Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River, Romania

Article Article scientifique Article Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River, Romania eng 2009 author Garcia Bravo Andrea 559843 author Loizeau Jean-Luc 0000-0002-0611-0388 23020 author Ancey Lydie 631333 author Ungureanu Viorel Gheorghe author Dominik Janusz 22088 66-75 10.1007/s11356-008-0057-5 0944-1344 http://link.springer.com/10.1007/s11356-008-0057-5 Background, aim and scope Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic environment showing a strong biomagnification effect along the food chain. The most common transfer path of Hg to humans is contaminated fish consumption. In severely exposed humans, Hg poisoning may lead to damage in the central nervous system. Thus, it is important to examine current and past contamination levels of Hg in aquatic milieu. The Olt River is the largest Romanian tributary of the Danube River. The use of Hg as an electrode in a chlor-alkali plant contributed to the contamination of the aquatic environment in the Rm Valcea region. The purpose of this study was to compare the current state of Hg contamination with the past contamination using a historical record obtained from a dated sediment core from one of the Olt River reservoirs (Babeni) located downstream from the chlor-alkali plant. To our knowledge, no published data on Hg contamination in this region are available. The Babeni Reservoir was selected for this study because it is situated downstream from the chlor-alkali plant, whilst the other reservoirs only retain the pollutants coming from the upstream part of the watershed. Preliminary analyses (unpublished) showed high Hg concentrations in the surface sediment of the Babeni Reservoir. One core was taken in the upstream Valcea Reservoir to provide a local background level of Hg concentrations in sediments. Results and discussion Sediment texture was uniform in the cores from both reservoirs. Laminated sediment structure, without any obvious discontinuities, was observed. Hg concentrations in the sediment core from the Valcea Reservoir were low and constant (0.01–0.08 mg/kg). In Babeni Reservoir sediments, Hg concentrations were very high in the deeper core section (up to 45 mg/kg in the longest core) and decreased to lower concentrations toward the top of the cores (1.3–2.4 mg/kg). This decrease probably reflects technological progress in control of emissions from the Hg-cell-based chlor-alkali industry. Two strong peaks could be distinguished in older sediments. The mean rate of sedimentation (5.9 cm/year) was calculated from the depth of the 137Cs Chernobyl peak. This was in good agreement with the sedimentation rate estimated at this site from a bathymetric study. Assuming a constant sedimentation rate, the two Hg peaks would reflect two contamination events in 1987 and 1991, respectively. However, it is also possible that the two peaks belong to the same contamination event in 1987 but were separated by a sediment layer richer in sand and silt. This layer had a low Hg concentration, which can be interpreted as a mass deposition event related to a major flood bringing Hg-free sediments. Conclusions Whilst the chlor-alkali plant partly switched to a cleaner technology in 1999, no obvious decrease of Hg concentrations was observed in recent decade. Results from the sediment core reflected the historical trend of Hg release from the chlor-alkali plant, revealed important contamination episodes and confirmed a legacy of contamination of Hg in recent sediments even if the concentrations of Hg decreased toward the surface due to a more efficient emission control. Recommendations and perspectives Although the Hg concentrations in Babeni Reservoir sediments were extremely high in the late eighties and they remain one order of magnitude higher in the surface sediments than in sediments from the upstream reservoir, little is known about the transfer of Hg to the biota and human population. Our initial measurements indicate the presence of monomethyl-Hg (MMHg) in pore water, but further studies are necessary to evaluate fluxes of MMHg at the sediment–water interface. Samples of fish and hair from various groups of the local population were recently collected to evaluate the potential hazard of Hg contamination to human health in the Rm Valcea region. ESTROM Historical record Hg Mercury Olt River Reservoir Sediment Dewey 550 Open Access - Licence nationale Springer Swiss National Science Foundation ESTROM CH 41 Département F.-A. Forel des sciences de l'environnement et de l'eau 153 false 944 ISE Eau 938 ISE Pôle Sciences 753 Limnology and Environmental Geology Environmental science and pollution research international 16 S1 de6d70cc-e56d-44f2-8a27-b0c164ae2260 Article (Published version) Public Garcia Bravo et al 2009 Environ Sci Poll Res.pdf 269052 application/pdf openAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département F.-A. Forel des sciences de l'environnement et de l'eau

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Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River, Romania	Environmental science and pollution research international			2009	747	285

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Ancey, Lydie