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Assessing the stability of mercury and methylmercury in a varved lake sediment deposit
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
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2008 (English)In: Environmental Science & Technology, ISSN 0013-936X, Vol. 42, no 12, 4391-4396 p.Article in journal (Refereed) Published
Abstract [en]

Using lake sediments to infer past total mercury and methylmercury loading to the environment requires that diagenetic processes within the sediment do not significantly affect the concentrations or net accumulation rates of the mercury species. Because carbon is lost during early sediment diagenesis, the close link between carbon and mercury raises the question of how reliable lake sediments are as archives of total mercury and methylmercury loading. In this study we used a series of freeze cores taken in a lake with varved (annually laminated) sediment to assess the stability of total mercury and methylmercury over time. By tracking material deposited in specific years in cores collected in different years, we found that despite a 20–25% loss of carbon in the first 10–15 years, there was no apparent loss of total mercury over time; hence, lake sediments can be considered as reliable archives. However, over the first 5–8 years after sedimentation, about 30–40% of the methylmercury was lost (a decrease of 0.025–0.030 μg MeHg m−2 yr−1), suggesting that sediment profiles showing increasing methylmercury concentrations toward the sediment surface are in large part an artifact of diagenetic processes (net demethylation), rather than a record of changes in methylmercury loading.

Place, publisher, year, edition, pages
American Chemical Society , 2008. Vol. 42, no 12, 4391-4396 p.
Identifiers
URN: urn:nbn:se:umu:diva-10271DOI: 10.1021/es7031955PubMedID: 18605560OAI: oai:DiVA.org:umu-10271DiVA: diva2:149942
Available from: 2008-08-06 Created: 2008-08-06 Last updated: 2013-01-17Bibliographically approved
In thesis
1. Studies of an elusive element: processes that influence the net retention of mercury in lake sediments and peatlands
Open this publication in new window or tab >>Studies of an elusive element: processes that influence the net retention of mercury in lake sediments and peatlands
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Because of its toxic nature mercury is a threat to both wildlife and human health, and thus, it is an element of concern in the environment. Currently much of the mercury emitted to the atmosphere is derived from anthropogenic sources – both direct emissions and re-emission of already deposited anthropogenic mercury. Following deposition mercury is affected by a long array of processes, and this thesis has focused on trying to increase our knowledge on the net retention of mercury in lake sediments and peatlands. This information is vital in order to understand how mercury behaves in the environment and where mercury is at risk of becoming a problem. Knowledge about the retention of mercury is also important when using lake sediments and peat records as environmental archives over past mercury deposition.

By using varved, annually laminated, sediments I have determined that lake sediments are reliable archives for inorganic mercury, but not for methylmercury. A study of the spatial distribution of mercury in a whole-lake basin shows that inorganic- and methylmercury are controlled by different sediment properties. Inorganic mercury is controlled by combination of fine-grained mineral matter and organic matter concentrations, whereas methylmercury is controlled by water depth and sulfur concentration. This study also shows that especially methylmercury have a very heterogeneous spatial distribution across the lake basin, something that might be of large importance when using lake sediments to calculate whole-lake burdens of mercury. In a study regarding the effects of vegetation on the net retention of mercury in a peatland I showed that there are considerable differences in both plant- and peat-mercury concentrations depending on vegetation type. This might have implications for the use of peat records as archives over atmospheric mercury deposition. Finally I have used a combination of a peat and a lake sediment record to study how past and recent climatic changes affects the stability of a peatland currently underlain by permafrost. Here we are able to show that destabilization of peatlands, as a result of permafrost melt, can cause a significant release of organically bound mercury from the mire to the surrounding aquatic environment. Considering the currently warming climate there is a risk of sub-arctic peatlands turning into mercury sources, which might be important to recognize when assessing current mercury pollution pathways.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2010. 20 p.
Keyword
Mercury, retention, lake sediments, peatlands, environmental archives, sedimentation, diagenesis, vegetation, permafrost
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-38424 (URN)978-91-7459-113-2 (ISBN)
Public defence
2011-01-14, KBC-huset, KB3A9 (lilla hörsalen), Umeå universitet, Umeå, 10:00 (English)
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Available from: 2010-12-21 Created: 2010-12-14 Last updated: 2010-12-21Bibliographically approved

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