Abstract
Geochemical analyses of varved lake sediment cores (Lake Montcortès, Pre-Pyrenees) enabled the reconstruction of mercury (Hg) and lead (Pb) atmospheric deposition over the past seven centuries in the Pyrenees (NE Spain). Accumulation Rates (AR) from the Middle Ages to the Industrial Period ranged from 2,500 to 26,130 μg m²·yr⁻¹ and 15–152 μg m²·yr⁻¹ for Pb and Hg respectively. Significant metal pollution began around CE 1550 during a period of increased exploitation of ore resources in Spain. Colder and more humid conditions in the Pyrenees during the Little Ice Age may also have favoured Hg and Pb atmospheric deposition in the lake. Therefore, the interplay between increased rainfall (wet deposition) and mining activities on the Iberian Peninsula drove Hg and Pb AR during the Pre-industrial Period. More recently, the use of leaded petrol in Europe in the mid-20th century may explain the highest Pb AR between CE 1953 and 1971. The highest Hg AR occurred in CE 1940, synchronous with the peak Hg production in the Almadén mining district (southern Spain) and the Second World War. The record of Hg enrichment in Lake Montcortès shows a decrease during recent decades in Western Europe, similar to other regional records and global emission models. This study highlights the exceptional quality of varved sequences to disentangle pollutant depositional mechanisms, identify historical periods of increased atmospheric pollution, and provide a historical context for pollutant baseline values to enable accurate assessments of recent (atmospheric) pollution in lake ecosystems.
