Les eaux continentales comme sources de gaz à effet de serre vers l’atmosphère : étude pilote dans 4 cours d’eau en Wallonie

audience: researcher, professional, student, popularizationLes eaux continentales (fleuves et lacs) sont d’importantes composantes des cycles globaux du carbone et de l’azote. Elles transportent du carbone et de l’azote organique et inorganique des écosystèmes terrestres vers les océans. Cependant, ce transport n’est pas passif et les eaux continentales produisent, dégradent, stockent et échangent du carbone et de l’azote avec l’atmosphère. Ainsi, les eaux continentales émettent du dioxyde de carbone (CO2), du méthane (CH4) et du protoxyde d’azote (N2O) vers l’atmosphère. Le CO2, CH4 et N2O sont les principaux gaz à effet de serre (GES) anthropiques, et le N2O est en plus le plus important agent anthropique de destruction de la couche d’ozone. L’Unité d’Océanographie Chimique a mené une étude pilote dans quatre cours d’eau à proximité de la ville Liège (Meuse, Ourthe, Geer et Ruisseau du Blanc Gravier) qui ont été étudiés afin de décrire la dynamique du CO2, CH4 et N2O et d’en estimer les flux émis des eaux de surface vers l’atmosphère. Les conditions ainsi que les résultats de l’étude seront présentés lors de cet exposé

Reconciling opposing views on carbon cycling in the coastal ocean: continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2

Despite their moderately-sized surface area, continental marginal seas play a significant role in the biogeochemical cycles of carbon, as they receive huge amounts of upwelled and riverine inputs of carbon and nutrients, sustaining a disproportionate large biological activity compared to their relative surface area. A synthesis of worldwide measurements of the partial pressure of CO2 (pCO2) indicates that most open shelves in the temperate and high latitude regions are under-saturated with respect to atmospheric CO2 during all seasons, although the low latitude shelves seem to be over-saturated. Most inner estuaries and near-shore coastal areas on the other hand are over-saturated with respect to atmospheric CO2. The scaling of air-sea CO2 fluxes based on pCO2 measurements and carbon mass balance calculations indicate that the continental shelves absorb atmospheric CO2 ranging between 0.33 to 0.36 Pg C yr-1 that corresponds to an additional sink of 27% to ~30% of the CO2 uptake by the open oceans based on the most recent pCO2 climatology (Takahashi et al., 2008; Deep-Sea Research II, this issue). Inner estuaries, salt marshes and mangroves emit up to 0.50 Pg C yr-1, although these estimates are prone to large uncertainty due to poorly constrained ecosystem surface area estimates. Nevertheless, the view of continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2 allows reconciling long-lived opposing views on carbon cycling in the coastal ocean

Nonextensive distributions of rotation periods and diameters of asteroids

Context. To investigate the distribution of rotation periods of asteroids from different regions of the Solar System and distribution of diameters of near-Earth asteroids (NEAs). Aims. Verify if nonextensive statistics satisfactorily describes the data. Methods. Light curve data was taken from Planetary Database System (PDS) with Rel $\ge 2$. Taxonomic class and region of the Solar System was also considered. Data of NEA were taken from Minor Planet Center. Results. The rotation periods of asteroids follow a $q$-Gaussian with $q=2.6$ regardless of taxonomy, diameter or region of the Solar System of the object. The distribution of rotation periods is influenced by observational bias. The diameters of NEAs are described by a $q$-exponential with $q=1.3$. According to this distribution, there are expected to be $994 \pm 30$ NEAs with diameters greater than 1 km.Comment: 5 pages, 4 figures; observational bias taken into account in the new versio

Methane, carbon dioxide and nitrous oxide emissions from two clear-water and two turbid-water urban ponds in Brussels (Belgium)

Shallow ponds can exist in a clear-water state dominated by macrophytes or a turbid-water state dominated by phytoplankton, but it is unclear if these two states affect differently carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions to the atmosphere. Two clear-water urban ponds (Silex and Tenreuken) dominated by macrophytes, and two turbid-water urban ponds (Leybeek and Pêcheries) dominated by phytoplankton, in the city of Brussels (Belgium), were sampled 46 times between June 2021 and December 2023 to measure the partial pressure of CO2 (pCO2), dissolved CH4 concentration, N2O saturation level (%N2O), and ancillary variables. CH4 ebullitive fluxes were also measured in the four ponds during 8 deployments, totally 48 days of cumulated measurements. The 13C/12C ratio of CH4 (δ13C-CH4) was measured in bubbles from the sediment and in water to decipher the pathway of sedimentary methanogenesis (acetoclastic or hydrogenotrophic) and quantify methane oxidation (MOX) in the water column. The pCO2 and CH4 values in the sampled urban ponds correlated with precipitation and water temperature, respectively. The %N2O values did not correlate with dissolved inorganic nitrogen (DIN) nor other variables for the individual ponds, but a positive relation to DIN emerged from the combined data-set for the four ponds. The sampled turbid-water and clear-water ponds did not show differences in terms of diffuse emissions of CO2 and N2O. Clear-water ponds exhibited higher values of annual ebullitive CH4 fluxes compared to turbid-water ponds, most probably in relation to the delivery to sediments of organic matter from macrophytes. At seasonal scale, CH4 fluxes between the surface of the ponds and the atmosphere exhibited a temperature dependence in all four ponds, with ebullitive CH4 fluxes having a stronger dependence to temperature than diffusive CH4 fluxes. The temperature sensitivity of ebullitive CH4 fluxes was different among the four ponds and decreased with increasing water depth. During summer 2023, hydrogenotrophic methanogenesis pathway seemed to dominate in clear-water ponds and acetoclastic methanogenesis pathway seemed to dominate in turbid-water ponds, as indicated by the δ13C-CH4 values of bubbles sampled by physically perturbing sediments. The δ13C-CH4 values of bubbles sampled during bubble trap deployments in 2021–2023 indicated a seasonal shift to hydrogenotrophic methanogenesis pathway in fall compared to spring and summer, when acetoclastic methanogenesis pathway seemed to dominate. The δ13C-CH4 of dissolved CH4 indicated higher rates of MOX in turbid-water ponds compared to clear-water ponds, with an overall positive correlation with total suspended matter (TSM) and Chlorophyll-a (Chl-a) concentrations. The presence of suspended particles putatively enhanced MOX by reducing light inhibition of MOX and/or by serving as substrate for fixed methanotrophic bacteria in the water column. Total CH4 emissions in CO2 equivalents either equalized or exceeded those of CO2 in most ponds, while N2O emissions were negligible compared to the other two greenhouse gases (GHGs). Total annual GHG emissions in CO2 equivalents from all four ponds increased from 2022 to 2023 due to higher CO2 diffusive fluxes, likely driven by higher annual precipitation in 2023 compared to 2022, possibly in response to the intense El Niño event of 2023

Full Paper: Rapid Production of Enterprise Applications in a Low-Code Environment: Comparing the Itlingo-ASL and Powerapps Metamodels

Low-code development platforms allow to reduce the time and resources required for developing business applications; thus, many companies are increasingly adopting them. However, they often use proprietary languages making it challenging to interoperate with other systems or switch to different low-code platforms, resulting in vendor lock-in situations. This research proposes to combine a model-driven approach based on rigorous requirements specifications defined in the ITLingo-ASL language with the Microsoft PowerApps technology to generate quasi-complete enterprise applications semi- automatically. This research analyses the ITLingo-ASL and Microsoft PowerApps metamodels, mainly focusing on concepts related to DataEntities, UI elements, Actors and Use cases to find similarities indicating that transforming one model is possible. It also pinpoints differences so that the ITLingo-ASL language can be extended to support software enterprise application specifications better

Size matters: tissue size as a marker for a transition between reaction-diffusion regimes in spatio-temporal distribution of morphogens

The reaction-diffusion model constitutes one of the most influential mathematical models to study distribution of morphogens in tissues. Despite its widespread use, the effect of finite tissue size on model-predicted spatio-temporal morphogen distributions has not been completely elucidated. In this study, we analytically investigated the spatio-temporal distributions of morphogens predicted by a reaction-diffusion model in a finite one-dimensional domain, as a proxy for a biological tissue, and compared it with the solution of the infinite-domain model. We explored the reduced parameter, the tissue length in units of a characteristic reaction-diffusion length, and identified two reaction-diffusion regimes separated by a crossover tissue size estimated in approximately three characteristic reaction-diffusion lengths. While above this crossover the infinite-domain model constitutes a good approximation, it breaks below this crossover, whereas the finite-domain model faithfully describes the entire parameter space. We evaluated whether the infinite-domain model renders accurate estimations of diffusion coefficients when fitted to finite spatial profiles, a procedure typically followed in fluorescence recovery after photobleaching (FRAP) experiments. We found that the infinite-domain model overestimates diffusion coefficients when the domain is smaller than the crossover tissue size. Thus, the crossover tissue size may be instrumental in selecting the suitable reaction-diffusion model to study tissue morphogenesis.Fil: Ceccarelli, Alberto Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Borges, Augusto. Helmholtz Zentrum München; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Chara, Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Universidad Argentina de la Empresa; Argentina. Technische Universität Dresden; Alemani