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.     

Trace metal behaviour during summer in a stratified Mediterranean system: The Louros Estuary (Greece)

Trace metals (Al, Pb, Zn, Cr, Cu, Ni, Fe, Mn) were studied in waters (dissolved and particulate phases) and sediments of the Louros Estuary in the Amvrakikos Gulf, one of the most important European wetlands located at the NW coast of Greece. The study system is small, with a relatively narrow mixing zone, typical for Mediterranean estuaries. Particular emphasis was given to understanding the conditions prevailing in summer. During this season saline water intrudes the estuary along the river bed, despite the existing shallow sill, and forms a thin salt-wedge water mass, which occupies the near bottom layer with its thin end pointed upstream. Particulate metal concentrations within this saline bottom layer are considerably higher than in the riverine and marine sections of the estuary. Since the metal content of particles collected upstream is higher than that of the marine ones, there is a clear evidence that the salt-wedge acts as a ‘sink’ for most metals during the summer. Coexistance in the same zone of high dissolved metal concentrations indicate that loosely associated metals are desorbed from riverine particles, whereas newly formed suspended matter is deposited together with particles, transported by the river. The accumulation of metals in the near bottom layer affects directly their distribution in the sediments. The maximum concentrations of the metal fraction which is loosely held in sediments, are found primarily at the same site. The distribution of the ‘non-labile’ metal fraction of the sediments (particularly for Cu and Pb) is broadly constant throughout the estuary, confirming the absence of any significant natural or industrial point sources, at the lower part of the river. However, the analysis of sediment cores reveals an enrichment of this metal fraction at the top, near surface sections of the mouth area, indicating relatively recent pollution.     

Zinc in seawater and sediments of the Gulf of Elefsis,Greece

Dissolved and particulate Zn were measured in the sea water of the small Gulf of Elefsis, near Athens, Greece, for one year and as a function of depth. Particulate Zn was correlated with magnetic properties. Total Zn distribution in surface and subsurface sea bottom sediments and the partitioning of Zn among various sediment fractions were studied on a number of cores. The results for the Gulf of Elefsis are compared to recent results from other areas.     

Dissolved and particulate trace metals in a wetland of international importance: Lake Mikri Prespa,Greece

This paper reports the dissolved and particulate trace metal distributions in Lake Mikri Prespa, wetland of NW Greece. The concentrations of Cu, Pb, Zn, Cd, Al, Fe, Mn, Ni and Cr were determined in surface and hypolimnetic waters as well as in the inputs and the outflow. Trace metals were connected with two major populations of suspended particles, identified by using the recovery ratio for two different leaching reagents, namely 0.5 N HCl and 1:1 hot aqueous HNO₃. The first group is land derived entering the lake through runoff and plays a rather restricted role in its geochemistry. The second group which is more important includes authigenic carbonates, Fe and Mn hydroxides and oxides and organic rich particulates.