Environmental Engineering Reference
In-Depth Information
TABLE 4.10
A Typical Louisiana Sediment/Soil Composition
Component/Property
Sediment
Soil
Bulk density (g/cm
3
)
1.54
1.5
Particle density (g/cm
3
)
2.63
Bed porosity (cm
3
/cm
3
)
0.59
0.4
Organic carbon,
φ
oc
(humics, fulvics, etc.) (%) 2.1 2.3
Sand (%) 27 57.8
Silt (%) 37 25.5
Clay (%) 34 16.7
Iron (g/kg) 13 23
Aluminum (g/kg) 12 25
Calcium (g/kg) 3 1
Magnesium (g/kg) 2 0.4
Manganese (mg/kg) 206 100
Phosphorus (mg/kg) 527 166
Zinc (mg/kg) 86 54
Sodium (mg/kg) 77 29
Lead (mg/kg) 56 35
Chromium (mg/kg) 20 23
Copper (mg/kg) 17 20
Nickel (mg/kg) 12 15
Note:
Sediment sample obtained from Bayou Manchac, LA. Soil sample obtained from
North Baton Rouge, Louisiana.
E
XAMPLE
4.13 F
LUX OF
Hg
0
IN THE
E
NVIRONMENT
In the equatorial Pacific Ocean, Kim and Fitzgerald (1986) reported that the principal
species of mercury in the atmosphere is elemental Hg
0
. It was shown that a significant
fraction of the dissolved mercury in the surface water was elemental Hg
0
. The con-
centration in the surface water,
C
i
w
, was 30 fM
(
=
30
×
10
−
15
mol/L
=
6 ng/m
3
)
. The
mean atmospheric concentration was 1 ng/m
3
. The Henry's constant at 25
◦
C for Hg
0
is 0.37. The overall mass transfer coefficient
K
w
=
5.1 m/day. The flux of Hg
0
is there-
foregivenby
J
Dry
(
G
)
=
5.1
[
1
/
0.37
−
6
]=−
16.8 ng/m
2
/day.TheannualfluxofHg
0
is
given by
−
16.8
×
365
=−
6.1
×
10
3
ng/m
2
=−
6.1
μ
g/m
2
. The flux is negative, and
hence is directed from the ocean to the atmosphere. The total flux from 1.1
×
10
13
m
2
surface area of the equatorial Pacific Ocean is 0.67
×
10
8
g/year. The total flux of Hg
0
to air from all regions of the world combined is 8
×
10
9
g/year. Hence, the flux from
the equatorial Pacific Ocean is only 0.08% of the total.
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