Geology Reference
In-Depth Information
Methods
Measurements of water chemistry
In the course of the experiment, water samples were
collected between April 2002 and December 2003
during the 5 - 8 campaigns, depending on the site.
A detailed hydrochemical study is beyond the
scope of this paper, hence only selected data are
presented. They concern springs that feed the tufa
precipitating streams and the stations located
directly above the place where tablets were
exposed. At the L
´ˇ
ky site only chemical compo-
sition of water directly feeding the waterfall was
taken into consideration.
The specific electrical conductance (SEC) and
pH were measured in the field using calibrated
equipment: a WTW product. Total alkalinity (as
bicarbonate HCO
3
) was determined using 0.05
molar HCl acid by Gran titration also in the field
immediately after sampling of water. Temperature
was read with a mercury thermometer. The resol-
ution was 0.02%, 0.01 and 0.1 8C for SEC, pH and
temperature, respectively. Chloride (Cl) contents
were determined by the method of Mohr, using
0.01 molar AgNO
3
within two days after sampling.
Concentration of other components - Ca, Mg, Na,
K, Li, SO
4
, Sr, Ba - was determined by inductively
coupled plasma-atomic emission spectroscopy
(ICP-AES) using a Perkin-Elmer product. Total
sulphur was calculated as sulphates. All laboratory
analyses were done at the AGH University of
Science and Technology in Krak
´
w. The total dis-
solved solids (TDS) were calculated by summing
concentrations of ions.
The PHREEQC Interactive program was used to
calculate the equilibria of water samples (Parkhurst
& Appelo 1999; Charlton & Parkhurst 2002).
Calcite saturation index (SI
calc.
) was applied as a
measure of equilibrium, according to the formula:
SI ¼ log(IAP/KT), where: IAP - Ion Activity
Product for ions forming minerals soluble in the
given water solution, calculated according to the
law of mass action for the given reaction; KT -
equilibrium constant for a given reaction.
in streams. The copper tablets were c. 75 40
0.7 or 1 mm, and had two holes, each 5 mm
across. The dimensions of each tablet were
measured with the precision of 0.1 mm and their
overall surface area was calculated. Before placing
in streams the tablets were dried up at 50 8C for
48 h and weighed with precision of 0.01 g.
The tablets were installed using steel nails, in
pairs containing copper and limestone ones. At
least two pairs were placed at each study site in
August 2002. One pair at each site remained there
until the end of the experiment (that is until
October 2003). The second pair was changed four
times a year, every three or four months on average.
At the Karw ´w site two pairs of tablets were
installed in the crest of the small tufa dam
(Karw
´
w dam point; Fig. 3a). Other two pairs
were placed on the vertical wall of a small cascade
a few metres downstream from the dam (Karw
´
w
cascade point; Fig. 3b). At the Z´zriv´ site only
one point was studied (Figs 2b & 3c). Two pairs
of tablets were installed on the horizontal part of
the tufa fan. Conversely, three points were selected
for tablet installation at both the L ´ˇky and H´j
sites. In L ´
ˇ
ky all the points were located on the
waterfall (Figs 2c & 3d). The first of them (L´ˇky
top point) was located in horizontal riverbed over
the waterfall about 2 m from the waterfall crest.
The subsequent points (L ´ˇky E and W) were on
the vertical walls of the waterfall. The water depth
at the L ´ˇky top point was between 6 - 10 cm. The
second point (L ´ˇky E) was flushed by water inten-
sely falling down, while the third one (L´ˇky W)
was supplied by a thin film of constantly flowing
water. The L ´ˇky E point was shaded by a vertical
cliff of older tufa and by trees, the L ´ˇky top only
by trees while L ´
ˇ
ky W facing to the south was
almost not shaded, even during the development
of canopy in late spring and summer. At the H
´
j
site the tablets were installed along the course of
a stream over a distance of more than 900 m
(Fig. 2d). The uppermost point was at the H
´
j
upper waterfall. Two pairs of tablets were installed
on the waterfall face, on a moss curtain that dips
at an angle of about 608 (Fig. 3e). The second
point was at the lower waterfall. Similarly to the
upper one, tablets were installed on its face
dipping at an angle of 808. The lowermost point -
H
´
j dam point - is located about 50 m downstream
from the lower waterfall. The two pairs of tablets
and one extra limestone tablet were placed there in
the inclined downstream-facing part of the dam
that is 0.7 m high (Fig. 3f, g).
Collected tablets were transported to the labora-
tory carefully packed to prevent any loss of tufa,
dried at 50 8C for 48 h and weighted again. A test
showed that subsequent drying in temperature of
85 8C
Measurement of tufa growth rate
Tablets made of limestone and copper were used
in the experiment. The limestone ones were made
of Givetian dark limestone from the vicinities of
Krak´w, South Poland, known as the D˛bnik
Limestone. It has low porosity and deep-grey to
black colour which allows recognizing easily
in the field if the tablet is covered with a freshly
deposited tufa. The tablets were approximately
80 40 8 mm in size. The faces of the tablets
were smoothed. A circular hole 5 mm across was
bored through each tablet to enable their fastening
throughout
next
12 h
did
not
cause
any
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