Effects of Flax Straw Biochar on Soil Properties, Fractions and Maize Availability of Lead and Cadmium in Light Sierozem

摘要

Bioavailability of heavy metals can be reduced in acidic soils with biochar amendment but the situation in alkaline soils is not much clear. Effects of four rates (1%, 5%, 10% and 15% w/w) of flax (Linum usitatissimum L.) straw biochar (FBC) prepared at 600oC on the properties of soil, fraction and phytoavailability of Pb and Cd, and plant growth in the simulated Pb (1000 mg.kg-1) or Cd (20 mg.kg-1) contaminated light sierozem were assessed with pot experiments using maize (Zea mays L.) as an indicator plant. The amendment of FBC significantly enhanced the pH value, cationic exchange capacity (CEC) and organic matter of soil (P < 0.05). The BCR sequential extraction results indicated that the acid extractable fraction of Pb or Cd only decreased by 12.80% or 5.56% when FBC was added with the high rate of 15%. The uptake of Pb or Cd by maize shoots scarcely decreased with 1% and 5% of FBC amendment. Significant inhibitory effects of FBC on the growth of maize shoots were observed with FBC amendment at the rates of 10% and 15%. The results could provide a different implication for immobilization remediation of loess soils (e.g., light sierozem) contaminated with heavy metals.