Assessment of Heavy Metal Bioaccumulation in Selected Fish Species from the River Ganga in Bhojpur District, India

Abstract

The study under consideration investigates the occurrence, distribution of heavy metal in the tissues, and potential health risks of heavy metal pollution in the selected freshwater fish species caught in the Bhojpur area of River Ganga, India. Pre-monsoon, monsoon and post-monsoon seasons Three common species Labeo rohita, Catla catla and the carnivorous Channa punctatus were sampled. Muscle, liver, and gill tissues were analyzed by the atomic absorption spectrophotometry in the presence of lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), mercury (Hg), and arsenic (As) after acid digestion. The results revealed that the metals under study were all found in all the species and tissues. The highest concentration was in Zinc and copper; Zn (approximately 48.1 mg/kg) and Cu (6.88 mg/kg) in liver samples, and mercury was relatively low (maximum 0.19 mg/kg). The tissue-wise accumulation confirmed the metabolic storage patterns which were liver > gills > muscle. The troic level of biomagnification was observed whereby carnivorous fish were found to have higher metal loads compared to herbivorous ones. The bioaccumulation factors obtained were 21-237 with the highest being zinc. The change of season indicated that the concentrations were a bit higher during the post-monsoon season, possibly because of surface run-offs and resuspension of sediments. Health risk assessment based on Estimated Daily Intake (EDI), Target Hazard Quotient (THQ) and Hazard Index (HI) showed that the majority of individual THQ values were less than unity, with cadmium having a THQ of approximately 1.12, and the cumulative HI of more than 4.0, indicating that there were long-term health risks to regular fish consumers. The work provides a quantitative baseline data of the bioaccumulation of heavy metal in the commercially valuable fish species of the River Ganga in the Bhojpur district and the need to have continuous environmental monitoring and pollution control measures to ensure the safety of aquatic life and health protection of the population.