铜绿微囊藻与蛋白核小球藻的快速定性研究

铜绿微囊藻和蛋白核小球藻是藻类水华常见的优势藻,二者形状大小较为相似,不易区分,采用浮游植物流式细胞仪,初步研究了铜绿微囊藻和蛋白核小球藻的快速检测和区分技术。通过对比选择具有区分优势的参数指标,即代表细胞内颗粒复杂程度的侧向散射信号(SWS)的均值指标和代表叶绿素含量的红色荧光信号(FL Red)的均值指标,对两藻种进行了多维度的筛选和区分。根据选择的参数指标,导出对应的特征信号图谱,进一步考察其信号图谱的特征性。经研究表明区分藻种的一级指标是信号强度,二级指标是信号光滑度。     

基于高光谱特征提取的藻类叶绿素a反演模型

选取自然界中分布较广泛的小球藻和铜绿微囊藻为研究对象,进行室内藻类光谱试验,同步测定其ρ(叶绿素a),并分别建立基于混合高斯函数的小球藻和铜绿微囊藻高光谱信息模型.在此基础上,利用模拟退火算法实现模型的非线性参数拟合,提取这2种藻的高光谱特征,通过非线性回归分析,反演得到分解后的高光谱信息模型的峰高(hf)与ρ(叶绿素a)的定量模型,实现对水体中小球藻和铜绿微囊藻ρ(叶绿素a)的预测.结果表明:藻类高光谱特征提取算法能有效揭示小球藻和铜绿微囊藻的光谱本质特征,并得出相应的小球藻和铜绿微囊藻叶绿素a反演模型.     

2-甲基乙酰乙酸乙酯对藻细胞膜和亚显微结构的影响

为揭示化感物质抑制藻类的机理, 研究了芦苇化感物质2-甲基乙酰乙酸乙酯(eathyl-2-methyl acetoacetate, EMA)对蛋白核小球藻、铜绿微囊藻和普通小球藻细胞膜磷脂脂肪酸种类、含量以及藻细胞亚显微结构的影响,采用Bligh and dye法提取藻类细胞膜磷脂脂肪酸,GC-MS测定脂肪酸种类和含量,透射电镜法观测细胞亚显微结构. 结果表明, EMA使蛋白核小球藻细胞膜不饱和脂肪酸亚麻酸、亚油酸含量都增加了14%, 而饱和脂肪酸肉豆蔻酸、棕榈酸含量则下降了12%和11%. 加入EMA后, 铜绿微囊藻细胞膜中不饱和脂肪酸C18∶1和C18∶2含量分别增加了12%和10%, 饱和脂肪酸C18∶0和C16∶0含量则下降. EMA对普通小球藻细胞膜磷脂脂肪酸含量没有显著影响. EMA使蛋白核小球藻和铜绿微囊藻细胞壁脱落, 细胞膜破裂, 细胞内含物渗出, 细胞内片层结构解体, 细胞核和线粒体结构损坏. EMA对普通小球藻细胞亚显微结构没有显著破坏.     

荷花不同部位浸出液对3种淡水藻类生长的影响

文章探讨了荷花不同部位(茎和叶)浸出液对铜绿微囊藻、蛋白核小球藻及四尾栅藻生长的影响,为利用荷花化感物质减少湖泊富营养化提供基础。结果表明荷花不同部位的浸出液对3种藻类均有抑制作用,荷花叶浸出液抑制效果好于荷花茎浸出液。荷花不同部位浸出液对藻类的半浓度效应(EC5)0各不相同,荷花叶浸出液对四尾栅藻的EC50为4.21 g/L,抑制效果最好;铜绿微囊藻及蛋白核小球藻的EC50值分别为5.35 g/L、9.92 g/L;荷花茎浸出液对铜绿微囊藻、蛋白核小球藻及四尾栅藻的EC50值分别为9.52 g/L、7.28 g/L、6.90 g/L。     

薄荷提取物对3株微藻生长特性的影响

薄荷中含有不同的化感物质,其化感作用可能抑制或促进微藻生长,达到对水华微藻或商业微藻的调控作用。该研究以铜绿微囊藻、蛋白核小球藻和栅藻为受试藻种,探究了薄荷提取物对铜绿微囊藻、蛋白核小球藻和栅藻生长特性的影响。发现薄荷提取物对铜绿微囊藻(蓝藻)的生长具有抑制作用,其抑制率最大可达97%,而对蛋白核小球藻和栅藻(均为绿藻)的生长具有一定的促进作用,最大促进率可分别达552%和176%,两株受试绿藻的干重最大增加0.60 g/L和0.62 g/L。可见,薄荷提取物对不同藻种的生长特性影响不同,通过添加薄荷提取物控制微藻生长,达到对不同藻种的调控作用。     

芦苇化感物质对藻类细胞膜选择透性的影响

以藻类渗出的K⁺、Mg²⁺、Ca²⁺浓度为表征,以ICP-MS检测为手段,研究了芦苇抑藻化感物质2-甲基乙酰乙酸乙酯(eathyl-2-methyl acetoacetate, EMA)对铜绿微囊藻、蛋白核小球藻和普通小球藻细胞膜选择透性的影响. 结果表明, 在实验条件下, 铜绿微囊藻和蛋白核小球藻细胞经煮沸完全破坏细胞膜时K⁺渗出量为1 .45、1 .59 μg·(10⁹ cell)^-1, 当EMA浓度为2 mg·L^-1时, 铜绿微囊藻和蛋白核小球藻的K⁺渗出量为1 .38、1 .40 μg·(10⁹ cell)^-1,当EMA浓度为4 mg·L^-1时, 铜绿微囊藻和蛋白核小球藻的K⁺渗出量为1 .44、1 .58 μg·(10⁹ cell)^-1,离子渗出量达到完全破坏细胞膜最大渗出量的95%以上. EMA浓度为4 mg·L^-1时,普通小球藻的细胞内K⁺渗出量为0 .64 μg·(10⁹ cell)^-1, 仅为完全破坏细胞膜后K⁺渗出量的31 .5%. EMA对Mg²⁺、Ca²⁺的渗出量的影响规律与K⁺相同. EMA破坏了铜绿微囊藻和蛋白核小球藻的细胞膜,但对普通小球藻的细胞膜透性没有显著影响.这是EMA选择性抑藻的机理之一.     

不同磷浓度对小球藻铜绿微囊藻生长及生理的影响

常通过对藻类某些生理生化指标的测定,甄别水体的营养状态。实验以小球藻(Chlorella sp.)和铜绿微囊藻(Microcystis aeruginosa)为对象,研究它们在不同磷浓度下藻细胞480 nm和665 nm吸光度的比值(OD480/665)、光系统Ⅱ的最大光化学效率(F v/Fm)、碱性磷酸酶活性(APA)等的响应及其作为营养状态指标的可能性进行了探讨。结果发现磷浓度与小球藻OD480/665负相关;而铜绿微囊藻OD480/665值与磷浓度相关性不明显。P缺乏能导致小球藻和微囊藻F v/Fm降低。小球藻产生的APA与培养基中磷含量负相关,而铜绿微囊藻产生碱性磷酸酶的量与培养基中磷含量关系并不明显。研究结果表明OD480/665、Fv/Fm、APA可以反映小球藻磷限制情况,不能反映铜绿微囊藻磷限制情况;藻类生理生化指标对磷的响应与种类有关,用来指示营养限制情况时需谨慎。     

水稻秸秆浸泡液对蓝藻和绿藻生长选择性抑制作用

运用流式细胞仪研究了水稻秸秆浸泡液(RSE)对藻类生长、形态学特征(细胞大小)和生理参数(叶绿素荧光强度)的影响.RSE对有毒、无毒铜绿微囊藻(Microcystis aeruginosa)、有毒水华鱼腥藻(Anabaena flos-aquae)、鱼害微囊藻(Microcystis ichthyoblabe)这4种蓝藻和羊角月牙藻(Selenastrum capricornutum)、蛋白核小球藻(Chlorella pyrenoidosa)、斜生栅藻(Scenedesmus obliqnus)这3种常见绿藻生长的抑制作用具有选择性.RSE浓度为2.0~10.0 g·L~(-1)时,可以显著抑制蓝藻的生长,同时强烈影响了藻细胞的叶绿素荧光强度和细胞大小.有毒水华鱼腥藻、鱼害微囊藻、有毒和无毒铜绿微囊藻的7d EC50分别为1.72、2.21、2.92和5.72 g·L~(-1).暴露于RSE的蛋白核小球藻和斜生栅藻,细胞生长被促进了并观测到有群体形成;而对羊角月牙藻来说,当RSE浓度为1.0~4.0 g·L~(-1)时月牙藻生长和叶绿素荧光强度被抑制,但是当RSE浓度为8.0~10.0g·L~(-1)时,月牙藻生长被显著促进.总之,RSE对蓝藻生长的抑制效果强于羊角月牙藻、蛋白核小球藻和斜生栅藻,蓝藻光合系统Ⅱ反应中心的敏感性和绿藻群体的形成可能是造成两者对水稻秸秆敏感性不同的重要原因.     

脂肪酸类物质的抑藻效应及其构效关系

研究了17种脂肪酸对产毒铜绿微囊藻、蛋白核小球藻以及斜生栅藻的抑制效应,比较了脂肪酸抑藻的构效关系.结果表明,17种脂肪酸单独作用对研究的3种藻均有一定的抑制作用,但对产毒铜绿微囊藻的抑制作用最强.脂肪酸类物质抑藻效应与其化学结构密切相关,脂肪酸不饱和程度越高抑制作用越佳,碳链越短抑藻效果越好,奇数碳脂肪酸的抑藻效果好于偶数碳脂肪酸.多种脂肪酸联合抑藻具有协同抑制作用.     

除草剂百草枯对蓝藻和绿藻的毒性

为评估除草剂百草枯对藻类生态系统的环境毒害效应,测定了百草枯对4株蓝藻:铜绿微囊藻(M.aeruginosa XW01,M.aeruginosa 7806)、平裂藻(Merismopedia sp.)、集胞藻(Synechocystis PCC 6803),以及两株绿藻:蛋白核小球藻(Chlorella pyrenoidosa)和绿球藻(Chlorococcum sp.472)的毒害效应,采用半效抑制浓度EC5o值、无观察效应浓度(NOEC)、最低观察效应浓度(LOEC)及慢性值(ChV)评价了百草枯对6株藻的毒性.结果表明:蓝藻对百草枯的敏感性显著大于绿藻,蛋白核小球藻的96 h-EC50值是铜绿微囊藻XW01的96 h-EC50值的7.4倍.百草枯毒害作用具有时间效应,暴露时间越长,毒害作用越强.     

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).     

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.     

Effects of arsenic on seed germination and physiological activities in wheat seedlings

The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.     

Sustainability： A view from the wind-eroded field

This article explores the assessment of sustainability in fields subject to wind erosion. In the first part, simple sustainability audits are examined, as of soil depth and nutrients. Direct measurement of these characteristics has many problems, largely because of huge variability in space and time at all scales. Modelling still has its problems, but it may be possible to overcome many of them soon. It is true that wind erosion preferentially removes soil nutrients, but there are imponderables even here. The nutrient balance in many of these soils includes considerable input from dust. In West Africa, it has been shown that the amounts of calcium and potassium that are added in dust are sufficient to fertilize dispersed crops. In mildly acidic sandy soils, such as those found on the widespread palaeo- aeolian deposits, much of the phosphorus is fixed and unavailable to plants by the time it is removed by wind erosion, so that erosion has no added downside. Most of the nutrients carried by dust have been shown to travel close to the ground （even when they are attached to dust-sized particles）, and so are trapped in nearby fallow strips, and are thus not lost to the farming system. Second, the sustalnabillty of a whole semi-arid farming system is explored. Wind erosion in semi-arid areas （like China, the Sahel and Norflawestern Europe） generally takes place on aeolian deposits of the recent geological past. Most of these soils are deep enough to withstand centuries of wind erosion before they are totally lost to production, and some of these soils have greater fertility at greater depth （so that wind erosion may even improve the soil）. Finally some remarks are made about environmental change in relation to sustainability.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Amplification of plasmid DNA bound on soil colloidal particles and clay minerals by the polymerase chain reaction

Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.