Heavy Metal (As, Cd, Cu, Hg, Pb and Zn) Distribution in Topsoil Developed on Alluvial Sediments of the Drava and Sava Rivers in NW Croatia

In the region of north-western Croatia (NWC) 328 topsoil samples were taken (from a depth of 0 to 25 cm). The composite samples were analyzed after near total decomposition (a hot acid mixture: HClO4–HNO3–HCl–HF at 200°C) by ICP–AES for As, Cd, Cu, Pb and Zn. Hg was analysed by cold vapour AAS. The following element concentration ranges were acquired: As 2–74 mg/kg (geometric mean 8 mg/kg), Cd 0.4–9.4 mg/kg (geometric mean 0.4 mg/kg), Cu 5–248 mg/kg (geometric mean 22 mg/kg), Hg 5–4,535 mg/t (geometric mean 55 mg/t), Pb 15–699 (geometric mean 32 mg/kg) and Zn 28–1,432 (geometric mean 82 mg/kg). The analysis of the spatial distribution of heavy metals in NWC showed increased values of As, Cd, Hg and Pb at Mts. Zumberak, Medvednica, Ivanscica and Kalnik that originate mainly from natural sources (bedrock mineralizations and ore deposits). The Cu and Zn contents on Mt. Medvednica are only slightly less natural in origin. The high concentrations of copper on the slopes of Mts. Zumberak, Medvednica, Kalnik and in the NW part of Hrvatsko Zagorje are of anthropogenic origin and are related to wine-growing areas. In the Sava River valley the average levels of Hg, Zn, As, Cd, and Pb are higher than the calculated baseline values (geochemical background) in the NWC while the Cu values are equal to the baseline values. The higher values of As, Cd, Pb, and (in part) Zn are for the most part of anthropogenic origin, and to a lesser extent of natural origin. The Hg in the topsoil has a strong anthropogenic influence caused by mining upstream (Litija) and by the city of Zagreb’s urban area (fossil fuel combustion, traffic, electrolysis, diverse paints, pharmaceutical products, chlor-alkali industry and paper industry). The pedogenic profile shows that the content of Cd, Pb, Cu and Zn at a depth of 20 cm is almost half the content of the same elements found in the first two centimeters of the soil. At a depth of 60 cm, the concentrations are in the level of background values characteristic of the preindustrial era. When compared to the calculated baseline values, the contents of As, Cd, Cu and Hg in the soils of the Drava River valley are higher, while the Pb and Zn contents are anomalous. According to permitted concentrations of heavy metals for ecological food production prescribed by Government regulations the contents of As, Pb and Zn in the topsoil on the Drava alluvial sediment are too high. The Cu concentrations are lower than the limit permitted by Government regulation. The higher contents of mercury, although under the limit prescribed by Government regulation, are an immediate consequence of fossil fuel combustion and traffic in the urban area of the city of Varaždin. Factor analysis and high correlation coefficients show a mutual connection of Pb, Zn and Cd (Pb and Zn r=0.96; Pb and Cd r=0.80; Zn and Cd r=0.84). These 3 heavy metals show high positive factor loadings on the first factor (F1) which accounts for more than 58% of the data variability. The flood waters of the Drava River were highly loaded with anthropogenic Pb, Zn and Cd mainly as a consequence of mining, smelting and flotation activities upstream in the Meza valley in the Republic of Slovenia and Austria. Also, they were additionally loaded with waste waters from upstream settlements. The soil profile shows that increasing depth results in the lowering of the Pb, Zn, Cd and As content reaching the background level of that area at 80 cm depth. This suggests that the alluvial sediments of the pre-industrial era lay deeper

Quaternary Deposits as the Hydrogeological System of Eastern Slavonia

The area of eastern Slavonia, situated between the Drava and Sava rivers, comprises three geotectonic units: the eastern part of the Drava depression in the north, part of the Slavonia-Srijem depression in the south and the central Djakovo-Vinkovci plateau together with the Vukovar plateau. These units are separated by deep faults that reach the base of the Tertiary sediments. The first 200 m of Quaternary deposits are saturated with fresh water. The aim of this study was to find out whether the faults form impermeable boundaries separating the waterbearing deposits into independent hydraulic systems, or if a singular hydraulic entity exists. Results of the analysis indicate that lithological continuity of the aquifers exists along the fault zones on the margins of the Djakovo-Vinkovci and the Vukovar plateaux, which means that there is no impermeable hydraulic boundary on the watershed between the Sava and Drava river valley. The part of eastern Slavonia between the Sava and Drava rivers is one hydraulic system consisting of zones with different transmissivity values. In the zones of reduced transmissivity, the hydraulic connections are weakened, but not broken. Such zones exist not only along the fault zones of the Djakovo-Vinkovci plateau and the Vukovar plateau, but also within the Sava and Drava depressions. The terrain morphology influenced formation of both the surface and the underground watershed, parallel to the extension of the Djakovo-Vinkovci and Vukovar plateau. Therefore, within this single hydraulic entity, when the draw-down reaches the watershed due to excessive pumping, the watershed will be displaced from its natural position

Recent Sediments of Makirina Cove (Northern Dalmatia, Croatia): Their Origin Viewed Through a Multidisciplinary Approach

Makirina Cove was formed by the Holocene sea-level rise which caused a marine ingression into the depression formed within Albian–Cenomanian dolomites at approximately 4.5 ka B.P. At present, Makirina Cove represents an restricted, stressed, shallow-marine (<2m) ecosystem characterized by varying seawater temperatures (0–35°C) as well as fluctuating salinities (up to 41‰) affected by seasonally enhanced evaporation, continuous freshwater supply through on-shore and submarine springs associated with the coastal karst area and surface run-off episodes. These environmental conditions have been conducive to high primary production of organic matter resulting in the formation of organic-rich deposits which contain up to 5 wt.% of organic carbon. Up to the present times, 3.5 m of sediments have been deposited indicating a relatively high sedimentation rate estimated at 0.75 m/1.0 ka in the northern central part of the Cove. The sediments are being deposited mostly as poorly sorted clayey–sandy silts. The distribution and concentration of most of the chemical elements is dependant on the mineralogical composition and granulometric features of the Makirina sediments, which show values more or less similar to those from the Central Adriatic. Accordingly, there is a positive correlation with Al and K concentrations increasing off-shore and with the depth being associated with increasing concentrations of clay minerals within the clay fraction. The same holds true for concentrations of some trace elements, especially Mo and Se which is consistent with the distribution pattern of sulphides. Selenium is preferentially enriched in authigenic pyrite and it is probably the major source of Se in the Makirina Cove sediments. The concentrations of Ca, Mg and Sr decrease off-shore and they are linked to the composition of the surrounding carbonate rocks. The saturation indices show that the water is supersaturated with respect to carbonates enabling the precipitation of authigenic amorphous or crystalline carbonate phases from the pore water in the upper segment of the sediment column. According to the oxygen isotopic (δ18O) composition, molluscs precipitated their carbonate shells mostly during warmer periods (May to November) at or near isotopic equilibrium with their ambient waters. The carbon isotopic δ13C composition of mollusc carbonate shells is environmentally affected due to oxidation and decomposition of organic matter as well as influxes of fresh water into the Cove, indicating their formation out of the predicted isotopic equilibrium with atmospheric CO2. Palynological and organic carbon isotopic (δ13C) composition shows that the sedimentary organic matter (SOM) is 70–90% lipid- and hydrogen-rich and on average 2/3 marine derived (mainly phytoplankton, bacteria and marine macrophytes) and 1/3 terrestrially derived (mainly woody tissue). The variations in composition of SOM have been noted as a function of the distance from the shore. The type and the preservation state of SOM and pyrite as well as the measurements of Eh, pH, total alkalinity, dissolved inorganic carbon (DIC) and the enrichment of redox-sensitive trace elements, indicate oxygen-depleted depositional conditions and that the sediment is highly reductive even in the uppermost segment at the sediment/water interface. According to the results obtained from the applied methods, the features of Makirina sediments strongly reflect the given depositional conditions within this restricted, stressed, shallow-marine environment where these organic-rich sediments originate, and may therefore serve as a calibration standard in further investigations

Evolution of the Adria-Europe plate boundary in the northern Dinarides: From continent-continent collision to back-arc extension

The Sava Zone of the northern Dinarides is part of the Cenozoic Adria‐Europe plate boundary. Here Late Cretaceous subduction of remnants of Meliata‐Vardaroceanic lithosphere led to the formation of a suture, across which upper plate European‐derived units of Tisza‐Dacia were juxtaposed with Adria‐derived units of the Dinarides. Late Cretaceous siliciclastic sediments,deposited on the Adriatic plate, were incorporated into an accretionary wedge that evolved during the initial stages of continent‐continent collision. Structurally deeper parts of the exposed accretionary wedge underwent amphibolite‐grade metamorphism. Grt‐Pl‐ Ms‐Bt thermobarometry and multiphase equilibria indicate temperatures between 550°C and 630°C and pressures between 5 and 7 kbar for this event. Peak metamorphic conditions were reached at around 65 Ma. Relatively slow cooling from peak metamorphic conditions throughout most of the Paleogene was possibly induced by hanging wall erosion in conjunction with southwest directed propagation of thrusting in the Dinarides. Accelerated cooling took place in Miocene times, when the Sava Zone underwent substantial extension that led to the exhumation of the metamorphosed units along a low‐angle detachment. Footwall exhumation started under greenschist facies conditions and was associated with top‐to‐the‐north tectonic transport, indicating exhumation from below European plate units. Extension postdates the emplacement of a 27 Ma old granitoid that underwent solid‐state deformation under greenschist facies conditions. The 40Ar/39Ar sericite and zircon and apatite fission track ages from the footwall allow bracketing this extensional unroofing between 25 and 14Ma. This extension is hence linked to Miocene rift‐related subsidence in the Pannonian basin, which represents a back‐arc basin formed due to subduction rollback in the Carpathians