چكيده انگليسي :
The survey of "Study on water quality (biotic, abiotic and environmental pollutant parameters) of Azad Dam (Sanandaj) in order to fisheries activities" was conducted in 2014-15. The main objectives of this study were to compare the water quality status of the dam according to the environmental pollutants (metallic elements, detergents and agricultural pesticides), biotic (microbes) and abiotic parameters, surface water quality indicators (IRWQISC) and trophic state index with standards in various uses, with emphasis on fishery activities. Determination of metal elements (lead, cadmium, arsenic and mercury) was in fish samples and hydrocarbons compounds were in sediment. The parameters of chlorine, phosphorus and detergent pesticides, as well as physicochemical, chlorophyll-a and microbial parameters were determined in water samples. Based on the results, DO concentration was more than 5 mg/l and mean values of TP, TN, TA, TH and pH were 0.048±0.033, 1.52±0.32, 50±10, 147±13 mg/l, 7.89±0.37 and EC and TDS were ranged 290±40 μs/cm and 145±40 mg/l, respectively. In addition, mean values of BOD5, COD, NH3 and NO2/N were observed 2.18±1.48, 9.28±8.78 mg/l, 1.57±2.58 μg/l and 0.005±0.004 mg/l, respectively. The mean of chlorophyll concentration (8.56 ± 0.81mg/m3) in rainy months (November, December, January, February, March, April), was 9 times higher than dry months. The overall mean of TSI (49) indicates to the mesotrophic status of the reservoir. The trophic state was generally higher at riverine stations (4 and 5) in all seasons. The stepwise regression test showed that there was a significant negative correlation between water transparency and chlorophyll-a (beta coefficient: -0.36 and coefficient of correlation: 0.13). Calculating of IRWQIsc showed that approximately 59, 40 and 1 percent of the total data were in classes 1 (very good), 2 (good) and 3 (fairly good) respectively. The mean IRWQIsc of surface water indicates a very good quality of all stations (1 to 5). In the rainy season, the decrease of IRWQIsc had a significant correlation (Pearson) with the increase of the trophic state index (based on nutrients) (r = -0.30). Pearson correlation between chlorophyll-a and climate factors (precipitation and air temperature) showed the significant positive correlation. Microbial survey showed that the maximum (13000 CFU/100ml) and minimum (40 CFU/100ml) count in Agust and January respectively in station 5. The geometric mean of the total coliform was approximately %3 of total count of microbes. The mean values of total count and total coliforms were not significantly different (ANOVA, P>0.05) in stations and zones (littoral and limnotic). While the 2 parameters were different among months (ANOVA, P<0.05). The results also showed very low proportion (<0.01 of CFU/100ml) of fecal streptococci and fecal coliform in culture microbe media. According to the results of the main component analysis (PCA), the trophic level index and chlorophyll-a concentration were in the first main component, which they made the most important factors affecting the water quality of the dam. The water quality index and it depended parameters (DIP, BOD5 and total coliform) were in the second component.
In this study, concentrations of lead, mercury and cadmium (μg/g dry weight) in different fishes was obtained (2.72 ± 0.57), (0.55 ± 0.09) and (0.32 0.06) respectively. The mean of lead and cadmium concentration in fish with a weight less than 100 grams was more than fish with a weight greater than 100 grams. However, the concentration of mercury element in these two groups of fish was not different. The arsenic element was higher in fish with a weight greater than 100 grams. The concentration of agricultural chlorine pesticide components in the water showed that only 2% of the total data was in concentration of more than 2 μg / l. These pesticides were Lindane from the BHCs group and Aldrin group from the Drins group. Phosphoric agricultural pesticides such as diazinon, ethion, malathion, parathion, azinphos methyl were less than the diagnostic values. The maximum and minimum concentration of detergent (LAS) in water were obtained at station 5 (326.0 mg / l) and station 1 (082/0 mg / l) respectively. The maximum and minimum amount concentration of hydrocarbons compounds (PAHs 16) (μg / kg dry weight) in sediments were determined at station 1 (50 μg / kg dry weight) and station 2 (14 μg / kg dry weight), respectively.
Generally, the range of physicochemical parameters in water were suitable for fishery activities (farming of warm water and cold water fish) with comparison the standard values. Based on the microbial counting, low organic contamination (due to sewage sludge, grazing) was not supported the microbial growth. The retention time of water in the dam was also suitable for self-purification and microbial removal. In addition, a small number (less than 0.1 CFU / 100ml) of fecal coliform and streptococci in all water samples indicated that the water was not polluted by fresh fecal microbes as well as resistant and old form. According to the mean of IRWQIsc (88, very good quality), this dam has potential for fishery activities and farming of sensitive fish. The annual mean of TSI (49) indicates to alert conditions for salmon fish as well. Therefore, in spite of the accepted quality of dam based on the IRWQIsc, the water of dam is not suitable based on the TSI, for salmon farming, but according to the values of the trophic level index, the dam is suitable for the production of resistant fish. Therefore, management challenges will be required to maintain the trophic level within the mesotrophic to meso-euotrophic range (corresponding to TSI of 40-60) in the case of fish farming in the lake.
