title: Environmental quality assessment of reservoirs impacted by Hg from chlor-alkali technologies: case study of a recovery.
abstract: Mercury (Hg) pollution legacy of chlor-alkali plants will be an important issue in the next decades with the planned phase out of Hg-based electrodes by 2025 within the Minamata convention. In such a context, the present study aimed to examine the extent of Hg contamination in the reservoirs surrounding the Oltchim plant and to evaluate the possible improvement of the environmental quality since the closure of its chlor-alkali unit. This plant is the largest chlor-alkali plant in Romania, which partly switched to Hg-free technology in 1999 and definitely stopped the use of Hg electrolysis in May 2012. Total Hg (THg) and methylmercury (CH3Hg) concentrations were found to decrease in the surface waters and sediments of the reservoirs receiving the effluents of the chlor-alkali platform since the closure of Hg units. Hence, calculated risk quotients (RQ) indicated no adverse effect of Hg for aquatic organisms from the ambient water exposure. RQ of Hg in sediments were mostly all higher than 1, showing important risks for benthic organisms. However, ecotoxicity testing of water and sediments suggest possible impact of other contaminants and their mixtures. Hg hotspots were found in soils around the platform with RQ values much higher than 1. Finally, THg and CH3Hg concentrations in fish were below the food safety limit set by the WHO, which contrasts with previous measurements made in 2007 revealing that 92 % of the studied fish were of high risk of consumption. Discontinuing the use of Hg electrodes greatly improved the surrounding environment of chlor-alkali plants within the following years and led to the decrease environmental exposure to Hg through fish consumption. However, sediment and soil still remained highly contaminated and problematic for the river reservoir management. The results of this ecological risk assessment study have important implications for the evaluation of the benefits as well as limits of the Minamata Convention implementation.
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland. severine.lefaucheur@unige.ch.
authors: Séverine
authors: S
authors: Le Faucheur
authors: National Institute for Research and Development of Marine Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053, Bucharest, Romania.
authors: Dan
authors: D
authors: Vasiliu
authors: National Institute for Research and Development of Marine Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053, Bucharest, Romania.
authors: Irina
authors: I
authors: Catianis
authors: National Institute for Research and Development of Marine Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053, Bucharest, Romania.
authors: Mariana
authors: M
authors: Zazu
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland.
authors: Perrine
authors: P
authors: Dranguet
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland.
authors: Rebecca
authors: R
authors: Beauvais-Flück
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland.
authors: Jean-Luc
authors: JL
authors: Loizeau
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland.
authors: Claudia
authors: C
authors: Cosio
authors: National Institute for Research and Development of Marine Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053, Bucharest, Romania.
authors: Costin
authors: C
authors: Ungureanu
authors: National Institute for Research and Development of Marine Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053, Bucharest, Romania.
authors: Viorel Gheorghe
authors: VG
authors: Ungureanu
authors: University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Institute F.-A. Forel, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, 1211, Geneva 4, Switzerland. vera.slaveykova@unige.ch.
authors: Vera I
authors: VI
authors: Slaveykova
mesh_terms: D000468:Alkalies; D000818:Animals; D059001:Aquatic Organisms; D004435:Eating; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005399:Fishes; D019015:Geologic Sediments; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008628:Mercury / Q000633:toxicity*; D008767:Methylmercury Compounds / Q000633:toxicity; D045483:Rivers; D012383:Romania; D012987:Soil / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D000468:Alkalies; D008767:Methylmercury Compounds; D012987:Soil; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Chlor-alkali plant; Legacy pollution; Mercury; Reservoirs; Risk assessment