Hydrogeochemical analysis of groundwater quality for drinking and irrigation with elevated arsenic and potential impact on agro-ecosystem in the upper Brahmaputra plain, India.

Abstract

The upper Brahmaputra floodplain is considerably enriched with geogenic contaminants, mainly Arsenic (As) exhibiting high spatial heterogeneity. With this concern, the present study was conducted in Lakhimpur district located in the upper Brahmaputra floodplain aiming to assess the groundwater (GW) suitability for drinking and irrigation. Chemical analysis of 78 GW samples revealed significantly high As (max 0.12 mgL-1, mean 0.02 mgL-1) followed by iron (max 62.2 mgL-1, mean 19.94 mgL-1) showing uneven distribution. Hydrogeochemical analysis of the GW samples revealed that majority of the water samples belong to mixed Ca2+- Na+- HCO3- type with weathering and forward ion exchange as the dominant processes in the aquifer system. Positive correlation among iron (Fe) and As, together with close grouping in hierarchical cluster analysis and principal components analysis, indicated the involvement of reductive hydrolysis process. Calculation of saturation indices indicated that, precipitation of Fe minerals may lead to de-coupling of Fe and As contributing to the enrichment of both the elements in the GW. Further, assessment of key parameters for irrigation water quality including water quality index indicated the GW to be suitable for irrigation purpose. Finally, toxicity implications of crops produced from As contaminated water indicated higher accumulation potential of As in the food grains implying significant impacts on the agro-ecosystem and associated health hazards.