Poultry Litter Biochar as a Gentle Soil Amendment in Multi-Contaminated Soil: Quality Evaluation on Nutrient Preservation and Contaminant Immobilization

Abstract

Poultry litter biochar (PLB) has great potential for carbon (C) sequestration, which has been confirmed in the previous study. The promising potential of PLB for nutrient preservation and contaminant immobilization, however, has not been well studied. A multi-contaminated soil, mainly contaminated by chrome (Cr), copper (Cu), nickel (Ni), and zinc (Zn) was selected for this short-term incubation study. The purpose of this study was to evaluate the effects of PLB after incubation on the release of available nutrients (phosphorus, P; potassium, K; calcium, Ca; magnesium, Mg) and on the solubility of Cr, Cu, Ni, and Zn. The results of 56-day incubation indicated that hightemperature pyrolysis PLB (>400◦ C) has great potential to raise soil pH, electrical conductivity (EC), and concentrations of P, K, and Mg; however, maintenance of lower Cr and Cu concentrations and a decline in Ni and Zn concentrations were also observed. The solubility of Cr, Cu, and Ni increased with dissolved organic carbon (DOC) increased, suggesting co-mobilization occurred. The solubility of Zn decreased with increased pH, suggesting adsorption by PLB and/or soil. We recommend the use of 5% high temperature pyrolysis PLB (500 and 600◦ C) as a gentle soil amendment to achieve C sequestration, provide available nutrients, maintain low available concentrations of Cr/Cu, and reduce Ni/Zn availability.