ASSESSMENT OF HEAVY METAL IN SOIL, RICE AND ASSOCIATED HEALTH RISK INSIDE THE STEEL INDUSTRY IN SIRAJGANJ, BANGLADESH (MS Thesis)- Degree Awarded

Abstract:

The present study was conducted to assess the heavy metal in soil, rice and associated health risk beside the steel industry in Sirajganj, Bangladesh. A total of 21 soil and rice samples were collected from seven zones at 50 m intervals, ranging from 200 m to 500 m from the agricultural fields adjacent to the steel industry. Additionally, 5 soil and rice samples were collected from the control sites for comparison. Sampling followed by SRDI methods and was analyzed using Atomic Absorption Spectrophotometry (AAS). The mean concentrations of heavy metals in soil samples from the industrial sites were found in decreasing order: Fe > Zn > Ni > Pb > Cd. The concentration ranges were; Fe (39.14 ± 1.10 to 98.58 ± 2.46 mg/kg), Zn (52.24 ± 2.48 to 71.73 ± 1.86 mg/kg), Ni (23.47 ± 2.54 to 47.17 ± 2.46 mg/kg), Pb (13.72 ± 1.45 to 45.89 ± 1.52 mg/kg), and Cd (0.502 ± 0.03 to 1.225 ± 0.01 mg/kg). All were significantly higher than control sites and exceeded WHO standards, while Fe and Zn also surpassed SRDI standards. ANOVA results indicated significant differences in soil heavy metal concentrations across sampling distances. In rice samples, the concentration of heavy metals also followed the order; Fe > Zn > Ni > Pb > Cd, with ranges; Fe (8.24 ± 0.41 to 18.25 ± 0.97 mg/kg), Zn (3.90 ± 0.66 to 7.13 ± 0.22 mg/kg), Ni (0.54 ± 0.17 to 2.15 ± 0.60 mg/kg), Pb (0.14 ± 0.01 to 1.56 ± 0.29 mg/kg), and Cd (0.009 ± 0.001 to 0.042 ± 0.003 mg/kg. The concentrations of Fe, Ni, and Pb in the rice samples significantly surpassed the WHO and FAO permissible limits and were much higher than those found in the control samples. Though the estimated daily intake (EDI) values for all metals were below the maximum tolerable daily intake (MTDI), the total target hazard quotient (TTHQ) exceeded the threshold of 1.00, indicating potential non-carcinogenic risks. The target carcinogenic risk (CR) values of Ni, Pb and Cd exceeded the USEPA recommended threshold level (0.000001) or residual level (0.0001). Industrial effluents such as furnace slag and wastewater should be treated before disposal. The steel industry should also implement air pollution controls to minimize flue gases emissions.

• Supervision