On Composition, Morphology, and Size Distribution of Airborne Mineral Dust - Mineral Dust: A Key Player in the Earth System - page 16

Keywords Composition ￿ Mineralogy ￿ Chemistry ￿ Elements ￿ Isotopes ￿

Particle shape ￿ Particle morphology ￿ Single-particle analysis ￿ Radiative

forcing ￿ Size distribution

2.1 Introduction

Mineral dust is an omnipresent constituent of the Earth's atmosphere. It is mainly
uplifted in the large desert regions of the Earth and may be transported hundreds
to several thousand of kilometers around the globe. The uplift, transport, and
final deposition of mineral dust have severe consequences on climate and many
important ecosystems. One can distinguish between impacts in the source regions,
the atmosphere, and the zones of dust settlement, respectively.
Source regions of mineral dust are often affected by heavy dust storms coupled
with extremely high concentrations of particulate matter resulting in negative
health effects for the population, a degradation of visibility, damages to crops and
machinery, and the deflation and degradation of surface sediments (see Goudie and
Middleton 2006 , their Table 3.1).
The input of mineral dust into the atmosphere largely influences the radiative
budget of the Earth through absorption and scattering of the incoming solar and
outgoing terrestrial radiation (direct effect, e.g., Balkanski et al. 2007 ). Mineral dust
particles may also act as cloud condensation nuclei (CCN) or ice nuclei (IN) and
consequently will change in-cloud processes (see Chap. 12 , Rosenfeld et al. 2001 ;
Yin et al. 2002 ;DeMottetal. 2003 ; Toon 2003 ; Zimmermann et al. 2008 ; Koehler
et al. 2009 ; Kumar et al. 2011 ). The detailed characteristics and the extent of this so-
called indirect effect is a matter of intense research. During transport, mineral dust
will also inevitably react with other components including heterogeneous reactions
with trace gases which will in turn alter the chemical balance of the atmosphere
(Bauer et al. 2004 ). Especially calcium-rich dusts will partly buffer an elevated
acidity of the atmosphere and increase pH values of precipitation (e.g., Rodá et al.
1993 ; Cao et al. 2005 ; Ooki and Uematsu 2005 ).
In regions of dust settlement, several impacts are also observed, and many
terrestrial soils and marine surface sediments contain significant fractions of aeolian
material. Mineral dust may be also a carrier of different nutrients, and the supply of
iron and phosphorus to terrestrial and marine ecosystems will modify the primary
bio-productivity and finally the biogeochemical cycle in regions far apart from the
dust source regions (see Chap. 14 and, e.g., Swap et al. 1992 ; Jickells et al. 2005 ;
Mahowald et al. 2008b ; Paytan et al. 2009 ;Okinetal. 2011 ). On the other hand,
living microorganisms (including pathogens) are often carried along with mineral
dust which may cause diseases leading, for example, to the demise of coral reefs
(Shinn et al. 2000 ; Garrison et al. 2003 ; Griffin and Kellogg 2004 ). Furthermore,
the remaining size fraction of mineral dust after long-range transport will be
comparatively small and therefore may affect human health through inhalation and
transport deep into the lungs (see Chap. 15 , Prosperoetal. 2008 ; De Longueville
et al. 2010 ).