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Amel Nouara (CEM team) will defend his thesis on: Thursday, September 26 at 11:00, Amphitheatre Océanomed (Luminy)

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  3. Amel Nouara (CEM team) will defend his thesis on: Thursday, September 26 at 11:00, Amphitheatre Océanomed (Luminy)

On the following topic: "Development of analytical tools for the quantification and isotopic study of organic compounds from biomass fires in the environment".
Thesis Director: Mr. Richard Sempéré, CNRS Research Director
Co-director: Mr. Christos Panagiatopoulos, CNRS Research Officer
 

Abstract :

Biomass burning (BB) pollution is a major concern for public health and also climate change as BB emissions increase significantly human cardiopulmonary diseases and affect the global terrestrial radiative budget. In order to improve our understanding on the origin and fate of compounds related to BB in the environment, we have developed new analytical methods (isotopic and chromatographic methods) allowing the detection and quantification of anhydrosugars (specific tracers of BB) as well as a broader panel of sugars in natural ecosystems. This research carried out on samples from the terrestrial and marine environment such as marine particulate organic matter (POM), marine high molecular weight dissolved organic matter (HMWDOM), and total suspended atmospheric particles (TSP). The first developed method allowed to perform for the first time compound specific isotopic measurements of individual sugars by EA-IRMS (δ13C) and/or EA-AixMICADAS (∆14C) after purification by preparative chromatography HPLC-RI. Our results showed the presence of anhydrosugars in the POM sample exhibiting isotopic signatures of δ13C levoglucosan = −27.2‰, and δ13C mannosan = −26.2‰, indicating an external terrestrial input to marine environment probably via atmospheric deposition. In addition, the radiocarbon signature of levoglucosan (∆14C levoglucosan = 33‰) from TSP sample indicates a modern age, suggesting its recent synthesis in the environment as it has the same isotopic signature with atmospheric CO2. The HPAEC-PAD chromatography is the second method developed in the frame of this study and provided a full analysis of 17-most abundant sugars found in natural environments. This method allowed for the first time the quantification of anhydrosucres in the marine POM and HMWDOM that represent 2% and 3% of total sugars detected, respectively. In a complementary study, the emissions from BB have been also studied in aerosols from the Eastern Mediterranean Sea by monitoring the annual variations of anhydrosugars. The results of this study highlight the important contribution of BB emissions (up to 13%) to organic carbon pool in the PM10 particles arriving in the Eastern Mediterranean. Finally, the methods developed in this study have shown their high potential to quantify and monitor the anhydrosugars including other sugars in natural environments. This research may be pursued by following the dynamics of anhydrosugars in the water column and sediment which will improve our knowledge about the fate and the origin of these compounds in the marine environment.

 

Keywords : Biomass burning, Anhydrosugars, Compound specific carbon isotope analysis (CSIA), EA-IRMS and EA-AixMICADAS, Preparative chromatography (HPLC-RI), Ionic chromatography (HPAEC-PAD)