『Abstract
The deposition of aeolian, or windblown, dust is widely recognized
as an important physical and chemical flux to ecosystems. Dust
deposition adds exogenous mineral and organic material to terrestrial
surfaces and can be important for the biogeochemical cycling of
nutrients. There have been many studies that characterize the
physical and chemical composition of dust. However, few studies
have synthesized these observations in order to examine patterns
geochemical fluxes. We have compiled observations of dust deposition
rates, particle size distribution (PSD), mineralogy and bulk elemental
and organic chemistry.
The rates of dust deposition observed across the globe vary from
almost 0 to greater than 450 g m-2 yr-1.
Sites receiving dust deposition can be partitioned into broad
categories based on there distance from dust source regions. when
compared to global dust models our results suggest some models
may underestimate dust deposition rates at the regional and local
scales. The distance from the source region that dust is deposited
also influences the particle size distributions, mineralogy, and
chemical composition of dust; however, more consistent dust sampling
and geochemical analyses are needed to better constrain these
spatial patterns. On average, the concentrations of most major
elements (Si, Al, Fe, Mg, Ca, K) in aeolian dust tend to be similar
(±20%) to the composition of the upper continental crust (UCC),
but there is substantial variability from sample to sample. In
contrast, some elements tend to be depleted (Na) or enriched (Ti)
in dust, likely as a result of soil weathering processes prior
to dust emissions. Trace elements, especially heavy metals, are
consistently enriched in dust relative to the UCC. Ecologically
important nutrients, such as N and P, are also present in dust
deposition. The geochemical flux attributable to dust deposition
can be substantial in ecosystems located proximal to dust source
regions. We calculate estimates of elemental flux rates based
on the average chemical composition of aeolian dust and varying
rates of deposition. These estimated flux rates are useful as
a rough gauge of the degree to which dust deposition may influence
biogeochemical cycling in terrestrial ecosystems and should be
utilized to better constrain deposition estimates of global dust
models.
Keywords: Aeolian dust; Modeling; Atmospheric deposition; Particle
size distribution; Mineralogy; Trace-metals; Elemental chemistry』
1. Introduction
2. Background: the global dust cycle
2.1. Source areas and global budget
2.2. Emission
2.3. Transport
2.4. Deposition
2.5. Dust geochemical characteristics
3. Methods
3.1. Dust deposition rates
3.2. Dust chemistry, mineralogy, and particle size
4. Results
4.1. Rates of deposition
4.2. Particle size distribution
4.3. Mineralogy
4.4. Dust chemistry
5. Discussion
5.1. Deposition rate
5.2. Particle size
5.3. Mineralogy
5.4. Chemistry
5.5. Rates of chemical flux
5.6. Modeling dust depositions
6. Conclusions
Acknowledgements
References