Heavy metal(loid) pollution in the Laukhati River water of Bangladesh: Environmental implications for the Patuakhali coastal region

The Laukhati River, a vital freshwater source in the urbanized Patuakhali coastal region of Bangladesh, is increasingly threatened by anthropogenic inputs, raising serious concerns at both local and national levels. This study aimed to assess heavy metal(loid) contamination and associated ecological risks in the river water. Water samples from five locations were analyzed using atomic absorption spectroscopy (AAS) to quantify Cr, Ni, Cu, Cd, Pb, and As concentrations, which ranged from 2.81 to 6.83, 1.24 to 5.41, 2.86 to 5.37, 0.97 to 2.12, 1.26 to 1.75, and 1.65 to 2.51 µg/L, respectively. Source apportionment indicated predominantly anthropogenic origins, with metal(loid) abundance following the order: Cr > Cu > Ni > As > Cd > Pb. Station-wise distribution revealed higher concentrations at upstream sites, and spread in the following order: St-2 > St-1 > St-3 > St-4 > St-5. Among all metal(loid)s, arsenic (As) exhibited the highest toxicity load (HMTL: 16424.8 µg/L) with a required removal efficiency (RTMRPL) of 89.81%. Contamination degree (CD) values suggested low overall pollution, and pollution index (PI) values classified the area as low risk (Class 1). However, cadmium (Cd) posed the most significant individual risk (RI), with ecological risk index (ERI) values ranging from 6.446 to 13.705, indicating generally low ecological risk. The study revealed that the Laukhati River has a generally lower status in terms of overall heavy metal pollution and ecological risk. The findings highlight the urgent need for strict enforcement of waste discharge regulations and effective management of vessel-derived pollution.