Assessment of Water Quality and Heavy Metal Contamination in River Water and Fish Species from the Bangshi River, Tangail, Bangladesh

Abstract

The Bangshi River flows through the industrial regions of Dhaka and Tangail, polluted by various wastes, including industrial effluents. This study assessed water quality and heavy metal concentrations in the river, focusing on two fish species, Tengra (Mystus nigriceps) and Tara baim (Macrognathus aral). Fish samples were taken from one station during the wet season, whereas water samples were taken from three stations throughout the dry season (June to August 2022) and wet season (February to May 2022). The parameters analyzed included water temperature, pH, dissolved oxygen (DO), biological oxygen demand (BOD), total dissolved solids (TDS), electrical conductivity (EC), alkalinity, and the concentrations of heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), and manganese (Mn). Water temperature ranged from 30.5 to 32.3°C during the wet season and 19.91 to 20.5°C in the dry season, remaining within acceptable limits. pH values were within the standard range. However, EC exceeded irrigation standards during the dry season (828 to 903 µS/cm). TDS levels were 83 to 175 ppm in the wet season and 328 to 563 ppm in the dry season, with most dry season samples exceeding fish culture limits. DO values (1.98 to 4.26 ppm) were consistently below recommended levels, while BOD (2.33 to 4.83 ppm) and alkalinity (80.7 to 382.23 ppm) surpassed permissible thresholds, particularly in the dry season. Heavy metals in water were generally within safe limits except for Pb (4.40 to 5.002 ppm). In fish, Pb concentrations exceeded permissible levels (5.35 ppm in Tengra, 4.46 ppm in Tara baim), while Cd, Cu, and Mn were within acceptable thresholds. The elevated Pb levels likely stem from effluents released by glass, textile, and paint industries. These findings highlight potential risks to human health from consuming water and fish from the Bangshi River, underscoring the urgent need for improved pollution control strategies.

Keywords

• water pollution; heavy metals; water quality; bioaccumulation.