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Chokshi K, Kavanagh K, Khan I, Slaveykova VI, Sieber S. Surface displayed MerR increases mercury accumulation by green microalga Chlamydomonas reinhardtii. ENVIRONMENT INTERNATIONAL 2024; 189:108813. [PMID: 38878502 DOI: 10.1016/j.envint.2024.108813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/22/2024] [Accepted: 06/10/2024] [Indexed: 06/19/2024]
Abstract
Mercury is a highly toxic trace metal that can accumulate in aquatic ecosystems and when resent at high concentrations can pose risks to both aquatic life and humans consuming contaminated fish. This research explores the use of the metalloregulatory protein MerR, known for its high affinity and selectivity toward mercury, in a novel application. Through a cell surface engineering approach, MerR was displayed on cells of green alga Chlamydomonas reinhardtii. A hydroxyproline-rich GP1 protein was used as an anchor to construct the engineered strains GP1-MerR that expresses the fluorescent protein mVenus. The surface engineered GP1-MerR strain led up to five folds higher Hg2+ accumulation compared to the WT strain at concentration range from 10-9 to 10-7 M Hg2+. The binding of Hg2+ via MerR was specific and did not get significantly affected by major freshwater water quality variables such as Ca2+ and dissolved organic matter. The presence of other trace metals (Zn2+, Cu2+, Ni2+, Pb2+, Cd2+) in a same concentration range even resulted in 30-40 % increase in the accumulated Hg. Further, the engineered cells also demonstrated the ability to accumulate Hg2+ from the water extracts of the Hg-contaminated sediment samples. These results demonstrate a novel approach utilizing the cell surface display system in C. reinhardtii for its potential application in bioremediation.
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Affiliation(s)
- Kaumeel Chokshi
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Killian Kavanagh
- Department F.A. Forel for Environmental and Aquatic Sciences, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
| | - Imran Khan
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Vera I Slaveykova
- Department F.A. Forel for Environmental and Aquatic Sciences, Faculty of Sciences, University of Geneva, 1211 Geneva, Switzerland
| | - Simon Sieber
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland.
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Arrighi S, Franceschini F, Petrini R, Fornasaro S, Ghezzi L. The Legacy of Hg Contamination in a Past Mining Area (Tuscany, Italy): Hg Speciation and Health Risk Assessment. TOXICS 2024; 12:436. [PMID: 38922116 PMCID: PMC11209415 DOI: 10.3390/toxics12060436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 06/27/2024]
Abstract
The mercury cell manufacturing process, which has been extensively used in chlor-alkali plants to produce chlorine and caustic soda by electrolysis, represents a major source of Hg environmental pollution. At Saline di Volterra (Tuscany, Italy), solution mining by pumping water into halite deposits was applied to produce brines for a mercury-cell chlor-alkali plant. The Hg-contaminated, exhausted brines were pumped back at depth into the rock salt field in order to renew the available resources. Activities ceased in 1994, following the leakage dispersion of highly contaminated Hg(0)-bearing brines into the environment. The mercury content in the soil, measured during a survey conducted in 2000, reached 334 mg/kg, highlighting diffuse contamination in the floodplain. By 2009, the Hg concentration had generally decreased and was mostly confined to the topsoil layer. In order to evaluate the present Hg soil pollution, a geochemical survey was carried out in 2023, almost thirty years after the contamination event. The obtained data indicated the occurrence of legacy Hg, which reached 25.5 mg/kg in some soil samples. Speciation analysis for the most contaminated soil revealed that Hg(0) represented about 17.3% of the total Hg and that water-soluble and organic Hg fractions were negligible. These results suggest that the originally released metallic mercury has volatilized and likely oxidized, becoming practically immobile in the soil. A risk assessment, performed by applying Hg speciation analysis, indicated that the mercury in the soil does not carry a risk of non-cancerous effects for different exposure routes in case of subsequent use of the site and that the formerly contaminated area can now be converted into a leisure area.
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Affiliation(s)
- Simone Arrighi
- Department of Earth Science, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy; (S.A.); (R.P.); (L.G.)
| | - Fabrizio Franceschini
- Environmental Protection Agency of Tuscany (ARPAT), Via Vittorio Veneto, 56127 Pisa, Italy;
| | - Riccardo Petrini
- Department of Earth Science, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy; (S.A.); (R.P.); (L.G.)
| | - Silvia Fornasaro
- Department of Earth Science, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy; (S.A.); (R.P.); (L.G.)
| | - Lisa Ghezzi
- Department of Earth Science, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy; (S.A.); (R.P.); (L.G.)
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Ciucure CT, Geana EI, Arseni M, Ionete RE. Status of different anthropogenic organic pollutants accumulated in sediments from Olt River Basin, Romania: From distribution and sources to risk assessment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 886:163967. [PMID: 37164074 DOI: 10.1016/j.scitotenv.2023.163967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 04/30/2023] [Accepted: 05/01/2023] [Indexed: 05/12/2023]
Abstract
Some organic pollutants including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) have been banned from production worldwide, but due to their toxicity and persistence are still of concern. Also, unintentional by-products of combustion and industrial processes such as polycyclic aromatic hydrocarbons (PAHs), represent a permanent threat to the safety of the environment and the population. In this study, surface sediment samples from the middle and lower Olt River Basin (ORB), Romania, including dams, the main tributaries and the confluence with Danube River were collected during seasonal sampling campaigns in 2019 and analyzed for 13 OCPs, 12 PCBs and 15 PAHs in order to evaluate the impact of the main anthropogenic activities in the area (industrial activities and agriculture) and the ecological status of the ORB. The registered levels of OCPs, PCBs and PAHs in surface sediments varied from low to significantly polluted environments, indicating a clear spatial distribution between sites based on concentrations and congener profiles correlated with the influence of anthropogenic activities in the surrounding area. Based on some molecular diagnostic ratio and multivariate statistical analysis, both non-point sources and point sources deposition by surface runoff or atmospheric deposition were identified. Overall, the contamination profile of the study area reveals significant amounts of organochlorine compounds, resulting from the industrial production of chlorinated products, including lindane, but also from the long-term agricultural use of both HCHs and DDTs, more than half of the sites having levels that pose a potential risk for benthic organisms. Therefore, levels of POPs in the hot-spots sampling locations raise numerous concerns about the safety of the environment and the population in the region, requiring immediate actions.
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Affiliation(s)
- Corina Teodora Ciucure
- National Research and Development Institute for Cryogenics and Isotopic Technologies - ICSI, 240050 Ramnicu Valcea, Romania
| | - Elisabeta-Irina Geana
- National Research and Development Institute for Cryogenics and Isotopic Technologies - ICSI, 240050 Ramnicu Valcea, Romania.
| | - Maxim Arseni
- REXDAN Research Infrastructure, Faculty of Sciences and Environment, "Dunarea de Jos" University of Galati, 800201 Galati, Romania
| | - Roxana Elena Ionete
- National Research and Development Institute for Cryogenics and Isotopic Technologies - ICSI, 240050 Ramnicu Valcea, Romania
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Godyń I, Bodziony M, Grela A, Muszyński K, Pamuła J. Determination of Pollution and Environmental Risk Assessment of Stormwater and the Receiving River, Case Study of the Sudół River Catchment, Poland. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 20:504. [PMID: 36612823 PMCID: PMC9819663 DOI: 10.3390/ijerph20010504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/12/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
Changes in the land use of urban catchments and the discharge of stormwater to rivers are causing surface water pollution. Measurements were taken of the quality of discharged stormwater from two areas with different types of development: a residential area and a residential-commercial area, as well as the quality of the Sudół River water below the sewer outlets. The following indicators were studied: TSS, COD, N-NO3, N-NO2, TKN, TN, TP, Zn, Cu, Hg, HOI, and PAHs. The influence of land use on the magnitudes of flows in the river was modeled using the SCS-CN method and the Snyder Unit Hydrograph Model. The results showed an increase in sealing and a resulting increase in surface runoff. Concentrations of pollutants in stormwater and analysis of the potential amounts of loadings contributed by the analyzed stormwater outlets indicate that they may be responsible for the failure to meet environmental targets in the Sudół River. Environmental risk assessment shows that the aquatic ecosystem is at risk. A risk factor indicating a high risk of adverse environmental effects was determined for N-NO3, Zn, and Cu, among others.
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Araújo PRM, Biondi CM, do Nascimento CWA, da Silva FBV, da Silva WR, da Silva FL, de Melo Ferreira DK. Assessing the spatial distribution and ecologic and human health risks in mangrove soils polluted by Hg in northeastern Brazil. CHEMOSPHERE 2021; 266:129019. [PMID: 33272678 DOI: 10.1016/j.chemosphere.2020.129019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 11/06/2020] [Accepted: 11/15/2020] [Indexed: 06/12/2023]
Abstract
The emission of mercury (Hg) by chlor-alkali plants can pollute soils and sediments, posing risks to the environment and human health. Mangrove ecosystems are particularly sensitive to Hg contamination. Here, we studied the Hg spatial distribution and associated human and ecologic risks in mangrove soils impacted by a chlor-alkali plant. Sixty-six samples of superficial soils were collected from the mangrove of the Botafogo River, Brazil. Mercury contents were determined and ecological and human health risks were estimated from the soil. The Hg contents exceeded the local Hg background by up to 180 times, indicating the substantial anthropic contribution that occurred in the area. Mercury concentrations followed a gradient as a function of the distance from the chlor-alkali plant, with an apparent contribution from the estuary's hydrodynamic regime. The ecological risk was considered high in all the soils evaluated, while the daily average exposure for humans, considering multiple exposure routes to soil, is below the tolerable dose recommended by the World Health Organization (WHO). However, the risk to human health was unacceptable in the estuary section closest to the plant, mainly for children. Vapor inhalation was the main route for estimating non-carcinogenic risk. The results of this study indicate a severe scenario of Hg pollution with unacceptable risks to the ecosystem and the health of human beings, especially of the communities that live from fishery and shellfish colletion and are exposed daily to soils polluted by mercury. Studies on the organomercurial species in the food chain and Hg levels in individuals living close to the estuary are warranted. This research is an important reference in the world regarding the contamination of mangrove areas by Hg.
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Affiliation(s)
- Paula Renata Muniz Araújo
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
| | - Caroline Miranda Biondi
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
| | | | - Fernando Bruno Vieira da Silva
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
| | - William Ramos da Silva
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
| | - Franklone Lima da Silva
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
| | - Djennyfer Karolaine de Melo Ferreira
- Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
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Huang J, Hou M, Wang J, Teng X, Niu Y, Xu M, Chen Z. RuO2 nanoparticles decorate belt-like anatase TiO2 for highly efficient chlorine evolution. Electrochim Acta 2020. [DOI: 10.1016/j.electacta.2020.135878] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Rapin A, Rabiet M, Mourier B, Grybos M, Deluchat V. Sedimentary phosphorus accumulation and distribution in the continuum of three cascade dams (Creuse River, France). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:6526-6539. [PMID: 31873883 DOI: 10.1007/s11356-019-07184-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 11/25/2019] [Indexed: 06/10/2023]
Abstract
Dam construction leads to both sediment discontinuities and the creation of internal phosphorus (P) loads in reservoirs capable of supporting eutrophication. Today, majority of large rivers are dammed and numerous of these infrastructures are constructed in cascade. However, few studies focus on the cumulative effect of the presence of dam on sediment P mobility and bioavailability in downstream reservoirs and rivers parts or throughout the continuum. The influence of three cascade dams has been studied herein on the sedimentary P distribution in surface bed sediments along a 17-km fluvial continuum of the Creuse River (Massif Central, France). The sediments (17 samples) were analyzed for their physical (grain size, specific surface area) and chemical (pH, contents of P, Fe, Al, Ca, Mn, organic matter (OM), and P fractionation) characteristics. Results indicated an amount of P 3 to 7 times higher in dam sediments (1.59 ± 0.51 mgP/g DW) than in free-flowing river sections (0.27 ± 0.11 mgP/g DW). Unexpectedly, sedimentary TP content did not decrease from the first to the third reservoir. The spatial variations of sediment characteristics between river and reservoirs were correlated with the retention of particles sized under 200 μm within the reservoirs. In reservoir sediment, P was mainly associated with the ascorbate fraction (P associated with the redox-sensitive Fe/Mn precipitates). Inside each dam reservoir, longitudinal variations of the sedimentary P distribution were mainly due to the increase of amorphous Fe precipitate content accumulated in fine sediments toward the dam, as characterized by a low Fe-Asc/P-Asc molar ratio. In the river sections, P distribution (mainly associated with HCl and ascorbate fractions) was not significantly influenced by cascade dams.
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Affiliation(s)
- Anne Rapin
- PEIRENE EA 7500, Faculté des Sciences et Techniques, Université de Limoges, 123 Av. Albert Thomas, 87060, Limoges Cedex, France
| | - Marion Rabiet
- PEIRENE EA 7500, Faculté des Sciences et Techniques, Université de Limoges, 123 Av. Albert Thomas, 87060, Limoges Cedex, France.
| | - Brice Mourier
- PEIRENE EA 7500, Faculté des Sciences et Techniques, Université de Limoges, 123 Av. Albert Thomas, 87060, Limoges Cedex, France
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR5023 LEHNA, F-69518, Vaulx-en-Velin, France
| | - Malgorzata Grybos
- PEIRENE EA 7500, Faculté des Sciences et Techniques, Université de Limoges, 123 Av. Albert Thomas, 87060, Limoges Cedex, France
| | - Véronique Deluchat
- PEIRENE EA 7500, Faculté des Sciences et Techniques, Université de Limoges, 123 Av. Albert Thomas, 87060, Limoges Cedex, France
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Pollution and Health Risk Assessments of Potentially Toxic Elements in Soil and Sediment Samples in a Petrochemical Industry and Surrounding Area. Molecules 2019; 24:molecules24112139. [PMID: 31174302 PMCID: PMC6600396 DOI: 10.3390/molecules24112139] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/27/2019] [Accepted: 05/30/2019] [Indexed: 02/06/2023] Open
Abstract
The pollution state and health risk assessment of potentially toxic elements (PTE) in soil and sediment samples of the petrochemical industry and its surrounding area are evaluated in this study. The pseudo-total contents of Ba, Cd, Co, Cu, Cr, Mn, Ni, Pb, V, Zn, As, Hg, and Se were measured by inductively coupled plasma–optical emission spectrometry (ICP/OES) in analyzed samples. Instead of determining total content, we performed aqua regia of the samples. The silicate matrix remained, and the quantities of elements that are within the silicate matrix do not represent an environmental danger. The soils from the chlor–alkali plant are highly polluted by Hg (the enrichment factor values were above 6000), and by Cu, Cd, Pb, and Zn, while the sediment samples from the wastewater channel are polluted with Cr, Cd, and Hg. The measured element contents are used for calculating health risk criteria for a composite worker (a worker who is exposed, long-term, during the work day) and for residential people. Hg is the element that mainly contributes to non-carcinogenic risks within the petrochemical area. The highest value of total carcinogenic risk obtained in the sediment sample from the wastewater channel, and the metal that mostly contributes is Cr. The areas closest to the petrochemical industry have higher values of health risk criteria parameters and pollution indices. The areas that are located further to the north and south from the petrochemical industry are less burdened with the analyzed elements, which is significant because the closest city and village are situated in those directions.
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A clean and membrane-free chlor-alkali process with decoupled Cl 2 and H 2/NaOH production. Nat Commun 2018; 9:438. [PMID: 29382835 PMCID: PMC5789859 DOI: 10.1038/s41467-018-02877-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 01/05/2018] [Indexed: 11/18/2022] Open
Abstract
Existing chlor-alkali processes generally use asbestos, mercury or fluorine-containing ion-exchange membranes to separate the simultaneous chlorine production on the anode and hydrogen production on the cathode, and form sodium hydroxide in the electrolyte. Here, using the Na+ de-intercalation/intercalation of a Na0.44MnO2 electrode as a redox mediator, we decouple the chlor-alkali process into two independent steps: a H2 production step with the NaOH formation in the electrolyte and a Cl2 production step. The first step involves a cathodic H2 evolution reaction (H2O → H2) and an anodic Na+ de-intercalation reaction (Na0.44MnO2 → Na0.44−xMnO2), during which NaOH is produced in the electrolyte solution. The second step depends on a cathodic Na+ intercalation reaction (Na0.44−xMnO2 → Na0.44MnO2) and an anodic Cl2 production (Cl → Cl2). The cycle of the two steps provides a membrane-free process, which is potentially a promising direction for developing clean chlor-alkali technology. The chlor-alkali process is an important industrial process to make commodity chemicals; however, it usually requires the use of dangerous chemicals as membrane material. Here, the authors demonstrate clean, membrane-free chlor-alkali electrolysis, where chlorine evolution and hydrogen/sodium hydroxide production are completely decoupled.
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Kassegne AB, Okonkwo JO, Esho TB, Mekonnen KN, Malehase T, Asfaw SL. Distribution of total mercury in surface sediments and African catfish (Clarias gariepinus) from Akaki River catchment and Aba Samuel Reservoir, downstream to the mega-city Addis Ababa, Ethiopia. EMERGING CONTAMINANTS 2018; 4:32-39. [DOI: 10.1016/j.emcon.2018.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2023]
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Kassegne AB, Okonkwo JO, Esho TB, Mekonnen KN, Malehase T, Asfaw SL. Distribution of total mercury in surface sediments and African catfish (Clarias gariepinus) from Akaki River catchment and Aba Samuel Reservoir, downstream to the mega-city Addis Ababa, Ethiopia. EMERGING CONTAMINANTS 2018; 4:32-39. [DOI: https:/doi.org/10.1016/j.emcon.2018.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2023]
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Dranguet P, Le Faucheur S, Cosio C, Slaveykova VI. Influence of chemical speciation and biofilm composition on mercury accumulation by freshwater biofilms. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:38-49. [PMID: 27942649 DOI: 10.1039/c6em00493h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mercury (Hg) is a pollutant of high concern for aquatic systems due to the biomagnification of its methylated form along the food chain. However, in contrast to other metals, gaining knowledge of its bioavailable forms for aquatic microorganisms remains challenging, making Hg risk assessment difficult. Ubiquitous and sessile freshwater biofilms are well known to accumulate and to transform Hg present in their ambient environment. The present study thus aims to evaluate whether non-extractable (proxy of intracellular) Hg accumulated by biofilms could be a good indicator of Hg bioavailability for microorganisms in freshwater. To that end, the link between Hg concentration and speciation, as well as biofilm composition (percentage of abiotic, biotic, chlorophyll and phycocyanin-fractions and abundance of dsrA, gcs, merA and hgcA bacterial genes) and biofilm Hg accumulation was examined. The studied biofilms were grown on artificial substrata in four reservoirs along the Olt River (Romania), which was contaminated by Hg coming from chlor-alkali plant effluents. The 0.45 μm-filterable Hg concentrations in ambient waters were measured and inorganic IHg speciation was modelled. Biofilms were analyzed for their non-extractable IHg and methylmercury (MeHg) contents as well as for their composition. The non-extractable IHg content was related, but not significantly, to the concentration of total IHg (r2 = 0.88, p = 0.061) whereas a significant correlation was found with the predicted IHg concentration that is not bound to dissolved organic matter (r2 = 0.95, p = 0.027), despite its extremely low concentrations (10-25 M), showing a limitation of the thermodynamic Hg modelling to predict Hg bioavailability. The studied biofilms were different in biomass and composition and a principal component analysis showed that the non-extractable IHg content correlated with the abundance of the merA and hgcA genes, while MeHg accumulation was only linked with the abundance of the rRNA 16S gene. The present study suggests that non-extractable IHg concentrations in biofilms are a useful proxy of IHg bioavailable forms in waters whereas the hgcA and merA genes are good biomarkers of both biofilm IHg exposure and bioavailability.
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Affiliation(s)
- P Dranguet
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - S Le Faucheur
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - C Cosio
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
| | - V I Slaveykova
- University of Geneva, Faculty of Science, Earth and Environmental Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Uni Carl Vogt, 66 Bvd. Carl Vogt, CH-1211 Geneva, Switzerland.
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