Natural attenuation in marine sediments: investigation of the effect of chloride concentration on the mobility of metals

Abstract

Metals can be mobilized from contaminated sediments under variable environmental conditions. This paper discusses the effects of specific ions of the water column in conjunction with natural attenuation processes on the leaching of metals from marine sediments. In particular, the effect of the salinity and the presence of ions in the seawater, especially the chlorides of the water column, in leaching of metals was examined. Sediment samples were collected from sampling stations in the inner port of Piraeus, Greece. Due to the fact that natural attenuation is a slow procedure which consists of natural, chemical, and biological processes and is influenced by many factors, it was approached with experiments taking place under quite aggressive conditions. Sequential leaching tests in cycles of seven repetitions were performed. The results of these experiments showed that leaching of metals from contaminated sediments to the water column was influenced by the concentration of dissolved constituents. Initially leaching was significant with maximum concentration of leachable copper (Cu) 0.25mg/kg, lead (Pb) 0.0048mg/kg, and zinc (Zn) 0.28mg/kg, and then fell in the last repetitions. The leaching of Cu and Zn from contaminated sediments to the water column was positively correlated to the concentration of chlorides.