The impact of seasonal waterlogging on the depth-wise distribution of major and trace metals in the soils of the eastern Ganges basin

•Studied the seasonal waterlogging impact on metals distribution in floodplain soil.•Concentrations of trace metals and major oxides are higher in the WL profile.•Metals accumulation are higher in the topsoil layers due to silt and clay fractions.•Ni, As, Cr and Cu may cause occasional adverse biological effects to living organisms.•Soil texture, Fe/Mn oxyhydroxides and carbonates governed the metals distribution. In the Ganges River basin, studies related to the depth-wise distribution of major and trace metals in these floodplain soils (seasonally waterlogged and non-water logged) have been limited thus far. This research attempts to address this gap in the current literature by geochemical and geostatistical analyses and assessment of soil pollution. Significant concentrations of major and trace metals in these soils could greatly impact the health of local communities. Soil samples were collected in the eastern Ganges basin from a shallow seasonally waterlogged (SWL) site and a shallow non-waterlogged (SNWL) site up to 3 m below ground level (mbgl) and a deep seasonally waterlogged (DWL, up to 14 mbgl) site. The soils were analysed to determine soil texture and the concentration of major oxides and trace metals with increasing depth. The average concentration of trace metals (Ba, Rb, V, Cr, Ni, As, Pb, Ga, Co, Cs, Nb, W) and major oxides (Al2O3, Fe2O3, K2O, MgO) are higher in the SWL soil than the SNWL soil. A higher concentration of metals generally occurred in the upper soil layers due to the adsorption of elements by the silt and clay fractions. Soil pollution assessment indicated that W, As, Sb and Cu are enriched in both the waterlogged and non-waterlogged soils, while Sn is enriched in the SNWL soil profile only. The values obtained for the geochemical indices, which were geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF) and pollution load index (PLI), were relatively higher in the top layers for the SWL and DWL sites. Based on effects range-low (ERL) and effects range-median (ERM) values, the possibility of adverse biological effects caused by the metals is highest for Ni in the DWL site, Cr and Ni in the SWL site and Cu in the SNWL site. Pearson’s correlation and principal component analysis (PCA) justify the role of soil texture, phyllosilicates, Fe-Mn oxyhydroxides and carbonates in the occurrence and distribution of metals in these soils. Seasonal waterlogging facilitates the dissolution and precipitation of oxi