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USE OF SELENASTRUM CAPRICORNUTUM
GROWTH INHIBITION TEST FOR TESTING
TOXICITY OF METAL IONS IN SOIL AND WATER
I. Ivanova, V. Groudeva
Sofia University "St.Kl.Ohridski", Faculty of Biology, Dept. of Microbiology, Sofia, Bulgaria

ABSTRACT
The unicellular green alga Selenastrum capricornutum (Rhapidocelis subcapitata) growth
inhibition assay was applied to the toxicity testing of water,suspensions of heavy-metalpolluted clinker and waste ore pile. The ISO 8692:2004 standard test procedure was followed, and growth rate inhibition indexes were determined. Despite high concentrations
of zinc in water (38.47 mg/L of Zn), exceeding by approximately 400-fold the EC50 value
for S. capricornutum (0.1 mg Zn/L), 72-h algal growth in the soil extracts was inhibited
with 50% in comparisonwith growth in the standard control ISO mineral medium. Cell
dead of algae was observed by clinker leacheates contained up to 796 mg Cu/L. Decreasing of inhibition effect and rate of cell dead could not be explained by supplementary nitrogen, phosphorous, and carbonate leached from the waste ore pile and clinker.

Introduction
Growth inhibition toxicity tests were usually used for determiningthe presence of
toxic substances in environment (9). Microbial growth rate decreases with increasing toxicity (4). Bacterial growth inhibition tests could not be used in experiments with pure water, because they compete, when the nutrient medium is depleted.
In such situation green algae could be used
successfully for determination of the toxic
and mutagenic effect of chemicals, heavy
metals,pesticides or industrial wastes (10,
1).
Algae are important system, because they
could accumulate and metabolize nonmutagenic substances (promutagens) till
mutagenic products, different from these in
high plants and animals (11).
The aim of this work was to compare the
sensitivity of internationally accepted algal
test for the toxicity assessment of soil and
water. We determined theenvironmental
toxicity of metal ions in drainage waters
and leached solution of clinker, waste ore
179

pile using the growth inhibition of Selenastrum capricornutum – ISO 8692:2004 .

Materials and Methods
Investigated materials
- Drainage waters, collected from the East
side of Plant for Color Metals Processing
(PCM) – Plovdiv;
- Drainage waters, collected from the West
side of waste orepile next to Agria plant
-Plovdiv ;
- Clinker, collected from waste ore pile
with temperature 80-90 ºС (hot pile);
Processing of the samples
Immediately after collection the samples
were put on ice and transported to the lab,
where they were kept frozen till the processing. They were defrosted on ice for
several hours without disturbing of their
composition.
Water samples werecentrifuged at 2500
rpm for а 15 min, after that they were filtered through filter paper. Clinker and
waste ore pile samples were mixed with
bidistilled water in the proportion 1/10 for
Biotechnol. & Biotechnol. Eq. 20/2006/1

TABLE 1
Chemical analysis of PCМ-Plovdiv (ICP AES)
Sample N
As
Cd
Cu
Fe
Hg
Mn
Ni
Pb
Zn

Sample N 1
< 5 ppb
4.05 mg/ l ± 0.44 %
0.78 mg/ l ± 0.53 %
< 5 ppb
<5 ppb
22.12 mg/ l ± 1.17 %
0.45 mg/ l ± 19.04 %
-

Sample N 2
< 5 ppb
0.13 mg/ l ± 1.37 %
0.23 mg/ l ± 1.78 %
< 5 ppb
< 5 ppb
< 5 ppb
< 5 ppb
38.47 mg/ l ± 0.61 %

Sample N 3
0.07 mg/ l ± 31.51 %
0
796
26. 58mg/ l ± 0.84 %
< 5 ppb
360
3 mg/ l ± 0.14 %
1.07 mg/ l ± 0.95 %
273

Sample 1: Drainage waters, collected from the East side of Plant for Color Metals (PCM) –Plovdiv;Sample 2. Drainage waters, collected from the West side of waste ore pile;
Sample 3. Leached solution of clinker, collected from waste ore pile with temperature 80-90 ºС (hot pile)

30 min at 220 rpm, and than were settled
for 30 min and processed as the water samples.
Test-organism Selenastrum capricornutum Printz - resemble to the strain Rhapidocelis subcapitata ATCC 22662, used in...