Ecotoxicological assessment of water quality and ecosystem health: a case study of the Volga river / Moiseenko T. I., Gashkina N. A., Sharova Yu. N., Kudryavtseva L. P. // Ecotoxicology and Environmental Safety. - 2008. - Т. 71, № 3. - С. 837-850.

Т.I. Moiseenko et al. / Ecotoxicology and Environmental Safety 72 (2008) 837-850 839 An integrated impact dose is determined by summing the excess for each revile concentration of toxic compound to their MPCfiSheiy as follows: = E MpCjsheiy’ where Itox is the integrated toxicity index, Q is the concentration registered in water, and MPCfiSheiy is the MPC for toxic substances accepted in Russia for fishery and aquatic life. According to Russian rules of water protection, the water quality may be considered good if ItCK is no more than 1 (0</tox_is$l). Water quality may be considered good if 7t0x-i is no more than 1. 2.2. Bioaccumulation For determination of the metal content of the bodies of fish, subsamples from a minimum of five individual fish from every site were collected from the gills, liver, kidneys, muscle, and skeleton. Samples of fish organs and tissues for metal analyses were dried to their constant weight at 105 °C. Dry samples were prepared for analysis by wet digestion in ultrapure nitric acid (10 ml acid for 1g of tissue). The content of Ni, Co, Cd, Cr, Mn, Pb, Cu, Zn, Al, Sr in fish was determined on an atomic-absorption spectrometer, using a graphite furnace HGA-400. Duplicate analyses were used for the purpose of quality control. In analyzing essential elements (Cu, Zn, Co) additional information about climatic variation along Volga River was also used, that is sums of annual temperature exceeding +10 °C taken from climatic map. 2.3. Fish pathology This was aimed at revealing the effects of toxic substances. Fish were studied at 13 river sections; the minimum number of fish observed was 50 of the same age (from 4+ to 6+ years old); all were free of internal parasites in the time period of the investigation (August and early September). Blood samples are taken from live fish tail artery using methods described elsewhere. In the blood samples thus taken, hemoglobin concentration, erythro­ cyte sedimentation rate (ESR), erythrocyte and leukocyte concentration. Blood smear examination allows the analysis of red blood composition, differential blood count, and the detection of occurrence of pathologic blood corpuscles (Ivanova, 1976a, b; Krylov, 1980a, b). Macrodiagnostics to determine fish health were carried out under field conditions. The clinical and pathological anatomical signs of intoxication and any abnormalities were documented on the basis of visual examination of the fish during the first hour after fishing. In the process of visual examination, special attention paid to the following: the intensity of color, the state of pigment (cells-melanophores); the total amount of mucus on the fish body; the state of squama, opercula, oral cavity, anus; the cases of hyperemia, subcutaneous hemorrhages, sores, or hydremia of the body; deformation of skull and skeleton bones; the state of eye crystalline lens and cornea. When the opercula are opened, branchiae are examined, in particular, their color, the presence and the amount of mucus, the state of branchial petals (accretion, adhesion, dilatation, or thinning down). After the abdominal cavity is dissected, the state of fish muscles is studied (color, consistence, hemorrhages, attachment to bones), as well as the presence of exudate in the abdominal cavity, the amount of cavitary fat, its color and density. The topographic location of viscera (liver, kidneys, gonads, spleen, heart, stomach, intestines), their dimensions, color, density, edges, hemorrhages, zones of necrosis, etc., are studied. Mucous membranes of dissected stomach and intestines are examined, in addition to cerebrum, paying special attention to filling of vessels, their color and density. For more precise microdiagnostics, the organs of fish with overt signs of pathology were removed for histological analysis. Histological sections were prepared in the laboratory according to the standard method (Bucke, 1994). For satisfactory histological preparations, only freshly killed fish were considered. Gills, kidneys, liver, and gonads were handled rapidly to prevent degenerative changes within the specimen. They were carefully dissected from the body, cut into blocks of < lc m 3 and placed in a fixative (Bouin’s fluid). Histopathological alterations of organs were evaluated under a light microscope (450 x ). Diagnosis of disease was confirmed on the basis of histopathological observations. The percentage of sick fish in the stock of each local polluted zone was documented. Fish were detected at various stages of disease ranging from initially insignificant pathological organ changes to serious compromise of the organism. In the process of macrodiagnostics, three stages of disease can be identified (0 denotes healthy individuals): (1 ) Low-level disturbance, not threatening the life of the fish. (2 ) Medium-level disturbances, causing a critical state in the organism. (3 ) Distinct signs of intoxication leading to inevitable death of the organism. The overall index of morbidity in fish in a given zone of contamination can be presented as 7 + 2 N2 + 3 N3 Ntot Here, Z is the morbidity index for fish, 0s$Zs$3; Ni, N2, and N3 are the numbers of fish in the first, second, and third stages of the disease, respectively; and Ntot is the total number of fish examined in the local contamination zone, including healthy individuals. If none of the fish in a given body of water demonstrates any signs of intoxication, then Z = 0. The value of Z will increase with an increase in both the number of sick fish and the severity of their diseases. 2.4. Statistics Statistical data processing was carried out using the regression analysis; the significance of correlation coefficients was determinated by t-criteria. 3. Results 3.1. Concentrations o f toxic substances in water 3.1.1. Metals and metalloids The microelement concentrations in the water were relatively low in the investigated river sections: the concentrations of Mo, Cd, Co, and Cr were less than 1 j.ig/1, those of Se and Pb varied from less than 1 to 1.7 j.ig/1, those of Ni, V, and Cu varied from less than 1 to 2.8 i-ig/1; the concentration of Zn varied from 1 to 6.2 j.ig/1; and that of As from 1 to 4.2 j.ig/1 (Table 1). Relatively high concentra­ tions of Mn and Sr were observed. The concentration of mercury did not exceed the accuracy of its determination using our technique ( < 0.05 j-ig/1). Relatively low concentrations of the investigated elements (especially Zn, Ni, Cd, and Cu) can be explained by the absence of ferrous and non-ferrous metallurgical plants in the region under consideration, as well as by the overall decrease in the level of Volga River water contamination observed after the recent economic crises. Comparison of the element concentrations in the Volga River with the respective “background” values for overland flow in European Russia (Petrukhin et al., 1989; Burtseva et al., 1991) showed that the concentration of As was higher than its “background” value in all the investigated areas; the concentrations of Ni and Cd exceeded the background level near the dam of the Kuibyshev Reservoir; whereas the “background’ concentrations of Cu and Se were exceeded in the central part of the Gorkii Reservoir. It is a well-known fact that zones of atmosphere and land contamination can be found within the catchment areas of the Kuibyshev, Saratov, and Volgogradskoe reservoirs, as well as in the Lower Volga (Koronkevich and Zaitseva, 2003). This probably explains the exceeding of “back­ ground” concentrations by such elements as V, Se, Pb, Ni, and Co. The concentration o f Mn in the Ivankovo and Gorkii reservoirs, as well as the concentrations of V and Cu in the Kuibyshev Reservoir, the Lower Volga and the Volga River delta, were higher than the respective MPC values (List of Fishery Standards, 1999), estab­ lished for fishery water bodies. Thus, the pattern of element concentration distribution within the investigated areas reflects, primarily, overall diffuse pollution, which is formed against the background of the natural geochem­ ical input of microelements and is mainly due to pollutant discharge by fuel and energy plants and general economic activity within the catchment area. 3.2. Toxic organic compounds Dangerous organic substances include oil products, cyclohex- ane and cyclopentadiene and their derivatives, sebacic acid ether, xylene, phthalates, and dioxanes (Table 2). A high level of water