组配/改性材料对镉砷复合污染土壤的钝化修复

为探究不同类型钝化材料对镉(Cd)砷(As)复合污染土壤的修复效果,以黑麦草为供试植物,研究石灰+硫酸亚铁组配(LF)、改性生物炭(MB)和改性桉树屑(MC)对Cd、As的钝化效果及对黑麦草积累Cd、As的影响。结果表明:在土壤pH为8.19,Cd、As含量为6.87、67.59 mg·kg^-1的重度污染土壤中,施加质量分数为0.5%、1%、2%的LF和0.25%、0.5%、1%的MB或MC不会引起土壤pH大幅度波动;不同施加量下LF、MB和MC对Cd的钝化效率分别达21.4%~32.9%、25.2%~29.4%和18.4%~24.9%,对As的钝化效率分别达3.5%~24.5%、3.7%~22.1%和11.8%~18.2%;3种材料可通过静电吸引、络合、沉淀等作用促使两种元素向低活性态转化;LF、MB和MC不同施加量均对黑麦草的生物量没有显著影响,但分别降低了黑麦草地上部6.5%~25.4%、43.9%~48.8%和40.5%~48.3%的Cd含量,33.1%~43.7%、33.6%~38.9%、14.9%~44.4%的As含量;3种材料均可有效阻控黑麦草对Cd、As的吸收与转运。研究表明,实际应用中施加2%的LF或1%的MB、MC均可达到较佳的Cd、As修复效果。

Passivation and remediation of cadmium and arsenic pollution in soil using composite/modified materials

To explore the remediation effect and mechanism of three types of passivation materials on cadmium- and arsenic-polluted soil, pot experiments were conducted. The materials used were lime+ferrous sulfate(LF), modified biochar(MB), and modified eucalyptus chips (MC). The effect of ryegrass on cadmium and arsenic accumulation was also evaluated. Results showed that the application of LF with soil weight ratio of 0.5%, 1%, and 2% and MB and MC with soil weight ratio of 0.25%, 0.5%, and 1% did not cause great fluctuation in soil pH value in a heavily polluted soil with soil pH of 8.19 and Cd and As contents of 6.87 mg·kg^-1 and 67.59 mg·kg^-1, respectively. The passivation efficiencies of LF, MB, and MC for Cd and As were 21.4%~32.9%, 25.2%~29.4%, 18.4%~24.9%, and 3.5%~24.5%, 3.7%~22.1%, and 11.8%~18.2%, respectively. The three materials transformed Cd and As to a low active state through electrostatic attraction, complexation, and precipitation. The three materials had no significant effect on the biomass of ryegrass, but reduced Cd content by 6.5%~25.4%, 43.9%~48.8%, and 40.5%~48.3% in the shoots of ryegrass and As content by 33.1%~43.7%, 33.6%~38.9%, and 14.9%~44.4%, respectively. The three materials effectively inhibited and controlled the absorption and transport of Cd and As by ryegrass. Practically, the application of LF with a soil weight ratio of 2% and MB and MC with a soil weight ratio of 1% can achieve a better remediation effect of Cd and As.