heavy metal accumulation of danube river aquatic plants indication of chemical contamination

Cent. Eur. J. Biol. • 3(3) • 2008 • 285–294
DOI: 10.2478/s11535-008-0017-6

Central European Journal of Biology

Heavy metal accumulation of Danube river aquatic
plants – indication of chemical contamination
Research Article

Slobodanka Pajević*, Milan Borišev, Srđan Rončević, Dragana Vukov, Ružica Igić
Department of Biology and Ecology,
Faculty of Natural Sciences,
21 000 Novi Sad, Serbia

Received 2 November 2007; Accepted 14 February 2008

Abstract: In this paper, the ecological status of a section of the Danube River flowing through Serbia from Bezdan to Djerdap was evalutated.
Using the chemical composition of water, sediment samples from the littoral zone and dominant aquatic macrophytes, the level of
chemical pollution was ascertained. Chemical analyses of the water and sediment indicated that the tributaries flowing into the Danube
significantly influenced the chemical load of the water and as a direct consequence, the sediment. The concentration of heavy metals
including Cu, Mn and Cd found in plants of the Potamogeton genus, further indicated significant chemical pollution, establishing a
clear link between the chemical composition of plant tissues and the chemical composition of water and sediment. This paper therefore
describes how the chemical composition of aquatic plants can be used as a reliable indicator for heavy metal pollution of aquatic
ecosystems.
Keywords: M
 acrophytes • The Danube River • Potamogeton sp. • Bioindication • Heavy metals
© Versita Warsaw and Springer-Verlag Berlin Heidelberg.

1. Introduction
Macrophytes are important in the biological monitoring
of aquatic ecosystems, as changes in the composition

of the aquatic vegetation are considered a reliable
biological indicator of the quality of water [1-3].
Seasonal dynamics of macrophyte associations, as
well as the distribution according to structure (species
number, population density), represent important
indicators of general ecological circumstances which
are dominant in aquatic ecosystems [4,5]. Pollution of
aquatic ecosystems may also be estimated based on
the accumulation rate of nutrients and heavy metals.
Many studies had researched the use of macrophytes
as indicators of metals bioaccumulation [6-8].
However, while macrophytes are useful biomonitors,
the bioconcentration of metals in macrophytes may
be the result of the exposure to metals in both water
and/or sediments, making it difficult to directly compare
between the concentrations measured in plants and in
the environment (i.e., water or sediments).
Chemical, biochemical, and biophysical mechanisms
of uptake and accumulation of heavy metals into various
* E-mail:

aquatics plants and also, the effect of accumulated
metals persistent in plant metabolism have been widely
studied [9-11]. Most macrophytes which are primarily
submersed and floating, have the ability to tolerate
moderately high levels of heavy metal contamination
by forming chelates (by binding metal ions to organic
molecules) and by subcellular compartmentation. In such
aquatic plants, phytochelatines and metalothionines
are the main cytoplasmic chelators of heavy metals

[12]. In addition, the increased activity of metabolic
pathways giving rise to glutathione and organic acids
which act as intracellular ligands of metals and organic
acids, is important for growth in water and/or sediment
contaminated with heavy metals [13].
While macrophytes accumulate and filter out
chemical elements from the surrounding environment,
the physical presence of macrophytes in water systems
increases the stability of sediment, and, reduces
eutrophication. In addition, macrophytes are involved in
bioremediation due to their high tolerance to metals and
the affect on ion solubility through the release of O2 from
their roots [14]. Consequently, macrophytic vegetation
may be used in purification of natural aquatic resources,

285


Heavy metal accumulation of Danube river aquatic
plants – indication of chemical contamination

substratum and littoral zone. Permanent monitoring of
chemical composition of water and monitoring of the
distribution and abundance of aquatic plant species are
useful tools in outlining programs for the sustainable
development of aquatic ecosystems.
The Danube, like other river systems, is affected
by human activities resulting in contamination of the
water and its littoral zone. Pollution stemming from
power plants, oil refineries and fertilizer plants can

cause contamination of surrounding air and waterways.
Consequently, in order to cultivate effected areas
of once arable land, one must address not only the
contamination of the Danube but also contamination
coming from other tributaries.
While commercial use of phytoremediation is a
plauisble way to purify contaminated areas, the role of
macrophytes in the complex pathways of nutrient and
heavy metal cycling, in aquatic ecosystems must first
be understood.
Our objective was to determine the ecological
status of littoral zone of the Danube River in Serbia,
by assessing the heavy metal content of dominant
macrophytes. The flow section of the Danube River
utilised in this study starts at 1433 river kilometers
(rkm) on the state border with Hungary and Croatia
and ends at 845 rkm on the state border with Romania
and Bulgaria. The results obtained, form the basis of an
ecological monitoring system for this aquatic area and
highlight the importance of macrophytic vegetation in
remediation - removing chemical pollutants from water
and sediments in particular.

2. Experimental Procedures
Concentration of heavy metals (Fe, Mn, Cu and Cd) in
water and sediment was determined by flame atomic
absorption spectrophotometry [15].
To determine which macrophytes were dominant
at the littoral zone samples were collected by using a
random block system in the period of a maximal organic

production (July 2006). The same plant species from
different sites were collected to facilitate the comparison
of results (Table 1).
Djerdap I hydroelectric power plant is located at
942nd river kilometer, while Djerdap II hydroelectric
power plant is located at 863rd river kilometer (Figure 1).
Differences in water levels on these damns can reach
up to 30 meters. Prahovo (35) and Radujevac (36)
represent the last two urban sites at the Danube in
Serbia,with Prahovo also housing a number of chemical
plants. The Mlava mouth (14), Dubovac (15,16), and
Ram (17) belong to the Labuduvu Okno Protected
286

Figure 1.

The Danube flow portion through Serbia.

area, representing a part of the Deliblato Sands. This
protected area has no pollution sources to deplete its
aquatic ecosystems. The Smederevo metal smelter (11)
and the Kostolac thermal power plant (13) are a serious
industrial threat declining water quality of the Danube.
On each sampling location, three patches of each
plant species were collected and pooled into one
uniformed sample. Only vegetative parts of plants were
selected (leaves with stems). Plant material was rinsed
in deionised water, dried and prepared for analyses
following standard methods for the examination of water
and wastewater [16]. The concentrations of heavy metals

were determined after drying at 450ºC and treatment
with 25% HCl. Concentrations of Fe, Mn, Cu and Cd
were determined from prepared solutions by employing
the atomic absorption spectrophotometry (AAS).
Statistical analyses was conducted on plant samples
using Duncan’s Multiple Range Test, at the level of
significance P<0.05, using 1-way factor analyses.
At each location sediment was collected using a van
Veen grab (36 x 28 cm) in three replicates in the vicinity
of plants. Water was also sampled in the zone of plant
growth, at a depth of 0.5 m, using 0.5 l samplers, in
three replicates.
A t-test (one-population) was performed to test
the differences between concentrations of metals
in water and sediment. All statistical analyses were
conducted with computer software Origin 5.0 in order to
determine whether the location had an effect on metal
concentration. Each metal was analyzed individually. A
level of 0.05 alpha was used to determine significance.
All data shown in tables are mean values.


S. Pajević et al.

No.

Location

River km

Sampled species

1.

Bezdan

1 425

Juncus compressus Jacq.

2.

Bogojevo

1 366

Rorippa amphibia L.

3.

Bačka Palanka

1 298

Rorippa amphibia L.

4.

Beočin

1 269

Rorippa amphibia L.

5.

Sremski Karlovci

1 244

Rorippa amphibia L.

6.

Stari Slankamen

1 215

P. pectinatus L., P. perfoliatus L.

7.

Mouth of the Tisza River

1 214

Ceratophyllum demersum L.

8.

Zemun

1 173

Juncus compressus Jacq.

9.

Mouth of the Sava River

1 170

Rorippa amphibia L.

10.

Vinča

1 144

P. pectinatus L., P. perfoliatus L., P. lucens L.

11.

Smederevo

1 116

P. pectinatus L., P. lucens L.

12.

Mouth of the Morava River

1 104

P. pectinatus L.

13.

Kostolac

1 095

P. pectinatus L., P. perfoliatus L.

14.

Mouth of the Mlava River

1 091

P. pectinatus L., P. gramineus L.

15.

Dubovac right bank

1 085

P. pectinatus L., P. perfoliatus L.

16.

Dubovac left bank

1 085

P. pectinatus L., P. perfoliatus L., P. lucens L.

17.

Ram

1 076

P. perfoliatus L., P. lucens L.

18.

Mouth of the DTD canal

1 076

P. lucens L.

19.

Veliko Gradište

1 059

P. pectinatus L., P. x fluitans Roth., P. lucens L.

20.

Golubac

1 044

Ceratophyllum demersum L., P. perfoliatus L.

21.

Golubačka Tvrđava
– Djerdap National Park

1 040

Elodea canadensis Michx., P. pectinatus L., P. perfoliatus L., P. lucens L.

22.

Mouth of the Brnjička river
– Djerdap National Park

1 032

P. perfoliatus L., P. lucens L.,
Myriophyllum spicatum L.

23.

Dobra
– Djerdap National Park

1 020

P. perfoliatus L., Myriophyllum spicatum L.

24.

Djerdap National Park

1 010

P. pectinatus L., P. perfoliatus L.

25.

Greben – entry into lake “Djerdap” of the Djerdap
National Park

999

P. perfoliatus L., P. lucens L.

26.

Donji Milanovac

– Djerdap National Park

990

P. lucens L.

27.

Mouth of the Porecka river
– Djerdap National Park

988

P. x fluitans Roth., P. pectinatus L.

28.

Malo Golubinje
– Djerdap National Park

980

P. perfoliatus L., P. lucens L.

29.

Veliki Kazan
– Djerdap National Park

970

P. x fluitans Roth.

30.

Djerdap National Park

960

P. lucens L.

31.

Tekija
– Djerdap National Park

955

Nymphoides peltata (S.G.Gmelin) O. Kuntze.,
P. perfoliatus L., P. lucens L.

32.

Kladovo

933

P. perfoliatus L., P. lucens L.

33.

Brza Palanka

883

P. perfoliatus L., Ceratophyllum demersum L.

34.

Kusjak

863

P. pectinatus L.

35.

Prahovo

861

Scirpus palustris L.

36.

Radujevac

852

Scirpus palustris L.

Table 1.

Location of test sites and plant species sampled along the Danube River in Serbia.

287


Heavy metal accumulation of Danube river aquatic
plants – indication of chemical contamination

Sampling
site

Fe
water
mg ∙ l-1

Mn
sediment
mg ∙ g-1

water
μg ∙ l-1

water
μg ∙ l-1

Cd
sediment

μg ∙ g-1

water
μg ∙ l-1

sediment
μg ∙ g-1

1

930.3

17.4

38.0

271.3

8.1

18.0

0.3

1.4

2

589.7

24.4

33.7

129.7

21.7

38.0

1.9

1.5

3

730.3

12.6

51.7

154.3

2.7

8.8

1.1

1.2

4

390.7

30.6

22.7

373.7

4.1

26.1

1.1

1.7

5

239.0

23.4

24.3

203.7

9.6

21.0

1.1

1.4

6

981.3

-

34.3

-

8.1

-

1.1

-

7

241.7

34.8

28.7

678.3

6.8

72.4

0.8

3.2

8

240.1

23.8

26.7

294.7

4.2

36.1

0.3

1.5

9

1608.7

44.5

44.7

358.7

16.3

45.0

1.7

3.6

10

1510.3

36.1

74.3

554.3

42.7

43.7

1.7

2.8

11

242.0

7.9

25.3

154.3

8.2

5.4

0.8

0.7

12

289.3

38.7

28.7

664.3

34.7

43.0

1.7

2.4

13

489.7

-

58.3

-

31.7

-

0.7

-

14

241.0

32.5

18.3

608.0

14.3

51.0

0.3

2.5

15,16

289.0

38.4

23.3

593.3

6.7

77.7

1.5

3.2

17

1022.0

39.2

78.7

467.3

4.1

56.3

0.6

2.8

18

389.0

19.3

33.3

201.3

9.6

13.7

0.3

1.1

19

341.0

-

30.3

-

0.0

-

0.3

-

20

340.3

14.2

25.3

310.3

11.7

30.3

0.6

2.2

21

182.3

5.9

18.3

224.0

9.5

14.1

1.1

2.5

22

34.0

23.1

9.5

193.3

1.6

20.7

0.8

2.1

23

539.3

41.8

47.3

373.3

6.8

72.8

0.3

1.9

24

389.0

18.1

43.3

650.7

4.2

70.1

0.6

2.5

25

290.7

20.7

26.3

397.3

2.7

43.1

0.6

2.4

26

440.5

38.4

51.3

483.3

31.1

70.9

1.7

2.9

27

240.1

31.6

25.3

389.7

2.8

24.0

0.8

1.0

28

390.3

45.7

35.3

389.7

5.5

37.1

1.1

1.1

29

209.9

36.6

14.3

580.3

446

74.0

0.6

2.6

30

290.7

-

27.3

-

5.5

-

0.6

-

31

56.6

51.6

16.2

726.0

0.0

92.0

0.6

3.2

32

181.3

18.0

23.7

232.3

4.3

16.0

1.1

1.1

33

239.7

-

25.3

-

5.4

-

1.4

-

34

290.3

45.1

49.2

500.3

5.4

81.9

0.8

2.5

35

24.0

11.2

16.3

156.3

8.2

33.0

0.6

0.7

391.3

12.0

38.3

171.3

8.1

106.1

0.6

1.2

36

Table 2.

Heavy metal concentrations in water and sediment (mud) at investigated localities.

3. Results and Discussion
3.1. Heavy metals in the Danube water and
sediment in its section through Serbia

Heavy metals are naturally found in the environment at
low concentrations due to the composition of the Earth’s
crust. However, due to lax regulations of industrial
‘outputs’ and inadequate environmental monitoring,
water systems are now contaminated with heavy metal

288

Cu
sediment
μg ∙ g-1

pollution. Main sources of these pollutants are industrial
and urban waste which includes the runoff from

agricultural chemicals. The ecological consequence of
such contamination is that sediment absorbs the heavy
metals and then these metals may enter the food chain.
Due to a lack of legislation in Serbia concerning
sediment quality, the quality of the sediment was
compared to Holland’s recommendations for standard
sediment quality (Anon 2000), in addition to a general
directive from the EU [17]. The water quality was


S. Pajević et al.

Metal content water

P-value

Significant difference
at level 0.05

Metal content
sediment

P-value

Cd

3.11 ·10-13

Yes

Cd

4.36 ·10-18

Yes

Cu

0.04642

Yes

Cu

4.15 ·10

-12

Yes

Fe

3.11 ·10-8

Yes

Fe

2.40 ·10-16

Yes

Mn

7.20 ·10-20

Yes

Mn

4.49 ·10-15

Yes

Table 3.

Significant difference
at level 0.05

Statistical analysis of the dependence of metals content on the location.

compared to Serbian maximum legal concentrations
of pollutants as defined in the Book of Rules regarding
dangerous substances [18].
Results showed that waters flowing from the mouth
of the Tisza, Sava and Morava rivers, into the Danube
significantly increased the chemical load of water and
sediment (Tables 2 and 3).
The concentration of Cd, Cu, Fe and Mn varied
greatly among sample sites (Table 3).

An increased concentration of Fe and Cd were
observed at the convergence of the Sava River and the
Danube (Table  2). Similarly at the mouth of the Tisza
river, high concentrations of all researched metals
was found in the sediment, whilst the increased metal
concentration was also noticed at Location 10 which is
situated after the Tamiš mouth. Furthermore, a significant
increase of the Mn, Cu and Cd concentrations was
observed in the Danube sediment following the mouth of
the Morava River (Location 12). These results suggest
the tributaries flowing into the Danube greatly affect the
heavy metal contamination of the Danube. High metal
values in the sediment were also noted at Location
15 and 16 (Dubovac) which belong to the Deliblato
sands Protected Area in the flooded zone. At Location
26 (Donji Milanovac), the Danube is up to 2 km wide,
the water speed is slower than regions upstream and
sediment settles down. As a consequences, increased
concentrations of Mn, Cu and Cd, in the sediment and
water was identified (Table  2). At Location 29, there
is a great narrow spot of the Danube (Veliki Kazan),
and extremely high concentration of Cu was recorded
both in the sediment and in the water samples. Before
the Djerdap I hydroelectric power plant at Location 31
(Tekije) as well as before the Djerdap II hydroelectric
power plant (Location 34, Kusjak) the water is slow,
the sediment settles down, which results in high heavy
metal contamination. The localities which are situated
downstream from the Smederevo smelter and the
Kostolac power plant also appear to be chemically

loaded.

3.2. Heavy metals in macrophytes – indicators
of the Danube River in its section through
Serbia

In formulating new “ecosystematic” decrees and
regulations regarding water quality, countries belonging to
the European Union follow chemical and microbiological
parameters in addition to novel biological parameters
which include the monitoring of living creatures [19].
Increased concentrations of heavy metals in aquatic
environments does not lead to visible plant damage as
plants have developed specific physiological mechanisms
to survive in these polluted conditions [13,20]. The ability
to effectively remove metal ions out of solution and to
accumulate high levels of these pollutants in plant tissue
are dependent on plant species and metal ions. Some
factors involved in the determining such differences
include the rate of chelation, ionic exchange, chemical
precipitation, translocation of metal ions and precipitation
induced by root exudates or by microorganisms [21]. As
a result, hyperacumulation of heavy metals can be used
alongside other bioindicaters and phytoremediaters as
important factor to consider when defining the ecological
status of aquatic ecosystems, or using macrophytes for
purification of polluted river [22-24].
Our results show that purification efficacy, uptake and
accumulation rates of studied heavy metals, depended
both on plant species and sampling site. Variations of

concentration ratio between investigated heavy metals
in plant tissue of the same plant species were site
dependent.

3.3.

Heavy metal concentrations
Potamogeton perfoliatus

in

Potamogeton perfoliatus species was dominant at 16
out of the 36 sites sampled, and was therefore used as
a test species for chemical analyses. The content of Fe
in the tissue of P. perfoliatus varied from 1280 μg ∙ g-1
(0.128%), at Location 20 (Golubac), to 5800 μg ∙ g-1
(0.58%) at Location 28 (Malo Golubinje) (Table 4).
The observed concentrations of Fe (found at levels
of >1%) were significantly lower than results from a
previous study undertaken on the same species at similar
locations along the Danube River [25]. The distibution of
Fe in P. perfoliatus varied along the Danube River, with
289


Heavy metal accumulation of Danube river aquatic
plants – indication of chemical contamination

Sampling site

Fe

Mn

Cu
μg ∙ g

Cd

Sampling site

Mn

Cu
μg ∙ g

Cd

-1

6

2550 efg

431 fg

9.67 f

1.43 ef

6

5472 c

1060 ef

12.67 d

1.33 cde

10

4067 c

1494 b

14.11 cd

1.37 ef

10

1223 g

1371 d

9.39 fg

1.90

13

4361 c

1557 b

10.89 ef

1.38 ef

11

6945 b

1039 ef

14.89 c

0.93 fg

a

15

2294 fgh

1404 b

13.00 de

1.78 cde

12

2844 f

948 f

11.33 e

0.80

16

2267 fgh

2695 a

13.44 de

1.94 cd

13

2972 ef

2571 d

8.72 g

1.27 def

g

17

2645 efg

1064 c

13.50 de

2.00 cd

14

3272 ef

1077 ef

12.89 d

1.20

20

1281 j

853 d

8.89 f

1.67 de

15

1230 g

1491 c

9.89 f

1.43 bcde

ef

21

1602 ij

567 ef

15.11 bcd

3.44

a

16

1139 g

3929 a

9.22 fg

1.67 abc

22

3022 de

1180 c

16.44 abc

1.53 def

19

3644 e

754 g

13.17 d

1.77 ab

23

5000 b

1155 c

18.94 a

2.72 b

21

4793 d

1136 e

11.33 e

1.93

24

2850 def

294 g

19.00 a

2.22 c

24

9895 a

679 g

23.33 a

1.60 abcd

a

25

3356 d

576 ef

13.33 de

1.67 de

27

5794 c

409 h

16.06 b

0.93 fg

28

5800 a

460 fg

19.11 a

1.78 cde

34

3478 ef

1561 c

8.11 h

1.67 abc

31

1856 hij

290 g

17.33 ab

2.22 c

32

3317 d

604 ef

18.39 a

1.68 de

33

2038 ghi

654 e

8.5 f

1.60 de

Table 4.

Average Fe, Mn, Cu and Cd concentrations in Potamogeton
perfoliatus plants.

Data with the same letter represent statistically identical values in
vertical columns (P<0.05)

higher levels of accumulation observed in the section
around Vinča (Location 10), Kostolac (Location 13),

Dobra (Location 23) and Malo Golubinje (Location 28).
Although there was no significant corelation between
Fe concentrations in the water and sediment compared
with Fe concentrations in the plant tissue, it can be
noted that with the increase of Fe in the surroundings,
the levels accumulating in plant tissue was greater
(Tables 3 and 5).
The highest Mn concentration in the tissue of P.
perfoliatus was recorded at Location 16 (Dubovac – left
shore). This increase of Mn concentration, is most likely
due to an inflow of industrial waste water from the nearby
smelter, as well as contaminated waters flowing from the
Sava, the Morava and the Mlava Rivers. Comparisions
between the Mn concentration in P. pectinatus and the
Mn concentration in water and sediment were statistically
significant, indicating the relevance of P. perfoliatus as a
bioindicator for heavy metal contamination.
The results shown in Table 4 demonstrate that
the highest concentration of Cu was recorded was
at Location 28 (Malo Golubinje, 19.11µg·g-1). At this
sample site, large amounts of waste water loaded with
heavy metals is discarded from the thermal power plant.
P. perfoliatus species also had higher amounts of Cu
in region 23 – Dobra (18,97µg·g-1) and region 24 – the
Djerdap National Park (19,0 µg/g), when compared to
the other locations. The presence of Cd was discovered
in the tissue of P. perfoliatus at all sample sites.
290

Fe

-1

Table 5.

Average Fe, Mn, Cu and Cd concentrations in Potamogeton
pectinatus plants.

Data with the same letter represent statistically identical values in
vertical columns (P<0.05)

Concentrations were as low as1.37 μg ∙ g-1 (in the Vinča
region, loc. 10 and 13) and peaked at 3.44 μg ∙ g-1, in
the Golubac Fortress region (Location 21). Although the
recorded values were not extremely high, the presence
of Cd in the plant tissue is a strong indicator of the
chemical load of the water as well as the sediment of
the Danube River.

3.4.

Heavy metal concentrations
Potamogeton pectinatus

in

The aquatic species, P. pectinatus, was dominant at 13
sample sites. The highest Fe concentration of nearly
1% (9895 μg ∙ g-1) was recorded in the Djerdap National
Park region (Table 5).

The Mn content in the tissue of P. pectinatus was
on average higher when compared to P. perfoliatus and
P. lucens. However, a significant correlation beetwen
the concentrations of Mn in water and plant tissue for
P. perfoliatus (rxy = 0.765), for P. pectinatus (rxy = 0.672)
and for P. lucens (rxy = 0.665) was obtained. Also it can
be noted that the coefficient of linear correlation between
water Mn concentration and sediment Mn concentration
in these localities was positive although not statistically
significant (rxy = 0.195). The highest registered values
of Mn was 3929 μg ∙ g-1 at Location 16 (Dubovac – left
shore). These data support already noted data for P.
perfoliatus indicating that the level of Mn contamination
of the water and littoral zone in the Kostolac thermal
power plant region is high (Table 4). Chemically loaded
waste waters of the Kostolac thermal power plant could
theorectically introduce significant amounts of Mn to the
river system.


S. Pajević et al.

Sampling site

Fe

Mn

Cu
μg ∙ g

Cd

Sampling site

Fe

Mn

Cu
μg ∙ g

-1

Cd

-1

10

2300 gh

1134 e

12.56 fg

0.98 e

7

10822 a

4997 a

58.28 a

9.17 a

11

2522 fg

1325 d

12.78 fg

1.26 de

20

3702 b

2165 b

12.78 b

1.45 b

16

3206 de

2786 a

13.44 fg

1.67 cd

33

4083 b

4036 a

17.56 b

2.78 b

17

3761 cd

1797 c

13.33 fg

1.49 cd

18

7405 a

1110 e

14.06 ef

1.37 cde

19

1828 hi

1842 bc

13.06 fg

0.33

21

793 j

695 g

11.33 g

2.61 a

22

2917 efg

1896 b

17.33 d

1.43 cd

25

3811 cd

642 g

19.78 c

1.33 cde

2911 efg

348 i

16.06 de

1.63 cd

28

4078 c

517 h

26.44 a

1.70 cd

30

1423 i

406 i

23.33 b

1.73 bc

31

2961 ef

381 i

22.61 b

1.63 cd

32

5889 b

840 f

20.00 c

2.11

b

Average Fe, Mn, Cu and Cd concentrations in Potamogeton
lucens plants.

Data with the same letter represent statistically identical values in
vertical columns (P<0.05)

It can also be concluded that the distribution of
Cu and Mn in plants per localities was similar for all
three species. The Cu concentration in P. perfoliatus
ranged from 8.11 μg  ∙  g-1, at Location 34 (Kusjak), to
23.33 μg ∙ g-1, at Location 24 (the Djerdap National Park).
The presence of Cd was also detected in P.
pectinatus samples from all researched locations, which
clearly implies chemical pollution of the water, the littoral
zone and the bottom. The highest concentration of
this heavy metal of 1.93 μg ∙ g-1 was registered at the
Golubac fortress (Location 21).

3.5.

Heavy metal concentrations
Potamogeton lucens

Average Fe, Mn, Cu and Cd concentrations in Ceratophyllum demersum plants.

Data with the same letter represent statistically identical values in
vertical columns (P<0.05)

f

26

Table 6.

Table 7.

in

Surprisingly, our results showed that the content of Fe in
the dry matter of P. lucens varied significantly between
sample sites, ranging from 793 μg ∙ g-1 to 7405 μg ∙ g-1 dry
matter. The highest concentration of this microelement
was observed in the plant tissue from Location 18 at the
mouth of the DTD channel (Table 6).
All three examined species of the Potamogeton
genus, had extremely high accumulation of Fe in the
section of the lower flow of the Danube around the
Djerdap National Park, the mouth of the DTD channel
and Smederevo. The highest concentration of Fe
was recorded in the P. pectinatus tissue. This kind of
distibution of Fe in the tissue of the examined species,
positive corelated with the load of the water and the

sediment containing this heavy metal.
According to our results, the distribution of the Cu
and Mn contents in the P. perfoliatus and P. lucens plant

tissues were very similar. High accumulation of Cu in
both species was at Location 28 (Malo Golubinje), and
Mn at Location 16 (Dubovac – left shore).
The presence of Cd was detected in P. lucens
plant tissue at all researched localities. Following the
distibution of Cd in P. lucens, a distinctive load of the
water and the sediment around the Golubac Fortress
section (Location 21- 2.61 μg∙g-1) and Kladovo (Location
32 - 2.11 μg ∙ g-1) was observed.
Based on the content of the examined heavy metals in
Potamogeton spp., the chemical composition of aquatic
plants is a reliable indicator of the heavy metal pollution
of the aquatic ecosystems supporting researched
conducted by Mikryakova [26]. The metal content in
plants, water and sediment clearly indicated which areas
of the Danube are ecologically endangered.


3.6.

Heavy metal concentrations
Ceratophyllum demersum

in

Ceratophyllum demersum is a well known

hyperaccumulator and consequently plays a large role in
the monitoring aquatic ecosystems [7]. In our research,
C. demersum was only found at three localities, where
the Danube flows slowly (Table 7).
Heavy metal concentrations greater than 1% were
recorded at Location 7 (the mouth of the Tisza River) which
indicates that the Tisza River is under obvious chemical
pressure from industrial waters, as well as runoff from
surrounding agricultural areas. The highest concentrations
of other researched heavy metals were also registered
at this site. Furthermore, the Cd uptake of C. demersum
plants at the mouth of the Tisza River was extremely high,
9.17 μg ∙ g-1.

3.7. Heavy metal concentrations in Rorippa
amphibia

The heavy metal content in helophytes is also used in
biomonitoring as an indicator of chemical contamination
of aquatic ecosystems. These plants function as a filter
for toxic substances and aid the natural purification of
waste waters from agricultural, urban and industrial
areas [27,28]. The high accumulation of nutrients and
heavy metals in aerial parts is not characteristic in these

291


Heavy metal accumulation of Danube river aquatic
plants – indication of chemical contamination

Sampling site

Fe

Mn

Cu

Cd

μg ∙ g-1
2

10170 a

203 b

18.61 a

1.10 b

3

3783 c

95 d

9.06 c

1.02 b

4

7594 b

170 c

6.61 c

0.56 c

5

8978 a

327 a

13.83 b

1.06 b

9

7305 b

249 b

17.11 ab

1.46 a

Table 8.

Average Fe, Mn, Cu and Cd concentrations in Rorippa amphibia plants.

Data with the same letter represent statistically identical values in
vertical columns (P<0.05)

species, however, very high concentration of metals can
often be noted in roots and rhizoma.
Rorippa amphibia was used as a test species in this
research. The chemical analysis of the upper part of the
plant was done.
The highest accumulation of Fe in R. amphibia tissue
was registered at the Bogojevo site (10170  μg  ∙  g-1)
(Table  8). Also, relatively high concentrations of Fe
was noted in Sremski Karlovci (8979 μg ∙ g-1), while the
lowest levels were recorded at the Bačka Palanka site
(3783 μg ∙ g-1). Based on these results, it can be noted
that there is a distinctive chemical load in the water and
sediment in the Bogojevo and Sremski Karlovci sections.
The concentration of Cd in Rorippa amphibia
plant tissue was recorded at all localities where this
species was identified and concentrations ranged from
0.56 μg ∙ g-1 to 1.46 μg ∙ g-1. Although samples were not
collected from more locations, it still can be concluded
that the chemical composition of R. amphibia can also
serve as an indicator of chemical load of the littoral zone.

4. Conclusions
In aquatic ecosystems, water and sediment quality
may vary depending anthropogenic origin as well as
natural parameters including various biogeochemical
processes. Results obtained from our study showed that
the rivers which flow into the Danube from its entering
point in Serbia (the Tisza, the Sava, the Morava, and
the Tamiš) significantly influence the chemical load of
water and sediment. Where the Sava River converges
with the Danube, increased concentrations of Fe and Cd
were recorded. At the mouth of the Tisza River, higher
concentrations of all researched metals were registered
in the sediment, while the increased metal concentration
was also noticed at the site situated after the Tamiš
mouth. The sample sites situated downstream from the
smelter and the power plant were also chemically loaded.
Macrophytes are biological filters that purify
water bodies and littoral zones by accumulating
292

dissolved metals and toxins. These aquatic plants
are useful indicators when monitoring of ecological
status of ecosystems. Consequently, this study aimed
at understanding the importance of macrophytes
in bioindication and bioremediation of toxic metals
and controlling the heavy metal pollution – thereby
suggesting the remedial measures for the preservation
and restoration of Danube river ecosystem. Our results
show that purification efficacy, uptake and accumulation
rates of studied heavy metals, depended both on plant

species and sampling site.
All three examined species of the Potamogeton
genus, had extremely high accumulation of Fe in the
section of the lower flow of the Danube around the
Djerdap National Park, the mouth of the DTD channel
and the metal smelter. The highest concentration of Fe
was noted in the P. pectinatus. The distribution of Fe in
tissues of the examined species positively reflected the
degree contamination in the water and sediment.
The increase in Mn concentrations in the plants
may be the result of the industrial waste waters inflow
from the smelter, as well as the inflows from other
rivers. A statistically significant correlation between
Mn concentration in P. pectinatus tissue and Mn
concentration in water and sediment was observed
which confirms the role of this plant as an indicator
of the environmental chemical load. It can also be
concluded that the distribution of Cu and Mn in plants
at specific locations was similar for all three species
of Potamogeton. The correlation coefficient of Mn
site distribution between P. perfoliatus and P. lucens
was highly significant (rxy  =  0.906). Also, significant
correlations of Mn distributions were recorded between
P. pectinatus and P. lucens (rxy  =  0.783) and between
P. pectinatus and P. perfoliatus (rxy = 0.921). Significant
correlations of Cu distributions were recorded between
P. perfoliatus and P. lucens (rxy = 0.737) and between P.
pectinatus and P. perfoliatus (rxy = 0.715).
Based on the heavy metals concentrations in
Potamogeton spp., it can be concluded that the chemical

composition of macrophytes is a reliable indicator of
the heavy metal pollution of the aquatic ecosystems.
Furthermore, these macrophytes may potentially be
useful in purifying natural aquatic resources as part
of program for sustainable development of aquatic
ecosystems.

Acknowledgements
This study was supported by Ministry of Science and
Environment Protection of the Republic of Serbia as part
of project number 143037.


S. Pajević et al.

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