Christophe Benninghoff

Publications (3)5.22 Total impact

• Article: Confirmation of elemental sulfur toxicity in the Microtox® assay during organic extracts assessment of freshwater sediments

  Michel Pardos, Christophe Benninghoff, Richard L. Thomas, Sophal Khim-Heang
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  ABSTRACT: Recent literature indicates that the elemental sulfur occurring in organic extracts of sediment samples can be toxic to the bacterium Vibrio fischeri, used in standard Microtox® bioassays. This observation was tested by means of the solvent extraction of 14 freshwater sediment samples from rivers tributary to Lake Geneva (Switzerland–France), measuring both Microtox toxicity and the elemental sulfur concentration of the extracts. Aliquots of these sediment extracts were further treated to remove the sulfur by adding acid-activated copper to the crude extracts; for 18 h in one case, and for 116 h in an other. The results were a significant amount of the observed acute toxicity in the Microtox assay of 81% of sample extracts (n = 42, crude and after cleanup) was due to elemental sulfur, and despite a median decrease of 99.1% of elemental sulfur in the extracts subject to a 116-h cleanup, sulfur toxicity was not completely excluded for 57% (8/14) of the samples. Clearly, the Microtox methodology needs to be amended to more accurately assess the potential impact of organic pollutants in sediments when solvent extracts are used. This will help to cut down on costly and unnecessary remedial actions.
  Environmental Toxicology and Chemistry 11/2009; 18(2):188 - 193. · 2.81 Impact Factor
• Article: Photosynthetic and population growth response of the test alga Selenastrum capricornutum Printz to zinc, cadmium and suspended sediment elutriates

  Michel Pardos, Christophe Benninghoff, Richard L. Thomas
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  ABSTRACT: Short-term 14C-fixation (4 h) Selenastrum capricornutum algal toxicity tests were conducted with Cd (n=8), Zn (n=9) and suspended sediment aqueous elutriates (n=28) and the results were compared to those obtained in a 48 h population growth test. In order to provide more realistic experimental conditions, toxicity tests were carried out in prefiltered nutrient-spiked Lake Geneva water. The population growth inhibition test was significantly more sensitive than the14 C-fixation test for Cd (median EC50-4h and EC50-48h values of 600 and 118 µg L-1, respectively) whereas no significant difference was measured for Zn toxicity (median EC50-4h and EC50-48h values of 97 and 96 µg L-1, respectively). With suspended sediment aqueous elutriates, the relative sensitivity of the two different end points is sample dependent, with ratios of the EC25 for the14 C-fixation: population growth test ranging from <0.26 to >53.3. Elutriate toxicity shows no apparent relationship between the acute and chronic test, indicating that population growth inhibition cannot be derived directly or predicted from14 C-fixation. Both tests with their specific advantages and limitations provide valuable complementary information to measure the impact of single toxicants or complex mixtures on aquatic plants.
  Journal of Applied Phycology 04/1998; 10(2):145-151. · 2.41 Impact Factor
• Article: The impact of a sewage treatment plant's effluent on sediment quality in a small bay in Lake Geneva (Switzerland–France). Part 1: Spatial distribution of contaminants and the potential for biological impacts

  Michel Pardos, Christophe Benninghoff, Luis Felippe de Alencastro, Walter Wildi
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  ABSTRACT: The purpose of this study was to assess the quality of bottom sediment collected in the Bay of Vidy (Lake Geneva, Switzerland) which receives sewage treatment plant discharges from the city of Lausanne and its surroundings. Thirty-eight sediment samples were taken, forming a dense network. Samples of that portion of the sediment that has accumulated since phosphorus removal (via iron precipitation) was instituted at the plant in 1971 were analysed for heavy metals, nutrients and organic micropollutants and subjected to Microtox toxicity evaluation (organic extract). The distribution patterns of contaminants, as well as principal components analysis, demonstrated that the sewage treatment plant's effluent is the main source of local sediment contamination. This was not supported by the Microtox results. In close proximity to the outlet pipe of the sewage treatment plant, contaminants showed very high median concentrations for virtually all the parameters measured, at levels above those believed to elicit biological responses. A major environmental impact is clearly occurring in this coastal region of the lake and remediation of this situation is believed to be important in order to protect the Lake Geneva ecosystem.