Department of Chemistry, University of Girona, Campus Montilivi, s/n. 17071, Girona, Spain; Department of Chemistry, University of Kalyani, Kalyani, 741 235 West Bengal, India.
Sci Total Environ. 2014 Jan 15;468-469:804-12. doi: 10.1016/j.scitotenv.2013.08.087. Epub 2013 Sep 23.
Dissolved organic carbon (DOC) and Fe mineral phases are known to influence the mobility of arsenic (As) in groundwater. Arsenic can be associated with colloidal particles containing organic matter and Fe. Currently, no data is available on the dissolved phase/colloidal association of As in groundwater of alluvial aquifers in West Bengal, India. This study investigated the fractional distribution of As (and other metals/metalloids) among the particulate, colloidal and dissolved phases in groundwater to decipher controlling behavior of organic and inorganic colloids on As mobility. The result shows that 83-94% of As remained in the 'truly dissolved' phases (i.e., <0.05 μm size). Strong positive correlation between Fe and As (r(2) between 0.65 and 0.94) is mainly observed in the larger (i.e., >0.05 μm size) colloidal particles, which indicates the close association of As with larger Fe-rich inorganic colloids. In smaller (i.e., <0.05 μm size) colloidal particles strong positive correlation is observed between As and DOC (r(2)=0.85), which highlights the close association of As with smaller organic colloids. As(III) is mainly associated with larger inorganic colloids, whereas, As(V) is associated with smaller organic/organometallic colloids. Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy confirm the association of As with DOC and Fe mineral phases suggesting the formation of dissolved organo-Fe complexes and colloidal organo-Fe oxide phases. Attenuated total reflectance-Fourier transform infrared spectroscopy further confirms the formation of As-Fe-NOM organometallic colloids, however, a detailed study of these types of colloids in natural waters is necessary to underpin their controlling behavior.
溶解有机碳 (DOC) 和铁矿物相已知会影响地下水砷 (As) 的迁移性。砷可以与含有有机物和铁的胶体颗粒结合。目前，印度西孟加拉邦冲积含水层地下水溶解相/胶体砷的相关性数据尚不可用。本研究调查了砷（和其他金属/类金属）在地下水颗粒、胶体和溶解相中的分馏分布，以解析有机和无机胶体对砷迁移性的控制作用。结果表明，83-94%的砷仍存在于“真正溶解”相中（即<0.05μm 粒径）。铁和砷之间存在强烈的正相关（r² 在 0.65 到 0.94 之间），主要观察到较大（即>0.05μm 粒径）胶体颗粒中，这表明砷与较大的富含铁的无机胶体密切相关。在较小的（即<0.05μm 粒径）胶体颗粒中，砷与 DOC 之间存在强烈的正相关（r²=0.85），这突出了砷与较小的有机胶体的密切关联。As(III)主要与较大的无机胶体结合，而 As(V)则与较小的有机/有机金属胶体结合。扫描电子显微镜和能量色散 X 射线光谱证实了砷与 DOC 和铁矿物相的结合，表明形成了溶解的有机铁配合物和胶体有机铁氧化物相。衰减全反射-傅里叶变换红外光谱进一步证实了砷-铁-天然有机物金属胶体的形成，然而，需要对天然水中这些类型的胶体进行详细研究，以支持其控制作用。
