Measuring anthropogenic impacts on an industrialised coastal marine area using chemical and textural signatures in sediments: A case study of Augusta Harbour (Sicily, Italy)

From the early 1950s until the late 1970s, Augusta Bay (Sicily, Italy) served as a major European (petro) chemical hub. It thereafter began a progressive decline as several crude oil refining and industrial plants closed due to the transfer of production cycles to other sites around the globe. As a result of the rapid and relatively uncontrolled post-WWII development of the site, several environmental studies identified significant contamination in sediments around the southernmost sector of the bay. The pollution was mainly due to barium (Ba) and mercury (Hg), attributable to the former chlor-alkali plant (1958–2003), and polychlorobiphenyls (PCBs) and hexachlorobenzene (HCB). The present study focuses on understanding the broad legacy of pollution across the whole harbour by systematically analysing 10 sediment cores collected in 2008 for contaminant concentration profiles of Hg, Ba, PCBs, HCB and grain-size variations. Pre-industrial environmental geochemical background conditions were identified using data from the deeper parts of cores. The results show that contamination has affected the entire harbour area to varying degrees, and this has allowed identifying contamination transfer, based on decreasing concentrations and related depths in the sediment cores from the southernmost sector to the central and northern area. A recent finding by the current researchers is that the construction of the dam/breakwater in the early 1960s, that largely coincided with the start of industrial inputs, led to the trapping of fine terrestrial sediment inside the harbour, particularly in the central and northern area. This trapped sediment provides a granulometric time marker in those cores. The presence of highly contaminated sediments inside the harbour represents a significant future liability unless remedial action is applied to remove the worst of the polluted sediment