Predrag Polić

Natural radionuclide emission from a coal power plant and the population exposure to external radiation in its vicinity

Abstract Investigations carried out in the vicinity of four coal-fired power plants showed that the average annual emission of natural radionuclides for each MWe of produced electric power is an average of 0.200 MBq for each component of 238 U chain, and of 0.130 MBq for each component of 232 Th chain, respectively, and of 1.027 MBq for 40 K. The average annual absorbed dose of about 1 mGy was found on five locations studied. The results of specific activity measurements on the samples taken from several locations studied showed that there is a concentration of natural radionuclides in ash and slag of up to about five times. The absorbed dose levels found on depots of ash and slag were close to the values recommended by the International Commission on Radiological Protection.

Association Forms Of Heavy Metals In Fly Ash From Power Plants

During coal combustion, the organic component becomes oxidised, while inorganic components mostly remain in the ash. All natural elements were found in coal, except some very rare ones, like polonium, francium, astatine, etc. (Finkelman 1993). The variability of inorganic constituents is influenced by biological, hydrological and geochemical factors and their association forms govern their behaviour and their technological and environmental impact. Emission and deposition of coal ash represent major environmental problems, due to the large amount of ash obtained. The environmental impact of ash has at least two aspects: a) emission and deposition of enormous amounts of ash particles, polluting air, water and soil; b) leaching of microelements (including toxic metals), but also major cations and anions from ash by atmospheric and surface waters.

Leaching of trace and major elements from coal ash dumps

Coal ash samples taken from an active, currently filled cassette as well as samples taken from passive cassettes of the power plant in Obrenovac (Yugoslavia) were subjected to sequential leaching, comprising of extraction with distilled water, 1 M KC1 and 0.1 M HC1. Concentrations of trace and major elements found in extracts revealed that lead and cadmium are not present in significant concentrations, while other elements show different behavior: practically all absorbed trace elements and most of the major elements are partially leached during transport, while later, on the dump, only a slow release of most of the examined ion‐exchangeable elements occurs.

Alluvial aquifer contamination: Exchangeable heavy metals and factors affecting their spatial distribution

The distributions of ammonium acetate — extracted (‘exchangeable’) Co, Ni, Cu, Zn, Cd and Pb were determined in alluvial sediments of the Sava River at Novi Beograd (Belgrade aquifer, Yugoslavia). Samples were taken from the river bottom and from three drill-holes in the alluvial formation (in increasing distance from the river-bed). The alluvial samples included the quaternary formation — humified surface layers, sands and clays, as well as some samples from the impervious tertiary layer at about 25 m depth. A combined method for the interpretation of results was introduced in order to obtain a clear insight into the factors of heavy metal distribution within the examined aquifer sequence, including elementary statistical methods, as well as factor analysis. There are no significant correlations between metal concentrations and burial depth, river distance, or lithologic type. The application of factor analysis on the exchangeable metal phase, however, reveals the existence of two sample populations and two dominant ecochemical factors, governing the distribution of heavy metals within the aquifer. One factor representssurface contamination, and the other representsriver water influence, accumulating exchangeable heavy metals within a sharply outlined zone. This zone spreads over most layers in the immediate vicinity of the river, as well as over a few, more distant layers which are at roughly the same level as the river-bed.

Speciation of Heavy Metals in Geological Matter of the Serbian National Parks, Protected Areas and Cities Within the Danube River Basin After the War Conflict in 1999

In order to assess the effects of the 1999 NATO bombing of Serbia on the environment, some of the most widespread and feared pollutants, including heavy metals were determined in various sediment samples that were taken from three areas hit by bombing and were previously well-known for its unpolluted environment. Samples of soil and sediments from Fruska Gora National Park as well as Deliblatska Pescara and Zasavica Protected Areas which all lie in the immediate vicinity of the Danube, were investigated by sequential extraction, in order to determine potential substrates of heavy metals and to predict their potential mobilization mechanisms into the environment, especially into surface and ground water flows. This was important because the Danube, one of Europes most important rivers, flows in the immediate vicinity of the National Park and Protected Areas and any contamination could cause severe effects on the rivers ecological status and unpredictable consequences on the countries downstream, including the ecology of the Black Sea. Results show that all three examined areas are polluted with cadmium, the main source of which is projectiles (i.e. their explosions which could contaminate the examined sediments). In Deliblatska Pescara Protected Area there is an increase of highly mobile lead, most probably originating from the bombing of Pancevo oil industry facilities. Radioactivity in examined sediment samples is in the range of values commonly reported from neighbouring countries, suggesting that the contribution of the Chernobyl accident and NATO bombing in 1999 to the total radioactivity in the examined areas is negligible from the health point of view (i.e. that DU ammunition was not used in these areas).

Identification of the substrates of mobile selenium in alluvial sediments of the Sava river

Few facts are known about the biogeochemical cyding of Se, especially in alluvial sediments. Se is a toxic as well as an essential element, and the transformation processes of its various forms-Se(IV), Se(VI), Se, selenide, organic Se--often generate highly complex geochemical association. A sequential extraction procedure (1) was applied on 15 core samples from three drill holes at the Sara river bank (Raney well area) down to a depth of 15 m, as well as on a river mud sample. Se was determined in the ammonium acetate leachate (1. fraction: mobile Se); metals were also determined in the hydroxylamine leachate (2. fraction) and in the oxalate leachate (3. fraction). According to mobile Se content, two subpopulations of sediment samples were identified: I, samples with up to 32 ~g/kg Se; and II, samples with 56-100 ~g/kg Se (mud sample: 84 ~g/kg Se). The mobile Se fraction is associated with various substrates: carbonates, all forms of Fe-hydroxides (especially stable forms), Mn-oxides and hydroxides, unstable Al-species, and organic matter. The uniformity of the mobile Se-distribution in carbonates and in most hydroxide phases indicates a constant, nonanthropogenic input of Se. The nickel content is a good indicator of the mode of Se incorporation into the oxalate-leachable fraction. Silicates were not identified as substrates of mobile Se. The mobile organic Se fraction is mostly associated with recent unstable iron hydroxides (1. and 2. fraction of the sequential extraction).

Metal-organic matter interactions in the formation of an oil shale deposit

Abstract An attempt was made to distinguish metal-organic matter interactions in two types of sulfate-reducing environments, mild (MR) and strong sulfate-reducing (SR), in the Aleksinac oil shale deposit (Oligocene-Miocene). Samples from the MR group show (all differences are statistically highly significant): lower organic matter content, compared with the SR group, higher O/C and N/C ratios (0.147 ± 0.054 and 0.041 ± 0.014, respectively, compared with 0.125 ± 0.031 and 0.035 ± 0.008, respectively, in the SR group), and higher Cu, Zn, Pb, Cr, Mo and Co contents than in the SR group. Statistically significant correlations between metals, the N/C and the SiO2/Al2O3 ratio in the MR group only, represent a record of highly interdependent processes of organic-metal-silicate interactions which had been occurring in the mild sulfate-reducing conditions during oil shale formation.