Influence of Suspended Particulate Matter on the Distribution and Transport of Metal and Organic Pollutants in the Elbe estuary

Legacy pollutants in aquatic sediments pose risks to valuable habitats, especially in estuaries of historically industrialized rivers like the Elbe. The fate of these particles is closely tied to the dynamics of suspended particulate matter (SPM) and its interactions with organic matter. While experimental studies have demonstrated that metal and organic pollutant affinities vary across different SPM compounds, the translation of these findings into predictive mathematical transport models remains challenging. In tidally influenced transition waters such as the Elbe estuary, the composition of SPM is known to vary over both time and space, thereby limiting the understanding of the transport behavior of legacy pollutants.

This contribution presents the findings of a recent study [1] that investigated the long-term seasonal dynamics of heavy metals (Cd, Cu, Zn, Hg) and persistent organic pollutants (HCB, DD’x and PCB 180) in SPM, at two sites along the Elbe River, one tidal and one nontidal, using statistical modelling of monitoring data from 2007 to 2021. It further introduces an empirical partitioning approach based on Turner’s formulation [2], which estimates the aqueous–solid partitioning coefficient (K_d) of metals as a function of salinity, suspended solids, and an organic matter proxy. The underlying data for this approach were gathered in several field campaigns and laboratory experiments (2023–2025) within the interdisciplinary research project CTM-Elbe.

Statistical modelling of long-term data has revealed that suspended solid concentration (SSC) largely explains the variation in unfiltered metal concentrations in water, reflecting the combined effects of sediment resuspension and seasonal biomass cycles [1]. Both organic and inorganic fractions of SPM were identified as key drivers of Cd, Zn, Cu, and Hg distribution and transport. In contrast, the particle-bound content of organic pollutants was poorly explained by SSC or organic carbon, reflecting limitations of the particulate sampling method. These insights support the development of new hydrodynamic transport models that account for metal partitioning under estuarine conditions, thereby enhancing our understanding of legacy pollutant transport and fate. Such models are essential for improving future sediment management and risk assessment strategies for legacy pollution in complex estuarine systems such as the Elbe.

 

References

1. Ortiz Gutierrez, V.; Fricke, B.; Kelln, J.; Zimmermann, T.; Pröfrock, D. (2025): Seasonal influence of suspended particulate matter on metal and organic pollutant distribution under fluvial and tidal conditions in the Elbe River. Water Research 291. DOI: 10.1016/j.watres.2025.125177.

2. Turner, A. (1996): Trace-metal partitioning in estuaries: importance of salinity and particle concentration. Marine Chemistry 54 (1-2). DOI: 10.1016/0304-4203(96)00025-4.