Phytoremediation potential of industrial hemp grown in sewage sludge: Growth performance and environmental impact

This study investigated sewage sludge as a fertilizer supplement, assessed biochar's effect on heavy metal absorption and industrial hemp growth, evaluated hemp's phytoremediation potential, and analyzed heavy metal accumulation in plant tissues. Additionally, it examined if sewage sludge leachate could contaminate groundwater during industrial hemp cultivation. The experiment comprised five treatments: "a" 50 tha(-)(1) sewage sludge, "b" 50 tha(-)(1) sewage sludge and 30 tha(-)(1) biochar, "c" sewage sludge with chemical fertilizer, "d" 30 tha(-)(1) biochar, and "e" chemical fertilizer. Over 120 days, plant growth performance, soil pH, electrical conductivity (EC), and Zn, Cd, Co, Cr, Cu, Ni, and Pb concentrations in plant parts and leachate were measured. Sewage sludge application slightly reduced soil pH but did not affect EC, with soil pH increasing gradually from day 1 to day 120. All treatments, except "d", supported effective plant growth. Heavy metals predominantly accumulated in hemp roots. The bioconcentration factor (BCF) indicated significant accumulation of Zn, Cu, and Cd (BCF >1), while Cr, Pb, Co, and Ni exhibited lower accumulation (BCF 0.1-1.0). Additionally, translocation factor (TF) values confirmed the effective translocation of Zn, Cu and Cd from the root-to-shoot of the hemp plant, indicating its potential for phytoextraction of these metals. Leachate analyses showed low heavy metal concentrations, significantly influenced by plant presence. Initial color values (up to 267 ADMI) substantially decreased (<50 ADMI by day 120), particularly in biochar-amended treatments. In conclusion, sewage sludge demonstrated potential as a sustainable fertilizer for industrial hemp, offering environmental advantages and supporting circular economic principles.