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 variability and sources of dissolved trace elements in the Sava River (Slovenia, Croatia).

The spatial and temporal variability of dissolved trace elements (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sb, Sr, Ti, U, V and Zn) in the upper and middle reaches of the Sava River during two campaigns (2007/2008 and 2017/2018) was examined. The study also included important tributaries and wastewater effluents. No crucial change in metal concentrations in the Sava River water between the two sampling periods was detected. Elements Co, Cr, Cu, Fe, Sb and Zn had higher concentrations at several sites in the first period, whereas Ba, Cd and Pb in the second period. The influence of wastewater discharges proved to be negligible. The highest levels of potentially toxic metals (Cd, Cr, Cu, Sb, V and Zn) were found downstream of the industrial town of Sisak. Concentration-discharge relationship of dissolved elements showed a chemostatic behaviour for As, Cr, Cu, Sr and V and chemodynamic behaviour for all other elements. The UNMIX model, used to identify and quantify metal sources, indicated that soil weathering was the main source of most elements (Al, As, Ba, Co, Cu, Fe, Li, Ni, Sb, Sr and V), with an anthropogenic contribution for Cd, Mo, Pb, Ti and Zn, while Mn and U were associated with colloid formation. The Sava River was defined as moderately polluted regarding metals, whose water quality meets environmental quality standards (EQS). These results may help to better understand the behaviour of dissolved metals in rivers under anthropogenic pressure and to control pollution in the Sava River Basin.

Effects of microscale particles in red mud amended artificial soils on bioaccumulation of elements in E. fetida.

Red mud (RM) contains large quantities of microscale particles < 1 µm and high concentrations of potentially toxic elements. In this research, we have used two types of RM of similar chemical properties but containing different quantities of micro-particles, to test whether their size plays a role in the uptake of chemical elements by earthworm Eisenia fetida. Earthworms were exposed for seven days to artificial soils (prepared in the laboratory following a protocol) amended with increasing quantities of RM. Mortality of 86 % occurred when earthworms were exposed to amended soil containing 46 % of particles below 1 µm. Surprisingly, tissue analyses have shown decreased concentrations of metals instead of the expected toxic effect. SEM analysis revealed that micro-particles strongly adhere to the earthworm epidermis putting them under the large stress. Micro-particles in RM clog their minute dermal pores of 90 nm-735 nm in diameter, which size depends on whether the earthworm's body is contracted or stretched. Strong adhesion of micro-particles to earthworms' epidermis and blockage of their microsize pores prevented normal dermal respiration and absorption of chemical elements through their epithelium resulting in a decrease of most measured metals, especially essential elements potassium, calcium and iron, followed by the lethal outcomes.

Geochemical Characteristics and Preliminary Assessment of Geochemical Threshold Values of Technology-Critical Elements in Soils Developed on Different Geological Substrata Along the Sava River Headwaters (Slovenia, Croatia).

The increased demand for technology-critical elements (TCEs) in emerging technologies brings about the need to determine their spatial distribution in the environment and establish regulatory guidelines. In this paper, concentrations of Li, Sc, Nb, W, Ga, Ge, and REY (rare earth elements, including yttrium) in soils collected from different parent materials in the upper catchment of the Sava River (Slovenia, Croatia) were analysed. Results of multivariate (principal component analysis) and univariate (threshold methods) statistical techniques were used to determine geochemical characteristics of studied soils to identify the background variations and to establish geochemical threshold values. The investigated area is characterized by great lithological diversity and substantial variation of TCE concentrations. Among methods for assessment of geochemical threshold, the TIF (Tukey inner fence) and 97.5th percentile delivered the most reasonable results. Some exceedances above the 97.5th percentile were natural in origin, caused by local geology. These findings can provide baseline data because little is known about TCE variation on different geological substrata.

The assessment of metal contamination in water and sediments of the lowland Ilova River (Croatia) impacted by anthropogenic activities.

The aim of the present study was to assess physico-chemical water parameters, granulometric sediment characteristics and concentrations of trace and macroelements in the water and sediments of the Ilova River. Samplings were conducted at three sampling sites (near villages Maslenjaca, Ilova and Trebez) along the Ilova River, differing in the source and intensity of the anthropogenic influence. This study indicated disturbed environmental conditions, most pronounced in the downstream part of the river (Trebez village) impacted by the activity of fertilizer factory. Water from the Ilova and Maslenjaca villages was of good quality, whereas COD, nitrates and phosphates exceeded the good quality levels in Trebez village. Trace and macroelement concentrations in water were mostly below thresholds set by environmental quality standards at all locations, but levels of Al, As, Cd and Ni were few times higher in Trebez village than at other locations. Metal contamination assessment of sediments (trace and macroelement concentrations, contamination and enrichment factor, pollution load index) confirmed deteriorated environmental quality in Trebez village. However, the overall assessment performed in this study revealed that anthropogenic impact was still not particularly strong in the Ilova River ecosystem. Nevertheless, the observed water and sediment characteristics serve as a warning and suggest that stricter protection measures should be initiated, including continuous monitoring and comprehensive quality assessment of the downstream part of the Ilova River, especially because it is a part of the protected area of the Lonjsko Polje Nature Park.

Geochemistry of recent aragonite-rich sediments in Mediterranean karstic marine lakes: Trace elements as pollution and palaeoredox proxies and indicators of authigenic mineral formation.

This study investigates the geochemical characteristics of recent shallow-water aragonite-rich sediments from the karstic marine lakes located in the pristine environment on the island of Mljet (Adriatic Sea). Different trace elements were used as authigenic mineral formation, palaeoredox and pollution indicators. The distribution and the historical record of trace elements deposition mostly depended on the sedimentological processes associated with the formation of aragonite, early diagenetic processes governed by the prevailing physico-chemical conditions and on the recent anthropogenic activity. This study demonstrated that Sr could be used as a proxy indicating authigenic formation of aragonite in a marine carbonate sedimentological environment. Distribution of the redox sensitive elements Mo, Tl, U and Cd was used to identify changes in redox conditions in the investigated lake system and to determine the geochemical cycle of these elements through environmental changes over the last 100 years. The significant enrichment of these elements and the presence of early formed nanostructured authigenic framboidal pyrite in laminated deeper parts of sediment in Malo Jezero, indicate sporadic events of oxygen-depleted euxinic conditions in the recent past. Concentrations of trace elements were in the range characteristic for non-contaminated marine carbonates. However, the increase in the concentrations of Zn, Cu, Pb, Sn, Bi in the upper-most sediment strata of Veliko Jezero indicates a low level of trace element pollution, resulting from anthropogenic inputs over the last 40 years. The presence of butyltin compounds (BuTs) in the surface sediment of Veliko Jezero additionally indicates the anthropogenic influence in the recent past.

Physico-chemical characteristics of the peloid mud from Morinje Bay (eastern Adriatic coast, Croatia): suitability for use in balneotherapy.

The study conducted in the Morinje Bay (Central Dalmatia, Croatia) included the investigation of the sedimentological, physico-chemical and geochemical properties of the Morinje Bay sediments in order to assess the suitability of the material for wellness-related purposes including medicinal use. The sedimentological characteristics of the Morinje mud are in accordance with the geological origin of the material; the sediment is fine grained, composed mostly of carbonates, quartz and clay minerals. The composition of the sediment determines the physico-chemical properties of the mud. The high content of carbonate minerals diminishes adsorbing the characteristics of the mud to some extent; however, they are still comparable to some commercial mud already successfully used for medicinal purposes. Geochemical analyses have shown that trace metals concentrations in the Morinje Bay samples were mostly in the range with similar material from unpolluted Adriatic environments. Only the concentrations of Cu, Pb, Zn and As were slightly higher than in the reference material, but still within acceptable limits.

Remobilization of metals from slag and polluted sediments (case study: the canal of the Deûle River, northern France).

The anthropogenic impact on the environment in the last century has proven to be very negative due to the fast development of industry. A typical example is the Deûle River in northern France, one of the most polluted sites in this region. The concentrations of Pb, Cd, Zn and Cu in river sediments are 300, 800, 50 and 15 times higher, respectively, than the background values. The present study was undertaken to evaluate the capacity of already polluted sediments to capture metals released from industrial wastes (slag). As it were, in spite of the high metal pollution level, sediments have still shown the ability to adsorb metals released from slag under the conditions provided. Their efficiency in "cleaning up" some of the metals (e.g. Pb) seems to be additionally enhanced in anoxic conditions. This study provided some additional information on the importance of sediments as a pollutant sink.