Evaluation of sediment contamination in the Red Sea coastal area combining multiple pollution indices and multivariate statistical techniques

Abstract

In the recent years, the Red Sea coast of Yemen has been severely affected by intensive anthropogenic activities. The current study constitutes a thorough inquiry to evaluate the extent of heavy metals pollution in Yemen's Red Sea coast sediment and identifies the possible sources of pollution. The concentrations of five metals (copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), and nickel (Ni)) collected from nine sites along the Red Sea coast of Yemen were assessed using an atomic absorption spectrophotometer (ASS). Sediment quality indices, such as the sediment quality guidelines (SQGs), potential ecological risk (RI), contamination factor (CF), pollution load index (PLI), geoaccumulation index (Igeo), and modified degree of contamination (mCd) were computed. In addition, multivariate statistical techniques (principal component analysis (PCA), hierarchical cluster analysis, and Pearson's correlation analysis) were applied to identify the potential sources of metals. The mean concentrations of Cu, Zn, Cd, Pb, and Ni were 51.3, 61.9, 4.02, 9.9, and 33.4 mg/kg dry wt, respectively. The spatial distribution revealed that the metals concentrations were high at the middle zone and low southward of Hodeida city. According to the SQGs, the adverse biological effects of metals were occasionally associated with Cu and Cd, frequently associated with Ni, and not expected to occur with Zn and Pb. The RI indicated that the sediment of the studied sites pose low (RI < 50) to considerable (100 ≤ RI < 200) ecological risk. The mean effect range-median quotient (M-ERM-Q) indicated that the combination of the studied metals had the toxicity probability of 21% at all studied sites. Igeo and CF indicated that the metals concentrations were in the descending order of: Zn > Ni > Pb > Cd > Cu, whereas the PLI and mCd indicated that Ras Isa (Site 5) and Urj village (Site 6) were the most polluted sites. PCA, cluster analysis, and correlation analysis found that Cd, Pb, and Ni mostly originated from anthropogenic sources while Cu and Zn were mainly derived from natural sources. Thus, it is evident that the intensive anthropogenic activities had negative influence on metals accumulation in the sediment of the Red Sea coast of Yemen leading to detrimental effects to the whole ecosystem. These comprehensive findings provide valuable information and data for future monitoring studies regarding heavy metals pollution and sediment quality at the Red Sea coast of Yemen.