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In this study, pyrolysis and co-pyrolysis of commonly used plastic materials (polyethylene terephthalate – PET, high density polyethylene – HDPE, and polystyrene – PS) were conducted to analyse the chemical composition of the corresponding pyrolyzates. Different ratios of plastic materials were applied to obtain a composition of aliphatic and aromatic degradation products that closely resemble those of conventional fossil fuels. The systematic chemical variations can act as base for evaluating this approach as a sustainable source of alternative fuels. HDPE revealed an aliphatic composition of degradation products, while PS and PET produced only aromatic compounds. Quantitative analysis of the obtained pyrolyzates revealed a clear correlation of initial proportion with the resulting quantitative product composition. The generation of individual pyrolysis products gave a high reproducibility. However, it became evident that the decomposition products of PS consistently emerged as the most prominent among all tested HDPE/PS mixtures. The ratio of HDPE:PS = 1:3 showed 96 % of the aromatic compounds as PS decomposition products. PET revealed a oxygen containing structure of the products, contributing to 83 % of the HDPE:PET = 1:3 mixture. These results gain insights into the potential of plastic waste as a sustainable source for alternative fuels and valuable chemicals.

This study is focussed on a comprehensive investigation on the state of pollution of Danube and Sava rivers in Belgrade region. Different complementary analytical approaches have been used covering both (i) organic ccontaminants in river water by target analyses of hormones and neonicotinoids as well as non-target screening analyses and (ii) heavy metals in sediments. Finally, some common water quality parameters have been analysed. The overall state of pollution is on a moderate level. Bulk parameters did not reveal any unusual observation. Also quantification of preselected organic contaminants did not point to elevated pollution. A more significant contamination was measured for chromium, nickel, zinc and partially copper in sediments with values above target values according to Serbian regulations. Lastly, non-target screening analysis revealed a wider spectrum of organic contaminants comprising pharmaceuticals, technical additives, personal care products and pesticides. The study presented a comprehensive view on the state of pollution of Sava and Danube rivers and is the base for setting up further monitoring programs. As a superior outcome it has been illustrated how different chemical analyses can point to different assessments of the river quality. The comparison of target and non-target analyses pointed to potential misinterpretation of the real state of pollution.

It is well known that during biodegradation of oil in natural geological conditions, or oil pollutants in the environment, a degradation of hydrocarbons occurs according to the well defined sequence. For example, the major changes during the degradation process of n-alkanes occur in the second, slight and third, moderate level (on the biodegradation scale from 1 to 10). According to previous research, in the fourth, heavy level, when intensive changes of phenanthrene and its methyl isomers begin, n-alkanes have already been completely removed. In this paper, the ex situ natural bioremediation (unstimulated bioremediation, without addition of biomass, nutrient substances and biosurfactant) of soil contaminated with heavy residual fuel oil (mazut) was conducted during the period of 6 months. Low abundance of n-alkanes in the fraction of total saturated hydrocarbons in the initial sample (identification was possible only after concentration by urea adduction technique) showed that the investigated oil pollutant was at the boundary between the third and the fourth biodegradation level. During the experiment, an intense degradation of phenanthrene and its methyl-, dimethyl-and trimethyl-isomers was not followed by the removal of the remaining n-alkanes. The abundance of n-alkanes remained at the initial low level, even at end of the experiment when the pollutant reached one of the highest biodegradation levels. These results showed that the unstimulated biodegradation of some hydrocarbons, despite of their high biodegradability, do not proceed completely to the end, even at final degradation stages. In the condition of the reduced availability of some hydrocarbons, microorganisms tend to opt for less biodegradable but more accessible hydrocarbons.

"On-line" pyrolysis coupled with gas chromatography (GC) was performed for quantitative determination of poly(vinylpyrrolidone) (PVP) in wastewater sample. Gas chromatography-mass spectrometry (GC-MS) showed that the main product of pyrolysis of PVP, at high temperatures, is N-vinylpyrrolidone (NVP). After that, different amounts of commercial PVP were pyrolyzed in order to establish correlation between the amount of generated NVP (its GC peak area) and the initial mass of pyrolyzed PVP. GC-FID analysis was used for construction of calibration curve and for quantitative determination of PVP. Very good linear correlation was obtained between the area of NVP peak, generated during pyrolysis, and the initial mass of PVP (r2 = 0.998). Further, solutions of known concentration of PVP were prepared in destilled water ("spiked samples"). Spiked samples were preextracted with diethyl ether and n-hexane, and after that, the water-layer was evaporated and dissolved again in methanol. Analysis of pyrolysates of preextracted spiked samples showed that the "recovery" of PVP was above 96 mas%. This finding suggested that pre-extraction could be applied to reduce the concentration of organic substances that could also be pyrolyzed, and thus hinder identification and quantitative determination of PVP, without significant loss of polymer. The sample of an industrial wastewater from Pančevo, Serbia was investigated in the last part of this work. The sample was preextracted in the same way as the spiked samples and than pyrolyzed. NVP was identified by GC-MS in obtained pyrolysate, which was the evidence that PVP was present in the wastewater sample. NVP was quantified on the basis of the peak area in GC-FID chromatogram, and than the concentration of PVP in wastewater sample was calculated based on calibration curve. Concentration of PVP in industrial wastewater amounted 2.5 mg/L.

Twenty-five crude oils originating from the Velebit oil field (SE Pannonian Basin), the most important oil field in Serbia, were investigated. Saturated biomarkers (n-alkanes, isoprenoids, steranes and triterpanes) were analyzed by gas chromatography-mass spectrometry (GC-MS). Based on the distribution and abundance of these compounds, a large number of source and maturation parameters were calculated, particularly those most often used in correlation studies of oils. The examined samples were classified according to their origin and level of thermal maturity using factor, cluster and discriminant analyses. According to the source and maturation parameters, combined factor and cluster analyses using the Ward method enabled the categorization of the investigated oils into three groups. The cluster Ward analysis was shown to be of greater susceptibility and reliability. However, in addition to the two aforementioned methods, K-Means cluster analysis and discriminant analysis were shown to be necessary for a more precise and detailed categorization in the case of a large number of samples in one group. Consequently, it was concluded that factor and cluster K-Means and Ward analyses can generally be used for the interpretation of saturated biomarkers in correlation studies of oils, but the observed results have to be checked, i.e., confirmed by discriminant analysis.