三叶鬼针草毛状根的诱导及其对重金属Cd、Pb蓄积

利用发根农杆菌诱导植物毛状根多被利用于药用植物生物技术工程方面.目前植物修复也利用毛状根生长快,侧根分支多与污染源接触表面积大等优点进行污染水体的修复.三叶鬼针草自然植株具有重金属Cd的超富集能力,本文利用发根农杆菌C58C1诱导三叶鬼针草叶片产生毛状根,在1/2MS的液体培养基能稳定、正常生长,并表现对重金属Cd、Pb极强的忍耐和蓄积能力.单一处理时,三叶鬼针草毛状根在Cd≤50μmol·L-1和Pb≤25μmol·L-1时均能正常生长,生物量积累与对照没有明显差异;随处理浓度增加,当Cd≥100μmol·L-1、Pb≥50μmol·L-1时,毛状根生物量积累明显受到抑制.Cd-Pb复合处理时,低浓度Cd(25μmol·L-1)与Pb复合处理,随Pb浓度增加(25、100、200μmol·L-1)三叶鬼针草毛状根生物量逐渐减少,抑制效应随Pb增加而加剧;高浓度Cd(200μmol·L-1)与Pb复合处理,随Pb浓度增加(25、100、200μmol·L-1)生物量逐渐减少,抑制效应随Pb增加而加剧.高浓度Cd与Pb复合处理,毛状根生长受到抑制更严重.单一处理时,当Cd≤50μmol·L-1时,随处理浓度增加Cd蓄积量增加,当Cd≥100μmol·L-1时,重金属蓄积量明显降低,随处理浓度进一步增加,重金属蓄积量已无明显变化.Pb≤100μmol·L-1处理时,毛状根对Pb蓄积量随处理浓度增加微弱降低,但不明显;当Pb≥200μmol·L-1时,随处理浓度增加,毛状根对Pb蓄积量明显降低.Cd-Pb复合胁迫,低、中Pb(Pb≤100μmol·L-1)促进毛状根对Cd富集,高浓度Pb(Pb≥200μmol·L-1)则抑制Cd的富集;低浓度Cd仅对低浓度25μmol·L-1时Pb有微弱促进积累效应,其余均抑制Pb富集.这说明三叶鬼针草毛状根可作为重金属Cd、Pb污染水体潜在的植物修复新材料.     

三岔河沿岸植物铅、镉富集特性的研究

以紫茎泽兰（EupatoriumadenophorumSpreng）、青蒿（HerbaArtemisiaeAnnuae）、三叶鬼针草（Bidenspilosa）、野牡丹（MelastomaAfffine D．Don）、光叶蕨（Knuiwatsukiacuspidata）为例,分别在河边、路边、山上和污水灌溉的旱地4个采样点采取5种植物的根部和茎叶,测量重金属元素Pb、Cd的含量、富集系数和转移系数并分析数据。结果表明,各种植物不同器官在不同环境中对重金属元素Pb、Cd的富集和转移水平各不相同,就平均水平来说三叶鬼针草对重金属Pb、Cd的富集系数较大,转移系数也高,但其对Pb的转移量明显高于Cd的转移量;紫茎泽兰对重金属元素Cd的富集和转移速度相对高于其它4种植物,说明紫茎泽兰对Cd的吸收和转移比较快,可作为受镉污染土壤进行改良的备选植物种。     

活化剂与植物联合修复Pb、Zn和Cd污染土壤研究

添加外源活化剂调控和间作是提高重金属污染土壤植物修复的有效方法。通过盆栽试验研究外源添加乙二胺四乙酸（EDTA）、聚天冬氨酸（PASP）和乙二胺四乙酸+聚天冬氨酸（EDTA+PASP）对少花龙葵、翅果菊修复Pb、Zn和Cd复合污染土壤的影响。结果表明：添加活化剂提高了土壤p H值和土壤有机质含量。EDTA+PASP对土壤重金属有效态含量影响不大,但EDTA与PASP对土壤重金属有效态含量分别表现为活化和钝化作用。土壤中添加PASP使单作翅果菊株高增加5.98%,使单作少花龙葵鲜重增加36.82%,使间作少花龙葵地下部的干重增加52.93%。虽然EDTA对植物生物量影响不大,但EDTA能够活化土壤中的重金属,单作和间作条件下均能够促进翅果菊和少花龙葵对Pb和Zn吸收,分别使翅果菊地下部Pb和Zn提取量提高187.63%和21.21%,使翅果菊地上部Zn浓度提高62.29%。土壤添加PASP使单作翅果菊和间作翅果菊地上部Cd含量分别降低38.88%和58.86%。植物对Pb、Zn和Cd总提取量主要表现为间作>少花龙葵>翅果菊。少花龙葵和翅果菊在EDTA处理下Pb、Zn和Cd富集...     

组配改良剂联合硅肥对Cd污染稻田的修复效果

选取湖南省浏阳市某Cd污染稻田进行田间试验,研究组配改良剂石灰石+海泡石（LS）、基施硅肥及叶面喷施硅肥对Cd污染稻田修复效果,结果表明：（1）基施硅肥90kg/hm²和叶面喷施硅肥（0.2,0.4g/L）对土壤pH值无明显影响,添加LS（2250,4500kg/hm²）的各处理均显著提高土壤pH值（P < 0.05）.（2）基施硅肥90kg/hm²分别降低土壤交换态、毒性特征浸出（TCLP）提取态Cd含量20.0%和18.5%,叶面喷施硅肥对土壤Cd两种提取态含量无明显影响,添加LS的各处理（2250,4500kg/hm²）分别使土壤交换态、TCLP提取态Cd含量降低25.8%~49.9%、26.4%~44.5%.（3）3种单一技术措施均能明显降低水稻各部位Cd含量,但降低糙米中Cd含量的效果低于3种技术措施的组合处理;“组配改良剂LS+基施硅肥+叶面喷施硅肥”各处理（JL1F1、JL1F2、JL2F1、JL2F2）使水稻糙米中Cd含量降低25.6%~70.5%.（4）“组配改良剂LS+基施硅肥+叶面喷施硅肥”的组合技术处理能显著降低土壤中Cd的有效性,显著降低水稻各部位中Cd含量,其中JL2F2处理效果最佳,能使对照糙米Cd含量从0.66mg/kg降低到0.19mg/kg,实现中重度Cd污染稻田的水稻安全生产.     

三叶鬼针草等7种常见菊科杂草植物对重金属的集特征

超富集植物是植物修复重金属污染土壤技术最主要的内容,而超富集植物的筛选是植物修复技术的难点和重点.采用室外盆栽试验的方法,研究了我国北方较常见的7种菊科植物对重金属的超富集特征.盆栽筛选试验表明,蒲公英和三叶鬼针草对Cd单一及Cd-Pb-Cu-zn复合污染的耐性较强,植物地上部镉含量分别高于其根部镉含量,地上部镉的富集系数也均大于1,具备了镉超富集植物的基本特征.以这2种植物为试材的盆栽浓度梯度试验表明,当土壤中Cd投加浓度分别为25、50、100 mg·kg-1时,三叶鬼针草地上部生物量没有明显下降(P<0.05),Cd含量均大于其根部Cd含量,且其叶中Cd含量均大于100 mg·kg-1,达到了Cd超富集植物应达到的临界含量标准.而蒲公英在这3个处理条件下,其叶片中Cd含量均没有超过100 mg·kg-1.可见只有三叶鬼针草完全具有镉超富集植物的基本特征,是镉超富集植物.     

外源脯氨酸对Cd胁迫下107杨光合与叶绿素荧光特性的影响

为揭示Cd胁迫下外源脯氨酸对107杨（Populus×euramericana cv.‘74/76’）光合与叶绿素荧光特性的影响,以一年生107杨苗木为试验材料,采用盆栽控水试验,研究了添加不同浓度（0、10和20 mmol/L）外源脯氨酸对Cd（0、100、200和300 mg/kg）胁迫下107杨叶片光合气体交换参数、光响应参数和叶绿素荧光参数的影响.结果表明:①Cd作为独立因子可显著影响107杨叶片的光合气体交换参数、光响应参数和叶绿素荧光参数,外源脯氨酸作为独立因子对这些参数无显著影响,Cd与脯氨酸的交互作用对这3类参数均有显著影响.②随着w（Cd）的增加,107杨叶片净光合速率（P_n）、蒸腾速率（T_r）、气孔导度（G_s）和水分利用效率（WUE）的变化趋势基本一致,均显著下降,而胞间CO₂浓度（C_i）呈显著上升趋势.与单独Cd处理组相比,在w（Cd）为200 mg/kg处理下,添加外源c（脯氨酸）为10 mmol/L时苗木叶片的P_n显著提高123.12%;WUE、PSⅡ原初反应最大量子效率（F_v/F_m）、实际光化学量子效率（φ_PSⅡ）、光化学淬灭系数（qP）和表观光合电子传递速率（ETR）分别显著提高43.73%、6.52%、27.99%、28.96%和63.26%;而非光化学淬灭系数（NPQ）显著降低19.97%.研究显示,w（Cd）低于200 mg/kg时,外源添加脯氨酸处理可增强107杨的PSⅡ光能转换效率和光强利用效率,防止过剩光能对光合机构的伤害,从而提高植株抗逆性与适应性,且以c（脯氨酸）为10 mmol/L时的处理效果较好.      

三叶鬼针草等7种常见菊科杂草植物对重金属的超富集特征

超富集植物是植物修复重金属污染土壤技术最主要的内容,而超富集植物的筛选是植物修复技术的难点和重点.采用室外盆栽试验的方法, 研究了我国北方较常见的7种菊科植物对重金属的超富集特征. 盆栽筛选试验表明, 蒲公英和三叶鬼针草对Cd单一及Cd-Pb-Cu-Zn复合污染的耐性较强, 植物地上部镉含量分别高于其根部镉含量,地上部镉的富集系数也均大于1, 具备了镉超富集植物的基本特征. 以这2种植物为试材的盆栽浓度梯度试验表明, 当土壤中Cd投加浓度分别为25、 50、 100 mg·kg^-1时,三叶鬼针草地上部生物量没有明显下降(p<0.05), Cd含量均大于其根部Cd含量, 且其叶中Cd含量均大于100 mg·kg^-1, 达到了Cd超富集植物应达到的临界含量标准.而蒲公英在这3个处理条件下,其叶片中Cd含量均没有超过100 mg·kg^-1. 可见只有三叶鬼针草完全具有镉超富集植物的基本特征,是镉超富集植物.     

Cd胁迫下不同外源植物激素对水稻幼苗抗氧化系统及Cd吸收积累的影响

为了探讨外源添加植物激素对Cd胁迫下水稻幼苗的抗氧化系统及Cd吸收积累情况的影响,减少Cd在植物体内的运输和积累,从而来缓解Cd对水稻的胁迫.以中嘉早17水稻幼苗为研究对象,进行水培试验,设置0、5和25 μmol·L^-1这3个Cd浓度处理,3种外源植物激素处理：不添加植物激素、100 μmol·L^-1褪黑素（MT）、0.2 μmol·L^-12,4-表油菜素内酯（EBL）和0.2 μmol·L^-1茉莉酸（JA）,共12个处理,每个处理重复3次.测定水稻幼苗体内Cd的含量,同时也对水稻幼苗地上部及根部丙二醛（MDA）、过氧化物酶（POD）、过氧化氢酶（CAT）和还原型谷胱甘肽（GSH）含量进行分析.结果表明,在5 μmol·L^-1和25 μmol·L^-1 Cd胁迫下,外源添加MT、EBL和JA使地上部MDA含量显著降低了11%~24%,但是根系与地上部情况恰好相反,添加3种外源物质均导致根系中MDA含量增加,其中MT和EBL现象明显,在5 μmol·L^-1 Cd胁迫下,与CK相比,分别提高了45.5%和20.0%;在25 μmol·L^-1 Cd胁迫下,分别提高了46.2%和19.8%.外源添加植物激素可显著增加水稻幼苗地上部和地下部POD、CAT的活性,降低GSH以及Cd的含量,在5 μmol·L^-1 Cd胁迫下,添加MT、EBL和JA导致水稻地上部Cd含量分别降低39.4%、40.1%和51.6%,根部分别降低38.9%、40.2%和7.0%;25 μmol·L^-1 Cd胁迫下,地上部Cd含量分别降低18.9%、14.5%和35.6%,根部分别降低85.3%、81.1%和56.5%.由此可见,通过外源添加低浓度植物激素MT、EBL和JA,可缓解Cd对水稻的胁迫,降低Cd对水稻的毒害作用.     

两种外源有机酸对土壤Cd形态及秋华柳Cd积累的影响

秋华柳(Salix variegate Franch.)因具有良好的重金属耐受和积累能力,常被作为重金属污染土壤修复工程物种.通过盆栽模拟试验,分析了不同浓度外源草酸和酒石酸处理下土壤Cd形态的变化和秋华柳Cd含量的积累特征,以探究外源有机酸在Cd污染土壤植物修复中的应用潜力.结果表明:添加外源酒石酸可显著降低土壤非有效性Cd含量,增加土壤中以可交换态Cd为主的有效性Cd含量,促进了秋华柳对Cd的积累,同时也显著提升了植株的富集系数,其中添加5 mmol/kg酒石酸的处理效果最佳.与CK相比,添加5 mmol/kg外源酒石酸可显著增加秋华柳根、茎和叶中的Cd积累量,地上、地下部分和全株的Cd积累量分别提升了62.2%、75.9%和78.4%,地上和地下部分富集系数分别提升了173.0%和178.8%.添加外源草酸对土壤有效性Cd含量没有显著影响,秋华柳根、茎和叶的Cd含量和积累量无明显提升.研究显示,添加较低浓度的酒石酸更有利于增加土壤中可交换态Cd含量和有效性Cd含量,促进秋华柳对土壤中Cd的吸收和积累,增强秋华柳对Cd污染土壤的修复能力,可应用于Cd污染土壤的植物修复.      

三叶鬼针草幼苗对镉污染的耐性及其吸收积累特征研究

通过盆栽实验研究了镉(Cd)胁迫下三叶鬼针草(Bidens pilosaL.)幼苗的耐性能力(包括生长反应和生理生化特性)以及对Cd的吸收积累特征.结果表明,当土壤中投加的Cd浓度为≤32 mg/kg时,三叶鬼针草植物的生长和发育没有受到抑制,与对照相比,地上部和根部生物量分别增加了32.4%~44%和29.1%~57.6%,其中,当Cd处理浓度为8 mg/kg时,地上部干重达到最大值,为0.22 g/pot.在不同Cd处理下,叶绿素(Chl)和可溶性蛋白(SP)含量下降,分别比对照处理降低了23.3%和41.5%;超氧化物歧化酶(SOD)活性随着Cd浓度增加先有所抑制,后逐渐增大;过氧化物酶(POD)活性和丙二醛(MDA)含量随Cd处理浓度增加而增大,分别比对照增加了1.2~6.6和1.1~1.5倍.然而,当Cd浓度为50~100 mg/kg时,显示出对三叶鬼针草幼苗的生长发育和生理生化特征都产生了一定的负效应,说明三叶鬼针草对Cd污染的耐性能力具有一定的阈值.在梯度实验中,植物体内Cd的富集系数和转移系数都大于1.0.当土壤中Cd含量达到100 mg/kg时,地上部Cd含量达到119.1 mg/kg,具备...     

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.     

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.     

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.     

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.     

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

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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.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.