Spatio-temporal analysis of heavy metals in the sediment of lower Meghna river using contamination indices, multivariate statistics and GIS techniques

The study aimed to measure heavy metals concentration in the lower Meghna river's surface sediments considering seasonal variation using multivariate statistics, contamination indices, and Geographical Information System (GIS). The mean concentration of heavy metals in most sampling sites was below the standard level except Ni in both dry and wet seasons. In terms of contamination factor (CF) in the dry and wet seasons, all samples showed moderate contamination of Ni. The contamination degree (CD) of samples revealed moderate contamination in the dry season in comparison with wet seasons. Furthermore, the geo-accumulation index ( I geo ) indicated that river sediment was uncontaminated at most sites. In the wet season, the potential ecological risk was low compared to the dry season. Inverse Distance Weighted (IDW) analysis found diverse patterns of spatial and seasonal variation of heavy metals. Principal Component Analysis (PCA) revealed the significant contribution with components in the following order Cr > Cd > Ni > Pb > Mn in dry season and Pb > Cr > Cd > Ni > Mn in the wet season. The pollution is likely to negatively impact the ocean-river system, including the food chain and estuarine chemical processes. The outputs of this study could be used to understand the adverse impact of industrial and anthropogenic sources of pollution and illustrate pollutant transfer pathways from the river to the marine environment.