Atmospheric and catchment mercury concentrations and fluxes in Fennoscandia

image of 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




Yearly average TGM concentrations from five Northern European sites and from Ny-Ålesund are shown in Figure 2. The data covers the period 1995 to 2006 and shows that all values with few exceptions are confined into the relatively narrow range of 1.4-1.9 ng m-3. The background concentration of TGM in the Northern Hemisphere was estimated to be around 1.7 ng m-3 during the period 1996-2000 with somewhat higher values over the Northern Atlantic Ocean (Slemr et al., 2003). Hence, this indicates that the present TGM values to a large degree reflect the northern hemispheric background concentration of mercury. Earlier TGM was much higher in for example southern Sweden due to the proximity to European mercury sources (Iverfeldt et al., 1995; Wängberg et al., 2007). The highest values are observed at Mace Head and at Lista/Birkenes and during later years also at Råö. Whereas TGM values appears to be slightly lower at especially Pallas and NyÅlesund. The reason for this difference is not clear, but the same pattern has been observed earlier and attributed to re-emission from the Atlantic Ocean (Kock et al., 2005).


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