title: Influence of catchment vegetation on mercury accumulation in lake sediments from a long-term perspective.
abstract: Organic matter (OM) cycling has a large impact on the cycling of mercury (Hg) in the environment. Hence, it is important to have a thorough understanding on how changes in, e.g., catchment vegetation - through its effect on OM cycling - affect the behavior of Hg. To test whether shifts in vegetation had an effect on Hg-transport to lakes we investigated a sediment record from Herrenwieser See (Southern Germany). This lake has a well-defined Holocene vegetation history: at ~8700years BP Corylus avellana (hazel) was replaced by Quercus robur (oak), which was replaced by Abies alba (fir) and Fagus sylvatica (beech) ~5700years BP). We were particularly interested in testing if coniferous vegetation leads to a larger export of Hg to aquatic systems than deciduous vegetation. When hazel was replaced by oak, reduced soil erosion and increased transport of DOM-bound mercury from the catchment resulted in increases in both Hg-concentrations and accumulation rates (61ngg(-1) and 5.5ngcm(-2)yr.(-)(1) to 118ngg(-1) and 8.5ngcm(-2)yr.(-)(1)). However, even if Hg-concentrations increased also in association with the introduction of fir and beech (173ngg(-1)), as a result of higher Hg:C, there was no increase in Hg-accumulation rates (7.6ngcm(-2)yr.(-)(1)), because of a decreased input of OM. At around 2500years BP Hg-accumulation rates and Hg-concentration indicated an additional input of Hg to the sediment (316ngg(-1) and 10.3ngcm(-2)yr.(-)(1)), which might be due to increased human activities in the area, e.g., forest burning or mining. Our results contrast those of several paired-catchment studies that suggest a higher release of Hg from coniferous than deciduous forest, and there is a need for studies with a long-term perspective to increase our understanding of the effects of slow and gradual processes on mercury cycling.
authors.affiliation: Institut für Geoökologie, AG Umweltgeochemie, Technische Universität Braunschweig, Germany. Electronic address: johan.rydberg@emg.umu.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Rydberg
authors.affiliation: Labor für Archäobotanik, Landesamt für Denkmalpflege im RP Stuttgart, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Rösch
authors.affiliation: Institut für Geoökologie, AG Umweltgeochemie, Technische Universität Braunschweig, Germany; Landschaftsökologie und Ressourcenmanagement, Universität Giessen, Germany.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Heinz
authors.affiliation: Institut für Geoökologie, AG Umweltgeochemie, Technische Universität Braunschweig, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Biester
mesh_terms: D001673:Biodegradation, Environmental; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D005858:Germany; D060106:Lakes / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D010944:Plants; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Environmental archives; Holocene; Landscape development; Terrestrial–aquatic links