Unravelling New Processes at Interfaces: Photochemical Isoprene Production at the Sea Surface

Isoprene is an important reactive gas that is produced mainly in terrestrial ecosystems but is also produced in marine ecosystems. In the marine environment, isoprene is produced in the seawater by various biological processes. Here, we show that photosensitized reactions involving the sea-surface microlayer lead to the production of significant amounts of isoprene. It is suggested that H-abstraction processes are initiated by photochemically excited dissolved organic matter which will the degrade fatty acids acting as surfactants. This chemical interfacial processing may represent a significant abiotic source of isoprene in the marine boundary layer

Is Adipose Tissue a Place for Mycobacterium tuberculosis Persistence?

BACKGROUND: Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), has the ability to persist in its human host for exceptionally long periods of time. However, little is known about the location of the bacilli in latently infected individuals. Long-term mycobacterial persistence in the lungs has been reported, but this may not sufficiently account for strictly extra-pulmonary TB, which represents 10–15% of the reactivation cases. METHODOLOGY/PRINCIPAL FINDINGS: We applied in situ and conventional PCR to sections of adipose tissue samples of various anatomical origins from 19 individuals from Mexico and 20 from France who had died from causes other than TB. M. tuberculosis DNA could be detected by either or both techniques in fat tissue surrounding the kidneys, the stomach, the lymph nodes, the heart and the skin in 9/57 Mexican samples (6/19 individuals), and in 8/26 French samples (6/20 individuals). In addition, mycobacteria could be immuno-detected in perinodal adipose tissue of 1 out of 3 biopsy samples from individuals with active TB. In vitro, using a combination of adipose cell models, including the widely used murine adipose cell line 3T3-L1, as well as primary human adipocytes, we show that after binding to scavenger receptors, M. tuberculosis can enter within adipocytes, where it accumulates intracytoplasmic lipid inclusions and survives in a non-replicating state that is insensitive to the major anti-mycobacterial drug isoniazid. CONCLUSIONS/SIGNIFICANCE: Given the abundance and the wide distribution of the adipose tissue throughout the body, our results suggest that this tissue, among others, might constitute a vast reservoir where the tubercle bacillus could persist for long periods of time, and avoid both killing by antimicrobials and recognition by the host immune system. In addition, M. tuberculosis-infected adipocytes might provide a new model to investigate dormancy and to evaluate new drugs for the treatment of persistent infection

Optimisation des prélèvements par accumulation et dosage par couplage GC/MS des COV présents dans les stockages d'ordures ménagères: Première approche de comparaison de méthodes analytiques

The present article is devoted to an approach of optimization of required conditions to traces VOCs analysis coming from household wastes stocked in specially designed pilots for studying maturation. A known volume of the gas phase goes through tubes filled with various adsorbents like Tenax, Chromosorb, Tenax-graphitized carbon and active charcoal. To extract VOCs, thermal desorption has been used for the first three adsorbents while CS2 extraction has been applied on active charcoal tubes. About 200 VOCs were surely identified and performances of the two sample preparation processes were compared: accumulation followed by thermal desorption or followed by solvent extraction. Both analysis techniques are compared in order to set all the precautions for a reliable quantitative analysis.Le travail présenté constitue une approche de l'optimisation des conditions nécessaires à l'analyse des composés organiques volatils (COV) émis par des ordures ménagères en cours de maturation dans un pilote. Un volume connu de la phase gaz du pilote parcourt des tubes à accumulation de différentes natures : Tenax, Chromosorb, Tenax-carbone graphite et charbon actif. Les COV piégés sur les trois premiers types de tubes ont été extraits pas désorption thermique et par extraction au sulfure de carbone pour les tubes à charbon actif. Plus de 200 COV sont identifiés avec certitude et les performances des deux filières accumulation/désorption thermique et accumulation/extraction par solvant sont comparées. Quelques précautions à prendre pour un dosage quantitatif fiable sont émises

Impact environnemental des émissions liées au compostage :de la définition d'un protocole d'échantillonnage à l'évaluation de l'exposition des populations

Rapport FINA

Impact environnemental des émissions liées au compostage :de la définition d'un protocole d'échantillonnage à l'évaluation de l'exposition des populations

Rapport FINA

Salting out, non-ideality and synergism enhance surfactant efficiency in atmospheric aerosols

Abstract In Earth’s atmosphere, the surface tension of sub-micron aerosol particles is suspected to affect their efficiency in becoming cloud droplets. But this quantity cannot be measured directly and is inferred from the chemical compounds present in aerosols. Amphiphilic surfactants have been evidenced in aerosols but experimental information on the surface properties of their mixtures with other aerosol components is lacking. This work explores experimentally the surface properties of aqueous mixtures of amphiphilic surfactants (SDS, Brij35, TritonX100, TritonX114, and CTAC) with inorganic salts (NaCl, (NH4)2SO4) and soluble organic acids (oxalic and glutaric acid) using pendant droplet tensiometry. Contrary to what could be expected, inorganic salts and organic acids systematically enhanced the efficiency of the surfactants rather than reduced it, by further lowering the surface tension and, in some cases, the CMC. Furthermore, all the mixtures studied were strongly non-ideal, some even displaying some synergism, thus demonstrating that the common assumption of ideality for aerosol mixtures is not valid. The molecular interactions between the mixture components were either in the bulk (salting out), in the mixed surface monolayer (synergy on the surface tension) or in the micelles (synergy on the CMC) and need to be included when describing such aerosol mixtures

Photocatalytic degradation of imazalil in an aqueous suspension of TiO2 and influence of alcohols on the degradation

International audienceThe photocatalytic degradation of imazalil, a probably carcinogen fungicide, was carried out in an aqueous suspension of titanium dioxide under UV irradiation. The influence of alcohols as hydroxyl scavengers (isopropanol, methanol) on the degradation was studied and different concentrations were used. We conclude that the degradation of imazalil occurs mainly by OHradical dot attack, since 80% of the degradation was inhibited in the presence of isopropanol [isopropanol] = 1000 [imazalil]. Using HPLC/DAD and LC-MS/MS analysis, nine intermediates were identified giving monohydroxylated, dihydroxylated and mostly a hole attack for other products. Their kinetic evolution profiles were plotted and compared to those with isopropanol. The quantity of photoproducts formed by OHradical dot radicals was decreased in the presence of isopropanol. After that a tentative pathway mechanism was proposed including mainly hydroxyl radical attack with the participation of holes in the degradation. Ion chromatography showed that nitrogen groups in imidazole were converted to both NH4+ and NO3−. In addition, TOC was examined in details and total mineralization was reached

Photosensitized production of functionalized and unsaturated organic compounds at the air-sea interface

The sea-surface microlayer (SML) has different physical, chemical and biological properties compared to the subsurface water, with an enrichment of organic matter i.e., dissolved organic matter including UV absorbing humic substances, fatty acids and many others. Here we present experimental evidence that dissolved organic matter, such as humic acids, when exposed to sunlight, can photosensitize the chemical conversion of linear saturated fatty acids at the air-water interface into unsaturated functionalized gas phase products (i.e. saturated and unsaturated aldehydes and acids, alkenes and dienes,…) which are known precursors of secondary organic aerosols. These functionalized molecules have previously been thought to be of biological origin, but here we demonstrate that abiotic interfacial photochemistry has the potential to produce such molecules. As the ocean is widely covered by the SML, this new understanding will impact on our ability to describe atmospheric chemistry in the marine environment

Primary particle emissions and atmospheric ageing from road traffic.

10th International Conference on Future Environment and Energy, KYOTO, JAPON, 07-/01/2020 - 09/01/2020Road traffic is a significant source of atmospheric aerosols, which are important pollutants (class 1 carcinogens for Humans). It contributes to primary and secondary particles in the atmosphere, depending on the presence of particle precursors such as volatile, intermediate-volatility, and semi-volatile organic compounds (VOCs, IVOCs, SVOCs). However, lack of knowledge exists on the sampling methodology, which depends on dilution and available deposition surface. Moreover, the physicochemical and photochemical processes leading to secondary aerosols are complex, and often studied in specific experimental conditions. Therefore, contribution of transportation on aerosol pollution is under-estimated in air-quality models. This study presents particle, black-carbon (BC) and IVOC emissions on a chassis dynamometer under controlled conditions (10 diesel and gasoline passenger-cars, Euro 1 to Euro 6) and in-situ (open urban area and tunnel). Particles and BC were measured with optical devices; IVOCs were sampled on sorbent tubes and analyzed with mass-spectroscopy. IVOC emissions are 2 to 2500 times higher in-situ than for chassis dynamometer experiments. Results show that sampling conditions influence significantly IVOC concentrations, mainly due to temperature and dilution effects on gas-particle partitioning. IVOCs can also nucleate to form new particles, or condensate onto pre-existing particles, and play an important role on particle atmospheric ageing

Euro 3 and Euro 5 Diesel vehickes' particle evolution in ageing chamber

23rd International Transport and Air Pollution Conference, THESSALONIQUE, GRECE, 15-/05/2019 - 17/05/2019This study focuses on the evolution in an ageing chamber of the particles emitted by two Diesel vehicles: a Euro 5 with a Diesel Particle Filter (DPF) and a Euro 3. Both vehicles were tested on a chassis dynamometer with Artemis urban cold start (UC) and Artemis motorway (MW) cycles. Exhaust gas was injected in a 8-cubic-meter dark ageing chamber through a stainless steel line heated at 120°C, during 16 to 25 minutes. The evolution of the particles was monitored during 10 hours. Moreover, exhaust gas was sampled at emssion from the heated line on sorbent tunes, which were then analyzed with ATD-GC-MS. For the Euro 5 DPF vehicle, particle mass (PM) concentrations are below 2µg/m3 (UC/MW) and remain stable during 10h. For the Euro 3 Diesel vehicle, PM concentrations start at 270µg/m3 (UC) and 2200µg/m3 (MW). PM increases of 29% during the first 90min and then stays stable until the end for the MW. For the UC, PM increases of 125% during 10h. This indicates the formation of new particulate matter, which might in part be explained by condensation of Semi-Volatile Organic Compounds (SVOCs). Moreover, condensation would also explain the increase of the mean particle size from 250 to 500nm. Particle number (PN) concentration is close to the background for the Euro 5 DPF UC condition. For MW conditions, the particle mean size is around 20nm. For the Euro 3 Diesel UC and MW conditions, larger particles are emitted and the initial mean particle size is around 120-150nm. Moreover, the total PN decreases and the mean particle size increases with time. This could be explained by coagulation processes. Furthermore, small particles around 30nm are formed during the first hour for Euro 5 DPF MW conditions, probably by nucleation processes. Finally, different SVOCs - such as alkane, alkene, cyclo, and aromatic compounds - were followed with C numbers between C12 and C30 at emission and during the first 6h of ageing. Considering their relatively low volatilities, these SVOCs could play a role in secondary particle formation through physicochemical interactions