组配/改性材料对镉砷复合污染土壤的钝化修复

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

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。

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.