Heavy Metals in Coastal Sediments of Kudumbul Volcanic Island, Southeastern Red Sea, Saudi Arabia: Contamination, Source Constraints and Risk Assessment

Coastal sediments around volcanic islands may contain mixed geogenic signals from local lithology and localized non-lithogenic inputs. This study examines heavy metal (HM) patterns, contamination levels, source constraints, and screening-level health risks in coastal sediments from Kudumbul volcanic island in Saudi Arabia’s southeastern Red Sea. Thirty-five surface sediment samples were analyzed for Fe, Cr, Pb, Zn, V, Cu, and Ni using ICP-OES. Concentrations ranged from 1898–19,500 μg/g for Fe, 11.00–65.52 μg/g for Cr, 11.00–22.00 μg/g for Pb, 7.00–40.00 μg/g for Zn, 5.16–48.35 μg/g for V, 2.43–17.31 μg/g for Cu, and 1.00–88.00 μg/g for Ni. Compared with published background concentrations and sediment quality guidelines, most HMs showed generally low contamination levels across the island. However, Ni showed localized exceedance of the ERL at three sites and the ERM at one site. Contamination indices indicated low average contamination at the island scale, although Pb showed the highest relative enrichment and should be interpreted cautiously because of its limited concentration range and sensitivity to Fe normalization. Correlation analysis, HCA, and PCA identified a predominant Cr-Cu-Fe-Ni-V-Zn grouping compatible with basaltic and volcaniclastic sediment inputs, while Pb showed distinct behavior, implying different sediment partitioning or an additional localized source. Screening-level risk calculations identified ingestion as the primary exposure route, with estimates higher for children than adults under conservative assumptions. Non-carcinogenic risk remained below the threshold value of 1. Cancer-risk estimates warrant cautious interpretation because Cr speciation and bioaccessibility were not measured. These results establish a monitoring baseline for volcanic-island coastal sediments and highlight the need for site-specific background data and metal speciation in future evaluations.