Heavy Metal Signature and Environmental Assessment of Nearshore Sediments: Port of Koper (Northern Adriatic Sea)

A novel pollution index to assess the metal bioavailability and ecological risks in sediments

The chemical forms of metals in sediments of ports around Taiwan were investigated using sequential extraction. Based on the availability of different chemical forms, novel indices such as bioavailability, mobility, availability, and availability risk of metals in sediments were developed. The results showed that Co, Zn, Pb, Mn, and Cu were mainly present in available forms (49-84 %), and the proportion of oxidative or reductive fractionation was the highest. This suggests that the redox potential is a major factor for metal mobility in the sediments. The results from the proposed indexes showed that metals in sediments have low bioavailability but high to very high mobility and availability. Primarily, the proposed index is more appropriate, as the current index for assessing total metal content may overestimate the level of risk. The indexes established can comprehensively evaluate the bioavailability, mobility, availability, and ecological risk of metals in sediments.

The response of metal mobilization and redistribution to reoxygenation in Baltic Sea anoxic sediments

To bring life back to anoxic coastal and sea basins, reoxygenation of anoxic/hypoxic zones has been proposed. This research focuses on the metals released during the oxidization of sediments from two locations in the anoxic Eastern Gotland Basin under a laboratory-scale study. Triplicate experimental cores and reference cores were collected from the North and South Eastern Gotland Basins. The oxygenation of the water column took place over a 96-hour experiment in a dark and 5 °C environment. In 12 and 24 hour intervals, the surface waters were exchanged and, over time, analyzed for pH, electroconductivity (EC), total organic carbon (TOC), soluble metal concentrations, and the top samples (0-10 cm) were analyzed with 3-step (E1: water-soluble, E2: exchangeable, and E3: organic-bound) sequential chemical extraction (SCE). Results show stable pH and decreasing EC in the column waters. The EC indicates that metals are released in the initial phases (12 h) of reoxygenation for both sites. Arsenic, Ba, Co, Mn, Rb, U, K, Sr, and Mo are released into the water column during the 96 hour experiment, and based on the calculations for the entire East Gotland Basin, would mean 8, 50, 0.55, 734, 53, 27, 347,178, 3468, and 156 μg L^-1 are released, respectively. Elements Mn, Mo, U, and As are released in higher concentrations during the experiment than previously measured in the Eastern Gotland Basin, which provides vital information for future proposed remediation and natural geochemical processes with their known environmental impacts. The SCE results show that redox-sensitive metals (Mn, U, and Mo) are released in the highest concentrations into the solution. The relationship between the highest released metals (beside redox-sensitive) into solution over the oxygenation and their initial abundant phase is noticed, where the smallest released concentrations belong to K < Rb < Sr in E2, and As<Ba in E3, respectively.

Origin and history of trace elements accumulation in recent Mediterranean sediments under heavy human impact. A case study of the Boka Kotorska Bay (Southeast Adriatic Sea)

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources.

Spatial and temporal distribution of pollution indices in marine surface sediments-a chemometric approach

Concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn, and Fe measured at forty locations in the Boka Kotorska Bay were used to monitor the spatial and temporal quality of sediment and to assess surface sediment contamination over the last 15 years. This ecological geochemistry assessment was made using two classes of pollution indices: single indices concerning the investigated elements (contamination factor (Cf)) and integrated indices concerning the locations (pollution load index (PLI), potential ecological risk index (RI), mean effects range median quotient (MERMQ), toxic risk index (TRI), contamination severity index (CSI)). The distribution of all indices was geostatistically mapped and several hotspots were identified. Based on the indices applied in the risk assessment, the mean contribution of individual metal species to the total risk was determined and presented in the following order: Cd > Hg > As > Pb > Ni > Cu > Cr > Zn. This study revealed that Cd and Hg were at the top of the risk list among the examined elements. The temporal distribution of Hg has shown a decreasing trend during the period 2005-2019, while the presence of Cd in the Bay environment is of major concern. The results revealed that the most polluted part of the investigated area was Tivat bay within the Boka Kotorska Bay. Multivariate statistical analysis of pollution indices resulted in multicollinearity, which enabled the use of a reduced number of indices with an acceptable risk estimation.

Baltic Sea sediments record anthropogenic loads of Cd, Pb, and Zn

The unsustainable settlement and high industrialization around the catchment of the Baltic Sea has left records of anthropogenic heavy metal contamination in Baltic Sea sediments. Here, we show that sediments record post-industrial and anthropogenic loads of Cd, Zn, and Pb over a large spatial scale in the Baltic Sea. We also demonstrate that there is a control on the accumulation of these metals in relation to oxic/anoxic conditions of bottom waters. The total concentrations of Cd, Zn, and Pb were obtained with the near-total digestion method in thirteen cores collected from the Bothnian Bay, the Bothnian Sea, and the west and central Baltic Proper. The lowest average concentrations of Cd, Zn, and Pb were observed in Bothnian Bay (0.4, 125, 40.2 mg kg^-1 DW, respectively). In contrast, the highest concentrations were observed in the west Baltic Proper (5.5, 435, and 56.6 mg kg^-1 DW, respectively). The results indicate an increasing trend for Cd, Zn, and Pb from the early nineteenth century until the 1970s, followed by a decrease until 2000-2008. However, surface sediments still have concentrations above the pre-industrial values suggested by the Swedish EPA (Cd is 0.2, Zn is 85, and Pb is 31 mg kg^-1 DW). The results also show that the pre-industrial Cd, Zn, and Pb concentrations obtained from 3 cores with ages < 1500 B.C. were 1.8, 1.7, and 1.2 times higher, respectively, than the pre-industrial values suggested by the Swedish EPA. To conclude, accumulations of metals in the Baltic Sea are governed by anthropogenic load and the redox conditions of the environment. The significance of correct environmental governance (measures) can be illustrated with the reduction in the pollution of Pb, Zn, and Cd within the Baltic Sea since the 1980s.

Trace elements in the estuarine systems of the Gulf of Trieste (northern Adriatic Sea): A chemometric approach to depict partitioning and behaviour of particulate, colloidal and truly dissolved fractions

Estuaries are transitional water systems where the hydrodynamic processes governing water circulation actively influence suspended particle transport and deposition. In the estuarine mixing zone, the strong physico-chemical gradients resulting from the interaction between river freshwater and seawater may affect the distribution, mobility and fate of several potentially toxic compounds, among which trace elements are of major concern. Knowledge regarding the partitioning behaviour of trace elements would provide essential scientific support for the environmental management of estuaries. In this study, trace element occurrence and phase partitioning among suspended particulate matter, colloidal material and the truly dissolved fraction were investigated in the main Italian and Slovenian estuarine environments of the Gulf of Trieste (northern Adriatic Sea). Further information about the water quality at the river mouths was provided and, in addition to the traditional evaluation of single chemical parameters, a multi-way principal component analysis was employed in order to depict disparities among sampling sites, water layers and seasonal conditions with the final aim of evaluating trace element phase partitioning. Results indicated that the suspended particulate matter acts as the main effective vehicle for Cu, Cr, Fe, Ni and Pb, and enhanced adsorption processes resulted in elevated partitioning coefficients, especially for Fe and Pb. Although disparities occurred between sampling sites and seasons, trace elements showing affinity for the solid phase appeared to be partially bound to the colloidal material. Conversely, As and Cs prevailed in the truly dissolved fraction, especially in seawater and showed scarce affinity for both the suspended particles and colloids.