Consequences of the use of thawing salt on our roads
this article we would like to inform and to contribute our standpoint
to an on-going discussion. It concerns the use of thawing salt for the
roads of Kiev and other cities with the goal to facilitate the traffic.
Road thawing salt consists predominantly of common salt (chemical name
sodium chloride or NaCl) sometimes with admixtures of calcium chloride
and (toxic) potassium ferrous cyanide. To road thawing salt there are
hardly alternatives (e.g. snow removal, sand) and therefore it is not
pretended here that it is possible to maintain the traffic completely
without the use of salt. But how much salt must be? For the answer of
this question, also its negative effects must be evaluated apart from
the usefulness of salt. Since the disadvantages are by far less known,
they are briefly described here.
Salt does not only thaw ice and
snow. It attacks the road surface, cars and even reinforced concrete
(buildings). Along the roads (according to literature data up to 80 m!)
salt is deposed on the soil, changes the soil structure and thus
reduces its permeability for rain water. Trees take up the chloride
through the roots, a part will be deposited in the leaves and let them
get brown already in the spring. Rain can wash out the salt from
leaves, but finally this salt comes again in contact with the roots.
After several years the tree is attacked by parasites and dies. Often
salt was the cause but this is not always recognised.
which seeped into the soil, either reaches the groundwater and
sometimes possibly the drinking water or is enriched in the soil. Both
effects are not desired. With the melting water salt comes into the rainwater drains
and a substantial part flows into the brooks. The salt concentration in
the brooks reaches its maximum already short time after the beginning
of the thawing process. One day later the concentration can already
drop to nearly normal values. In order to catch the biologically
relevant maximum, automatic samplers must be set up, which take samples
regularly also at night, or one measures continuously the electrical
conductivity (which depends from the salt concentration).
performed several control measurements on the 14th and 15th of
February2005. On the 14th water collected from the streets and the
storm water drains was strongly loaded with salt as expected. In three
different places of the brook Libid the electrical conductivity was
about 1050 mS/m (roughly 10 times more than usual). The maximal load
was probably even higher. Our laboratory analyses have shown that 1000
mS/m correspond to a chloride concentration of approximately 2500 mg/L.
Such concentrations occur otherwise only in mines drainage water. They
are deadly for stream organisms. Most freshwater organisms tolerate
only 1000 up to 2300 mg/L chloride (literature data, KOPPE and STOTZEK
1999). Most macrophytes (water plants) tolerate not more than 150 mg/L
same risk is given for the ecologically more valuable streams Siretz
and Darnitza because both receive storm water runoff. They also showed
increased conductivity after snow melting.
The river Nivka is an
exception: it seems to receive less storm water and flows through
several ponds. The ponds dilute the inflowing water and reduce the
current velocity. Salt water is heavier than freshwater and sinks down
to the bottom, where it can cause problems as well. Downstream of the
ponds water did not show obvious signs of salinisation or increased
The following day, 15 February, conductivity has fallen already down to between 400 – 500 mS/m in the first mentioned streams.
investigations have already shown that only a reduced number of
organisms live in Kievs’ brooks. Salinisation is possibly one of the
main reasons for that. If we want that our brooks reach a better
ecological status then we should include this aspect into our
considerations and balance advantages and disadvantages of salt use.
our mind, the damage to material and nature is substantial. To quantify
this damage and to put it into relation with the advantages of thawing
salts is unfortunately not possible for us. Nevertheless, following the
precautionary principle, we mean that the use of salt should be
minimised as far as possible. The employment should be limited to the
main connecting roads. On side streets, sand must be strewn in the case
of need. The most important is however that the drivers and the
inhabitants understand the needs and accept measures if taken by the
Environmental Association has published the following article about
chestnut trees that are suffering from salt, air pollution and soil
V.) KYIV CHESTNUT TREES NEED TREATMENT:
National Radio Company of Ukraine, February 12, 2007
boasts two million chestnuts, scientists of the National Academy Of
Sciences inform. The majority of them, however, experience some bad
condition, especially those, located in the Kyiv downtown.
of the Hryshko National Botanical Gardens are engaged in carrying out a
research of the state of Kyiv chestnuts. The scientists agree Kyiv
chestnuts need treatment, at least this proves to be cheaper than
planting new chestnuts, evaluated at 100 M. US$.