Mladen Juračić

Heavy metals in sediments—problems concerning determination of the anthropogenic influence. Study in the Krka River estuary, eastern Adriatic coast, Yugoslavia

Factors that govern heavy metal concentration in sediments were examined by a combined analytical, geochemical, and geological approach. The constrains encountered in the determination of the anthropogenic influence are exposed. The region examined was the Krka River estuary located in the typical karst region of the eastern Adriatic, Yugoslavia.Sedimentological research revealed that: the Krka River (main water supplier) is almost free of suspended terrigenous material; the main supplier of suspended terrigenous matter of flysch origin is a small torrent-type Guduča Creek, and that this fine grained terrigenous material is sedimented mostly in the central enlarged part of the estuary, the Prokljan “Lake.”Three different groups of heavy metals were identified in recent sediments. Increased concentrations of nickel and zinc were found in estuarine sediments due to strongnatural enrichment in source rocks. Manganese and chromium were found to benaturally enriched and depleted in surface layer respectively, due to the different postdepositional geochemical behavior. Lead and copper concentrations were found to be increased in surface sediments in the central part of the estuary, apparently from anthropogenic source.

History of the accumulation of trace metals in sediments of the saline Rogoznica Lake (Croatia)

Abstract Geochemical and sedimentological characteristics, the sedimentation rate (by 137 Cs dating) and the history of the accumulation of trace metals (Cd, Pb, Cu and Zn) in sediments from anoxic, marine water of the Rogoznica Lake, Croatia, have been studied. The sediment is a fine-grained silt throughout the profile, characterized as an authigenic carbonate sediment of mainly biogenic origin, belonging to the anoxic-sulfidic sedimentation environment. The relatively high sedimentation rate (0.093 g/cm 2 per year) in the Rogoznica Lake, in comparison with the nearby coastal area, and the Krka River Estuary can be explained by higher primary biological production in the upper, oxic water layer, as well as the absence of sediment resuspension. The Rogoznica Lake behaves as a ‘sediment trap’ because of its small dimensions and sheltered position. The concentrations of trace metals in sediments are in the range usual for unpolluted marine carbonate sediments. Nevertheless, concentrations of Pb, Cu and Zn, in the uppercore profile of recent and sub-recent (up to the past 40 years) sediments, reflect anthropogenic influences. Leaded gasoline seems to be the principal anthropogenic source of Pb enrichment, while for Zn and Cu it may be of a communal origin, possibly due to recent tourist activity in this area.

Impact of fish farming on foraminiferal community, Drvenik Veliki Island, Adriatic Sea, Croatia

This study examined the impact of fish farming on foraminiferal communities in the Adriatic coastal zone. Samples were taken directly beneath the farm, near the edge of the farm, and at a reference station away from the farm. The foraminiferal community near the farm is characterized by Epistominella exigua, Globocassidulina subglobosa, Haynesina germanica and the genera Elphidium, Bulimina and Brizalina. These foraminiferal species are less abundant seaward. Asterigerinata mamilla, Neoconorbina terquemi and genus Cibicides are almost absent below the cages. Total phosphorus (TP) and total nitrogen (TN) in the sediments decrease with distance from the cages. The abundances of E. exigua, G. subglobosa, H. germanica and the genera Elphidium, Bulimina and Brizalina are correlated with TP and TN, indicating their dependence on nutrient input. The absence of A. mamilla, N. terquemi and the genus Cibicides below the cages is a due to a degraded Posidonia community. According to our study, foraminiferal community composition can be used as indicator of organic enrichment caused by fish farm activities.

Benthic Foraminiferal Assemblages in a Restricted Environment - An Example from the Mljet Lakes (Adriatic Sea, Croatia)

Benthic foraminiferal assemblages from a peculiar restricted marine environment, the Mljet Lakes (Mljet Island, Adriatic Sea, Croatia) have been studied. These lakes are drowned karst dolines, which are connected with the Adriatic Sea through a narrow, shallow channel. Occasional stagnant conditions in the marine lakes cause hypoxic and anoxic conditions in the bottom waters. Such stressed conditions are reflected in oligospecific benthic foraminiferal assemblages with a Shannon-Wiener species diversity index (H) ranging from 0.8 to 1.0 and equitability index (E) ranging from 0.18 to 0.26, identified in samples from each marine lake. In the more dysoxic Malo Jezero, Haynesina depressula dominates an assemblage of 12 benthic foraminiferal species. In the less (and less frequently) hypoxic Veliko Jezero, we found an Asterigerinata mamilla a s s e m b l a g e with 18 foraminiferal species. A more diverse assemblage containing 55 different benthic foraminiferal species occupies an adjacent opensea station. Long-term salinity measurements indicate that H. depressula tolerates higher salinity than formerly presumed (up to 38 ‰), and is well adapted to stressed hypoxic conditions.

Eastern Adriatic Coast (EAC): Geomorphology and Coastal Vulnerability of a Karstic Coast

ABSTRACT Pikelj, K., and Juračić, M., 2013. Eastern Adriatic coast (EAC): Geomorphology and coastal vulnerability of a karstic coast. Coastal zones are one of the most rapidly changing environments on the global scale, mainly caused by anthropogenic activities (industry, urbanization, tourism, and food production). Coastal erosion is primarily a natural process, although human-induced coastal changes are becoming more and more present and are significant factors associated with the loss of beach capacity. The eastern Adriatic coast (EAC) is one of the most rapidly growing tourist markets within the Mediterranean, along which beaches still represent a leading component of the tourism resource. The objective of this paper is to provide an overview of natural geomorphologic features of the EAC as a starting point for further investigation and sustainable management of the coastal zone. The EAC is generally steep and rocky, mostly built up of karstified carbonates, and characterized, thus, by a variety of drowned karstic forms. Beaches in carbonates are mostly small, narrow, and scattered pocket gravel beaches. Coasts developed in the flysch and associated rocks are characterized by longer sandy and gravel beaches. The total beach length along the EAC presumably does not exceed 5%, and the small proportion of the beach length in relation to the rest of the EAC emphasizes their value in the tourist valorization, indicating the need for protection and sustainable management. Due to their geomorphologic diversities, fragmentation, different orientation, length, and sediment composition and budget, each beach should be studied separately and on a small scale. Detailed information on beach profiles, the nearshore geomorphology, and the beach processes needed to plan a sustainable coastal development is still mostly missing.

Sorption behaviour of some chlorophenols in natural sorbents. 1. Validity of the partition model for sorption of phenolates

Abstract In order to verify the validity of the partition model for describing the sorption behaviour of hydrophobic but ionizable polar compounds in natural sorbents, a series of experiments was carried out in which three chlorophenols: 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, were sorbed in 14 different soil and sediment samples. Freundlich isotherm coefficients K f and 1 n were calculated for all three compounds in all sorbents and compared with those favouring phenolate forms. The sorption coefficients K f were closely related to the total sorbent organic matter content with a high correlation coefficient. However, isotherm non-linearities were observed in almost all experiments. The removal of the sorbent organic matter from the three tested sorbents drastically decreased the sorption intensity in two of them, but considerably increased it in the third, indicating that interaction with the mineral surface could be much stronger than sorption in the organic phase. These results indicate that the simplified partition concept used for the sorption of non-polar compounds might not offer an adequate description of the sorption behaviour of chlorophenolates in natural sorbents.

Modern C, O, and H isotope composition of speleothem and dripwater from Modrič Cave, eastern Adriatic coast (Croatia)

Modric Cave is a shallow horizontal cave situated in the middle of the eastern Adriatic coast (Croatia). The cave entrance is located 120 m from the coast at an altitude of 32 m above sea level, and due to its position on the SW slope of the Dinaridic mountain range, a Mediterranean climatic influence is dominant. Due to the stable environmental conditions [(15.6 ± 0.1) °C] Modric Cave was recognized as a potential site for detailed palaeoclimatic studies. Isotope analyses of modern carbonate speleothems, rain and dripwater were conducted in order to evaluate the isotopic equilibrium conditions. The δ18O composition of rain and cave seepage waters shows an absence of kinetic isotopic fractionation within the epikarst zone, whereas the relation between δ13C and δ18O in modern carbonate samples and dripwater suggests the isotopic equilibrium conditions during the carbonate deposition. These results contribute to a better understanding of the present-day isotopic composition and they provide a basis for interpretation of speleothem- derived palaeoclimatic records.

Selected element concentrations in alluvial sediments under garbage disposal site (Zagreb, Croatia)

Abstract Ag, Ba, Cd, Ce, Cs, Co, Cr, Cu, Eu, Fe, Ga, Mn, Ni, Pb, Rb, Sb, Sc, Sr, Th, Ti, V, Zn and Zr concentrations in alluvial sediments were determined by INAA and OES in the area used as a garbage disposal site in the vicinity of a water-well field. Results show that total concentrations of analysed elements depend on sediment characteristics: mineral composition, specific surface area, cation exchange capacity, organic matter and clay-grain size fraction content. On the other hand, concentrations in sediment depend on physico-chemical forms and geochemical characteristics of the elements in question. Most of the elements reveal excellent/very good correlations with iron, while strontium shows negative correlation with iron. Strontium has a very good, positive correlation with carbonate content, while all other analysed elements, except silver, have excellent negative correlations with carbonates. Correlations with clay-grain size fraction are good or very good for all elements, except strontium and silver. The only element which is not correlated, either with iron, carbonate, or with clay-grain size fraction is silver. One can conclude, therefore, that silver is introduced as discrete particles. Extremely high silver concentration was found 6.5–6.8 m below the garbage in the aerated layer, occasionally under the water table. The enrichment factor for silver is found to be 127, which is a clear indication of sediment pollution with silver. Long-lasting clandestine deposition of industrial wastes on a disposal site meant for domestic wastes might be the reason. The elevated concentrations found on the 11.2–11.4 m depth are concordant with mineralogical composition (MnO-hydroxides, iron minerals, illite, chlorite) and enrichment factors for the majority of analysed elements are below 2. For the time being, this sediment layer acts as a chemical filter preventing infiltration in the vertical direction. Concentrations and enrichment factors of all determined elements from the uppermost and deeper water bearing layers are of natural values. Taking into account these, and additional, piezometer results, it can be concluded that the quality of water taken from the water-well field downstream of the garbage disposal site is not endangered so far.

Jabuka Shoal, a New Location with Igneous Rocks in the Adriatic Sea

Petrographic and XRF analyses of the magmatic rock from Jabuka Shoal, 2300 m west of Jabuka Islet (central Adriatic Sea) revealed that the rock is gabbro. This new location of magmatic rocks in the Adriatic confirms their linear arrangement, and indicates the presence of an important fault line which predisposed the occurrences of magmatic rocks.

Sedimentological and surface characteristics of the northern and central Adriatic sediments

The results of this investigation reveal mutual relationship between some sedimentological and surface chemical characteristics, such as granulometric and mineral composition, specific surface area (SSA) and organic matter content, of northern and central Adriatic surface sediments. Grain size distribution and mineral composition enabled the reconstruction of the sedimentation pattern in the northern and central Adriatic Sea. It was shown that sands are spread in the east, along the Croatian coast. Toward the west, the share of finer sediments increases, so that the western region (parallel to the Italian coast) is covered with pelites. Such a pattern is typical for the northern Adriatic and the 401-407 profile of the central Adriatic. Most of the central region is covered with pelites. Granulometric and mineral composition are interrelated, indicating that sediments having more clay minerals (aluminosilicates) are always fine-grained, while coarser sediments contain more quartz and carbonates. The SSA and organic matter content are dependent on the grain size and mineral composition - fine-grained clay minerals have larger SSA’s and contain more organic matter attached to their surface. These organic substances influence considerably the SSA of sediments. It was noted that, after removing the organics, the SSA of sediments changed. This indicates that, effecting the SSA of sediments, organic matter effects their adsorptive ability.