Better understanding of concentration dynamics of substances in surface water

Nine substance groups

Monitoring programmes measure many substances in different surface waters. Sometimes the concentration of a substance is high, then it is again low. This complicates the interpretation of the results and the subsequent packet of measures to be taken, when these are necessary.

In the ‘Environmental Forensics: pollution signatures’ project the correlations between substance concentrations were examined at sites in the Meuse and Rhine river basins.  A total of nine substance clusters were distinguished at several locations. Substances in these clusters show similarities in application and/or chemical properties. This concerns metals, salts, biphenyls, pharmaceuticals, contrast agents, (polycyclic) aromatic hydrocarbons, beta-blockers and antidiuretics.

Conditions and properties

Most of these clusters have a specific association with environmental factors, such as temperature, river water discharge volume, or the amount of organic matter in the water. Additionally, substances in a cluster show similar combinations of properties, such as degradability, volatility, mobility and water-solubility. These results make clear that concentrations of substances in surface water are, besides their direct emission, also to a significant degree determined by these factors.

Image 1. Clustering concentration pattern at Nieuwegein site, with several structural substance clusters which are also found at other sites.

Outliers

Besides substances that could be grouped into clusters, there were also ‘outliers’ with unique concentration patterns. Other substance clusters, like certain herbicides and petrochemicals, showed up incidentally and irregularly. There were also substance clusters that were only found at a few sites. The common denominator for these substances is more difficult to determine and requires further research.

Grip on substances

The observed patterns, trends and correlations with conditions and substance properties offer a basis for the formulation of hypotheses about the emission (patterns) and the development of models to predict substance concentrations. This would give the water sector a better grip on substances and lead to prospective measures to reduce or prevent emissions.

Read the scientific papers with the results of this research here.