B. Jovančićević's research while affiliated with University of Belgrade and other places

In Sečovlje Salina Nature Park, the therapeutic mud matured in the natural sedimentary environmental site. This work aimed to determine the influence of the peloid maturation process on the hydrocarbon and elemental distributions, as well as changes in morphology. For this purpose, the sample before and after maturation was examined using various methods. n-Alkanes were the most abundant among saturated hydrocarbons in both immature and mature peloid samples. The results showed that the maturation mainly influenced the change in distribution and concentration (from 378 to 1958 ppm) of n-alkanes. The organic matter (OM) of the immature peloid sample was characterized by a slight prevalence of long-chain and odd carbon-numbered n-alkanes, maximizing at n-C27. However, mature peloid's OM showed a similar share of short-, mid- and long-chain n-alkanes with a slight dominance of short-chain members, maximizing at n-C16. The origin of short-chain and even carbon-numbered n-alkanes was attributed to microbial precursors (e.g., Leptolyngbyaceae). Hopanes were considerably more dominant compared to steranes in both peloids. The hopane series of immature peloid was characterized by the dominance of 22,29,30-trinor-hop-5(6)-ene (C27 hopene), as well as the presence of C30-hop-22(29)-ene (diploptene), which are widespread in cyanobacterial species. The aromatic fraction of immature peloid pointed to the predominance of polycyclic aromatic hydrocarbons (PAHs). As peloid aging progressed, the sample was richer in methyl-branched alkanes, carboxylic acids, their methyl esters, and thermodynamically more stable hopanes and steranes. The presence of elements with toxicological relevance during maturation was reduced below the limits prescribed in most of the directives for cosmetic products. It specifically refers to: As, Ni and Se. A higher concentration of total sulfur in the mature peloid can be related to gypsum precipitation in the summer and/or more intensive microbial activity.

https://www.earthdoc.org/content/papers/10.3997/2214-4609.202134040

A detailed evaluation of geochemical properties of oil shale samples from the outcrops of the Lower Miocene upper layer in the Dubrava area, Aleksinac basin, Serbia, was performed. For that purpose X-ray diffraction (XRD) analysis, Rock Eval pyrolysis, gas chromatography-mass spectrometry (GC-MS) analysis of biomarkers and conventional pyrolysis in an autoclave were used. Most of the samples have similar mineral compositions with predominance of clay and feldspar minerals. Three samples are characterised by an elevated content of carbonates, and among them one sample has a notable prevalence of this mineral group. This sample also demonstrated certain differences in biomarker distribution. In most samples organic matter (OM) consists predominantly of type I and II kerogens, showing high oil generative potential, whereas three samples, which contain type II kerogen with a certain input of type III kerogen, demonstrated potential to produce both, oil and gas. The OM of all samples is immature and corresponds to the vitrinite reflectance of ca. 0.40%. Biomarker patterns along with Rock-Eval data indicated a strong contribution of aquatic organisms such as green and brown algae and bacteria with some influence of higher plants OM. The organic matter was deposited in a reducing lacustrine alkaline brackish to freshwater environment under warm climate conditions. Preservation of OM was governed by stratification of the water column rather than its height. Tectonic movements that caused the regional tilting of an investigated area and supported minor marine ingression and influx of fresh water played an important role in formation of the sediments. Conventional pyrolytic experiments confirmed that these sediments at the catagenetic stage could be a significant source of liquid hydrocarbons.

In this study the concentrations of metals were investigated in Phragmites australis (Cav.) Trin. eh Steud. 1841 and sediment samples from the bed of the River Tisza in Serbia. Al, As, B, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sr and Zn levels were analyzed using inductively coupled plasma – optical emission spectrometry. The sediment samples contained elevated concentrations of cadmium, chromium, copper, nickel and zinc. The increased concentration of these metals had no significant effect on wildlife of the river Tisza as the determined concentrations of the metals tested in the comon reed do not exceed the threshold of phytotoxicity. The research proved a strong positive correlation between the concentrations of metals in the sediment and all common reed organs (rhizome, stem and leave). Accumulated metals in the common reed are not distributed evenly, but there are target organs for bioaccumulation. Concentrations in belowground organs were usually higher than aboveground organs, and the general decreasing trend of element content was rhizome>leaves>stems.

The possibility of using the data on the hydrocarbon composition obtained by analysis of hydrocarbon concentrates for geochemical studies has been shown on the example of Pannonian Basin (Serbia) crude oils of different genetic types and different degrees of thermal maturity and biodegradation. A high convergence of the values of geochemical parameters calculated on the basis of the composition of steranes and terpanes, alkylnaphthalenes, phenanthrenes, and dibenzothiophenenes in hydrocarbon concentrates and chromatographic fractions isolated from them has been found by correlation analysis.

This paper reports an investigation of 60 samples of lacustrine sedimentary rocks of Neogene age lying at depths of 0–400 m in the Valjevo-Mionica Basin, Serbia. The goal of the study was to determine the origin and type of primary organic matter (OM), the degree of thermal alteration, the generation potential of OM from the rocks of this basin, and conditions in the sedimentation environment during the formation of the rocks. The potential of OM of the rocks was estimated on the basis of the thermolysis of a representative sample after its preliminary debituminization. Using data on Corg and bitumen contents and S1, S2, and HI Rock-Eval pyrolysis parameters, the samples were divided into three groups. The first and second groups include rocks recovered from depths up to 200 m, and the third group comprises samples from depths of 200–400 m. The investigation of the inorganic constituents of the rocks and biomarker composition showed that the samples of each of these groups were formed under significantly different climatic conditions, which influenced both the composition of primary organic matter and the conditions of the sedimentation environment, which eventually affected the abundance and quality of OM in the rocks. The yield of the liquid fraction and concentration of hydrocarbons obtained during the thermolysis of the debituminized sample of the first group (showing the highest Corg content), the character of n-alkane and sterane distribution in the saturated fraction of thermolysis products, and the thermal maturity indices calculated from the composition of steranes supported the high generation potential of OM from these rocks.

Free and associated bitumens were isolated by sequential extraction from Vlasina lake peat (SE Serbia) and were investigated in order to differentiate between oil pollution and natural bitumens. Four peat samples were collected at different depths, on a peat island. Gas chromatographic (GC) and gas chromatography/mass spectrometry (GC/MS) analysis revealed the presence of three markedly different bitumen fractions. Here we show that the free bitumens are representing the native peat bitumens. The two associated bitumens are mainly the products of bacterial rework of organic substance, which were then trapped by two differing mechanisms. The bitumens characteristics and association features exclude a contribution of oil pollution.

The average structural characteristics of oily and resinous components of nine crude oils of various types from different Miocene horizons of the Sirakovo and Bradarac-Maljurevac oil fields (Serbia), as well as the mass-spectrometrically established hydrocarbon-group composition of these oils, are described. The most abundant components of crudes from both oil fields are mono- and bicyclanes bearing long alkyl substituents. It was found that there is no universal trend in the chemical type of the oils with the occurrence depth of the producing zones in these fields, that is, oils are enriched in aliphatic hydrocarbons with depth in the Sirakovo oil field and in naphthene hydrocarbons in the Bradarac field. These trends cannot be explained by microbial degradation processes or by the catagenetic alteration of petroleum composition in the Earth's interior and indicate a low level of thermal maturity of the source organic matter that gave rise to the hydrocarbon systems in question. A certain parallelism of variation in the structural parameters of hydrocarbonaceous and heteroorganic (resinous) components of the oils depending on natural factors is noted.