Potential of sewage irrigation for heavy metal contamination in soil–wheat grain system: ecological risk and environmental fate

Abstract

Anthropogenic activities are major cause of environmental pollution with significant risks for human health that can lead to excessive pollutant entry into the terrestrial ecosystem. The present study was conducted to evaluate the impact of bioaccumulation of carcinogenic metals (Cd, Ni, Co, Cr), and mineral elements (Zn, Fe, Mn and Cu) in the wheat irrigated with sewage water and different environmental traits (bio-concentration factor, pollution load index, daily intake of metals, health risk index) were compared to understand the ultimate sink of these toxic metals. The Cd was in range of 2.89–3.04 mg/kg in soil. The Fe and Mn were in range of 2.87–4.16 and 1.54–1.66 mg/kg, while Zn varies from 0.18 to 1.21 mg/kg, respectively. Grain exhibit higher concentration (3.31 mg/kg) of Zn while lowest (1.02 mg/kg) of Ni. Bio-concentration factor (BCF) values of Cd, Ni, Fe and Mn being less than 1.0 indicates lower Ni, Cd, Fe and Mn concentration in grains. BCF varies from 0.46 to 0.80 mg/kg for Cd, 0.31 to 0.41 mg/kg for Ni, 0.29 to 0.44 mg/kg for Fe and 0.15 to 0.73 mg/kg for Mn. Pollution load index (PLI) of Zn and Cd was lowest and highest among the evaluated trace metals, respectively. Health risk index was highest for Zn and Cd while it was < 1 for all other metals that showed no danger to human health. Enrichment factor (EF) of Zn was highest followed by Cd while found lowest in Mn. To minimize the health risks in humans, regular monitoring of wheat crop irrigated with wastewater is highly recommended.