Holistic risk assessment of heavy metal contamination in coastal zones under diverse anthropogenic pressures in a developing nation

Growing global concerns over heavy metal contamination in coastal environments are driven by the increasing impact of anthropogenic activities. This study investigated the contamination levels, ecological and human health risks, and potential sources of eight heavy metals (As, Cd, Cr, Fe, Mn, Ni, Pb, and Zn) in sediment samples collected from areas exposed to various anthropogenic activities (aquaculture, fisheries, tourism, power generation, and heavy industries) along a developing nation's coastline. Heavy metal concentrations in the studied sediments varied significantly, with Fe (27,342.1 ± 9064.09 mg kg⁻¹) and Mn (895.7 ± 269.24 mg kg⁻¹) dominating due to their lithogenic origin. Among trace metals, Zn (69.26 ± 11.18 mg kg⁻¹) and Cr (65.58 ± 28.47 mg kg⁻¹) were more prevalent than Pb, As, Ni, and Cd. Compared to mean crustal values, all metals except Mn and Cd were below crustal levels, with Cd showing significant enrichment and indicating severe localized contamination in the study area. Due to the dominance of Fe (96 % of total metal content), the highest metal abundances were found near estuarine regions (S1) and Fishery Ghat (S6), while the Thermal Power Plant (S5) and Shrimp Hatchery Area (S8) showed the lowest concentrations. Interestingly, despite lower overall metal concentrations, the heavy industrial area (S4) and tourist area (S7) exhibited the highest ecological risk due to the presence of hazardous metals. SQGs suggested that Cd and Cr may occasionally pose adverse effects on the coastal ecosystem. The risk indices (EF, PERI, mHQ) indicated that these stations pose a greater ecological threat compared to other locations. The Risk Index (RI) highlighted significant risks (> 100) from Cd, particularly at stations S4 and S7. Human health risk analysis revealed that Cr (carcinogenic) and Fe (non-carcinogenic) pose the highest health risks, with the sea beach area showing the greatest carcinogenic ingestion risk, especially for children (1.56E − 0 4 ) and adults (1.66871E -05 ). This study highlighted the need for stricter regulations, improved waste management, and enhanced monitoring to mitigate metal contamination risks in coastal zones. • Mean metal concentrations followed the decreasing order: Fe > Mn > Zn > Cr > Pb > As > Ni > Cd. • The estuarine area and Fishery Ghat had the highest metal abundances. • Industrial and tourist areas showed the highest ecological risks. • Cd and Cr occasionally pose adverse effects on the coastal ecosystem. • Human health risk from Cr (carcinogenic) was highest at the sea beach areas for children.