Environmental Engineering Reference
In-Depth Information
34
the Black Sea: 1 - Station 1; 2 - Station 2; 3 - Station 3 [36] and 4 - data from [93].
Figure 2.
Concentration and δ
S values of dissolved sulphide in water of the anoxic zone of
with elemental sulfur, thiosulfate, and sulfite is beyond the question [13].
Hydrogen sulfide produced during this reaction is substantially enriched in the
lighter sulfur [14 - 16]. However, it is totally unfounded to use the dispro-
portionation mechanism to explain the extremely light isotopic composition
of H 2 S in Black Sea waters. It suffices to remind the data obtained by Luther
[74], who had studied the distribution of sulfur species in sulfidic waters of
the Black Sea and did not reveal the presence of sulfite and thiosulfate. The
concentration of elemental sulfur in the sulfidic water was very low - less than
30 nM [74]. The higher S 0 concentrations (up to 65 nM) were found only in
the upper part of the Black Sea sulfidic zone, where, in contrast to deep waters,
active hydrogen sulfide oxidation occurs [74]. The combination of two factors
- less depleted in 34 S hydrogen sulfide and the higher rate of sulfate reduction
in the upper part of the sulfide zone (Table 2 and 4) - likely favors our view-
point on the inverse relationship between the SRR and δ
34 S-H 2 S rather than a
pronounced effect of the disproportionation. Our data indicating that hydrogen
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