Thiombane, Matar (2018) Environmental geochemistry of Potentially Toxic Elements (PTEs) and Persistent Organic Pollutants (POPs) as a tool of exposure evaluation and chemical risk assessment. [Tesi di dottorato]

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Abstract

Environmental pollution is one of the most challenging environmental issues to tackle due to its impact to human health and the ecosystem. One of the main objectives of environmental geochemistry is to investigate, characterise, and reveal the patterns of organic compounds and inorganic elements and further unveil their possible sources. Geogenic features and anthropogenic activities are the main sources of environmental contamination which are likely to release these contaminants into atmospheric, soil and water media. Moreover, anthropogenic activities let out chemicals produced from industrial activities, domestic, livestock and municipal wastes (including wastewater), agrochemicals, and petroleum-derived products. Organic pollutants cover a large group of synthetized pollutants and Persistent Organic Pollutants (POPs) have received a specific attention due to their physico-chemical properties, high toxicity, and subject to long-range atmospheric transfer. Polychlorinated biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs) and Organochlorines Pesticides (OCPs) are the main POPs that are subject to different regulation schemes to their irreversible adverse effects to both human and wildlife health. Stockholm Convention, Rotterdam and Basel, World Health organisation (WHO) and United Nations Economic Commission for Europe POPs Protocol have so far addressed, threated and introduced legislation which ban or fix threshold’s values of these POPs into environment. Potentially Toxic Elements (PTEs) are widespread metals/metalloids related to geogenic and/or anthropogenic activities. PTEs are one of the major concerns in the environment because their concentrations are increasing due to accelerated population growth rate, higher level of urbanisation and industrialisation providing a great variety of anthropogenic contamination/pollution sources. They have often been given special emphasis because their accumulation in different matrices can cause soil and land degradation and they can be transferred into the human body as a consequence of dermal contact, inhalation and ingestion through food chain and drinking water. PTEs are generally non-biodegradable having long biological half-lives and tend to accumulate in soils being absorbed to clay minerals and organic matter. However, their bioavailability is influenced by different physicochemical processes (e.g. pH, Eh) and physiological adaptation. PTEs and POPs can be observed in different environmental media but soil is considered an important reservoir due to its physico-chemical properties which confer high retention capacity of these pollutants. Soil contamination has been increasing worldwide and has become the focus of attention in recent years. Several soil parent materials are natural sources of certain organic contaminants, elements, and these can pose a risk to the environment and human health at elevated concentrations. For that, various geostatistical computations have been used to identify source patterns of different pollutants related to underlying geological features and/or anthropogenic activities, and to further distinguish mineralisation from contamination. Several single and complex contamination/mineralisation indices such as Enrichment Factor, Geo-accumulation Index or Single Pollution Index have been elaborated to quantify the contamination or mineralisation status of different PTEs. They are generally based on intervention limits (thresholds) or background/baseline values of a single element based on National Legislation, as a reference. Indices based on intervention limits (thresholds) are easily interpretable and comparable, but they disregard the compositional nature of geochemical data; hence they can be biased and/or spurious. This PhD research project reveals novel geostatistical computations that will lay out sources patterns of Potentially Toxic Elements (PTEs) and Persistent Organic Pollutants (POPs), and assess the soils contamination levels in the central-southern Italy. Series of follow up studies have provided an invaluable baseline for these contaminants distribution in Italy to push towards an institutional response for more adequate regulation of these pollutants worldwide. A further ongoing research project is currently investigating the content and bioavailability of mercury and Potentially Toxic Elements (PTEs) in artisanal and small-scale gold mining (ASGM) districts of Kedougou (Senegal). This study in particular will represent a fundamental stepping stone to build a baseline review of PTEs in ASGM of Kedougou (Senegal) and evaluate human health risks from exposure of PTEs. It is envisaged that the results of this study should trigger more detailed surveys in contaminated areas as well as ad-hoc risk-based studies, which in the long-term will constitute a strong argument to cause an adequate institutional response by the Senegalese regulating authorities for a full application the Minamata convention.

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