Applied, collaborative, interdisciplinary research on a European scale
The EU-funded projects SOLUTIONS, MARS, and GLOBAQUA with a total funding volume of over 20 million Euro and comprising 80 leading scientific institutes from 23 European countries together with partners from Australia, Brazil, China, Turkey and Morocco provided the critical mass to successfully overcome the interdisciplinary challenges of monitoring, assessment and protection of European water resources as established in the WFD and the EU strategy for a non-toxic environment. The balance between individual objectives and approaches of the projects and intensive exchange and collaboration between the projects allowed for overarching conclusions directly informing decision making in the catchments and in European regulation. That is, MARS developed an overarching concept to assess how multiple stressors affect surface water and analysed stress data at the European, at the catchment and at the water body scale, providing methods to support improving ecological status in a multiple-stress context. SOLUTIONS contributed a comprehensive picture of contamination and toxic stress in European catchments using predictive modelling based on emission data as well as monitoring of complex mixtures and effects at the watershed scale in major European river basins including those of the Rivers Danube, Rhine and Ebro. GLOBAQUA studied multiple stressor effects in rivers of southern Europe such as the Adige, Evrotas and Sava, providing methods to tailor the aforementioned approaches to water systems under water scarcity scenarios. Together, the projects provided methods to monitor, assess and manage chemical mixtures and other stress that allow for advanced assessment of both chemical safety and ecological status. Collaborative modelling and monitoring data assessments across the three projects revealed that chemical mixtures occur as one of the prevailing factors for determining the ecological status in many rivers. Pollutants collectively contribute in multiple stressor settings to a similar degree as nutrients, hydrology and riparian land use, with a spatiotemporal variability that relates to land use and season. To better understand toxic stress under water scarcity as an increasing challenge under climate change, SOLUTIONS and GLOBAQUA closely collaborated on the Iberian Peninsula and were able to demonstrate the intensifying role of climate change on the environmental impact of chemicals. These results, which emerge from collaborative, interdisciplinary European research, suggest that the separate consideration of chemical contamination (status) and ecological status needs to and can be overcome to achieve the goals of the Water Framework Directive (WFD).
Although strongly focused on fulfilling societal and regulatory demands, applied research, as it has been performed in the three European projects, addresses the full chain of knowledge from basic understanding of scientific processes via monitoring and assessment tools to the formulation of recommendations for protection and management efforts by all stakeholders, supported by a comprehensive set of policies. This may be illustrated by the monitoring of toxic stressors in European water bodies as performed in SOLUTIONS. Starting with the collation and investigation of modes of action and toxicogenomics of known water contaminants [38, 39], an effect-based monitoring strategy and the corresponding toolbox  were developed, rigorously evaluated and adapted using selected chemicals , mixtures  and field samples . Through extensive stakeholder dialogue, policy-related working groups, workshops, via scientific and popular publications plus close collaboration with relevant science–policy interaction networks such as NORMAN, the new concepts were discussed, refined and integrated in the decision-making processes regarding the review of WFD .
Solution-based approaches in monitoring, assessment and management of risks of complex chemical mixtures and multiple stressors
While current evaluations of chemical pollution in European surface waters focus on problem description and water quality classification, the projects SOLUTIONS, MARS and GLOBAQUA put emphasis on early exploration of prevention and abatement options considering the remedial space within the Drivers–Pressure–State–Impacts–Response (DPSIR) causal approach . To facilitate solution-focused risk assessment , a conceptual framework has been developed . The early consideration of possible responses is supported by a database on technical abatement options  and a systematic evaluation of non-technical abatement options. SOLUTIONS-focused assessment of multiple stressors is supported by the SOLUTIONS’ Tools and Services for River Basin Toxicants Assessment and Management accessible through the web-based guidance tool RiBaTox (https://solutions.marvin.vito.be/ ) and by a living database architecture for the exchange of chemical and effect-based monitoring data . Moreover, a scenario analysis tool developed by MARS provides indications on how stressor intensity and ecological status will develop under given scenarios of human impact at the European scale and broken down to more than 100,000 sub-catchments in Europe (https://mars-project-sat.shinyapps.io/mars-sat). In addition, a diagnostic tool developed by MARS assists water managers to identify the main stressors affecting the ecological status, and to derive appropriate management measures (http://freshwaterplatform.eu/index.php/mars-diagnostic-tools.html). GLOBAQUA developed ESPRES (Efficient Strategies for anthropogenic Pressure Reduction in European waterSheds, http://www.globaqua-project.eu/en/content/ESPRES-tool.94/), a web-based decision support tool that can be employed to explore management options for achieving environmental targets of European water bodies. The user-friendly web interface supports multi-criteria river basin analyses via DPSIR-based causal analysis steps to identify efficient pressure reduction strategies and reflecting the perception of stakeholder efforts, which includes monetary costs, political difficulty, and social acceptability of available solutions. Monitoring and assessment of ecosystem goods and services such as river ecosystem functioning have been addressed by GLOBAQUA and recommended as a crucial module to be included in the existing river monitoring and assessment schemes . The resultant toolbox is accessible (http://www.globaqua-project.eu/en/content/Toolbox-for-ecosystem-functioning.50/).
Success measures towards a non-toxic environment and sustainable cities and landscapes
While global boundaries have been defined as the safe operating space for humanity , ecological, energy, carbon and water footprints have been introduced to quantify the appropriation of natural resources by humans within these boundaries [46, 47], typically at a regional scale. Chemical footprints as applied in SOLUTIONS were likewise developed as an indicator of the cumulative impacts of chemical mixtures on biodiversity and represent the approximation or exceedance of a contamination level considered as safe . They are recommended to be used to evaluate trends in chemical contamination and may help selecting best options for abatement scenarios, as well as to communicate complex data sets on mixture exposures and effects . To anticipate the effectiveness of interventions, the perspectives of the water cycle and the chemical life cycle were connected by providing a mitigation database coupled to hydrological models .
River basin scale case studies were instrumental to benchmark performance of modelling and measurement tools for water contamination assessment, provided data necessary to identify river basin-specific pollutants, demonstrated the benefits of the technical upgrade of wastewater treatment plants, specified the potential for targeted remediation of pollution sources, and demonstrated the interactions between contamination and situations of water scarcity that need to be acknowledged. In particular, we sought to conceptually provide links for bridging between chemical and ecological water status measures [49,50,51]. This includes the identification and ranking of environmental hazards with ecosystem vulnerability distributions . Thus, we overcame a major hurdle in current water quality assessment, where ecological and ecotoxicological assessments and recommendations are derived independently, based on different principles (protection vis a vis protection and impacts) leading to diverging, if not contradictory advice for river basin management.
Science–policy interaction and stakeholder dialogue
Starting in the proposal phase, a systematic and structured dialogue with diverse stakeholders was established in the three collaborative projects SOLUTIONS, MARS and GLOBAQUA. It involved major stakeholders in the fields such as DG Environment, European Environmental Agency (EEA), European Chemical Agency (ECHA), European Food Safety Authority (EFSA), International River Commissions such as International Commission for the Protection of the Danube River (ICPDR) and the Rhine (ICPR), national environmental and chemical agencies, water industry, and NGOs. The structured stakeholder dialogue led to joint activities and developed new options. For example, SOLUTIONS provided the compilation of river basin-specific pollutants suggested for the Danube River Basin Management Plan and provided conceptual and technical input as well as case study evidence to the sub-group for effect-based methods of the CIS Working Group Chemicals under DG Environment. MARS with stakeholder participation developed conceptual models on how the relevant multiple stressors affect water body status in sixteen case study catchments and subsequently used the outcome for producing predictive models. The results were discussed in a specific workshop with the Common Implementation Strategy (CIS) Working Group ECOSTAT of DG Environment. A moderated e-learning course for policy makers and river basin managers was provided to translate scientific understanding for end users (http://www.globaqua-project.eu/en/content/E-Learning.93/).
In summary, the three projects SOLUTIONS, MARS and GLOBAQUA provided well-structured and complementary contributions to the EU policy goals on sustainable management of water resources. Acknowledging a growing world population with growing demands for agricultural, industrial and energy production under conditions of climate change, land use changes and urbanization pressures and management needs emerge at a novel scale. We need to jointly address toxic pressure by complex mixtures of chemicals and multiple stressors from various sources across compartmental and regulatory borders and enable their prediction, monitoring, assessment and abatement. Accounting for associations and nexus between SDGs is a major challenge for which scientific as well as practical solutions are sought that circumvents undue trade-offs between SDGs. The water quality-related projects GlobAqua, MARS and SOLUTIONS may serve as examples for the performance of collaborative projects in supporting a rational European policy on sustainability, environmental protection, and for safeguarding of ecosystem services for “living well, within the limits of our planet” .