Uptake and surface chemistry of SO2 on natural volcanic dusts

V-dust (v-dust) is a highly variable source of natural particles in the atmosphere, and during the period of high volcanic activity it can provide a large surface for heterogeneous interactions with other atmospheric compounds. Icelandic v-dust was chosen as a case study due to frequency of volcanic eruptions and high aeolian activity in the area. In this study, we focus on the kinetics and mechanism of the reaction of sulfur dioxide (SO2) with natural v-dust samples under atmospheric conditions using coated wall flow tube reactor and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Steady state uptake coefficients determined are in the range of 10−9 to 10−8 depending on the considered v-dust. Concomitantly with SO2 uptake, both sulfites and sulfates are monitored on the surface of v-dust, with sulfates being the final oxidation product, attesting of SO2 surface reaction. Surface hydroxyl groups play a crucial role in the conversion of SO2 to sulfites as evidenced from both flow tube and DRIFTS experiments. Based on these experimental results, a mechanism for SO2 interaction with different surface sites of v-dust is proposed and discussed. This study provides original insights in the kinetics of SO2 uptake under simulated atmospheric conditions and its mechanism and transformation on volcanic material. To that regards, it brings an accurate perspective on SO2 heterogeneous sinks in the atmosphere.The authors acknowledge Mr Vincent Gaudion and Dr Mohamad Zeineddine (SAGE, IMT Lille Douai) for their assistance in the lab. We are grateful to Mr Bruno Malet and Dr Laurent Alleman (SAGE, IMT Lille Douai) for conducting the ICP-MS experiments. This work was achieved in the frame of Labex CaPPA, funded by ANR through the PIA under contract ANR-11-LABX-0005-01, and CPER CLIMIBIO project, both funded by the Hauts-de-France Regional Council and the European Regional Development Fund (ERDF). J. Lasne acknowledges support from the Labex CaPPA and CPER CLIMIBIO projects and the Hauts-de-France Regional Council for his post-doctoral fellowship.Peer Reviewe

The 2020 plasma catalysis roadmap

International audienc

Newly identified climatically and environmentally significant high-latitude dust sources

Peer reviewe

Origin and mobility of Iron Age Gaulish groups in present-day France revealed through archaeogenomics

The Iron Age period occupies an important place in French history, as the Gauls are regularly presented as the direct ancestors of the extant French population. We documented here the genomic diversity of Iron Age communities originating from six French regions. The 49 acquired genomes permitted us to highlight an absence of discontinuity between Bronze Age and Iron Age groups in France, lending support to a cultural transition linked to progressive local economic changes rather than to a massive influx of allochthone groups. Genomic analyses revealed strong genetic homogeneity among the regional groups associated with distinct archaeological cultures. This genomic homogenisation appears to be linked to individuals’ mobility between regions as well as gene flow with neighbouring groups from England and Spain. Thus, the results globally support a common genomic legacy for the Iron Age population of modern-day France that could be linked to recurrent gene flow between culturally differentiated communities

How to select the indoor air treatment device you may need ? a map of the problematic

International audienc

How to select the indoor air treatment device you may need ? a map of the problematic

International audienc

Oxydation hétérogène des COV : des fondamentaux à la qualité de l'air

My main assignment as I was recruited in 2008 at Ecole des Mines in Dpt SAGE was to create a novel research activity focused on fundamentals and applications of air treatment processes. The development of this new topic was supported by the high level academic background of the laboratory in the field of environmental gas phase analysis. In that context, I brought my expertise in the domain of (i) adsorption, (ii) photocatalysis and (iii) non-thermal plasma coupling with catalytic materials. Heterogeneous physical and chemical phenomena are the meeting points of these air treatment technologies, they had to be addressed in details with innovative experimental approaches to be understood and enhanced.The modern context of indoor air and the dramatic decrease of indoor air quality have been identified as main issues where air treatment technologies could bring effective improvements. An overview of current existing technologies points out the fact that adsorption, photocatalysis and non-thermal plasma are the relevant technologies to face the pollution characteristics and the energetic requirements of indoor air. However, none of them were effectively investigated, developed or validated under typical indoor air conditions. The three air treatment techniques share the common characteristics of being heterogeneous processes. To that regard, scientific questions were still open about (i) heterogeneous interactions between pollutants, materials and non-thermal plasma in the plasma-material coupling, (ii) the effectiveness of photocatalytic oxidation at typical ppb in the presence of multi-polluted indoor atmospheres, and (iii) the sustainability these technologies.The approach I proposed to investigate plasma-material coupling through sequential adsorption of the pollutants and plasma regeneration of the saturated coupling material offered interesting insights from a fundamental as well as a process point of view. First, it improved the distinction between gas phase and adsorbed phase phenomena. The key role of coupling material surface chemistry has been quantitatively evidenced for (i) pollutant adsorption; (ii) plasma generated oxidizing species consumption and (iii) long term performances and potential deactivation. Second, from a process point of view, it evidenced that the plasma sequential regeneration was a relevant option regarding energy consumption and oxidation reaction advancement. Based on these results, future perspectives in plasma-material coupling are proposed toward material tailored synthesis and tuned surface chemistry. The detailed investigation of photocatalytic reaction at ppb level was required by the high development of such technologies for indoor air applications whereas its effectiveness was questioned. Based on analytical developments, gas phase and adsorbed phase have been addressed from primary VOC removal to gas phase reaction intermediate, CO2 and particle matter production. The efficacy of photocatalytic oxidation for VOC abatement under typical indoor air condition was shown. However, the variability of the reaction with the nature and the diversity of VOCs have been evidenced. Adsorption considerations are relevant to describe and predict the behavior of photocatalysis on multi-polluted air, but deeper investigations have to be carried out. The key point of future developments is the real scale assessment of photocatalytic air treatment devices to propose effective standards and protocols to ensure efficiency and innocuity of such a process.My research perspectives can be structured according to two main paths. First, at short and mid-term, the development of a large scale experimental room will make possible further investigation of indoor air treatment technologies and more generally indoor air chemistry, from a homogenous to a heterogeneous point of view. This innovative device will be used for the assessment of photocatalytic air treatment devices performances and innocuity and for the evaluation of the performances of designed sorbents and catalyst when used for specific VOC adsorption and subsequent plasma regeneration. Second, I plan to widen the scope of my research activities to atmospheric heterogeneous processes investigation. Typically, my involvement in the field of heterogeneous oxidation processes could lead to the development of innovative approaches to tackle the interaction of atmospheric VOCs with mineral dust from arid area and volcanoes and the subsequent air quality impacts

Évaluation de l’innocuité des systèmes de Traitement d’Air par PhotocatalysEprojet ETAPE

Le projet ETAPE se situe à un moment clé où les techniques d’élimination des COV en air intérieur deviennent nécessaires du fait du confinement croissant des bâtiments dans une perspective d’économie énergétique. Les dispositifs d’oxydation photocatalytique des COV semblent pouvoir apporter une réponse à cette problématique liée à la qualité de l’air intérieur. Ils connaissent, depuis une dizaine d’année, une croissance forte de leur marché et sont utilisés dans des espaces confinés extrêmement variés en termes de polluants et de niveaux de concentration. Les systèmes d’épuration photocatalytiques autonomes peuvent être testés suivant la norme XP B 44-200. L’évaluation des performances des dispositifs à l’aide de cette norme ne présage (i) ni de l’efficacité du dispositif face à la pollution spécifique du milieu dans lequel il est mis en oeuvre, (ii) ni de l’innocuité du dispositif vis-à-vis de la génération de sous-produits gazeux ou particulaires.L’objectif principal du projet ETAPE est de caractériser les performances et l’innocuité de systèmes commerciaux de traitement d’air par photocatalyse dans des situations de fonctionnement types, proches des conditions réelles d’utilisation, c'est-à-dire, prenant en compte la diversité et la réalité de l’air intérieur.Dans un premier temps, quatre dispositifs commerciaux sont testés suivant la norme en vigueur. A l’issue de ces tests, deux sont retenus pour la suite du projet. Les performances des deux systèmes retenus sont évaluées face à quatre matrices gazeuses typiques : (1) air intérieur standard, (2) air intérieur en zone urbaine, (3) air intérieur bâtiment bois, (4) air intérieur milieu hospitalier.L’évaluation des performances est effectuée à travers deux approches complémentaires :1/ Evaluation physico-chimique : pour chaque matrice, les systèmes sont évalués en termes (i) d’abattement des COV de chaque matrice; (ii) de formation de sous-produits organiques gazeux ou particulaire. Cette approche permet d’évaluer des critères de performances proches des conditions réelles.2/ Evaluation procédé : pour chaque matrice, un système spécifique a été évalué (i) suivant les paramètres de fonctionnement proposés par le fabricant ; (ii) en faisant varier les paramètres du procédé de traitement (débit d’air, irradiation, mise en oeuvre du média,…). Cette approche permet de définir les paramètres de fonctionnement optimaux et proposer une optimisation des critères de performances liés au procédé

Sorption properties and photocatalytic reactivity of standard and natural dusts with model VOC

International audienc

Photocatalytic oxidation of limonene in indoor air: gas phase, adsorbed phase and particulate matter investigation

International audienc