A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a biolumine... more A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN) 4 ]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.
Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles f... more Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles from water at 25 uC. A very good extraction efficiency was obtained with distribution coefficients as high as 500.
ABSTRACT This laboratory study demonstrated the effectiveness of UV-H2O2 on the disinfection of w... more ABSTRACT This laboratory study demonstrated the effectiveness of UV-H2O2 on the disinfection of water contaminated with microorganisms and organic matter. It was shown that UV-H2O2 has a higher efficiency than UV or hydrogen peroxide treatments applied alone. Performances were evaluated via microbiological and chemical parameters analyzed on both, water and biofilms (ATP, culturable and total bacteria, DOC and TOC). The optimization phases of the treatment confirmed a bacterial adaptation to H2O2 when applied alone. This adaptation was not observed in the case of UV-H2O2.
1] Barbel and gudgeon differ in their biology and ecology so that their bioturbation of streambed... more 1] Barbel and gudgeon differ in their biology and ecology so that their bioturbation of streambed sediments may have specific effects on the patch dynamics of the sediment transport. Using experimental streams, we tested this idea by measuring the impact of a naturally occurring biomass gradient of each fish on the (1) transport of gravel and sand at base flow; (2) sediment surface characteristics; and (3) critical shear stress (t C ) causing incipient gravel and sand motion during simulated floods. Corresponding to their biology and ecology, the fish specifically modified base flow transport and surface of the sediments. The greatest t C reduction for gravel/sand caused through these base flow fish activities was $50%/$60% in the barbel and $35%/$60% in the gudgeon experiment. We integrate these results into a conceptual framework that outlines the contribution of benthic animals to the patch dynamics of the gravel and sand transport in real streams.
We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotroph... more We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0-50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of ''small'' cocci, but filaments (>2 lm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization-detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the ''clear water phase'' was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).
A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a biolumine... more A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN) 4 ]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.
We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial ... more We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial grazing rates of heterotrophic and mixotrophic flagellates in the oligotrophic Lake Annecy (France). The comparison of bacterial grazing rates to bacterial production demonstrated a high transfer efficiency from the bacterial compartment up to flagellates. Per capita grazing rates ranged from 1.2U10 3 to 5.1U10 6 bacteria l 31 h 31 for heterotrophic flagellates, and from 4.8U10 6 to 6.8U10 7 bacteria l 31 h 31 for mixotrophic flagellates. The main bacterial grazers were Katablepharis within heterotrophic flagellates and Dinobryon within mixotrophic flagellates. Our results show that bacterial ingestion by a given flagellate taxon changed seasonally and could vary up to 30-fold. We also provide evidence that mixotrophic flagellates represent an important link in the flux of materials through planktonic food webs in Lake Annecy, suggesting that the introduction of mixotrophs within functional groups could improve our understanding of carbon flux pathways.
Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles f... more Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles from water at 25 uC. A very good extraction efficiency was obtained with distribution coefficients as high as 500.
A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a biolumine... more A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN) 4 ]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.
Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles f... more Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles from water at 25 uC. A very good extraction efficiency was obtained with distribution coefficients as high as 500.
ABSTRACT This laboratory study demonstrated the effectiveness of UV-H2O2 on the disinfection of w... more ABSTRACT This laboratory study demonstrated the effectiveness of UV-H2O2 on the disinfection of water contaminated with microorganisms and organic matter. It was shown that UV-H2O2 has a higher efficiency than UV or hydrogen peroxide treatments applied alone. Performances were evaluated via microbiological and chemical parameters analyzed on both, water and biofilms (ATP, culturable and total bacteria, DOC and TOC). The optimization phases of the treatment confirmed a bacterial adaptation to H2O2 when applied alone. This adaptation was not observed in the case of UV-H2O2.
1] Barbel and gudgeon differ in their biology and ecology so that their bioturbation of streambed... more 1] Barbel and gudgeon differ in their biology and ecology so that their bioturbation of streambed sediments may have specific effects on the patch dynamics of the sediment transport. Using experimental streams, we tested this idea by measuring the impact of a naturally occurring biomass gradient of each fish on the (1) transport of gravel and sand at base flow; (2) sediment surface characteristics; and (3) critical shear stress (t C ) causing incipient gravel and sand motion during simulated floods. Corresponding to their biology and ecology, the fish specifically modified base flow transport and surface of the sediments. The greatest t C reduction for gravel/sand caused through these base flow fish activities was $50%/$60% in the barbel and $35%/$60% in the gudgeon experiment. We integrate these results into a conceptual framework that outlines the contribution of benthic animals to the patch dynamics of the gravel and sand transport in real streams.
We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotroph... more We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0-50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of ''small'' cocci, but filaments (>2 lm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization-detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the ''clear water phase'' was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).
A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a biolumine... more A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN) 4 ]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.
We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial ... more We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial grazing rates of heterotrophic and mixotrophic flagellates in the oligotrophic Lake Annecy (France). The comparison of bacterial grazing rates to bacterial production demonstrated a high transfer efficiency from the bacterial compartment up to flagellates. Per capita grazing rates ranged from 1.2U10 3 to 5.1U10 6 bacteria l 31 h 31 for heterotrophic flagellates, and from 4.8U10 6 to 6.8U10 7 bacteria l 31 h 31 for mixotrophic flagellates. The main bacterial grazers were Katablepharis within heterotrophic flagellates and Dinobryon within mixotrophic flagellates. Our results show that bacterial ingestion by a given flagellate taxon changed seasonally and could vary up to 30-fold. We also provide evidence that mixotrophic flagellates represent an important link in the flux of materials through planktonic food webs in Lake Annecy, suggesting that the introduction of mixotrophs within functional groups could improve our understanding of carbon flux pathways.
Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles f... more Hydrophobic room-temperature ionic liquids were used to remove KNbO 3 and BaTiO 3 nanoparticles from water at 25 uC. A very good extraction efficiency was obtained with distribution coefficients as high as 500.
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Papers by Sylvie Viboud