Geoscience Reference
In-Depth Information
Table 3.6
Conductivity, concentration of dissolved matter and suspended matter in ice, snow and
water in four Finnish lakes (Lepp
ä
ranta et al. 2003b): oligotrophic Lake P
ä
ij
ä
nne, oligo-mesotrophic
Lake P
ää
j
ä
rvi, eutrophic Lake Vesij
ä
rvi, and hypereutrophic Lake Tuusulanj
ä
rvi
Lake
Conductivity
ʼ
S
cm
−
1
Dissolved
matter
mg l
−
1
Suspended matter
mg l
−
1
(organic
fraction)
pH Congelation
ice fraction
%
(at 25
°
C)
P
ä
ij
ä
nne
91.8
Ice
7.7
11.3
2.1 (23 %)
6.6
Snow
19.0
20.0
17.0 (50 %)
×
Water
78.7
31.3
1.4 (49 %)
7.0
P
ää
j
ä
rvi
69.0
Ice
13.0
14.3
2.1 (36 %)
6.7
Snow
16.5
15.0
4.2 (38 %)
×
Water
108.0
64.0
3.7 (40 %)
6.6
Vesij
ä
rvi
89.7
Ice
7.0
12.7
2.0 (33 %)
6.6
Snow
28.0
23.5
9.9 (54 %)
×
Water
128.3
52.3
1.1 (50 %)
7.0
Tuusulanj
ä
rvi
77.8
Ice
15.0
17.3
12.6 (24 %)
6.6
Snow
9.5
17.0
11.6 (58 %)
×
Water
208.3
143.0
11.5 (22 %)
6.8
The data show averages of the years 1997
-
1999
the liquid water. Congelation ice is typically much cleaner than the water from which it
forms whilst snow-ice can include impurities from the lake water and the parent slush.
When the ice melts, these impurities are released into the lake in a very short time. The
meltwater of clean congelation ice may then be less dense than the underlying lake water
due to its very low content of dissolved matter.
The concentration of a substance in lake ice can be formulated as
C ¼
c
C
ci
þ
1
c
ð
Þ m
C
s
þ
1
m
½
ð
Þ
C
w
ð
3
:
8
Þ
is the fraction of congelation ice,
m
1
=
2
where
is the fraction of snow in snow-ice, and
the subscripts w, s and ci refer to lake water and snow in snow-ice, and congelation ice.
The vertical distribution of impurities shows usually an increase in the snow layer
when snow ages, highest in old snow or snow ice, and congelation ice is clearly the
cleanest layer (Fig.
3.14
). The lake water shows much higher levels than snow or ice.
ʳ
Search WWH ::
Custom Search