Biological oxidation of arsenite: batch reactor experiments in presence of kutnahorite and chabazite

Arsenic represents a threat to all living organisms due to its toxicity which depends on its speciation. This element is carcinogenic, teratogenic and is certainly one of the most important contaminants affecting millions of people around the world. Abiotic and biotic processes control its speciation and distribution in the environment. We have previously shown that a new bacterial strain named ULPAs1 performed oxidation of As(III) (1.33 mM) to As(V) in batch cultures. In order to develop new methods to remove arsenic from contaminated effluents or waste, by bacterial oxidation of As(III) to As(V) followed by its sorption, the conservation of oxidative properties of ULPAs1 was investigated when cultivated in batch reactors in the presence of two solid phases, chabazite and kutnahorite, already used as microorganisms immobilizing materials in biological remediation processes. In parallel, the retention efficiency of these solid phases toward arsenic ions and particularly arsenate was studied. Pure quartz sand was used as a reference material. Kutnahorite efficiently sorbed As(V), chabazite alone performed As(III) oxidation and pure quartz sand did not sorb arsenic at all. The arsenite oxidative properties of ULPAs1 were conserved when cultivated in the presence of quartz or chabazite.     

Is PCBs concentration variability between and within freshwater fish species explained by their contamination pathways?

Many chemical, physiological, and trophic factors are known to affect bioaccumulation of polychlorinated biphenyls (PCBs) in biota. Understanding the primary factors affecting fish contamination is critical for predicting and assessing risks to upper-trophic level consumers, including humans. Here we identify PCB contamination pathways that could explain within- and between-species variability in fish concentration levels. Three freshwater river fish species (barbel, chub and bream) were sampled at three sites along the Rhone River (France) where fish consumption is partially prohibited because of PCB levels exceeding the European health-based benchmark. The trophic position was assessed using an innovative approach based on stable isotope analyses and Bayesian inference, which takes into account both isotope data variability and parameter uncertainty. The effect of foraging habitat on fish contamination was addressed using stable isotope mixing models. The fish trophic position and PCB concentrations were found to be unrelated while the exploitation of sediment detrital carbon as a food source appeared to be a critical factor affecting fish contamination. Fish length, PCB concentration of the sediment, and individual fish foraging habitat (exploitation of detrital versus planktonic carbon sources) explained 80% of within- and between-species variability observed in PCB concentrations. These results, obtained for species that have overlapping TPs and exploit different carbon sources, reveal that the important factor in fish PCB contamination is not only what fish consume, but also and essentially the feeding location.