Anthropogenic and natural contribution of potentially toxic elements in southwestern Ganges-Brahmaputra-Meghna delta, Bangladesh.

Elemental composition, multivariate statistical analyses with the absolute principal component score-multiple linear regression (APCS-MLR) model, and different pollution indices in Upper and Lower Southwestern Ganges-Brahmaputra-Meghna (GBM) delta sediments were studied to characterize pollution, ecological risk and quantify potential toxic element sources of the area. Toxic metals concentrations were higher in Lower Delta and individual pollution indices showed Upper Delta was moderately polluted by arsenic, chromium, cobalt, copper and lead, and Lower Delta was moderately-strongly polluted by the same metals. Synergistic indices include Potential Ecological, Toxic, Nemerow, and Pollution Risk indices in Upper and Lower Delta sediment ranged from 47.17-128.07, 2.03-12.19, 29.92-65.42, 0.28-1.62, and 69.17-246.90, 8.00-13.47, 20.53-152.92, 1.18-1.58, indicated low and moderate risk pollution, respectively. Statistical models represent the metals dominantly originated from nature for Upper Delta, and both natural and anthropogenic activities contributed to Lower Delta sediment. The study found that the modern deposit in Lower Delta became more contaminated and thus enhanced ecological risk.