Total mercury and methylmercury in runoff water after wetland restoration and ditch cleaning

Last changed: 07 November 2023

Trollberget ditch clearningThis project evaluates how wetland restoration and ditch cleaning effect total Hg (THg) and methylmercury (MeHg) concentrations in runoff waters. Forest soils have retained high loads of Hg originating from long-range transboundary air pollution and historic point sources. The mobilization of legacy Hg can increase rapidly if conditions change, e.g. by forestry operations such as ditch cleaning or by flooding of forest soils. Flooding of soils may also increase the formation of the toxic and bioavailable MeHg by anaerobic microorganisms. Ditch cleaning, on the other hand, may lower the ground water levels, but may instead increase Hg co-transported with sediments released during ditch cleaning activities. The study involved monitoring of THg and MeHg in ditch water from the restored wetlands and ditch cleaned catchments, before and after forest harvest, ditch cleaning and wetland restoration in the Trollberget Experimental area and close-by reference catchments.

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