Assessment of heavy metal pollution in surface water of Bangladesh

Abstract

Industrial discharge of heavy metals severely deteriorates surface water quality in many parts of the world, particularly in lower-middle-income countries like Bangladesh. This study collected published data from 30 different surface water bodies in Bangladesh, including rivers, lakes, freshwater wetlands (Haors), and river estuaries, on mean concentrations of 12 heavy metals (Cd, Pb, Cr, Hg, Zn, Cu, Ni, Al, Fe, Mn, As, and Co) in surface water bodies from 2010 to 2022. The study aimed to explore the pollution source and levels of heavy metals in the surface water of Bangladesh. The water quality status and correlations between variables were assessed using the heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and principal component analysis (PCA). The analysis results showed that the average heavy metal concentrations in the surface water of Bangladesh were in the order of Fe>Al>Mn>Cr>Zn>Cu>As>Ni>Pb>Co>Cd>Hg in the range of 3.98 ppm to 0.004 ppm. It also showed that Dhaka, Chittagong, Mymensingh divisions, and Bogra city of Rajshahi division are the most polluted areas of Bangladesh in terms of heavy metal concentration, whereas Khulna and Sylhet divisions are moderately polluted. The results showed that about 83.3 % of water bodies have HPI values greater than 100, which is considered unsafe for consumption. However, the HEI analysis revealed that about 46.7 % of water bodies were in the high pollution category (HEI > 20). The correlation matrix of heavy metals illustrated strong positive linear relationships between Cr and Co, Cu and As, Cu and Cd, and As and Cd. The principal component analysis suggested that the most contributing sources of pollution in the studied area are related to different anthropogenic activities, such as municipal waste and industrial effluent discharge, including tanneries, textile and dyeing industries, shipbreaking yards, and gas production plants, as well as agricultural runoff.