油菜-紫花苜蓿混种对土壤中菲、芘的修复作用

 【目的】探讨混种模式下植物对土壤中多环芳烃（PAHs）污染的联合修复、积累效应。【方法】采用盆栽试验法，对比研究油菜、紫花苜蓿在不同栽培模式下对土壤中芘、菲的去除效果与修复机制。【结果】在试验浓度范围内，混种模式下芘、菲的修复效果明显超过单种模式。油菜、紫花苜蓿联合种植70 d后，土壤中菲、芘平均去除率为75.06%、68.22%，分别比二者单独种植时高出43.26%、40.38%和11.03%、16.29%，强化效果明显。植物本身能够吸收与累积在一定量的菲和芘，累积量与土壤中菲、芘的添加浓度正相关。相同污染水平下，茎叶部积累量低于根部、菲小于芘、混种模式低于单种模式。在植物-微生物系统中，微生物降解、植物-微生物联合效应是菲、芘去除的主要途径，但植物-微生物联合效应是混种模式下强化修复PAHs污染的主要原因。【结论】混种模式能强化PAHs污染土壤的修复效果、减少植物积累、缓解污染风险。

Mechanisms of the Removal and Remediation of Phenanthrene and Pyrene in Soil with Mixed Cropping of Alfalfa and Rape

【Objective】 To evaluate the potential of multispecies rhizoremediation in decontaminating polycyclic aromatic hydrocarbons (PAHs) contaminated soil and its impacts on plant accumulations of PAHs. 【Method】 Pot experiments were conducted to investigate the mechanisms of the removal and remediation efficiencies of PAHs under different planting models using two plant species, alfalfa (Medicago sativa L.) and rape (Brassica campestris L.) in a greenhouse. 【Result】 Results showed that multispecies rhizoremediation rather than monoculture have the evident potential to enhance pollutants removal in soils with initial phenanthrene concentrations of 20.05-322.06 mg?kg-1 and pyrene of 20.24-321.42 mg?kg-1. At the end of the 70 d experiment, the extractable PAHs in soils with mixed cropping of alfalfa and rape were lower than that in monoculture. About 65.17%-83.52% of phenanthrene and 60.09%-75.34% of pyrene were removed from the soils in mixed cropping, respectively. As compared to monoculture with rape, mixed cropping removed in 43.26% of phenanthrene and 40.38% of pyrene from soils in average and relative to monoculture with alfalfa, 11.03% of phenanthrene and 16.29% of pyrene was removed. Alfalfa or rape did take up PAHs from the soils obviously; the concentrations of PAHs in root or shoot monotonically increased while ones in the soils were higher, and under the same treatment conditions, the concentrations of PAHs in root or shoot were lower in mixed cropping than that in monoculture, and in the shoot lower than in the root. Despite the presence of vegetation evidently enhanced the remediation of PAHs in soil environment, contributions of abiotic loss, plant accumulation and degradation was much lower than ones of microbial degradation and plant-microbial interactions in the process of phytoremediation. Thus plant-microbial interactions are the main mechanisms for the remediation enhancement of soil PAHs pollution under mixed cropping models. 【Conclusion】 Results from this study suggested a feasibility of the establishment of multispecies phytoremediation to improve the efficiency of bioaugmentation in decontaminating PAHs contaminated soils, decreasing crop accumulations to PAHs and reducing risks associated with PAHs.