988330 - Long-Term Effectiveness of Biochars Derived from Agricultural Wastes for Immobilization of Heavy Metals Contaminated Soils (Student Poster 17)

Biochar has been recommended as amendment for the in situ remediation of heavy metals contaminated soils due to its unique properity, such as high stability and specific surface area, that leads to the immobilization of heavy metal in the soil. Most studies only focused on the immobilization of heavy metal for single biochar and the transformation of metal speciation in the soil. Although, the exchangeable fractions of the heavy metal speciation had shown high mobility in the soil, only a few studies investigated the insight in selecting appropriate biochar for heavy metal and the long-term influence on the immobilization of heavy metal in various types of soil. This study aims to investigate the effects of biochar that produced from the agricultural wastes, including rice husk biochar (RHB), rice straw biochar (RSB), corn waste biochar (CWB), sugarcane bagasse biochar (SBB), and pineapple leaf biochar (PLB) on the speciation changes of Cu, Zn, Ni, and Cr in five types of soils within 300 days incubation. The five types of soils are soil without K fertilization (W), soil with long-term K fertilization (L), red soil (R), alkaline soil (A), and forest soil (F). The metal concentrations were 2,000 mg/kg for Cu and Zn; 1,000 mg/kg for Ni and Cr. Pot experiments are conducted by combining biochar with the contaminated soils. After 50-day incubation, all of the biochars can effectively immobilize Cu, Zn, and Ni in contaminated soils aside of Cr. Among all of the biochars, PLB treatments (10%, w/w) showed the highest immobilization of Cu, Zn, and Ni in 5 types of soils. The exchangeable fractions in Cu, Zn, and Ni of W-soil were decreased respectively by 41.41%, 58.70%, and 45.44%, and the Fe-Mn oxide fractions were increased respectively by 35.54%, 24.81%, and 44.99% in PLB treatments. The properties of PLB, such as soil pH, pore size, and zeta potential extreamly affected the transfer of exchangeable fractions to Fe-Mn oxide fractions in 5 types of soils, which was likely due to the formation of Fe oxides/hydroxides, and reduced Cu, Zn, and Ni availability. Results indicate that different types of soils and biochars influence the transformation of speciation of heavy metal in the soil. Overall, this study demonstrates that the biochars, especially PLB, could effectively immobilize heavy metals contaminated soils.