The Biogeochemical Differentiation and Movement of Arsenic within Groundwater Aquifers Amid Fluctuating Redox States

(https://doi.org/10.5281/zenodo.22184730)

सार

This widespread contamination of groundwater formation by natural sources of arsenic is an unprecedented environmental and public health crisis, especially in the deltaic and alluvial areas throughout the world. Geographical distribution and water solubility of arsenic is essentially controlled by the complex biogeochemical cycling of redox sensitive elements such as iron, manganese and sulfur under changing hydrodynamic conditions. This is a detailed study paper that methodologically reviews the processes that affect arsenic speciation and mobilization in different redox situations such as sub-daily variations associated with the tide, plus seasonal recharge of the groundwater and anthropogenic disturbance from agricultural activities. The traditional view is that the release of arsenic is due primarily to the reductive dissolution of the iron (oxyhydr) oxides, but from the current multi-scale evidence, there is strong evidence of an important geochemical separation of iron and arsenic. The separations of these due to the precipitation of secondary minerals like magnetite, green rust, and authigenic sulfides of different affinities to arsenite, (As (III)), and arsenate, (As (V)). In addition, this study examines kinetic constraints of arsenic oxidation by the biogenic manganese oxides (BMOs), their inhibitory effect in natural organic matter (NOM) and the evolution of integrated catalytic mechanisms such as bio-electro-Fenton processes. Inclusion of high-resolution spectroscopic data and use of reactive transport models like PHT3D and CD-MUSIC, has important implications regarding predictions and remediation in environments exposed to imminent hydro-climatic changes, as discussed in this article.