Biomass burning plays a pivotaI role on atmospheric chemistry by serving as a source of many important trace gases such as reactive compounds (CO, hydrocarbons, organic acids, NH3, NOx) , greenhouse gases (CO2, CH4, N2O), and of course combustion aerosols. This study is principally based on two types of measurements: (1) -Boreal in-plume composition above Canada (ABLE-3B carnpaign: The Arctic Boundary Layer Expedition)-; (2) -Analyses performed along ice cores coming from Greenland which provide a unique record of precipitation chemistry reflecting the atmospheric composition at the time of deposition. They indicate simultaneous enhancement of formic and acetic acids and the formation of ammonium formate . Such sporadic features were attributed to biomass burning events-. A comparison between (1) and (2) indicates a characteristic chemical evolution during the plume ageing. The main goal of this study is to explain the signature of boreal biomass burning in ice cores, and to discern chemical phenomena that govern the plumes ageing. We used a meteorological model, and developed a box model of gas phase and aqueous phase chemistry: we introduce a pH calculation of the clouds droplets, a new solver, and we update, modify, and complete the chemical mechanism. Our results show that air masses are transported from North America to Greenland on a typical time scale of 5 days, with any cloud event, and a chemical equilibrium is reached rapidly. Above Greenland, chemical species are incorporated in the aqueous phase. Aqueous chemistry has a negligible impact on our results, and the gas-water-ice phase transfer phenomena are mostly responsible for the difference in chemical signature between fire plumes and the ice core records. We explain how our model results were extrapolated to concentrations in ice. We determine important physico-chemical parameters related to the incorporation of chemical species in the ice.
