Contamination level of heavy metals and assessment of the ecologic risk in the surface water and sediments of Batanghari river Dharmasraya, Indonesia

Heavy metals contamination in river surface water and sediments represents a critical environmental issue on a global scale.The Batanghari river in Dhamasraya region plays a main role in domestic water supply and agricultural activities, necessitating a comprehensive investigation into heavy metal contamination within its water and sediment.The aims of this study were to visualize the overview of the heavy metals concentration present in the Batanghari river and to assess the contamination degree using several ecological assessment tools, such as the enrichment factor (EF), geo-accumulation index (I geo ), contamination factor (C f ), contamination degree (CD), ecological risk index (E r ), and potential ecological risk index (RI).The samples of surface water and sediment were obtained from 15 locations along the Batanghari river.The heavy metal analysis in the water samples revealed that the Fe, Zn, and Cd concentrations exceeded the established safety thresholds.The mean concentrations observed in the water in the following descending order was, 1.030 mg/L, 0.380 mg/L, 0.005 mg/L, for Fe, Zn and Cd, respectively, while Cu and Pb concentration were not detected.Meanwhile, the concentrations in the sediment were significantly higher, with the following mean values: 14,422.37mg/kg for FE, 53.05 mg/kg for Zn, 22.37 mg/kg for Cu, 18.00 mg/kg for Pb, and 0.13 mg/kg for Cd.Furthermore, EF, Igeo, Cf, and Er evaluations, Fe contamination was classified as high, while Pb and Cu showed low to moderate contamination levels, and Zn and Cd were categorized as low.Moreover, the contamination degree and potential ecological risk analyses indicated the highest pollution level were in downstream areas.Although pollution sources such as domestic effluents, road runoff, local mining, and agricultural activities were more prevalent in upstream and midstream regions, the mobilization of heavy metals through river flow led to their accumulation downstream.