Hazardous substances can remain in the environment for a very long time, and harm ecosystems and human health. Although monitoring indicates that the loads of some substances have been reduced in recent years, many problems still persist. The increasing number of these man-made substances present in the environment is a matter of concern, and calls for the application of the precautionary principle.
Hazardous substances (HS) pollution refers to contamination with harmful chemicals and substances of emerging concern that might be heavily toxic to or accumulative in living organism. They include both inorganic and organic micro-pollutants such as heavy metals, arsenic, cyanides, oil and its compounds, trihalomethanes, polycyclic aromatic hydrocarbons, per- and polyfluoroalkyl substances, surfactants, flame retardants, plasticizers, biphenyls, phenols, pesticides, haloalkanes, endocrine disruptors, pharmaceuticals, certain ingredients of personal care products, etc.
HS can pose a serious threat to the aquatic environment and humans. Some of them are persistent, slowly degradable and can accumulate in the ecosystem (soil, unsaturated zone, river and lake sediments or in biota like fish or mussels). Depending on their concentration and the actual environmental conditions, they can cause acute (immediate) or chronic (latent) toxicity. They can deteriorate habitats and biodiversity and also endanger human health via drinking water or fish consumption as many of these chemicals are carcinogenic, mutagenic, interfere with the endocrine system or reproduction, or teratogen. They usually affect one or more of the vital systems of the living organism, like nervous, enzymatic, immune, reproductive, muscular systems or directly target the cells, exerting also genotoxic and mutagenic activities. They can alter proteins, impact cells, tissues and different organs, negatively influencing individual organisms or entire populations. As many pollutants tend to attach to organic matter, they may be taken up by the organisms during feeding and introduced in the food web through bioaccumulation and biomagnification processes. Moreover, some of the pollutants can attach to soil and sediment particles and can be subject to subsequent resuspension and dissolution. Therefore, HS pollution is considered as local/regional or even basin-wide water quality problem, which could even impact entire ecosystems.
Industrial emission inventory
The ICPDR complies and regularly updates an inventory for industrial and agricultural direct dischargers, based on the data published at the European Industrial Emissions Portal. The database contains information on the main industrial facilities and their pollution discharges above certain capacity and emission levels. The last inventory was compiled in 2021 for the reference year 2018. These inventories serve the pollution assessments of the Danube River Basin Management Plans elaborated by the ICPDR every six years.
Detecting chemical pollution of urban wastewater
In late summer 2017, samples from 12 urban wastewater treatment plants were collected and analysed by the SOLUTIONS Project in cooperation with the ICPDR for a wide range of hazardous substances including organic compounds and metals. The objectives of the monitoring exercise were to evaluate the occurrence of chemicals using the state-of-the art wide-scope chemical screening techniques, to quantify the effluent concentrations of the chemicals, to prioritize the detected substances based on ecotoxicological thresholds and to assess the acute adverse effects of mixtures of pollutants on different indicator species.
In the framework of the JDS4, daily composite wastewater influent and effluent samples from additional 11 treatment plants were collected and analysed for a target list of more than 2,400 chemicals and their transformation products. Prioritisation of these chemicals based on the NORMAN-methodology resulted in a preliminary list of wastewater-related river basin specific pollutants that are obviously originating from wastewater and exceeding ecotoxicology threshold values in the river water at the basin scale. These substances represent carefully selected compounds, which are released from treatment plants in high concentrations causing adverse effects to environment, always present and easy to analyse.
These investigations provided valuable information on the hazardous substance content of wastewater treatment plant effluents and oriented the scope of further activities to substances with high environmental risk.
Controlling hazardous substances emissions
The ICPDR actively contributed to and supported the implementation of the Danube Hazard m3c project, funded by the Danube Transnational Programme. The project aimed to achieve a durable and effective transnational control and reduction of hazardous substances water pollution. Danube Hazard m3c built on the three elements of water governance (measuring, modelling and management) complemented by capacity building.
- Collection of the pre-existing data on hazardous substances pollution across the Basin was carried out by exploiting national and international databases. In addition, targeted measuring campaigns were carried out in 7 different pilot catchments in 4 countries and for 17 preselected parameters – pesticides, pharmaceuticals, industrial chemicals, heavy metals, combustion products. All the collected data have been incorporated into an easy-to-use online database, which is accessible for everyone.
- A coupled water quality model system was developed and adapted to the conditions of the basin. First, a basin-wide source-oriented model was set up to simulate the spatial patterns of the target chemicals. Then, this model has been enhanced by upscaling the experiences of a pathway-oriented model that was tested in the pilot catchments. The obtained modeling results were used to assess the current chemical emissions in the basin and to propose recommendations for sustainable measure implementation based on scenario assessment.
- The legal framework of all the countries across the basin was analyzed and critically assessed to identify the need for harmonization of current policies. The findings served the elaboration of a policy paper that recommends sound policy instruments and effective measures for managing hazardous substances pollution. It offers Danube countries support for the preparation and implementation of tailor-made national water management policies.
- Capacity building was a key feature of the project. Technical aspects of monitoring and modeling were discussed with relevant experts at 7 national and 4 international training events. More than 400 participants from different water related working fields were acquainted with good practices on monitoring, laboratory testing and applying simulation models. In addition, a technical manual has been developed to provide guidance on monitoring ad modelling of hazardous substances pollution for practitioners.
The interim modelling results and the policy paper provided inputs to the Danube River Basin Management Plan Update 2021.