Mercury is an element with a complex biogeochemical cycle in air, soils, water, and biota; mercury originates from both natural and anthropogenic sources. Although mercury is a naturally occurring element, human activities have increased levels in the environment by about a factor of three globally (1). Humans are exposed to mercury through industry, artisanal gold mining, dental amalgam, and fish consumption. The main concern of mercury in the environment is associated with elevated concentrations of methylmercury in fish because methylmercury bio-accumulates in freshwater fish at concentrations that may be harmful to human health. The main health concern refers to neurological damage, and unborn fetuses are especially sensitive to low doses of methylmercury. In boreal regions, mercury in the environment is to a large extent accumulated in soils and sediments with only small fractions available for uptake in aquatic food chains. A large fraction of this mercury is of natural origin. However, external factors such as forestry operations (2, 3) and storm events can affect the environmental biogeochemistry of mercury and increase the risks of bioaccumulation in aquatic ecosystems. In addition to direct atmospheric deposition, mercury leaching from forest soil is the most important source of mercury in surface waters, and external factors affecting the forestry system may therefore result in a significant increase in the load of mercury on streams and lakes. This study focuses on two examples where an increased mobilization of mercury and methylmercury from forest soils to aquatic ecosystems has been observed: forestry operations and storm-felling.
Nyckelord: Mercury, Methylmercury, Forest Soils, Storm-fell event
Författare: John Munthe, Sofie Hellsten, Therese Zetterberg
Publicerad i: Ambio, 2007. Volume 36, pp. 1:111-113