Figure 4. Chemical monitoring
The chemical monitoring (Figure 4) was carried out to determine:
heavy- and toxic element content of the different experimental samples;
natural water chemical composition [17]; mountain lake
hydrochemical characteristics [8]; geochemical composition
of Rila water [19]; biogenic emissions and organic
components in air [19,
20]; activity
and chemical composition of lysimetric water in forest soils of the Rila
mountain [21]; anion composition of rain and snow precipitation
[22].
The
heavy and toxic elements in environmental samples were estimated mainly
by means of X-ray fluorescent analysis [16]. Atomic
absorption analysis was used in some investigations to increase the accuracy
of the low concentration measurements [23].
During all expeditions (from 1994 till 1996) [18,24,25]
more than a hundred samples, most of them from permanent water sources
in the Rila mountain (lakes, rivers, springs) were studied. There is no
indication for heavy metal pollution in the mountain lakes under consideration.
The Iskar river is the longest Bulgarian river and
its upper reach is situated in the north slopes of the Rila Mountain. The
Iskar dam - the biggest water reservoir in the country used mainly for
water supply of the capital - Sofia city, is constructed at the foot of
the mountain. The sediment regime of the Iskar river [26]
and its tributaries plays a significant role connected with the river impact
on environment. This is due to capacity of sediments to adsorb and transport
the toxic elements in the basin.
There is no reason to assume that the sediments in the mountain section
of the Iskar river and its tributaries are polluted by heavy metals and
toxic elements. The content of the investigated elements could not affect
the water quality of the Iskar dam [28], used as the
main drinking water supply of the Sofia city.