Comprehensive Evaluation of Some Toxic Metals in the Surface Water of Louhajang River, Bangladesh

Abstract

\n Louhajang River, Bangladesh, crosses Tangail, which is a densely industrialized and urbanized city. Louhajang River is an essential water source for domestic, irrigation, and urbanization purposes. This study reports the levels of pH, electrical conductivity (EC), and some toxic heavy metals in 40 water samples collected during summer and winter seasons from Louhajang River. The levels were found to be in the ranges of pH 6.22-7.43 and EC 345-798 mS/cm, Cr 0.18-13.2, Ni 0.02-19.04, Cu 0.96-15.92, As 2.18-12.51, Cd 0.02-2.42, and Pb 0.49-15.74 µg/L. The winter season reported higher levels of the examined parameters than the summer season with significant variation (p < 0.05) for all parameters, with the exception of Cd. The metal contents were assessed against local and international standards for drinking, irrigation and aquatic life purposes where different trends were observed. The heavy metal evaluation index (HEI) and the ecological risk index (ERI) reported low to moderate risks. The spatial distribution of metal contents assigned hot spots in some sites along the riverbed, which were attributed to specific manmade sources. The health risk assessment for three population categories, i.e., adult male, adult female, and children, were examined in terms of hazard index (HI) and total cancer risk (TCR) for oral and dermal pathways during both seasons. Cr and Cd recorded HI more than unit in all cases, indicating possible non-cancer risk. TCR values of As for the three examined population categories during both seasons were > 1.0×10-6, indicating possible cancer risk, while that of Pb were < 1.0×10-6. For Ni, about 10-25% of the sampled sites recorded TCR > 1.0×10-6.