2024-06-07 カリフォルニア大学サンディエゴ校(UCSD)
◆研究はモノメチル水銀の海洋中の発生源を特定するための重要な一歩であり、水銀排出を減少させることで海洋食物網における毒素の濃度がどの程度減少するかを予測するための鍵となります。
◆研究チームは、沿岸の湧昇現象が水銀レベルを高めることを確認し、これにより水銀が海面に運ばれることを明らかにしました。さらに、ジメチル水銀がモノメチル水銀の安定性を保つ役割を果たしている可能性が示唆されました。これらの発見は、水銀排出削減の効果を予測するために必要な知識を提供します。
＜関連情報＞
- https://today.ucsd.edu/story/study-illuminates-previously-unknown-ocean-mercury-pathway
- https://pubs.acs.org/doi/10.1021/acs.est.4c01112
生産性の高い湧水系におけるモノメチル水銀の発生源としてのジメチル水銀 Dimethylmercury as a Source of Monomethylmercury in a Highly Productive Upwelling System
Hannah M. Adams, Xinyun Cui, Carl H. Lamborg, and Amina T. Schartup
Environmental Science & Technology Published:June 7, 2024
DOI:https://doi.org/10.1021/acs.est.4c01112
Abstract
Monomethylmercury (MMHg) is a neurotoxicant that biomagnifies in marine food webs, reaching high concentrations in apex predators. To predict changes in oceanic MMHg concentrations, it is important to quantify the sources and sinks of MMHg. Here, we study mercury speciation in the California Current System through cruise sampling and modeling. Previous work in the California Current System has found that upwelling transports mercury-enriched deep waters to productive surface waters. These upwelled waters originate within the California Undercurrent water mass and are subsequently advected as a surface water parcel to the California Current. Between the two major water masses, we find that compared to the California Current, the California Undercurrent contains elevated dissolved total mercury (THg) and dimethylmercury (DMHg) concentrations by 59 and 69%, respectively. We explain that these differences result from losses during advection, specifically scavenging of THg and DMHg demethylation. We calculate a net DMHg demethylation rate of 2.0 ± 1.1% d–1 and build an empirically constrained mass budget model to demonstrate that net DMHg demethylation accounts for 61% of surface MMHg sources. These findings illustrate that DMHg is a significant source of MMHg in this region, challenging the current understanding of the major sources of marine MMHg.
