Environmental Engineering Reference
In-Depth Information
Table 2.2
(continued)
Element
Continental crusts
Granite
Basalt
Shale
Seawater
U
2.7
4.8
0.6
3.2
0.003
Br
2.5
1.3
3.6
6
65
Sn
2
3
1
6
0.000,8
As
1.8
1.5
2
6.6
0.003
Ge
1.5
1.5
1.5
2
0.000,06
Mo
1.5
2
1
2
0.01
W
1.5
2
1
2
0.000,1
8.8 × 10 7
Ho
1.5
1.9
1.1
1
10 7
Eu
1.2
1.5
0.8
1
4.6
×
Tb
1.1
1.5
0.8
0.9
10 7
Lu
0.8
1.1
0.6
0.7
4.8
×
10 7
Tm
0.25
0.3
0.2
0.25
5.2
×
I
0.5
0.5
0.5
1
0.06
Tl
0.45
0.75
0.1
1
<0.000,01
Cd
0.2
0.2
0.2
0.3
0.000,11
Sb
0.2
0.2
0.2
1.5
0.000,5
Bi
0.17
0.18
0.15
0.01
0.000,02
In
0.1
0.1
0.1
0.05
<0.02
Hg
0.08
0.08
0.08
0.4
0.000,03
Ag
0.07
0.04
0.1
0.1
0.000,04
Se
0.05
0.05
0.05
0.06
0.000,4
Au, Pt metals, Re and Te are less than 0.05 ppm in rocks and less than 0.000,01 ppm in seawater.
Inert gases He, N, Ar, Kr and Xe are not listed as they only occur in seawater at low concentrations
Krauskopf ( 1967 )
and is able to support rooted plants. The lower part of a weathering profile is called
saprolite 2 or the chemically rotted rock in situ.
Depending on the climatic regime that exists in a region where rocks or soils
continue to weather, the chemical transformations of mineral parent material are
affected by the complete or partial removal, or merely local translocation, of sol-
uble minerals and by the pH of the system. Rocks and soils consist largely of
silicate minerals. Their transformations to secondary minerals and solutes are rea-
sonably well known and documented. McBride ( 1994 ) summarises these weathering
environments as follows:
Strongly alkaline, confined environments : Smectite clays and other silica-rich
silicate minerals are formed and potassium, calcium and magnesium salts may
accumulate.
Moderately alkaline, weak-leaching environments : The most soluble by-products
of weathering are removed, such as the base metals and some of the silica, but
secondary clays as smectites and illites remain.
2 Ibid.
 
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