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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