Geochemical rorms and risk assessment of some heavy metals in Aden coasts sediments, Yemen

Abstract

The objective of the present study is to investigate risk assessment and geochemical forms of Pb, Mn, Zn and Cu in Aden Coasts sediments as well as the content of sediment texture, organic carbon, and carbonates. Sequential extraction technique was applied to estimate the metals in five different fractions; exchangeable, bound to carbonate, bound to oxides, bound to organic matter and residual. The results indicated that the metals bound to non-residual fraction (anthropogenic input) represent 72.8 % of the total extractable fractions for Pb, 79.7 % for Mn, 87.4 % for Zn, and 87.3 % for Cu. The five fractions of the metals in the present study could be arranged in the following sequence: Residual > Exchangeable > Oxide form > Organic form > Carbonate for Pb; Residual > Oxides form > Organic form > Carbonate > Exchangeable for Mn or Zn; Organic form > Residual > Oxide form > Carbonate > Exchangeable for Cu. The risk assessment of the metals showed medium risk for Pb at all sampling sites except Sira zone which revealed very high risk to aquatic environment. Fractionation pattern of Zn and Cu showed low risk, while Mn showed low (most sites) to medium risk (Sira and Caltex) to aquatic environment. In general, the risk assessment of the metals in the study area decreased as follows: Pb >Mn>Zn> Cu.