Dragana Đorđević

Assessment of heavy metal pollutants accumulation in the Tisza river sediments.

In this study we have worked on the evaluation of heavy metal contamination in the sediments taken from the Tisza River and its tributaries, and thereby used the sequential extraction method, geochemical normalization, the calculation of the enrichment factor (EF), and the methods of statistical analysis. The chemical fractionation of Ni, Cu, Zn, Cr, Pb, Fe, and Mn, carried out by using the modified Tessier method, points to different substrates and binding mechanisms of Cu, Zn and Pb in sediments of the tributaries and sediments of the Tisza River. The similarities in the distributions of Fe and Ni in all types of sediments are the result of geochemical similarity as well as of the fact that natural sources mainly affect the concentration levels of these elements. The calculated enrichment factors (EF, measured metal vs. background concentrations) indicated that metal contamination (Cu, Pb, Zn and Cr) was recorded in the sediments of the Tisza River, while no indications of pollution were detected in the tributaries of the Tisza River and the surrounding pools. The maximum values of the EF were close to 6 for Cu and Pb (moderately severe enrichment) and close to 4.5 for Zn (indicating moderate enrichment). It can be said that the Tisza River is slightly to moderately severely polluted with Cu, Zn, and Pb, and minorly polluted with Cr. It is concluded that sediments of the Tisza serve as a repository for heavy metal accumulation from adjacent urban and industrial areas.

Trace elements as tracers of environmental pollution in the canal sediments (alluvial formation of the Danube River, Serbia)

The purpose of this study was to examine the levels of trace elements and to discuss the origin and mobility of these contaminants in the canal sediments (alluvial formation of the Danube River). The most significant fractions binding all of the studied elements were oxides and silicates. The high proportion of elements in the residual fraction and the generally low contents of extractable elements reflected the background geochemical conditions. The contents of trace elements (except Hg and As) were dominantly controlled by the presence of Fe and Mn oxides as well as by the grain size and the geochemical composition of the sediment. The studied alluvial sediments were not heavily contaminated; there were only few sites where an anthropogenic influence on the concentrations of some metals (Cu, Cd, Zn, and Pb) was noticed. The results from this study show that impact of Pančevo industrial zone on the quality of the Danube River and its contamination with trace element is minor.

Aqua regia extracted metals in sediments from the industrial area and surroundings of Pančevo, Serbia.

Surface and buried sediments were analyzed for Ba, Ca, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and V, as well as for total carbon and hydrogen to assess the distribution of sediment pollution due to the vicinity of the petrochemical complex. The samples, collected from 20 locations within the petrochemical complex and from 16 locations outside the complex, were aqua regia extracted and analyzed by ICP/OES. Metals were determined with an acceptable accuracy for certified metals of 82-113%. The precision for the aqua regia extraction was satisfactory, less than 20%, except for Cd where it was 28%. Comparison of the data from the petrochemical with those from the non-petrochemical areas showed different distributions of the metals. Metals that exceeded the baseline range; Ba, Cd, Cu, Zn and Pb, were detected in higher concentrations in sediments that were under the influence of the chlor-alkali plant within the petrochemical complex. Comparison with data from the petrochemical complex and its surroundings and their distribution demonstrated that the metal compositions of the sediments were modified by anthropogenic activities.

Assessment of the contamination of riparian soil and vegetation by trace metals — A Danube River case study

The aim of this study was to assess the spatial distribution of arsenic and heavy metals (Cd, Cr, Cu Hg, Ni, Pb and Zn) in a riparian area influenced by periodical flooding along a considerable stretch of the Danube River. This screening was undertaken on soil and plant samples collected from 43 sites along 2386 km of the river, collected during the international Joint Danube Survey 3 expedition (ICPDR, 2015). In addition, data on the concentration of these elements in river sediment was used in order to describe the relationship between sediment, riparian soil and riparian plants. A significant positive correlation (Spearman r, for p<0.05) was found for trace metal concentrations in river sediment and soil (r=0.817). A significant correlation between soil and plants (r=0.438) and sediment and plants (r=0.412) was also found for trace metal concentrations. Elevated levels of Cd, Cr, Cu, and Ni were found at certain sites along the Serbian stretch, while elevated concentrations of Hg were also detected in Hungary, of Pb along the Romanian stretch and of As along the Bulgarian stretch (the Lower Danube). These results point to the presence of naturally-occurring metals derived from ore deposits in the Danube River Basin and anthropogenic metals, released by mining and processing of metal ores and other industrial facilities, which are responsible for the entry of metals such as Cu, Ni and Zn. Our results also indicated toxic Cd and Zn levels in plant samples, measured at the Hercegsznato site (Middle Danube, Hungary), which highlighted these elements as a potential limiting factor for riparian vegetation in that area. The distribution of the analysed elements in plant material also indicates the species-specific accumulation of trace metals. Based on our results, the Lower and Middle Danube were found to be more polluted in terms of the analysed elements.

Evaluation of sediment contamination with heavy metals: the importance of determining appropriate background content and suitable element for normalization

In the present study, concentrations of heavy metals (Cd, Cu, Co, Mn, Cr, Ni, Pb, and Zn) were determined at 35 river sediments in Serbia. The anthropogenic heavy metals input and quantification of the metal enrichment degree in sediments were estimated by calculating geo-accumulation indices (Igeo) and enrichment factors (EF). These pollution indices have been calculated using different background values (continental crust and local background values) and different element used for normalization (Al and Fe), followed by result comparison. The EF values calculated with continental crust as background (minor to extremely severe enrichment) were higher than when regional background values were used (minor to moderate enrichment). Significant influence of background values on the Igeo values is observed. Values of geo-accumulation index (<2) revealed that studied river sediments are remaining unpolluted to moderately polluted with Co, Mn, Cr, and Ni. Significant pollution in the sediments was observed for Cd, Cu, Pb, and Zn elements. The results of this study confirm the relevance of precise and accurate determining of local background concentrations while assessing sediment pollution. The values of EFs for studied elements were more influenced by the choice of background values than selection of element used for normalization. Our recommendation would be to use the local and regional background content in quantification of metal contamination in sediments, since these values differ and are site and region dependent.

Trace element study in Tisa River and Danube alluvial sediment in Serbia

Abstract The contaminated sediment serves as a long-term source of toxic elements, since that mobility and transport in the environment of these elements are strongly influenced to associated solid phase. In this study, the modified Tessier sequential extraction procedure was applied for the fractionation of Cd, As, Hg, Cu, Zn, Cr, Pb, Ni and V in the sediments (Tisa River and canal sediments - Danube alluvial formation), to obtain an overall classification of trace element pollution in these areas through its spatial distribution. Investigations of this region are important due to the widespread occurrence of metal mining activities throughout the Tisa and Danube drainage basins and possibilities of contamination with toxic elements at studies localities. Five steps of the sequential extraction procedure partitioned elements into CH 3 COONH 4 extractable (F1), NH 2 OHHC carbonate extractable and easily reducible (F2), H 2 C 2 O 4 /(NH 4 ) 2 C 2 O 4 moderately reducible (F3), H 2 O 2 –HNO 3 organic extractable (F4), and HCl acid soluble residue (F5). Analyses of the extracts were performed by flame atomic absorption spectrometry. To indicate the degree of risk of toxic elements, risk assessment code and contamination factor have been used. The results of partitioning study indicate that more easily mobilized forms (metals in adsorbed/exchangeable/carbonate forms or bound to amorphous Fe and Mn oxyhydroxides and Fe and Mn oxides) were predominant for copper, zinc, cadmium and lead, which can be used as indicators for input from anthropogenic source. In contrast, the largest amount of chromium and nickel were associated with the inert fraction, which reduced their solubility and rendered them immobile under natural conditions and indicative of natural origins. Most of remaining portion of metals was bound to ferromanganese oxides fraction. It is concluded that sequential extraction results proved useful to distinguish between anthropogenic and geochemical sources of elements in the sediments.

The electronic properties of trimethylnaphthalenes as properties for the prediction of biodegradation rates: Ab initio and DFT study

There is little information on trimethylnaphthalenes (TMNs) which are constituents of diesel fuel and bitumen emissions. In this study, a theoretical investigation of the electronic properties of all trimethylnaphthalene (TMN) isomers and their relation to biodegradation are presented. Equilibrium geometries, ionization potentials (IPs), electron affinities (EAs), dipole moments and electronic dipole polarizabilities of TMN isomers calculated by ab initio and Density Functional Theory (DFT) methods are reported. Polarizability and dipole moment computations have been performed in gas and in water solution using the polarizable continuum model (PCM). The results obtained show that the IP value varies little along the series of isomers while averaged static dipole polarizabilities () increase on passing from α,α,α-TMN to β,β,β-TMN isomers. This indicates that the binding affinity between TMNs and active site of bacterial enzymes is mainly determined by dispersive and inductive effects. Therefore, the computed polarizability values of TMNs can be used as predictors of the rates of biodegradation of TMNs.

Risk assessment of trace element contamination in river sediments in Serbia using pollution indices and statistical methods: a pilot study

To effectively manage potential environmental and human health impacts of contaminated river sediments, it is important that information about the source (anthropogenic vs geogenic), variability and environmental risks associated with the contamination are well understood. The present study was carried out to assess the source and severity of contamination and to undertake a risk assessment for selected elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) in river sediments in Serbia. The estimate of the anthropogenic component of contamination was derived by determining the total element content and the background values for elements in sediments, and the severity of pollution was assessed by calculating a number of pollution indices including the contamination factor, the enrichment factor, the index of geoaccumulation, the ecological risk factor, the potential ecological risk index, the pollution load index, the combined pollution index, the modified degree of contamination and the toxic unit factor. This analysis indicates that river sediments in Serbia are primarily polluted with Zn, Cu and Cd. The most contaminated river systems are the Ibar, Pek, West Morava and Great Morava rivers. Mining activities were found to have a significant influence on sediment. Multivariate analyses suggested anthropogenic origins for Pb, Zn, Cd, As, Ni and Cu, whilst Fe, V, Mn, Co and Cr appear to have a mixed origin (both lithogenic and anthropogenic sources). A geochemical approach, with a calculation of pollution indices and statistical methods, is recognised as useful for the risk management of trace elements in sediments around the world.

Assessment of arsenic and mercury contamination in the Tisa River sediments and industrial canal sediments (Danube alluvial formation), Serbia

The purpose of this study was to examine the levels of As and Hg and mobility of these contaminants in the sediments of the River Tisa and canal sediments (alluvial formation of the Danube River, Serbia), in order to determine the degree to which the ecosystem is harmed by these pollutants. The sequential extraction procedure (modified Tessier method) was used to extract the metals from the sediments. Arsenic is extracted in the second, third and fifth fraction, with dominant extraction in the second fraction. This distribution indicates that As is significantly present in the form of carbonates, whereas the part of As is present in the form of oxides. The most important extraction of Hg is in the fifth stage (extraction with 6M HCl), with over 80 % of extracted element in both types of sediment, indicating a strong association between Hg and Fe crystalline oxides as well as presence of Hg in the form of sulfides. Based on arsenic and mercury content in sediments and results of sequential extraction it can be concluded that on the studied localities there is no significant As and Hg contamination.

Evaluation of heavy metal contamination in sediments using the method of total digestion and determination of the binding forms-Tisa River Basin, Serbia

This paper describes an approach for the evaluation of metal contamination in sediment, using the determination of binding forms of elements (sequential extraction method), the total element content (digestion method), as well as a comparison of the obtained results with the legislative limits of the EU. Results indicate that silicates are significant substrates for Ni and Cr, whereas Zn, Cd, Pb, and Cu were not dominantly bound to silicates. Mg is present in the form of carbonates and silicates; Fe is in the form of oxides, and Mn is in the form of Mn carbonate and oxides. Zn, Cd, and Cu are dominantly extracted in the labile fractions and because of this they are likely to pose a direct and significant threat to the environment. The results of a comparison with the legislative limits of the EU indicated that in some of the sediments, elevated levels of Zn, Cd, and Cu exist. The contamination was caused by permanent pollution, originating mainly from industrial activities, municipal sewage discharge and agriculture. Results indicate to the significance of the employment both of methods, sequential extraction and total digestion, for metal investigation in sediment. With the aim of protecting the sediment quality of the Tisa River, of importance for Central Europe, the obtained results also indicate the necessity for systematic investigations in all countries through which this river flows.