Water-quality indicators and trace elements were measured in the alluvial area of the Kostolac Basin, Serbia. The results revealed that the groundwater was naturally neutral, with a mean conductance of 920.10 μs/cm. The primary factors contributing to the decline in the groundwater quality in the researched area were electrical conductivity (EC), NO₃⁻, SO₄²⁻, Cd, and Pb; the water samples were deemed unfit for human consumption and the water was classified as having impaired quality. A Pearson correlation matrix, a principal component analysis (PCA), and a cluster analysis (CA) were applied to identify the pollution source and factors controlling the groundwater quality and the results indicated that both natural and anthropogenic factors influenced the groundwater of the studied area. The Nemerow pollution index indicated medium to high pollution levels along with the degree of contamination. A health risk evaluation was conducted to determine the non-carcinogenic risks posed by nitrates and heavy metals from oral consumption and skin contact in the researched area. Nearly all monitoring sites had hazard quotients (HQs) below 1, suggesting that potential concerns might be negligible. However, children showed the highest exposure levels, with HQs for nitrates at 2.26 and for lead (Pb) at 2.515. No carcinogenic risk from oral lead (Pb) exposure was found in any sample.

Concentrations of 10 potentially toxic trace elements were measured in soil samples collected from 18 sites in urban areas of Belgrade, the capital and the largest city in Serbia. Samples were analysed in order to assess the extent of soil contamination and to distinguish natural and anthropogenic input. The results demonstrated a general Zn, Pb, and Cd enrichment in surface samples, hence, after comparison with guidelines, it has been determined that there is a potential risk for human health. In the surface and buried samples, traces of cooper were detected. The highest concentrations of Cr (121 ± 12.3 mg/kg) and Ni (94.9 ± 12.6 mg/kg) were found at a sediment depth of 2 m and should be ascribed to geogenic sources. The results of HCA and PCA analysis supported a natural origin of Co, Cu, Mn, Cr, and Ni, while Cd, Zn, and Pb originated from anthropogenic inputs. Based on the pollution indices, Cd made the most dominant contribution, posing a high contamination risk in the studied area. Results of Nemerow pollution index (PI_N) and potential ecological risk index (PER) demonstrated that pollution by heavy metals in sediments on several sites is moderately intense.

Eight samples of powdered brown coal (Krepoljin coal basin, Miocene age) were successively extracted by two extractants at room temperature: bidistilled water, Me1, and 2 M MgCl₂ solution, Me2. Large amounts of Ni and Zn are leached from the coal deposit by water. On the contrary, no significant amounts of Pb and Cu are washed under normal conditions. Also, the mobility of Zn and Ni especially depends, to a high extent, on ionic strength. It can be assumed that the humic acids co-extracted during water leaching, Me1, and being a highly competitive ligand for metal ions, will act as a disturbing agent in metal speciation procedure in coals. This assumption is supported by the obtained significant correlation between the Me1:Me2 ratio and the humic acid complex stability constants.

The characteristics of early diagenetic processes, which influenced the composition of the organic matter of coals from the Krepoljin coal basin, Serbia, Miocene age was assessed by statistical correlation analysis and multivariate principal component analysis. The complexity of processes in a coal-forming sedimentary environment has been paid special attention to obtain the most possible reliable interpretation of these early diagenetic processes and, therefore, this investigation was performed by applying principal component analysis. The principal components, which are defining the coals and promoting individual early diagenetic processes, were the precursor materials and environmental factor, respectively, represented by higher plants, algae, and molds—expressed by the relative contents of the Cs₂₉-, Cs₂₈-, Cs₂₇-steranes, respectively, and the content of organic sulphur—Sorg, average content 166 ± 101 μmole/g. The main and highly interrelated effects of the higher plant material were as follows: (i) increase of the sulphur content of coal organic matter, (ii) promoter of sulphate reducing conditions, and (iii) establishment of the H/C- and N/C-ratios of organic matter. Pyrite formed by the participation of Sorg.