Estuarine filter for trace metals and emerging contaminants: an example from Southampton Water, UK

Organic and inorganic contaminants have deleterious effects on organisms and ecosystems worldwide. Elevated trace metal concentrations are known to cause poisoning and diseases such as Minamata disease, persistent PAHs are found regularly both in industrial discharges and in human body fluids and trace amounts of exogenous hormones can have significant (population level) impacts on aquatic organisms and cause serious diseases, obesity, and infertility in humans. Through wastewater treatment plants, discharge and agriculture, these contaminants end up in aquatic systems and their associated bed sediments. For a range of contaminants, estuarine sediments have been shown to be effective “traps”, moderating contaminant input from rivers to coastal and marine ecosystems, depending on the physical and chemical properties of the sediments. Sediment composition, particle size, organic matter content as well as contaminant chemical structure and speciation play an important role in the interaction between contaminants and sediments. However, for many pollutants, such as hormones, the circumstances that influence these trapping processes are still unclear. Further research is needed to fully understand the behavior of these contaminants and to assess possibilities to reduce their input into the environment and into aquatic food systems.

Here, we examine the sedimentary trapping of a range of emerging and conventional contaminants in the intertidal sediments of Southampton Water, a major industrialized and urbanized estuarine system in the southern UK.

Sediment cores (dated with Pb-210 and Cs-137 dating) show historical trends in contamination related to waste discharges into the estuary (e.g., for Cu and Pb), while surface sediments indicate point source inputs of contaminants, resulting in sedimentary concentration of contaminants which significantly exceed local geological background concentrations (e.g., Hg, with concentrations up to 2.4 ppm). TOC, δ¹³C values and major elements indicate an association with the sediment grain size. Ongoing work is examining distribution, trapping and breakdown of hormones and PAHs in sediments, and the role of sediment composition in these processes, using a sample preparation method for the simultaneous analysis of PAHs and hormones in sediments via GC-MSMS.