络合吸收脱除NO体系中FeⅢ(EDTA)的生物还原

利用驯化得到的微生物还原Fe^Ⅲ(EDTA)的研究结果表明,葡萄糖比乙醇和甲醇更适合于作为该体系的碳源;由于硝酸盐在反应过程中对Fe^Ⅲ(EDTA)的微生物还原形成抑制,选择铵盐为微生物生长的氮源;反应最适pH值范围为6~7;温度在30℃~40℃范围之间变化,Fe^Ⅲ(EDTA)还原率相差不大,温度大于40℃以后,还原率随温度升高而下降.碳源量和菌体接种量满足还原反应需要即可,过量碳源或菌体接种量对还原率没有明显的促进作用.在实验考察的浓度范围内,FeⅢ(EDTA)的生物还原符合1级反应动力学,最大反应速率γ_max=1.3 mmol·(L·h)^-1,半饱和速率常数k_m=53.5 mmol·L^-1.     

假单胞菌DN-1再生NO络合吸收液的特性

Fe^Ⅱ(EDTA)络合吸收脱除NO吸收速率快,吸收容量大,但是存在吸收液再生方面的缺陷.实验用自行分离得到的假单胞菌DN-1,将吸收液中的Fe^Ⅱ(EDTA)NO还原为N₂而进行再生.考察了不同碳源种类、碳源量、菌种量、pH值、温度、络合物浓度等条件下该菌种对Fe^Ⅱ(EDTA)NO的还原情况.结果表明,葡萄糖比醋酸钠、柠檬酸三钠和乙醇等更适合于作为该体系的外加碳源.当Fe^Ⅱ(EDTA)NO浓度为6.50 mmol·L^-1时,添加250 mg·L^-1的葡萄糖就能满足微生物的反应需要;DN-1还原适宜温度范围为40～45℃,适宜pH值为6.9～7.2;还原速率随菌体接种量的增多而加快;而Fe^Ⅱ(EDTA)NO浓度小于11.8 mmol·L^-1时,还原速率随着络合物浓度的增加而增加;超过这一浓度,还原速率不再随络合物浓度的增加而增加,反应速率基本不变.     

微生物降解苯酚废水的特性研究

通过对驯化微生物处理苯酚模拟废水的研究,考察了苯酚初始浓度、菌种投加量、葡萄糖添加量、废水pH值、反应温度等因素对苯酚降解效果的影响.结果表明,当苯酚浓度大于500mg/L时开始表现出对微生物的抑制作用,浓度高于700mg/L以后微生物降解效果不理想;当苯酚浓度为500mg/L时,微生物接种量大于400mg/L可获得最大降解速率;适量添加葡萄糖可促进微生物对苯酚的降解,但浓度超过0.2g/L以后由于底物竞争会对苯酚的降解形成抑制;生物降解苯酚的适宜pH值和温度范围分别为5.5～6.5和30～35℃.     

Shewanella oneidensis MR-1和Shewanella putrefaciens对V(Ⅴ)的还原及其影响因素

在实验室模拟培养条件下,研究Shewanella oneidensis MR-1和Shewanella putrefaciens在厌氧体系中对V(Ⅴ)的耐性试验,探讨在不同的V(Ⅴ)浓度、接菌量、pH值和不同蒽醌-2,6-二磺酸(AQDS)浓度下对V(Ⅴ)还原的影响,并通过扫描电镜(SEM)和X射线光电子能谱(XPS)进行表征.结果表明V(Ⅴ)浓度低于10mg/L时对S. oneidensis MR-1和S. putrefaciens的生长影响较小,V(Ⅴ)浓度超过20mg/L则会抑制其生长和V(Ⅴ)的还原;随着接菌量的增加,2种微生物对V(Ⅴ)的还原能力逐渐增强;2种微生物最适生长pH值均为7.0左右,弱碱性环境下2种微生物对V(Ⅴ)的还原率高于弱酸性环境;添加1mmol/L AQDS会加快2种微生物对V(Ⅴ)的还原.菌株培养3d后通过SEM分析,S. oneidensis MR-1和S. putrefaciens进行V(Ⅴ)还原的同时也伴有少量的吸附作用.利用XPS能谱分析表明S. oneidensis MR-1和S. putrefaciens将V(Ⅴ)还原为V(Ⅳ).     

乳化油碳源原位治理地下水中Cr(Ⅵ)静态批试验研究

通过投加碳源原位治理地下水中Cr(VI)的应用越来越广泛,碳源的选择是影响治理效果好坏的重要因素。实验中使用实际污染场地的土壤和含有Cr(VI)的溶液模拟地下水环境,加入自行配置的乳化油作为碳源促进土著微生物还原Cr(VI),分别探讨了乳化油碳源的作用,不同初始p H值和NO-3的存在对微生物还原Cr(VI)的影响。结果表明乳化油可以有效的促进土著微生物还原水中的Cr(VI),在2个周期内Cr(VI)的浓度分别从5.25 mg/L和5.1 mg/L降至0.05 mg/L和0 mg/L,还原率分别为99.05%与100%,与未加入乳化油碳源的组分相比还原率分别提高了33.33%和49.02%。实验中Cr(VI)的还原符合一级反应动力学,一级衰减速率常数保持在0.689 1~0.765 9 d-1,经过估算乳化油作为碳源促进微生物还原Cr(VI)的能力远大于0.986 mg/m L。NO-3能促进微生物利用乳化油还原Cr(VI),平均还原速率为0.138 2 mg/d,是未加入NO-3组分的2.1倍,这种促进作用在NO-3消耗殆尽之后依然能够继续发挥。乳化油的加入未引起p H值发生较大变化;p H值在8.8~9更有利于微生物还原Cr(VI)。     

Fe(Ⅱ)EDTA络合剂吸收NO的研究

在鼓泡反应器中,以Fe(Ⅱ)EDTA络合剂溶液为吸收液,给定NO与SO2的初始浓度分别为330 mg/m3与4 850 mg/m3,研究了温度、络合剂浓度等对Fe(Ⅱ)EDTA吸收NO的影响。结果表明,吸收液初始pH为6.5,温度为50℃,络合剂浓度为0.01 mol/L时,脱硝率可达到62.5%。并且得到Fe2+:EDTA=1∶1.5时脱硝率最好。SO2对络合剂单独脱硝有促进作用,可使脱硝率长时间保持在45%以上。在Fe(Ⅱ)EDTA溶液中添加4%氨水,对同时脱硫脱硝有一定的积极作用。     

应用青霉菌BX1活体吸附水中活性艳蓝KN-R

研究了染料高效吸附菌(青霉菌BX1)的生长条件及其对活性艳蓝KN-R的吸附特性为避免染料对其生长的毒害,本研究将菌体培养及其对染料的吸附分离.结果表明,青霉菌BX1生长分3个阶段:孢子活化、线性生长和菌体自解.菌体生长的最佳温度为30℃,最优碳源依次为淀粉＞木糖＞蔗糖＞麦芽糖＞葡萄糖＞乳糖,最佳pH值为4.0用培养48h的活菌体吸附水中的100mg/L的活性艳蓝KN-R,120min脱色率达93.7%,20℃时菌体(以干菌重计)对染料的最大饱和吸附量为159mg/g.     

微生物作用引起的铁铝氢氧化物吸附砷的还原与释放机制研究

地下水砷污染的形成机制目前尚不清楚,普遍认为,微生物对吸附于铁氧化物表面的As(Ⅴ)以及基质Fe(Ⅲ)的还原是砷释放的主要原因.本研究中以富集的混合菌群为接种微生物,以不同比例（Al∶Fe为1∶0、 1∶1、 0∶1）的铁铝氢氧化物为吸附剂,考察了微生物对吸附于这些载体上的As(Ⅴ)的还原和迁移作用.结果表明,接种微生物后,3种体系表现出不同程度的As释放,溶液中释放的As基本上是As(Ⅲ).在氢氧化铁体系中,溶解态As(Ⅲ)浓度仅为60 μg/L左右,微生物还原产生的As(Ⅲ)几乎全部存在于固相中;在Al∶Fe为1∶1的铁铝氢氧化物中,溶解态As(Ⅲ)大约为1.3 mg/L;氢氧化铝体系中,该值为7.8 mg/L,约占微生物还原总As(Ⅲ)的82%.而未接种的对照组均未检测到As(Ⅲ)以及明显的As释放.本研究还考察了吸附基质铁氧化物的还原对砷迁移的影响,结果表明,砷的还原发生在铁还原之前,铁的还原并没有引起砷的明显释放.因此,根据本实验结果推断,氢氧化铁吸附的As(Ⅴ)的还原及Fe(Ⅲ)的还原很可能不是造成地下水系统中砷释放的主要原因,而吸附于铝氧化物或其它矿物表面的As(Ⅴ)的还原可能引起了砷向水相迁移.     

纳米四氧化三铁对2,4-D的脱氯降解

采用纳米四氧化三铁(Fe3O4)降解水溶液中的2,4-二氯苯氧乙酸(2,4-D),考察了2,4-D初始浓度、纳米Fe3O4投加量、溶液pH和温度等因素对2,4-D降解率的影响.结果表明,纳米Fe3O4对2,4-D有显著的降解效果,初始浓度为10 mg/L的2,4-D, 48 h内降解率可达48%.纳米Fe3O4对2,4-D的降解是一个还原脱氯过程,反应体系中氯离子浓度随2,4-D浓度降低而升高.LC/MS分析表明,2,4-D降解的主要产物是苯酚,其他中间产物是2,4-二氯苯酚(2,4-DCP)、4-氯苯酚(4-CP)和2-氯苯酚(2-CP).溶液中2,4-D的降解符合准一级反应动力学,产物4-CP、2,4-DCP和苯酚的反应速率常数K分别为0.0043、0.0026和0.0032 h -1.环境条件对降解效率有显著影响,2,4-D初始浓度在0～10 mg/L、纳米Fe3O4投加量0～300 mg/L的范围内,2,4-D降解率随初始浓度和纳米Fe3O4投加量的增加而增大;pH对2,4-D的脱氯降解有显著影响,在pH为3.0时,纳米Fe3O4对2,4-D的还原脱氯效果最好;温度升高,可以提高脱氯反应速率.     

絮凝剂产生菌GA1 的营养优化及发酵动力学

 应用动力学方程考察了初始底物浓度对絮凝剂产生菌GA1 的生长及絮凝剂产率的影响.结果表明,GA1 对碳源、氮源的最大特征生长速率分别为0.099, 0.095h^-1,半饱和常数分别为1.503,0.315,说明GA1 对氮源比碳源更具亲和性. 当碳源或氮源为单一限制性底物,其碳源和氮源浓度分别为1~48 g /L 与0.1~4.0 g /L 时,GA1 特征生长速率和最大生长量随底物浓度增加而增大,.蔗糖浓度为40 g/L 时,絮凝剂的产率达到0.306g/g 蔗糖.理论上GA1 的最大细胞对蔗糖得率(Y ^*X / S )为0.381g/g ,菌体生长维持系数(m)为0.0311g/(g·h) ,说明絮凝剂产生菌GA1 具备工业化生产的潜力.     

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.     

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.     

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.     

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.