Atmospheric and catchment mercury concentrations and fluxes in Fennoscandia

Sammanfattning

Measurements in Southern Fennoscandia show a weak declining trend in mercury deposition which can be attributed to reduction controls in EU countries. Deposition of mercury in Arctic areas is likely to be governed by the amount of mercury in background air and therefore largely dependent on mercury emissions from mercury sources in the northern hemisphere. As a consequence of reduced mercury from European sources concentrations of gaseous elemental mercury (Hg0) in Northern Europe is also to a much lar-ger degree than before governed by the background level of mercury. This is consistent with mercury being a global pollutant. Hence, further reduction in anthropogenic emissions of mercury will also require control measures on a global scale. The so called atmospheric mercury depletion events (AMDE's) are occurring during polar spring. During AMDE mercury is rapidly oxidised and deposited on snow and ice and thereby constituting a source of mercury to the vulnerable Arctic environment. However, a significant part of the freshly deposited mercury may be reduced to the elemental form and be re-emitted back to the atmosphere. How much of the deposited mercury that remains contra is re-emitted to the atmosphere is crucial for assessing the importance of AMDE in the Arctic environment. Mercury deposited to boreal forest areas tend to accumulate in forest soils. Part of the mercury is re-emitted back to the atmosphere as a course of reduction mechanisms in the soil. Forest fires also constitute a source of mercury. When the soil is heated a great part of the accumulated mercury is re-emitted as Hg0 and hence recycled back to the atmosphere. The re-emission fluxes from forest fires are small in comparison to anthropogenic mercury emissions from the Fennoscandian countries, but cannot be ignored in the global mercury cycle. Forest soils are an important sink for mercury deposited from the atmos-phere. This sink can be affected by perturbations which lead to a mobiliza-tion of the stored mercury. Forestry practices which cause changes in the soil water table and may damage soil structures can lead to increased leach-ing of MeHg and TotHg via both increased run off and (for MeHg) by creat-ing conditions suitable for methylation of mercury. Similar effects can be expected in areas where climate change results in large increases in precipi-tation amounts. The processes governing these changes in mobilization are to some extent unknown and general predictions of the magnitude of the changes are thus associated with a large degree of uncertainty

Medarbetare: John Munthe

Nyckelord: mercury concentrations, fluxes, Fennoscandia

Typ: Artikel

År: 2011

Rapportnummer: A1866

Författare: Ingvar Wängberg, Katrine Aspmo Pfaffhuber, Torunn Berg, Hannele Hakola, Katriina Kyllönen, John Munthe, Petri Porvari, Matti Verta

Publicerad i: 2010. Norden, TemaNord 2010:594. ISBN 978-92-893-2162-4