engleski

Marine sediment geochemistry influenced by the treated city effluents discharge in the coastal zone of the Adriatic Sea (Šibenik, Croatia)

Submerged wastewater effluent discharge in the vicinity of cities along the Adriatic Sea coast may lead to coastal marine sediment contamination by inorganic and organic pollutants, depending of sewage treatment system performance. The city of Šibenik area (Middle Eastern Adriatic coast) had faced in the past the serious problem of the eutrophication of the Krka River Estuary and coastal marine environment that had been receiving untreated industrial and domestic sewage for years. As a region is very attractive because of natural beauties, the problem was becoming more pronounced during the touristic summer period. Sewage treatment system and pipe line to outside of Krka River Estuary was constructed in 2008, and treated effluent is being released into the near shore marine environment SE of the Island of Zlarin by 5000 m long sub-marine pipe system. The investigation was undertaken to examine the metal concentrations in marine sediments influenced by the wastewater disposal system. Surface marine sediment was sampled by Veen Grab Sampler in July, 2014 from thirteen locations around the effluent discharge at the depth of the sea floor ranged from 33.4 m to 62.7 m. Samples were analysed for mineralogy, organic matter and CaCO3 content, and major and trace element concentrations. The univariate and multivariate statistics was applied. The geochemical normalization of data was done using Al, the procedure based on calculation of the regression line of the metal on the normalizer followed by testing the ratios metal/normalizer on all data-points. Calcite is the main mineralogical component, and traces of quartz, dolomite, Mg-calcite and aragonite are present. Normalization of trace metals to Al revealed the strong significance of the regression lines only between Al/Cr (R2adj = 0.957), followed by Al/Pb (0.725) and Al/Zn (R2adj = 0.863). For Hg and Cd, regression lines were not significant. Generally, distinct anthropogenic loads of trace elements in sediment that may be related to the wastewater effluent discharge are not evident.

Submerged wastewater; marine sediment; inorganic and organic pollutants; univariate and multivariate statistics; geochemical normalization

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