HEAVY METALS IN WATER AND
ZOOPLANKTON OF NOVOSIBIRSK RESERVOIR
Serafima Ya. Dvurechenskaya[1], Nadezhda
I. Yermolaeva (Institute for Water and Environmental Problems, Siberian
Branch of RAS, Novosibirsk, Russia),
Gennady N. Anoshin (United Institute of Geology, Geophysics and
Mineralogy, Siberian Branch of RAS, Novosibirsk, Russia)
Abstract
The results of evaluation of Zn, Pb, Mn, Ni,
Co, As, Cd, Ba, Be, Hg, V and Cu contents in water and zooplankton of
Novosibirsk Reservoir had been obtained. The microelements accumulation
coefficients (Kd) in zooplankton had been determined. Time and
spatial variability of Kd had been discussed. The difference in Kd
values can be explained by the variety of zooplankton organisms over the
reservoir body and self-cleaning capacities of the reservoir.
Introduction
Novosibirsk reservoir (Fig. 1) is one of the greatest artificial reservoirs in the South of the Western Siberia. Its water surface area is 1070 km2, total reservoir water storage is 8.8 km3, and useful water storage is 4.4 km3. The maximum width is 22 km, the length is 185 km, the maximum depth is 23 m, and the average depth is 9 m. Novosibirsk Reservoir and hydropower station were designed and constructed for the purpose of power generation on the Ob River in 1959 (Vasiliev and Savkin, 1996). The total water storage in the reservoir is estimated as the difference in water influx and water discharge through the hydropower development in lower pool. The mean annual runoff of the river is 54.5 km3 and ranges from 39.8 to 73.5 km3 . The maximum monthly runoff can be observed in May and is estimated to range from 6.7 to 18.6 km3. This is the period of intensive filling by volume. The minimum monthly runoff ranges from 1.4 to 1.8 km3 in December. And it is the period of the winter decrease reservoir water storage. The total exchange between different waters in the reservoir is seven times a year on the average.
The lower part of the reservoir (at the dam) looks like a lake. Its width is 22 km, depth reaches 23 m, and length is 65 km. There are intensive wind waves in this part of the water body, causing water mixing. And there is almost no water flow.
The middle part of the reservoir is rather narrow. Its width is less than 4-5 km, depth reaches 12 m, and length is 88 km. There are many islands, putting natural obstacles in the way of wave generation. The water flow velocity is 0.2-0.3 m/s.
The upper part of the reservoir is too wide: its width reaches 8 km, depth is 8 m in the flooded river bed and 2-3 m in the other part of water area, and the length is 35 km. The hydrological parameters of this part of the reservoir are similar to the river. The water flow velocity is 1.5 m/s.
Nowadays the reservoir’s
water resources are exploited for a variety purposes including water supply,
municipal service, recreation, navigation, hydropower generation and flood
control. The reservoir serves as an important source of drinking water in this
region. Thus, water quality and the ecological situation of Novosibirsk
Reservoir are of very importance.
Heavy metals compounds are of very significance for water animals evolution as the regulators of many biochemical processes in natural waters (Moore and Ramamoorthy, 1987). On the other hand, water animals (mainly zooplankton) as well as bottom sediments can be considered as water quality indicators, which characterise the water pollution degree and reservoir water quality (Polukhina, Dvurechenskaya et.al., 1998).
The present paper is concerned with the investigation of microelements contents in some of reservoir ecosystem components: water and zooplankton and analysis of heavy metals accumulation in zooplankton organisms.
Methodology
Samples of water were picked
up with the Molchanov device twice a month during the
characteristic phases of water level controlling. The measurements of heavy
metals content in the water and zooplankton
samples were performed by AAS-technique in the Analytical Center of the United Institute of
Geology, Geophysics and Mineralogy of SB RAS. For heavy metals analyses 1l of
water was filtered through nuclear membrane filters of 0.45µm
diameter with the help of a Kuprin apparatus. The filtrates were conserved with HNO3
of high quality (4 ml per 1l of water). As the microelements content in water samples
was much lower than the AAS-technique detection limits, preliminary
concentration by evaporation was carried out. The concentration coefficients
were not more than 30 as a precautionary measure against interference by the
macroelements. For measuring zooplankton biomass and taxonomic
composition quantitative samples were taken. Zooplankton was collected by filtration
of 50 l of water on a 73-µm-mesh
Apshtien’s net
and preserved in 4% formaldehyde. For AAS analysis the biological specimen were gathered with the help of Dzhedy’s net (Kiselev, 1969;
Kozhova and Melnik, 1978) and then 0.2-0.5g of the samples were
decomposed in nitric acid and next in perchloric acid. The taxonomic composition of zooplankton species
was determined by calculating of organisms from each samples (using
Bogorov-chamber) under a binocular microscope. The evaluation of the elements
content in water and zooplankton by AAS - technique were carried out with a flame or electrothermal
(ETA) atomization using the graphite tube with platform. Zeeman and Perkin-Elmer
AAS-spectrometers were employed. Flame atomization had been done with the acetylene-air
mixture, and for electrothermal atomization HGA-600 - graphite furnace had been
used.
Results
and discussion
Table 1 summarizes the
results of the evaluation of heavy
metals accumulation coefficients in zooplankton organisms. These coefficients
have been calculated as the ratio of the elements concentration in zooplankton
(wet weight) to those in water samples.
Zooplankton organisms have
to be divided onto three groups due to its food types and characteristic interaction with
heavy metals compounds
(Nikanorov et.al., 1983):
· filter - feedeing crustaceans (Cladocera, Diaptomida) can rapidly accumulate heavy metals in contents several times larger than those in water samples;
· thin-filter-feeding and predatory Rotifers (Rotatoria) can accumulate heavy metals. The numerical fluctuation of these water animals may be considered as the reaction on metal concentration increasing.
· predatory crustaceans (Cyclopoida) accumulate heavy metals in very small amounts as usual.
Nowadays 69 kinds of zooplankton
organisms can be observed in the
water of Novosibirsk reservoir. The quantitative composition was as following:
31 types of Rotatoria, 31 types of Cladocera and 12 types of Cyclopoida. The dominates
were: Asplanchna priodonta, Brachionus calyciflorus, Keratella quadrata from Rotatoria, ,
Daphnia longispina, Chydorus sphaericus, Bosmina
longirostris from Cladocera
and Mesocyclops
leuckarti, Cyclops strenuus, Acanthocyclops viridis, Eudiaptomus graciloides from Cyclopoida. These species
of zooplankton constitute not less than 90% of total biomass in summer.
In Chingisy which is too close to the upper
part of reservoir Rotatoria were prevalent in July in species number (from 15
to 37% in quantity). Cyclopoida dominated in biomass quantity (from 50 to 63%
of total zooplankton biomass). As it can be seen from the table 1, zooplankton
organisms mainly accumulate Co, Hg, Mn, Be, Cd in this region.
In the middle part of the reservoir (N. Kamenka
region) the total biomass of zooplankton was higher as compare with those in
the upper part. Cladocera became dominant there, occupying up to 70% in biomass
and 40% in quantitative composition of zooplankton. The increase of Co, Zn, Pb,
and Ba accumulation was observed there. In Ordynka Kd for these
metals significantly decreased. It can be explained by the exchanging of
taxonomic composition of zooplankton on that with the overwhelming composition
community of large forms of Cladocera (Daphnia longispina, Daphnia cucullata).
The lower part of the reservoir where water
flow is almost negligible was characterized by zooplankton composition with the
large forms of Cladocera as dominants. These kinds of hydrobyotic samples
reached up to 90% of total biomass in July. The minority communities of
Rotatoria were observed also. The maximum accumulation of Mn, Be, As, V и Cu were detected
there.
The distiguishable trends of metals
accumulation in the upper (riverine) and lower (lake - land) parts of the reservoir
were evidenced. Metals can be settled in the following consequence by the
reduction of Kd.
In upper part: Сo>Hg>Mn>Be>Cd>Pb>Zn>Ni>Cu>Ba>V>As
In lower part:
Mn>Be>Co>Hg>Zn>V>Cu>Ni>As>Cd>Ba>Pb
Such variation in heavy metals accumulation
appears to be explained not only by the changing of zooplankton composition
from Rotatoria in the upper part of the reservoir to Cladocera in the lower
part. This phenomenon can be arisen due to specific metals concentrating
mechanism by separate organisms of different zooplankton types.
In September air temperature decreased to 16oC
and zooplankton total number and biomass were two or three times less than
those in with summer. Zooplankton taxonomic composition greatly changed under
this conditions. In this case, Cladocera decreased as in quantity (down to 50%
of total biomass only) as in qualitative diversity. Quite the reverse of that
Rotatoria increased in quantity. Simaltaneously there was the changing in
dominants of Cyclopoida: Mesocyclops leuckarti
exchanged by Cyclops strenuus and the
increase of their biomass (up to 35-45%). At this period the sharp reduction of
accumulation of all metals in zooplankton organisms had been observed (table
1).
The comparison of accumulation coefficients of
the investigated metals in different hydrological phases of the year can
establish the obvious dependence of this process upon taxonomic communities,
its diversity and quantitative composition of zooplankton in the reservoir.
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Figure
1. The Scheme of Novosibirsk Reservoir