The BLLAST field experiment: Boundary-Layer late afternoon and sunset turbulence

Due to the major role of the sun in heating the earth's surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The afternoon transition, the period of the day that connects the daytime dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state. These issues motivated the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign that was conducted from 14 June to 8 July 2011 in southern France, in an area of complex and heterogeneous terrain. A wide range of instrumented platforms including full-size aircraft, remotely piloted aircraft systems, remote-sensing instruments, radiosoundings, tethered balloons, surface flux stations and various meteorological towers were deployed over different surface types. The boundary layer, from the earth's surface to the free troposphere, was probed during the entire day, with a focus and intense observation periods that were conducted from midday until sunset. The BLLAST field campaign also provided an opportunity to test innovative measurement systems, such as new miniaturized sensors, and a new technique for frequent radiosoundings of the low troposphere. Twelve fair weather days displaying various meteorological conditions were extensively documented during the field experiment. The boundary-layer growth varied from one day to another depending on many contributions including stability, advection, subsidence, the state of the previous day's residual layer, as well as local, meso- or synoptic scale conditions. Ground-based measurements combined with tethered-balloon and airborne observations captured the turbulence decay from the surface throughout the whole boundary layer and documented the evolution of the turbulence characteristic length scales during the transition period. Closely integrated with the field experiment, numerical studies are now underway with a complete hierarchy of models to support the data interpretation and improve the model representations.publishedVersio

Métrologie de la fraction fine de l'aérosol métallurgique (apport des techniques micro-analytiques (microspectrométrie X et spectroscopie de perte d'énergie des électrons)

Les poussières émises par l'industrie métallurgique concourent à la qualité de l'air des zones urbaines voisines. Ces particules, émises par des procédés à "haute température", sont susceptibles d'évoluer rapidement au sein des panaches. L'objectif de l'étude est de caractériser la phase particulaire sur un site d'émission métallurgique et de déterminer la nature et l'amplitude des transformations physico-chimiques subies par ces particules dans les premières minutes de leur émission. Des prélèvements d'aérosols ont été réalisés au sein des cheminées et dans l'environnement proche d'une usine métallurgique (production d'alliage de ferromanganèse), dont l'atelier d'agglomération est le principal émissaire. Le spectre granulométrique des particules dans l'environnement montre un enrichissement de nanoparticules (10-100nm) après survol des masses d'air au dessus du site industriel. Les rejets caractéristiques de l'usine (émission d'oxydes de fer et de manganèse, mais également d'aluminosilicates) se trouvent la plupart du temps sous forme d'agglomérats de composition chimique hétérogène et de structure morphologique complexe. Ces agglomérats semblent évoluer rapidement par adsorption de composés organiques volatils ou de suies. L'étude de la spéciation du Fe et du Mn au sein de ces particules indique qu'elles sont sujettes à des réactions d'oxydation via des mécanismes de conversion gaz/particules au sein même du procédé industriel, aboutissant notamment à une oxydation du fer inversement proportionnelle à la taille des particules. Par contre, aucune évolution significative du degré d'oxydation du Fe et du Mn n'a été observée dans l'environnement proche de l'émissaire.Steelworks activities are important sources of fine particles which may affect air quality in urban areas close to plants. Those particles are emitted by "high-temperature" processes and could evolve very quickly in the plumes. The main objective of this study is to evaluate the nature and the amplitude of physico-chemical evolutions of those particles in the few minutes after the emission. Aerosol samplings were performed inside the chimneys and in the close environment of a FeMn alloys manufacturing plant where the sintering unit is the most important source of particles. The number size distributions in the close environment show a higher abundance of nanoparticles (10-100nm) inside the plume, by comparison with air masses upwind from the plant. The chemical analysis indicates that particles characteristic of the plant emissions (iron and manganese oxides but also aluminosilicates) are mostly constituted of agglomerates. These agglomerates combine various compounds inside a same particle in a complex structure. Moreover, they evolve rapidly (in a few minutes) after emission by mixing with organic compounds inside the plume. This evolution results from the adsorption of volatile organic compound or the agglomeration with soot particles. The study of iron and manganese speciation inside particles shows that they are prone to oxidation reactions via gas/particle conversion mechanisms during the industrial process, leading notably to a higher iron oxidation state for the smallest particles. However, no change of iron and manganese oxidation state was observed in the close environment of the plant.DUNKERQUE-SCD-Bib.electronique (591839901) / SudocSudocFranceF

Isotopic evidence of spatial magnitude of the Pb deposition near a lead smelter

In order to determine the dry deposition of lead around a Pb-Zn refinery, two cross-sectional sampling experiments, using deposition plates, have been performed on a daily basis, under representative meteorological situations (north-easterly and south-westerly winds). The amount of lead deposited, as well as its isotopic composition (expressed by the 206Pb/207Pb ratio) are systematically measured. For a daily production of approximately 670 metric tons of (Pb+Zn), the dry fallout, greater than 1000 μg Pb.h-1.m-2 on the edge of the plant, falls to about 100 μg Pb.h-1.m-2, four kilometres away from the refinery. This value is still ten times higher than the urban background (< 10 μg Pb.h-1.m-2). The spatial extension of the dry deposition plume is evidenced by the evolution of the isotopic signature of the refinery (1.10<206Pb/207Pb<1.13), clearly distinct from the urban background signature (1.15<206Pb/207Pb<1.16). As a first estimate, the extension of the deposition plume seems not to be linked to the wind speed. At the opposite, diffuse emissions from slag heaps are related to this parameter.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Single-particle analysis of atmospheric aerosols at Cape Gris-Nez, English Channel: Influence of steel works on iron apportionment

International audienc

Fe and Mn Oxidation States by TEM-EELS in Fine-Particle Emissions from a Fe–Mn Alloy Making Plant

International audienc

Review of pollutant lead decline in urban air and human blood: A case study from northwestern Europe

International audienceA review of the transient decline of pollutant lead in the air (PbA) and the blood (PbB) has been conducted in order to assess the relationship between these environmental reservoirs. We have demonstrated that PbA decreased 20 to 100 times more than PbB for the past 30 years, suggesting another significant intake besides airborne lead to explain lead accumulated in humans. This trend has also been observed in two blood surveys we have completed in 1976-1978 and 2008-2009 in northern France and Belgium. Nowadays, the mean PbB (1.5-3.5 mu g/dL) remains at least 100 times higher than the estimated non contaminated PbB. Lead isotope imprints in blood could help decipher specific contamination cases, and were coherent with the decline of PbA, but could not help discriminate the source of blood lead owing to the lack of source imprints, especially from dietary intakes. Correlations between recent PbB, isotopic imprints and the age of the subjects suggested that lead released from bones has become a significant source of lead in blood. The significant cause for human exposure to lead may have shifted from direct pollutant lead input accumulated in exogenous reservoirs (air and diet) to endogenous lead release from bone tissues consequential to metabolic calcium homeostasis and bone turnover. (C) 2015 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved

Evidencing lead deposition at the urban scale using "short-lived" isotopic signatures of the source term (Pb-Zn refinery)

To demonstrate the ability of the lead isotope signature technique to evidence the spatial extent of an industrial Pb deposition plume at a local scale, dry deposition of lead in the urban environment of a Pb-Zn refinery was investigated, as a study case, using transient ("short-lived") isotopic signatures of the industrial source. Sampling campaigns were achieved in representative weather conditions, on an 8-h basis. Dry deposition rates measured downwind from refinery emissions (≈102-10 3μgPbm-2h-1), cross-sectionally in a 3-5km radius area around the plant, represent 10-100 times the urban background dry fallout, measured upwind, as well as fallout measured near other potential sources of anthropogenic Pb. The Pb-Zn refinery isotopic signature (approx. 1.100<206Pb/207Pb<1.135) is made identifiable, using the same set of Pb and Zn ores for 2 days before sampling and during field experiments, by agreement with the executive staff of the plant. This source signature is less radiogenic than signatures of urban background Pb aerosols (1.155<206Pb/207Pb<1.165) and minor sources of Pb aerosols (1.147<206Pb/207Pb<1.165). By a simple binary mixing model calculation, we established the extension of the industrial Pb deposition plume. Fifty to eighty percents of total lead settled by the dry deposition mode, 3-4km away from the refinery, still have an industrial origin. That represents from 40 to 80μgPbm-2h-1, in an area where the blood lead level exceeds 100μgPbl-1 for 30% of men and 12% of women living there. We demonstrate here that stable Pb isotope analysis is able to evidence the Pb dry deposition plume in stabilised aerodynamic conditions, using a short-lived source term, suggesting that this methodology is able to furnish valuable data to validate industrial Pb aerosols dispersion models, at the urban scale. © 2004 Elsevier Ltd. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Assessment of pollution aerosols sources above the Straits of Dover using lead isotope geochemistry

We assess the capability of lead isotopes to study the transport of pollution aerosols above the Straits of Dover by collecting atmospheric aerosols above the Eastern Channel and the Southern Bight of the North Sea. During the same period, we characterized the lead isotopic signature of the main industrial sources on the French coast near the Straits of Dover. Urban and automobile-derived aerosols were also collected. Due to the phasing out of lead in gasoline, the urban isotopic composition (206Pb/207Pb=1.158±0.003) has become more radiogenic, although it is highly variable. On a regional scale, major industrial emissions have a well-defined isotopic composition (1.13<206Pb/207Pb<1.22), more radiogenic than the petrol-lead signature (1.06<206Pb/207Pb<1.12). These results together with those measured near the main coastal highway show that the automobile source has become a minor component of particulate lead in air. On a local scale, Dunkerque, the most urbanized and industrialized area along the Straits of Dover, may transiently control elevated lead concentrations. Except for the occurrence of local and regional range transport episodes, lead concentrations in the Straits of Dover can be related to remote or semi-remote pollution source emissions. Combining air mass retrospective trajectories and related lead abundances and isotopic compositions, it can be shown that lead aerosols originating from eastern Europe have an isotopic signature (1.145<206Pb/207Pb<1.169) different from the isotopic composition of west-European lead aerosols (1.111<206Pb/207Pb<1.142). The influence of remote North American sources is suggested, with caution, due to uncertainties in meteorological calculations. Copyright (C) 1999 Elsevier Science B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Zn isotopes: tracers of atmospheric emissions related to metallurgical activities

INVITED Talkinfo:eu-repo/semantics/publishe

Microscopic observations of core-shell particle structure and implications for atmospheric aerosol remote sensing

International audienc