Identification of the Danube River Basin Specific Pollutants and Their Retrospective Risk Assessment

Abstract

Following the requirements of the European Water Framework Directive (WFD), a process of selecting pollutants relevant at the river basin scale started in 2001. In the Danube river basin, the process was aided by two Joint Danube Surveys (JDS1 and JDS2) organised by the International Commission for the Protection of the Danube River (ICPDR) in 2001 and 2007, respectively. This study was retrospectively analysing all data on organic substances identified in the water samples collected within the two surveys and comparing them to the latest Environmental Quality Standards (EQSs) as well as ecotoxicological threshold values (Predicted No Effect Concentrations; PNECs) that were not available at the time of writing the JDS1/2 Final Scientific Reports. The results showed that 26 out of 89 substances detected in the samples exceeded the EQS/PNEC values in at least one sampling site and 53 substances were found above their limit of quantification (LOQ) at more than five sampling sites within the basin. The above-mentioned 26 substances deserve closer attention as candidates for the list of Danube River Basin Specific Pollutants (DRBSPs). A novel approach of ranking gas chromatography–mass spectrometry (GC–MS) nontarget screening data, based on the assessment of (1) available literature PNEC values (19 substances), (2) derived provisional PNEC (P-PNEC) values (160 substances) and (3) estimated concentrations of tentatively identified substances, has been applied too. Sixty-five out of a total of 179 compounds identified in the JDS samples exceeded the ecotoxicological threshold value in at least one sampling site, which makes them potential candidates for inclusion into future investigative monitoring schemes.