Environmental Engineering Reference
In-Depth Information
(c)
p
,
p
-DDT, (d) chlorpyrifos, and (e) 1,2-dichlorobenzene. The depth of
mixing is 1 m.
6.23
3
The following data were obtained on the oxygen deficit (
Δ =
C
O
2
-
C
O
2
) in a pond with a surface aerator. Determine the mass
transfer coefficient for oxygen from the data.
Oxygen Deficit
t
(min)
(% of Saturation)
0
78
2
62
4
52
6
44
8
37
10
31
12
27
14
23
Note: d
Δ
/
d
t
=−
k
r
Δ
, and
k
r
=
k
L
a
for a surface aerator.
6.24
2
The absorption cross-section and actinide flux for the photolysis
ClNO
h
ν
−→
Cl
+
NO in air are given below:
σ
λ
i
(cm
2
/Molecule)
λ
i
(Photons/cm
2
s)
λ
i
(nm)
I
10.3
×
10
−
20
0
×
10
14
280
300
9.5
0.325
320
12.1
5.08
340
13.7
8.33
360
12.2
9.65
380
8.3
8.45
400
5.1
11.8
Determine the atmospheric half-life for ClNO.
6.25
2
In the surface waters of a natural lake, iron (Fe
2
+
) reacts with
hydroxide in an oxidation-precipitation reaction with a rate
−
r
oxdn
=
k
ox
[
Fe
2
+
][
O
2
(
aq
)
][
OH
−
]
2
and photochemically dissolves by reduction
with a rate
−
r
photo
=
k
photo
{
Fe
III
L
}
, where {Fe
III
L} is the concentration
of a ligand-bound Fe
III
on surfaces. If the lake volume is
V
and has a
volumetric flow rate of
Q
, obtain the steady-state concentration of Fe
2
+
in the lake.
6.26
2
Usinga16-Wlow-pressureHglampphotoreactoremittinglightat254nm,
a series of pesticides were subjected to photodegradation in distilled water.
The concentrations, absorbances, and quantum yields are given below:
Compound
φ
A
abs
C
(mol/L)
2.3
×
10
−
5
Atrazine
0.037
0.08
1.8
×
10
−
5
Simazine
0.038
0.059
1.0
×
10
−
5
Metolachlor
0.34
0.005
The emitted light intensity of the lamp was
I
0
=
7.1
×
10
−
8
einstein/L s. Estimate the half-lives of the pesticides in water.
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