Effect of Sulfur Granular Municipal Solid Waste, Humic Acid, and Nano Fe-Oxide on Lead Uptake by Plants in a Calcareous Soil in the Presence of Thiobacillus

Soil poisoning with heavy metals is one of the most significant aspects of environmental research. In the soil treated with Thiobacillus, the effect of sulfur granular municipal solid waste (sulfur granular MSW), humic acid, and nano Fe-oxide on reducing Pb absorption by plants was investigated. Treatments consisted of applying sulfur granular MSW (۰ and ۳۰ t/ha), spraying humic acid (۰ and ۱.۵ mmol/L), and using nano Fe-oxide (۰ and ۲% w/w) in the soil contaminated with Pb (۰, ۶۰۰, and ۱۲۰۰ mg/kg-soil). Plants were collected after ۵ months, and the Pb content in the soil and plants was estimated by atomic absorption spectroscopy (AAS). The activity of ascorbate peroxidase (APX) and peroxidases (POX) enzymes were also determined. The use of ۳۰ t/ha of sulfur granular MSW in the Pb-polluted soil reduced Pb concentration in the soil and plant by ۱۳.۴% and ۱۵.۱ %, respectively, while it increased Fe concentration by ۱۵.۲% in the plant. Using nano Fe-oxide (۲% w/w) in the Pb-contaminated soil (۶۰۰ and ۱۲۰۰ mg/kg soil) considerably enhanced Fe content in the plant. Pb absorption by plants was dramatically reduced by foliar application of humic acid. According to the findings of this study, the interaction effects of sulfur granular MSW, nano Fe-oxide, and humic acid significantly reduced the Pb absorption by plants. However, the impacts of soil physico-chemical characteristics and the kind of soil pollutant on plant Pb concentration cannot be ignored.