Yin Runsheng, Feng Xinbin, Hurley James P, Krabbenhoft David P, Lepak Ryan F, Kang Shichang, Yang Handong, Li Xiangdong
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.
Sci Rep. 2016 Mar 21;6:23332. doi: 10.1038/srep23332.
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.
被称为“第三极”的青藏高原是大气汞(Hg)沉降的关键区域。全球范围内日益增加的人为活动导致环境变化,这可能会影响汞在环境中的负荷、传输和沉降。然而,青藏高原汞的沉降历史和地球化学循环仍不明确。我们对青藏高原最大的两个湖泊——青海湖和纳木错沉积物剖面中的汞及其同位素记录显示,自上世纪以来汞流入量增加,青海湖和纳木错的最大汞流入富集率分别为5.4和3.5。青海湖(-4.55‰至-3.15‰)和纳木错(-5.04‰至-2.16‰)中负δ(202)Hg的变化表明,通过降雨、植被和土壤径流的大气汞沉降增加。观测到偶汞(∆(200)Hg:+0.05‰至+0.10‰)和奇汞(∆(199)Hg:+0.12‰至+0.31‰)同位素的质量无关分馏。正Δ(200)Hg表明青藏高原降水来源的汞比例较高,而正Δ(199)Hg是由Hg(II)光还原产生的。自20世纪以来,两个湖泊的Δ(199)Hg均呈上升趋势,我们得出结论,随着冰期的缩短,这些青藏高原湖泊中Hg(II)的光还原可能加速。