土壤中黑曲霉降解氧化乐果的研究

Study on the Degradation of Omethoate in Soils by Fungus Aspergillus niger

在实验室模拟条件下,选择砂壤土和粉黏土为环境介质,研究在不同氧化乐果初始浓度条件下黑曲霉(Aspergillus niger)降解土壤中氧化乐果的特性,评价黑曲霉对受污染土壤的生物修复能力,结果表明,在灭菌土壤中,黑曲霉可有效降解氧化乐果。在氧化乐果浓度较低(15mg·kg-1dried soil)的受污染非灭菌土中,投加黑曲霉的生物修复强化作用不明显,但在污染浓度较高时(150～500mg·kg-1dried soil),投加黑曲霉可明显加快氧化乐果降解速率,在氧化乐果初始浓度为500mg·kg-1dried soil条件下,非灭菌粉黏土中氧化乐果的降解半衰期由8.9d缩短到4.9d,氧化乐果生物降解速率提高10.9mg·kg-1dried soil·d-1。黑曲霉具有耐受并降解较高浓度氧化乐果能力,适合中高浓度(或污染事故)氧化乐果污染土壤的生物修复。

Currently, bioremediation of the contaminated soil is one of the hottest research fields of environmental protection. In this paper, we evaluated fungus AspergiUus niger＇s bioremediation in the polluted soil by studying the degradation of the omethoate by the fungus in sterilized and unsterilized soils at different initial concentrations of the contaminant, under laboratory simulated conditions with sidehill sand clay and paddyfield silt clay as the medium. We measured the degradation rate of the omethoate and calculated its half-life time by fitting the degradation process by the first order kinetic equation. We also measured the fraction of degraded omethoate to value the bioremediation efficiency. Our studies show that in the sterilized soil, fungus AspergiUus niger can degrade the omethoate efficiently. In the unsterilized soil, the efficiency of degradation depends on the concentrations of the contaminant. At low concentrations of omethoate（e.g. 15 mg·kg^-1 dried soil）, the bioremediation of the fungus is not obvious; At high concentrations （e.g. 150-500 mg·kg^-1 dried soil）, the added fungus accelerates the degradation of omethoate remarkably. For example, at 500 mg· kg^-1 dried soil, the half-life time of omethoate decreases to 4.9 days from 8.9 days, and the degradation rate increases to 10.9 mg·kg^-1 dried soil·d^-1. While at extremely high concentrations of omethoate （e.g. 1 000 mg·kg^-1 dried soil）, the bioremediation of the fungus is restrained badly with bioremediation efficiency 3.5%, which is lower than that of pure fungus 5.7%. Therefore, fungus AspergiUus niger can tolerate and degrade high concentrations of omethoate and it can be applicable to mass bioremediation of the soil polluted by the omethoate.