CHAPTER 4 . Redox Processes in Anoxic Waters
Fig. 4.26. The effect of Mn on
the formation of products during the oxidation of H2S with
O2 in sea water (Zhang and
Millero 1993a)
25
20
! 1:: 15
:>
]
~ 10
5
o
-0- H2S
..... S~-V- S2~........ S~119
o
2
3
4
5
6
7
8
9
10
Time (h)
validity of the model was evaluated by comparing the model predictions with the experimental measurements of reactants and products. At low concentrations the overall oxidation of HS- with O 2 is given by (Zhang and Millero 1993b)
k
H 2 S + O 2 ~products (S03)
H 2 S0 3 + O 2 k2 ) products (S04)
The overall rate equations for H 2 S, SO;-, S20~-, SO~- are given by
d[H2S]1 dt = -kJlH2S)[02]- k3[H2S)[SO~-][02]
d[SO;- ]1 dt = k l [H 2 S][02]- k 2 [SO;-]2[02]112 - k3[H2S)[SO~-][02]
d[S20;-]1 dt = k3[H2S][SO~-][02]
d[S04 2-]1 dt = k 2 [SO;-]2[02]1/2
where til is the total concentration of i.
These rate equations have been integrated simultaneously to evaluate the values of
kl , k2 and k3 using the experimental time dependence concentrations of all the reactants and products. The experimentally measured concentrations of H 2 S, SO~-, S20~-,
and SO~- were found to be in good agreement with the model predictions up to reaction times of 80 hours (curves in Fig. 4.25). The values of k2 in sea water needed to fit