Mixtures of chemicals are important drivers of impacts on ecological status in European surface waters

Abstract

The ecological status of European surface waters may be affected by multiple stressors including exposure to chemical mixtures. Currently, two different approaches are used separately to inform water quality management: the diagnosis of the deterioration of aquatic ecosystems caused by nutrient loads and habitat quality, and assessment of chemical pollution based on a small set of chemicals. As integrated assessments would improve the basis for sound water quality management, it is recommended to apply a holistic approach to integrated water quality status assessment and management. This allows for estimating the relative contributions of exposure to mixtures of the chemicals present and of other stressors to impaired ecological status of European water bodies. Improved component-and effect-based methods for chemicals are available to support this. By applying those methods, it was shown that a holistic diagnostic approach is feasible, and that chemical pollution acts as a limiting factor for the ecological status of European surface waters. In a case study on Dutch surface waters, the impact on ecological status could be traced back to chemical pollution affecting individual species. The results are also useful as calibration of the outcomes of component-based mixture assessment (risk quotients or mixture toxic pressures) on ecological impacts. These novel findings provide a basis for a causal and integrated analysis of water quality and improved methods for the identification of the most important stressor groups, including chemical mixtures, to support integrated knowledge-guided management decisions on water quality.

Mixture toxicity in the Erft River: assessment of ecological risks and toxicity drivers

“…These substances, however, can vary seasonally and regionally, which was also observed in this study. Therefore, even if only a few substances are the main contributors to the mixture toxicity, a high number of substances need to be analysed in order to obtain a comprehensive overview of the mixture risks in surface waters [36,37].…”

A holistic approach is key to protect water quality and monitor, assess and manage chemical pollution of European surface waters

“…Although the WFD was published in 2000, a good water quality status was not yet reached in 2012 and 2018 in a large fraction of Europe's surface waters [5,12]. Chemical pollution poses a lasting and diversifying problem to surface water quality [7], together with the aforementioned other stressors [13].…”

“…The diagnostic methods are summarized and characterized in the other SOLUTIONS Policy Briefs. For example, methods can be selected for early-stage exploratory assessments on the presence of chemicals [19], via refined component-and effect-based diagnostic approaches of impacts [20,21] to specific biological quality elements [22] and the ecological status [13], up till integrated modeling [23]. The methods cover the full array of the DPSIR-causal approach (Fig.…”

Solutions for present and future emerging pollutants in land and water resources management. Policy briefs summarizing scientific project results for decision makers

“…1) as well as several Spanish river basins and a number of additional field sites all over Europe and discussed with European and national agencies, international river commissions and many more important stakeholders. By integrating the SOLU-TIONS monitoring and modeling tools with multiple stress investigations carried out in the MARS project [14], it could be shown that mixtures of chemicals are actually important drivers of impacts on the ecological status in European surface waters [15].…”