Concepts from Chemical Reaction Kinetics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 247

Hence, J = 0.0081 s − 1 and t 1 / 2 = 85 s.Inthiscasesince I

i Δλ changeswiththezenith
angle, the rate constant varies diurnally and hence NO 2 decomposition by photolysis
also varies diurnally.

λ

5.10 ENZYME CATALYSIS
5.10.1 M ICHAELIS -M ENTEN K INETICS AND M ONOD K INETICS
A knowledge of the biochemical reaction kinetics will allow us to predict not only the
reaction rates but also the present and future concentrations of a pollutant involved

TABLE 5.8
Photolytic Rate Constants for Compounds in Air
and Water

Air Environment

J (s −1 )

Reaction

O 3 → O 2 + O ( 1 D ) 10 − 5 at 10 km, 10 − 3 at 40 km

NO 2 h −→ NO + O 0.008 (surface), 0.01 (30 km)

NO 3 h −→ NO + O 2

0.016

NO 3 h −→

NO 2 + O 0.19

CH 3 COCH 3 h −→ CH 3 + CH 3 CO 12.4 × 10 − 6

HCHO h −→ HCO + O

10.1 × 10 − 6

CO 2 h −→ CO + O 3 P 2.2 × 10 − 8

Water Environment

J (s −1 )

Compound

(PAHs)
Naphthalene 10 − 6

2.7 ×

2.8 × 10 − 4

Pyrene

2.6 × 10 − 4

Anthracene

4.4 × 10 − 5

Chrysene

(Pesticides)
Malathion 1.3 × 10 − 5

7.3 × 10 − 7

Sevin

2.0 × 10 − 4

Trifluralin

2.2 × 10 − 8

Mirex

8.0 × 10 − 7 Parathion

Source: Seinfeld, J.H. and Pandis, S.N. 1998. Atmospheric Chemistry and Physics of Air Pollution .
NewYork,NY:JohnWiley&Sons,Inc.;Finlayson-Pitts,B.J.andPitts,J.N.1986. Atmospheric
Chemistry . New York, NY: John Wiley & Sons, Inc.; Lyman, W.J. et al. 1982. Handbook of
Chemical Property Estimation Methods . New York: McGraw Hill Book Co.; Warneck, P.
1988. Chemistry of the Natural Atmosphere . NewYork: Academic Press.