Petar Pfendt

The point of zero charge and sorption of cadmium (II) and strontium (II) ions on synthetic hydroxyapatite

Abstract Surface properties of synthetic well-crystallized hydroxyapatite were investigated. Points of zero charge (pH PZC ) for different solid to solution ratios were determined by the batch equilibration technique, using KNO 3 as a background electrolyte. It has been found that the decrease in solid to solution ratio from 1:100 to 1:500 leads to a decrease in pH PZC from 6.1 to 4.1, respectively. Sorption of Cd 2+ ions is not influenced by the initial pH value in the investigated range (5–7), while sorption of Sr 2+ -ions, determined in the wider pH range (4.5–11.5), depends only on the initial pH higher than 10, i.e. final pH values higher than 4.5. Negative surface charge established when pH of the solution is higher than pH PZC leads to a more effective cation sorption.

Maturity assessment of oils from the Sakhalin oil fields in Russia : phenanthrene content as a tool

A correlation analysis of maturation parameters was carried out on 14 crude oil samples from nine oil fields on Sakhalin Island (Russia). The oils were taken from reservoir rocks of Miocene age at depths ranging from 73 to 2841 m. On the basis of GC analysis of the alkane fraction (n-alkanes and the isoprenoid alkanes pristane and phytane) as well as on the basis of the abundance of demethylated hopanes (GC–MS analysis, m/z 177), it is assumed that the oils are either biodegraded or are a mixture of biodegraded and nonbiodegraded oils. Therefore, their maturation is assessed on the basis of the distribution and abundance of tricyclic aromatic hydrocarbons that are more resistant to biodegradation than alkane-type biological markers. The oils may be classified into three groups on the basis of the well-established maturation parameter MPI 3: highly mature (group I), moderately mature (group II) and immature (group III). The correlation analysis shows that the percentage of phenanthrene [P] in the tricyclic aromatic fraction of the oils of the Sakhalin oil fields can be used as a maturation parameter. The highly mature oils (group I) were found to have a [P] value of more than 14%; the moderately mature oils (group II) have values of 7–14%, and the immature oils (group III) a value of less than 7%. The very good correlation between MPI 3 and [P] also indicates that parallel to methylphenanthrene isomerization, dealkylation also occurs in the reservoir rocks. By correlation analysis it is shown that these reactions are, to a great extent, determined by the depth of the reservoir rocks.

Characterization of lake sediment humic acids from the Ćelije Lake system near Kruševac (Central Serbia) by13C and 1H solution NMR and 13C cpmas NMR

Humic acids were extracted from the bottom sediment of the three lakes (Zlatari, Vasici and Vodozahvat) that together comprise Lake Ćelije a regional drinking water reservoir. The humic acids were examined by high resolution 13C and 1H solution NMR and 13C CPMAS. The aromaticity expressed as the number of benzene rings per 1000 g of humic acid is 1.8 for Zlatari, 2.3 for Vasici and 1.9 for Vodozahvat. Oxygen-substituted aromatic carbon structures in humic acids from the first two lakes (Zlatari and Vasici) are similar and resemble p-coumaryl units in lignin while those in Lake Vodozahvat more closely resemble coniferyl or sinapyl units in lignin. The aromatic rings of all three humic acids are highly substituted. Humic acids from the first two lakes have very similar carbohydrate carbon contents (19.9 and 19.5% respectively) compared to 23.3% for Vodozahvat humic acid. Zlatari and Vodozahvat humic acids have a higher alkyl chain content which indicates a greater potential for forming hydrophobic cavities. The carboxyl and aromatic OH group content of each humic acid influences their capacity for forming complexes with metal ions.

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.

Indication of reducing conditions in early diagenesis: The Aleksinac oil shale as example

Abstract An attempt was made to define the early diagenetic reducing conditions in the Aleksinac oil shale deposit, a freshwater lake sediment of Upper Oligocene-Lower Miocene. This deposit consists of three zones: northern, central and southern zone. 171 samples from 25 cores were investigated, originating from various depths, i.e. 9–720 m. Several potential indicators of reducing conditions were correlated, such as the atomic O/C ratio of the organic matter, the content of pyritic sulfur (S pyr ) and the content of organic carbon (C org ). In most of the layers the concentration of sulfate was found to be limiting factor for development of sulfate-reducing conditions corresponding to the content of the organic substance during diagenesis. The intensity of reducing conditions in the presence of sufficient amount of sulfate (the critical concentration of residual sulfate being 2.0–2.5 mmol/100 g), clearly depended on the concentration of organic matter in the sediment, but also on the conditions in the water column. A greater variety in the intensity of reducing conditions during early diagenesis was observed in the North and Central zones, while in the South zone during the whole early diagenesis the conditions probably were markedly sulfate-reducing. In the North and Central zones milder and more pronouncedsulfate-reducing conditions varied, involving occasional shifting of the anoxic zone into the water column. The highest frequency of pronounced reducing conditions was observed in the middle (150–340m) and upper (40–70m) layers. Indications of further intensification of reducing conditions leading to methanogenesis were not clearly observed.

Fulvic acid characterization in an alluvial sediment sequence: differences between clay and sand environments

Abstract Fulvic acids (FAs) from the whole Quaternary sequence (to a depth of 26 m) of the alluvial sediment of the Sava river (taken from a site in Novi Beograd, Belgrade, Yugoslavia) were investigated with the aim of examining the effect of the environment (clay or sand) on their characteristics. Characterization of the FAs was carried out by correlating the results obtained by various instrumental techniques (u.v.-vis. and i.r. spectroscopy, fluorimetry). Differences were noticed between the FAs, depending on whether they originated from sand or clay, which indicates that the hydrogeological environment represents an important factor in determining their characteristics, though the role of the precursor material may be significant. FAs found in clay layers are less aliphatic, have a greater non-aliphatic hydroxyl group content and exhibit more similar fluorescence ntensities compared to FAs originating from sand. The greater mutual similarities of the clay FAs in comparison to those from sands is a result of diagenesis occurring in a more “closed” system.

Comparison of the general chemical nature of various kerogens based on their reactivities towards bromine

Abstract It was found that data obtained by bromination of kerogens, such as the amount of bromine consumed and the amount of hydrogen bromide liberated, in combination with data obtained by ultimate analysis (C, H) provide a basis for a more detailed comparison of the chemical nature of fossil organic materials than the one on the basis of O/C-H/C ratios only. Kerogens of the following shales were investigated: Estonian Kukersite (Middle Ordovician), Australian Torbanite (Permian-Carboniferous), Kimmeridge shale, Dorset, U.K. (Jurassic), Colorado shale (Eocene, Green River Formation) and Aleksinac shale, Yugoslavia (Oligocene-Miocene). The kerogens were compared with each other as well as with their benzene bitumens, and one sample of petroleum asphaltenes. The data obtained by bromination and by elemental analysis were introduced into an atomic C/Br vs H/HBr diagram, divided into nine areas by means of bromination lines H/HBr = α(C/Br), obtained on the basis of theoretical consideration of the behaviour of eight structural models of fossil organic materials towards bromine. The order of areas occupied by kerogens in the C/Br vs H/HBr diagram, from left to right, i.e. starting with lower C/Br values towards higher values, strictly followed the arrangement of the kerogens in the Van Krevelen diagram. However, in the C/Br vs H/HBr diagram details were observed which were useful for a closer characterization of the chemical nature of the organic matter. Two principal indicators of the chemical nature of the organic substances were found: (a) the distance of the position of an investigated substance from the beginning of the coordinating system (C/Br vs H/HBr diagram), and (b) the region which an investigated substance occupies between two bromination lines.

Diagenetic relationships between sulphur species and formation of pyrite in coals and Sediments

Abstract Based on the abundant minerals in a Miocene freshwater sequence of mixed sediments (pieces of coal in clays, sand-stones and shales) alternating with coal layers, the following main sedimentation environments were distinguished: illite-montmorillonitic (I-M), calcitic (Ct) and coal-forming environment. Applying factor analyses to 16 geochemical parameters, an environmentally-specific early diagenetic connection between the sulphur transformation processes, amount of Corg and precursor material species (C27-C29-steranes) was determined. It was found that the effects of limiting factors on Spyr formation depended on the hydrogeochemical conditions of individual sedimentation environments. Pyrite formation in coals depended directly on participation of higher plant precursor materials and/or on the total sulphur content in the system. In the MS, pyrite formation directly depended on total sulphur content, hydrogeological conditions and the amount of Corg.

Characteristics of wintertime polycyclic aromatic hydrocarbon assemblage in aerosol of the Southern Adriatic

Features of polycyclic aromatic hydrocarbon (PAH) assemblage in aerosol samples collected from the atmosphere of Herceg Novi during the winter months of two successive years were studied. The results showed almost the same concentration profiles of identified PAHs for samples from the two periods analyzed, generally suggesting a similar origin. Diagnostic ratios indicated combustion of wood and coal, emissions from petrol and diesel engines, and dust resuspension as sources that predominantly contributed to the atmospheric PAH concentrations. Statistical analysis, principal component analysis (PCA) in particular, allowed us to identify the impact of meteorological parameters on PAH abundance.

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).