Löslighet och metylering av kvicksilver i en förorenad sjö (Ala-Lombolo) i Kiruna kommun
Transformation of inorganic mercury (Hg) to methyl mercury (MeHg) is a biotic process that is proposed to be conducted primarily by sulphate reducing bacteria (SRB). The formation of MeHg is of great interest because it is the mercury species that biomagnifies to the greatest extent in the aquatic f...
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| Format: | Other/Unknown Material |
| Language: | Swedish English |
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SLU/Dept. of Forest Ecology and Management
2007
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| Online Access: | https://stud.epsilon.slu.se/12016/ |
| Summary: | Transformation of inorganic mercury (Hg) to methyl mercury (MeHg) is a biotic process that is proposed to be conducted primarily by sulphate reducing bacteria (SRB). The formation of MeHg is of great interest because it is the mercury species that biomagnifies to the greatest extent in the aquatic food webs; about 90 % of all Hg in fish is MeHg. Our understanding of factors involved in the production of MeHg is very important for making a reliable risk assessment. The purposes of this study were to investigate the different factors that control the solubility of Hg and the production of MeHg in a contaminated lake sediment. The lake Ala-Lombolo, Kiruna municipality, is well-known to be contaminated by mercury from different sources. Sediment cores were sampled at three different locations (N, SW and SE) in the lake and divided in three different layers; 0-5, 5-10 and 10-15 cm. To minimize the contact with air, 1 litre plastic buckets were completely filled with sediment as fast as possible and then sealed and put in a cooling bag during the 8 hour transport to Umeå. In the laboratory, samples where homogenized in a N2-filled glove-box and divided into sub-samples for determination of total concentrations of Hg-tot, MeHg, C, N, S and Fe in the sediment and Hg, MeHg, organic and inorganic carbon, pH, dissolved H2S, Cl and SO4 in the pore water. The potential methylation/demethylation rates where determined in sediment sub-samples after incubation 48 hours at 23 ˚C. The lake is highly contaminated with a total Hg concentration varying between 20 and 60 mg kg-1 in the solid phase and between 0,05 and 0,77 nM in the pore water. For MeHg the concentration ranges from 6,6 to 29,2 µg kg-1 in the solid phase and from 0,00019 to 0,0014 nM in the pore water. The depth distribution of MeHg differs from Hg, with the highest concentration of MeHg in the top sediment layer (0-5 cm). The likely reason for that is a sedimentation of energy rich organic matter from dead algae, which is stimulating sulphate reducing bacteria, at ... |
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