Spatial distribution of PAHs in riverbed sediments of the Danube river in Serbia: Anthropogenic and natural sources

The top layer of riverbed sediments from 10 sites along the Danube River in Serbia were analysed for the presence of polycyclic aromatic hydrocarbons (PAHs). Potential sources of pollution were identified using different multivariate techniques. Total concentrations of 29 PAHs in sediment samples ranged from 128.27 to 676.85 µg/kg dry weight. Based on these concentrations and PAH patterns, a clear spatial distribution of examined localities was determined. The diagnostic ratios indicated a pyrolytic origin of PAHs, except for two sites where PAH contamination originated from petrogenic sources. The Varimax rotated principal component analysis revealed three main factors, namely coal, wood, and biomass combustion; vehicular emissions; and natural sources; accounting for 92.1 % of the variance in the original datasets. The sites with different pollution load, depending on main sources identified, were arranged by hierarchical cluster analysis. The results were compared with sediment quality guidelines, and the obtained values of equilibrium partitioning sediment benchmarks toxic unit and total toxic equivalent quantities of benzo[a]pyrene suggested that Danube sediments do not pose an elevated ecotoxicological risk for benthic organisms.