6 research outputs found
Updated African biomass burning emission inventories in the framework of the AMMA-IDAF program, with an evaluation of combustion aerosols
African biomass burning emission inventories for gaseous and particulate species have been constructed at a resolution of 1 km by 1km with daily coverage for the 2000–2007 period. These inventories are higher than the GFED2 inventories, which are currently widely in use. Evaluation specifically focusing on combustion aerosol has been carried out with the ORISAM-TM4 global chemistry transport model which includes a detailed aerosol module. This paper compares modeled results with measurements of surface BC concentrations and scattering coefficients from the AMMA Enhanced Observations period, aerosol optical depths and single scattering albedo from AERONET sunphotometers, LIDAR vertical distributions of extinction coefficients as well as satellite data. Aerosol seasonal and interannual evolutions over the 2004–2007 period observed at regional scale and more specifically at the Djougou (Benin) and Banizoumbou (Niger) AMMA/IDAF sites are well reproduced by our global model, indicating that our biomass burning emission inventory appears reasonable
Mass concentration, optical depth and carbon composition of particulate matter in the major southern West African cities of Cotonou (Benin) and Abidjan (Côte d'Ivoire)
Air quality degradation is a major issue in the large conurbations on
the shore of the Gulf of Guinea. We present for the first time
PM2.5 time series collected in Cotonou, Benin, and Abidjan,
Côte d'Ivoire, from February 2015 to March 2017. Measurements were
performed in the vicinity of major combustion aerosol sources:
Cotonou/traffic (CT), Abidjan/traffic (AT), Abidjan/landfill (AL) and
Abidjan/domestic fires (ADF). We report the weekly PM2.5 mass and
carbonaceous content as elemental (EC) and organic (OC) carbon
concentrations. We also measure the aerosol optical depth (AOD) and the
Ångström exponent in both cities. The average PM2.5 mass
concentrations were 32 ± 32, 32 ± 24 and
28 ± 19 µg m−3 at traffic sites CT and AT and landfill
site AL, respectively. The domestic fire site shows a concentration of
145 ± 69 µg m−3 due to the contribution of smoking and
roasting activities. The highest OC and EC concentrations were also measured
at ADF at 71 ± 29 and 15 ± 9 µg m−3,
respectively, while the other sites present OC concentration between 8 and
12 µg m−3 and EC concentrations between 2 and
7 µg m−3. The OC ∕ EC ratio is 4.3 at CT and 2.0 at AT.
This difference highlights the influence of two-wheel vehicles using gasoline
in Cotonou compared to that of four-wheel vehicles using diesel fuel in
Abidjan. AOD was rather similar in both cities, with a mean value of 0.58 in
Cotonou and of 0.68 in Abidjan. The seasonal cycle is dominated by the large
increase in surface mass concentration and AOD during the long dry season
(December–February) as expected due to mineral dust advection and biomass
burning activities. The lowest concentrations are observed during the short
dry season (August–September) due to an increase in surface wind speed
leading to a better ventilation. On the other hand, the high
PM2.5 ∕ AOD ratio in the short wet season (October–November)
indicates the stagnation of local pollution
Microbiota-Derived Short-Chain Fatty Acids Promote the Memory Potential of Antigen-Activated CD8+ T Cells
Interactions with the microbiota influence many aspects of immunity, including immune cell development, differentiation, and function. Here, we examined the impact of the microbiota on CD8+ T cell memory. Antigen-activated CD8+ T cells transferred into germ-free mice failed to transition into long-lived memory cells and had transcriptional impairments in core genes associated with oxidative metabolism. The microbiota-derived short-chain fatty acid (SCFA) butyrate promoted cellular metabolism, enhanced memory potential of activated CD8+ T cells, and SCFAs were required for optimal recall responses upon antigen re-encounter. Mechanistic experiments revealed that butyrate uncoupled the tricarboxylic acid cycle from glycolytic input in CD8+ T cells, which allowed preferential fueling of oxidative phosphorylation through sustained glutamine utilization and fatty acid catabolism. Our findings reveal a role for the microbiota in promoting CD8+ T cell long-term survival as memory cells and suggest that microbial metabolites guide the metabolic rewiring of activated CD8+ T cells to enable this transition