Lead pollution
Mining and smelting have been a source of lead atmospheric pollution since ancient times. Atmospheric lead may travel long distances before it is deposited on remote ecosystems like alpine lakes. A sediment core retrieved in Lake Redon revealed that lead pollution started here already 2,700 years ago, and peaked in the VII century. Further studies have shown a widespread contamination in sediments from lakes accross the Pyrenees. And moreover, there is a lead legacy stored for centuries in soils that is been leached nowadays causing a delayed pollution to lakes.