Abstract:

Phytoremediation technology is effective, environmentally friendly, and inexpensive for soil remediation of heavy metals (HMs) pollution. However, phytoremediation-derived waste biomass (PB) contains abundant heavy metal (Hms) that may cause secondary contamination without suitable treatment. In previous studies, we developed a hydrothermal system of PB and bone meal (BM) supported by co-hydrothermal technology (Co-HTC), which achieved the efficient fixation of heavy metals in the solid phase. Nevertheless, the composition and potential value of liquid-phase (PB/BM-L) products have not been thoroughly analyzed. Inductively coupled plasma emission spectrometer (ICP-OES), gas chromatography-mass spectrometry (GC×MS), continuous flow injection analyzer (FIA), Kjeldt nitrogen analyzer (KNA) and organic carbon/total nitrogen analyzer (TOC) were used to evaluate the safety of PB/BM-L, respectively. It was used in willow pot experiments to evaluate its effect on alkaline soil and plant growth, and to comprehensively evaluate its potential application value. The results show that the concentrations of Cd and Zn in PB/BM-L were lower than the national comprehensive sewage discharge standard (GB 8978—1996), (Cd≤0.1 mg∙L⁻¹, Zn≤2 mg∙L⁻¹), which is rich in nutrients such as total nitrogen (TN, 12.87 to 17.78g∙L⁻¹), total phosphorus (TP, 13.13 to 20.03 g∙L⁻¹), and total organic carbon (TOC, 8.97 to 13.46 g∙L⁻¹). The pH is in the acidic range (4.53 to 4.72), and contains a variety of mineral elements such as Ca (26.61 to 42.85 g∙L⁻¹), Mg (5.28 to 9.33 g∙L⁻¹), Fe (5.28 to 9.33 g∙L⁻¹), etc. In addition, the relative contents of PB/BM-L organic components in the liquid-phase products were analyzed. This was followed by phenol (52.81%), ketones (12.21%), pyrazine (10.09%), esters (8.64%), aldehydes (5.55%), hydrocarbons (3.62%), acids (3.11%), amines (2.81%), alcohols (0.63%) and pyridine (0.53%). The L-3% treatment in the pot experiment significantly increased willow biomass (roots, 22.50%; stems, 26.17%; leaves, 37.08%), increased plant height by 22.64%, stem diameter by 19.23%, and decreased soil pH (7.96 to 7.84). The soil physical properties were improved, the soil water content and porosity were increased by 2.01% and 0.99% respectively, while the soil bulk density was decreased by 0.17 g∙cm⁻³. Soil total nitrogen (TN), hydrolyzed nitrogen (HN), total organic carbon (TOC), available phosphorus (AP), and available potassium (AK) increased, whereas soil alkaline phosphatase (ALP), sucrase (Suc), and urease (Ure) activities increased by 81.17%, 293.04%, and 89.57%, respectively. In summary, PB/BM-L has great application prospects in improving the quality of alkaline and barren land and is expected to realize the secondary utilization of waste.

Key words: phytoremediation-derived biomass, liquid phase products, heavy metal, safety evaluation, soil improvement

摘要： 前期研究以共水热炭化技术为支撑，建立植物修复衍生生物质/骨粉（PB/BM）水热体系有效地固定了PB中重金属于固相，但液相副产物（PB/BM-L）成分和潜在利用价值未深入剖析。该研究对PB/BM-L进行成分分析，并设置对照，1%添加量和3%添加量的处理组进行柳树盆栽试验评价其对碱性土壤及植物生长的影响，综合评估其潜在应用价值。结果表明，PB/BM-L中重金属Cd、Zn质量浓度均低于国家污水综合排放标准（GB 8978－1996，Cd≤0.1 mg∙L⁻¹，Zn≤2 mg∙L⁻¹）；其富含氮（12.87－17.78 g∙L⁻¹）、磷（13.13－20.03 g∙L⁻¹）、有机碳（8.97－13.46 g∙L⁻¹）等；pH处于酸性范围（4.53－4.72）且含有多种矿质元素，如Ca（26.61－42.85 g∙L⁻¹）、Mg（5.28－9.33 g∙L⁻¹）、Fe（5.28－9.33 g∙L⁻¹）等；液相产物PB/BM-L主要有机组分依次为酚（52.81%）、酮（12.21%）、吡嗪（10.09%）、酯（8.64%）、醛（5.55%）、烃（3.62%）、酸（3.11%）、胺（2.81%）、醇（0.63%）、吡啶（0.53%）等。与对照组相比，盆栽试验中3%添加量的处理改善了土壤物理性质，降低了土壤pH（7.96－7.84），土壤含水量和孔隙度分别提高了2.01%和0.99%，而土壤容重降低了0.17 g∙cm⁻³，提高了土壤总氮（TN）、水解氮（HN）、总有机碳（TOC）、有效磷（AP）和速效钾（AK），同时土壤碱性磷酸酶（ALP）、蔗糖酶（Suc）、脲酶（Ure）活性分别提高了81.17%、293.04%、89.57%。苏柳J172（Salix×jiangsuensis cv. ‘J172’）的根、茎和叶生物量分别提高了（22.50%、26.17%、37.08%，p<0.05），且株高、茎粗分别增加了22.64%、19.23%。综上所述，PB/BM-L在碱性、贫瘠的土地上和植物生长改善方面具有良好的应用前景，有望实现废弃物的二次利用。

关键词: 植物修复衍生生物质, 液相产物, 重金属, 安全性评价, 土壤改良