On the following topic: "Development of analytical tools for the quantification and isotopic study of organic compounds from biomass fires in the environment".
Thesis supervisor :Mr Richard Sempéré, CNRS Research Director
Co-director: Christos Panagiatopoulos, CNRS Research Fellow
Summary:
Pollution emitted by biomass burning (BB) remains a major public health and climate change issue, as it contributes significantly to increased cardiopulmonary disease in humans and affects the Earth's global radiation balance. In order to improve our understanding of the origin and fate of BB compounds in the environment, we have developed new analytical methods (isotopic & chromatographic) for detecting and quantifying anhydrosugars (BB-specific tracers) and a range of the most abundant sugars in natural ecosystems. This work was carried out using samples from the terrestrial and marine environment, such as marine particulate organic matter (POM), marine high molecular weight organic matter (HMWDOM) and total suspended particulate matter (TSP). The first method developed made it possible to carry out molecular-scale isotopic measurements of sugars by EA-IRMS (δ13C) and/or EA-AixMICADAS (∆14C) after their prior purification by HPLC-RI preparative chromatography. Our results showed the presence of anhydrosugars in marine POM with a terrestrial isotopic signature (δ13C levoglucosan = -27.2‰, and δ13C mannosan = -26.2‰), reflecting a terrestrial input of these sugars to the marine environment probably by atmospheric deposition. In addition, the radiocarbon signature of levoglucosan (∆14C levoglucosan = 33‰) from atmospheric TSP indicates recent production of this compound as it carries the isotopic signature of atmospheric CO2. HPAEC-PAD chromatography is the second method developed in this work for characterising 17 of the most-responsive simple sugars in natural ecosystems. This method enabled the first quantification of anhydrosugars in marine POM and HMWDOM, accounting for 2% and 3% of the total sugars detected respectively. BB emissions were also studied in aerosols from the eastern Mediterranean Sea by monitoring annual variations in anhydrosugars. The results of this study showed the high contribution of BB emissions (13%) to the pool of organic carbon in PM10 particles arriving in the eastern Mediterranean basin. Finally, the methods developed in this study have demonstrated their great potential for quantifying and monitoring the dynamics of BB-derived compounds in natural environments. These studies now need to be continued, in particular to improve our knowledge of the fate of anhydrosugars in the water column and in marine sediments (this compartment has never been studied) in order to understand the impact of BB emissions on the marine environment.
Keywords: Biomass fires, Anhydrosugars, Specific carbon isotope analysis (CSIA), EA-IRMS and EA-AixMICADAS, HPLC-RI preparative chromatography, HPAEC-PAD ion chromatography