Abstract:

The heavy metal pollution in soil has been paid much attention as it is a threat to ecological safety and human health. The in situ application of fast-growing Salix coupled with micro-nano biochar is a promising technology for remediating heavy metal-polluted soil. In this study, two kinds of phosphorus-enriched biochar (BC and MBC) with different particle sizes (<75 μm and <1.0 μm) were prepared from animal-derived biomass of bone meal, by using high-temperature pyrolysis combined with wet ball milling technology. BC and MBC with various dosages (ie., 0, 0.5%, 1.0% and 2.0%, w%) were added to Cu and Pb contaminated soil, and the effects of BC and MBC on the Cu and Pb chemical forms and bioavailability in the soil, as well as the accumulation and transport characteristics in Salix jiangsuensis ‘172’ (Salix-172) were investigated. The main results are as follows: 1) The analysis of phosphorus enriched biochars using SEM-EDX-mapping, TEM, XRD and FT-IR, which confirmed that the composition of the biochar contains a significant amount of hydroxyapatite and carbon. In addition, the specific surface area and pore volume of MBC increased by 5.93 times and 4.65 times, respectively, compared to BC. 2) Both BC and MBC applications were effective in reducing the soil bioavailable contents of Cu and Pb, and the MBC was more effective at the same application rate. At the application of 2% BC and MBC, the bioavailable concentrations of Cu and Pb was significantly reduced by 6.41%, 17.31% and 8.84%, 30.31% compared to the control (P<0.05), respectively. 3) Compared with the control group, both BC and MBC significantly increased the biomass of Salix-172 (P<0.05) and decreased the Cu and Pb contents in the roots of Salix-172 (P<0.05), while had no significant effect (P>0.05) on the total accumulation of Cu and Pb in Salix-172. 4) Application of 0-2.0% BC had no significant effect (P>0.05) on the BCF and TF of Cu and Pb in Salix-172, whereas 1.0%-2% MBC significantly enhanced the BCF and TF of Cu and Pb (P<0.05). Specially, 2.0% MBC caused the TF of Cu and Pb increased by 101.06% and 25.16% compared with the control group, respectively. These results offer a fundamental scientific framework for utilizing fast-growing trees in conjunction with efficient amendments for phytoremediation of heavy metal-contaminated soil.

Key words: biochar, micro-nano scale, heavy metals, Salix, accumulation, transfer

摘要：

土壤重金属污染对生态环境和人类健康造成严重威胁，生物炭作为优秀土壤改良剂，与植物联合发挥作用，是修复受重金属污染的土壤的潜力途径。以动物源生物质骨粉为原料，采用高温裂解联合湿法球磨技术，制备了两种不同粒径（<75 μm和<1.0 μm）的富磷生物炭（BC和MBC）。通过大棚盆栽试验，考察不同施用剂量（0、0.5%、1.0%和2.0%，w%）的BC和MBC对重金属污染土壤中Cu和Pb的赋存形态及其在苏柳172（Salix jiangsuensis ‘172’）的积累和转运影响。主要结果如下：1）通过对两种粒径的富磷生物炭进行SEM-EDS-mapping、TEM、XRD和FT-IR等分析表征，证明了富磷生物炭为含有大量的羟基磷灰石的富炭固相材料，且球磨后的MBC的比表面积和孔体积较BC可分别提升5.93倍和4.65倍;2）施用BC和MBC均能有效降低土壤Cu和Pb的生物可利用态含量，且同等剂量MBC的效果更优。在添加2% BC和MBC条件下，Cu和Pb的生物可利用态含量较对照显著降低了6.41%、17.31%和8.84%、30.31%（P<0.05）;3）添加BC和MBC均显著增加了苏柳172生物量（P<0.05），显著降低了苏柳172根部中Cu和Pb的含量（P<0.05），但对苏柳172积累Cu和Pb无显著影响（P>0.05）;4）BC（0－2.0%）对苏柳172的Cu和Pb生物富集和转运能力无显著影响（P>0.05），而MBC（1.0%－2%）显著提升苏柳172对Cu和Pb的生物富集和转运能力（P<0.05），2.0%MBC可使Cu和Pb的TF值分别提升101.06%和25.16%。该文对了解微纳富磷生物炭联合树木修复Cu、Pb复合污染土壤具有重要意义，可为重金属污染土壤的生态修复提供科学依据。

关键词: 生物炭, 微纳米, 重金属, 柳树, 积累, 转运