Algoa Bay sediment metal distribution and potential ecological riskassessment

Abstract

The study assessed the heavy metal distribution and ecological risk in marine sediments across three depths (10, 20 and 30 m) in Algoa Bay, South Africa. The concentration of heavy metals varied between depths, ranging from 0.8 to 124.5 mg/kg at 10 m depth contour, 0.5–96.7 mg/kg at 20 m depth contour and 0.7​​​​–113.3 mg/kg at 30 m depth contour determined using X-ray fluorescence (XRF). Higher concentrations were reported both at 10 and 30 m depths. The sediment quality was evaluated against the threshold effect concentration (TEC), probable effect concentration (PEC), effect range low (ERL) and effect range medium (ERM) guidelines. Pollution indices, including geoaccumulation (Igeo), the enrichment factor (EF), the pollution load index (PLI) and the potential risk index (PERI), consistently demonstrated anthropogenic accumulation of As, Ag, Cd and Hg. The PERI demonstrated the ecological risk from low to significantly high across all depths; 10, 20 and 30 m had PERI of 4013, 5391 and 5051, respectively.