International Journal of Research and Innovation in Applied Science (IJRIAS) |Volume VI, Issue IX, September 2021|ISSN 2454-6194 www.rsisinternational.org Page 118 Seasonal Variation of Water Quality Constituents in the Turag River Mir Obaidur Rahman * , Mohammad Zahangeer Alam Department of Environmental Science, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh * Corresponding author Abstract: Unplanned urbanization enhances environmental threats. Environmental threats increases water pollution that creates harmful impacts on the distribution of aquatic species. The present study is focused to evaluate the seasonal variation of water quality parameters in the Turagriver. Water samples were collected from 5 locations in north and south sides of the Turagriver during summer and winter seasons. The quality of water was found jeopardy. Dissolved oxygen (DO) of water samples were detected 4.9 to 5.7 mgL-1 during summer season. In winter, DO was found 0.78 to 0.95 mgL-1. The chemical oxygen demand (COD) was found higher in winter as compared to summer season. Heavy metals (Cr, Ni and Mn) in water samples were found higher than that of standard limit in both the seasons. Disposal of industrial wastewater was found to be the main causes for the pollution of water. It is suggested that disposal of wastewater should be treated properly before discharge into water bodies. Consequently, water will be contaminants free for community people and aquatic species that will help to protect of sustainable livelihood. Keywords: Pollutions, industrial effluents, aquatic organisms, Heavy metals. I. INTRODUCTION ater quality issues are one of the key problems throughout the world in the twenty-first century [1]. Due to climate change these problems are going to be more aggravated in the future, resulting in higher water temperatures, melting of glaciers, and an intensification of the water cycle [2], with potentially more floods and droughts on earth [3]. The most severe impact of water pollution is the lack of sanitation and safe drinking water which affects more than a third of the people in the world [4]. In addition, exposure to pathogens or to chemical toxicants via food chain is increasing because of irrigating plants with contaminated water and bioaccumulation of toxic chemicals by aquatic organisms, including seafood and fish or direct contact with polluted water during recreation. Surface water pollution has been drawing more attention for many decades [4]. Bangladesh has unplanned industries which are not operated according to proper effluent treatment strategies and untreated or partially treated effluent has been throwing into the nearby water body which demolishes the aquatic environment [5]. From manmade activities industrial effluents, agricultural runoffs, land runoffs, municipal wastes, hospital wastes and mine pollutions are the most common factors for influencing biogeochemistry of water body. The government of Bangladesh has focused on industrial development from the last decades for improving living standard of mass people and keeping a constant GDP growth more than 7%. Therefore, the extreme use of water for industrial purpose exerts pressure on surface water and thereby pollutes water resources as proper effluent treatment is not imposed [6]. The Turag River is the upper affluent of the Buriganga, a major river in Bangladesh. Main source of pollution of Turag river water are various consumer goods industries (soap and detergent), garments industries, pharmaceuticals byproducts, lots of tanneries, dyeing industries, aluminum industries, battery manufacturing, match industries, ink manufacturing industries, textile, paint, iron industries, pulp and paper factories, chemical factories, frozen food factories and steel workshop etc. Most of the industries discharge their effluents directly or indirectly into the Turag River without any precaution causing pollution of the surface water. Moreover, many sewerage and municipal sewage drainage system have become a dumping ground of all kinds of solid, liquid and chemical waste that polluted the river bank [7]. Consequently, hard mixture of hazardous chemicals, both organic and inorganic are released into Turag river water resulting in different chemical and biochemical reaction in the river system and thus deteriorate the water quality. For this reason, water causes the adverse effect of surrounding land and aquatic ecosystem as well as creates subsequent impact on the livelihood of the local community [8]. Fresh water, one of the vital elements of the earth, has a strong correlation with all kinds of lives for sustaining [9]. The strategies taken in Bangladesh for saving rivers from pollution have completely failed against recent industrial development [10]. This problem is intensified by unplanned urbanization, industrialization, changes of land use pattern and lack of public awareness. The Turag is an important river in Bangladesh that are flowing through the north side of Dhaka mega city. Rapid industrial growth has been increasing on the bank city of Gazipur at Tongi arena under the Bangladesh Master Plan-1959. A variety of industries like garments, textile, spinning, jute, metal industries, tobacco, pharmaceuticals, chemical, pesticides, food processing, tanneries and many more are located in this industrial zone. The rhythm of proper waste disposal and waste management system has not kept pace with this industrial growth. Therefore, the Turag has been a dumping station for this area and industrial zone. Considering the above idea, the present study was undertaken to analyze the selected water quality W