Geology Reference
In-Depth Information
PRODUCTION
LOSS
RO
2
CH
4
, HC
j(O
1
D)
j(HONO)
j(HCHO)
j(H
2
O
2
)
O
3
+ C
n
H
2n
j(ROOH)
j(RCHO)
j(H
2
O)
RADICAL - RADICAL
HO
2
+ HO
2
HO
2
+ RO
2
RO
2
+ RO
2
RADICAL - NO
x
OH + NO
2
HO
2
+ NO
2
RO + NO
→
Nitrate
RCO
3
+ NO
2
NO
CO
HO
2
OH
NO, O
3
Heterogeneous
P
L
Figure 9 The sources, interconversions and sinks for HO
x
(and ROx) in the tropo-
sphere
14
Table 2 Calculated fractional contribution of various photolysis rates to radical
production with altitude
j(O(
1
D))
þ
H
2
O
j(O(
1
D))
þ
CH
4
Altitude
j(Acetone)
j(H
2
O
2
)
j(HCHO)
Ground
0.68
0.0
Neg.
0.15
0.17
Mid-
troposphere
0.52
Neg.
0.03
0.20
0.25
Upper-
troposphere
0.35
0.02
0.1
0.25
0.28
Lower
stratosphere
0.40
0.1
0.25
0.1
0.15
Note: (Neg: Negligible).
relatively high concentration given its high reactivity. The hydroxyl
radical is ubiquitous throughout the troposphere owing to the widespread
nature of ozone and water. In relatively unpolluted regimes (low NO
x
)the
main fate for the hydroxyl radical is reaction with either carbon monoxide
or methane to produce peroxy radicals such as HO
2
and CH
3
O
2
, viz
OH
þ
CO
-
H
þ
CO
2
(2.11)
H
þ
O
2
þ
M
-
HO
2
þ
M
(2.12)