Assessment of water quality and heavy metal indices in a tropical freshwater river for aquatic life and public health standard

We investigated the spatial-temporal variability, contamination sources, and risk of heavy metals (HMs) on environment and public health in water of the Barnoi River, Bangladesh from July 2019 to June 2020. Surface waters were sampled from five distinct sampling sites and measured for physico-chemical parameters (temperature, pH, dissolved oxygen, total alkalinity, total hardness, total dissolved solids, electrical conductivity, biological oxygen demand, nitrate-nitrogen and phosphate-phosphorus) and HMs (As, Cd, Cr, Pb, Ni, Cu and Zn) content. Physico-chemical parameters were analyzed following standard procedure, and HMs concentration was analyzed by an atomic absorption spectrophotometer (AAS). We assessed the surface water quality for drinking and aquatic life standard, metal pollution indices (HPI and HEI) and non- cancer and cancer risks. Furthermore, we employed correlation analysis (CoA), principal component analysis (PCA), and cluster analysis (CA), to define the inter-metal relationship, distribution and potential origin. Our results indicated that all physico-chemical parameters satisfied drinking and aquatic life standards (WHO, USEPA). However, among the analyzed HMs, Cr, As, Pb and Cd surpassed the maximum recommended value. Principle component analysis (PCA) revealed distribution of the studied metals, possibly anthropogenic sources (industrial, agricultural, household, and municipal wastewater). Based on the indices, the Barnoi River water was 'undrinkable' (DWQI = 158.66) and the index value was higher at Site-1 and Site-2. However, the CCME-WQI index for aquatic life or fisheries indicated that the surface water was in a 'fair' condition (CCME-WQI = 70.65). The mean values of HPI (257.41) and HEI (17.47) indicate 'unsuitable for drinking' and 'medium pollution' conditions of the surface water, respectively. Health risk evaluation revealed that children are more susceptible to both non-carcinogenic and carcinogenic risks by Cr, As and Ni than the adults. Regular monitoring is recommended by the responsible authorities and policymakers.