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Digestive enzymes and gut morphometric parameters of threespine stickleback (Gasterosteus aculeatus): Influence of body size and temperature
No full textInternational audienceDetermining digestive enzyme activity is of potential interest to obtain and understand valuable information about fish digestive physiology, since digestion is an elementary process of fish metabolism. We described for the first time (i) three digestive enzymes: amylase, trypsin and intestinal alkaline phosphatase (IAP), and (ii) three gut morphometric parameters: relative gut length (RGL), relative gut mass (RGM) and Zihler's index (ZI) in threespine stickleback (Gasterosteus aculeatus), and we studied the effect of temperature and body size on these parameters. When mimicking seasonal variation in temperature, body size had no effect on digestive enzyme activity. The highest levels of amylase and trypsin activity were observed at 18°C, while the highest IAP activity was recorded at 20°C. When sticklebacks were exposed to three constant temperatures (16, 18 and 21°C), a temporal effect correlated to fish growth was observed with inverse evolution patterns between amylase activity and the activities of trypsin and IAP. Temperature (in both experiments) had no effect on morphometric parameters. However, a temporal variation was recorded for both RGM (in the second experiment) and ZI (in both experiments), and the later was correlated to fish body mass
Exposure assessment of pregnant women to Di(2-ethylhexyl) phthalate by reverse dosimetry : Variability in repeated spot sample
No full textInternational audiencePhthalates are a family of chemicals that can be found in a wide array of consumer products, and are suspected to induce reproductive and developmental toxicity. Among all phthalates, Di(2-ethylhexyl) phthalate (DEHP) have the strongest reproductive and developmental effects observed in animal studies. Large-scale human biomonitoring surveys typically gather biomarker measurements from single time points. For non-persistent compounds, such as DEHP, the biomarker levels are known to greatly vary within the same individual over a relatively short period of time. Thirty women from two countries (Spain and Norway) were followed over a week during the second trimester of pregnancy. A protocol was designed specifically to assess the intra-individual variability over the week. Two spot samples per day (first and last voids) and the pool of the urines collected over the week were analyzed. A toxicokinetic model proposed by Lorber et al., (2010) was applied to back-calculate the exposure levels to DEHP from the urinary metabolites concentrations. Individual data were collected from questionnaires and integrated in the model such as the bodyweight, the times of urination, time of meal and the time of sampling. This model that integrates all the DEHP metabolites has also the capability of considering the temporal variability of concentration. Our results showed a reduced variability of daily intake estimates compared to biomarkers measurement. Daily intake estimates were performed for first and last sample separately. Our study highlights the major influence of time data in reverse dosimetry and point out major information that should be obtained in future survey to better characterize non-persistent pollutant exposure
The influence of dust originating from carbon black nanopowders on the explosion characteristics of lean methane/air mixtures within a turbulent environment
No full textInternational audienceIndustrial requirements present some unique challenges that can be met only by the application of engineered nanomaterials (ENMs). The completion of risk assessments based on the knowledge of the change in the explosion severity of turbulent gas/air mixtures caused by the accidental dispersion of nanopowders is vital before integrating such materials into existing systems. In this work, known amounts of selected carbon black nanopowders were mixed with methane near the lower-flammability-limit (LFL) to form hybrid mixtures of variable dust concentration. Mixtures were ignited in a 23 L cylindrical combustion vessel that allowed the control of isotropic turbulence through specially designed fans. The particle size distribution, the explosion pressure history and the flame speed derived from high speed Schlieren cine photographs, were measured. The influence of dispersed amounts of nanopowders on explosion severity was investigated by comparing the results with those obtained for pure methane-air explosions. Results indicated that the release of a relatively low mass of nanopowder into methane-air mixtures resulted in a more severe explosion than that of a higher amount. Also, despite the very low content of volatiles in the selected nanopowders, a hybrid mixture can be ignitable at an equivalence ratio well below the LFL of the gas. However this ignitability was shown to be related to the agglomeration state of powder in the dispersion phase, indicating that as the mean particle size decreases, a hybrid mixture with an extremely low content of flammable gas could be ignitable. From a risk assessment point of view, these results may have great significance for specific industrial processes aiming to utilise ENMs
Endocrine disrupting properties: how far and consistent they are considered deriving Water Framework Directive Environmental Quality Standards ? A case study tackling French and EU EQS values
No full textInternational audienceThe concern raised by endocrine disrupting properties of chemicals should be tackled in diverse regulatory frameworks, among which the Water Framework Directive Common Implementation Strategy (WFD CIS). In this context, endocrine disruption (ED) is quoted several times as an issue for deriving water quality thresholds in the European Commission Technical Guidance for Deriving Environmental Quality Standards (TGD EQS). However, even if this guidance introduces ED properties as a reason for growing concern, it does not properly recommend any specific methodological approach to consider these properties while deriving EQS values. In order to evaluate the usefulness of such a recommendation and the extent to which it should be implemented, a state of the art of how ED properties are currently been taken on board in the EQSs already derived at EU and national level was made. To begin with, the work consisted in carrying out an inventory of substances for which an EQS had been derived and a factsheet describing the reasoning behind value was available. These substances made up the universe of 178 substances on which further work was led. Then, an analysis was made of these substances EQSs derivation to categorise them according to how ED properties where reported and taken on board if necessary for protection of wildlife and human health. This work led to 4 groups of substances. Group 1 contains substances whose EQS values do not consider ED effects, and which need to be reassessed as a matter of priority. Substances for which EQS derivation has considered ED effects but whose rationale does not clearly explain this are grouped together in Group 2 and should be verified. Group 3 corresponds to substances whose ED characteristics have been considered by an additional safety factor and / or a study that covers ED effects. Group 4 contains all substances that have no ED effects demonstrated from now on. No action is required for these last two categories. This state of play and categorisation work made it possible to prioritise substances for which EQS should be updated first as regards their ED potential. Also, this work gives more insight in how to derive EQSs as regards ED potential in order to further propose recommendations for a harmonisation of the methodology in the future
Rôle des aérosols dans l’environnement et l’exposition des personnes : apport de la métrologie
No full textA European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
No full textInternational audienceThis paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe
La surveillance des particules ultrafines en France
No full textInternational audienceMeasurement of ultrafine particles (UFP) has been developing recently in the air quality monitoring networks in France. These particles are very small in size (<100 nm) and low in mass, but represent significant health effects. This article presents different results of short and long-term measurement campaigns which have been carried out in different environments (urban, traffic and industry) and the comparison of the number concentrations and size distribution at the national level. In addition, we show how UFPs measurements can be used to identify local sources and explain atmospheric phenomena.La mesure des particules ultrafines (PUF) se développe de plus en plus dans les réseaux de surveillance de la qualité de l’air en France. Ces particules sont très petites en taille (<100 nm) et faibles en masse, mais représentent des effets sanitaires importants. Cet article présente différents résultats issus de campagnes de mesure de courte et longue durée qui ont été réalisées dans différents environnements (urbain, trafic et industrie), et une comparaison des concentrations en nombre et de la distribution en taille au niveau national. De plus, nous montrons comment la mesure de PUF peut permettre d’identifier des sources locales et contribuer à expliquer certains phénomènes atmosphériques
Nanopowders explosion : influence of the dispersion characteristics
No full textInternational audienceWith the publication of NFPA 68 (2013); a major change is in progress in venting area calculation methods for gas explosions. Old methods referring to the Kg parameter proved to be inappropriate for real applications. The present work provides new data to correlate real gas concentration and initial turbulence conditions to flame propagation and explosion overpressure during a vented gas explosion. Explosion tests were performed in a 4 m3 rectangular chamber equipped with transparent walls and vented (0.49 m2 square vent) on one side. The chamber is filled with a turbulent or quiescent hydrogen-air mixture with a purposely built injection system that allows to vary the turbulence intensity and the length scale. Gas concentration and turbulence parameters are measured with concentration gauges and Pitot probes distributed in the chamber (Duclos, 2017). Then the flame propagation is fully characterized with high speed video and explosion overpressure is measured inside and outside the chamber. The paper presents the parametric study performed by varying the initial turbulence and focuses on its influence on the inside explosion overpressure. Then physics of vented gas explosion is discussed, results are compared to developing phenomenological model
Acoustic monitoring of a thermo-mechanical test simulating withdrawal in a gas storage salt cavern
No full textInternational audienceNatural gas storage in salt caverns requires fast injection / withdrawal cycles due to the increasing dynamics of the energy market. High rates induce rapid changes in the internal pressure of the stored gas causing important temperature changes susceptible to damage the rock salt mass. To experimentally observe this, the Starfish project aimed to characterize the damage caused by purely thermal stresses at the surface of a large bloc of rock in the salt mine of Varangéville (France). The objective was to determine the type of failure mechanism involved with repeated cooling stages. Since the salt is favourable to the generation of Acoustic Emissions (AE) and the propagation of stress waves, acoustic monitoring was chosen as one of the methods to follow the impact of the salt cooling. In addition to thermal and mechanical sensors, an acoustic monitoring device consisting of 16 ultrasonic sensors was installed on the free surface and in boreholes. It enabled to record and locate a large number of AE (58,426) located with good accuracy (2.5 cm). Those AE can be correlated to the evolution of salt fracturing. Acoustic activity is very intense at the start of each cooling cycle, then decreases with time to reach a very low level (background) after about 15 days. The average localisation depth reached by the AE is about 90 cm during the first cooling period. For subsequent cooling cycles, this depth is limited to 74 cm. These results show that the first cooling period is decisive, as it contains the strongest and deepest acoustic emissions