title: Impacts of forest harvesting on mobilization of Hg and MeHg in drained peatland forests on black schist or felsic bedrock.
abstract: Forest harvesting, especially when intensified harvesting method as whole-tree harvesting with stump lifting (WTHs) are used, may increase mercury (Hg) and methylmercury (MeHg) leaching to recipient water courses. The effect can be enhanced if the underlying bedrock and overburden soil contain Hg. The impact of stem-only harvesting (SOH) and WTHs on the concentrations of Hg and MeHg as well as several other variables in the ditch water was studied using a paired catchment approach in eight drained peatland-dominated catchments in Finland (2008-2012). Four of the catchments were on felsic bedrock and four on black schist bedrock containing heavy metals. Although both Hg and MeHg concentrations increased after harvesting in all treated sites according to the randomized intervention analyses (RIAs), there was only a weak indication of a harvest-induced mobilization of Hg and MeHg into the ditches. Furthermore, no clear differences between WTHs and SOH were found, although MeHg showed a nearly significant difference (p = 0.06) between the harvesting regimes. However, there was a clear bedrock effect, since the MeHg concentrations in the ditch water were higher at catchments on black schist than at those on felsic bedrock. The pH, suspended solid matter (SSM), dissolved organic carbon (DOC), and iron (Fe) concentrations increased after harvest while the sulfate (SO4-S) concentration decreased. The highest abundances of sulfate-reducing bacteria (SRB) were found on the sites with high MeHg concentrations. The biggest changes in ditch water concentrations occurred first 2 years after harvesting.
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland. liisa.ukonmaanaho@luke.fi.
authors.forename: Liisa
authors.identifier: http://orcid.org/0000-0002-2268-6862
authors.initials: L
authors.lastname: Ukonmaanaho
authors.affiliation: Department of Forest Sciences, University of Helsinki, P.O. Box 27, Helsinki, FI-00014, Finland.
authors.forename: Mike
authors.initials: M
authors.lastname: Starr
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland.
authors.forename: Marjatta
authors.initials: M
authors.lastname: Kantola
authors.affiliation: Natural Resources Institute Finland, P.O. Box 68, Joensuu, FI-80101, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Laurén
authors.affiliation: Natural Resources Institute Finland, University of Oulu, P.O. Box 413, Oulu, FI-90014, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Piispanen
authors.affiliation: Valmet, Elektroniikkatie 9, Oulu, 90590, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Pietilä
authors.affiliation: Department of Chemistry, University of Oulu, P.O. Box 3000, Oulu, FI-90014, Finland.
authors.forename: Paavo
authors.initials: P
authors.lastname: Perämäki
authors.affiliation: Natural Resources Institute Finland, University of Oulu, P.O. Box 413, Oulu, FI-90014, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Merilä
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Fritze
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland.
authors.forename: Tero
authors.initials: T
authors.lastname: Tuomivirta
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Heikkinen
authors.affiliation: Geological Survey of Finland, P.O. Box 1237, Kuopio, FI-70211, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Mäkinen
authors.affiliation: Natural Resources Institute Finland, P.O. Box 18, Vantaa, FI-01301, Finland.
authors.forename: Tiina M
authors.initials: TM
authors.lastname: Nieminen
mesh_terms: D004784:Environmental Monitoring; D005387:Finland; D016468:Forestry / Q000379:methods* / Q000706:statistics & numerical data; D065928:Forests; D007501:Iron; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D012987:Soil / Q000737:chemistry; D014197:Trees; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D012987:Soil; D014874:Water Pollutants, Chemical; D007501:Iron; D008628:Mercury
keywords: Bedrock; Concentrations; DOC; Fe; Harvesting regime; SO4-S; SSM