The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Trench sediments receive mercury (Hg) from the upper ocean, serving as a crucial global Hg sink. To trace Hg cycling evolution in trenches before the Anthropocene, we analyzed the Hg contents and isotopes in a Mariana Trench sediment core. The Δ¹⁹⁹Hg and Δ²⁰⁰Hg values, and the Δ¹⁹⁹Hg/Δ²⁰¹Hg slope indicated that Hg was influenced by atmospheric or seawater photochemical processes before deposition. Geological proxies and large negative δ²⁰²Hg values consistent with volcanic rocks suggested that the increased Hg content during the Deglacial period was due to geological Hg input. During the Holocene, atmospheric deposition was the main Hg source in the Mariana Trench, while a combination of atmospheric and biogenic sources occurred during the Last Deglaciation. Our findings indicate that Hg sources in the Mariana Trench varied from the Last Deglaciation to the Holocene, likely due to environmental and geological changes.
 

Mariana Trench sediment, last deglaciation, Hg isotopes, mercury