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沉积物中铁氧化物的生物还原对铁磷有效性影响的研究
Alternative TitleInfluence of bio-reduction of iron oxides on availability of iron phosphate in sediments
丁煜
Subtype硕士
Thesis Advisor李清曼
2008-09-06
Degree Grantor中国科学院水生生物研究所
Place of Conferral水生生物研究所
Keyword沉积物 铁氧化物 生物还原 铁磷 铁还原细菌 有效性
Abstract磷是生命活动必需的矿质元素,水生生物对磷敏感,过多的磷可导致水体富营养化。水柱中的磷主要源于沉积物中多种形态磷的释放,其中铁磷(与铁氧化物及水合氧化物作用的磷,简称Fe-P)对水环境变化极为敏感。铁氧化物是沉积物的重要组分,其氧化还原是缓冲沉积物物理、化学及生物学性质变化的重要因素。随着水环境污染的加剧,沉积物中铁氧化物的氧化还原及Fe-P的有效性越来越多地受到关注。 本文用于驱动铁氧化物生物还原的铁还原细菌源于武汉月湖表层沉积物,人工合成的无定形Fe(Ⅲ)氧化物为生物还原过程研究的铁氧化物。通过监测反应体系中水溶性磷、吸附态磷、Fe(Ⅲ)和Fe(Ⅱ)等变化,揭示了铁氧化物的生物还原对Fe-P有效性的影响,结果表明: (1) 最适宜铁还原细菌生长的环境为铁氧化物-水界面。随着生物量的增加,铁还原细菌同时向铁氧化物和水柱两个方向扩增。本文分离出的铁还原细菌属嫌气菌,供氧可抑制其活性。 (2) 铁还原细菌能有效地促进铁氧化物的生物还原。随着培养时间的增加,Fe(Ⅱ)的生成量逐渐增加,一段时间后达到最大值。铁氧化物的生物还原程度与培养液中的碳源性质有关。乙酸为碳源时,Fe(Ⅱ)生成量低。水生植物残体为碳源时,铁还原细菌的活性强,Fe(Ⅱ)的生成量高。 (3) 铁氧化物的生物还原可降低Fe-P的有效性。添加到Fe(Ⅲ)氧化物悬液中的磷酸根主要以三种形态存在,即专性吸附、电性吸附和水溶态。随着Fe(Ⅲ)氧化物的还原,磷的形态与数量发生变化。专性吸附磷的量增加,电性吸附磷和水溶性磷的量则下降。当Fe(Ⅲ)还原到一定程度时,后两者的量极低,几乎不能被常规检测。 (4) 无定形铁氧化物对磷的吸附可用数学模型来描述。基于几点假设,提出了无定形铁氧化物对磷的吸附模型,即TPad = (KFe(II) - KFe(III)) * MFe(II) + KFe(III) * M,式中的TPad表示吸附磷总量,KFe(II)和KFe(III)分别表示单位Fe(Ⅱ) 氧化物和Fe(Ⅲ) 氧化物的磷吸附量,MFe(II)表示Fe(Ⅱ)的量,M表示体系中总铁。获得的数值显示,KFe(II)约为KFe(III)的两倍,表明Fe(Ⅱ) 氧化物对磷的吸附能力较Fe(Ⅲ) 氧化物强。 (5) 根据数学模型获得的参数,铁氧化物生物还原过程中铁与磷相互作用的机理被描述。体系的P/Fe(III)在一定程度上决定磷的吸附量,随着P/Fe(III)的增加,Fe(Ⅲ) 氧化物吸附的磷量也相应地增加。机理可能与增加的铁氧化物表面积有关。随着Fe(Ⅱ)生成量的增加,有效磷(操作定义为电性吸附的磷和水溶性磷)优先被Fe(Ⅱ) 氧化物吸附,Fe(Ⅲ) 氧化物专性吸附的磷则向Fe(Ⅱ) 氧化物专性吸附的磷转化,直至磷在两个固相中的分布达到平衡。
Other AbstractPhosphorus is an essential mineral element for life activities in aquatic ecosystems. Due to extreme sensitiveness of hydrobiology, excess loading of phosphorus would render water bodies eutrophicated. There are various phosphorus species in sediments that can contribute to water column, but iron phosphate fraction is regarded predominant because of high instability in sediment environment. Iron oxides, one of main sediment components, play an important role in buffering the change of sediments in physico-chemistry and biology properties through oxidation-reduction reaction. Therefore, with water environment deteriorated, the attention is increasingly focused on the oxidation-reduction of iron oxides associated to the availability of iron phosphate fraction in sediments. In the thesis, a high pure strain of Fe (III) reducing bacteria was prepared with the sediment sampled from Yuehu Lake of Wuhan, and amorphous Fe (III) oxide was synthesized to gain a model of ferric oxides for bio-reduction of ferric oxides. Simultaneously, some criteria of reaction system such as soluble phosphate, sorbed phosphate, Fe (II) and Fe (III) were monitored with the purpose to characterize the relationship between availability of iron phosphate fraction and bio-reduction of ferric oxides. The results were as following: (1) A optimal habitat for ferric reducing bacteria was the iron oxide-water interface. With biomass increasing, the augment of ferric reducing bacteria was toward the directions of both iron oxide and water column. The ferric reducing bacteria obtained in the thesis seemed anaerobic, and oxygenation might impede their activities. (2) Ferric reducing bacteria can effectively promote reduction of ferric oxides. The production of Fe (II) was increased over incubation time with a maximum reached. The extent of ferric oxide bio-reduction depended on incubation medium. Compared with the residue of aquatic plants, acetate induced ferric reducing bacteria to reduce less of Fe (III) due to a weak activity. (3) Iron phosphate availability decreased was coupled with bio-reduction of ferric iron oxides. Phosphate existed in the suspension of Fe (III) oxides in three types, e. g. both specific and electrostatic adsorption phosphate as well soluble phosphate. As Fe (III) reduced, phosphate species would be changed with specific adsorption phosphate increasing but both electrostatic sorption and soluble phosphate decreasing. Provided that a certain amount of Fe (II) was produced, the latter were decreased to a level not be detected. (4) Sorption of amorphous ferric oxide to phosphate could be characterized by mathematical model. On the basis of several hypotheses, a model of iron sorption to phosphate was given, e. g. TPad = (KFe(II) - KFe(III)) * MFe(II) + KFe(III) M, which TPad denoted the total of phosphate sorbed, KFe(II) and KFe(III) denoted the amount of phosphate sorbed by unit Fe(III) and Fe (II) respectively, MFe(II) denoted the amount of Fe (II), and M represented the total of iron in the system of interest. KFe(II) obtained was two times as much as KFe(III), showing a stronger ability of Fe(II) to sorb phosphate than Fe (III). (5) The mechanism by which iron oxides sorbs phosphate was inferred based on the parameter values. Ratio of phosphate sorbed to Fe (III) (P/Fe (III)) was responsible for the amount of phosphate sorption with more phosphate sorbed as P/ Fe (III) was higher. Interpretation to the results might be related to the increase of iron oxide surface induced by addition of phosphate. With the production of Fe(II), Fe (II) preferred to sorb the available phosphate, which was operationally defined as both electrostatic sorption and soluble phosphate, and transformation of the phosphate adsorbed specifically by Fe (III) to adsorbed specifically by Fe (II) was enhanced until distribution equilibrium of phosphate in both Fe (II) and Fe (III) states reached.
Pages67
Language中文
Document Type学位论文
Identifierhttp://ir.ihb.ac.cn/handle/342005/12364
Collection学位论文
Recommended Citation
GB/T 7714
丁煜. 沉积物中铁氧化物的生物还原对铁磷有效性影响的研究[D]. 水生生物研究所. 中国科学院水生生物研究所,2008.
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