Comparison of contamination by polycyclic aromatic hydrocarbons, pesticides and pharmaceuticals in abandoned meanders and channel bars, Czech Republic

This article focuses on the necessity to enhance the current understanding of the accumulation and fate of pesticides and pharmaceuticals (emerging pollutants) in abandoned meanders and adjacent river channel bars. The primary objective of this study is to conduct a comparative analysis of pollutant concentrations in both settings and to identify the driving factors of their deposition. The studied sites are situated within two distinct catchments of the Morava and Odra rivers in the eastern part of the Czech Republic. The most prevalent pesticides were identified as propiconazole, metazachlor and tebuconazole. For caffeine and pharmaceuticals, the peak concentrations exceeded 10 µg/kg. The other pharmaceuticals frequently detected in these sediments were carbamazepine, diclofenac and metoprolol. The polycyclic aromatic hydrocarbons and polychlorinated biphenyls, selected for comparison (hereafter referred to as 'legacy pollutants'), reached high to extremely high levels due to their frequent use in the past or present. Pollutant assemblages differed between channel bars and abandoned meanders. The maximum concentrations of emerging pollutants have been observed to be generally higher in abandoned meanders; however, the relative occurrence of pollutants has been found to be higher in channel bars. Abandoned meanders are most vulnerable to contamination in the first years following the cut-off, due to the increased frequency of flooding during this period. Consequently, they pose a higher environmental risk. Older meanders contain residual concentrations of pollutants and can serve as long-term sinks for organic pollutants, thereby providing temporal patterns. Conversely, channel bars represent current contamination levels and thus indicate spatial trends.