Plankton composition of Hakaluki Haor of Moulvibazar, Bangladesh

In the present study, physicochemical and biological variables related to the water quality of Hakaluki Haor were studied. Three study stations viz. Bakshimul, Jalabeel and Dudhai were investigated because of an event of mass scale of dead fish and other aquatic organisms were reported. The stations had water depths from 2.74 - 5.13 m and Secchi Disc Transparency were 0.74 - 1.91 m. The air and water temperature among the three stations ranged from 28.2 - 30.4°C and 21.8 - 28.8°C, respectively. TDS ranged from 35 - 42 mg/l, while the electric conductivity of water showed 40 - 50 μS/cm. SRP, nitrate and SRS ranged from 10.68 - 12.32 μg/l, 0.116 - 0.122 mg/l and, 16.08 - 35.42 mg/l, respectively. The concentration of DO was very poor which ranged from 2.8 - 5.4 mg/l. In all the three studied stations, the free CO2 concentration was 0.096 mg/l. Chlorophyll-a value was moderate in all the three stations (ranged within 34.67 and 40.60 μg/l). The phaeopigment concentration was low and ranged from 1.51- 8.72 μg/l among the studied stations. Concentration of ammonia was much higher (1.03 - 1.72 mg/l) than the standard value for Bangladesh (0.5 mg/l). From this analysis, it is observed that during fish kill event the concentration of ammonia was higher with low DO content which might have resulted because of the decomposition of upper foliar parts of the rice plant due to the sudden inundation. Gross α and β counts were found to be 0.01 and 0.10 Bq/l in the Haor water at the time of fish kill. From the planktonic community, 16 phytoplanktons from green algae, 14 euglenoids, 5 diatoms, 5 dinoflagellates and 12 zooplankton species were recorded. A shift in the pH of the Haor water from acidic to alkaline might have occurred during the last 3 decades. A detailed limnological study covering the climatic seasons of Bangladesh has been recommended to be carried out for Hakaluki Haor. Dhaka Univ. J. Biol. Sci. 30(1): 69-78, 2021 (January)

The natural radioactivity in drinking water by gross alpha and beta measurements and radiological quality assessment

The aim of this study is to investigate the radiological quality of drinking waters consumed in Nevşehir province which is the most important tourism destination of the Cappadocia region. The activity concentration of gross α- and β-emitting from natural radionuclides (238U, 234U, 230Th, 226Ra, 210Po, 232Th and 210Pb, 228Ra and 40K) in 21 tap water samples supplied by municipal pipelines were analyzed by using a gas proportional α/β counter. The average activity concentrations of the gross α and gross β in tap water samples were found as 88 ± 10 mBq L−1 and 305 ± 32 mBq L−1, respectively. The average natural activity concentrations of α- and β-emitting radionuclides in tap water samples are below the limit values recommended by the Turkish regulation and WHO. For all samples, except for one sample, the gross β activity concentrations are higher than the corresponding gross α concentrations. The average annual effective radiation dose (AERD) due to the ingestion of these water samples was estimated to be 43, 60 and 124 μSv year−1 for infants, children, and adults, respectively. The average of AERD estimated for adults is 24 % higher than the dose limit of 100 μSv year−1. The activity concentration results reveal that tap water samples are acceptable for human consumption in accordance with the Turkish regulation and WHO recommendations for drinking water.