CLImate relevant processing of Mineral Dust by volatile Organic compounds – CLIMDO

CLIMDO uses a combination of innovative laboratory experiments in a well-controlled and characterized environment (the state-of-the-art atmospheric simulation chamber CESAM at LISA (project coordinator) and advanced flow reactors and optical cells), the development of novel modelling schemes of both the reaction mechanisms and the resulting optical properties of mineral dust, and new simulations of the global direct radiative effect and SOA distribution.

The work carried out so far consists of
IMT-DOUAI (partner 2): The heterogeneous interaction of ethanedial with natural mineral dust and mineral oxides and carbonates was evaluated. The capture coefficients that we measured at the initial stage (initial capture coefficients) and after the long aging of the particles by GL (steady state capture coefficients). Our results indicate that ethanedial is strongly adsorbed on dust surfaces, with initial capture coefficients of the order of 0.01-0.4, and steady-state capture coefficients of the order of 10-6. . The sample of natural mineral dust with the highest absorption capacity came from the Gobi Desert and this sample was selected for the deepening phase, which is currently underway. In this context, we will study the impact of the concentration of glyoxal, relative humidity, solar radiation and temperature, on the capture coefficients. The expected results of glyoxal adsorption on Gobi dust will be provided to Partners 1 and 3 for further use in large-scale experiments and in the model respectively. The same approach will also be followed for the study of methylglyoxal with mineral dust.
LISA (partner 1): a doctoral thesis began in October 2020. Two sets of experiments in a simulation chamber (WP2) were carried out to evaluate the experimental protocol for the injection of particulate compounds and in the gas phase (February 2021) and to study the interactions between dust and ethanedial (May 2021). The analysis of these first observations is underway. The results, which are quite encouraging, support the idea that the lifetime of gaseous compounds is sufficient to assess their losses by heterogeneous reaction with dust. A dust injection protocol by size class has been put in place. Condensation of ethanedial on dust appears to occur under conditions of high relative humidity.
LSCE (partner 3): Ramiro Checa-Garcia's post-doctorate consisted in adding the chemistry of glyoxal to the INCA model (Interactions between Chemistry and Aerosols). Since Glyoxal is the degradation product of other chemical species, this step also involves reactions other than those producing glyoxal directly. It is therefore necessary to explore a set of chemically stable reagents. We carried out this work in 5 steps 1) Add the gas-phase reactions of the new species; 2) Check the code involving these reactions; 3) Change the aqueous phase to include more reactions and species; 4) Include heterogeneous chemistry reactions involving OSA; 5) Evaluate the heterogeneous chemistry at the surface of desert dust.

The exploitation of the results for glyoxal and the transfer of expertise between partners is underway
In 2022 we will also tackle the studies on methylglyoxal and we will also seek to publish the first results.

1. Ramiro Checa-Garcia et al., Impact of heterogeneous chemistry on the distribution of Glyoxal and Methylglyoxal in the troposphere, submitted to AS3.1 – Aerosol Chemistry and Physics (General Session), EGU General Assembly 2021
2. Paola Formenti et al., The CLImate relevant processing of Mineral Dust by volatile Organic compounds (CLIMDO) project, submitted to CL4.27 – Aeolian dust: initiator, player, and recorder of environmental change, EGU General Assembly 2021
3. Romanias et al. Glyoxal uptake on various mineral surrogates. a knudsen flow reactor study. presented to session CM 02 : INTERACTIONS BETWEEN DUSTS AND ATMOSPHERIC TRACE GASES: IMPACT ON ATMOSPHERE AND DUST SURFACE PROPERTIES, DUST 2021 | IV INTERNATIONAL CONFERENCE ON ATMOSPHERIC DUST
4. Antonia Zogka et al., Heterogeneous Interaction of Glyoxal with Gobi desert dust under simulated atmospheric conditions, presented to session CM 02 : INTERACTIONS BETWEEN DUSTS AND ATMOSPHERIC TRACE GASES: IMPACT ON ATMOSPHERE AND DUST SURFACE PROPERTIES, DUST 2021 | IV INTERNATIONAL CONFERENCE ON ATMOSPHERIC DUST

As emphasized in the Intergovernmental Panel for Climate Change (IPCC) Assessments Report 5, aerosols contribute the largest uncertainty to global radiative forcing budget estimates. The uncertainty stems largely from the lack of information related to global aerosol distributions, composition, and aging effects in the atmosphere, all of which affect aerosol radiative properties.
Of the two major categories of aerosols, natural and anthropogenic, natural aerosols remain the largest source of the uncertainty. This limits our capacity to measure and attribute total climate forcings. Without a firm understanding of total climate forcing, our ability to predict its evolution over time diminishes and limits the development of adaptation strategies for future climate change.
Aerosolized mineral dust is the largest single component of the global aerosol mass budget, making up nearly half of annual particle emissions to the atmosphere. Mineral dust aerosols influence the global climate through both direct interactions with radiation (scattering and absorbing in the visible and IR regions) as well as indirect interactions with radiation (by serving as cloud condensation nuclei (CCN) or ice nuclei (IN)). One potentially important aspect of dust aerosols is that they are able to uptake and heterogeneously react with gases. Henceforth, mineral dust may also play a significant but mostly unknown role in secondary organic aerosol (SOA) formation in the atmosphere.
In conclusion, the combination of the complex reaction pathways and processing mechanisms inherent to the dust/organic system is hampering our understanding of dust and organic aerosols on global climate.
Despite a great number of progresses on climate-relevant properties of mineral dust and SOA in these past ten years, including the work of members of this consortium, studies of the heterogeneous chemistry occurring between dust and organic species are sparse. There is a clear urgent need for new science driven by original approaches.
The CLImate relevant processing of Mineral Dust by volatile Organic compounds (CLIMDO) project tackles this under-explored science question by proposing the first comprehensive process-driven project addressing the reactivity of complex and realistic mineral dust/organic systems to better understand how dust and VOCs influence the global climate system.
CLIMDO will investigate the heterogeneous interaction of mineral dust with two of the most common organic SOA precursors: glyoxal and methylglyoxal from ubiquitous anthropogenic and biogenic sources, thought combination of innovative laboratory experiments in a well-controlled and characterized environment (the state-of-the-art atmospheric simulation chamber CESAM at LISA (project coordinator) and advanced flow reactors and optical cells), the development of novel modelling schemes of both the reaction mechanisms and the resulting optical properties of mineral dust, and new simulations of the global direct radiative effect and SOA distribution.
Results and data of CLIMDO will be disseminated through the European open-access EUROCHAMP-2020 datacentre hosted in France by the French national data centre AERIS, a pillar of the ACTRIS ERIC at the European level.