“Unraveling Mercury’s Escape: How Oxygen and Soil Composition Influence Elemental Mercury Production in Riparian Environments” 水辺の土壌からの水銀放出の謎：酸素と土壌組成が元素状水銀生成に与える影響を解明
利谷研究室と共同研究者たちは、土壌中の酸素量が、汚染された河川敷地域からの元素状水銀の放出量に大きな影響を与えることを発見しました。この研究では、空気がある状態とない状態という異なる条件下で土壌サンプルを調査し、水銀の挙動を理解しようとしました。その結果、ほとんどの場合、空気が存在する時により多くの水銀が放出されることがわかりました。しかし、有機物が多い土壌では結果が異なりました。この研究は、河川敷環境における水銀汚染の管理方法の改善に役立ち、水銀の放出を制御する上で土壌組成が重要であることを強調しています。Scientists from Riya Lab and their collaborators have discovered that the amount of oxygen in soil can significantly affect how much elemental mercury is released from contaminated riverside areas. This study examined soil samples under different conditions – with and without air – to understand how mercury behaves. They found that in most cases, more mercury was released when air was present. However, in soil with high organic matter, the results were different. This research helps us understand how to better manage mercury pollution in riverside environments and highlights the importance of soil composition in controlling mercury emissions.
ORIGINAL ARTICLE:
https://doi.org/10.1007/s11356-024-33384-w
Elemental mercury production from contaminated riparian soil suspensions under air and nitrogen bubbling conditions
Shuting Zhao, Akihiko Terada, Makoto Nakashima, Takeshi Komai, Shohei Riya, Masaaki Hosomi & Hong Hou
The dynamic change of redox conditions is a key factor in emission of elemental mercury (Hg0) from riparian soils. The objective of this study was to elucidate the influences of redox conditions on Hg0 emission from riparian soils. Soil suspension experiments were conducted to measure Hg0 emission from five Hg-contaminated soil samples in two redox conditions (i.e., treated with air or with N2). In four of the five samples, Hg0 emission was higher in air treatment than on N2 treatment. Remaining one soil, which has higher organic matter than other soils, showed no distinct difference in Hg0 production between air and N2 treatment. In soil suspensions subject to N2 treatment, the dissolved organic carbon (DOC) and Fe2+ concentrations were 3.38- to 1.34-fold and 1.44- to 2.28-fold higher than those in air treatment, respectively. Positive correlations were also found between the DOC and Fe2+ (r = 0.911, p < 0.01) and Hg2+ (r = 0.815, p < 0.01) concentrations in soil solutions, suggesting Fe2+ formation led to the release of DOC, which bound to Hg2+ in the soil and, in turn, limited the availability of Hg2+ for reduction to Hg0 in N2 treatment. On the other hand, for remaining one soil, more Hg2+ might be adsorbed onto the DOM in the air treatment, resulted in the inhibition of Hg0 production in air treatment. These results imply that the organic matter is important to prevent Hg0 production by changing redox condition. Further study is needed to prove the role of organic matter in the production of Hg0.