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Climate, Fire, and Vegetation Mediate Mercury Delivery to Midlatitude Lakes over the Holocene
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2018-07-10 , DOI: 10.1021/acs.est.8b01523
David P. Pompeani 1, 2 , Colin A. Cooke 3, 4 , Mark B. Abbott 2 , Paul E. Drevnick 5
Affiliation  

The rise in mercury concentrations in lake sediment deposited over the last ∼150 years is widely recognized to have resulted from human activity. However, few studies in the Great Lakes region have used lake sediment to reconstruct atmospheric mercury deposition on millennial time scales. Here we present a 9000-year mercury record from sediment in Copper Falls; a small closed-basin lake on the Keweenaw Peninsula. Prior to abrupt increases in the 19th and 20th centuries, mercury remains at relatively low concentrations for the last 9000 years. Higher mercury fluxes in the early Holocene (3.4 ± 1.1 μg m–2 yr–1) are attributed to drier conditions and greater forest fire occurrence. The gradual decline in mercury flux over the middle to late Holocene (1.9 ± 0.2 μg m–2 yr–1) is interpreted to reflect a transition to wetter conditions, which reduced forest fires, and promoted the development of soil organic matter and deciduous forests that sequestered natural sources of mercury. The Copper Falls Lake record highlights the sensitivity of watersheds to changes in mercury inputs from both human and natural forcings, and provides millennial-scale context for recent mercury contamination that will aid in establishing baseline values for restoration efforts.

中文翻译:

气候,火灾和植被介导了全新世期间汞向中纬度湖泊的输送

在过去约150年中,沉积的湖泊沉积物中汞浓度的上升被广泛认为是人类活动造成的。但是,在大湖地区,很少有研究使用湖泊沉积物在千年尺度上重建大气中的汞沉积。在这里,我们展示了铜瀑布中沉积物产生的9000年汞记录;Keweenaw半岛上的一个封闭的小流域湖。此前在19突然增加和20世纪以来,汞保持在相对低的浓度在过去9000年。全新世早期的汞通量更高(3.4±1.1μgm –2 yr –1)归因于更干旱的条件和更大的森林火灾发生。全新世中期至晚期(1.9±0.2μgm –2 yr –1)中汞通量的逐渐下降被认为反映了向湿润条件的过渡,这减少了森林火灾,并促进了土壤有机质和落叶林的发展隔离了汞的天然来源。铜瀑布湖的记录突出了流域对人为和自然强迫产生的汞输入变化的敏感性,并为近期的汞污染提供了千年规模的背景信息,这将有助于确定恢复工作的基准值。
更新日期:2018-07-12
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