锰氧化菌Aminobacter sp.H1的分离鉴定及其锰氧化机制研究

从某水厂的生物除锰滤池中分离出1株新的高效锰氧化菌,命名为H1.通过生理生化及16S rDNA序列对比分析鉴定为氨基杆菌(Aminobacter sp.),国内外未曾有对该菌株具有锰氧化能力的相关报道.本文对Aminobacter sp.H1的微生物特性、锰氧化机制及生成的生物氧化锰的性质进行了研究.结果表明,Aminobacter sp.H1的锰耐受浓度高达50 mmol·L-1,可完全去除浓度低于10 mmol·L-1的Mn(Ⅱ).菌株H1对Mn(Ⅱ)的氧化主要是通过产生锰氧化活性因子和碱性代谢产物提高pH两个因素共同作用的结果,活性因子细胞内合成后分泌到细胞外起作用.氧化过程中发现有Mn(Ⅲ)中间体出现,XRD、XPS、SEM-EDX等分析菌株H1介导生成的生物氧化锰发现,生物氧化锰与菌体结合紧密,弱结晶、无固定形态,成分主要为MnCO3、MnOOH、Mn3O4和MnO2等.     

锰氧化菌Arthrobacter sp.HW-16的锰氧化特性和氧化机制

锰作为一种常见的无机污染物,难以从环境中除去.本研究采用选择性培养基从锰矿土壤中分离到1株高效锰氧化细菌Arthrobacter sp.HW-16.此外,高通量测序发现,不同驯化条件下微生物群落结构有明显差异,且Arthrobacter在含Mn(Ⅱ)培养基里为优势菌属.本文对Arthrobacter sp.HW-16的微生物特性和锰氧化机制进行了初步的研究.结果表明,菌株HW-16的Mn(Ⅱ)耐受质量浓度高达5 000 mg·L~(-1),菌株HW-16在3 000 mg·L~(-1)Mn(Ⅱ)培养基里取得最大Mn(Ⅱ)氧化率为66.28%.单因素变量实验表明环境因子影响菌株HW-16的生长和Mn(Ⅱ)氧化率.菌株HW-16在30℃,pH 7.0,1%或3%盐度,200 r·min-1下生长得最好.高温(≥40℃),高pH(≥7),高转速和低盐度条件下Mn(Ⅱ)氧化率高.菌株HW-16通过合成锰氧化活性因子促使Mn(Ⅱ)氧化和产生碱性代谢产物促使Mn(Ⅱ)转化为沉淀.     

生物氧化锰矿物对几种重金属的吸附作用

从土壤铁锰结核及其附近土壤中分离、培养并筛选到3株锰氧化细菌:芽孢杆菌(Bacillus sp.)WH4和GY16,假单胞菌(Pseudomonas sp.)WHS26,应用这3个菌株大量合成了生物氧化锰.在此基础上,比较研究了这3个菌株催化合成的生物氧化锰与一种化学合成锰氧化物矿物(S-MnOx:Synthesized Mn oxide)对重金属Cu2+、Zn2+、Cd2+的吸附特征.结果表明,3种生物氧化锰对重金属的吸附具有明显优势,其对Cu2+、Zn2+、Cd2+的最大吸附量约为S-MnO2的10～100倍;各种氧化锰对Cu2+、Zn2+、Cd2+的吸附过程均符合Langmuir等温吸附模型,且是一个快速吸附的过程;3种锰氧化物对Cu2+、Zn2+、Cd2+3种重金属的最大吸附量与其比表面积呈正相关,吸附过程受pH影响,最适的pH范围为3～6.     

土壤中耐受Mn(Ⅱ)真菌菌株的分离及氧化Mn(Ⅱ)特性研究

采用分离纯化的方法从锰矿企业含锰土壤中筛选分离能够耐受并氧化二价锰离子(Mn(Ⅱ))的真菌,并研究分离菌株的生长特性及对Mn(Ⅱ)的氧化能力。共分离得到4株具有耐受Mn(Ⅱ)的真菌菌株,分别为XS2-1,XS2-2,XS3-2-4,XS3-2-5。其中XS2-2,XS3-2-4,XS3-2-5能够将Mn(Ⅱ)氧化生成锰氧化物(Mn(Ⅲ,Ⅳ))。根据ITS(Internal Transcribed Spacer)rRNA基因测序结果,这4株真菌菌株分别属于Cladosporium、Plectosphaerella、Epicuccum和Phaeosphaeriopsis属。考察了pH值以及Mn(Ⅱ)浓度对菌株生长和氧化Mn(Ⅱ)能力的影响。发现这4株真菌菌株的生长受pH值影响较小,但受Mn(Ⅱ)浓度影响较大;菌株的Mn(Ⅱ)氧化能力受pH值和Mn(Ⅱ)浓度的影响均较为显著。菌株XS3-2-5的Mn(Ⅱ)氧化能力最为突出,随着Mn(Ⅱ)浓度的增加(最高至15 000μmol/L),其Mn(Ⅱ)氧化能力不断升高,并未出现不耐受的情况。能够氧化Mn(Ⅱ)的真菌菌种的发现对于治理受锰污染的水及土壤具有潜在的实际意义。     

真菌菌株XS3-2-5对含锰废水中Mn(Ⅱ)的生物氧化作用

该研究以一株从锰污染土壤中筛选、分离得到的具有高Mn(Ⅱ)耐受性并具有氧化Mn(Ⅱ)的特性的真菌菌株XS3-2-5为对象,考察了p H值和Mn(Ⅱ)初始浓度对该菌株生长及其氧化Mn(Ⅱ)能力的影响,并结合扫描电镜(SEM)、透射电镜(TEM)、X射线能量色散谱(EDS)、X射线光电子能谱(XPS)等方法,对经过菌株XS3-2-5氧化后的生物锰氧化物进行了表征。ITS(internal transcribed spacer)r RNA基因测序结果表明,该菌株属于Phaeosphaeriopsis sp。pH和Mn(Ⅱ)初始浓度对该菌株的生长速度无显著影响。该菌株(湿重)在p H 5~7范围内对Mn(Ⅱ)(300μmol/L)的氧化率接近200 mg/g。SEM、TEM、EDS和XPS的分析结果表明,Mn(Ⅱ)经过该菌株氧化后的生物锰氧化物主要为二氧化锰。     

环境中生物氧化锰的形成机制及其与重金属离子的相互作用

微生物参与形成的锰氧化物是环境中一种高活性的锰氧化物.研究表明,锰氧化菌主要通过分泌多铜氧化酶来氧化Mn(Ⅱ)而形成锰氧化物.微生物形成锰氧化物过程的主要初级产物是与δ-MnO₂或与酸性钠水锰矿类似的层状锰酸盐.生物氧化锰是环境中重要的吸附剂、氧化剂和催化剂.通过吸附、氧化作用,生物氧化锰影响着重金属离子在环境中的迁移转化,在重金属元素生物地球化学循环中起重要作用.研究锰氧化物的生物形成过程、生物氧化锰的结构特征及其与重金属离子之间的相互作用,对于了解生物氧化锰在重金属元素生物地球化学循环过程中的作用以及在重金属污染修复中的应用有着重要意义.本文综述了环境中生物氧化锰的形成机制、性质、结构特点及其吸附、氧化重金属离子的机制.     

不同氧化锰矿物与砷的交互作用

利用从土壤铁锰结核中分离筛选得到的1株锰氧化细菌(芽孢杆菌,Bacillus sp.)GY16合成生物氧化锰,与化学合成的水钠锰矿进行比较,研究了不同氧化锰对As的氧化吸附特征.结果表明,生物氧化锰和化学氧化锰对As(Ⅲ)均有强烈的氧化作用,化学氧化锰对As(Ⅲ)的氧化速率要高于生物氧化锰,而单位物质的量的生物氧化锰对As(Ⅲ)的氧化量可达化学氧化锰的5倍,并且对As(Ⅴ)有非常明显的吸附作用,而化学氧化锰对As(Ⅴ)的吸附量则非常少.此外,随着生物氧化锰与As(Ⅲ)/As(Ⅴ)反应的进行,生物氧化锰对As(Ⅲ)/As(Ⅴ)的氧化吸附速率均逐渐降低.随着pH的增加,生物氧化锰对As(Ⅲ)的氧化量及As(Ⅴ)的吸附量均呈现出明显的下降趋势,但是化学氧化锰对As(Ⅴ)的吸附量却有微弱的增加.研究结果可为生物氧化锰应用于环境修复提供可靠的技术支撑.     

微生物对砷的氧化还原竞争

滤池被广泛运用于饮用水厂中,前期研究发现某水厂生物滤池处理含砷地下水时,一方面三价砷可被生物氧化锰氧化为五价砷,另一方面滤池系统中存在的微生物砷还原酶可促使五价砷还原为三价砷,而滤池表面存在的这种微生物竞争关系会影响滤池的稳定性及处理效率.为探讨其内在机制,本研究选取1株锰氧化模式菌(Pseudomonas sp.QJX-1)和1株砷还原模式菌(Brevibacterium sp.LSJ-9),考察在Mn2+、As(As3+、As5+)共存时,两菌株对空间、营养物质以及对砷氧化/还原的竞争关系.结果表明,不同的反应时间,Mn、As质量浓度/价态不同,三价及五价砷体系中,Pseudomonas sp.QJX-1生成的锰氧化物在砷的氧化还原反应中占主导地位,即能迅速氧化本身存在的As3+(三价砷体系)和砷还原菌产生的As3+(五价砷体系),最终两体系中砷都主要以As5+的形式存在.PCR及RT-PCR结果表明,反应过程中锰氧化菌功能基因(cum A)抑制了砷还原酶(ars C)的表达,锰氧化菌16S rRNA表达量始终比砷还原菌高两个数量级,即锰氧化菌在生长竞争过程中占优势.实验结果表明滤池的水力停留时间是决定出水中砷价态的一个重要因素.     

Pseudomonas sp. QJX-1的锰氧化特性研究

从锰矿土壤样品中分离、纯化出1株高效锰氧化细菌(QJX-1),经16S rDNA序列鉴定为Pseudomonas sp.QJX-1.研究表明,Pseudomonas sp.QJX-1含有锰氧化的必需成分多铜氧化酶基因CumA,当初始Mn2+为5.05 mg·L-1,菌密度D600为0.020时,该菌可在48 h内将Mn2+转化,且转化率高达99.4%.在寡营养条件下该菌锰氧化速率较富营养条件下有显著提高;添加石英砂滤料促使生物膜的快速形成,进而促进Mn2+的生物转化.根据研究结果推测地下水处理过程中生物锰氧化速率较快.     

水锰矿氧化水溶性硫化物过程及其影响因素

作为表生环境中易生成且分布广泛的氧化锰矿物,水锰矿参与水溶性硫化物的氧化反应,影响其迁移、转化和归趋.本研究考察了水锰矿氧化水溶性硫化物(S~(2-))的过程与产物,探讨了初始pH、氧气对反应速率与中间产物的影响,X-射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和透射电镜(TEM)表征水锰矿与水溶性硫化物反应固相产物晶体结构、组分和微观形貌;分光光度计、高效液相色谱仪和离子色谱仪分析S~(2-)及其氧化物的浓度与变化趋势.结果表明水锰矿氧化S~(2-)产物主要为单质S,起始pH降低可加速S~(2-)的初始氧化反应,对产物组成并无显著影响;有氧环境中单质S会进一步氧化生成S_2O_3~(2-),且水锰矿表现出良好的催化作用与化学稳定性,反应约10 h,晶体结构保持稳定.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Chlorobenzenes in waterweeds from the Xijiang River （Guangdong section） of the Pearl River

The Xijiang River is the major source of water for about 4.5 millions of urban population and 28.7 millions of rural population. The water quality is very important for the health of the rural population. The concentration and distribution of chlorobenzenes (CBs) in both water and waterweeds collected from 4 stations in the Xijiang River (Gangdong section) of the Pearl River in April and November were determined. The result showed that nearly every congener of CBs was detected. The total contents of CBs (∑CBs) in the river water ranged from 111.1 to 360.0 ng/L in April and from 151.9 to 481.7 ng/L in November, respectively. The pollution level of CBs in the water in April was higher than that in November. The contents of ∑ CBs in waterweeds ranged from 13.53×102 μg/g to 38.27×102μg/g dry weight (dw). There was no significant difference between April and November in waterweeds. The distribution of CBs in roots, caulis, and leaves of Vallisneria spiralis L. showed different patterns. The leaves mainly contained low-molecular-weight CBs(DCBs), whereas the roots accumulated more PCBs and HCBs. The average lgBCFlip (bioconcentration factor) of CBs ranged from 0.64 to 3.57 in the waterweeds. The spatial distribution character of CBs in the Xijiang River was: Fengkai County ＜ Yunan County ＜Yun'an County ＜ Gaoyao County according to the ∑CBs, and the pollution deteriorated from the upstream to the downstream of the Xijiang River. Further analysis demonstrated that the discharge of waste containing CBs may be the main source of CBs pollution in the Xijiang River.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.