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. 2016 Mar 21:6:23332.
doi: 10.1038/srep23332.

Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes

Runsheng Yin  1   2 , Xinbin Feng  1 , James P Hurley  2   3   4 , David P Krabbenhoft  5 , Ryan F Lepak  2 , Shichang Kang  6   7 , Handong Yang  8 , Xiangdong Li  9
Affiliations

Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes

Runsheng Yin et al. Sci Rep. .

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.

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Figures

Figure 1
Figure 1. Study area and sampling sites.
(This image is modified by R-S Yin, on basis of the a Wikimedia Commons map: https://commons.wikimedia.org/wiki/File:Topografic_map_of_Tibetan_Plateau.png#filelinks).
Figure 2
Figure 2
Sediment profiles of THg (A), Hg influx (B), Hg influx ratio (C), global average temperature anomaly ((D) according to Hansen et al.30) and temperature in TP ((E), according to Zhang et al.13), TOC ((F) according to Lami et al. and Li et al.22), δ 202Hg (G), ∆ 200Hg (H), ∆ 199Hg (I) and ice duration ((J) according to Che et al. and Ke et al.21) in Lake Qinghai and Nam Co.
Figure 3
Figure 3. Correlations between THg and TOC in sediments of Lake Qinghai and Nam Co.
Figure 4
Figure 4
Relations of δ 202Hg to THg (A) and TOC (B) in sediments of Lake Qinghai and Nam Co.
Figure 5
Figure 5. Relations between ∆ 199Hg and ∆ 201Hg in sediments of Lake Qinghai and Nam Co.
Figure 6
Figure 6
Relations of ∆ 199Hg to δ 202Hg(A), THg (B) and TOC (C) in sediments of Lake Qinghai and Nam Co.
See this image and copyright information in PMC

References

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