Investigating the impact of a decommissioned uranium mine on the fluvial sediment of the River Fal, Cornwall

Development of remediation strategies is required to assist in the restoration of polluted river systems to meet a ‘good ecological status’ as part of the European Water Framework Directive’s objectives. This study investigates whether the source of heavy metal contaminants within the River Fal is directly caused by diffuse pollution from the decommissioned South Terras uranium mine, Cornwall. A longitudinal study from above the South Terras mine continuing downstream to the Fal Estuary firstly investigates patterns of metal contamination and transportation, specifically focusing on uranium and its decay products. The use of XRF (X-ray Fluorescence Analysis) and Gamma Spectrometry analysed spatial trends of contaminated river sediments as well as potential sources of the river sediment including sediment from the mine itself, the catchment surrounding the mine and the river bank. These results (after statistical analysis) were utilised to produce a sediment fingerprint of which a mixing module determined source proportions within the river sediment at each sample site. The finding confirmed that heavy metals, uranium and its decay products are only elevated within river sediments adjacent to the mine. Results show that the primary source of sediment is provided from the catchment area followed closely by the river bank. It can be concluded that South Terras mine is not secreting significant concentrations of radioactive material into the river Fal and is not the direct source of any detected radioactive elements. The heavy metal concentrations detected are not substantial enough to impact the WFD status of the river however management initiatives are suggested to ensure the contaminant concentrations do not increase