title: Winter peaks of methylmercury in deposition to a remote Scottish mountain lake.
abstract: Depositional records of methylmercury (MeHg) are rare, especially for remote and mountainous areas. Our data from Lochnagar, a mountain lake in Scotland, covering a 7-year period from 2001-2008, show an unusual seasonal pattern in that elevated MeHg concentrations occur each winter while concentrations each summer fall below the limit of detection. To our knowledge this is the first time this seasonal pattern has been reported. Peak concentrations at the site in October 2006 (1.2 ng L(-1)) are amongst the highest reported depositional values in the literature. As the soils and lakes in the region are frozen or snow covered for much of each winter, we consider possible sources of this winter deposited MeHg to be either aqueous phase methylation in the atmosphere or marine evasion. However, the factor driving this seasonal pattern is likely to be scavenging by snow, as elevated concentrations in deposition coincide with periods of snowfall at the site. If this mechanism is correct, then predicted impacts of climate change, which will reduce annual snowfall at the site by between 50% and 100% by 2080, will effectively eliminate this input source. However, other climate-influenced inputs of mercury, such as remobilisation from catchment soils, are likely to increase and negate any benefit.
authors.affiliation: Environmental Change Research Centre, University College London, Gower Street, London WC1E 6BT, UK. n.rose@ucl.ac.uk
authors.forename: Neil L
authors.initials: NL
authors.lastname: Rose
authors.forename: John
authors.initials: J
authors.lastname: Munthe
authors.forename: Alistair
authors.initials: A
authors.lastname: McCartney
mesh_terms: D000397:Air Pollution / Q000032:analysis / Q000706:statistics & numerical data; D001272:Atmosphere / Q000737:chemistry; D057231:Climate Change; D004784:Environmental Monitoring; D060106:Lakes / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000032:analysis*; D012606:Scotland; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical