Aberystwyth University scientists have warned that large quantities of contaminated sediment from floodplain soils and old workings is being remobilized by flooding in areas where metal mining took place.
A paper in Science of The Total Environment warns the pollution poses a significant threat to agricultural production and is preventing many European rivers achieving good chemical and ecological status under the water framework directive.
Analysis of overbank sediment following widespread flooding in west Wales in June 2012 showed flood sediment contamination above guideline thresholds, in some samples by a factor of 82.
Most significantly, silage produced from flood-affected fields contained up to 1,900mg kg− 1 of sediment-associated lead, which caused cattle poisoning and mortality.
With climate change increasing flooding, the researchers say the problem is set to intensify.
Management of contaminated catchments will require a geomorphological approach to understand spatial and temporal cycling of metals through the fluvial system.
Paul Brewer of the University told The Independent newspaper the lead-laden flood waters were responsible for the deaths of two calves in 2012 after they consumed contaminated silage.
The newspaper speculated recent floods may be causing a wildlife disaster.