小麦秸秆生物质炭对碱性土壤中油菜生长和镉吸收的影响

Effect of wheat straw-derived biochar on rape growth and cadmium uptake in an alkaline soil

为探讨小麦秸秆生物质炭对镉(Cd)污染碱性土壤的修复效果,采用序批式吸附试验和Cd污染土壤盆栽试验,研究了小麦秸秆生物质炭施用(1%,m/m)对碱性土壤吸附Cd的影响,以及对Cd污染土壤中油菜生长和Cd吸收的影响。结果表明:Cd在生物质炭上的吸附等温线非线性较强,生物质炭对Cd的表面吸附起主导作用,Cd在生物质炭上的分配系数(Kd)是在土壤上的1.5~3.0倍。生物质炭施用可促进土壤对低浓度Cd的吸附,0.1 mg·L^-1平衡浓度下Kd值提高了19.5%;生物质炭施用可抑制土壤对高浓度Cd的吸附,在10 mg·L^-1条件下Kd值降低了37.2%。生物质炭施用对土壤pH值影响不显著,但缓解了Cd污染对油菜生长的抑制作用,油菜生物量最高提高了45.0%,也抑制了油菜对Cd的富集,油菜富集Cd的量最高降低了40.6%;CaCl2、Mg(NO3)2、NH4OAC、HCl、DTPA和BCR1作为提取剂提取出土壤中Cd的量与油菜地上部分吸收Cd的量相关性较强(线性回归方程决定系数R2>0.8),而Mg(NO3)2萃取出土壤中Cd的量更能预测油菜地上部分吸收Cd的量。研究表明,小麦秸秆生物质炭有利于降低碱性土壤中Cd的生物有效性,但并非通过提高土壤pH值和吸附能力来实现。

We explored the effect of wheat straw-derived biochar on remediation of alkaline cadmium(Cd)contaminated soil by conducting the sequential batch adsorption experiment and pot experiment.The results showed that the sorption isotherm of Cd on biochar was highly nonlinear,indicating that the surface sorption of Cd on biochar was dominant.The distribution coefficient(Kd)of Cd on biochar was 1.5~3.0 times more than that on soil.Biochar application(1%,m/m)to soil promoted the sorption of low-concentration Cd by soil and increased the Kd value by 19.5%at the equilibrium concentration of 0.1 mg·L^-1.In contrast,biochar inhibited the sorption of high-concentration Cd by soil and decreased the Kd value by 37.2%at the equilibrium concentration of 10 mg·L^-1.Biochar application to soil had no significant effect on soil pH.Biochar alleviated the inhibitory effect of Cd on rape growth,which biomass in rape was increased by 45.0%.In addition,biochar application decreased the uptake of Cd by 40.6%in rape.There was a strong correlation between the amount of Cd extracted by CaCl2,Mg(NO3)2,NH4OAC,HCl,DTPA,and BCR1,and the amount of Cd in the aboveground part of rape(R2>0.8).In conclusion,wheat strawderived biochar is beneficial in reducing the Cd bioavailability in alkaline soil;however,this effect is not achieved via increasing soil pH and adsorption capacity.