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The Plymouth Student Scientist

Bjorn Piñol

Document Type

Geography, Earth and Environmental Sciences Article

Abstract

Freshwater quality is critical to the health of aquatic ecosystems and human water security, yet anthropogenic activities, such as historic mining, continue to degrade aquatic systems. While extensive research has examined metal contamination in major rivers like the River Tamar, smaller tributaries affected by legacy mining remain understudied. This study investigates trace metal contamination and its controlling factors in the River Seaton, Cornwall, a small river influenced by historic mining from the South Caradon Mine. Water samples collected from four study sites along the river gradient and a reference site at Siblyback Lake were subjected to ICP-MS analysis and physico-chemical characterisation to identify potential correlations between trace metal(loids) concentrations (Metals: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Cd, Tl, Pb and Zn; Metalloids: Ge, As, Se, Sb) and environmental factors such as pH, redox potential, temperature, and Dissolved Oxygen (DO). These samples were quantified and analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Physico-chemical factors were taken in situ in the River Seaton, Cornwall, and ecological risk was calculated using the Potential Ecological Risk Index (PERI). Pearson's Correlation Coefficient analysis identified pH and redox potential as the dominant geochemical controls on trace metal speciation and mobility.

Results revealed severely elevated metal concentrations, particularly at site two directly below the South Caradon Mine, which alone accounted for 87% of the cumulative PERI score across all four study sites. Copper (Cu) had the highest average concentration across all sites, at 177 µg/L in site 2, with metal concentrations decreasing substantially toward the river mouth (site 5) due to spatial and temporal distribution patterns driven by river flow. Zinc (Zn) was exceedingly significant in all sites, with a concentration of 400 µg/L at site 3. Both Cu and Zn exceed the Environmental Quality Standard (EQS) and the Dutch Maximum Permissible Concentration (MPC), with an average PERI score of 491, indicating "high" ecological risk across the study sites. Although not surpassing the EQS, high concentrations of Arsenic (As) (12.3 µg/L) under the formation of arsenite (As(III)) and arsenate (As(V)) were sampled in site 2. The presence of As confirms the release of AMD into the river, resulting from the oxidative dissolution of arsenic-bearing sulphide minerals in the catchment's historic mining areas. These findings indicate a significant anthropogenic imprint on the River Seaton, confirming that legacy mining activities continue to influence water chemistry, degrade ecological status, and pose risks to downstream aquatic systems. This was confirmed by comparing the River Seaton water samples with those from the reference site in Siblyback Lake. These findings provide crucial baseline data for the River Seaton; however, further investigation incorporating temporal variability and biological assessments will be necessary to comprehensively classify the river health index.

Publication Date

2025-12

Volume

18

Issue

2

ISSN

1754-2383

Deposit Date

2025-12

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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Bjorn Piñol - supplementary file.docx (6764 kB)
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