502
Chemical Oceanography, 4th Edition
Yao and Millero (1995) examined how the oxidized products of Fe 2+ and Mn 2+ that occur
above the anoxic–oxic interface can oxidize hydrogen sulfide and complete the redox cycle
of these metals in anoxic waters (Figure 10.87). These reactions are much more complicated since they occur on the surfaces of the oxide minerals. The rates of oxidation of H 2 S
by Mn(IV) and Fe(III) (hydr)oxides in the water near the interface (~21 m) were determined and compared with the values obtained in the surface waters of the Gulf Stream
(Figure 10.88) in the laboratory. The agreement is quite good. The slightly higher oxidation rates observed in the field might be related to the microbiological activities near
the interface.
References and Further Reading
Photochemistry
Bielski, B.H.J., Re- evaluation of the spectra and kinetics properties of HO 2 and O 2
– free radicals,
Photochem. Photobiol., 38, 450 (1978).
Heltz, G.R., Zepp, R.G., and Crosby, D.G., Aquatic and Surface Photochemistry, Lewis, Boca Raton, FL (1994).
King, D.W., Lounsbury, H.A., and Millero, F.J., Rates and mechanism of Fe(II) oxidation at nanomolar
total iron concentrations, Environ. Sci. Technol., 29, 818 (1995).
Millero, F.J., Estimate of the life time of superoxide in seawater, Geochim. Cosmochim. Acta, 51, 351 (1987).
Moffett J.W., and Zafiriou, O.C., An investigation of hydrogen peroxide chemistry in surface waters
of Vineyard Sound with H 2
18 O 2 and 18 O 2 , Limnol. Oceanogr., 35, 1221 (1990).
Moffett, J.W., and Zika, R.G., Measurement of copper (I) in surface waters of the subtropical Atlantic
and Gulf of Mexico, Geochim. Cosmochim. Acta, 52, 1849 (1988).
Mopper, K., and Zhou, Z., Hydroxyl radical photoproduction in the sea and its potential impact on
marine processes, Science, 250, 661 (1990).
log k (M
–1
min
–1
)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
MnO 2
Fe(OH) 3 (s)
αFeOOH
Waters near O 2 /H 2 S interface (S = 21‰)
Surface waters of Gulf Stream (diluted to S = 21‰)
Figure 10.88
Comparison of the rates of oxidation of H 2 S by Mn(IV) and Fe(III) (hydr)oxides in the Framvaren Fjord and
laboratory measurements.
Chemical Oceanography, 4th Edition
Yao and Millero (1995) examined how the oxidized products of Fe 2+ and Mn 2+ that occur
above the anoxic–oxic interface can oxidize hydrogen sulfide and complete the redox cycle
of these metals in anoxic waters (Figure 10.87). These reactions are much more complicated since they occur on the surfaces of the oxide minerals. The rates of oxidation of H 2 S
by Mn(IV) and Fe(III) (hydr)oxides in the water near the interface (~21 m) were determined and compared with the values obtained in the surface waters of the Gulf Stream
(Figure 10.88) in the laboratory. The agreement is quite good. The slightly higher oxidation rates observed in the field might be related to the microbiological activities near
the interface.
References and Further Reading
Photochemistry
Bielski, B.H.J., Re- evaluation of the spectra and kinetics properties of HO 2 and O 2
– free radicals,
Photochem. Photobiol., 38, 450 (1978).
Heltz, G.R., Zepp, R.G., and Crosby, D.G., Aquatic and Surface Photochemistry, Lewis, Boca Raton, FL (1994).
King, D.W., Lounsbury, H.A., and Millero, F.J., Rates and mechanism of Fe(II) oxidation at nanomolar
total iron concentrations, Environ. Sci. Technol., 29, 818 (1995).
Millero, F.J., Estimate of the life time of superoxide in seawater, Geochim. Cosmochim. Acta, 51, 351 (1987).
Moffett J.W., and Zafiriou, O.C., An investigation of hydrogen peroxide chemistry in surface waters
of Vineyard Sound with H 2
18 O 2 and 18 O 2 , Limnol. Oceanogr., 35, 1221 (1990).
Moffett, J.W., and Zika, R.G., Measurement of copper (I) in surface waters of the subtropical Atlantic
and Gulf of Mexico, Geochim. Cosmochim. Acta, 52, 1849 (1988).
Mopper, K., and Zhou, Z., Hydroxyl radical photoproduction in the sea and its potential impact on
marine processes, Science, 250, 661 (1990).
log k (M
–1
min
–1
)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
MnO 2
Fe(OH) 3 (s)
αFeOOH
Waters near O 2 /H 2 S interface (S = 21‰)
Surface waters of Gulf Stream (diluted to S = 21‰)
Figure 10.88
Comparison of the rates of oxidation of H 2 S by Mn(IV) and Fe(III) (hydr)oxides in the Framvaren Fjord and
laboratory measurements.