Seasonal dynamics of trace elements, sediment contamination, and child health risks in six Egyptian red sea ports: an integrated water-sediment-human health assessment.

Coastal port environments along the Red Sea-Suez Canal corridor face intensifying multi-stressor pressures, yet integrated seawater-sediment-human-health assessments of toxicologically distinct trace elements remain scarce. In this study, arsenic (As), selenium (Se), tin (Sn) and mercury (Hg) were quantified in surface seawater (n = 38) and surficial sediments (n = 19) across six Egyptian ports (Port Tawfiq, Zayteiat, Hurghada, Safaga, Nuweibaa and Sharm El-Sheikh). Six contamination and ecological-risk indices (CF, Igeo, PLI, MPI, Er and RI) were integrated with a USEPA-compliant human health risk assessment and multivariate source apportionment to disentangle natural and anthropogenic signatures. Dissolved As exhibited a pronounced and biogeochemically coherent seasonal inversion, with winter concentrations (8.82 ± 1.04 µg L-1) 3.2-fold higher than summer values (2.76 ± 0.53 µg L-1; p < 0.001), whereas Se followed the opposite trend (summer > winter; p < 0.001). All stations fell within the "low" ecological-risk category, with sediment-based indices uniformly low (PLI = 0.07-0.47; RI = 3.6-22.4). Critically, non-carcinogenic hazard indices for children exceeded unity at all six ports (HI = 1.13-1.57), driven predominantly (> 92%) by As, an exceedance that would be masked by adult-only assessment (HI = 0.50-0.67). Total carcinogenic risk remained within the acceptable 10-6-10-4 range. Principal component analysis and inter-element correlations (r ≥ 0.84, p < 0.001) resolved two anthropogenic clusters: a legacy antifouling-paint (Sn-As-Hg) signature at high-traffic ports persisting over a decade after the 2008 IMO organotin ban, and petroleum-related Se enrichment at the Zayteiat oil terminal. These findings highlight the necessity of age-stratified exposure assessment and sustained multi-compartment monitoring as Suez Canal traffic intensifies.