The work performed and main results achieved so far in project EPHEMERAL are:
In WP2
The development of a technique to detect individual organic radicals in the atmosphere is about half-way into reaching its objective. Two state-of-the-art proton transfer time-of-flight mass spectrometers (PTR-tof-MS, “FUSION”, Ionicon Analytik, Gmbh) were purchased and optimized. These instruments could not initially detect the radicals and a first series of optimization was performed to improve their performances. At the time of this report both instruments can detect RO2 radicals, including CH3O2 and other small alkyl RO2 that are important in the atmosphere. While their detection sensitivities are currently a factor 10 to 50 below the performances necessary to detect the radicals in the atmosphere, they are the first time-of-flight mass spectrometers able to detect these radicals, which already allows for innovative investigations in laboratory, such as in WP3. In addition, a PERCA/ECHAMP instrument was built in WP2, which is being used to quantify the concentrations of RO2 observed by the MS instruments (“calibrations”).
In WP1
Several classes of reactions of RO2, never or hardly studied previously, have already been studied. Their reactions with unsaturated compounds (alkenes) were studied for the first time at room temperature, and the first experimental rate coefficients for H-shift and cyclisation reactions for unsatured RO2, contributing to the formation of HOMS and aerosols, were determined. Studies of the effects of water vapor on the reactions of RO2 are about to begin.
In WP3
The uptake and reactions of RO2 with various surfaces were studied for the first time. The reactivity of these radicals towards some surfaces, in particular metals, was found to be very high and in competition with their gas-phase chemistry. This suggests that some current knowledge of the reactivity of these radicals, based on laboratory setups where metal surfaces are important, might be inaccurate.
In conclusion, while the major breakthrough set in the project’s objectives have not been reached yet, the progress made so far is about half way towards these objectives. Several major achievements have been made, both in term of instrument/technique development and in investigating radical reactions in laboratory, which should soon open some new perspectives on the reactivity of these radicals in the atmosphere.
