生物炭对水稻-再生稻体系吸收土壤中Cd和Pb的影响

以矿区周边Cd—Pb复合污染的农田土壤为供试材料,设置0,2.5%和5%(w/w)3个生物炭添加处理,通过盆栽试验探讨生物炭对再生稻吸收土壤中Cd和Pb的影响。结果表明,生物炭施加提高土壤pH和有机质含量,使Cd和Pb从移动性较强的弱酸提取态转化为较稳定的可还原态,且土壤CaCl2提取的有效态Cd和Pb含量分别降低33.23%~53.23%和66.52%~91.45%。同时,生物炭抑制Cd在头季和再生季水稻叶到糙米中的迁移,降低Pb从茎到叶和糙米的迁移,从而减少Cd和Pb在糙米中的累积;在5%生物炭处理下,再生季糙米Cd含量为0.15mg/kg,低于食品安全国家标准限量值(0.2mg/kg);Pb含量比对照处理降低68.18%。此外,再生季糙米中Cd和Pb含量低于头季稻糙米中相应的含量。因此,生物炭可以抑制Cd和Pb在再生稻体内的累积,降低糙米的重金属污染风险。

Effects of Biochar on the Uptake of Cd and Pb from Soil by Rice-Ratoon System

A pot experiment was conducted with three levels of biochar addition (0, 2.5% and 5% (w/w)), to investigate the effect of biochar on the uptake of Cd and Pb by ratoon rice (Oryza sativa L.). The results indicated that biochar addition decreased the accumulation of Cd and Pb both in the main crop and ratoon crop. This could attribute to the following reasons:Biochar addition increased the soil pH and the content of soil organic matter, which consequently promoted Cd and Pb transformation from acid soluble fraction to reducible fraction. The CaCl₂-extraction Cd and Pb concentrations were also reduced in soil, resulting in the decreased uptake of Cd and Pb by rice root. Biochar addition decreased the transfer factors (TF) of Cd from leaf to brown rice both at main crop and ratoon crop, and also reduced the TF_stem-leaf and TF_stem-rice of Pb; therefore, the concentrations of Cd and Pb in brown rice were decreased. The Cd content in brown rice was 0.15 mg/kg inratoon crop with 5% biochar addition, which was below the hygienic standard for rice in China (0.2 mg/kg). And 5% biochar addition reduced Pb concentration in brown rice of ratoon crop by 68.18% compared with the control. What is more, this research also found that Cd and Pb concentrations in brown rice of ratoon crop were lower than those in the main crop. In a word, biochar addition could reduce the Cd and Pb transfer from soil to ratoon rice.