Condensed-phase biogenic–anthropogenic interactions with implications for cold cloud formation

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles' organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (Tg) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respective Tg and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas

Détermination de la provenance des céramiques par analyse des géopolymères contenus dans les pates céramiques cuites à basse température

A low temperature ceramic material is obtained with curing temperature ranging from 250 to 500° C, using a chemical reaction, a polycondensation into a geopolymer, between a clayish mineral and caustic soda. Caustic soda is easily obtained by reacting a lime solution with sodium carbonate (salt natron of Egypt and Africa). With the different types of clays, soils, the polycondensed geopolymer has the structure of the feldspathoîd sodalite or hydrosodal ite, except illitic material which does not react and has to be fired at high temperature. Lateritic soil and Nil mud necessit an addition of a soluble silica source, such as mica, flint, chrysocolla.On obtient une consolidation céramique, par moyen chimique, à basse température, entre 250° C et 500° C, par polycondensation entre un matériau argileux et la soude caustique. Le produit obtenu est un géopolymère. La soude caustique est obtenue facilement à l'aide de lessive de chaux et de carbonate de sodium (le sel natron d'Egypte et d'Afrique). Le produit géopolymère obtenu pour différents sols ou argiles possède la structure du feldspathoïde sodalite ou hydrosodal ite, sauf pour l'illite qui ne réagit pas et qui doit donc être cuite à haute température. Les sols latéritiques et le limon du Nil nécessitent l'addition de silice soluble, provenant par exemple de mica, silex, chrysocolle.Davidovits Joseph. Détermination de la provenance des céramiques par analyse des géopolymères contenus dans les pates céramiques cuites à basse température. In: Revue d'Archéométrie, n°1, 1981. Actes du XXe symposium international d'archéométrie Paris 26-29 mars 1980 Volume III. pp. 53-56

Materiaux composites a matrice geopolymere

SIGLECNRS AR 10940 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc