Abstract:

There are large areas in the Northern cold region that consist of contaminated soils with low and medium concentrations of polycyclic aromatic hydrocarbons (PAHs). These contaminants pose potential threats to both ecological safety and human health. In this paper, a mixed biochar (C500+W500) was used as a carrier, and Pseudomonas sp. S4 and Mortierella alpine J7 were used as mixed bacteria capable of degrading PAHs. The bioremediation materials were prepared using an adsorption immobilization method. The study aimed to investigate the degradation capabilities of mixed biochar and single-type biochar loaded with cold-tolerant mixed bacteria on soil compounds such as phenanthrene (Phe) and pyrene (Pyr) under low-temperature conditions, and the mechanisms and advantages of biochar in the process of microbial degradation of PAHs in soil were discussed. The results showed that the remediation effects of mixed biochar immobilized microorganisms on Phe and Pyr in soil were higher than those of free bacteria as well as single biochar immobilized bacteria. The remediation effect was related to the mixing ratio of biochar. After 30 days of remediation at 15 ℃, the removal rates of Phe and Pyr were 51.87% and 45.28% respectively, when using immobilized mixed biochar with 1.34% C500 and 0.67% W500 mixed biochar as the carrier (CWJ 2:1). These rates were higher than the removal rates achieved by free bacteria (25.81% and 23.65%) and single biochar immobilized group (15.63%‒18.96% and 13.62%‒16.07%). Furthermore, mixed biochar affected the migration of PAHs in soil. The addition of biochar to soil reduced the adsorption of Phe, facilitating the entry of PAHs into the bio-facies in soil and improving the microbial availability of PAHs. In terms of Phe’s competitive adsorption, the equilibrium adsorption amounts of CK biochar, CK soil, CW_soil and CW were 0.01 μg∙mg⁻¹, 25.45 μg∙g⁻¹, 23.46 μg∙g⁻¹, and 26.46 μg∙mg⁻¹, respectively. The competitive adsorption process of soil Phe by biochar was found to align closely with the quasi second-order kinetic model. This study provides a theoretical reference for in-situ microbial remediation of PAH-contaminated soil in Northern cold areas.

Key words: mixed-biochar, PAHs, immobilized microorganism, soil remediation, organic pollutants, strengthening mechanism

摘要：

北方寒冷地区存在大面积中低浓度多环芳烃（PAHs）污染土壤，潜在威胁生态安全与人群健康。以混合型生物炭（C500+W500）为载体，以耐冷假单胞菌（Pseudomonas sp.，S4）与高山被孢霉（Mortierella alpine，J7）为PAHs降解混合菌，采用吸附固定化方法制备生物修复材料，研究了低温条件下混合型/单一型生物炭加载耐冷混合菌对土壤菲（Phe）、芘（Pyr）的降解效果，并探讨生物炭对土壤中PAHs微生物降解过程的强化机理。结果表明：混合型生物炭固定化微生物对土壤Phe、Pyr的修复效果高于游离菌，亦高于单一类型生物炭固定化菌剂，并且修复效果与生物炭的混合比例有关。15 ℃条件下修复30 d后，以w=1.34% C500与w=0.67% W500混合生物炭为载体的固定化混合菌（CWJ2:1）对Phe和Pyr的去除率分别为51.87%和45.28%，高于游离菌25.81%和23.65%，亦高于单一生物炭固定化组15.63%－18.96%和13.62%－16.07%。生物炭添加后，减少了土壤对Phe的吸附量，促进土壤中PAHs进入生物相，提高土壤PAHs微生物可利用性。在Phe的竞争吸附中CK-Biochar、CK-Soil、CWsoil与CW的平衡吸附量分别为0.01 μg∙mg⁻¹、25.45 μg∙g⁻¹、23.46 μg∙g⁻¹与26.46 μg∙mg⁻¹，生物炭对土壤Phe的竞争吸附过程接近于准二级动力学模型。该研究为寒冷地区有机污染土壤的微生物原位修复提供理论指导与借鉴。

关键词: 混合型生物炭, PAHs, 固定化微生物, 土壤修复, 有机污染物, 强化机理