Environmental Engineering Reference
In-Depth Information
The last step is to calculate the concentrations in each phase,
C
j
:
C
air
=
fZ
1
=
3.4
×
10
−
8
mol/m
3
,
C
water
=
fZ
2
=
9.4
×
10
−
5
mol/m
3
,
C
soil
=
fZ
3
=
1.7
×
10
−
3
mol/m
3
,
C
sediment
=
fZ
4
=
2.9
×
10
−
3
mol/m
3
.
We can now calculate the total moles of pyrene in each compartment,
m
j
:
m
air
=
C
air
V
air
=
205 mol,
m
water
=
C
water
V
water
=
658 mol,
m
soil
=
C
soil
V
soil
=
76 mol,
m
sediment
=
C
sediment
V
sediment
=
61 mol.
Thus, the largest fraction (65.8%) of pyrene is in water. The next largest fraction
(20.5%) resides in air. Both sediment and soil environments contain less than 10%
of pyrene each.
If there is inflow and outflow from the evaluative environment, and steady state
exists, we have to use a level II fugacity calculation. If
G
j
(m
3
/h) represents both the
inflow and outflow rates from compartment
j
, then the total influx rate
I
(mol/h) is
related to the fugacity:
I
j
G
j
Z
j
f
=
.
(3.22)
The concentrations are then given by
C
j
=
fZ
j
and mass by
m
j
=
C
j
V
j
. The total
G
j
C
j
, where
E
is the total emission rate (mol/h) from
the environment and
C
j
is the influent concentration (mol/m
3
)
in the stream.
=
+
influx rate is given by
I
E
E
XAMPLE
3.6 L
EVEL
II F
UGACITY
C
ALCULATION
For the environment consisting of 10
4
m
3
air, 1000 m
3
of water, and 1 m
3
sediment,
an air flow rate of 100 m
3
/h, a water inflow of 1 m
3
/h, and an overall emission rate
of 2 mol/h are known for pyrene. The influent concentration is 0.1 mol/m
3
in air and
1 mol/m
3
in water. Given
Z
values of 10
−
4
for air, 0.1 for water, and 1 for sediment,
calculate the concentration in each compartment.
Total influx
I
=
2
(
mol/h
)
+
100
(
m
3
/
h
)
0.1
(
mol/m
3
)
+
1
(
m
3
/
h
)
1
(
mol/m
3
)
=
13 mol/h. Fugacity
f
=
13
/
[
(
100
)(
10
−
4
)
+
(
1
)(
1
)
]=
13 Pa.
C
air
=
(
13
)(
0.0001
)
=
0.0013 mol/m
3
,
C
water
=
(
13
)(
0.1
)
=
1.3 mol/m
3
, and
C
sed
=
(
13
)(
1
)
=
13 mol/m
3
.
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