<br>环极深水上升流对南极洲周围上层海洋甲基汞的贡献增加：鸟类沉积物中汞同位素的证据,Environmental Science & Technology

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环极深水上升流对南极洲周围上层海洋甲基汞的贡献增加：鸟类沉积物中汞同位素的证据
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2024-01-31 , DOI: 10.1021/acs.est.3c06923
Hongwei Liu ₁ , Wang Zheng _{2,

3} , Yuesong Gao ₁ , Lianjiao Yang ₁ , Fange Yue ₁ , Tao Huang ₄ , Zhouqing Xie ₁

Affiliation

上升流在向上层海洋供应甲基汞 (MeHg) 方面发挥着关键作用，有助于海洋食物网中甲基汞的生物累积。然而，南大洋体积最大的水团——环极深水（CDW）的上升流对南极洲周围海洋和海洋生物群的甲基汞循环的影响仍不清楚。在这里，我们研究了受南极洲罗斯岛企鹅活动强烈影响的鸟类沉积剖面中的汞 (Hg) 同位素。结果表明，企鹅鸟粪是沉积物中汞的主要来源，汞的质量无关同位素分馏（以 Δ ¹⁹⁹ Hg 为代表）可以为企鹅积累的海洋甲基汞的来源提供见解。沉积物中的 Δ ¹⁹⁹ Hg 在大约公元 1550 年显着下降，这主要是由于 CDW 的上涌增强，将更多的 Δ ¹⁹⁹ Hg 较低的 MeHg 从较深的海水带到了上层海洋。我们估计来自更深海水的 MeHg 的贡献可能达到 38% 以上，以解释 1550 CE 时 Δ ¹⁹⁹ Hg 的下降。此外，我们发现，上升流的加剧可能增加了海洋生物的甲基汞暴露量，凸显了车辆碰撞波上升流对南极沿海生态系统甲基汞循环的重要性。

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Increased Contribution of Circumpolar Deep Water Upwelling to Methylmercury in the Upper Ocean around Antarctica: Evidence from Mercury Isotopes in the Ornithogenic Sediments

Upwelling plays a pivotal role in supplying methylmercury (MeHg) to the upper oceans, contributing to the bioaccumulation of MeHg in the marine food web. However, the influence of the upwelling of Circumpolar Deep Water (CDW), the most voluminous water mass in the Southern Ocean, on the MeHg cycle in the surrounding oceans and marine biota of Antarctica remains unclear. Here, we study the mercury (Hg) isotopes in an ornithogenic sedimentary profile strongly influenced by penguin activity on Ross Island, Antarctica. Results indicate that penguin guano is the primary source of Hg in the sediments, and the mass-independent isotope fractionation of Hg (represented by Δ¹⁹⁹Hg) can provide insights on the source of marine MeHg accumulated by penguin. The Δ¹⁹⁹Hg in the sediments shows a significant decrease at ∼1550 CE, which is primarily attributed to the enhanced upwelling of CDW that brought more MeHg with lower Δ¹⁹⁹Hg from the deeper seawater to the upper ocean. We estimate that the contribution of MeHg from the deeper seawater may reach more than 38% in order to explain the decline in Δ¹⁹⁹Hg at ∼1550 CE. Moreover, we found that the intensified upwelling may have increased the MeHg exposure for marine organisms, highlighting the importance of CDW upwelling on the MeHg cycle in Antarctic coastal ecosystems.

更新日期：2024-01-31

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