Sediment Evidence of Early Eutrophication and Heavy Metal Pollution of Lake Mälaren, Central Sweden

• Published in: Ambio Vol. 30; no. 8; pp. 496 - 502
• Main Authors: Renberg, Ingemar, Bindler, Richard, Bradshaw, Emily, Emteryd, Ove, McGowan, Suzanne
• Format: Journal Article
• Language: English
• Published: Sweden Royal Swedish Academy of Sciences 01-12-2001
• Subjects: Diatoms; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Eutrophication; Fresh Water - chemistry; Geologic Sediments - analysis; History, 20th Century; History, Ancient; History, Medieval; Humans; Lakes; Lead; Lead - analysis; Lead industry; Lead isotopes; Metallurgy; Metals, Heavy - analysis; Paleontology - methods; Pigments; Sediment contamination; Sediments; Sweden; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - history; Water pollution; Water Pollution - history; Watersheds; Sweden
• ISSN: 0044-7447; 1654-7209
• DOI: 10.1579/0044-7447-30.8.496

Lake Mälaren is the water supply and recreation area for more than 1 million people in central Sweden and subject to considerable environmental concern. To establish background data for assessments of contemporary levels of trophy and heavy metal pollution, sediment cores from the lake were analyzed. Diatom–inferred lake–water phosphorus concentrations suggest that pre-20th century nutrient levels in Södra Björkfjärden, a basin in the eastern part of Mälaren, were higher (c. 10–20 µg TP L−1) than previously assumed (c. 6 µg TP L−1). Stable lead isotope and lead concentration analyses from 3 basins (S. Björkfjärden, Gisselfjärden and Asköfjärden) show that the lake was polluted in the 19th century and earlier from extensive metal production and processing in the catchment, particularly in the Bergslagen region. The lake has experienced a substantial improvement of the lead pollution situation in the 20th century following closure of the mining and metal industry. The lead pollution from the old mining industry was large compared to late-20th century pollution from car emissions, burning of fossil fuels and modern industries.