Comprehensive pollution and ecological risk of heavy metals in an industrial region of south-west Bangladesh

Deterioration of water, soil and sediment due to industrial operation is well known. This study aimed to evaluate physicochemical properties of surface water and heavy metals in industrial effluent (n = 13), river water (n = 14), pond water (n = 5), soil (n = 11) and sediment (n = 19) collected from an industrial zone in south-west Bangladesh. Among the physicochemical parameters, pH and dissolved oxygen (DO) indicated relatively higher values in most of the samples than their respective lower guideline values of 6 and 4.5 mg L-1 and showed significant variation across environments. Based on the average concentration, none of the heavy metals in any environment surpassed the guideline values in the study area, except, Cr in both industrial effluent (0.034 ± 0.055 mg L-1) and river water (0.011 ± 0.005 mg L-1), Cd in both soil (1.11 ± 0.47 mg kg−1) and sediment (1.41 ± 1.04 mg kg−1). Possibly, continuous discharge of industrial effluents might increase the heavy metal concentrations in the effluent receiving environment. Concentration of others heavy metals were below the respective guideline values but varied significantly among the environments. Depth-wise variation was negligible which might be dependent on metal chemistry in soil and sediment. A very high pollution and ecological risk were observed for Cd, specifically in soil and sediment. Multivariate statistics showed strong correlation among heavy metals, which indicated considerable contribution from industrial effluent. Industrial operations control physicochemical properties of surface water, but temperature is dependent of meteorological conditions. This study concludes that the lower concentrations of heavy metals than guideline values in environmental samples still pose significant levels of pollution and ecological risks.