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Modeling the Chemical Aging of Dust Particles

Atmospheric dust particles are an integral part of the Earth System and play an important role. (1) They interact with the Earth’s energy balance (2) they affect human health, and (3) they interact with anthropogenic air pollution. The latter, however, can change the physical (optical) and mineral (chemical) properties of natural dust particles, which in turn is important for (1) and (2). For instance, dust particles can significantly impact the energy balance through the absorption and scattering of shortwave radiation, as well as re-emission of long-wave radiation at characteristic wavelengths of the ra­diation spectrum in the atmosphere. But dust particles also have a broad range of impacts on the biosphere, marine productivity as well as human health. Dust represents a serious hazard for life, health, property, environ­ment and economy. On local scales, increased levels of particulate matter (PM) - in the Mediterranean often mainly containing dust - can decrease air quality which affects human health and marine productivity. Dust impacts on the environment are controlled by the balance between the emissions and the removal of the dust from the atmosphere as well as its chemical structur­ing during transportation in the atmosphere, which in turn controls removal processes. During transportation, dust can undergo chemical aging, i.e. dust particles become coated by e.g. anthropogenic air pollution (acids), which includes various heterogeneous surface reactions that strongly depend on the mineral composition of dust. This way, coated dust particles can not only transport both pollution from anthropogenic activities and disease agents across the world, aged (and humidified) dust particles often also have an increased ability to act as so-called cloud condensation nuclei, whereas their ice nucleating activity sometimes reduces, which is particularly important for cloud (ice) and rain formation.

Thus studying the role of anthropogenic air pollution on the chemical aging of dust particles and the resulting effects on human health and cli­mate is challenging. At The Cyprus Institute a high resolution (T255, 50 km grid box) atmospheric Chemistry General Circulation Model (EMAC) is used. The model configuration captures transport and deposition of aged dust particles and includes state-of-the-art gas and aqueous phase chemistry, the production processes of major aerosol precursor gases (acids) and partic­ulate matter, as well as major natural and anthropogenic emission sources.

The movie shows the aging of dust particles during transportation. The natural dust emission flux from the source regions, e.g. from the Sahara is indicated in yellow colors, while the color changes to green with increasing interaction with air pollution, e.g. from China to North America.

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For further information, please contact EEWRC: Mohamed Abdel Kader and Swen Metzger.