COVID-19疫情期间北京市两次重霾污染过程大气污染物演变特征及潜在源区分析

新冠肺炎疫情（COVID-19）期间,执行了严格居家隔离措施,人为排放源急剧降低,但北京仍出现了两次持续重霾污染过程.本研究使用北京市大气污染物、气溶胶数浓度和气象要素数据,结合气团轨迹模式（HYSPLIT）,计算了潜在源贡献因子（PSCF）和浓度权重轨迹（CWT）,分析了两次重霾污染过程中大气污染物的演变特征及其潜在源区贡献.结果表明,COVID-19期间居家隔离措施对PM_2.5和黑碳（BC）的日变化特征影响较大,对CO、NO₂、SO₂和O₃的日变化影响较小.两次重霾污染过程首要污染物均是PM_2.5,污染过程1主要是以局地污染为主,污染过程2以局地污染和外来输送为主.不同过程下气溶胶数浓度谱分布均为单峰型分布,峰值位于0.3 μm,在污染过程中主要是0.2~0.5 μm粒径气溶胶数浓度增加,是干净日的3.3~13.6倍.不同过程中BC_liquid对BC的贡献为64.8%~85.1%.BC_liquid的浓度为：污染过程2（5.04 μg ·m^-3）>污染过程1（3.20 μg ·m^-3）>干净日（疫情前,2.31 μg ·m^-3）>干净日（疫情,0.76 μg ·m^-3）.不同过程中PM_2.5和BC的PSCF和CWT分布特征不同.PM_2.5的PSCF高值区在干净日（疫情前）和干净日（疫情）主要分布在北京的西南方和西部,权重浓度超过30 μg ·m^-3;在污染过程1和污染过程2主要分布在北京及其周边地区和西南部,权重浓度均超过90 μg ·m^-3.BC的PSCF高值区在干净日（疫情前）、干净日（疫情）和污染过程1主要分布在北京及其周边地区,权重浓度分别超过2.4、0.9和4.5 μg ·m^-3;在污染过程2中分布在北京西南部,权重浓度超过5μg ·m^-3.     

承德市PM2.5中碳质组分的季节分布特征及来源解析

为研究承德市PM_2.5中碳质组分的季节变化及污染来源,于2019年1、4、7和10月采集大气PM_2.5样品,测定碳质组分浓度.通过有机碳（OC）与元素碳（EC）比值、总碳质气溶胶（TCA）及二次有机碳（SOC）的估算,分析碳质组分的变化特征;结合后向轨迹和主成分分析（PCA）方法,分析污染来源.结果表明,采样期间PM_2.5、OC和EC的平均质量浓度分别为（31.26±21.39）、（13.27±8.68）和（2.80±1.95）μg ·m^-3.PM_2.5的季节变化趋势为：冬季[（47.68±30.37）μg ·m^-3]>秋季[（28.72±17.12）μg ·m^-3]>春季[（26.59±15.32）μg ·m^-3]>夏季[（23.17±8.38）μg ·m^-3],与总碳（TC）、OC和EC季节变化趋势一致,冬季（R²=0.85）的OC与EC来源较一致;OC/EC值得出4个季节均受到交通和燃煤源排放的影响,且冬季受烟煤排放影响显著.TCA的平均浓度为（21.38±13.68）μg ·m^-3,占PM_2.5比例达68.39%,二次转化率（SOC/OC）为：春季（54.09%）>秋季（37.64%）>夏季（32.91%）>冬季（25.43%）.后向轨迹模拟结果表明,春季和夏季气团携带的污染物浓度相对较低,秋季污染物的传输通道为西南方向,冬季为西北方向,主成分分析（PCA）表明,承德市PM_2.5削减的关键是控制机动车尾气、燃煤和生物质燃烧源的排放.     

2017~2018年北京大气PM2.5中水溶性无机离子特征

为探究近年来北京市空气质量持续改善过程中PM_2.5及其中水溶性无机离子（WSIIs）特征,于2017~2018年在北京城区进行了连续1 a的PM_2.5样品采集,对其中9种主要WSIIs进行了全面分析.结果表明,北京市PM_2.5年均浓度为（77.1±52.1）μg ·m^-3,最高和最低值分别出现在春季[（102.9±69.1）μg ·m^-3]和夏季[（54.7±19.9）μg ·m^-3].WSIIs年均浓度为（31.7±30.1）μg ·m^-3,对PM_2.5贡献比例为41.1%,季节贡献特征为：秋季（45.9%） > 夏季（41.9%） > 春季（39.9%） ≥ 冬季（39.2%）.SNA是WSIIs的重要组成,春、夏、秋和冬季在总WSIIs中的占比分别可达86.0%、89.5%、74.6%和73.0%.随温度升高,NO₃^-和SO₄^2-分别呈现出了先升高后降低以及波动性升高的趋势;而当相对湿度低于90%时,2种离子浓度均随相对湿度增加而升高,反映了光化学和液相过程对2种离子组分的贡献差异.随污染加重,WSIIs整体贡献比例大幅升高,且各类WSIIs演化特征各异,其中,NO₃^-浓度和贡献均持续升高,而SO₄^2-和各类源自扬尘的离子组分（Mg²⁺、Ca²⁺和Na⁺）贡献降低.观测期间WSIIs主要来源包括二次转化、燃烧源和扬尘源,对燃煤和机动车的管控是其减排的重要途径.后向轨迹分析表明,源自北京市南部和西部的气团对应着较高的PM_2.5浓度和WSIIs占比,且二次离子贡献显著;而源自西北和北部的气团对应的PM_2.5浓度和WSIIs占比则较低,但Ca²⁺贡献较高.     

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%）.     

天津市2020年冬季重污染过程气溶胶消光特性及其来源

为了解天津市2020年冬季重污染过程气溶胶消光特征,基于2020年1~2月高时间分辨率的在线监测数据,对1月16~18日（重污染过程Ⅰ）、1月26~28日（重污染过程Ⅱ）和2月9~10日（重污染过程Ⅲ）进行气溶胶消光特性及其来源分析.结果表明,3次重污染过程PM_2.5平均浓度分别为（229±52）、（219±48）和（161±25）μg·m^-3,NO₃^-、SO₄^2-、NH₄⁺、OC、EC、Cl^-和K⁺为PM_2.5中主要组分.3次重污染过程气溶胶散射系数（Bsp₅₅₀）和吸收系数（Bap₅₅₀）分别为（1055.65±250.17）、（1054.26±263.22）、（704.44±109.89） Mm^-1和（52.96±13.15）、（39.72±8.21）、（34.50±8.53） Mm^-1,散射效应高于吸收效应.重污染天气下硝酸盐（38.9%~48.8%）、硫酸盐（31.1%~40.7%）和OM （9.9%~21.8%）为PM_2.5中最主要消光成分.3次重污染过程PM_2.5组分对气溶胶消光的贡献发生明显变化,重污染过程Ⅰ,硝酸盐对消光系数的贡献最高;重污染过程Ⅱ,受春节期间烟花爆竹燃放影响,OM对消光系数的贡献升高;重污染过程Ⅲ,交通出行减少但燃煤源排放相对稳定,硝酸盐对消光系数的贡献降低,硫酸盐的贡献升高.来源解析结果显示,重污染天气气溶胶消光的主要来源为二次无机气溶胶（37.1%~42.0%）、燃煤和工业（22.9%~24.2%）、机动车（23.9%~27.2%）、扬尘源（5.0%~6.4%）和烟花爆竹及生物质燃烧排放（3.9%~6.2%）.与重污染过程Ⅰ相比,重污染过程Ⅱ烟花爆竹及生物质燃烧排放对消光系数的贡献升高;重污染过程Ⅲ机动车对消光系数的贡献明显降低;燃煤和工业对消光系数的贡献在3次重污染过程中较接近.后轨迹分析表明,重污染天气期间天津市主要以来自河北的小尺度、短距离以及内蒙古中部的中尺度、中短距离气团传输轨迹为主.     

北京南部城区PM2.5中碳质组分特征

为了解《大气污染防治行动计划》实施后北京市大气PM_2.5中碳质组分特征,于2017年12月至2018年12月在北京污染较重的南部城区进行了PM_2.5连续采样,对其中的有机碳（OC）和元素碳（EC）进行了全面研究.结果表明,北京大气PM_2.5、OC和EC浓度变化范围分别为4.2~366.3、0.9~74.5和0.0~5.5 μg ·m^-3,平均浓度分别为（77.1±52.1）、（11.2±7.8）和（1.2±0.8）μg ·m^-3,碳质组分（OC和EC）整体占PM_2.5的16.1%.OC质量浓度季节特征表现为：冬季[（13.8±8.7）μg ·m^-3] > 春季[（12.7±9.6）μg ·m^-3] > 秋季[（11.8±6.2）μg ·m^-3] > 夏季[（6.5±2.1）μg ·m^-3],EC四季质量浓度水平均较低,范围为0.8~1.5 μg ·m^-3.二次有机碳（SOC）年均质量浓度为（5.4±5.8）μg ·m^-3,四季贡献比例范围为45.7%~52.3%,年均贡献为48.2%,凸显了二次形成的重要贡献.随污染加重,尽管OC和EC贡献比例均降低,但浓度水平却成倍升高,OC和EC浓度在严重污染天分别是空气质量为优天的6.3和3.2倍.与非供暖时段相比,供暖时段PM_2.5、OC和SOC浓度分别增加了14.4%、47.9%和72.1%,体现了OC对供暖季PM_2.5污染的重要贡献.PSCF分析表明,位于北京西南的山西省和河南省部分区域是PM_2.5和OC的主要潜在源区,且PM_2.5潜在源区更为集中;EC的PSCF高值（>0.7）区域较少,主要位于北京南部,如山东省和河南省部分地区,且北京市及周边地区贡献明显.     

石家庄市采暖季PM2.5碳组分昼夜污染特征及来源分析

为探究2017年石家庄市采暖季昼夜PM_2.5中碳组分的污染及来源特征,选取2017年11月30日-2018年1月22日时间段分别采集石家庄白天（8：00-20：00）、夜晚（20：00-翌日8：00）的PM_2.5样品,分析PM_2.5组分中OC和EC昼夜间的浓度变化特征、来源特性,SOC的估算及影响因素,并对石家庄市碳质气溶胶进行源解析和区域传输分析.结果表明,①采样期间白天PM_2.5、OC和EC的平均质量浓度分别为（110.6±71.6）、（39.9±20.4）和（9.3±3.6）μg·m^-3,夜间平均质量浓度分别为（128.5±75.3）、（64.7±36.5）和（13.6±6.0）μg·m^-3,PM_2.5、OC和EC质量浓度均呈现出夜间质量浓度高于白天的特征.②燃煤和机动车尾气排放在增加了一次有机碳（POC）和元素碳（EC）的本底质量浓度的同时,产生的CO、NO₂、SO₂等气体污染物又促进了光化学反应,两者协同作用下促进了SOC质量浓度的生成和积累.根据估算,SOC、SOC/OC值在夜间高于白天,白天较强的太阳辐射和光化学活性是SOC转化的主导因素,夜间气态有机前体物浓度是SOC转化的主导因素.③采样期间昼夜间OC、EC的相关性较好,其来源具有较好的同源性.大气PM_2.5碳质气溶胶主要来自燃煤、汽油车和柴油车尾气排放混合源,夜间柴油车污染源对碳质气溶胶的贡献率较白天更为明显.④后向轨迹结果表明,石家庄市严重污染期间颗粒污染物浓度变化主要受到低空东北方向气团的影响,PM_2.5以及OC、EC质量浓度的变化和周边地区的污染物输送有关.     

2016年10～11月期间北京市大气颗粒物污染特征与传输规律

本研究采用气溶胶化学组分在线监测仪（ACSM）对北京地区2016年10月15日~11月15日期间非难熔性PM₁（NR-PM₁）化学组分进行实时连续在线观测,探讨了NR-PM₁化学组分的演变特征;运用潜在源贡献分析（PSCF）法和气象-空气质量模式（WRF-CAMx）识别了北京PM_2.5潜在污染源区和传输路径,揭示了PM_2.5净传输通量的垂直分布特征.结果表明,北京秋季NR-PM₁和PM_2.5质量浓度分别为（59.16±57.05）μg·m^-3和（89.82±66.66）μg·m^-3,其中NR-PM₁平均占PM_2.5的（70.31±22.28）%.整个观测期间,有机物（Org）、硝酸盐（NO₃^-）、硫酸盐（SO₄^2-）、铵盐（NH₄⁺）和氯化物（Chl）分别占NR-PM₁总质量浓度的（42.75±11.35）%、（21.27±7.72）%、（19.11±7.08）%、（12.19±2.64）%和（4.68±3.24）%,不同化学组分的日变化特征存在明显差异.对北京秋季NR-PM₁污染影响较大的潜在源区主要集中在河北南部、河南东北部及山东西部,重污染期间保定、北京南部及廊坊等城市对NR-PM₁贡献较大.WRF-CAMx模拟结果表明,PM_2.5总的净传输通量呈现出显著的垂直分布特征.整个观测期间,毗邻城市主要向北京输入PM_2.5,净通量最大出现在海拔600~1000 m;而重污染前期外来源输送PM_2.5主要位于高空,直到污染最严重的11月5日,PM_2.5转为近地面传输,说明高空和近地面传输是影响北京秋季PM_2.5重污染形成的重要因素.同时鉴别出了两种传输路径,即西南-东北方向（保定→北京→承德）和西北-东南方向（张家口→北京→廊坊北→天津）.     

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%）.     

2013~2021年邢台PM2.5重污染过程输送和增长特性

利用河北邢台2013~2021年的PM_2.5、气象要素和模拟资料,着重针对重度及以上污染过程（SAAP）中PM_2.5增长速率、来源及其与大气环流和风场的关联性进行分析.结果表明,2013~2021年邢台共发生PM_2.5污染过程164次,SAAP 103次.地面环流中倒槽型出现概率较低,但出现污染概率最高（61.1%）,其次为高压控制型;500 hPa为平直西风带控制时重度及以上污染概率最高（20.7%）,槽后型次之（16.1%）.SAAP中PM_2.5小时变化率（ΔPM_2.5）主要在±150 μg ·（m³ ·h）^-1,PM_2.5小时变化率为正（+ΔPM_2.5）贡献约61.7%,其中暴发增长占比约13.9%.北偏东风为与重度及以上污染关联最为紧密的风向.中等风速条件下SAAP中ΔPM_2.5平均值大多低于静小风,但东偏北和南偏西部分风向区间中,中等风速ΔPM_2.5平均值显著高于静小风（与污染传输有关）;较大风速对ΔPM_2.5影响复杂.后向轨迹表明,SAAP中缓慢、快速和暴发增长的后向轨迹可分为北偏西、北偏东和偏南3个主要路径,随增长速度加快,北偏西气团来向占比增大.缓慢增长气团相对湿度（RH）较大（80%以上RH>50%）,快速增长气团RH分布较集中（主要为35%~55%）,暴发增长中的低RH （RH<50%）气团占比明显增加（约63%）.模拟表明SAAP可分为本地累积、北部偏东输送、北部偏西输送、混合输送型和偏南输送这5类,其中混合输送型占比最高,其次为北部偏西输送型.偏南输送、本地累积和北部偏东输送型中出现概率最高的高低空配置均为高空槽后配合地面均压场;北部偏西输送型中地面高压配合高空槽后出现概率最高;混合输送中多种环流配比相对均衡.     

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.