Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
Int J Environ Res Public Health. 2022 Mar 15;19(6):3465. doi: 10.3390/ijerph19063465.
The reduction and transformation of arsenic-bearing ferrihydrite by arsenate-iron reducing bacteria is one of the main sources of arsenic enrichment in groundwater. During this process the coexistence cations may have a considerable effect. However, the ionic radius of calcium is larger than that of iron and shows a low affinity for ferrihydrite, and the effect of coexisting calcium on the migration and release of arsenic in arsenic-bearing ferrihydrite remains unclear. This study mainly explored the influence of adsorbed Ca on strain JH012-1-mediated migration and release of arsenate in a simulated groundwater environment, in which 3 mM ferrihydrite and pH 7.5. Ca were pre-absorbed on As(V)-containing ferrihydrite with a As:Fe ratio of 0.2. Solid samples were analyzed by X-ray diffraction (XRD), scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that calcium and arsenate can synergistically adsorb on ferrihydrite due to the electrostatic interactions, and the adsorbed Ca mainly exists on the surface through the outer-sphere complex. Adsorbed Ca entering the stimulated groundwater was easily disturbed and led to an extra release of 3.5 mg/L arsenic in the early stage. Moreover, adsorbed Ca inhibited biogenic ferrous ions from accumulating on ferrihydrite. As a result, only 12.30% Fe(II) existed in the solid phase, whereas 29.35% existed without Ca adsorption. Thus, the generation of parasymplesite was inhibited, which is not conducive to the immobilization of arsenic in groundwater.
砷铁氢氧化物被砷酸盐还原菌还原和转化是地下水中砷富集的主要来源之一。在此过程中，共存阳离子可能会产生相当大的影响。然而，钙离子的离子半径大于铁离子，对铁氢氧化物的亲和力较低，共存钙离子对含砷铁氢氧化物中砷的迁移和释放的影响尚不清楚。本研究主要探讨了吸附态 Ca 对模拟地下水中菌株 JH012-1 介导的砷酸盐迁移和释放的影响，其中 3 mM 铁氢氧化物和 pH 值为 7.5。Ca 预先吸附在含砷铁氢氧化物上，砷与铁的比例为 0.2。通过 X 射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和 X 射线光电子能谱（XPS）对固体样品进行分析。结果表明，由于静电相互作用，钙和砷酸盐可以协同吸附在铁氢氧化物上，吸附态的 Ca 主要通过外球络合物存在于表面。进入刺激地下水中的吸附态 Ca 很容易受到干扰，导致砷的额外释放 3.5mg/L。此外，吸附态 Ca 抑制了生物生成的亚铁离子在铁氢氧化物上的积累。结果，只有 12.30%的 Fe(II)存在于固相，而没有 Ca 吸附时存在 29.35%的 Fe(II)。因此，抑制了副砷铁矿的生成，不利于地下水砷的固定。
