223
Atmospheric Chemistry
Prospero (1999) has been monitoring the dust from Africa from stations in Barbados
and Miami for a number of years. The monthly inputs of dust at these stations from 1984
to 2004 are shown in Figure 5.47. The largest concentrations occur in the summer months.
The chemical concentrations of the elements in dust are shown in Figure 5.48 (Trapp,
Millero, and Prospero, 2010). The concentrations are similar at Miami and Barbados and to
the concentrations in upper crustal abundances (UCAs). The concentrations of Al and Fe
are the highest since they make up the major components of minerals. The concentrations
of total Fe are linearly related to the concentration of Mn in the dust (Figure 5.49). This is
similar to the ratio of Fe to Mn in minerals. The fractional concentrations of Fe throughout
the year correlate with the concentration of total dust (Trapp, Millero, and Prospero, 2010)
(see Figure 5.50). Sholkovitz et al. (2012) have recently synthesized the global aerosol data.
The fractional amounts of Fe (%) in dust were found to vary with the total dust in a hyperbolic way (Figure 5.51) (Trapp et al., 2010; Sholkovitz et al., 2012). They find that global- scale
data are all adequately described by a simple two- component mixing model. The Fe(%) is
2 0 0 4
2 0 0 2
2 0 0 0
1 9 9 8
1 9 9 6
1 9 9 4
1 9 9 2
1 9 9 0
1 9 8 8
1 9 8 6
1 9 8 4
0
10
20
30
40
50
60
70
Miami
Barbados
0
10
20
Miami (µg/m
3
)
Barbados (µg/m
3
)
30
40
Figure 5.47
The monthly mean dust concentrations at Miami and Barbados from 1984 to 2004. (From Trapp, J.M., Millero,
F.J., and Prospero, J.M., Geochem. Geophys. Geosyst., 11, 2000. With permission.)
U
Pb
Tl
Lu
Yb
Tm
Er
Ho
Dy
Gd
Eu
Sm
Nd
Pr
Ce
La
Ba
Cs
Sr
Rb
As
Ga
Zn
Cu
Co
Cr
Sc
Al
Li
10
–4
Abundance (µmol/g)
10
–3
10
–2
10
–1
10
0
10
1
10
2
Barbados
Miami
UCA
10
3
10
4
Be
V
Fe
Mn
Ni
Cd
Y
Figure 5.48
The chemical compositions of aerosols at Miami and Barbados compared to upper crustal abundances (UCAs).
(From Trapp, J.M., Millero, F.J., and Prospero, J.M., Geochem. Geophys. Geosyst., 11, 2000. With permission.)
Atmospheric Chemistry
Prospero (1999) has been monitoring the dust from Africa from stations in Barbados
and Miami for a number of years. The monthly inputs of dust at these stations from 1984
to 2004 are shown in Figure 5.47. The largest concentrations occur in the summer months.
The chemical concentrations of the elements in dust are shown in Figure 5.48 (Trapp,
Millero, and Prospero, 2010). The concentrations are similar at Miami and Barbados and to
the concentrations in upper crustal abundances (UCAs). The concentrations of Al and Fe
are the highest since they make up the major components of minerals. The concentrations
of total Fe are linearly related to the concentration of Mn in the dust (Figure 5.49). This is
similar to the ratio of Fe to Mn in minerals. The fractional concentrations of Fe throughout
the year correlate with the concentration of total dust (Trapp, Millero, and Prospero, 2010)
(see Figure 5.50). Sholkovitz et al. (2012) have recently synthesized the global aerosol data.
The fractional amounts of Fe (%) in dust were found to vary with the total dust in a hyperbolic way (Figure 5.51) (Trapp et al., 2010; Sholkovitz et al., 2012). They find that global- scale
data are all adequately described by a simple two- component mixing model. The Fe(%) is
2 0 0 4
2 0 0 2
2 0 0 0
1 9 9 8
1 9 9 6
1 9 9 4
1 9 9 2
1 9 9 0
1 9 8 8
1 9 8 6
1 9 8 4
0
10
20
30
40
50
60
70
Miami
Barbados
0
10
20
Miami (µg/m
3
)
Barbados (µg/m
3
)
30
40
Figure 5.47
The monthly mean dust concentrations at Miami and Barbados from 1984 to 2004. (From Trapp, J.M., Millero,
F.J., and Prospero, J.M., Geochem. Geophys. Geosyst., 11, 2000. With permission.)
U
Pb
Tl
Lu
Yb
Tm
Er
Ho
Dy
Gd
Eu
Sm
Nd
Pr
Ce
La
Ba
Cs
Sr
Rb
As
Ga
Zn
Cu
Co
Cr
Sc
Al
Li
10
–4
Abundance (µmol/g)
10
–3
10
–2
10
–1
10
0
10
1
10
2
Barbados
Miami
UCA
10
3
10
4
Be
V
Fe
Mn
Ni
Cd
Y
Figure 5.48
The chemical compositions of aerosols at Miami and Barbados compared to upper crustal abundances (UCAs).
(From Trapp, J.M., Millero, F.J., and Prospero, J.M., Geochem. Geophys. Geosyst., 11, 2000. With permission.)