有机无机氮配施对不同程度盐渍土硝化和反硝化作用的影响

以内蒙古河套灌区轻度盐渍土S₁（EC=0.62 dS·m^-1）及中度盐渍土S₂（EC=1.17 dS·m^-1）为对象,研究硝化和反硝化进程对盐渍化程度和有机无机氮配施比例的响应及其影响因素.本试验设置了6个处理,包括不施氮（CK）、单施无机氮（U₁）以及用有机氮（U₃O₁、U₁O₁、U₁O₃和O₁）替代25%、50%、75%和100%的无机氮.结果表明,盐度升高会降低土壤硝化势而提高土壤反硝化能力,同一处理S₁土壤硝化潜势较S₂土壤高出28.81%~69.67%,而反硝化能力降低17.16%~88.91%.盐度升高会降低AOB丰度及硝化贡献率,但会增加AOA丰度和硝化贡献率;盐度增加会提高土壤nirK和nirS型菌丰度,同时会增加N₂O/（N₂O+N₂）产物比,但会抑制nosZ丰度.S₁土壤,以U₁O₁处理硝化势和反硝化能力最大,较单施化肥增幅分别达到18.59%和15.87%;S₂土壤,各施肥处理之间土壤硝化势差异不显著,反硝化能力以O₁处理最大,较单施化肥提高88.26%.S₁和S₂盐渍土分别以U₁O₁及O₁处理获得较高的AOB基因丰度及硝化贡献率,且增大了nirS和nosZ基因丰度,并显著降低N₂O/（N₂O+N₂）产物比.综上,相比单施无机氮,轻度盐渍土以有机无机氮各半配施,中度盐渍土以单施有机氮更加利于土壤硝化反硝化过程进行.     

密云水库入库河流微生物群落演替对氮素形态转化的影响

密云水库是北京市重要的地表饮用水源地,但近年来,密云水库库区及入库河流中的总氮（TN）浓度呈现连年上升的趋势.以密云水库上游典型入库河流牤牛河为例,考察各形态氮素变化的空间分布规律,并从微生物群落组成和功能预测的视角,解析氮素形态的转化,以期为密云水库的氮污染治理提供科学依据.结果表明,密云水库上游除TN外,其余水质理化指标均满足我国地表水环境质量标准（GB 3838-2002）的Ⅱ类标准.入库河流TN浓度显著高于库区（P<0.05）,且以NO₃^--N为主,占比为77.7%~92.9%.半城子水库库区的C/N较高,有助于反硝化脱氮的发生,表现出一定自净能力.牤牛河水体和底质中微生物群落结构具有显著差异,呈现一定的空间分布特征,高NO₃^--N浓度是影响微生物群落结构演替的主要环境因子.牤牛河中存在大量硝化和反硝化功能微生物,反硝化菌相对丰度高于硝化菌,且均呈现出底质略高于水体的特点.牤牛河优势硝化菌和反硝化菌分别为Nitrosopumilus和Pseudomonas.PICRUSt2功能预测结果表明,牤牛河微生物氮代谢以NO₃^--N还原模块为主,且主要发生于水体中;硝化过程的功能基因在水体中的丰度最高,主要为narGH;而参与NO₃^--N还原反应的主要功能基因为底质中的异养反硝化菌（DNRA）所携带的nirBD,而反硝化模块的功能基因主要为nirK.     

稻田土壤氧化亚氮产生潜势、反硝化功能基因丰度和群落结构的垂向分布

土壤中氧化亚氮（N₂O）的释放量占全球N₂O释放总量的60%.其中，稻田土壤是N₂O最主要的释放源.反硝化过程是稻田土壤N₂O生成的主要微生物过程之一.本研究选取广东韶关稻田垂向土壤（0~100 cm）为研究对象，通过乙炔抑制剂法测定了N₂O产生潜势和反硝化潜势，并利用针对特异性功能基因的实时荧光定量和高通量测序技术分别分析反硝化功能基因丰度和反硝化微生物群落结构.结果显示：0~10 cm深度的土壤样品N₂O产生潜势最高，可达（0.020±0.0035）μg·g^-1·h^-1.反硝化功能基因中，nirK基因的丰度峰值（（1.51±0.0015）×10⁸ copies·g^-1）出现在0~10 cm深度，而nosZ和nirS基因的丰度峰值（（4.29±0.0015）×10⁷ copies·g^-1和（8.86±0.0010）×10⁷ copies·g^-1）均出现在10~20 cm深度.稻田垂向土壤中N₂O产生潜势和相关的反硝化功能基因（nosZ、nirK和nirS）丰度均随土壤深度的增加而逐渐降低.其中在所有深度的土壤样品中nirK基因的丰度均高于nirS.基于nirK基因的高通量测序结果发现慢生根瘤菌（Bradyrhizobium）的相对丰度最高（44.06%±6.14%，n=6）.相关性分析表明，稻田土壤中N₂O产生潜势与环境因子（TN、TC和含水率）、反硝化功能基因丰度以及慢生根瘤菌（Bradyrhizobium），罗河杆菌属（Rhodanobacter）和亚硝化螺菌属（Nitrosospira）的相对丰度呈正相关.上述结果表明稻田土壤中环境因子和反硝化功能基因丰度影响了N₂O产生潜势的垂向分布.     

不同水分管理条件下添加生物炭对琼北地区水稻土N2O排放的影响

干湿交替会影响土壤硝化和反硝化等N₂O主要的产生过程,频繁的干湿交替在以海南为代表的热带水稻种植地区十分常见.生物炭作为一种土壤改良剂在改良土壤理化性质,减少土壤温室气体排放方面应用广泛,然而当前关于生物炭在琼北地区水稻土频繁干湿交替过程中减排效果研究并未深入.本试验以海南琼北地区典型水稻土为供试土壤,以400℃厌氧条件下炭化的玉米秸秆生物炭为供试生物炭,探究不同水分管理条件下添加生物炭对土壤温室气体排放及微生物相关功能基因的影响.试验设置干湿交替条件下不添加生物炭（AWD1）,干湿交替并添加2%生物炭（AWD2）,干湿交替并添加4%生物炭（AWD3）,持续淹水不添加生物炭（CF1）,持续淹水并添加2%生物炭（CF2）,持续淹水并添加4%生物炭（CF3）共6个处理,进行为期30 d的25℃恒温避光培养.结果表明：①不同水分条件下添加玉米秸秆生物炭均可减少酸性水稻土中N₂O的排放（P<0.05,下同）,AWD3处理N₂O排放总量为0.43 mg·kg^-1,相比AWD1处理减少了68%;②玉米秸秆生物炭在不同水分管理条件下均可以显著提高土壤pH,添加生物炭处理相对于不添加生物炭处理在培养结束后土壤pH平均提高了0.5个单位,同时提高土壤NH₄⁺-N含量,但会导致Eh的降低;③玉米秸秆生物炭的添加显著降低了氨氧化细菌（AOB）丰度,显著提高了nosZ基因丰度,降低了（nirK+nirS）/nosZ的比值,抑制了硝化过程,同时促进了反硝化过程N₂O的还原,从而降低了N₂O排放.结果表明,干湿交替过程添加生物炭有利于减少水稻田土N₂O排放,在琼北地区农业温室气体减排方面有较大的应用前景.     

高效异养硝化-好氧反硝化菌Glutamicibacter sp.WS1低温下对多种氮源的脱氮特性及氮代谢机制

针对污水处理厂冬季生物脱氮效率低、出水水质不达标的问题,从活性污泥中分离出1株耐低温异养硝化-好氧反硝化菌株Glutamicibacter sp.WS1.采用PCR技术扩增该菌株的脱氮功能基因,研究其对不同氮源的低温脱氮效能,通过单因素实验探究环境因子对其低温好氧反硝化性能的影响,并利用氮平衡解析其氮代谢路径.结果表明,菌株WS1含有氮代谢相关的功能基因amoA、napA、nirS和nirK;在15℃低温条件下,菌株WS1在以NH₄⁺-N、NO₃^--N、NO₂^--N+NO₃^--N和NH₄⁺-N+NO₃^--N为氮源时,对各无机氮的去除率分别为100%、98.10%、99.87%+100%和100%+94.92%;菌株WS1的最佳反硝化条件：柠檬酸钠为碳源、C/N为16、pH为8、ρ（DO）为4.5~6.8 mg ·L^-1和温度为30℃;在低温（15℃）和低C/N （10）条件下,菌株WS1对NO₃^--N的去除率达到92.50%;异养硝化-好氧反硝化/好氧反硝化和同化作用是菌株WS1去除不同氮源底物的主要途径,其中大部分的无机氮（47%~56%）通过异养硝化-好氧反硝化/好氧反硝化作用转化为了气态氮.菌株WS1在低温污水脱氮领域具有广阔的应用前景.     

青藏高原高寒湿地春夏两季根际与非根际土壤反硝化速率及nirS型反硝化细菌群落特征分析

反硝化是生态系统氮循环的关键过程.目前对于生态系统氮排放及反硝化细菌群落的研究大多基于人为影响显著的环境,对于人为干扰较低的自然生态系统的研究较少.本研究选取青藏高原黄河源区不同海拔（唐克、久治、玛多和达日）不同季节（春季和夏季）的高寒湿地植物根际与非根际土壤作为研究对象,采用¹⁵N同位素标记法测定反硝化速率,高通量测序技术测定nirS反硝化细菌群落组成及相对丰度,并探究环境因子（气温、海拔）和土壤理化性质（pH、土壤有机碳、铵态氮、硝态氮和亚硝态氮）对nirS型反硝化细菌群落的影响.结果表明,高寒湿地土壤反硝化速率范围为0.80~14.98 nmol·（g·h）^-1,对总N₂释放的贡献率为11.23%~71.16%.唐克、久治和达日的土壤样品,均呈现出根际土壤反硝化速率高于非根际的趋势（P<0.05）.Proteobacteria是青藏高原高寒湿地植物根际和非根际土壤中主要的反硝化细菌门;在属水平上,各土壤样本中相对丰度最高的是一种未分类的变形杆菌（unclassified Proteobacteria,2.86%~29.41%）,这表明主导青藏高原高寒湿地反硝化作用的可能有一些独特的未被鉴定的反硝化菌属,相对丰度其次为假单胞菌属（Pseudomonas,2.45%~26.52%）和贪铜菌属（Cupriavidus,0%~34.14%）.基于距离的冗余分析结果表明,高寒湿地的反硝化细菌群落结构主要受到海拔、pH、NO₂^-含量影响（P<0.05）;相关分析表明反硝化速率和Shannon指数与pH呈显著负相关（P<0.05）,且主要反硝化菌群相对丰度受到温度和pH的影响.本研究结果可为进一步了解青藏高原高寒湿地这一特殊生境中的氮循环提供参考依据.     

添加生物炭对琼北地区双季稻田生物固氮的影响

生物固氮有助于植物对土壤中有效氮的利用,减少农业生态系统中无机氮肥的使用.生物炭可以通过其特殊物理结构调节土壤理化性质,提高土壤微生物的丰度和活性,然而关于生物炭对水稻土生物固氮方面的研究并未深入了解.试验共设置3个处理：施磷钾肥对照（CK）、当地常规施肥处理（CON）和常规处理配施20 t·hm^-2生物炭（B）,采用qPCR和高通量测序分析固氮基因（nifH）的丰度和群落结构变化,探讨生物炭添加对琼北地区双季稻田土壤固氮微生物的影响.结果表明,相比CK和CON处理,添加生物炭提高了土壤pH和土壤有机碳（SOC）含量以及作物产量.同时nifH基因丰度与土壤pH和SOC呈显著正相关.与CK处理相比,添加生物炭处理增加了nifH基因丰度以及显著改变了早稻季土壤固氮微生物的群落结构,常规施肥处理减少了nifH基因丰度而对固氮微生物群落影响相对较小.施用生物炭使固氮微生物群落优势属发生了变化,地杆菌属（Geobacter）、嗜糖假单胞菌属（Pelomonas）、固氮螺菌属（Azospirillum）、厌氧粘细菌属（Anaeromyxobacter）和铁氧化细菌属（Sideroxydans）等是所有处理中的优势菌属.相比CK处理,生物炭处理显著增加了嗜糖假单胞菌属的相对丰度,而常规施肥处理增加了地杆菌属的相对丰度.结果表明,生物炭添加具有一定的减肥潜力,为减少琼北地区稻田氮肥施用,提高氮肥利用率提供了理论依据.     

淮北平原典型农田土壤N2O产生途径及相关功能基因丰度研究

温室气体氧化亚氮（N₂O）已成为全球关注的焦点,全球约60%的人为N₂O排放来自农业土壤.虽然已知微生物硝化和反硝化是土壤N₂O产生的主要过程,但N₂O产生的关键生物学机制以及其调控环境变量之间的相互作用仍然难以预测.本研究选取安徽省亳州市冬、夏两季 农田垂向土壤（0~200 cm）为研究对象,通过乙炔抑制法、¹⁵N-¹⁸O同位素示踪技术分别测定了N₂O产生潜势及产生途径,并利用宏基因组测序技术分析不同N₂O产生途径中功能基因的丰度变化以解析农田土壤N₂O产生的微生物机理.结果显示,在空间尺度上,表层土壤（0~20 cm）是N₂O产生热区,其N₂O产生潜势最高,为（0.364±0.048） ng·g^-1·h^-1.硝化和反硝化潜势均在表层土壤达到最高.在时间尺度上,冬季（15 ℃）是N₂O产生热时,冬季样品N₂O产生潜势显著高于夏季样品,分别为（0.198±0.007）和（0.057±0.009） ng·g^-1·h^-1.总体而言,硝化过程是农田土壤N₂O产生的主要来源,其中,硝化细菌反硝化过程（ND）对N₂O产生的贡献率最高,为52%,而硝化细菌硝化过程（NN）和硝化反应偶联的反硝化过程（NCD）的贡献率分别为24%和0.统计分析表明,农田土壤N₂O产生、硝化及反硝化潜势与理化性质（MC、pH、TN）和功能基因相对丰度（hao、nirK、norB）存在显著相关性.本研究揭示了农田土壤中N₂O的产生机理及关键影响因素,并强调了冬季农田土壤中N₂O的产生不容忽视,这些结果对准确评估我国农业温室气体排放具有重要意义.     

干湿交替对自然沟渠沉积物反硝化速率的影响

以川中丘陵区自然沟渠沉积物为研究对象,设置低强度、中强度、高强度的干湿交替频率和长期淹水对照处理,运用室内原状土柱-乙炔抑制培养法和实时荧光定量PCR技术,研究了干湿交替对自然沟渠沉积物反硝化速率及相关功能基因的影响.结果表明：在试验模拟过程中,干湿交替显著降低了沉积物中NH₄⁺-N和DOC含量,沉积物中NO₃^--N含量则表现为先增加后减少的趋势.沉积物反硝化速率均值表现为中强度（266.42 μg·m^-2·h^-1） > 高强度（199.10 μg·m^-2·h^-1） > 低强度（152.93 μg·m^-2·h^-1） > 长期淹水（9.57 μg·m^-2·h^-1）.干湿交替增加了反硝化功能基因的拷贝数（p<0.05）,nosZ基因拷贝数在实验前后无显著差异;低强度和中强度处理的nirK基因拷贝数在实验前后差异显著,中强度处理的nirS基因拷贝数在实验前后差异显著.Pearson相关分析结果表明,沉积物的反硝化速率与NO₃^--N含量、ORP和nirK基因拷贝数呈显著正相关（p<0.05）.干湿交替可能主要通过改变沉积物的NO₃^--N含量、ORP和nirK基因拷贝数影响沉积物反硝化速率.     

异养硝化细菌Acinetobacter junii WZ17的脱氮特性及动力学研究

异养硝化-好氧反硝化细菌Acinetobacter junii WZ17脱氮效果良好,为确定其脱氮特性及动力学过程,利用“样条插值法”研究了菌株生长阶段,并采用Logistic模型和修正的Gompertz模型对菌株生长及氮素去除过程进行拟合,结合反硝化过程中间产物,分析菌株脱氮途径.结果显示,菌株WZ17以NH₄⁺-N、NO₃^--N和NO₂^--N唯一氮源时,生长适应期分别为2.89、3.13和3.13 h,最大去除速率分别为8.47、5.76和5.18 mg·L^-1·h^-1,生长和底物去除过程分别符合Logistic模型（R²>0.9）和修正的Gompertz模型（R²>0.9）.硝化过程中,NO₃^--N和NO₂^--N的积累量仅为0.13和0.14 mg·L^-1,反硝化过程中,NO₂^--N的积累量为1.55 mg·L^-1.“样条插值法”的运用可以准确地划分菌株WZ17的生长阶段,菌株WZ17对NH₄⁺-N、NO₃^--N和NO₂^--N均具有较好的去除效果,反硝化途径为NO₃^--N→NO₂^--N→N_xO_y.     

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.     

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.     

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.     

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.     

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.