Atmospheric and catchment mercury concentrations and fluxes in Fennoscandia

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 entire northern hemisphere. Hence, further reduction in anthropogenic emissions of mercury will require control measures in the entire northern hemisphere. The so called atmospheric mercury depletion events (AMDEs) are occurring during polar spring. How much of the deposited mercury that remains contra is re-emitted to the atmosphere is, however, crucial for assessing the importance of AMDE in the Arctic environment. Forest soils are an important sink for mercury deposited from the atmosphere. However, this sink can be affected by perturbations in conjunction to common forestry practices and lead to mobilization of the stored mercury and enhanced methyl mercury formation. Similar effects can be expected in areas where climate change results in large increases in precipitation amounts. The processes governing these changes in mercury mobilization are to some extent unknown and general predictions of the magnitude of the changes are thus associated with a large degree of uncertainty

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