Examinando por Autor "Kalman, Judit"

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Biodynamic modelling of the bioaccumulation of trace metals (Ag, As and Zn) by an infaunal estuarine invertebrate, the clam Scrobicularia plana
(2014) Kalman, Judit; Smith, Brian D.; Bury, Nic R.; Rainbow, Phil S.
Biodynamic modelling was used to investigate the uptake and accumulation of three trace metals (Ag, As, Zn) by the deposit feeding estuarine bivalve mollusc Scrobicularia plana. Radioactive labelling techniques were used to quantify the rates of trace metal uptake (and subsequent elimination) from water and sediment diet. The uptake rate constant from solution (±SE) was greatest for Ag (3.954±0.375 l g(-1) d(-1)) followed by As (0.807±0.129 l g(-1) d(-1)) and Zn (0.103±0.016 l g(-1) d(-1)). Assimilation efficiencies from ingested sediment were 40.2±1.3% (Ag), 31.7±1.0% (Zn) and 25.3±0.9% (As). Efflux rate constants after exposure to metals in the solution or sediment fell in the range of 0.014-0.060 d(-1). By incorporating these physiological parameters into biodynamic models, our results showed that dissolved metal is the predominant source of accumulated Ag, As and Zn in S. plana, accounting for 66-99%, 50-97% and 52-98% of total accumulation of Ag, As and Zn, respectively, under different field exposure conditions. In general, model-predicted steady state concentrations of Ag, As and Zn matched well with those observed in clams collected in SW England estuaries. Our findings highlight the potential of biodynamic modelling to predict Ag, As and Zn accumulation in S. plana, taking into account specific dissolved and sediment concentrations of the metals at a particular field site, together with local water and sediment geochemistries.
Differences in Engineered Nanoparticle Surface Physicochemistry Revealed by Investigation of Changes in Copper Bioavailability During Sorption to Nanoparticles in the Aqueous Phase
(2019) Patsiou, Danae; Kalman, Judit; Fernandes, Teresa; Henry, Ted
Sorption of chemical substances to nanoparticles (NPs) in the aqueous phase strongly influences NP physicochemisty, and investigations of these complex interactions can provide important insights into the environmental fate of NPs. The objective of the present study was to use differences in copper (Cu) bioavailability to investigate aqueous-phase sorption with NPs that had different physicochemical characteristics (silicon [Si], perovskite, and titanium dioxide NPs [TiO2 NPs]). Sorption of Cu with NPs was assessed by the presence of adsorbent in water and onto the NP surface after ultracentrifugation, and by changes in Cu bioavailability under static conditions during exposure of larval zebrafish, as well as under conditions of continuous agitation during exposure of the alga Chlorella vulgaris. The presence of TiO2 NPs reduced total Cu in the water column and Cu bioavailability (measured by growth inhibition, mortality, and metallothionein 2 gene expression), confirming Cu sorption to TiO2 NPs. Nanoparticle surface area was the most important factor that affected Cu sorption, as indicated by less bioavailable Cu in the presence of smaller TiO2 NPs. The surface area effect was consistent regardless of exposure conditions (alga, continuous agitation; zebrafish, static water) and was further supported by the fact that the lowest total Cu concentration in the water column was found in the presence of the smallest NP. The results differed with other NP types, for example, silicon NPs, in which Cu sorption was indicated by analytical chemistry, but sorption was not sufficient to significantly alter Cu bioavailability. The bioavailability tests did not indicate Cu sorption with perovskite NPs. The results demonstrate that surface area critically influences sorption, that Cu sorption as measured by bioavailability is not affected by agitation or static conditions, and that Cu sorption differs among types of NPs, indicating differences in their surface physicochemistry.
Investigating the Impact of Manufacturing Processes on the Ecotoxicity of Carbon Nanofibers: A Multi–Aquatic Species Comparison
(2019) Barrick, Andrew; Chatel, Amelie; Manier, Nicolas; Kalman, Judit; Navas, Jose M.; Moneyrac, Catherine
Manufactured nanomaterial production is outpacing the ability to investigate environmental hazard using current regulatory paradigms, causing a backlog of materials requiring testing. To ameliorate this issue, regulatory bodies have proposed integrating safety into the production of novel nanomaterials, allowing for hazards to be identified early in development rather than aftermarket release. In addition, there is a growing interest in short-term ecotoxicity testing to rapidly identify environmental hazards. In this sense, the present study investigated 3 carbon nanofibers (CNFs), created with different production methods, using short-term in vitro and in vivo exposures on fish cell lines, mussel hemocytes, crustacea, and algae. The present study investigated if differences in ecotoxicity hazard between the CNFs could be identified and, if so, which product could be considered less hazardous. A major challenge in assessing the potential hazards posed by manufactured nanomaterials is standardizing the preparation for testing. Standardized operating protocols have been proposed using protein to facilitate the preparation of stable stock suspension, which is not environmentally representative. As such, the study also assessed the potential impacts these standardized protocols (with or without the use of protein) could have on the interpretation of environmental hazard. The results demonstrated that there were clear differences between the 3 CNFs and that the dispersion protocol influenced the interpretation of hazard, demonstrating a need for caution when interpreting ecotoxicity in a regulatory context.