Heavy metal contamination and remediation strategies in peri-urban agricultural soils

Abstract:

Soils within 2 km of industrial zones in Indian cities are being farmed for vegetables and cereals, but how contaminated are they and what can realistically be done about it? This research assessed heavy metal concentrations (Pb, Cd, Cr, Ni, Zn, Cu) in agricultural soils at two distances—0.5 km (industrial fringe) and 2.0 km (peri-urban)—from the Naini industrial area of Prayagraj, Uttar Pradesh, and evaluated three remediation strategies in a pot experiment at Sam Higginbottom University of Agriculture. Soil samples from 30 geo-referenced locations were analysed by DTPA extraction and AAS. Lead and cadmium exceeded Indian permissible limits at the industrial fringe (67.8 and 6.4 mg/kg vs limits of 50 and 5 mg/kg, respectively). The pot trial tested phytoremediation with Brassica juncea, soil amendment with lime (5 t ha⁻¹) + biochar (10 t ha⁻¹), and a non-food crop rotation with castor. After 90 days, Brassica juncea removed 34.7 percent of DTPA-extractable Pb and 41.2 percent of Cd from industrial-fringe soil. Lime + biochar reduced DTPA-Pb by 52.4 percent through immobilization. The combined approach—phytoextraction followed by amendment—reduced bioavailable Pb to 18.3 mg/kg, below the permissible limit. These results provide a practical remediation framework for peri-urban farmers who must continue cropping on marginally contaminated land.