Algal scavenging of mercury in preindustrial Arctic lakes
Algal scavenging of mercury in preindustrial Arctic lakes
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DOI：
10.1002/lno.11135
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发表时间：
2019-02
影响因子：
4.5
通讯作者：
P. Outridge;G. Stern;P. Hamilton;H. Sanei
中科院分区：
文献类型：
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作者：
P. Outridge;G. Stern;P. Hamilton;H. Sanei
研究了1800年前北极湖泊沉积物中总汞（THg）的地球化学形态，以提高对控制“自然基线”THg的因素的理解。通过连续提取来自不同生态区（贫瘠苔原、长满草的苔原和北方森林）三个湖泊的过时岩心，确定了THg的固相结合形式。沉积物有机质（OM）主要来源于藻类。汞高度集中在沉积物有机质组分（OM-Hg）中，占总汞的60-87%，而有机质（作为总有机碳）仅占沉积物干重（DW）的0.6-13%。藻类有机质中的有机质-汞浓度相当于159 ± 13至776 ± 215纳克Hg g−1干重，与沉积物总汞相比富集了2-39倍，表明即使藻类有机质输入的微小变化也会显著改变总汞。OM‐Hg解释了几个世纪以来THg浓度变化的76-96%。在两个湖泊中，S2碳（藻类生产力代理）和OM-Hg的浓度显著相关，但在北方森林湖中不相关，这可能是因为其深水柱中的OM矿化。在贫瘠的苔原湖中，S2碳、OM‐Hg和THg通量高度相关，但无法计算其他湖泊。总体结果表明，高浓度的藻类汞由于清除有效汞控制OM-汞通量沉积物，从而驱动THg浓度和通量的变化。这些发现提高了我们对北方湖泊在气候变化（包括现代）下基线THg长期稳定性的理解。
The geochemical speciation of total mercury (THg) was examined in pre‐1800 Arctic lake sediments to improve understanding of the factors controlling “natural baseline” THg. Solid‐phase binding forms of THg were determined by sequential extraction of dated cores from three lakes in different ecozones (barren tundra, grassy tundra, and boreal forest). Sediment organic matter (OM) was mostly of algal origin. Mercury was highly concentrated in the sediment OM fraction (OM‐Hg), comprising 60–87% of THg, while OM (as total organic carbon) constituted only 0.6–13% of sediment dry weight (DW). OM‐Hg concentrations were equivalent to 159 ± 13 to 776 ± 215 ng Hg g−1 DW in algal OM and were enriched 2–39 times compared to sediment THg, indicating that even small changes in algal OM inputs could significantly alter THg. OM‐Hg explained 76–96% of the variation in THg concentrations over many centuries. Concentrations of S2 carbon (an algal productivity proxy) and OM‐Hg were significantly correlated in two lakes but not in the boreal forest lake possibly because of OM remineralization in its deep water column. Fluxes of S2 carbon, OM‐Hg, and THg were highly correlated in the barren tundra lake but could not be calculated for the other lakes. The results overall indicate that high algal Hg concentrations due to scavenging of available Hg controlled OM‐Hg flux to sediments, thus driving changes in THg concentrations and fluxes. These findings improve our understanding of the long‐term stability of baseline THg in northern lakes under a changing climate, including in the modern era.