Storjuktan – Rekonstruktion av ett sekels kvicksilverbelastning. : En undersökning av kvicksilverkoncentrationer i daterat bottensediment.

Sammanfattning: The aim of this study was to examine the current and historic mercury(Hg) load of the lake Storjuktan due to its recent exposure to a local potential source of Hg in form of the Sulphide mine Blaikengruvan(2006) and an earlier potential sources of Hg-load, the damming of the lake(1960s). Sediments were extracted using a HTH-sampler, freeze-dried, and analyzed for tot-Hg, LOI and activity of 210Pb and compared to samples extracted prior to the opening of the mine(2006). Constant initial concentration (CIC)-dating model was used for dating the samples. Low levels of Hg (100ng/g) were found throughout the lakes sediment. The highest levels of Hg(220ng/g) was detected at a depth of 4-5cm dating back to the mid 1970:s, suggesting that increased levels of atmospheric Hg rather than damming of the lake has caused the increase of Hg. No strong evidence for a release of Hg from the local mine was found. However an unexpected layer of anthropogenic sediment with low Hg-levels was found in close proximity to the metal enrichment plant, further supporting that the mine constituted a weak source of Hg. However, the anthropogenic sediment itself covered a large area (ca 22 ha) and its chemical composition calls for further investigation of its extent, properties and ecological impact in Lake Storjuktan. Keywords: Mercury; Sediment; contamination; Damming; Sweden