The chemical elements are natural components of the aquatic environment, but their levels can be increased due to emissions and discharge from the coal-fired power industry. These sources of pollution can affect the quality and quantity of fish stocks. Many researchers reported the environmental impact of coal power (Kolker et al. 2006, McConnell, Edwards 2008, Czarnowska, Frangopoulos 2012, Sikhynbaeva et al. 2014, Chanchal et al. 2016, Zholobova et al., 2016, Huang et al. 2017). In particular, Sikhynbaeva et al. (2014) noted that with a plant capacity of 1 million kW, 50 mln m3 of wastewater enriched with 52 tons of sulfuric acid, 26 tons of chlorides, 41 tons of phosphates, 500 tons of suspended solids and 360 tons of ash stored in dumps go to waste. Huang et al. (2017) found that the soils around the coal-fired power plant are contaminated with Cd, Hg, As, Cu and Cr. Under these conditions, it is essential to assess and predict all possible changes in water ecosystems under external and internal factors – flows of matter and energy and assessment of optimum conditions use of ecosystems (Alimov 2000, Scheffer and Van Nes 2007, Alimov et al. 2013). Even relatively low contents of chemical elements in water and soils are bioactive and can be accumulated in fishes (Nikanorov, Zhulidov 1991, Sani 2011, Afshan et al. 2014, Hashim et al. 2014, Nzeve et al. 2014) and result in various physiological changes and deformations in their anatomical and morphological structures, including genetic defects (Ayllon, Garcia-Vazquez 2000, Jezierska, Witeska 2001, Vosylienë, Jankaitë 2006, Ergene et al. 2007, Vinodhini, Narayanan 2009, Afshan et. al. 2014, Pandey, Madhuri 2014, Gorlacheva, Afonin 2017, Mataphonov, Shoydokov 2020). Within this framework, the data on chemical element contamination of the ichthyofauna of Lake Kenon, employed for recreation and industrial fishing, are not available. From 2012 to 2016, we studied the migration of chemical pollutions in living organisms (plankton, benthos, vegetation and fishes) as well as the distribution of metals in the water systems – in the aquatic environment and in the effluent of ash dump – which fell into Lake Kenon. We assumed that chemical substances transferred to the lake with filtration water from the ash dump and wastewaters from the thermal power station No. 1 (TPP-1) are concentrated in water and the bottom deposits and represent a potential source of secondary pollution for the ecosystem.
In this study, we cover the concentrations of Cr, Mn, Cu, Zn, Hg and Pb in the fish of Lake Kenon and possible reasons for their accumulation. Being included in a human diet, the muscle tissue of fishes was used as a biological indicator of ecosystem contamination. The feed preferences of the hydrobionts were thoroughly analysed as the source of chemical pollution exposure and determination of the ecological niche of fish. The findings will help to explain the path of potential pollution of fish with chemical substances and implement management decisions on the recovery of the ecosystem of Lake Kenon.
Lake Kenon is situated in the limits of the city of Chita, Transbaikal Territory, and located at latitude 52°04.362' N and longitude 113°21.432' E at an altitude of 653 m a.s.l. (Fig. 1). The catchment area of the lake is 227 km2, the surface area is 16 km2, the average depth is 4.4 m, the largest depth is 5.2 m, the length is 5.7 km, the average width is 2.8 km and the shoreline length is 17.4 km (Itigilova et al. 1998). Lake Kenon is a natural lake of the Amur River basin. Lake Kenon is used as a cooling pond for TPP-1 since 1965. Some abiotic indicators of Lake Kenon are shown in Figure 2. According to these data, Lake Kenon is a fresh-water body with an average level of salinity (TDS = 548 ± 25.1 mg L−1). pH values indicate alkaline conditions and with a sufficient amount of dissolved oxygen. Hydrocarbonate composition of surface and underground waters is typical for these zonal and climatic conditions (Zamana et al. 1998, Zhuldybina 2010, Zamana et al. 2011). The hydrochemical composition of lake waters from a two-component – sodium hydrogen carbonate until the 60s of the last century was transformed into a three-component – sulfate-hydrocarbonate-chloride sodium-calcium-magnesium (Tsybekmitova 2016, Usmanova et al. 2018) (Table 1). The water composition change was due to the ash dump leakage. Approximately, 2.2–2.4 thousand tons of sulphates enter the lake annually (Zhuldybina 2010).
Dominantions of water (mg/L−1) in Lake Kenon in years 2000–2018.
Parameter | Na+ | K+ | Mg2+ | Ca2+ | HCO3− |
|
Cl− | TDS |
---|---|---|---|---|---|---|---|---|
Minimum | 49.3 | 2.1 | 36.8 | 48.1 | 93 | 196.9 | 68.1 | 495 |
Mean | 54.4 ± 12.0 | 2.2 ± 0.1 | 42.5 ± 9.6 | 55.0 ± 14.2 | 131.8 ± 49.5 | 225.2 ± 87.8 | 55.0 ± 12.1 | 548 ± 64.4 |
Maximum | 60.2 | 2.2 | 47.2 | 64.8 | 164.7 | 239.2 | 33.1 | 594 |
In the present report, we investigate species dominant in the fish community of Lake Kenon –
Selected morphometrical and biological characteristics of the fishes collected in Lake Kenon.
Species | Weight range (mean) | Length range (mean) | Age | Number of individuals | Male / Female |
---|---|---|---|---|---|
[g] | [cm] | [years] | |||
76–246 (169) | 13–19 (16) | 4+ – 5+ | 15 | 5♂/10♀ | |
44–100 (73) | 13–18 (15) | 3+ – 4+ | 15 | 6♂/9♀ |
Immediately after collection, fish samples were put in a clean polythene bag to transport the fish samples to the laboratory of the Institute. In the laboratory, captured ichthyologic material was immediately analysed: each fish sample under study was identified to species and their lengths and weights were measured. Afterwards, the ages of the fishes were determined by interpreting sampled scales. The samples of fish muscle and food components were washed with distilled water and were cut into small pieces (2–3 cm), were then air-dried to remove the extra water and were then oven-dried until the constant weight was obtained. Samples were subsequently sent to the laboratory of the Institute of Microelectronics Technology and High-Purity Materials of the Russian Academy of Sciences (Chernogolovka, Moscow, Russia). Chemical elements in samples were determined by atomic emission spectrometry (iCAP-6500, Thermo Scientific, USA) and mass spectrometry (X-7, Thermo Elemental, USA). All samples were analysed for the presence of Cr, Mn, Cu, Zn, Pb and total Hg. These chemical elements are of the greatest concern in toxicology (Spry, Wiener 1991, Pandey, Madhuri 2014), although Cr, Mn, Cu and Zn are essential for normal physiological processes (Heath 2002). The accuracy of the analytical procedure was checked by the analyses of certified reference materials: for water – Certified Reference Material “Trace Metals in Drinking Water”; for bottom sediments – Certified Reference Material No. 521-84Ï “SGD-1A”, Essexite; for fish material – muscle tissue of
Results of analysis (μg g−1) of standard reference material (BOk-2) in comparison with certified values.
Metal [n = 6] | Limit of quantification | SRM, Baikal perch tissue, BOk-2 | Measured BOk-2 | Recovery [%] |
---|---|---|---|---|
Cr | 5.100 | 0.80 ± 0.1 | 0.29 | 36 |
Mn | 0.050 | 1.70 ± 0.3 | 2.10 | 123 |
Cu | 0.040 | 1.90 ± 0.3 | 1.10 | 58 |
Zn | 0.070 | 23.00 ± 2.0 | 23.00 | 100 |
Hg | 0.160 | 0.50 ± 0.2 | 0.39 | 78 |
Pb | 0.012 | 0.37 ± 0.1 | 0.26 | 70 |
We used two factors to evaluate the chemical element concentrations in fish: the bioaccumulation factor (BAF) and the trophic magnification factor (TMF). The chemical element concentration was compared with the maximum permissible limits (RF) and EPA (US) standards. BAF was used to evaluate the chemical element concentrations in fish tissues and was calculated as the ratio of the concentration of pollutant (chemical elements) accumulated in the tissue of organism with respect to the concentration of chemical elements in surrounding water using the following formula (Jezierska, Witeska 2001, Van der Oost et al. 2003):
Cfish is the concentration of chemical elements in fish tissue mg kg−1, Cwater is the concentration of chemical elements in surrounding water (mg L−1).
If BAF is greater than or equal to 1, biological objects tend to accumulate metals.
As consumption and accumulation of a greater part of chemical elements in fish mainly result from feeding, we analysed the level of metal in the stomach content (food components). We calculated TMF to interpret the results of chemical element accumulation in trophic levels of the ecosystem. TMF reveals the relationship between the chemical element concentration in predator and the chemical element concentration in prey. The equation is as follows (Dobrovolsky 2003):
Cpredator is the concentration level of chemical elements in the organism or organ of predator, Cprey is the concentration level of chemical elements in the organism of prey.
The findings on chemical elements content in fish tissues were analysed with Microsoft Excel 2010 and STATISTICA 10 for Windows (Copyright © StatSoft, Inc). The statistical significance was set at
Previous studies showed that the ash dump leakage, rich in S, Cr, Mn, Cu, Zn, Hg and Pb, flows into Lake Kenon (Tsybekmitova 2016). Table 4 shows the contents of chemical elements in the aquatic environment. Our investigation revealed that water contained low concentrations of the studied metals. With the exception of copper, the trace metal concentrations in water did not exceed EPA, but Cr and Hg were compared to national standard MPL (Table 4). The contents of the other chemical elements fell below MPL and varied (mg L−1): Cr (from 0.7 to 1.5), Mn (from 2.3 to 6.8), Zn (from 1.6 to 4.0) and Pb (from 0.29 to 2.6). The comparison of received mass concentrations of chemical elements with Clark's value for sedimentary rocks revealed that bottom sediments in Lake Kenon contained low concentrations of the studied metals (Table 4).
The concentrations of chemical elements in the aquatic environment, bottom sediments, and food organisms of the fishes in Lake Kenon.
Ñomponents | Unit | Cr | Mn | Cu | Zn | Hg | Pb |
---|---|---|---|---|---|---|---|
Water | |||||||
n = 20 | μg L−1 | 1 | 4.00 | 0.86 | 2.70 | 0.18 | 0.16 |
SD | 0 | 1.78 | 0.11 | 1.04 | 0.08 | 0.07 | |
MPL | μg L−1 | 1 | 10.00 | 5.00 | 10.00 | 0.10 | 6.00 |
EPA | μg L−1 | 50 | 50.00 | 1.00 | 5.00 | 2.00 | 50.00 |
Bottom sediments | |||||||
damp 70%, n = 25 | μg kg−1 | 13874 | 33 | 24535 | 43243 | 25 | 12072 |
SD | 2114 | 10 | 3351 | 3694 | 20 | 2375 | |
Ccrust | μg kg−1 | 100000 | 900000 | 55000 | 70000 | 70 | 14000 |
The food organisms from the stomach of the fish | |||||||
μg kg−1 | 200 | 170563 | 1066 | 3488 | 5 | 320 | |
SD | 94 | 1232 | 255 | 1144 | 2 | 81 | |
Amphipods, n = 7 | μg kg−1 | 86 | 4920 | 9970 | 10400 | 16 | 70 |
SD | 15 | 303 | 117 | 1130 | 8 | 16 | |
μg kg−1 | 500 | 23500 | 3570 | 14900 | 7 | 464 | |
SD | 30 | 1810 | 160 | 5200 | 1 | 20 | |
DL, biota | μg kg−1 | 20 | 50 | 40 | 70 | 4 | 10 |
SD – standard deviation, MPL - the maximum permissible limits (approved by the Order of Federal Fishery Agency of the RF No. 20 as of January 18, 2010), EPA – Environmental Protection Agency (EPA 2002), Ccrust – elements clarke in the Earth's crust (Kabata-Pendias and Mukherjee 2007), DL – the detection limit of the method.
The feed preferences of the dominant fishes in Lake Kenon are shown in Figure 3.
The concentrations of heavy metals in muscles and food bolus are shown in Table 5. In the muscles of
Chemical elements in the fishes (N=10) of Lake Kenon (mg kg−1 of dry matter).
Fish species | Cr | Mn | Cu | Zn | Hg | Pb |
---|---|---|---|---|---|---|
In the muscles | ||||||
0.18 ± 0.03 | 0.85 ± 0.15 | 0.91 ± 0.13 | 30.8 ± 4.36 | 0.47 ± 0.17 | 0.73 ± 0.10 | |
0.23 ± 0.06 | 1.00 ± 0.25 | 1.20 ± 0.37 | 82.5 ± 56.00 | 0.27 ± 0.11 | 0.58 ± 0.09 | |
MPL | 1.00 | 1.00 | 10.00 | 40.00 | 0.30 | 1.00 |
EPA | – | 0.05 | 1.00 | 5.00 | – | 0.05 |
In the food components of the fish stomach | ||||||
0.029 ± 0.004 | 277 ± 14.5 | 18.7 ± 6.2 | 179.9 ± 54.9 | 0.55 ± 0.08 | 0.19 ± 0.06 | |
13.60 ± 4.21 | 485 ± 53.0 | 80.8 ± 14.5 | 673.5 ± 167.8 | 0.45 ± 0.01 | 3.07 ± 0.03 |
The levels of chemical elements in the water, bottom sediments and food organisms from the stomach in dominant fishes are shown in Table 4. BAF and TMF for the fishes were calculated from those values (Figs 4 and 5). BAFs of chemical elements accumulated from the surrounding water for
Component analysis singled out two factors that totaled up to 69.84% (Fig. 6). Other factors were considered being insignificant in total variance. PCA revealed the following characteristics of the metal–species correlation. In the muscles of
The lack of advanced clean coal combustion technologies for coal-fired power plants results not only in atmospheric chemical pollution but also in the pollution of water ecosystems. Chemical pollutions change the quality of lake waters, accumulate in hydrobionts, and interfere with the biodiversity and structure of the lakes populations (Sunda, Guillard 1976, Nikanorov, Zhulidov 1991, Heaven et al. 2000, Cardwell et al. 2002, Tulonen et al. 2006, Moiseenko et al. 2005, Pastukhov 2012, Moiseenko, Gashkina 2020).
Our investigation revealed that water and bottom sediments in Lake Kenon contained low concentrations of the studied metals. Although in Lake Kenon, Hg exceeds the background value more than three times, which is comparable with polluted waters. The background values of the concentration of Hg in freshwater bodies of European and Caucasian Russia, and in those of the Tien Shan Mountains, were evidenced in the study by Nikanorov Zhulidov (1991) and estimated as equal to or less than 0.05 mg L−1. The research (Chale 2002) has shown that concentrations of trace metals of water were lower than that in fish tissues, which is consistent with our research. The self-cleaning ability from water ecosystems where aquatic organisms a purify waters polluted plays a role here (Moiseenko et al. 2005, Alimov et al. 2013). As compared to the aquatic environment, the contents of chemical elements in bottom sediments are an order of magnitude higher (Table 4). Such a high concentration in bottom sediments by the fact that metals are bound to organic compounds of plant and animal residuals settling in bottom sediments (Duan et al. 2014). Correlations between chemical elements and organic matter of bottom sediments are well traced in Lake Kenon (Tsybekmitova et al. 2019). Due to the sedimentation of suspended organic matter capable of adsorbing ions and mineral particles from water, the bottom sediments of Lake Kenon are enriched with Mn, Zn, Hg and Pb. Bottom sediments not only function as accumulators of heavy metals but also as one of the potential sources of pollution of the chemical element ecosystem.
The feed preferences of the dominant fishes of Lake Kenon are as follows:
In such reference ecosystems as Lake Baikal, the content of Cr in the muscles of fishes ranges from 0.3 to 0.86 mg kg−1 (Vetrov et al. 1989); in the ecosystem of Lake Kennebec (Maine, USA), the level of Cr in the muscles of
On the biogeochemical barrier, the migration of chemical elements drops drastically and their concentrations begin to rise (Alekseenko 2003). At the same time, chemical elements flowing into water ecosystems are selectively accumulated in organisms through the system of trophic interrelations. In the plant food organisms (
The lack of advanced clean coal combustion technologies for coal-fired power plants results in the pollution of water ecosystems. The findings underline the complicated distribution of chemical elements in fishes due to both exogeneous and endogenous factors of the ecosystem. This study underlines the importance of monitoring the levels of chemical pollutions not only in the water column and bottom sediments but also in the hydrobionts including fish to prevent this type of contamination. In addition, management decisions for mitigation practices in Lake Kenon should be preferably focussed on the disposal of wastewater from the ash dump contaminated with chemical elements.