Recent progress in understanding physical and chemical properties of African and Asian mineral dust

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. <br></br> 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. <br></br> 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. <br></br> 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

Impact of Gobi desert dust on aerosol chemistry of Xi'an, inland China during spring 2009: differences in composition and size distribution between the urban ground surface and the mountain atmosphere

“…Hua dust samples mainly originated from Gobi plants. NO (Formenti et al, 2011;Jöckel et al, 2003;Seinfeld and Pandis, 1998), but the NO − 3 formation is about 10 times faster than that of SO 2− 4 (Rodhe et al, 1981;Vrekoussis et al, 2004Vrekoussis et al, , 2007. Field observation showed that ground surface levels of NO 2 and SO 2 are similar in inland China.…”

The concentration, source and deposition flux of ammonium and nitrate in atmospheric particles during dust events at a coastal site in northern China

“…The average concentration of Ca 2+ in Category 2 (0.43 ± 0.40 µmol m −3 ) was evidently higher than that in Category 1 (Ca 2+ : 0.17 ± 0.04 µmol m −3 ), implying the probable formation of CaSO 4 and/or Ca(NO 3 ) 2 and the release of NH 3 (gas). Moreover, except for 20080502, the remaining dust samples in Category 2 were transported from the desert relatively enriched with CaCO 3 (1-25 % in wt %) (Formenti et al, 2011). A positive correlation between NO − 3 and SO 2− 4 in Category 2 compared to a negative correlation in Category 1 also implied that the dust particles enriched with CaCO 3 in Category 2 might play an important role to form SO 2− 4 and NO − 3 .…”

Discernible rhythm in the spatio/temporal distributions of transatlantic dust

“…North of the Sahel, all along the western part of the Sahara, there are clusters of many dust sources (Formenti et al, 2011, and the reference therein). Some of these are quite localized but distributed throughout the Western Sahara.…”

“…Regions b and c occupy vast regions over northwest Africa. Additional source area is (f) the Bodélé depression, recognized as the most intense dust source in North Africa (Koren et al, 2006;Huang et al, 2010;Formenti et al, 2011) located in the south-central part of the Sahara.…”