Abstract

Shallow harbours with contaminated sediments are subjected to the risk of uncontrolled resuspension of sediment, which could remobilize weakly bound heavy metals into overlying water and pose a potential risk to aquatic ecosystem. Remediation of sediments in these areas cannot be performed by conventional in situ and ex situ remediation methods. Alternatively, the resuspension technique was introduced to address these issues. The concept of the resuspension method is that finer sediments have a greater tendency to adsorb the contamination due to their specific surface area and ionic attraction. Therefore, finer particles were targeted for removal from the aquatic environment by a suspension mechanism in a confined water column. The main objective of this study was to evaluate the feasibility of the resuspension technique as a new approach for remediation of contaminated sediment and a viable option to reduce the risk of remobilization of pollutants in harbours. The results indicated that the resuspension technique could successfully reduce the total concentration of contaminants (i.e. Cr, Co, Ni, Cu, Zn, As, Cd and Pb) in almost all samples below the probable effect level with no significant change in the overlying water quality. Precisely, by removing just 4% of contaminated sediment in this method, the contamination intensity of Cd and Pb (as the main pollutants) was reduced by 26 and 28 percent and for the rest of the contaminants returned to the non-polluted level. Removal efficiency of heavy metals was positive with a minimum 17.6% for Co and a maximum for
25.9% for Zn. The results of the sequential extraction test (SET) also illustrated that the contaminant removal efficiency could be drastically enhanced for metals in sediment with a higher enrichment factor. Principal component analysis, performed on the data sets from the SET results, implied the significance of the anthropogenic factor in contaminating the sediments in the study area. Removal of contaminants from sediment through this method could also reduce the risk of mobility and availability of metals under changing environmental conditions. No chemical substances were employed in the resuspension method. Subsequently, less destruction can be caused in the aquatic ecosystem.