Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan.
Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan.
Sci Total Environ. 2022 Apr 1;815:152492. doi: 10.1016/j.scitotenv.2021.152492. Epub 2021 Dec 24.
The purpose of this study was to investigate the behavior of previously discharged mercury (Hg) released from the Itomuka Hg mine into the surrounding environment, especially into soil. Total-Hg (T-Hg), methylmercury (MeHg), and ethylmercury (EtHg) concentrations in the surface soil at eight sample sites around the mine were 3.8-64.2 mg/kg, 6.0-54.7 μg/kg, and undetected to 4.5 μg/kg, respectively. Core samples collected from seven of the eight sample sites showed that the vertical distribution of T-Hg was the highest in the surface soil layer and decreased rapidly in the lower layers. A strong positive correlation was observed between T-Hg and MeHg concentrations in the core samples; however, the slope of the regression line varied considerably for each core. This suggests that Hg and MeHg were not supplied from the atmosphere simultaneously, but rather that MeHg was produced on-site. Further, the formation of MeHg and EtHg in soil was considered in terms of the total organic carbon/total nitrogen ratio, which is a decomposition index of soil organic matter. The strong positive correlation between T-Hg and MeHg can be attributed to the migration of organic matter containing Hg species to the lower layers. There was no relationship between T-Hg and MeHg at the riverbed sample site because of the high T-Hg in the lower soil layers, suggesting that Hg was supplied by ore at this sample site. These assumptions of the formation change and migration of Hg in soil were supported by the results of the fractionation experiment and the elution test. To understand the current conditions in this area, measurements of Hg in the water, sediment, atmosphere, and plants were also conducted.
本研究旨在调查伊托木卡汞矿释放到周围环境（特别是土壤）中的已排放汞（Hg）的行为。矿区周围 8 个采样点的表层土壤中总汞（T-Hg）、甲基汞（MeHg）和乙基汞（EtHg）的浓度分别为 3.8-64.2mg/kg、6.0-54.7μg/kg 和未检出至 4.5μg/kg。从 8 个采样点中的 7 个采集的芯样表明，T-Hg 的垂直分布在表层土壤中最高，在下部迅速下降。芯样中 T-Hg 和 MeHg 浓度之间观察到强烈的正相关；然而，回归线的斜率因每个芯样而异。这表明 Hg 和 MeHg 不是同时从大气中供应的，而是在现场生成的。此外，根据总有机碳/总氮比（土壤有机质分解指标）考虑了土壤中 MeHg 和 EtHg 的形成。T-Hg 和 MeHg 之间的强烈正相关可归因于含 Hg 物种的有机物向较低层迁移。由于下部土壤层中 T-Hg 含量较高，河床采样点处 T-Hg 和 MeHg 之间没有关系，这表明该采样点的 Hg 是由矿石供应的。土壤中 Hg 形成变化和迁移的这些假设得到了分馏实验和洗脱试验结果的支持。为了了解该地区的现状，还对水、沉积物、大气和植物中的 Hg 进行了测量。
