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石油烃 (PHC)是目前环境中广泛存在的有机污染物,是多种烃类 (正烷烃、支链烷烃、环烷烃、芳烃)和少量其他有机物的混合物[1-2]。PHC进入土壤后,不仅会破坏土壤结构,影响其通气性,而且石油烃进入食物链后会对人体产生不可逆性的致癌、致畸、致突变的三致作用[2]。因此,如何经济、快速、有效地去除土壤中的石油污染物成为研究的重点[3]。微生物修复技术因成本低、环境友好等优势成为目前处理处置PHC污染土壤的热点方法[4-5]。
PHC微生物修复技术是以PHC作为底物,利用微生物活动过程中发生的一系列生化反应所进行的代谢降解[6-7]。微生物修复技术在降解有害物质过程中不会破坏动植物生长的土壤环境,并且可以有效地去除土壤中的有机污染物[8]。该技术根据反应过程中是否需氧气可分为好氧修复和缺氧修复[9]。由于缺氧条件下 PHC降解速率比好氧条件下的低 (1-2个数量级),目前利用微生物降解PHC的现场和室内研究多集中在好氧条件下[10-11]。在好氧条件下土著微生物利用氧气作为电子受体降解环境中的污染物,能够在较短的时间内达到较高的去除效率 [12]。
然而由于地下储油罐或输油管线的渗泄漏、土壤表层污染物的向下迁移等,存在着大量被PHC污染的深层土壤[12]。土壤中氧气浓度会随土壤深度的增加而降低,即使深层土壤中存在一定量的氧气也会很快被微生物好氧呼吸消耗殆尽。因此PHC污染的深层土壤往往处于缺氧条件[13]。与好氧微生物降解不同,缺氧微生物降解过程中不需要补充氧气/空气,且能够适应复杂的环境条件,并且修复成本相对较低[14]。因此,PHC的缺氧微生物降解具有明显优势。尽管如此,目前PHC缺氧微生物降解规律尚不清楚。本研究以PHC污染的深层土壤为对象,探索不同种类和质量分数的电子受体对土壤中土著微生物丰度、群落结构以及PHC缺氧降解的影响规律。研究结果可为深层PHC污染土壤修复技术的研发提供技术支持。
电子受体对深层土壤中石油烃缺氧降解的影响
Effect of electron acceptor on anoxic biodegradation of petroleum hydrocarbons in subsurface soil
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摘要: 微生物降解是处理土壤中石油烃 (PHC)污染的有效技术,目前对PHC微生物降解的研究多集中在好氧条件下,对PHC缺氧微生物降解的研究较少,PHC缺氧降解规律尚不清楚。以PHC污染的深层土壤为对象,探究不同质量分数 (500、1 500、5 000 mg·kg−1)的硫酸盐、硝酸盐或混合电子受体对土壤中土著微生物丰度、群落结构以及PHC缺氧降解的影响规律。结果表明,150 d缺氧培养后,添加相同种类电子受体的土壤处理中细菌丰度、潜在PHC降解菌 (变形菌门和厚壁菌门)丰度随电子受体的质量分数增加而增加;添加相同质量分数的不同种类电子受体土壤处理中细菌丰度、潜在PHC降解菌丰度从高到低分别为硝酸盐、混合电子受体、硫酸盐。添加相同种类电子受体的土壤处理中ΣPHC (C10~C30)和C1 (C10~C16)、C2 (C17~C23)、C3 (C24~C30)组分的降解率随着加入电子受体质量分数增加而增加;相同质量分数的不同种类电子受体土壤处理中ΣPHC和C1、C2、C3组分的降解率从高到低分别为硝酸盐、混合电子受体、硫酸盐。土壤中PHC缺氧降解率与细菌丰度、潜在PHC降解菌丰度均存在正相关关系。研究结果可为石油烃污染土壤的修复技术研发提供技术支持。Abstract: Anoxic biodegradation is an attractive approach to the removal of petroleum hydrocarbons (PHC)in soil. At present, the biodegradation of PHC is mostly focused on aerobic conditions. There are fewer studies on anoxic biodegradation of PHC, and the law of anoxic biodegradation of PHC is still unclear. In this study, the effect of electron acceptor (nitrate, sulfate and mixed electron acceptor)at different mass fraction (500, 1 500, 5 000 mg·kg−1)on anoxic biodegradation of PHC in subsurface soil were investigated. Dynamic changes in the soil bacterial abundance and community composition were also examined. The results showed that after 150 d of anoxic incubation, the abundance of bacteria and potential PHC-degrading bacteria (Firmicutes and Proteobacteria)in the soil treated with the same types of electron acceptors increased with the increase of electron acceptor concentration; the abundance of bacteria and potential PHC-degrading bacteria in the soil treated with the same concentration of different types of electron acceptors, in descending order, were nitrate, mixed electron acceptor, and sulfate, respectively. The biodegradation rates of ΣPHC (C10~C30)and C1 (C10~C16), C2 (C17~C23), and C3 (C24~C30)fractions in soil treated with the same types of electron acceptor added increased with the increase in the concentration of electron acceptor added; the biodegradation rates of ΣPHC and C1, C2, and C3 fractions in soil treated with the different types of electron acceptor added at the same mass fraction, in descending order, were nitrate, mixed electron acceptors, and sulfate, respectively. There was a positive correlation between the anoxic biodegradation rate of PHC in soil and the abundance of bacteria and potential PHC-degrading bacteria. The results can provide technical support for the development of remediation technologies for petroleum hydrocarbon contaminated soils.
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Key words:
- electron acceptor /
- petroleum hydrocarbon /
- anoxic biodegradation /
- microorganism
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表 1 土壤中PHC质量分数
Table 1. Mass fraction of PHC in soil
组名 碳原子数 原土PHC质量分数/
(mg·kg−1)各PHC组分占原土中PHC
质量分数的比例/%灭菌土PHC质量分数/
(mg·kg−1)各PHC组分占灭菌土中PHC
质量分数的比例/%C1 C10~C16 184.68±5.21 20.72 119.37±1.52 19.86 C2 C17~C23 626.99±14.69 70.36 416.02±6.55 69.21 C3 C24~C30 79.51±2.53 8.92 65.73±2.84 10.93 C4 C31~C40 14.53±2.08 — 13.25±1.97 — ΣPHC C10~C30 891.18±23.86 — 601.12±13.25 — -
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