Oxidative
Dissolution
of Sulfide Minerals Tends to
Accumulate More Dissolved Heavy Metals in Deep Seawater Environments
than in Shallow Seawater Environments
posted on 2023-12-05, 15:04authored bySiyi Hu, Chunhui Tao, Shili Liao, Yao Guan, Xuebo Yin, Chuanwei Zhu, Jin Liang, Zhikui Guo
Deep-sea
mining magnifies the release of heavy metals
into seawater
through oxidative dissolution of seafloor massive sulfide (SMS). At
present, there is little information about how the metals released
into seawater might be affected by the mineral assemblages, seawater
conditions, and solid percentages. Here, leaching experiments were
carried out to examine the behavior of three sulfides from the Southwest
Indian Ridge, under conditions that replicated deep and shallow seawater
environments at three solid–liquid ratios. The results demonstrated
that sphalerite dissolved rapidly, and the metals released in both
experimental conditions were comparable, potentially reflecting galvanic
interactions between the sulfide minerals. Large quantities of the
released metals were removed from the solutions when hydrous ferric
oxides formed, especially for shallow seawater conditions. A comparison
of metal concentrations in the leachates with the baseline metal concentrations
in natural seawater indicated that most of the released metals, when
diluted with seawater, would not have widespread impacts on ecosystems.
Based on the obtained unique oxidative dissolution properties of each
SMS at variable solid–liquid ratios, targeted wastewater discharge
treatments are proposed to minimize impacts from the dissolved metals.
This study will support the development of robust guidelines for deep-sea
mining activities.