Esad Prohić

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.

Evaluation of terra rossa geochemical baselines from Croatian karst regions

Abstract In karst regions of Croatia, regolith is the only favourable medium for geochemical mapping. Mediterranean climate and good drainage due to hard, fissured, permeable limestones and dolomites result in a spacious distribution of terra rossa (FAO-luvisols and cambisols) — a polygenetic type of soil. Samples of terra rossa from coastal and inland Croatian Dinaric karst terrains were collected during the initial studies for the Geochemical Map of Croatia at a density of 1 site/25 km 2 . A total of 87 terra rossa soil samples taken from a depth of 5–25 cm together with 27 samples from deeper profiles (down to 850 cm) were analysed for total Al, Ba, Ca, Co, Cr, Cu, Fe, Ga, La, Mg, Mn, Ni, Pb, Na, Sr, Ti, V and Zn concentrations. A stoichiometric approach was applied by modeling of terra rossa baselines on the basis of linear regressions of metals on Al and the calculation of enrichment factors (EF and CEFs) on the basis of soil standards. A noticeable enrichment of Pb was found in surface samples compared to the terra rossa deeper in the soil profile. Using these baseline relationships, an attempt is made to partition terra rossa metal concentrations into natural and anthropogenic fractions. Also, the models from both polluted and less polluted (uninhabited) karstic terrains improve the comparability of element contents through correction of variable background concentrations. A comparison of elemental concentrations revealed that due to contributions of bauxite debris, a number of studied samples is enriched in Cr and Ni (also with variable amounts of boehmite). The corrections will serve to reduce data variability and to increase the detection of spatial and temporal differences presented on the geochemical maps.

Geochemical patterns in soils of the karst region, Croatia

Soil samples were collected at 420 locations in a 5-km grid pattern in the Istria and Gorski Kotar areas of Croatia, and on the Croatian islands of Cres, Rab and Krk, in order to relate geochemical variation in the soils to underlying differences in geology, bedrock lithology, soil type, environment and natural versus anthropogenic influences. Specific objectives included assessment of possible agricultural and industrial sources of contamination, especially from airborne effluent emitted by a local power plant. The study also tested the adequacy of a fixed-depth soil sampling procedure developed for meager karstic soils. Although 40 geochemical variables were analyzed, only 15 elements and 5 radionuclides are common to all the sample locations. These elements can be divided into three groups: (1) those of mostly anthropogenic origin — Pb, V, Cu and Cr; (2) those of mixed origin — radionuclides and Zn; and (3) those of mostly geogene origin — Ba, Sr, Ti, Al, Na, Ca, Mg, Fe, Mn, Ni and Co. Variation in Pb shows a strong correlation with the pattern of road traffic in Istria. The distributions of Ca, Na and Mg in the flysch basins of southern Istria and Slovenia are clearly distinguishable from the distributions of these elements in the surrounding carbonate terrains, a consequence of differences in bedrock permeability, type of drainage and pH. The spatial pattern of 137Cs from the Chernobyl nuclear power plant accident reflects almost exclusively the precipitation in Istria during the days immediately after the explosion.

Normalization and Trace Element Contamination of Soils in a Karstic Polje - An Example from the Sinjsko Polje, Croatia

Estimation of the anthropogenic over natural contribution in the chemical content of soils and sediments is very important but not easy to measure. Normalization based on either aluminium or iron, as reference conservative elements having supposed natural distributions, is a useful tool in solving this problem. However, several independent factors can influence the normalization procedure, which if not taken into account could lead to completely erroneous conclusions about the origin of the particular elevated concentrations of certain elements. Therefore, a great deal of caution should be exercised during application of the normalization procedure. Analytical data from 95 soil samples from the Sinjsko polje enabled us to critically apply this procedure. Linear regression analysis, evaluation of enrichment factors and trend surface analysis with the construction of appropriate maps were used to test the procedure. Presuming an existing linear dependence between the conservative element and the heavy metal it is possible with the use of linear regression to simultaneously define the heavy metal geochemical background (baseline) and to isolate natural and/or anthropogenic outliers (anomalies). Coupled with geographic plotting facilities this type of outlier-screening is used to locate areas of man made pollution. Statistical treatment of selected elements included the calculation of means, standard deviations and other estimates of basic statistic parameters. Evaluation of enrichment factors reveals the dependence of this parameter upon four main factors: the choice of reference element; the choice of reference material; the homogeneity of reference element distribution in the study area; and correlation of particular element with reference element. Examination of trends is a common procedure in the analysis of geochemical maps. Its purpose is to segregate the underlying trend that possibly pervades the study area, from the local variations, that is, the “noise” or “background”. Statistical analysis, as suggested by the results in this work, would be more properly used over general areas in the karstic terrain, with different geological, geomorphologic and hydrogeological characteristics, rather than being focused on the relatively small phenomena such as poljes, with many local geologic, hydrogeological and geochemical constraints.

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.

Geochemical and Petrographic Evidence of Meteoric Diagenesis in Tufa Deposits in Northern Dalmatia (Zrmanja and Krupa Rivers, Croatia)

SummaryHolocene tufa deposits in the Northern Dalmatia region of Croatia occur along the banks and at present sites of waterfalls of the Zrmanja river and its tributary the Krupa river. Petrographic, geochemical and statistical analyses have been used to relate textural features and trace element composition to the degree of meteoric diagenesis. Trace metal concentrations associated with carbonate phase were determined by sequential extraction procedure. The insoluble residue (I.R.) is predominantly of primary origin and its amount ranges from 3% to 29%, averaging 13.75%, thus permitting variable water/rock ratios of the stabilazing meteoric system. All the evidence points to a scarcity of post-depositional recrystallization and cementation, but where present these features are accompanied by I.R., Mg, Sr and Zn depletion and Fe enrichment.

Movement of contaminants in karstified carbonate rocks

Dynamic flow systems and transport of contaminants in karstic aquifers result from the actions of physical and chemical processes involving aqueous systems containing certain contaminants. These processes are elaborated, and pertinent mathematical and chemical equations are discussed, herein. Contaminant transport in karstic aquifers can be mathematically expressed by the basic equations evaluated primarily for the flow in porous, highly permeable aquifers. The effects of advection, hydrodynamic dispersion, and dilution are elaborated as physical processes that effect the movement of contaminants through groundwater in permeable rocks. Physical and chemical mechanisms that govem contaminant movement and groundwater flow through fractured media are proposed as the basis of an approximate scenario of contaminant transport through karstified carbonate rocks.

Impressions of the Biota Associated With Waterfalls and Cascades from a Holocene Tufa in the Zrmanja River Canyon, Croatia

The following types of calcified deposits characterize Holocene waterfall tufas in the Zrmanja river: mossy deposits, algally laminated crusts and algally coated grains. Petrological examination revealed, that abundant organic remains belonging to mosses and algae provide supporting material, over which tufa accretion takes place, leaving well-defined impressions of the biota. Postgenetic features like meniscus, isopachous and drusy mosaic calcite spar cementation, as well as aggradational neomorphism are only rarely present.

Exchangeable fraction of elements in alluvial sediments under waste disposal site (Zagreb, Croatia)

Concentrations of Ag, Ba, Cd, Ce, Cs, Co, Cr, Eu, Fe, Rb, Sc, Sr, Th, and Zn exchangeable fractions were determined in alluvial sediments at waste disposal site area in the vicinity of water-well field. Samples have been leached with 0.5M NH4Cl at a sample/solution ratio of 1∶20 during 24 hours without shaking. INAA of dry NH4Cl residues show that the concentrations of exchangeable elements determined in the most of the sediments below the wastes have natural levels. Ag, Ba and Sr are readily exchangeable; Rb, Cs and Zn have lower exchangeability, while Cd, Ce, Th, Sc, Eu, Cr, Fe and Co are rather immobile. Extremely high total and exchangeable silver concentration was found at 6.5–6.8 meters below waste in the aerated layer occasionally under the water table. Exchangeable concentrations in deeper water-bearing sediment layers are not elevated. Due to this, one can presume that the upper sediment layers act as chemical filter generally preventing the infiltration from overlying wastes into water-bearing layers.

Contamination of seabed sediments around a shipyard in the Adriatic Sea (Ugljan island)

Geochemical, mineralogical and grain size data from sediment cores in the Lamjana Bay shipyard were obtained to determine the extent of contamination due to ship refits. The concentration and distribution of Ni, Pb, Cr, Zn, Cu, Mn, Cd, As and Fe in 9 sediment samples were measured. No increase of the analysed elements above natural background levels was detected, but contamination was not excluded due to possible dilution of seabed sediment by quartz sand used in process of abrasive blasting.