The influence of aluminium industry and bedrock lithology on the oxide content in the urban soil of Sibenik, Croatia

The content of major element oxides (Al₂O₃, SiO₂, CaO, MgO, Fe₂O₃, P₂O₅, K₂O, TiO₂, and MnO) in soil surrounding the light metal factory (TLM), which was producing aluminium from 1937 till 1991, was investigated by EDXRF and XRD. The evaluation of a possible aluminium pollution linked to the industrial activity was studied by a comparison of soil around the TLM with control soil samples. Taking into account natural variations caused by bedrock lithology, control samples were taken in the soil developed upon the Upper Cretaceous limestones and Middle Eocene flysch deposits, while the TLM soil was sampled over the Upper Cretaceous and Early to Middle Eocene limestones; that way the samples constituted four groups, each containing five to seven samples. Control soil overlying flysch deposits differed strikingly from the other three groups by its increased CaO values, and decreased content of Al, Fe, Mn, and Ti-oxides, confirming the overall geochemical imprint of bedrock lithology on the analysed soils. However, a specific mineral composition (presence of alumina) of the TLM soil, together with peculiar correlations among Al₂O₃ and other oxides indicates a certain extent of aluminium pollution of the investigated area.