Fröåtjärns föroreningshistoria
Utredning av hur metallbelastningen varierat över tid med hjälp av sediment som ett naturligt historiearkiv
The metal mining history goes thousands of years back. The downside of the mining industry is the large amount of tailings created during the mining operations. Drainage and leaching of heavy metals from these tailings may cause major environmental problems including acid mine drainage and leaching of heavy metals. This study examines a pond located near an old mining site, where part of the old mining facility has been recently (1990) restored. The objective was to assess eventual metal contamination from historical mining and the recently performed restoration using a sediment core as a natural archive of historical metal inputs to the pond. I found that the concentration of lead, copper, zinc and nickel were elevated in comparison to background levels in sediment. Elevated concentrations were found in the deep layer of the sediment core, 14-20 cm with an estimated age of ca 100 years. The highest concentrations were found near the surface (3-4 cm depth). Conclusion of the study was that the early mining operations has affected the ponds metal contamination history. The restoration of the mining site had weak impact on the pond, but may contribute to the high metal concentration in recent sediments.