Environmental effects of one thousand years of copper production at Falun, central Sweden.

Copper production in Falun, central Sweden, has emitted sulfur dioxide (SO2) and metals to the air during at least 1000 years. Emissions peaked in the 17th century when Falun produced 2/3 of the world's copper supply. This area offers unique opportunities to study long-term effects of acid deposition and metal pollution, including recovery following the three centuries of decreasing SO2 and metal deposition. Here we present a 1000-yr perspective on local emissions of SO2, estimated air concentrations and dry deposition of SO2, as well as results on acidification and metal pollution of soils and lakes. Despite a long period when deposition of SO2 exceeded the critical load, soil acidification is limited to the most heavily polluted area 12 km NW and SE from the mine. According to diatom analyses of take sediments, only 8 of 14 lakes have become acidified (0.4-0.8 pH units). None of these lakes show recovery from acidification, probably due to large amounts of sulfate still accumulated in the soils and changes in land use.