阴离子聚丙烯酰胺(APAM)和聚二甲基二烯丙基氯化铵(HCA)对给水厂污泥水分分布的影响及其与污泥颗粒的作用机制

为比较APAM和HCA对给水厂污泥调理的效果并探究其作用机制,测定了污泥调理前后的毛细吸水时间（CST）、污泥比阻（SRF）、溶解性有机污染物含量（DOC）、Zeta电位和絮体粒径的变化情况,并结合三维荧光谱图、液相-有机碳联用（LC-OCD）、热重差热法（TG-DTA）以及傅立叶红外（FTIR）的变化进行分析.结果表明,APAM和HCA的最佳投加量分别为0.05和0.10 g·L^-1,与之对应的CST分别从71.0 s降到25.8 s和37.6 s,SRF从9.72×10¹² m·kg^-1降到4.18×10¹² m·kg^-1和5.70×10¹² m·kg^-1,APAM的调理效果占优.HCA仅可释放毛细水,而APAM可释放污泥的毛细水和表面吸附水.APAM通过氢键的吸附架桥形成大块絮体以改善污泥脱水性能,Zeta电位的升高和有机物的变化显示出电中和及去水化作用是HCA的主要调理机制.本研究结果可为给水厂污泥脱水有机药剂的选择提供数据基础.     

污泥生物炭活化过一硫酸盐降解环丙沙星

以脱水干化污泥为原料,经450℃热解制成污泥生物炭（BC）,活化过一硫酸盐（PMS）,构建BC/PMS体系,降解环丙沙星（CIP）.采用扫描电子显微镜（SEM）、X射线能谱（EDS）、傅里叶变换红外吸收光谱（FTIR）、X射线衍射（XRD）、Zeta电位分析仪和电子自旋共振（EPR）分析了BC的理化性质;考察了BC投加量、PMS投加量、初始pH值和无机阴离子对BC/PMS体系降解CIP效果的影响;通过自由基淬灭实验和X射线光电子能谱（XPS）分析,深入探讨了BC/PMS体系对CIP降解机制.结果表明,CIP降解率随BC投加量和PMS投加量增大而升高,随溶液初始pH增大而降低,在BC 1.0 g·L^-1、PMS 3.0 mmol·L^-1、初始pH 6.0、CIP 20 mg·L^-1和反应时间120 min时,CIP降解率为49.09%;SO₄^2-和NO₃^-对BC/PMS体系降解效果无显著影响,HCO₃^-和Cl^-具有明显抑制作用;BC/PMS体系降解CIP是自由基途径（·OH和SO₄^-·）和非自由基途径（¹O₂）共同作用的结果,降解路径主要包括哌嗪环开环和羟基化反应.     

不同剪切条件下活性污泥理化性质及脱水性能的响应特征

通过实验室模拟,研究了原始活性污泥和最佳投药量下调理污泥的毛细管吸水时间、粒度、分形维数、Zeta电位和上清液SS值等参数随剪切强度与时间的变化规律,确定了污泥的剪切敏感性和强度因子及粒径、强度等参数与速度梯度（G）值之间的关系.结果表明,剪切导致原始污泥和调理污泥的脱水性能变差,相应的临界剪切强度分别为700 r·min^-1（G=554.6 s^-1）和400 r·min^-1（G=239.5 s^-1）,并暴露出更多带负电荷的新鲜表面.原始污泥的质量分形维数受剪切作用影响不大,其粒径在一定范围内随剪切强度的增加而减小,而调理污泥絮体的质量分形维数却随之上升,粒度随之降低.原始污泥与调理污泥絮体的K_SS值分别为4.73×10^-2、8.33×10^-2,稳定絮体粒径常数γ值分别为4.99×10^-2、35.19×10^-2,且前者的强度因子较高,它们均表明原始污泥的剪切稳定性更好.剥离是原始污泥剪切破碎的主要机制,而调理污泥在临界剪切强度以上呈现越来越明显的剪切分裂机制.此外,污泥粒径、强度均与G值呈现较好的指数关系.     

基于酸化与Fenton试剂处理的焦化污泥脱水过程及其重金属迁移研究

焦化废水污泥作为典型的危险废物,含有氰类、酚类、稠环芳烃与多环芳烃等有毒成分,严重影响人类健康与生态环境安全,焦化污泥减量化是其处理处置中重要一环.针对焦化废水污泥高有机物、高油含量特点,采用酸化+Fenton试剂进行复合调理改性,改性后污泥毛细吸水时间(Capillary Suction Time,CST)、比阻(Specific Resistance to Filtration,SRF)分别达到51.2 s和0.043×10¹³ m·kg^-1,药剂投加量通过响应表面法(Response Surface Method,RSM)进行优化,在实验室板框脱水实验中得到30%硫酸投加量为37.8 mL·L^-1,FeSO₄、H₂O₂和生石灰投加量分别为47.93、34.29和143.21 mg·g^-1DS时,脱水后泥饼含水率为55.82%,滤液pH为6.66,达到污泥深度脱水目标.采用酸化+Fenton试剂复合处理可使焦化废水污泥有效减量化,其良好的深度脱水效果能为后续的无害化处置奠定基础,并有效降低处置费用.     

核壳结构KNbO3@Co(OH)2的制备及其活化过一硫酸盐降解帕珠沙星的研究

制备了以KNbO₃为载体材料的Co（OH）₂复合材料并对其进行了详细的表征,分析了材料的组成成分、组成形态进而确定了其为核壳结构形貌的KNbO₃@Co（OH）₂.利用合成的样品作为催化剂活化过一硫酸盐（peroxymonosulfate,PMS）来降解帕珠沙星（pazufloxacin,PZF）,结果表明制备的催化剂对PZF的去除效率显著增加.讨论了不同初始PMS剂量对降解效率的影响,发现随着PMS增加可活化生成更多的硫酸根自由基（sulfate radicals,SO₄^·-）和羟基自由基（hydroxyl radicals,HO^·）来降解PZF,但继续增大PMS用量降解效率未见明显提升.酸性和中性pH值条件下利于反应活化PMS降解PZF,而碱性体系减缓反应,甚至强碱体系更易形成Co（OH）₂沉淀不利于反应体系中活性组分CoOH⁺的形成,大大抑制了催化性能.此外,在体系中加入淬灭剂叔丁醇（tert-Butanol,TBA）或者乙醇（ethanol,ETOH）进行自由基的淬灭实验,结果表明SO₄^·-自由基为体系降解PZF过程中主要贡献的自由基,而HO^·自由基的贡献较少.催化剂具有较好的稳定性5次循环之后仍能在10 min之内完全去除PZF.本研究提出了新的思路为制备其他载体的Co（OH）₂核壳结构提供参考依据,同时将该催化剂结合高级氧化技术应用到水体新兴有机污染物净化领域具有很好的应用前景.     

MoS2强化Fe2+活化单过硫酸盐去除磺胺甲恶唑和还原六价铬的研究

采用二硫化钼（MoS₂）作为助催化剂加入到亚铁离子（Fe²⁺）/单过硫酸盐（PMS）体系,去除溶液中的磺胺甲恶唑（SMX）和还原六价铬（Cr（Ⅵ））,分别对SMX及SMX与Cr（Ⅵ）共存情况下的去除效果进行研究,并考察了MoS₂、Fe²⁺、PMS、SMX投加量对SMX和Cr（Ⅵ）去除效果的影响.结果表明,在[MoS₂]₀=0.9 g·L^-1,[Fe²⁺]₀ =0.3 mmol·L^-1,[PMS]₀=1 mmol·L^-1,[Cr（Ⅵ）]₀=100 μmol·L^-1,[SMX]₀=25 μmol·L^-1,初始pH为3.0的条件下反应30 min时,SMX的去除率和Cr（Ⅵ）的还原率分别达到98.8%和99.2%;实验中MoS₂和Fe²⁺浓度与Cr（Ⅵ）还原率呈正相关,而PMS浓度过高则会抑制Cr（Ⅵ）的还原;MoS₂/Fe²⁺/PMS体系下Cr（Ⅵ）的还原机理不仅与MoS₂还原生成的亚铁离子有关,Cr（Ⅵ）也能够被MoS₂或PMS直接还原.EPR实验表明,MoS₂/Fe²⁺/PMS体系中主要的自由基是SO₄^·-和HO^·.     

Fenton试剂与骨架构建体复合调理剂对污泥脱水性能的影响

将Fenton试剂与骨架构建体联用作为复合调理剂开展了污泥调理及脱水试验.结果表明,赤泥与水泥作骨架构建体调理后,污泥脱水性能和脱水液pH均优于石灰与水泥调理污泥.以污泥比阻(SRF)为评价指标,开展了Fenton反应时间、初始pH及调理剂投加量对污泥脱水性能影响的单因素试验.当Fenton反应时间为90 min,初始pH为5,水泥、赤泥、Fe²⁺和H₂O₂的投加量(以污泥干固体质量计)分别为300、300、40和32 mg·g^-1时,污泥比阻降低率可达94.25%±0.21%.在此基础上,以泥饼含水率为响应指标,利用表面响应法对调理剂投加量进行优化.结果表明,水泥、赤泥、Fe²⁺和H₂O₂的投加量分别为287、287、46和37 mg·g^-1,泥饼含水率可降至47.7%±0.8%.调理后污泥的粒径减小,比表面积增大,粘度减小,Zeta电位由负变正,说明该复合调理剂能有效地破解胞外聚合物(EPS),提高污泥脱水性能.     

磁性生物炭负载α-MnO2活化过一硫酸盐降解2,2',4,4'-四溴联苯醚

环境中的多溴联苯醚（PBDEs）对人类健康和生态环境存在潜在危害,开发高效、经济和环保的高级氧化体系对其进行有效降解具有重要意义.利用水热法合成的磁性生物炭负载二氧化锰复合材料（α-MnO₂/MWB）作为催化剂,有效活化过一硫酸盐（PMS）降解2,2'',4,4''-四溴联苯醚（BDE-47）,通过SEM、XRD、FT-IR和BET等手段对材料进行表征分析,同时探究了材料对PMS的催化活化能力.结果表明,α-MnO₂/MWB具有最佳的催化性能,在α-MnO₂/MWB负载质量比为1：2、催化剂投加量为0.05 g·L^-1、PMS浓度为5 mmol·L^-1的条件下,对1 mg·L^-1 BDE-47的降解率达到94%.溶液初始pH对体系的影响较小,氯离子（Cl^-）和腐殖酸（HA）对BDE-47的降解有抑制作用,随其浓度升高抑制作用增强,硝酸根离子（NO₃^-）和碳酸氢根离子（HCO₃^-）对降解几乎无影响.通过自由基淬灭实验证明SO₄^-·和·OH是该体系降解BDE-47的两种关键自由基,其中SO₄^-·占主导地位.反应前后材料的XPS表征分析表明,Mn和Fe元素的价态转化是活化PMS的主要原因.α-MnO₂/MWB经重复利用4次,仍保持着高效的催化性能.     

聚乙烯与磺胺二甲嘧啶复合胁迫对大豆种子萌发及幼苗生长生理特征的影响

土壤环境中微塑料吸附抗生素产生复合污染已不可避免,但二者复合胁迫下的植物生物效应尚不清楚.以大豆品种晋豆21号为试材,采用种子萌发试验和幼苗盆栽试验研究聚乙烯（PE）和磺胺二甲嘧啶（SMZ）不同单一及复合处理对大豆种子萌发、幼苗生长、光合参数、叶绿素荧光参数和氮代谢的影响.结果表明,单一PE处理对大豆种子萌发和幼苗生长生理的影响总体表现为"低促高抑"的规律,较低水平PE［10 mg ·L^-1（或mg ·kg^-1）］处理对大豆种子萌发、幼苗生长、光合作用和氮代谢有促进作用,但较高水平PE［100 mg ·L^-1和200 mg ·L^-1（或mg ·kg^-1）］的抑制作用显著;单一SMZ处理对大豆种子萌发和幼苗生长生理产生不同程度的抑制作用,且抑制程度随着SMZ处理水平的增加呈升高趋势.不同水平PE和SMZ复合处理下,较低水平PE的加入能够缓解单一SMZ处理对大豆的抑制作用,以10 mg ·L^-1（或mg ·kg^-1） PE+1 mg ·L^-1（或mg ·kg^-1） SMZ处理的综合缓解效果最佳,具体表现为较单一SMZ处理增加了大豆种子发芽势、发芽率、发芽指数、活力指数、株高、根长、地上部及根部鲜重、P_n、G_s、T_r、叶绿素含量、F_v/F_m、Φ_PSⅡ、ETR、qP和NR等氮代谢关键酶活性,降低了种子平均发芽时间、C_i、NPQ、NO₃^--N和NH₄⁺-N含量;而较高水平PE的加入增强了SMZ处理对大豆的抑制作用,且抑制程度随着SMZ处理水平的增加呈升高趋势,其中200 mg ·L^-1（或mg ·kg^-1） PE+50 mg ·L^-1（或mg ·kg^-1） SMZ处理的抑制程度最大.综上可知,低水平PE能够一定程度缓解单一SMZ胁迫对大豆种子和幼苗的抑制作用,而高水平PE的加入则与SMZ产生协同作用,加剧了单一胁迫处理的毒害效应.     

太湖沉积物好氧细菌空间分布与氮磷来源及风险

沉积物中氮磷释放到湖水中会加剧湖泊的富营养化,危害生态安全和人类健康.微生物在氮磷转换中不可或缺,准确分析沉积物中氮磷分布特征和来源以及与微生物的关系是湖泊富营养化管控的重要前提.以太湖为研究区,采集30个表层沉积物样品,测定并分析了粒度、pH、有机质（OM）、溶解性有机碳（DOC）、全磷（TP）、全氮（TN）、硝态氮（NO₃^--N）和溶解性有机氮（DON）等指标含量及空间分布特征,同时利用营养琼脂（NA）培养基以平板计数法测定好氧细菌（AB）数量.结合主成分分析（PCA）和Pearson相关分析探究了太湖沉积物和AB空间分布特征和来源.采用综合污染指数法和有机污染指数法研究了太湖沉积物污染特征.结果表明,太湖表层沉积物指标平均值如下：AB为9.25×10⁴ CFU ·g^-1,平均粒径（M_Z）为17.59 μm,pH为7.62,ω（OM）为15.05g ·kg^-1,ω（DOC）为71.60mg ·kg^-1,ω（TP）为598.13mg ·kg^-1,ω（TN）为1113.92 mg ·kg^-1,ω（NO₃^--N）为3.22mg ·kg^-1,ω（DON）为22.60mg ·kg^-1.综合污染指数（FF）显示太湖中的点位13%为中度污染,87%为重度污染.TN除在湖心区、南部湖区和东太湖西部的部分湖区为轻度污染外,其余区域为中重度污染.除竺山湾为重度污染外,太湖中TP整体上为轻中度污染.有机污染指数（OI）表明,太湖沉积物有机污染较轻,主要与有机氮（ON）污染有关.太湖中DOC、DON、TN和OM主要来源于水生植物的影响,TP和AB主要来源于河流外源输入的影响.研究将为湖泊富营养化治理提供理论支撑,也为进一步研究AB去除沉积物中氮磷污染提供新思路.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

ＲｅｍｏｖａｌｏｆｈｅａｖｙｍｅｔａｌｓｆｒｏｍｓｅｗａｇｅｓｌｕｄｇｅｂｙｌｏｗｃｏｓｔｉｎｇｃｈｅｍｉｃａｌｍｅｔｈｏｄａｎｄｒｅｃｙｃｌｉｎｇｉｎａｇｒｉｃｕｌｔｕｒｅＷｕＱｉｔａｎｇ，ＮｙｉｒａｎｄｅｇｅＰａｓｃａｓｉｅ，ＭｏＣｅｈｕｉＦ...     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.