Éditeur(s) : Université Bretagne Ouest
Résumé : This work deals with the fishing effects on the diversity dynamics of demersal fish communities, focusing on the biotic interactions. Multispecies indices are used in order to characterize the demersal fish community dynamics of the Bay of Biscay and of the Gulf of Lions. These are the diversity indices, the temporal variability of the total biomass and of the slope of the number size spectra and the slope of the species-area curves (spatial segregation). The yearly bottom trawl surveys EVHOE, CHALIST and MEDITS, carried out in these two areas since 1983 by IFREMER for the stocks assessment provide the data. The differences between areas are related to a fishing index (mean value of the annual landings of demersal fish per surface area). Other areas are included in the analysis when the index values are available from the published literature (North Sea, Scotian Shelf, Kenya, French Guyana). It is argued from the diversity indices analysis that the Gulf of Lions community is more diverse and less disturbed than the Bay of Biscay one. This result is not consistent with a fishing effect but with biogeography. The total biomass variability and the slope variability of size spectra are higher in the most harvested areas than in the least ones. On the contrary, the species-area slope is the lowest in the most harvested areas. Theoretically, biotic interactions decrease the total biomass variability and the spectra slope variability because of compensations and increase the species area slope because of competitive exclusion. It is concluded that harvesting alters biotic interactions and favour local coexistence by decreasing competitive exclusion. The species diversity maintenance depends on competitive exclusion. Hence, biodiversity is threatened not only by a direct fishing effect but also by a dynamics alteration.
Ce mémoire aborde le problème de l'impact de l'exploitation par la pêche sur la dynamique de diversité des peuplements de poissons démersaux. Les effets de la pêche sur le rôle des interactions biotiques entre espèces dans la dynamique des peuplements sont plus particulièrement analysés à l'aide de descripteurs multispécifiques. Les descripteurs utilisés sont les indices de diversité, la variabilité temporelle de la biomasse totale et de la pente multispécifique du spectre de poids et la pente des droites d'accumulation d'espèces mesurant la ségrégation spatiale. Les valeurs de ces indices sont calculées à partir des données de campagnes annuelles de chalutage de fond EVHOE, CHALIST et MEDITS, menées par l'IFREMER depuis 1983 pour l'évaluation des ressources halieutiques dans le golfe de Gascogne et dans le golfe du Lion. Les différences de caractéristiques de dynamique entre les deux peuplements révélées par ces descripteurs sont mises en relation avec un indice d'exploitation (valeur moyenne des débarquements annuels, divisée par la surface du plateau de la région concernée). D'autres régions ont été intégrées dans cette analyse lorsque les valeurs des indicateurs étaient disponibles dans la littérature (Mer du Nord, plateau de Nouvelle-Ecosse, Kenya et Guyane Française). Les indices de diversité utilisés permettent de mettre en évidence que le peuplement du golfe du Lion est plus diversifié et moins soumis à perturbations que celui du golfe de Gascogne. Ces caractéristiques semblent dues à l'histoire biogéographique de ces deux régions et non à un effet de la pêche. La variabilité de la biomasse totale et celle de la pente du spectre multispécifique augmentent depuis les régions les moins exploitées vers les plus exploitées. A l'inverse, la ségrégation spatiale diminue. En théorie, les interactions entre espèces diminuent la variabilité temporelle de la biomasse totale et de la pente du spectre multispécifique, à cause de compensations entre espèces, et augmentent la ségrégation spatiale par exclusion compétitive. L'interprétation donnée des résultats obtenus est ainsi une altération des interactions entre les espèces par l'exploitation. En prélevant de la biomasse, l'exploitation augmente la disponibilité des ressources pour les individus non pêchés. En conséquence, l'exclusion compétitive diminue et la coexistence locale des individus est facilitée. A long terme, la diversité est donc menacée, non seulement par raréfaction des espèces prélevées par l'exploitation mais aussi parce que les interactions sont altérées et que le maintien de la diversité en dépend pour partie.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2000/these-6670.pdf
http://archimer.ifremer.fr/doc/00000/6670/

Éditeur(s) : Soc Francaise D Ichtyologie
Résumé : This work deals with the fishing effects on the diversity dynamics of demersal fish communities, focusing on the biotic interactions. Multispecies indices were used in order to characterise the demersal fish community dynamics of the Bay of Biscay and of the Gulf of Lions. These are the diversity indices, the temporal variability of the total biomass and of the slope of the number size spectra and the slope of the species-area curves (spatial segregation). The data were provided by yearly bottom trawl surveys EVHOE, CHALIST and MEDITS carried out in these two areas since 1983 by IFREMER for stock assessment. The differences between areas are related to a fishing index (mean value of the annual landings of demersal fish per surface area). Other areas are included in the analysis when the index values are available from the published literature (North Sea, Scotian Shelf, Kenya, French Guyana). From the diversity indices analysis it is argued that the Gulf of Lions community is more diverse and less disturbed than the Bay of Biscay one. This result is not consistent with a fishing effect. It is interpreted as a biogeography pattern. The total biomass variability and the slope variability of size spectra are higher in the most harvested areas than in the least ones. On the contrary, the species-area slope is the lowest in the most harvested areas. Theoretically, biotic interactions decrease the total biomass variability and the spectra slope variability because of compensations, and increase the species area slope because of competitive exclusion. It is concluded that harvesting alters biotic interactions and favours local coexistence by decreasing competitive exclusion. The species diversity maintenance depends on competitive exclusion. Hence, biodiversity is threatened not only by a direct fishing effect but also by a dynamics alteration.
Ce mémoire aborde le problème de l'impact de l'exploitation par la pêche sur la dynamique de diversité des peuplements de poissons démersaux. Les effets de la pêche sur le rôle des interactions biotiques entre espèces dans la dynamique des peuplements sont plus particulièrement analysés à l'aide de descripteurs multispécifiques. Les descripteurs utilisés sont les indices de diversité, la variabilité temporelle de la biomasse totale et de la pente multispécifique du spectre de poids et la pente des droites d'accumulation d'espèces mesurant la ségrégation spatiale. Les valeurs de ces indices sont calculées à partir des données de campagnes annuelles de chalutage de fond EVHOE, CHALIST et MEDITS, menées par l'IFREMER depuis 1983 pour évaluer les ressources halieutiques dans le golfe de Gascogne et dans le golfe du Lion. Les différences de caractéristiques de dynamique entre les deux peuplements révélées par ces descripteurs sont mises en relation avec un indice d'exploitation (valeur moyenne des débarquements annuels, divisée par la surface du plateau de la région concernée). D'autres régions ont été intégrées dans cette analyse lorsque les valeurs des indicateurs étaient disponibles dans la littérature (Mer du Nord, plateau de Nouvelle-Ecosse, Kenya et Guyane Française). Les indices de diversité utilisés permettent de mettre en évidence que le peuplement du golfe du Lion est plus diversifié et moins soumis à perturbations que celui du golfe de Gascogne. Ces caractéristiques semblent dues à l'histoire biogéographique de ces deux régions et non à un effet de la pêche. La variabilité de la biomasse totale et celle de la pente du spectre multispécifique augmentent depuis les régions les moins exploitées vers les plus exploitées. A l'inverse, la ségrégation spatiale diminue. En théorie, les interactions entre espèces diminuent la variabilité temporelle de la biomasse totale et de la pente du spectre multispécifique, à cause de compensations entre espèces, et augmentent la ségrégation spatiale par exclusion compétitive. L'interprétation donnée des résultats obtenus est ainsi une altération des interactions entre les espèces par l'exploitation. En prélevant de la biomasse, l'exploitation augmente la disponibilité des ressources pour les individus non pêchés. En conséquence, l'exclusion compétitive diminue et la coexistence locale des individus est facilitée. A long terme, la diversité est donc menacée, non seulement par raréfaction des espèces prélevées par l'exploitation mais aussi parce que les interactions sont altérées et que le maintien de la diversité en dépend pour partie.
Cybium (0399-0974) (Soc Francaise D Ichtyologie), 2001 , Vol. 25 , N. 3 , P. 293-294

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00000/10248/7688.pdf
http://archimer.ifremer.fr/doc/00000/10248/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 μm. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 °C, and constant shear strain rates ranging from 8 × 10−5 to 1.4 × 10−4 s−1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 μm down to 3-4 μm due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (γ < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.
ISSN: 0031-9201

hal-00745170
https://hal.archives-ouvertes.fr/hal-00745170
DOI : 10.1016/j.pepi.2012.05.001

Éditeur(s) : HAL CCSD
Résumé : 28 pages, 6 figures
We study a universal object for the genealogy of a sample in populations with mutations: the critical birth-death process with Poissonian mutations, conditioned on its population size at a fixed time horizon. We show how this process arises as the law of the genealogy of a sample in a large class of critical branching populations with mutations at birth, namely populations converging, in a large population asymptotic, towards the continuum random tree. We extend this model to populations with random foundation times, with (potentially improper) prior distributions g_i: xmapsto x^{-i}, iinZ_+, including the so-called uniform (i=0) and log-uniform (i=1) priors. We first investigate the mutational patterns arising from these models, by studying the site frequency spectrum of a sample with fixed size, i.e. the number of mutations carried by k individuals in the sample. Explicit formulae for the expected frequency spectrum of a sample are provided, in the cases of a fixed foundation time, and of a uniform and log-uniform prior on the foundation time. Second, we establish the convergence in distribution, for large sample sizes, of the (suitably renormalized) tree spanned by the sample genealogy with prior g_i on the time of origin. We finally prove that the limiting genealogies with different priors can all be embedded in the same realization of a given Poisson point measure.
https://hal.archives-ouvertes.fr/hal-01053343

hal-01053343
https://hal.archives-ouvertes.fr/hal-01053343
ARXIV : 1407.7720

Éditeur(s) : HAL CCSD
Résumé : International audience
Mylonite bodies are exhumed extensions at depth of shallow structural level brittle faults. They are characterised by intense strain localisation involving large volumes of middle to lower continental crust. The analysis of shear zone geometry and microstructures is a useful tool to decipher deformation kinematics, though finite strain estimation is still relatively qualitative. Timing of the deformation has also been the focus of numerous studies using the complete spectrum of geochronometers. However, only rare examples provide geochronological data that can be unambiguously interpreted and cooling, recrystallisation and neocrystallisation are difficult to tell from each other. Thus, time-scales over which major mylonite zones develop and remain active under ductile conditions as well as their strain rate often remain poorly documented. We investigated two sections across the South-Armorican Shear Zone (SASZ), a crustal-scale pluri-km thick dextral shear zone active during a single tectonic event of late-Variscan age and associated with syntectonic granite emplacement.. Finite strain profiles on these cross-sections, quantified from average Quartz grain-size in 34 samples, show a strong deformation partitioning towards the center of the SASZ, with a decrease, for each section, from 150µm in slightly deformed zones to less than 7-5 µm in the core of the ultramylonite. Furthermore, toward the core of the SASZ, development of a penetrative shear band network progressively eliminates lenses of less deformed rocks and results in homogenisation of the Quartz grain sizes. In parallel, we performed in-situ UV-laser Ar/Ar dating on the fabric-forming white micas. White micas population can be decomposed into inherited muscovites carried by the folation and newly-formed, syn-tectonic substituted phengites located along the shear bands yielding 2 age groups for each sample. Along the profiles, the difference between these two ages evolves from 10-15 Ma in weakly deformed domains to zero toward the SASZ core. In addition, mylonite-forming phengites yielded the same age irrespectively of their position on the section or of the rock strain.. On the regional point of view, this study brings deformation-ages for the late-orogenic evolution of the South Armorican domain. Strain accumulated along the SASZ in a time-span extending to 300-298 Ma, i.e. contemporaneously with the activity of nearby major extensional shear zones. These results support a new model of crustal-scale shear zone activity, where the whole body of the shear zone is active throughout its history (defined as the largest age difference through the section), i.e. the actively deforming zone does not get progressively narrower. The strain distribution nevertheless evolves with time, with an increasingly large fraction partitioned in the ultramylonitic core.
EGU General Assembly
Vienne, Austria

insu-00839320
https://hal-insu.archives-ouvertes.fr/insu-00839320
BIBCODE : 2010EGUGA..12.9881A

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We explore the use of seismic noise produced by rivers to monitor the bed load transport in the case of a low-discharge braided river in the French Alps: the "torrent de St Pierre". For this purpose, we deployed two dedicated seismic networks during summers 2007 and 2008, for which the characteristics of the recorded continuous signal are similar despite changes in the sensor locations. For dry weather conditions, only melting of nearby glaciers controls the supply of water to the stream. In these conditions, the river hydrology and the seismic energy in the 2-80 Hz frequency band both follow a diurnal fluctuation similar to the thermal amplitude. In contrast during rainfall episodes, the temperature variation fails to explain the hydrodynamic changes. Dense cloud covers reduce glacier melting and the recorded seismic energy denotes bursts of high-frequency seismic noise well correlated with water level data. Comparisons between the recorded seismic signals and the collected hydrological and sediment load data indicate that a frequency band of 3-9 Hz best explains the water level changes and thus the seismic waves coming from the flow turbulence. These analyses also reveal the presence of a seismic noise threshold that might be linked to the water shear stress exerted by the flowing water. Using the seismic energy in this frequency band as a proxy of the fluvial shear stress, the seismic-hydrologic relationship may be sensitive to variations in bed load transport. The spectral content of the seismic energy shows patterns consistent with the mobilization of sediment particles. From the interpretations of the seismic wave attenuation of river sources, we finally propose that stations at a distance from the stream less than 50 m are able to record most sediment particles. Farther stations are still useful during extreme events when largest grain sizes are mobilized. More generally this study demonstrates the feasibility of using the river seismic signal to survey bed load transport in various river types from small braided mountain rivers like the "torrent de St Pierre" to the large entrenched Himalayan rivers.
ISSN: 0022-1694

hal-00644789
https://hal.archives-ouvertes.fr/hal-00644789
DOI : 10.1016/j.jhydrol.2011.07.014

Éditeur(s) : Elsevier
Résumé : Choice of sampling method and survey period can have an important impact on the perception of the structure and dynamics of an ecological community. For the Celtic Sea fish assemblage we compared data obtained by three different trawl surveys: an autumn groundfish survey with a GOV trawl, and a spring and an autumn groundfish survey, both carried out with a Portuguese high-headline trawl. Time-series of abundance estimates were not consistent among surveys for all species and were generally very noisy. An analysis of variance components showed that the sampling method contributed more to the variance in abundance estimates compared to survey period, interannual variability, or even sampling variance. Overall community assessments based on indicators such as proportions of non-commercial and piscivorous species, and the proportion of benthic species showed similar trends for all data series. The shape of the size spectrum based on abundances per length class summed over all fish species, although stable over time, was highly sensitive to the sampling method. With the exception of size spectra, community indicators for marine fish assemblages monitored by surveys seem to be robust to survey period and trawling gear, but species abundance trends are method dependent.
ICES Journal of Marine Science (1054-3139) (Elsevier), 2004-05 , Vol. 61 , N. 3 , P. 351-362

Droits : 2004 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd
http://archimer.ifremer.fr/doc/2004/publication-899.pdf
DOI:10.1016/j.icesjms.2004.01.004
http://archimer.ifremer.fr/doc/00000/899/

Éditeur(s) : HAL CCSD
Résumé : The presence of obstacles met in natural environment by the flow, influences the dispersion of air pollutants which it carries. This thesis, based on spatiotemporal micro-meteorological measurements in tropical region, aims at studying the dispersion of compounds emitted by the ecosystem mangrove according to the weather conditions. At a daily scale, the meteorological analysis reveals, besides the presence of Trade Winds, the existence of thermal flows of which nocturnal thermodynamic parameters have been defined. The field observation has shown that the weak intensity of the wind disadvantages the dispersion of compounds emitted during the night. At a finer scale, the existence of a spectral gap separating large scale phenomena of those related to turbulence has been demonstrated. These last ones were treated by spectral and statistical approaches to quantify the turbulent fluxes of momentum and sensible heat during the night, for an averaged duration of 13 minutes. The stratification of the surface layer has been considered and determined by Monin-Obukhov similarity theory. The measurements acquired at night and the application of Kolmogorov theory allowed us to deduct the dissipation rate of energy and the size of the vortices at 5.5 meters in height. This work has also led us, by gas chromatography coupled to mass spectrometry, to identify, in mangrove, sulphurated volatil organic compounds, organohalogen, BTEX, ... All these results will later serve to feed dispersion models related to the studied ecosystem.
La présence d'obstacles rencontrés en milieu naturel par l'écoulement, influence la dispersion des polluants qu'il transporte. Cette thèse, fondée sur des mesures micro-météorologiques spatio-temporelles en région tropicale, vise à étudier la dispersion de composés émis par l'écosystème mangrove en fonction des conditions météorologiques. A l'échelle journalière, l'analyse météorologique révèle, outre la présence des Alizés, l'existence d'écoulements thermiques dont des paramètres thermodynamiques nocturnes ont été définis. L'observation terrain nous a montré que la faible intensité du vent défavorise la dispersion des composés émis durant la nuit. A une échelle plus fine, l'existence d'un trou spectral séparant les phénomènes de grande échelle de ceux liés à la turbulence a été mise en évidence. Ces derniers ont été traités par des approches spectrale et statistique pour quantifier les flux turbulents de quantité de mouvement et de chaleur sensible, pendant la nuit, pour une durée de moyenne de l'ordre de 13 minutes. L'état de stratification de la couche de surface a été pris en compte et déterminé par la théorie de similitude de Monin-Obukhov. Les mesures nocturnes effectuées et l'application de la théorie de Kolmogorov ont permis de déduire les taux de dissipation de l'énergie et la taille des tourbillons à 5,5 m d'altitude. Ce travail a également conduit, par l'analyse chromatographique en phase gazeuse couplée à la spectrométrie de masse, à l'identification, en mangrove, de composés organiques volatils soufrés, des organohalogénés, des BTEX, ... L'ensemble de ces résultats servira ultérieurement à alimenter les modèles de dispersion spécifiques liés aux écosystèmes étudiés.
https://tel.archives-ouvertes.fr/tel-00665882

Droits : info:eu-repo/semantics/OpenAccess
NNT : 11AGUY0438
tel-00665882
https://tel.archives-ouvertes.fr/tel-00665882
https://tel.archives-ouvertes.fr/tel-00665882/document
https://tel.archives-ouvertes.fr/tel-00665882/file/ThA_seCdAlexis.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
Mylonite-bearing crustal shear zones are exhumed extensions at depth of (potentially seismogenic) brittle faultsat shallow structural level. By concentrating deformation, shear zones play a major role in the rheology and mechanicalbehavior of the continental crust. Analysis of shear zone geometry and microstructures is a useful toolto decipher deformation kinematics, though finite strain estimation is still relatively qualitative. Timing of thedeformation has also been the focus of numerous studies using the complete spectrum of geochronometers. However,only rare examples provide geochronological data that can be unambiguously linked with deformation. Thus,time-scales over which major mylonite zones develop and remain active under ductile conditions as well as theirstrain rates often remain poorly documented. Several sections across the South Armorican Shear Zone (SASZ),a crustal-scale, several km-thick dextral shear zone were investigated by structural, petrological and Ar/Ar radiochronologicalmethods. Finite strain profiles on these sections showed a strong deformation partitioning towardsthe ultramylonite core of the SASZ, with a decrease, of both the C’/S mean angle (from ca. 45 to less than5) and the Quartz grain-size (from ca. 150 to 5 m). In parallel, conventional and in-situ Ar/Ar datings on thefabric-forming white micas were performed on compositionally complex white-micas. Inherited magmatic muscovitescarried by the foliation and newly-formed, syn-tectonic substituted phengites located along the shear bandsyielded 2 age groups for the less deformed samples. Along the shear zone cross-section, the difference betweenthese two ages evolves from 10-15 Ma in weakly deformed domains to zero toward the SASZ core. In addition, thevery fine-grained syn-tectonic phengites yielded the same ca. 300-298 Ma age irrespectively of their distance to thecore of the shear zone, even in slightly deformed rocks distant by several km. These results support a new modelof crustal-scale shear zone activity, where the whole body of the shear zone is active throughout its history, i.e.the actively deforming zone does not get progressively narrower. The strain distribution nevertheless evolves withtime, with an increasingly larger fraction partitioned in the ultramylonitic core. Besides, combination of the finitestrain estimations and the Ar/Ar ages enables us to assess the range of strain rates associated with mylonitization.
EGU General Assembly 2014
Vienne, Austria

insu-01565057
https://hal-insu.archives-ouvertes.fr/insu-01565057

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : The south-west lagoon of New Caledonia is a wide semi-open coral reef lagoon bounded by an intertidal barrier reef and bisected by numerous deep inlets. This paper synthesizes findings from the 2000-2008 French National Program EC2CO-PNEC relative to the circulation and the transport of suspended particles in this lagoon. Numerical model development (hydrodynamic, fine suspended sediment transport, wind-wave, small-scale atmospheric circulation) allowed the determination of circulation patterns in the lagoon and the charting of residence time, the later of which has been recently used in a series of ecological studies. Topical studies based on field measurements permitted the parameterisation of wave set-up induced by the swell breaking on the reef barrier and the validation of a wind-wave model in a fetch-limited environment. The analysis of spatial and temporal variability of suspended matter concentration over short and long time-scales, the measurement of grain size distribution and the density of suspended matter (1.27 kg 1(-1)), and the estimation of erodibility of heterogeneous (sand/mud, terrigenous/biogenic) soft bottoms was also conducted. Aggregates were shown to be more abundant near or around reefs and a possible biological influence on this aggregation is discussed. Optical measurements enabled the quantification of suspended matter either in situ (monochromatic measurements) or remotely (surface spectral measurements and satellite observations) and provided indirect calibration and validation of a suspended sediment transport model. The processes that warrant further investigation in order to improve our knowledge of circulation and suspended sediment transport in the New Caledonia lagoon as well as in other coral reef areas are discussed, as are the relevance and reliability of the numerical models for this endeavour.
Marine Pollution Bulletin (0025-326X) (Pergamon-elsevier Science Ltd), 2010 , Vol. 61 , N. 7-12 , P. 269-296

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00014/12526/9401.pdf
DOI:10.1016/j.marpolbul.2010.06.023
http://archimer.ifremer.fr/doc/00014/12526/

Éditeur(s) : HAL CCSD
Résumé : Semi-volatile organic compounds (SVOCs) refer to a broad spectrum of molecules from different chemical families that have numerous properties. They can be used as pesticides, plasticizers, flame retardants, surfactants, lubricants, etc. Consequently, they are introduced in numerous applications in buildings or used daily by the entire population. Once emitted through evaporation or abrasion in the indoor environment or introduced from the outdoors, their chemical or biological degradation is limited, and they persist indoors. This persistence also explains why some SVOCs that were banned a few years ago are still detected in the air and dust inside buildings. In indoor environments, SVOCs are divided between the gas phase, airborne particles, and dust settled on floors and surfaces. SVOCs are of concern due to their established or suspected health effects and their widespread exposure through different environmental media and pathways. The objective of the thesis was to study the concentrations of 66 SVOCs on airborne particles (PM10) and 48 SVOCs in settled dust in two samples of dwellings randomly selected across France. PM10 were sampled during the nationwide housing survey carried out by the French Observatory of indoor air quality in 2003-2005. The dust samples were collected from vacuum cleaner bags during a nationwide survey carried out in French dwellings where at least one child aged 6 months to 6 years lived (2008-2009). The SVOCs to be analyzed had prior been selected using a ranking method based on their toxicity and indoor concentrations. The data analysis focused in particular on the identification of French specificities in terms of detected molecules and measured concentrations. It highlighted some determinants of exposure, e.g., influence of particle size, type of dust collected, dust bioaccessibility, which are not always considered and limit the comparability of results. The measured concentrations were also used to assess the health ranking implemented prior to this work and to confirm its relevance. The concentrations measured both in the air and in settled dust were compared to study the similarities in terms of concentrations and SVOC mixtures. Finally, the exposure doses to SVOCs were calculated for both a child and an adult to assess the respective contributions of inhalation and ingestion to these compounds in particulate phase in dwellings.
Les composés organiques semi-volatils (COSV) font l’objet d’une attention croissante depuis une dizaine d’années. Utilisés dans de nombreux produits et matériaux du quotidien, ils sont émis dans les bâtiments par dispersion lors de l’usage, par évaporation ou abrasion. Du fait de leurs caractéristiques physico-chimiques, ces composés se répartissent à la fois dans l’air, en phases gazeuse et particulaire, et dans les poussières déposées au sol, sur le mobilier et les objets. Compte tenu du temps passé par la population dans les bâtiments, en particulier par les populations sensibles comme les enfants, les femmes enceintes et les personnes âgées, l’exposition à ces substances mérite d’être documentée, tenant compte des voies d’exposition en jeu : inhalation, ingestion et contact cutané. La thèse a porté sur les COSV présents en phase particulaire dans les logements. L’objectif de la thèse visait à exploiter les mesures de 66 COSV dans les particules en suspension de diamètre inférieur à 10 µm (PM10) et de 48 COSV dans les poussières au sol de taille inférieure à 100 µm considérées comme étant celles adhérant à la peau. Ces mesures ont été réalisées dans le cadre de deux campagnes nationales : la campagne « Logements » de l’Observatoire de la qualité de l’air intérieur conduite en 2003-2005 et l’enquête Plomb-Habitat dont les prélèvements ont eu lieu en 2008-2009. Une hiérarchisation des molécules jugées prioritaires au regard de leur impact sanitaire potentiel avait permis au préalable d’établir la liste des COSV à mesurer. L’exploitation de ces données de contamination a notamment porté sur l’identification d’éventuelles spécificités françaises au regard des molécules en présence et/ou des concentrations mesurées. Elle a permis de mettre en lumière un ensemble de facteurs déterminants de l’exposition (influence de la taille des particules, du type de poussières collectées, de leur bioaccessibilité), qui ne sont pas toujours considérés et qui limitent par ailleurs la comparabilité des résultats. Les concentrations mesurées ont aussi permis d’évaluer rétrospectivement la hiérarchisation sanitaire et d’en confirmer la pertinence. Les concentrations des COSV quantifiés à la fois dans l’air et au sol ont été mises en perspective afin d’examiner dans quelle mesure les particules en suspension et les poussières déposées sont similaires en termes de concentrations et de mélanges de COSV en présence. Enfin, l‘estimation des doses d’exposition aux COSV à partir d’équations simples, de variables humaines d’exposition et des données de contamination a permis une première évaluation des contributions respectives de l’inhalation et de l’ingestion aux expositions domestiques des enfants et adultes à ces composés en phase particulaire.
https://tel.archives-ouvertes.fr/tel-01308524

NNT : 2015REN1B033
tel-01308524
https://tel.archives-ouvertes.fr/tel-01308524
https://tel.archives-ouvertes.fr/tel-01308524/document
https://tel.archives-ouvertes.fr/tel-01308524/file/MANDINCorinne.pdf