Determination of the Lability Characteristics of Lead,Cadmium and Zinc in a Polluted Mediterranean Brackish-Marine Interface System

Labile and non-labile fractions of zinc, lead and cadmium are studied throughout the mixing process of the waters of a small brackish, polluted lake (Koumoundouros lake) with the seawaters of the adjacent Elefsis Bay, employing Differential Pulse Anodic Stripping Voltammetry (DPASV) and Chelex-100 resins. The metal fractions were classified according to their relative lability as: very labile, moderately labile, slowly labile andinert. Their distribution is determined mainly by their affinity to complexation to organic and inorganic ligands and the changes of pH and salinity. Furthermore, the impact of salinity and pH on lability was also studied using laboratory simulation experiments. Interesting observations on the phenomena recorded include: (a) positive correlation between salinity and the very labilefraction of the metals, attributed to the formation of ion pairs and complexes of metals with chlorine ions; (b) increase of the presence of the less labile metal species by increasing pH; (c) relatively strong correlation of the dissolved organic carbon with the slowly labile and inert fractions of Pb and Zn, respectively.