Environmental Engineering Reference
In-Depth Information
Figure 3.
Rates of anammox (filled grey symbols) and denitrification (open symbols) and the
concentration of hydrogen sulfide (dark grey line; bottom axis) in the anoxic water column of
Golfo Dulce. Diamonds and squares indicate two different stations A and B. Hydrogen sulfide
data is from station B. Anoxia was found from
∼
110 m at Station A and
∼
90 m at Station B.
Data from Dalsgaard et al. [11].
Dulce suggest that this process may also contribute substantially to the am-
monium and DIN deficiencies in oxygen deficient oceanic waters. The bay
provides an easily accessible model system for further studies of the process.
Mariager Fjord.
Mariager Fjord is a long and narrow fjord on the east
coast of Jutland, Denmark, which in its inner part harbors a small euxinic basin
known as Dybet (maximum depth 28 m). Stratification is occasionally disrupted
during winter, but then reestablishes during spring. Oxygen and hydrogen
sulfide usually meet at a sharp interface, but a “suboxic” zone low in both
these species is occasionally observed [22, 46, 83]. The suboxic zone may be
a non-steady-state phenomenon related to intrusions around the depth of the
chemocline, as indicated by day-to-day variations in chemocline structure [83].
Near the chemocline a small peak in NO
2
−
of
∼
1 µM may coexist with 10 - 20
µMNH
4
+
[83].
Investigations of anammox in the water column of Mariager Fjord in 2001
and 2002 did not find any clear evidence for the process in samples collected
across the chemocline [44]. Sampling was done with a pump system at a depth
resolution of 0.2 - 0.3 m. Denitrification rates exceeded 100 nM N
2
h
−
1
and
