Molecular characterization of gaseous and particulate phases of primary and secondary biomass burning emissions and understanding of their toxicity

About this position

Knowledge of particulate matter (PM) in ambient air is essential to assess health and climate impacts of air pollution. Their sources, formation processes and chemical composition are still poorly known. Biomass burning accounts for a significant part of the primary emissions of fine PM in ambient air notably in winter period due to wood combustion used for residential heating purposes.

This source also emits large quantities of volatile and semi-volatile organic species leading to the formation, via (photo-)chemical processes, of secondary organic aerosols (SOA) accounting for a substantial part of fine PM concentrations. However, SOA formation yields from this source, or from the corresponding SOA precursors emitted, are still poorly documented in the literature especially for night-time processes (involving nitrate radical). Moreover, the toxicological potential of primary and aged biomass burning emissions, or related SOA, is also poorly understood and notably the links between biological responses and particle physicochemical properties.

In this context, the main objectives of this post-doctoral work are to study and understand the SOA formation processes from residential wood-burning appliance emissions (logwood stove) (WOODNIGHT project). To do so, logwood stove emissions have been aged using an oxidant flow reactor (OFR) under different oxidation conditions (OH or NO3 radicals), simulating the diurnal and nocturnal atmospheric processes. A detailed physicochemical characterization of the gaseous and particulate phases has been carried out.

The implementation of advanced instrumentation such as a CI-ToF-MS (Chemical Ionization - Time of Flight-Mass Spectrometry), combining several ionization modes (H3O+, O2+, I-) and aerosol analysis modules (e.g., EESI - Extractive ElectroSpray Ionization or CHARON - CHemical analysis of AeRosol ON-line) permitted to determine and measure, at a molecular level, volatile and semi-volatile organic substances in real time. This allows the study of the primary particle emission and secondary formation dynamics from the wood log stove emissions, obtained under conditions as representative as possible of a common use. In parallel, as part of the WOODTOX-ALI project, exposures to primary and aged logwood emissions of pulmonary cells at the air-liquid interface (ALI) have been conducted.

The analysis of potential links between the detailed physicochemical characterization of the gaseous and/or particulate phases and the biological responses obtained in complementary studies will be carried out.

Your mission will focus on the following priorities:

• Analyze the data obtained by CI-ToF-MS + EESI and PTR-MS + CHARON and interpret the results obtained depending on the combustion and aging conditions.
• Link these results with those obtained from other instrumentation, samplings and analyses (e.g. SMPS, AMS/ACSM, gas analyzers, etc.).
• Participate in the study of the links between physicochemical characterization with toxicological responses.
• Present results at scientific meetings and during international scientific conferences. Valorize the results through research project reports and publish them in peer-reviewed literature.