Abstract
Abstract. This paper presents a review of recently acquired knowledge on the physico-chemical properties of mineral dust from Africa and Asia based on data presented and discussed during the Third International Dust Workshop, held in Leipzig (Germany) in September 2008. Various regional field experiments have been conducted in the last few years, mostly close to source regions or after short-range transport. Although significant progress has been made in characterising the regional variability of dust properties close to source regions, in particular the mineralogy of iron and the description of particle shape and mixing state, difficulties remain in estimating the range of variability of those properties within one given source region. As consequence, the impact of these parameters on aerosol properties like optical properties, solubility, hygroscopicity, etc. – determining the dust impact on climate – is only partly understood. Long-term datasets in remote regions such as the dust source regions remain a major desideratum. Future work should also focus on the evolution of dust properties during transport. In particular, the prediction of the mineral dust size distribution at emission and their evolution during transport should be considered as a high-priority. From the methodological point of view, a critical assessment and standardisation of the experimental and analytical techniques is highly recommended. Techniques to characterize the internal state of mixing of dust particles, particularly with organic material, should be further developed.
Highlights
IntroductionThe most recent model estimates indicate that global mineral dust emissions by wind-driven erosion over arid and semiarid areas range between 1000 and 3000 Tg yr−1 (Zender et al, 2004; Cakmur et al, 2006; Textor et al, 2007), representing about half of the annual particle emission at the global scale (Forster et al, 2007)
The most recent model estimates indicate that global mineral dust emissions by wind-driven erosion over arid and semiarid areas range between 1000 and 3000 Tg yr−1 (Zender et al, 2004; Cakmur et al, 2006; Textor et al, 2007), representing about half of the annual particle emission at the global scale (Forster et al, 2007).The global dust belt, where dust sources are located, extends from the west coast of North Africa, through the Middle East, into Central Asia and covers the Sahara, the deserts of the Arabian Peninsula and of Oman, Caspian Sea and Aral Sea regions in Central Asia, and Gobi and the Taklimakan in China
We present a review of the current state of knowledge of the physico-chemical properties of mineral dust relevant to estimating its main impacts
Summary
The most recent model estimates indicate that global mineral dust emissions by wind-driven erosion over arid and semiarid areas range between 1000 and 3000 Tg yr−1 (Zender et al, 2004; Cakmur et al, 2006; Textor et al, 2007), representing about half of the annual particle emission at the global scale (Forster et al, 2007). As for any type of atmospheric aerosol particles, the environmental and climatic impacts of mineral dust depend on its physico-chemical properties, that is, composition, shape, surface state, size, and mixing state of the particles (Raes et al, 2000a). A meaningful comparison of measurements by techniques based on different principles (e.g., number size distribution measurements by optical and aerodynamical methods) requires the knowledge of additional physico-chemical properties (e.g., composition, particle density and shape; see Hinds (1999). Properties are not measured in parallel, assumptions have to be made to reconcile their measurements
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