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化学氧化修复是有机污染场地常见的修复技术之一[1],其修复机理主要是通过强氧化剂与有机污染物发生氧化还原反应,使得污染物转化为稳定、低毒或无毒性物质[2]。常见的化学氧化剂有活化过硫酸盐、Fenton、类Fenton、高锰酸钾、臭氧等,其中活化过硫酸盐以其易活化、适应性广、效果好等优点而成为研究热点[3-4]。化学氧化能快速而高效地去除土壤中的各类有机污染物,具有修复效率高、修复速率快、普适性强等优点[5]。然而,加入大量化学氧化剂往往会导致土壤理化性质改变、微生物生态系统破坏、带来二次污染等隐患[6]。
微生物修复技术通过微生物的生长代谢作用,将有机污染物转化成简单无机物,从而达到去除环境中有机污染物的目的[7],包括生物刺激(添加营养物质)、生物强化(添加高效降解菌或生物催化剂(基因和酶))和曝气系统(曝气增氧)等[8]。与化学氧化等其他技术相比,微生物修复技术能够有效避免二次污染问题,其成本更低,更易于维护,但也存在修复时间长、对环境要求比较严格等缺点[9],故在实际污染场地的应用中,仍具有一定的局限性。
为了解决单项修复技术的局限性,实现更高的有机污染物去除率的目标,可以使用多种方法联合修复[10]。近年来的研究表明,化学氧化和微生物联合修复是一种可行的联合修复方法,具有广泛的应用前景[11-12]。然而,在此前化学氧化-微生物联用技术的研究中,微生物降解主要依赖土著微生物,重点关注的是化学氧化剂对土壤微生物生态系统的影响,关于化学预氧化联合微生物强化或微生物刺激技术(即预氧化后强化微生物降解作用)的研究较少[13-14]。
菲作为土壤中常见的多环芳烃污染物之一,对人类健康具有严重威胁[15]。针对菲污染土壤修复的研究主要集中于化学氧化、微生物降解等单一方法[16],本研究将化学氧化和微生物修复技术相结合,旨在探究化学预氧化后强化微生物降解对土壤中菲的降解效应,重点关注低浓度过硫酸盐预氧化耦合生物强化和生物刺激技术对菲降解的促进效应,以及修复期间土壤各项理化性质的变化情况,为化学氧化-微生物联用修复技术的应用提供参考。
化学预氧化-生物强化-生物刺激对土壤中菲降解的联合效应
Joint degradation effects of phenanthrene in soil by chemical pre-oxidation-bioaugmentation-biostimulation
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摘要: 通过室内实验,探究了低浓度过硫酸盐预氧化耦合生物强化或生物刺激技术处理下土壤中菲的降解率和修复效应。结果表明,浓度为0.1 mmol·g−1、温度为50 ℃热活化的过硫酸钠对土壤中菲7 d的降解率为22.7%。预氧化后,加入高效降解菌和营养物质,强化微生物对菲的降解,继续培育21 d,最终降解率较第7天可提高8.08%~18.59%。同时添加高效降解菌和营养物质N,对土壤中菲的降解促进作用最强,最终降解率可达41.29%,较仅进行化学氧化的对照组和仅进行微生物降解的对照组分别提高17.44%和22.86%,较预氧化后不进行微生物强化的对照组提高12.9%。降解期间,土壤微生物数量和pH呈先下降,后上升趋势,最终维持在相对稳定水平。相关性分析结果表明,土壤中菲的降解率与氧化剂和营养物质N的添加呈显著正相关,土壤微生物数量与pH呈正相关,与氧化剂呈负相关,土壤pH与氧化剂及营养物质P呈负相关。研究结果证实了化学预氧化耦合生物强化和生物刺激技术能有效促进微生物对菲污染土壤的修复。Abstract: The present study was conducted to investigate the degradation of phenanthrene in soil by low-concentration persulfate pre-oxidation combined bioaugmentation and biostimulation using high-efficiency degrading bacteria and different types of nutrients. The results showed that degradation efficiency of phenanthrene was 22.7% after 7 days treatment with 0.1 mmol·g−1 persulfate concentration and thermal activation at 50 ℃. Then the phenanthrene degradation bacteria and nutrients were added into the pre-oxidized matrix, and performed 21 days continuous cultivation, the final degradation efficiency of phenanthrene increased by 8.08%~18.59%. The simultaneous addition of degradation bacteria and nutrient N was the most effective way to promote the degradation of phenanthrene in soil, and the final degradation efficiency could reach 41.29%. This was 17.44% higher than that of the chemical oxidation control group, 22.86% higher than that of the microbial degradation control group and 12.9% higher than that of pre-oxidation without biofortification control group. During the degradation process, soil microbial biomass and pH decreased at first, then increased, and finally maintained at a relatively stable level. The results of correlation analysis showed that degradation efficiency of phenanthrene in soil was significantly positively correlated with the addition of oxidant and nutrient N, soil microbial biomass was positively correlated with pH, negatively correlated with the addition of oxidant. Soil pH was negatively correlated with the addition of oxidant and nutrient P. These results confirmed that chemical pre-oxidation combined with bioaugmentation and biostimulation can effectively promote the bioremediation of phenanthrene-contaminated soil.
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Key words:
- chemical oxidation /
- biodegradation /
- bioaugmentation /
- biostimulation /
- phenanthrene
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表 1 实验处理组
Table 1. Experimental treatment groups
实验处理组 处理组简称 添加药剂 单独微生物降解对照 B-CK 化学氧化阶段:不进行化学氧化,仅加入等量去离子水
微生物降解阶段:等量去离子水单独化学氧化对照 C-CK 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.1 mL·g−1 0.2 mol·L−1 NaN3化学氧化-土著微生物降解对照 CK 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:等量去离子水化学氧化+营养物质N刺激 C+N 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.187 mol·g−1 NaNO3化学氧化+营养物质P刺激 C+P 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.018 7 mol·g−1 KH2PO4化学氧化+营养物质NP刺激 C+NP 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.187 mol·g−1 NaNO3;0.018 7 mol·g−1 KH2PO4化学氧化+生物强化 CBA 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.1 mL·g−1 菌液化学氧化+生物强化+营养物质N刺激 CBA+N 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.1 mL·g−1 菌液;0.187 mol·g−1 NaNO3化学氧化+生物强化+营养物质P刺激 CBA+P 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.1 mL·g−1 菌液;0.018 7 mol·g−1 KH2PO4化学氧化+生物强化+营养物质NP刺激 CBA+NP 化学氧化阶段:0.1 mmol·g−1 Na2S2O8
微生物降解阶段:0.1 mL·g−1 菌液;0.187 mol·g−1 NaNO3;0.018 7 mol·g−1 KH2PO4 -
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