Department of Chemical Engineering, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-Cho, Koganei, Tokyo, 184-8588, Japan.
Disaster Risk Reduction and Environment SBU, Kokusai Kogyo Co., Ltd, Shinjuku Front Tower 14F, 2-21-1 Kita-Shinjuku, Shinjuku-Ku, Tokyo, 169-0074, Japan.
Environ Sci Pollut Res Int. 2024 May;31(22):32407-32415. doi: 10.1007/s11356-024-33384-w. Epub 2024 Apr 23.
The dynamic change of redox conditions is a key factor in emission of elemental mercury (Hg) from riparian soils. The objective of this study was to elucidate the influences of redox conditions on Hg emission from riparian soils. Soil suspension experiments were conducted to measure Hg emission from five Hg-contaminated soil samples in two redox conditions (i.e., treated with air or with N). In four of the five samples, Hg emission was higher in air treatment than on N treatment. Remaining one soil, which has higher organic matter than other soils, showed no distinct difference in Hg production between air and N treatment. In soil suspensions subject to N treatment, the dissolved organic carbon (DOC) and Fe 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 Fe (r = 0.911, p < 0.01) and Hg (r = 0.815, p < 0.01) concentrations in soil solutions, suggesting Fe formation led to the release of DOC, which bound to Hg in the soil and, in turn, limited the availability of Hg for reduction to Hg in N treatment. On the other hand, for remaining one soil, more Hg might be adsorbed onto the DOM in the air treatment, resulted in the inhibition of Hg production in air treatment. These results imply that the organic matter is important to prevent Hg production by changing redox condition. Further study is needed to prove the role of organic matter in the production of Hg.
氧化还原条件的动态变化是河岸土壤元素汞（Hg）排放的关键因素。本研究旨在阐明氧化还原条件对河岸土壤 Hg 排放的影响。进行了土壤悬浮实验，以测量五种 Hg 污染土壤样品在两种氧化还原条件（即空气处理或 N 处理）下的 Hg 排放。在这五个样本中的四个中，空气处理下的 Hg 排放高于 N 处理。其余一个土壤的有机质含量高于其他土壤，在空气和 N 处理之间，Hg 的产生没有明显差异。在接受 N 处理的土壤悬浮液中，溶解有机碳（DOC）和 Fe 的浓度分别比空气处理高 3.38-1.34 倍和 1.44-2.28 倍。还发现土壤溶液中 DOC 和 Fe（r = 0.911，p < 0.01）与 Hg（r = 0.815，p < 0.01）浓度之间存在正相关关系，表明 Fe 的形成导致 DOC 的释放，DOC 与土壤中的 Hg 结合，从而限制了 Hg 在 N 处理中还原为 Hg 的可用性。另一方面，对于其余一个土壤，更多的 Hg 可能被吸附到空气处理中的 DOM 上，导致空气处理中 Hg 的产生受到抑制。这些结果表明，有机质通过改变氧化还原条件对 Hg 的产生具有重要意义。需要进一步的研究来证明有机质在 Hg 产生中的作用。
