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Heterogeneous equilibria of Hg and Pb from laboratory to natural environment

The concentrations of lead and mercury in natural waters may be controlled by an equilibrium solubility of slightly soluble phases, by cation exchange mechanism or by adsorption processes. For better understanding the conditions in carbonate containing natural waters we have performed laboratory experiments. Basic thermodynamic data on lead and mercury solubility and speciation were performed [1, 2, 3]. Reported results have shown that studied Pb and Hg carbonates are rather soluble and that they cannot explain low concentrations found in natural waters. The next step was to study adsorption of trace metals, using model adsorbents and natural estuarine- and sea- waters [4, 5]. Natural concentrations of Hg were measured in water of unpolluted Krka estuary and processes affecting the fate of Hg were discussed [6, 7]. There were also some measurements of total Hg and of MeHg measured in very polluted Kaštela Bay [8]. Recent measurements of toxic elements (Pb, Cd, Cu, Zn and Mn) were performed in Kosovo rivers, belonging to three different watersheds. These measurements [9] are used to locate polluted regions and to highlight locations where intensive monitoring and possibly remediation should be performed. The last research could help to establish monitoring network and water management in Kosovo. References [1] Bilinski, H., Schindler, P., Solubility and equilibrium constants of lead in carbonate solutions (25°C, I=0.3 moldm-3), Geochim. Cosmochim. Acta, 46, (1982) 921-928. [2] Bilinski, H., Marković, M., Gessner, M., Solubility and equilibrium constants of Mercury (II) in carbonate solutions, I=0.5 moldm-3, 25°C, Inorg. Chem., 19, (1980) 3440-3443. [3] Bilinski, H., Huston, R., Stumm, W., Determination of the stability constants of some hydroxo and carbonato complexes of Pb(II), Cu(II), Cd(II) and Zn(II) in dilute solutions by anodic stripping voltammetry and differential pulse polarography, Anal. Chim. Acta, 84, (1976) 157-164. [4] Bilinski, H., Kozar, S, Plavšić, M., Kwokal, Ž., Branica, M., Trace metal adsorption on inorganic solid phases under estuarine conditions, Mar. Chem., 32, (1991) 225-233. [5] Kozar, S., Bilinski, H., Branica, M., Adsorption of lead and cadmium ions on calcite in the Krka estuary, Mar. Chem., 40, (1992) 215-230. [6] Bilinski, H., Kwokal, Ž., Branica, M., Processes affecting the fate of mercury in the Krka River estuary, Wat. Res., 26, (1992) 1234-1253. [7] Bilinski, H., Kwokal, Ž., Plavšić, M., Wrischer, M., Branica, M., Mercury distribution in the water column of the stratified Krka River estuary (Croatia): Importance of natural organic matter and of strong winds, Wat. Res., 34, (2000), 2001-2010. [8] Kwokal, Ž., Frančišković-Bilinski, S., Bilinski, H., Branica, M., A comparison of anthropogenic mercury pollution in Kaštela Bay (Croatia) with pristine estuaries in Öre (Sweden) and Krka (Croatia), Mar. Poll. Bull., 44, (2002), 1150-1155. [9] Gashi, F., Frančišković-Bilinski, S., Bilinski, H., Troni, N., Bacaj, M., Jusufi, F., Establishing of monitoring network on Kosovo rivers: preliminary measurements on the four main rivers (Drini i Bardhë, Morava e Binqës, Lepenc and Sitnica), Env. Monit. Assess., in review process.

lead ; mercury ; carbonates ; equilibrium solubility ; adsorption

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