Contributions of biomass/biofuel burning to organic aerosols and particulate matter in Tanzania, East Africa, based on analyses of ionic species, organic and elemental carbon, levoglucosan and mannosan

Atmospheric aerosol samples of PM_2.5 and PM₁₀ were collected at a rural site in Tanzania, East Africa, in 2011 during wet and dry seasons and were analysed for carbonaceous components, levoglucosan, mannosan and water-soluble inorganic ions. The contributions of biomass/biofuel burning to the organic carbon (OC) and particulate matter (PM) mass were estimated to be 46&ndash;52% and 87&ndash;13%, respectively. The mean mass concentrations of PM_2.5 and PM₁₀ were 28 ± 6 μg m⁻³ and 47 ± 8 μg m⁻³ in wet season, and 39 ± 10 μg m⁻³ and 61 ± 19 μg m⁻³ in dry season, respectively. Total carbon (TC) accounted for 16&ndash;19% of the PM_2.5 mass and 13&ndash;15% of the PM₁₀ mass. On average, 86 to 89% of TC in PM_2.5 and 87 to 90% of TC in PM₁₀ was OC, of which 67&ndash;72% and 63% was found to be water-soluble organic carbon (WSOC) in PM_2.5 and PM₁₀, respectively. We found that concentrations of levoglucosan and mannosan (specific organic tracers of pyrolysis of cellulose) well correlated with non-sea-salt potassium (nss-K⁺) (<i>r</i>² = 0.56&ndash;0.75), OC (<i>r</i>² = 0.75&ndash;0.96) and WSOC (<i>r</i>² = 0.52&ndash;0.78). The K⁺ / OC ratios varied from 0.06 to 0.36 in PM_2.5 and from 0.03 to 0.36 in PM₁₀ with slightly higher ratios in dry season. Mean percent ratios of levoglucosan and mannosan to OC were found to be 3&ndash;4% for PM_2.5 and PM₁₀ in both seasons. We found lower levoglucosan / K⁺ ratios and higher K⁺ / EC (elemental carbon) ratios in the biomass-burning aerosols from Tanzania than those reported from other regions. This feature is consistent with the high levels of potassium reported in the soils of Morogoro, Tanzania, suggesting an importance of direct emission of potassium by soil resuspension although K⁺ is present mostly in fine particles. It is also likely that biomass burning of vegetation of Tanzania emits high levels of potassium that may be enriched in plant tissues. The present study demonstrates that emissions from mixed biomass- and biofuel-burning activities largely influence the air quality in Tanzania

Observational evidence of strengthening of the Brewer-Dobson circulation since 1980

The change of the Brewer-Dobson circulation (BDC) over the period of 1980–2009 is examined through a combined analysis of satellite Microwave Sounding Unit (MSU/AMSU) lower stratospheric temperatures (TLS), ERA-Interim reanalysis data, and observed estimates of changes in ozone, water vapor, well-mixed greenhouse gases, and stratospheric aerosols. The MSU/AMSU-observed tropical TLS trend is first empirically separated into a dynamic component associated with the BDC changes and a radiative component due to the atmospheric composition changes. The derived change in the dynamic component suggests that the annual mean BDC has accelerated in the last 30 years (at the 90% confidence interval), with most of the change coming from the Southern Hemisphere. The annual mean Northern Hemisphere contribution to the acceleration is not statistically significant. The radiative component of tropical TLS trends is independently checked using observed changes in stratospheric composition. It is shown that the changes in ozone, stratospheric aerosols, well-mixed greenhouse gases, and water vapor make important contributions to the radiative component of tropical TLS trends. Despite large uncertainties in lower stratospheric cooling associated with uncertainties in observed ozone and water vapor changes, this derived radiative component agrees with the empirically inferred radiative component, both in terms of its average value and small seasonal dependence. By establishing a relationship between tropical residual vertical velocity at 70 hPa and TLS, we show that the relative strengthening of the annual mean BDC is about 2.1% per decade for 1980–2009, supporting the results from state-of-the-art chemistry-climate model simulations.United States. National Aeronautics and Space Administration (grant NNX13AN49G)United States. National Aeronautics and Space Administration (NNX14AB28G)United States. Department of Energy. Office of Science (grant DE-SC0010557)National Science Foundation (U.S.) (grant 1342810)National Science Foundation (U.S.) (grant 1461517

Assessing the accuracy of energy turbulent diffusion dispersion correlation in a porous two-fluid model dedicated to PWR core simulations

International audienceCATHARE is a 2-fluid thermal-hydraulic code, capable of simulating thermal and mechanical phenomena occurring in the primary and secondary circuits of Pressurized Water Reactor under a wide variety of accidental situations. One of the medium-term objectives of system code CATHARE-3 is modeling a PWR core at assembly scale to simulate various accidental situations such as the loss of coolant accident (LOCA) and steam line break accident. This requires the monophasic and two-phase models that adapted to the assembly scale. However, there exists 3D models for the whole core and sub-channel scale models, which have a certain degree of validation. For more macroscopic three-dimensional models, we only have global validations without local measurements, which is necessary for the validations of each closure law's separate effects. The objective of my PhD project is improving the sub-channel scale models and developing the assembly scale models in CATHARE-3 system code with the sub-channel scale simulations and experiments results

Seasonal variations of stable carbon isotopic composition and biogenic tracer compounds of water-soluble organic aerosols in a deciduous forest

To investigate the seasonal changes in biogenic water-soluble organic carbon (WSOC) aerosols in a boreal forest, aerosol samples were collected continuously in the canopy of a deciduous forest in northern Japan during 2009–2010. Stable carbon isotopic composition of WSOC (&amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;WSOC&lt;/sub&gt;) in total suspended particulate matter (TSP) exhibited a distinct seasonal cycle, with lower values from June through September (−25.5&amp;plusmn;0.5 &amp;permil;). This cycle follows the net CO&lt;sub&gt;2&lt;/sub&gt; exchange between the forest ecosystem and the atmosphere, indicating that &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;WSOC&lt;/sub&gt; likely reflects the biological activity at the forest site. WSOC concentrations showed the highest values in early summer and autumn. Positive matrix factorization (PMF) analysis indicated that the factor in which biogenic secondary organic aerosols (BSOAs) dominated accounted for ~40 % of the highest concentrations of WSOC, where BSOAs mostly consisted of α-/β-pinene SOA. In addition, primary biological aerosol particles (PBAPs) made similar contributions (~57 %) to the WSOC near the forest floor in early summer. This finding indicates that the production of both primary and secondary WSOC aerosols is important during the growing season in a deciduous forest. The methanesulfonic acid (MSA) maximum was also found in early summer and had a distinct vertical gradient with larger concentrations near the forest floor. Together with the similar vertical gradients found for WSOC and &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;WSOC&lt;/sub&gt; as well as the α-/β-pinene SOA tracers, our results indicate that the forest floor, including ground vegetation and soil, acts as a significant source of WSOC in TSP within a forest canopy at the study site

Sulforaphane induces adipocyte browning and promotes glucose and lipid utilization

Scope: Obesity is closely related to the imbalance of white adipose tissue storing excess calories, and brown adipose tissue dissipating energy to produce heat in mammals. Recent studies revealed that acquisition of brown characteristics by white adipocytes, termed “browning,” may positively contribute to cellular bioenergetics and metabolism homeostasis. The goal was to investigate the putative effects of natural antioxidant sulforaphane (1-isothiocyanate-4-methyl-sulfonyl butane; SFN) on browning of white adipocytes. Methods and Results: 3T3-L1 mature white adipocytes were treated with SFN for 48 h, and then the mitochondrial content, function, and energy utilization were assessed. SFN was found to induce 3T3-L1 adipocytes browning based on the increased mitochondrial content and activity of respiratory chain enzymes, whereas the mechanism involved the upregulation of nuclear factor E2-related factor 2/ sirtuin1/ peroxisome proliferator-activated receptor gamma coactivator 1 alpha signaling. SFN enhanced uncoupling protein 1 expression, a marker for brown adipocyte, leading to the decrease in cellular ATP. SFN also enhanced glucose uptake and oxidative utilization, lipolysis and fatty acid oxidation in 3T3-L1 adipocytes. Conclusion: SFN-induced browning of white adipocytes enhanced the utilization of cellular fuel, and the application of SFN is a promising strategy to combat obesity and obesity-related metabolic disorder