Biomonitoring toxic and essential element accumulation in trout in the As Pontes mine pit lake (NW Spain)

Abstract

This study investigated the accumulation of toxic and essential elements in trout from a pit lake situated in the surroundings of the abandoned As Pontes de García Rodríguez lignite mine (NW Spain). The element concentrations were compared with those measured in fish from upstream of the River Eume and from a local fish farm. Liver and muscle samples from fish captured in the lake (n = 16), river (n = 14) and fish farm (n = 10) captured in March–April 2022 were acid digested and analyzed by ICP-MS. The mining activity in As Pontes was found to have significantly impacted the aquatic ecosystem. Concentrations of Cd, Ni, Co, and Cu in the livers of the lake fish were significantly higher than in the livers of the other groups of fish, probably due to run-off from the spoil heap reaching the lake. Similarly, higher concentrations of Al, Pb, and Hg were observed in the river trout, associated with coal combustion at a near thermal power plant. Despite these variations, toxic and essential elements in both the pit lake and river remained low, within water quality standards, and do not pose an immediate threat to aquatic life. Concentrations of the metals in the muscle of wild fish, although higher than in farmed fish, were within EU limits. The study findings highlight the value of fish as indicators of environmental exposure and emphasize the ongoing need to monitor the pit lake to assess the long-term impacts of mining activities on aquatic health. Examination of liver tissue proved to be particularly useful in the assessments, providing a precise reflection of metal exposure and serving as a valuable means of evaluating environmental contamination and ecosystem health.