Investigating the sensitivity of fluvial processes on arsenic enrichment in the mid-Gangetic floodplains of India

The present study traces the geochemical occurrence of arsenic and Heavy Metals along the active oxbow formations of river Ganga in MGP. Strong influence of silicate weathering and anthropogenic leaching of fertilizers is concurrently occurring with pyrite oxidation leading to high arsenic vulnerability. While most carbonate minerals are in a state of oversaturation but monsoon led bi-carbonate enrichment play a major role via replacement of adsorbed arsenic under conditions suitable for microbial degradation. Further, the steep changes in river directional profile has caused high sediment deposition and compaction leading to increase in the soil bulk density, which interestingly traces the river flow path, coherent with the spatial distribution of soil organic carbon stock (socs). Further, localized concentration of arsenic matches the variation profile of clay content and iron concentration of the soil confirming the role of river led recharge in promoting oxidizing conditions within small stretch of study area. Low cation exchange capacity further supports our concern for groundwater vulnerability in terms of enhanced cation retention of the soil. Our study is a pioneering work in understanding arsenic spatial vulnerability under fluvial forcing through developing indicators which trace the arsenic mobilizing chemistry in a more coherent and direct ways.