title: Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes.
abstract: The Tibetan Plateau (TP), known as the "Third Pole", is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ (202)Hg in Lake Qinghai (-4.55 to -3.15‰) and Nam Co (-5.04 to -2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ (200)Hg: +0.05 to +0.10‰) and odd-Hg (∆ (199)Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ (200)Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ (199)Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ (199)Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes.
authors.affiliation: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.|Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Runsheng
authors.initials: R
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
authors.forename: Xinbin
authors.initials: X
authors.lastname: Feng
authors.affiliation: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, 53706, USA.|Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.|University of Wisconsin Aquatic Sciences Center, Madison, WI, 53706, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Hurley
authors.affiliation: U.S. Geological Survey, Mercury Research Laboratory, Middleton, WI, 53562, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Krabbenhoft
authors.affiliation: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Lepak
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Shichang
authors.initials: S
authors.lastname: Kang
authors.affiliation: Environmental Change Research Centre, University College London, Pearson Building, Gower Street, London WC1E 6BT, UK.
authors.forename: Handong
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Li