Environmental Engineering Reference
In-Depth Information
pyrite forms in the upper part of the anoxic zone (below to 200 m) [12, 51, 58],
whereas others have argued that the zone of pyrite formation in the water column
is wider and may take place down to 1000-1500 m water depth [88]. Mass-
balance calculation by Neretin et al. [64] suggested that only about 10-50%
of the sulphur buried in sediments may come from the syngenetic component.
The magnitude of the particulate sulphur flux in the Black Sea water column is
in the range of 0.1-0.5 Tg yr
−
1
[58, 88].
Figure 11.
Sulphur budget for the Black Sea anoxic zone. The width of arrows and dimension
of boxes represent the relative magnitudes of respective processes. SMMW stands for “Shelf
Modified Mediterranean Water”. Processes rates are in Tg yr
−
1
[64].
10. CONCLUSIONS
A general scheme of the processes within the sulphur cycle as discussed
above and with their assigned annual fluxes is presented in Fig. 11. Hydrogen
sulphide inventory and the location of the upper sulphide boundary is a delicate
balance between complex physical and biological processes. Among them are
ventilation of the Cold Intermediate Layer (CIL), the entrainment ratio between
CIL and the Modified Lower Bosporus waters, and the rates of organic matter
respiration processes, specifically oxygen consumption in the oxic zone. If the
