Quantifying excess heavy metal concentrations in drainage basins using conservative mixing modelling

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Authors

Jonas Alexander Eschenfelder , Alex G. Lipp, Gareth G Roberts

Abstract

High concentrations of heavy metals and other pollutants in river sediments can have detrimental effects on the health of ecosystems and humans.
As such, determining the composition of river sediments throughout drainage basins is an essential aspect of environmental monitoring.
Well characterised natural baseline concentrations are important information with which observations can be compared to identify potentially harmful pollutants. In this study, forward and inverse mixing models are used to map natural baselines and elemental concentrations in river sediments in the upper reaches of the Clyde drainage basin, UK. Continuous baselines are generated using forward mixing models parameterised with 1185 measurements of elemental concentrations from first-order streams. Calculated baselines are compared to concentrations measured at 60 localities along the main channel of the Clyde river. For a range of major and trace elements (e.g. Mg, Sr, K), the downstream observations are in close agreement with the baseline concentrations predicted from conservative mixing. However, some heavy metal concentrations (Pb, Cu, Zn) tend to exceed the predicted baseline concentrations. Assuming conservative mixing, the excess elemental masses required to match these observations are calculated by inverting (`unmixing'), the concentrations of downstream samples. We tentatively suggest that anthropogenic activity inserts 9.7 Mg/yr of Pb, 1.5 Mg/yr of Cu and 5.7 Mg/yr of Zn into the sediments of the river Clyde. Finally, a strategy for mapping toxic elemental concentrations along rivers and limitations on model resolution imposed by the spatial distribution of the data are discussed.

DOI

https://doi.org/10.31223/X5993F

Subjects

Earth Sciences, Environmental Sciences, Geochemistry, Geomorphology, Physical Sciences and Mathematics, Sustainability, Water Resource Management

Keywords

River pollution \and Clyde, Scotland \and Geochemical modelling \and Heavy metalMixing, River Pollution, Clyde Scotland, Geochemical Modelling, Heavy metal, mixing

Dates

Published: 2022-05-13 20:24

Last Updated: 2022-05-19 18:03

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
The data used was provided under licensce but can be requested from the BGS

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