52
Water In Ecosystems: A Non Renewable Resource
pour La comprehension des systemes ecologiques. Puisque les metaux lourds sont
fixes (par absorption, par coprecipitation, etc .... ) sur differentes phases minerales,
its peuvent egalement etre remobilises sous certaines conditions. Ainsi, une
reduction du potentiel redox a pour consequence une mise en solution des
hydroxydes de fer et de manganese. Ces processus de remobilisation representent
une menace pour les systemes aquatiques, meme si des mecanismes d'absorption
(i.e. sur les argiles) ont apparemment purifie la phase aqueuse.
1
EXPERIMENTAL
In order to obtain a clear insight into the nature of river water/sediment
interactions, most relevant river water parameters (e.g. t, pH, COD, BOD, 02' Corg,
major cation and anion, Cr, Co, Cu, Zn, Cd, Pb content), as well as the contents of
heavy metals in two sediment phases (2M MgCl 2 and 2M HCI-extractable) were
determined at 26 locations (Fig. 1), in the river Tara and in its main tributaries
(Puric, 1993).
2 RESULTS AND DISCUSSION
The data were processed by factor analysis, a multivariate method that enables the
extraction of factors which predominantly determine the system's variability
(Flury, Riedwyl, 1983). The distribution of samples (Fig. 2) clearly indicates the
influence of the Rudnica river (sample 18), draining the Mojkovac mine area, as
wel1 as the purification process downstream - samples 19, 20, 21 - the last sample,
practical1y indistinguishable from the main population, indicates the termination
of the self-purification process, approximatively 10 km downstream from the
Rudnica confluence. The corresponding distribution of parameters (Fig. 3) shows
the nature of the contamination process - most points on the left-hand side of
Fig. 3 represent heavy metal values - dissolved, as well as sedimentary. Factor 2 is
obviously geochemically determined (hardness).
In order to detect more details in the interaction mechanisms, the uncontaminated
area, upstream from the Rudnica mouth, was investigated separately. Factor
analysis of sediment and water sample characteristics clearly shows the clustering
of the following groups of samples (Fig. 4):
Samples of tributaries originating from the flysch region, as wel1 as Tara
River samples in the immediate vicinity of the tributaries' mouths, where
the flysch region influence stil1 dominates (4,5,6,7);
• Tributaries originating from the limestone region, and, again, a similar
Tara River sample downstream (8,9,10);
A main group in the centre, representing Tara River samples - in fact, a
result of thorough mixing and averaging of tributary water
(3,11,13,15,17).
Water In Ecosystems: A Non Renewable Resource
pour La comprehension des systemes ecologiques. Puisque les metaux lourds sont
fixes (par absorption, par coprecipitation, etc .... ) sur differentes phases minerales,
its peuvent egalement etre remobilises sous certaines conditions. Ainsi, une
reduction du potentiel redox a pour consequence une mise en solution des
hydroxydes de fer et de manganese. Ces processus de remobilisation representent
une menace pour les systemes aquatiques, meme si des mecanismes d'absorption
(i.e. sur les argiles) ont apparemment purifie la phase aqueuse.
1
EXPERIMENTAL
In order to obtain a clear insight into the nature of river water/sediment
interactions, most relevant river water parameters (e.g. t, pH, COD, BOD, 02' Corg,
major cation and anion, Cr, Co, Cu, Zn, Cd, Pb content), as well as the contents of
heavy metals in two sediment phases (2M MgCl 2 and 2M HCI-extractable) were
determined at 26 locations (Fig. 1), in the river Tara and in its main tributaries
(Puric, 1993).
2 RESULTS AND DISCUSSION
The data were processed by factor analysis, a multivariate method that enables the
extraction of factors which predominantly determine the system's variability
(Flury, Riedwyl, 1983). The distribution of samples (Fig. 2) clearly indicates the
influence of the Rudnica river (sample 18), draining the Mojkovac mine area, as
wel1 as the purification process downstream - samples 19, 20, 21 - the last sample,
practical1y indistinguishable from the main population, indicates the termination
of the self-purification process, approximatively 10 km downstream from the
Rudnica confluence. The corresponding distribution of parameters (Fig. 3) shows
the nature of the contamination process - most points on the left-hand side of
Fig. 3 represent heavy metal values - dissolved, as well as sedimentary. Factor 2 is
obviously geochemically determined (hardness).
In order to detect more details in the interaction mechanisms, the uncontaminated
area, upstream from the Rudnica mouth, was investigated separately. Factor
analysis of sediment and water sample characteristics clearly shows the clustering
of the following groups of samples (Fig. 4):
Samples of tributaries originating from the flysch region, as wel1 as Tara
River samples in the immediate vicinity of the tributaries' mouths, where
the flysch region influence stil1 dominates (4,5,6,7);
• Tributaries originating from the limestone region, and, again, a similar
Tara River sample downstream (8,9,10);
A main group in the centre, representing Tara River samples - in fact, a
result of thorough mixing and averaging of tributary water
(3,11,13,15,17).