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题名: 基因工程菌与生物质联合强化土壤中砷挥发研究
作者: 陈 鹏1
学位类别: 硕士
答辩日期: 2017-05
授予单位: 中国科学院生态环境研究中心
授予地点: 北京
导师: 孙国新
关键词: 砷,修复,生物挥发,生物刺激,生物强化 ; Arsenic, Remediation, Biovolatilization, Biostimulation, Bioaugmentation
其他题名: Study on the synergistic effect of genetic engineering bacterium and organic matter on soil arsenic volatilization
学位专业: 环境科学
中文摘要: 在土壤环境中,过量的砷(As)不仅危害植物生长,而且能在植物中累积并通过食物链进入人体,威胁人类健康。砷的不同化学形态之间的迁移性和毒性差异较大,无机砷(As(III) 和As(V))是自然环境中是毒性最大的形态,被美国环保总署列为 A 类致癌物质。砷对人类有致突变和遗传毒性,长期接触会引起我们机体产生一系列的健康问题,如胃肠道疾病、心血管紊乱和肝、肾功能衰竭等。数以百万计的人长期暴露在砷污染的地区,然而很多国家都不能对土壤砷污染进行有效的控制和管理。 微生物能使土壤中砷的形态通过氧化、还原和甲基化等发生变化。研究报道土壤中的砷能被土壤环境中的真菌、酵母菌和细菌通过一系列的氧化还原和甲基化,最终转化为挥发性气态化合物:砷化氢(AsH3)、一甲基砷(AsH2(CH3))、二甲基砷(AsH(CH3)2)和三甲基砷(As(CH3)3)。这个过程被认为是一种解毒机制。砷的生物甲基化和挥发是原位修复中的一种潜在修复方式,并且因独具的优点已被广泛誉为具成本效益的修复策略。但土著微生物产生挥发砷的能力有限,土壤修复效率有待提高。据报道,在土壤中砷的甲基化和挥发是一个严格的微生物驱动的过程。我们可以通过生物刺激和生物强化有效提高土壤砷甲基化和挥发的速率和效率。生物刺激旨在通过改变土壤环境条件提高土壤中微生物的砷甲基化和挥发的活性;生物强化是通过接种具有对砷有较高砷甲基化和挥发效率的微生物来加强修复砷污染的土壤。 基于此,我们选择表达了砷甲基化基因(arsM)的恶臭假单胞菌KT244 (GE P. putida)为外源性细菌和秸秆(RS)或生物炭(BC)为外源性生物质联合修定三种不同砷污染程度的水稻土来探寻提高砷甲基化和挥发效率的途径。同时我们希望为实际运用生物复合修复砷污染土壤开辟途径和为缓解砷对人类健康危害提供科学依据。实验的主要结果如下: (1)在本实验条件下,三种土壤中砷的挥发速率各不相同,单独添加秸秆(5%)能显着增强土壤中砷的甲基化和挥发,增强幅度达到了几百倍,且在淹水条件下对砷挥发促进作用强于在未淹水条件下。与GE P. putida联用进一步促进了砷的甲基化和挥发,且在未淹水条件下对砷挥发的促进作用更强。 (2)在本实验条件下,生物炭对土壤中砷的甲基化和挥发没有显著作用,且生物炭与GE P. putida 联用和生物炭、秸秆与 GE P. putida三者联用对砷的甲基化和挥发的促进作用也相对较低。 (3)单独添加秸秆和秸秆与基因工程菌GE P. putida 联用的处理中,挥发砷的主要形态为三甲基砷(As(CH3)3,65.9% ~84.2%)其次为砷化氢(AsH3,14.1% ~30.7%)。接种GE P. putida后甲基砷比例略有增加但并不显著。 以上结果表明,秸秆与GE P. putida联用对土壤中砷甲基化和挥发促进作用明显,表明了生物刺激和生物强化共同促进土壤中砷的甲基化和挥发在修复砷污染土壤中是有潜在实用价值的。
英文摘要: Excessive arsenic (As) in soil is not only harmful to plant growth, but also damaging human health through the food chain. Arsenic mobility and toxicity vary greatly among different chemical species, inorganic arsenate (As(V)) and arsenite (As(III)) are the primary and also most toxic arsenic species existing in natural environment, which has been ranked first on Super Fund List of Hazardous Substances by the U.S. Environmental Protection Agency. Arsenic is known to have mutagenic and genotoxic effects on humans, and long-term exposure can cause a series of health problems such as skin pigmentation, hyperkeratosis, and cancers. Millions of people are suffering from chronic inorganic As exposure, however, control and management of As-related pollution in soil exceed many countries capabilities. Transformations of As species in soil usually involve oxidation, reduction, and methylation, all of which are commonly driven by microbes. Several studies have stated that As can be volatilized from soil environment into the atmosphere by fungi, yeast, and bacteria. This process involves conversion of the inorganic As into arsines (arsine (AsH3), monomethylarsine (AsH2(CH3)), dimethylarsine (AsH(CH3)2) and trimethylarsine (As(CH3)3) through successive reduction/methylation steps. Arsenic biomethylation and biovolatilization in situ, a detoxification pathway, has been widely hailed because of their potential advantages as the cost-effective ways. However, the amounts of volatile As generated by indigenous microorganisms are limited and its effectiveness needs to be improved. It has been reported that As methylation and volatilization in soil is a strictly biological process and driven by microbial activity. The rate and efficiency of As methylation and volatilization can be enhanced through biostimulation and/or bioaugmentation. Biostimulation aims at enhancing microbial activities to remove As through methylation and volatilization with the aid of indigenous microorganisms in the site. Bioaugmentation is to improve As remediation by inoculating microorganisms with high activities of As volatilization.Here, efficiencies of As volatilization were evaluated in three different paddy soils amended with rice straw (RS, 5% w/w), biochar (BC, 5% w/w),inoculation of genetically engineered strain, Pseudomonas putida KT2440 (GE P. putida). Our study would provide useful information for practical bioremediation of As contaminated soil, and mitigate the health risks of As accumulated in food crops. The major results of the study are as follows: (1) In this experiment condition, the flux of As volatilization in different soils are quite different. The addition of RS (5% w/w) significantly enhanced As volatilization from the paddy soils. Hundred times of As volatilization were improved with the amendment of rice straw in comparison to the corresponding non-amended soil (control). And the As flux under the flooded condition was much higher than that in the nonflooded condition. The combination of RS + GE P. putida further enhanced the As flux in different soils. And the As flux under the nonflooded condition was a bit higher than that in the flooded condition. (2) The amendment of biochar (5% w/w) alone also showed some positive effect on As volatilization although not significant. The treatment of BC + GE P. putida and BC + RS + GE P. putida increased As methylation and volatilization respectively, but less than that of RS + GE P. putida. (3) The application of rice straw (Soil + RS and Soil + RS + GE P. putida) resulted in high rates of As volatilization. These samples were analyzed for As speciation. Trimethylarsine was proved to be dominant As species (65.9% ~84.2%), followed by AsH3 (14.1% ~30.7%). Inoculated GE P. putida alone slightly (but not significantly) increased the percentage of methylarsines. In summary, based on our data, the result was useful to evaluate arsenic methylation and emission from the investigated paddy soil amended the RS and inoculated the GE P. putida. It is proposed that combining genetically engineered bacteria with rice straw could be a promising strategy for bioremediation processes of arsenic-contaminated environments and reducingarsenic contamination in food.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38605
Appears in Collections:中澳联合土壤环境研究室_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
陈 鹏. 基因工程菌与生物质联合强化土壤中砷挥发研究[D]. 北京. 中国科学院生态环境研究中心. 2017.
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