Environmental Engineering Reference
In-Depth Information
the western part than in the eastern part. Recent detailed studies have shown
that not only the thermohaline characteristics, but also concentrations of sev-
eral chemical species in bottom waters below 1670 m are uniform, and like
thermohaline characteristics independent of a geographical location. The av-
erage concentrations of some chemical species and alkalinity in the bottom
convective layer measured in the period from 1999 to 2002 are given in Table
2.
Table 2.
Hydrochemical characteristics of the bottom convective layer of the Black Sea during
1999-2002.
1999:
2000:
2001:
2002:
Depth
≥
1750 m
Depth
≥
1750 m
Depth
≥
1750 m
Depth
≥
1650-
7 stations
5 stations
7 stations
1800 m
7 stations
pH
n.d.
n.d.
7.42
−
7.67 (34)
n.d.
7.52
±
0.06 (0.8%)
−
−
−
Alk, µM
4419
4530 (19)
4400
4529 (18)
4375
4551 (32)
n.d.
4478
±
33 (0.7%)
4485
±
44 (1.0%)
4450
±
45 (1.0%)
367-379 (26)
∗
H
2
S, µM
375-385 (18)
369-381 (34)
368-400 (36)
376
±
3(0.9%)
380
±
3(0.7%)
376
±
3(0.9%)
376
±
6(1.7%)
NH
4
+
, µM
n.d.
n.d.
85
.
8
−
100
.
6 (24)
n.d.
94.4
±
4.0(4.3%)
SiO
3
2
−
, µM
n.d.
n.d.
321
−
335 (35)
n.d.
330
±
3(1.0%)
Mn
2
+
, µM
n.d.
n.d.
4.0
−
4.3 (27)
n.d.
4.1
±
0.1(2.0%)
CH
4
, µM
n.d.
n.d.
11.8
−
13.4 (29)
n.d.
12.5
±
0.4(3.4%)
Note:
∗
367
−
379 (26)
- numerator: range (number of measurements)
376
±
3(0.9%)
- denominator: mean
±
standard deviation (coefficient of variability)
A transport between the bottom convective layer and the overlying waters
occurs via a single diffusive interface. A destabilizing geothermal heat flux at
the bottom acts against stable salinity stratification resulting in double diffusion
[60, 67]. It is the main mixing mechanism in bottom waters of the Black Sea.
Mixing inside the bottom convective layer occurs on a scale of about 40 yrs [69].
Interestingly enough, the bottom convective layer in the Black Sea covering
