En geokemisk kartering över området kring Nasa silvergruva : Effekterna av historisk gruvdrift i svensk fjällmiljö

• Main Author: Fahlman, Johan
• Format: Bachelor Thesis
• Language: Swedish
• Published: Institutionen för ekologi, miljö och geovetenskap 2012
• Subjects: Acid mine drainage; Geochemistry; Historical mining; Nasafjäll; Swedish mountains; Geokemi; Arctic; Kring; Nasa Silvergruva
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-61635

The aim of the study was to map the extent of Fe, Cu, Pb, As, Zn and S contamination in the area surrounding the Nasa silver mine. The mine operated between 1635 and 1810 with some prospecting performed in 1889, and has become infamous for the gruesome ways that the indigenous people were treated during the early years of operation. This study tested three hypotheses through a geochemical survey: 1) sulfide oxidation is still active in the abandoned mine, 2) the soil downslope of the mine is contaminated by mine drainage, and 3) the stream downslope of the mine is affected in the same way. All three hypotheses were valid, as the results showed that still, >200 years after mining operations ceased, signs of the historical mining are clearly visible in the surrounding environment. Acidic conditions were discovered in surface waters close to the waste rock piles, which indicates active sulfide oxidation. In addition, elevated levels of Fe, Cu, Pb, As, Zn and S were found in both soil and stream sediment downslope of the mines, as compared to reference localities upstream the mine (p <0.05). These results suggest that previous assessments of the mine being no threat to the environment may not be entirely correct. This study illustrates how mining waste can continue to affect the local, sub-arctic environment long after mining operations have ceased.