« Artificial Wet Buffer Zone: Sink or Carbon Source/Balance sheet approach »

Il s'agit d'un rapport de stage

إنجليزي. Wetland provides important ecosystem services and store carbon dioxide but is also an important globalsource of GHG mainly carbon dioxide and methane- a potent greenhouse gas. In order to understandthe dynamics of carbon budget for our study area; Rampillon buffer zone is an artificially constructedwetland designed to capture the titled agricultural drainage located near Nangis in Seine-et-Marne inorder to improve the surface water quality. Quantifying and understanding the environmental drivers ofcarbon sequestration from the wetland is important in order to have a better understanding of thecurrent and the future GHG budget of aquatic systems and the global ecosystem as a whole. In thisstudy, we present the observation of carbon storage in sediment coming from agricultural drainage forthe year 2017-2018, carbon captured in the vegetation during the growing season of the year 2018,observation of total inorganic and total organic carbon dissolved in the water by continuousmeasurement via SCAN spectrophotometer since year 2014-2018, observation of CO2 fluxes by EddyCovariance tower installed at the site during the one full year or one full growing season of 2017 andmeasurement of methane fluxes by Automatic Chamber method done via four campaigns held fromMay 2014 to October 2015. We found that, wetland acts as higher carbon sink via sediment than thevegetation with 2.3±0.248t C- CO2 of Total Carbon added each year by sediment compared to only11.5kg C or 42.24kg CO2 eq via vegetation. Using Eddy Covariance tower to measure CO2 fluxes, wedetermined that the wetland is net carbon source with ~1005kg C- CO2 been released into theatmosphere annually; primarily correlated to ecosystem respiration during the winter indicating the roleof soil temperature, microbial activity and atmospheric pressure. Methane fluxes were measured byautomatic chamber during the four campaigns resulted in wetland being source of CH4 releasing 40.85kgCH4-C or 1021 kg CO2eq per year; we found distinct diurnal and seasonal pattern of flux rates withebullition acting as the dominant transport pathways contributing 89% of total emissions. We concludethat the temporal dynamics of methane emissions over the seasonal and diurnal times scales should notbe ignored. By studying all the compartments of an artificial wetland and calculating Net carbon budget,we can conclude that Rampillon since its construction i.e. in last 8 years, is a carbon sink with 2.3t C- CO2or 8.4t CO2eq net carbon being stored in the wetland every year with sediment being foremostdominant compartment whereas from Net gas budget; a carbon source with 12.6t CO2eq of carbondioxide and 1.02t CO2eq of methane gas fluxes emitted every year. Further studies are required toinvestigate many other factors in depth such as soil temperature, atmospheric pressure, relativehumidity, microbial activity, photosynthetically active radiation along with reducing the percentage ofuncertainties of each compartment to have much deeper understanding of the GHG contributi