Evaluating contamination of dredges and disposal criteria in Greek coastal areas

Abstract

Sediments were collected from areas that were going to be dredged located at six small Greek ports, as well as from possible disposal areas. In order to assess the contamination level of dredged material, the samples were analysed for pH, organic matter, the metals Cd, Pb, Hg, Cr, Ni, Cu, Zn and major organic compounds (PAHs, PCBs). The sediments’ quality was evaluated by two approaches: (i) by classifying each area according to two sets of Sediment Quality Guidelines (SQGs) and (ii) by calculating the contamination factors and degree for each area. The results showed that organic compounds were detected in trace amounts in 14% of the port samples belonging to the PAHs group. The characterization of the sediment samples was based on the metals’ concentration showing that the majority of the areas to be dredged (80%) are classified as of medium–low contamination according to the SQGs. However, according to the contamination degree, only 30% of the areas are classified as of low contamination, while 40% as of moderate contamination and 30% of the areas as of considerable contamination. From the point of view of “no disturbance” of the ecosystem, decisions about dumping should be taken only after evaluating the material to be dredged. If the SQGs are exceeded, dumping must be forbidden. Otherwise, further evaluation is needed based on the comparison with the receiving area, i.e. by estimating the contamination degree. Dumping could be allowed if the contamination degree is found to be below moderate.