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.     

太湖春夏两季反硝化与厌氧氨氧化速率的空间差异及其影响因素

反硝化和厌氧氨氧化是湖泊的重要脱氮过程,对维持湖泊氮素平衡具有重要意义.为了解大型富营养化浅水湖泊——太湖反硝化和厌氧氨氧化速率的时空变化及其影响因素,于2020年春季和夏季选择太湖的梅梁湾、贡湖湾、竺山湾、大浦口、胥口湾和湖心区采集无扰动泥柱,利用¹⁵N同位素示踪技术,在恒温水浴条件下开展反硝化和厌氧氨氧化流动培养实验.结果表明,春季太湖不同湖区反硝化和厌氧氨氧化速率的空间分布差异较大,反硝化速率为（27.74±8.45）~（142.43±35.54）μmol·（m²·h）^-1,厌氧氨氧化速率为（2.35±1.06）~（17.95±8.66）μmol·（m²·h）^-1,厌氧氨氧化对脱氮的贡献率相对较低,为（7.82±1.71）%~（11.20±1.53）%.夏季竺山湾脱氮速率最高,反硝化和厌氧氨氧化速率分别高达（165.68±62.14）μmol·（m²·h）^-1和（33.56±10.66）μmol·（m²·h）^-1,厌氧氨氧化对脱氮贡献率达到了（16.85±1.78）%,其他湖区的脱氮速率相对较低,且没有十分显著的空间差异,反硝化和厌氧氨氧化速率分别为（25.47±10.46）~（42.50±16.46）和（2.65±0.94）~（5.95±2.65）μmol·（m²·h）^-1,厌氧氨氧化对脱氮的贡献率为（13.62±1.95）%~（7.24±1.78）%.总体来说,夏季反硝化速率要普遍低于春季,而厌氧氨氧化速率相对于春季并无明显下降.统计分析表明,反硝化和厌氧氨氧化速率与底物氮浓度呈显著的相关性（P<0.01）,说明氮浓度是不同湖区脱氮速率差异的主要控制因素.此外,厌氧氨氧化对脱氮的贡献率与叶绿素a的浓度呈现显著的正相关性（P<0.05）,说明蓝藻水华对厌氧氨氧化脱氮贡献率的变化有很大的影响,具体的影响机制还有待进一步研究.     

外源碳和氮输入对降水变化下土壤呼吸的短期影响

利用野外原位小区控制试验,模拟研究了降水变化下草地生态系统土壤呼吸对外源碳和氮输入的响应.在2014年,以内蒙古锡林河流域温带典型草原为研究对象,测定了增加降水处理（CK）、增加降水配施氮肥处理[CN,2.5 g·（m²·a）^-1]、增加降水配施碳源处理[CG,24 g·（m²·a）^-1]和增加降水配施氮肥和碳源处理[CNG,2.5 g·（m²·a）^-1+24 g·（m²·a）^-1]下土壤呼吸的变化,并分析了土壤呼吸与土壤温度、土壤水分、土壤可溶性有机碳（DOC）、土壤微生物量碳（MBC）之间的关系.结果表明,在自然降水较多的第一次增加降水（FWE）阶段,CG处理和CNG处理168 h土壤CO₂累积通量显著增加,而CN处理168 h土壤CO₂累积通量无显著变化,并且CG处理和CNG处理土壤MBC含量显著高于CK处理和CN处理,同时,该阶段平均CO₂释放速率与土壤MBC含量正相关（P<0.05）.与FWE阶段相比,无自然降水的第二次增加降水（SWE）阶段各处理168 h土壤CO₂累积释放量显著降低,并且各处理MBC含量也显著降低（P<0.05）,仅有土壤DOC含量显著增加（P<0.05）,CG处理和CN处理168 h土壤CO₂累积通量显著降低（P<0.05）.两个降水阶段土壤呼吸速率与土壤温度或土壤体积含水量均有显著的正相关性（P<0.05）.因此,自然降水的分布对土壤水分的影响调控着外源氮和碳对半干旱草地生态系统土壤呼吸的作用效应.     

城市草坪温室气体排放特征及影响因素

草坪作为城市绿地的重要组成部分，其温室气体的吸收或排放不容忽视.然而当前对亚热带城市草坪温室气体通量的研究相对匮乏.采用静态箱-气相色谱法，对杭州市城区典型城市草坪的多种温室气体（CO₂、CH₄、N₂O和CO）地气交换通量进行了连续观测研究.结果表明，城市草坪的温室气体月平均通量变化明显，而其日变化特征并不明显.城市草地和土壤（无植被生长的裸土）是大气N₂O的源，平均通量分别为（0.66±0.17）μg·（m²·min）^-1和（0.58±0.20）μg·（m²·min）^-1；是CH₄和CO的汇，其中CH₄平均通量分别为（-0.21±0.078）μg·（m²·min）^-1和（-0.26±0.10）μg·（m²·min）^-1，CO分别为（-6.36±1.28）μg·（m²·min）^-1和（-6.55±1.69）μg·（m²·min）^-1.城市草地和土壤CO₂平均通量分别为（5.28±0.75） mg·（m²·min）^-1和（4.83±0.91） mg·（m²·min）^-1.基于相关性分析研究发现，草地和土壤的CO₂和N₂O通量均与降水量呈显著的负相关，而CH₄和CO通量与降水量呈显著的正相关；除草地CH₄通量与土壤温度无显著相关、草地N₂O通量与土壤温度呈显著负相关外，其余各温室气体通量与土壤温度均呈显著正相关.另外，城市草坪的草地和土壤CO₂（R²为0.371和0.314）和N₂O （R²为0.371和0.284）通量季节变化受降水量的影响要大于其它温室气体，而土壤温度对CO通量的影响（R²为0.290和0.234）要显著于其它温室气体.     

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.     

短期氮磷添加对祁连山亚高山草地土壤呼吸组分的影响

为探究短期氮磷添加对祁连山亚高山草地土壤呼吸及其组分的影响,于2019年6~8月采用随机区组设计,设置氮添加［10 g ·（m² ·a）^-1,N］、磷添加［5 g ·（m² ·a）^-1,P］、氮磷混施［10 g ·（m² ·a）^-1N、5 g ·（m² ·a）^-1P,NP］、对照（CK）和完全对照（CK''）这5个处理,测定了土壤总呼吸速率及其组分.结果表明,氮添加对土壤总呼吸和异养呼吸的降低速率均低于磷添加［-16.71% vs.（相对照,下同）-19.20%;-4.41% vs.-13.05%］,但对自养呼吸的降低速率高于磷添加（-25.03% vs.-23.36%）,而氮磷混施则对土壤总呼吸速率无显著影响.土壤总呼吸速率及其组分与土壤温度均呈显著的指数相关,其中氮添加降低了呼吸速率的温度敏感性（Q₁₀：-5.64%~0.00%）,而磷添加增加了Q₁₀（3.38%~6.98%）,氮磷混施降低了自养呼吸速率但增加了异养呼吸速率的Q₁₀（16.86%）,从而降低了土壤总呼吸速率的Q₁₀（-2.63%~-2.02%）.土壤pH、土壤全氮和根系磷含量与自养呼吸速率均具有显著相关性（P<0.05）,而与异养呼吸速率无显著相关,且根系氮含量只与异养呼吸速率呈显著负相关（P<0.05）.总体上,自养呼吸速率对氮添加更加敏感,而异养呼吸速率对磷添加更加敏感,氮或磷添加均显著降低了土壤总呼吸速率,而氮磷混施并未显著影响土壤总呼吸速率,此结果可为准确评估亚高山草地土壤碳排放提供科学依据.     

不同水分条件下土地利用方式对我国热带地区土壤硝化过程及NO和N2O排放的影响

热带地区雨热条件丰富,硝化过程产生的硝态氮不利于氮素养分的保持,同时会带来氮氧化物排放等环境负面效应.橡胶树和茶树在热带地区广泛种植,不同土地利用方式土壤硝化速率和氮氧化物排放的差异尚不清楚.以海南白沙地区典型橡胶林和茶园土壤为研究对象,分别采集5 a （T5）和15 a （T15）茶园土壤和附近橡胶林（XJ）土壤,设置低（50% WFPS-L）和高（80% WFPS-H）两种不同水分含量,在25℃进行71d室内培养试验,探究不同土地利用方式和不同水分含量对土壤净硝化速率、NO和N₂O排放的影响.结果表明：①橡胶林改为茶园后,在高含水量条件下,显著降低了土壤净硝化速率、NO和N₂O排放,整体呈现XJH>T15H>T5H的趋势,XJH处理土壤净硝化速率、NO和N₂O排放分别高达4.2 mg ·（kg ·d）^-1、1.4 mg ·kg^-1和14.3 mg ·kg^-1（以N计）;在低含水量条件下,茶园土壤显著降低了土壤NO排放,N₂O排放在各土壤间差异不显著,净硝化速率在XJ和T15处理之间无显著差异;土壤NO排放和净硝化速率呈极显著正相关（P<0.01）.②XJH净硝化速率高于XJL,茶园土壤呈相反趋势;XJ和T15的NO排放对水分的响应和净硝化速率趋势一致,高硝化速率促进NO排放,而T5处理NO排放受含水量影响不显著;相比低含水量处理,高含水量各处理显著促进N₂O排放.结果表明,土壤有机质（SOM）、全氮（TN）、pH和含水量是影响土壤净硝化速率、NO和N₂O排放的关键因子,高含水量条件下橡胶林转为茶园的种植模式显著降低了土壤净硝化速率和对环境的负面影响.     

贵阳市花溪城区大气PM2.5中碳质气溶胶的变化特征及来源解析

碳质气溶胶作为大气气溶胶的重要组成部分,对大气环境质量、人类健康及全球气候变化有着重要的影响.为探究贵阳市花溪城区大气细颗粒物（PM_2.5）中碳质气溶胶的变化特征及来源,于2020年不同季节开展大气PM_2.5原位观测研究,利用热/光学碳分析仪（DRI Model 2015）测定大气PM_2.5的碳质组分.结果表明,观测期间大气ρ（PM_2.5）、ρ[总碳质气溶胶（TCA）]、ρ[有机碳（OC）]、ρ[二次有机碳（SOC）]和ρ[元素碳（EC）]的平均值分别为：（39.7±22.3）、（14.1±7.2）、（7.6±3.9）、（4.4±2.6）和（2.0±1.0）μg·m^-3,OC/EC的平均值为（3.9±0.8）.ρ（PM_2.5）、ρ（TCA）、ρ（OC）、ρ（SOC）和ρ（EC）呈现冬季最高[（52.6±28.6）、（17.0±9.6）、（9.1±5.2）、（6.1±3.9）和（2.4±1.2）μg·m^-3],夏季最低[（25.1±7.1）、（11.6±3.6）、（6.3±1.9）、（3.7±1.2）和（1.6±0.6）μg·m^-3]的季节变化特征.OC/EC季节变化呈现：夏季（4.2±0.8）>冬季（3.8±0.9）>秋季（3.8±0.5）>春季（3.7±0.9）,表明花溪城区各季节均存在SOC生成.SOC与OC呈现显著相关（R²=0.9）,且随着大气氧化性增强,SOC浓度呈增加趋势.OC与EC各季节均呈现较好相关性,其中秋季最高（R²=0.9）,其他3个季节偏低（R²为0.74~0.75）,表明二者具有共同来源.通过OC/EC值范围初步判断碳质气溶胶来源于机动车尾气排放、燃煤排放和生物质燃烧排放.为了进一步定量解析主要排放源对碳质气溶胶的贡献,利用PMF模型对碳质气溶胶来源解析,结果表明贵阳市花溪城区碳质气溶胶主要来源为燃煤源（29.3%）、机动车排放源（21.5%）和生物质燃烧源（49.2%）.     

玉米芯和稻草秸秆强化潜流人工湿地对低C/N污水的处理效果

人工湿地在处理低C/N污水时存在碳源缺乏而严重限制反硝化进行的问题.为了补充反硝化需要的碳源,选择了玉米芯和稻草秸秆作为外加碳源引入湿地系统,对比两种碳源对湿地脱氮的强化效果.结果表明,通过11 d的纯水浸提释放实验发现,碳素累积释放量：稻草秸秆［（145.17±9.44） mg·g^-1］>玉米芯［（57.41±5.04） mg·g^-1］;氮素累积释放量：稻草秸秆［（2.31±0.09） mg·g^-1］>玉米芯［（0.66±0.08） mg·g^-1］.在观测的时间内,玉米芯和稻草秸秆累积释放碳氮比平均值分别为94.78和63.64.相比于稻草秸秆,玉米芯更适合作为外加碳源.在为期58 d的潜流人工湿地实验中,发现除了第8~12 d,添加玉米芯和稻草秸秆人工湿地出水中ρ（COD）超过50 mg·L^-1外,其它时间都低于50 mg·L^-1.在观测期间,添加玉米芯人工湿地的NO₃^--N去除率为93%~99%,具有良好的反硝化性能.而添加稻草秸秆人工湿地在运行后期NO₃^--N去除率最低只有76.8%,反硝化速率明显下降.对照组NO₃^--N去除率只有76.2%~77.7%,出现了明显碳源不足的现象.碳源不足还造成了NO₂^--N的蓄积.添加稻草秸秆和对照组人工湿地中NO₂^--N的出水质量浓度分别是玉米芯人工湿地的2.5~6倍和6~26倍.与添加稻草秸秆比,添加玉米芯可以使人工湿地中NO₂^--N出水质量浓度得到更显著地降低（P<0.05）.玉米芯、稻草秸秆和对照组人工湿地TN去除率分别为83.75%~93.49%、76.59%~78.85%和67.85%~72.56%,三者之间存在显著性差异（P<0.01）.最后,通过对玉米芯进行了稀碱加热预处理,使玉米芯的碳素累积释放量提高到（93.73±17.49） mg·g^-1,累积释放的碳氮比提高至175.8,进一步提高了玉米芯的释碳性能,表现为更合适的外加碳源.     

张掖市城区大气细颗粒物PM2.5的化学组成及来源解析

为研究张掖市城区大气细颗粒物（PM_2.5）的污染特征和来源,于2020年9月至2021年7月在张掖市城区的河西学院和湿地博物馆2个采样点进行了PM_2.5样品采集,对PM_2.5浓度、化学组成（水溶性无机离子、碳质组分和元素）和来源进行分析.结果表明,河西学院和湿地博物馆两个采样点的年均ρ（PM_2.5）分别为（73.7±31.8）μg·m^-3和（68.1±33.3）μg·m^-3,季节浓度均值均呈现春季>冬季>秋季>夏季的变化.河西学院采样点的二次水溶性无机离子（SO₄^2-、NO₃^-和NH₄⁺）年均值高于湿地博物馆.河西学院采样点的ρ（OC）和ρ（EC）分别为（9.6±5.7）μg·m^-3和（2.9±1.6）μg·m^-3,湿地博物馆采样点的年均ρ（OC）和ρ（EC）分别为（9.2±5.8）μg·m^-3和（2.5±1.3）μg·m^-3,河西学院的含碳组分在各季节均高于湿地博物馆.河西学院和湿地博物馆两个采样点的年均二次有机碳（SOC）在OC中的质量分数分别为49.4%和43.7%,表明张掖市存在较为严重的二次污染.河西学院和湿地博物馆两个采样点的元素浓度年均值分别为（6.0±3.5）μg·m^-3和（5.8±3.9）μg·m^-3,受到人为源的影响,Zn、Ca、Al和Fe等元素浓度水平相对较高.正定矩阵因子分解模型（PMF）结果表明,张掖城区PM_2.5的主要贡献源为二次气溶胶（28.0%）、交通源（25.8%）、扬尘源（15.2%）、燃煤源（14.0%）、生物质燃烧和垃圾焚烧源（12.5%）和工艺过程源（4.5%）.     

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.     

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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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.     

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.     

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.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

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.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.