Summary
Data
on water chemistry including heavy metals concentrations of the Lužnice River
basin and its principal tributaries in the years 1986 to 1999 have been
summarised on the basis of analyses conducted by the Faculty of Agronomy,
University of South Bohemia and by the Povodí Vltavy, a.s. Company.
Average
content of selected chemical characteristics at the Pilař profile (river km
117) in the years 1986 to 1998 are presented as follows (in mg per litre): Na+
- 15.7; K+ - 7.0; Mg2+ - 4.2; Ca2+
- 19.2; SO42- - 37.9; Cl- - 20.2; NO3-
- 11.8; P tot. – 0.15. Ca2+ represent prevailing cations, followed
by Na+, K+, and Mg2+ with the dominating anion
SO42-. Chemical composition, as to tributaries, water
chemistry is similar, however, the content of Mg2+ is generally
higher that those of K+ here. The water in the Lužnice River shows
low mineralization at its upper water shed, significant increase in the
contents of practically all chemical components occurs in the area of Alt
Weitra-Krabonoš (river km 165 to 147). The obvious sources of pollution seem to
be the agriculture and wastewaters of Alt Weitra village and the agglomeration
of Gmünd
- Č.Velenice. In the territory of the Czech Republic the Na+, K+,
Cl-, and P contents decreases, the SO42-
contents slightly increases, the contents of the other components varies around
the average values which seem to be fairly constant. Also the average values in
the individual years vary around the mean values, only the values for
phosphorus content were slightly decreasing till the end of 1997 whereas in
1998 a more significant increase of the total phosphorus occurred, the contents
of Na and Mg increases slightly.
Average
concentrations of heavy metals were the following in the Pilař profile between
1986 and 1994 (in µg.l-1 i.e. in ppb): Pb – 0.47,
Cd - 0.16, Cu - 2.3, Mn
- 110, Fe - 736, Zn - 19, Ni –
2.9, Co – 1.5, Cr – 1.0. The highest heavy metals contents change along the
Lužnice River is again between the kilometres 165 and 147, where the contents
of practically all heavy metals increase significantly. On the Czech territory
the Cu, Cr and Fe contents slightly decreases, at the Suchdol level increase in
Co, Zn and Ni occurs, the manganese contents oscillates around the mean value.
Downstream the Koštěnický brook mouth increased contents of Pb was observed. It
is possible to state from the long-term point of view that the contents of
heavy metals did not change considerably during the period 1986 to 1998 except
for chrome, the contents of which increases permanently (from 0.24 µg.l-1
in 1989 to 1.30 µg.l-1 in 1995). For the lead
decrease of concentration was registered in the years 1988 and 1989.
The
heavy metals contents in the tributaries varies in the following range (in µg.l-1):
Fe – 411 to 2290, Mn –90 to 330, Zn – 7.6 to 134, Cu –1.43 to 4.08, Cr- 0.18 to
0.82, Cd –0.04 to 0.37, Ni –1.8 to 55.3, Co –0.83 to 52.8, Pb –0.06 to 2.48. It
is significantly influenced by the geological character of the basin.
Tributaries from the crystalinicum have in general lower heavy metals contents,
except for lead. Tributaries from the peat bogs are generally characterised by
extremely high Co a Ni concentrations and also by high contents of Zn, Fe and
Mn.