A 120-YEAR RECORD OF WIDESPREAD CONTAMINATION FROM MINING OF THE IBERIAN PYRITE BELT

A metal-enriched seawater plume entering the western Mediterranean Sea through the Strait of Gibraltar originates 300 km to the west in the Rio Tinto estuary of southwestern Spain, Mining of Rio Tinto ore, one of the largest metal-rich sulfide deposits in the world, started well before Roman times, Contemporary Rio Tinto waters draining the region are highly acidic (pH 2.5) with dissolved cadmium, zinc, and copper co ncentrations 10(5)-10(6) times higher than in uncontaminated surface w ater of the Gulf of Cadiz, Two dated sediment cores from the Spanish c ontinental shelf show that metal inputs to the region increased with t he onset of intensive mining activities during the second half of the 19th century, Although the impact of mining may have decreased over th e past few decades, the Tinto river and estuary remain highly contamin ated.