary dynamics, enabling the calculation of site-specific baseline values. The comparison with conventional basin-wide baselines demonstrates the superior sensitivity and interpretative power of the SCB-based contamination indices (Contamination Factor and Enrichment Factor), improving the identification of impacted sites in heavily urbanized and industrialized settings. The thesis also addresses the occurrence of naturally occurring radionuclides in drinking water, evaluating total alpha and beta activities and Rn-222 concentrations across different aqueduct sections. Beyond conventional guideline-based assessments, a human health risk evaluation, integrating deterministic and stochastic approaches, was performed for both ingestion and inhalation pathways. The findings underscore the limitations of relying solely on regulatory thresholds and highlight the added value of risk-based methodologies in adequately safeguarding public health, particularly in regions characterized by complex hydrogeological conditions and heterogeneous water supply infrastructures. Finally, the thesis includes additional research activities carried out within the framework of the Environmental Geochemistry Working Group (EGWG), focusing on CO₂ soil gas monitoring and geophysical investigations in seismically active areas. These studies further strengthen the methodological foundation of this work, contributing to a broader understanding of gas migration processes and environmental risk factors. Overall, the research demonstrates how the integration of multivariate statistics, geostatistical tools, and risk-based approaches can significantly advance the interpretation of environmental geochemical data. The methodologies developed provide robust and transferable frameworks for improving environmental assessment, supporting regional authorities, and contributing to sustainable land and water management.

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