Ecological risk assessment of potentially toxic elements (PTEs) in agricultural soil, vegetables and fruits with respect to distance gradient in proximity to lead-acid battery industry

Abstract

Lead-acid battery industries in Bangladesh have proliferated in urban areas, leading to the release of significant amounts of potentially toxic elements (PTEs) and metalloids into the environment. This study aimed to assess the spatial distribution, sources, contamination status, and ecological risks in agricultural soils, vegetables, and fruits near these industries. Soil samples were collected from four sites at varying distances (0 m, 100 m, 250 m, and 500 m) around three lead-acid battery industries (AA, AB, and AC) in Dhaka and Gazipur Districts during June-July 2020. The concentrations of the Pb, As, Cd and Zn in agricultural soils were ranged between 8.40–116.61, 8.99–28.21, 0.03–1.28, and 25.38–68.72 mg/kg, respectively. The concentrations of Pb, As, and Cd were found to be considerably higher than background levels across all industries, with a gradual decrease in PTE concentrations from 0 m to 500 m. The contamination factor indicated high to moderate contamination in agricultural soils by As, Cd, and Pb, and low contamination by Zn. pollution load index, modified contamination degree, and nemerow comprehensive index revealed varying pollution levels in the vicinity of the industries, with AA and AB showing higher pollution compared to AC. The individual risk factors demonstrated significant risks associated with Cd and As exposure, while Pb and Zn posed lower risks. The potential ecological risk index indicated considerable ecological risk for AA (risk index = 192.41), moderate risk for AB (risk index = 111.80), AC (risk index = 65.08), respectively. Correlation and principal component analysis revealed strong positive associations (p < 0.01) among the chemical parameters and potentially toxic elements in soils, and demonstrated the lead-acid battery industry as the primary contamination source in the studied areas. There were strong positive relationships (p < 0.01) existed between As, Cd, and Zn in soils and vegetables; while a strong negative association found between As in soils with As in Fruits. The cluster analysis showed EC, OC, OM, Pb, As and Zn into separate group, implied their same source of origin as anthropogenic source. The metal uptake was in the decreasing order of Cd > Zn > As > Pb and Cd > Zn > Pb > As in vegetable and fruit samples, respectively and transfer factor analysis highlighted Cd and Zn as metals with higher absorption rates in vegetables and fruits. Among the industries, AA and AB were significantly impacted on soil quality, and considerable metal accumulation found on vegetables. The human health risk assessment results indicate a potential noncarcinogenic health hazard for the populations surrounding the industries (AA, AB, and AC). This is evidenced by the calculation of the total target hazard quotient and the hazard index, both of which exceeded the acceptable level (>1). However, the carcinogenic health risks arising from the consumption of potentially toxic elements are within threshold values. This study provides crucial insights into the environmental as well as health impact of lead-acid battery industries, emphasizing the urgency of implementing effective environmental management practices to mitigate their consequences.