Isabelle Le Hécho | Université De Pau Et Des Pays De L'adour (original) (raw)

Papers by Isabelle Le Hécho

Les nanomateriaux sont au cœur des preoccupations des scientifiques tant leurs caracteristiques p... more Les nanomateriaux sont au cœur des preoccupations des scientifiques tant leurs caracteristiques physico-chimiques et leur taille leur conferent des proprietes uniques. L'evolution des outils d'observation et d'analyse de la matiere a permi l'etude a l'echelle nanometrique. On appelle nanomateriau des objets dont une des dimension est comprise entre 1 et 100 nanometres. De part leur taille, ces particules ont tres souvent une surface specifique importante, entrainant des proprietes bio-physico-chimiques particulieres, mais egalement ue mobilite et une reactivite precise. Cet article propose de faire le point sur ces particules, en presentant en premier lieu l'interet de leur etaude. Ensuite, quelques exemples d'applications sont presentes, naturels ou non. Enfin, les perspectives de developpement futur sont abordees.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 15, 2003

International audienc

HAL (Le Centre pour la Communication Scientifique Directe), Nov 6, 2019

HAL (Le Centre pour la Communication Scientifique Directe), Sep 4, 2016

HAL (Le Centre pour la Communication Scientifique Directe), Jul 13, 2014

HAL (Le Centre pour la Communication Scientifique Directe), Apr 3, 2005

HAL (Le Centre pour la Communication Scientifique Directe), Jun 19, 2017

HAL (Le Centre pour la Communication Scientifique Directe), Sep 17, 2017

HAL (Le Centre pour la Communication Scientifique Directe), Feb 11, 2010

HAL (Le Centre pour la Communication Scientifique Directe), Sep 8, 2020

HAL (Le Centre pour la Communication Scientifique Directe), Sep 20, 2021

$Research paper thumbnail of Diffusive isotope fractionation of benzene in water$

Goldschmidt2022 abstracts

International audienceRadioisotopes 131I, 129I, 79Se, 134Cs and 137Cs are of health concerns in c... more International audienceRadioisotopes 131I, 129I, 79Se, 134Cs and 137Cs are of health concerns in case of nuclear events. Due to their largeinteracting surface area by canopy, forests could impact the quantity and speciation of elements incoming from atmospheric inputs to the ground. This study investigated the atmospheric inputs of stable iodine, selenium and cesium,during one year in rainfall (twenty-seven monitored sites) as well as their canopy output in throughfall (fourteen sites)throughout France. Results showed that annual rainfall I concentrations were much higher than those of Se and Cs(mean = 1.57, 0.045 and 0.006 µg L‒1, respectively). Annual concentrations of I, Se and Na in rainfall were positivelycorrelated, suggesting common atmospheric scavenging mechanisms by rains and/or common source(s) for theseelements. Annual rainfall fluxes of elements varied greatly from one site to another (6.9-47.8, 0.20-1.86 and 0.02-0.11 gha‒1 yr.‒1 for I, Se and Cs respectively), mostly i...

Journal of Environmental Radioactivity

Radionuclides 129I (t1/2 = 15.7 × 106 years) and 131I (t1/2 = 8.02 days) are both introduced into... more Radionuclides 129I (t1/2 = 15.7 × 106 years) and 131I (t1/2 = 8.02 days) are both introduced into the environment as a result of nuclear human activities. Environmental transfer pathways and fluxes between and within ecosystems are essential information for risk assessment. In forest ecosystems, humus degradation over time could result in re-mobilization and then downward migration and/or volatilization of intercepted 129I. In order to estimate the scale of these processes, humus (mull and moder forms) sampled under deciduous and coniferous forests were spiked with 125I- (t1/2 = 59.4 days), as a surrogate for 129I, in order to study the evolution of its water-soluble and organic fractions as well as the volatilization rate during humus degradation at laboratory scale. To our knowledge, this is the first time that interactions between iodine and contrasting forms of forest humus have been investigated. The evolution of native stable iodine (127I) pools in unspiked humus was also studied. The nature of the humus' organic matter appears to be a factor that impacts on the proportions of water-soluble and organic fractions of iodine and on their evolution. Iodine-125 was mainly organically bound (fraction for mulls and moders: ∼54-59 and 41-49%, respectively) and no clear evolution was observed within the 4-month incubation period. A large decrease in 125I water-solubility occurred, being more marked for mull (from ∼14-32 to 3-7%) than for moder (from ∼21-37 to 7-19%) humus. By contrast, a significant fraction was not extractible (∼38-43%) and varied in inverse proportion to the water-soluble fraction, suggesting a stabilization of iodine in humus after wet deposit. The nature of the humus organic matter also impacted on 125I volatilization. Although of the same order of magnitude, the total volatilization of 125I was higher for moders (∼0.039-0.323%) than for mulls (∼0.015-0.023%) within the 4-month incubation period. Volatilization rates for mulls were correlated with the water-soluble fraction, implying that volatilization of 125I could occur from the humus solution. Our results showed that humus is thus a zone of iodine accumulation by association with organic matter and that potential losses by lixiviation are significantly more important compared to volatilization.

Ref : TIP958WEB - "Innovations technologiques", Oct 10, 2010

Up to now, different approaches have been proposed for in situ trace metal speciation, based on t... more Up to now, different approaches have been proposed for in situ trace metal speciation, based on the deployment of in situ devices such as Donnan Membrane device (DMT) and then analysis by ICP-MS [1], or by means of preconcentration systems hyphenated wih electrochemical detection such as gel integrated microelectrode (GIME) probe [2] or a direct in situ electrochemical stripping speciation method such as Absence Gradient Nernstian Equilibrium Stripping (AGNES) [3]. Although numerous in situ methods have been proposed, currently there is no reliable in situ probe for trace metal speciation at concentration levels present in natural systems. Regarding autonomy problems of in situ probes, electrochemical devices have the advantage of being easily available in smaller sizes and with the possibility to be operated with batteries. This work presents the probe ISIDORE developped for in situ trace metal speciation [4]. This probe is based on the hyphenation between a DMT and a screen-printe...

Science of The Total Environment, 2021

Storage of selenium and iodine can greatly vary between forest ecosystems, but the influence of t... more Storage of selenium and iodine can greatly vary between forest ecosystems, but the influence of tree species on partitioning and recycling of those elements remains elusive. In this study, contents of Se and I were measured in tree compartments, litterfall, humus, and soil horizons in monospecific stands of Douglas fir, pine, spruce, beech, and oak under identical climatic and edaphic conditions. The cycle of each element was characterized in terms of stocks and fluxes. Lowest concentrations were in wood (Se: 8-13 μg kg-1; I: <16.5 μg kg-1). Senescing organs had higher Se and I content, than the living parts of trees due to direct exposure to atmospheric deposition, with some variation between coniferous and deciduous trees. For all stands, low amounts of Se and I were involved in biological cycle as reflected by low root uptake. In humus, the enrichment of elements greatly increased with the stage of organic matter (OM) degradation with average factors of 10 and 20 for Se and I. OM degradation and element persistence in humus was influenced by tree species. Deciduous trees, with low biomass, and fast degradation of OM stored less Se and I in humus compared to fir and spruce with high humus biomass. Interestingly, tree species did not affect soil reserves of Se and I. Concentration ranges were 331-690 μg Se kg-1 and 4.3-14.5 mg I kg-1. However, the divergent vertical profiles of the elements in the soil column indicated greater mobility of I. Selenium concentrations regularly decreased with depth in correlation with OM and Fe oxides content. For iodine, the maximum iodine concentration at a soil depth of 15 to 35 cm was caused by a parallel precipitation/sorption behavior of aluminium and organic iodine dissolved in the topsoil.