土地利用对洱海罗时江小流域土壤微塑料污染的影响

土壤环境中微塑料污染受到广泛关注,但小流域尺度下不同土地利用方式对微塑料污染影响的认识相对不足.以洱海北部罗时江小流域为研究对象,分析耕地、河岸带、草地和林地土壤中微塑料污染特征,利用聚合物风险指数法评估4种地类土壤的污染风险,探讨土地利用对土壤微塑料污染的影响.结果表明：①罗时江小流域土壤微塑料丰度在220~1 900 n·kg^-1之间,平均丰度为（711 ± 55）n·kg^-1,主要聚合物类型为聚酯（PES,32.52%）和聚对苯二甲酸乙二醇酯（PET,21.95%）,粒径集中于0.5~2 mm（61.89%）,超过75%的微塑料为纤维状,颜色以透明为主（58.50%）.②小流域土地利用方式决定土壤微塑料的丰度和污染特征,人类活动强度更大的耕地[（885 ± 95）n·kg^-1]和河岸带[（837 ± 155）n·kg^-1]土壤微塑料丰度显著高于林地[（491 ± 53）n·kg^-1]（P<0.05）,薄膜和碎片状微塑料主要赋存于耕地土壤,微塑料聚合物类型和颜色种类也以耕地土壤最为丰富.③耕地土壤微塑料风险指数等级（Ⅲ级）高于其余3种地类（Ⅰ级）.研究表明,小流域内人类活动强度越大的土地利用方式,其土壤微塑料赋存特征越复杂,聚合物类型更丰富,潜在污染风险越高,应加强对耕地土壤微塑料污染的管控.     

玛瑙河多环境介质和铜锈环棱螺体内微塑料的赋存特征

微塑料污染对水生态系统及人类健康危害大,为探究微塑料在不同环境介质中的赋存特征,选择长江一级支流玛瑙河为研究区域,通过现场采样、显微镜观察和傅里叶红外光谱测定等,对玛瑙河表层水体、沉积物、河岸带土壤和底栖动物铜锈环棱螺中微塑料的丰度、粒径、形状、颜色和组成类型进行了分析.结果表明,玛瑙河表层水体的微塑料平均丰度为（5.9±0.26）n·L^-1;上层沉积物中微塑料丰度（以干重计）为（1.35±0.1）n·g^-1,下层沉积物中微塑料丰度（以干重计）为（0.93±0.12）n·g^-1;近河岸带土壤中微塑料丰度（以干重计）为（0.68±0.16）n·g^-1,远河岸带土壤中微塑料丰度（以干重计）为（0.69±0.14）n·g^-1;铜锈环棱螺体内微塑料丰度为（2.06±0.25）n·g^-1.分析发现,上层沉积物和下层沉积物中微塑料丰度呈正相关;铜锈环棱螺体内微塑料丰度分别与上、下层沉积物中微塑料丰度呈正相关;近、远河岸带土壤中微塑料丰度具有相关性.各环境介质和铜锈环棱螺体内微塑料粒径大多<0.1mm,主要形态为纤维状和碎片状,颜色以蓝色和黑色为主,成分主要是聚丙烯（PP）和聚乙烯（PE）.研究发现,河岸带土壤中微塑料主要来源于农用塑料薄膜的破碎和分解.通过多环境介质调查和铜锈环棱螺体内微塑料的分析,探明了大型底栖动物体内微塑料的累积效应,可为全面了解微塑料潜在生态风险提供依据.     

汾河沿岸农田土壤微塑料分布特征及成因解析

考察了汾河沿岸农田土壤中小于1 mm的微塑料分布特征及赋存因素.采用传统密度离心法对农田土壤中微塑料进行分离提取,使用体式显微镜观察了微塑料数量和类别等特征,采用扫描电镜-能谱仪（SEM-EDS）表征微塑料的微观形貌,采用傅里叶变换红外光谱仪（FTIR）对微塑料进行成分鉴定.结果表明汾河沿岸农田土壤中微塑料平均丰度为290.5 n·kg^-1,微塑料包括纤维类、薄膜类、碎片类和发泡类.其中,纤维类微塑料丰度最高,占总量的52.67%,主要成分为聚乙烯.薄膜类和碎片类主要成分为聚丙烯.发泡类成分为聚苯乙烯.汾河沿岸土壤中微塑料丰度整体呈现出下游>中游>上游的趋势.汾河下游段沿岸土壤微塑料丰度高达500.0 n·kg^-1,约是其上游段和中游段微塑料丰度的两倍.随机森林模型分析结果显示,汾河沿岸农田土壤中微塑料的来源与农膜使用量、人口数量、国内生产总值（GDP）和工业生产等密切相关.其中,农用薄膜使用是造成沿河农田土壤中微塑料赋存的最重要影响因素.     

覆膜年限和有机肥施用对花生田耕层土壤微塑料赋存特征的影响

地膜和有机肥料的大量投入已导致我国农田土壤微塑料污染日趋严重.为研究调查山东德州花生农田微塑料污染状况,分析了该区域不同覆膜年限（0、3、5和8 a）和有机肥施用对农田土壤中微塑料的丰度、粒径、颜色和形状等赋存特征的影响.结果表明,覆膜0、3、5和8 a后花生耕层土壤微塑料丰度的平均值分别为65.33、316.00、1 098.67和1 346.34 n·kg^-1.随着土层深度的增加微塑料丰度降低,0～10、10～20和20～30 cm耕层中的土壤微塑料丰度分别为1 076.00、603.50和440.25 n·kg^-1,并且增加覆膜年限和施加有机肥都显著增加了微塑料的丰度（P<0.05）.粒径<1 mm微塑料占总量的77.30%,且随着覆膜年限的增加,小粒径（<1 mm）微塑料占比显著升高（P<0.05）,随着土层深度的增加,其占比亦逐渐增加,施加有机肥对微塑料粒径没有显著影响.微塑料颜色组成以透明（49.77%）为主,其次是黑色（16.35%）和白色（16.27%）,覆膜年限和有机肥施加对土壤中微塑料的颜色影响不显著（P>0.05）,但覆膜年限显著增加了透明微塑料的占比.微塑料类型主要包括纤维类、薄膜类、碎片类、泡沫类和颗粒类,其占比分别为： 49.77%、25.41%、19.15%、3.26%和2.41%.耕层土壤微塑料的主要聚合物类型包含聚乙烯（PE）、聚丙烯（PP）和聚苯乙烯（PS）,分别占总量的21.37%、18.57%和19.77%.由此,山东德州花生田耕层土壤中普遍存在微塑料,且地膜和有机肥施用是其主要来源,这可为花生田耕层土壤微塑料污染物防控提供重要依据.     

长江流域微塑料污染特征及生态风险评价

长江作为我国第一大河流,其流域微塑料污染状况尚未得到全面研究.为此,针对流域尺度建立微塑料综合调查评价体系,以探明长江流域微塑料空间分布与组成特征,解析其影响因素,评价其生态风险.结果表明,研究区域微塑料丰度范围为21~44 080 n·m^-3,平均丰度为4 483 n·m^-3.在其空间分布上,支流高于干流（赣江除外）,其中岷江流域成都段是微塑料检出丰度最高的支流地区.流域微塑料尺寸集中在0~1 mm,形状以纤维和碎片为主,颜色以彩色（有色）和透明为主.进一步引入微塑料多样性指数,发现辛普森指数和香农-维纳指数均能量化流域微塑料特征组成的多样性,但二者变化趋势存在一定差别.回归分析显示,人类活动与微塑料丰度呈显著正相关（P<0.05）,8种人类活动因子中民用汽车保有量和旅游收入与微塑料丰度相关性最强,说明交通运输业和旅游业是影响微塑料分布的主要因素.从微塑料的潜在生态风险指数来看,长江流域微塑料具有一定的生态风险,68.97%的区域属于Ⅲ级和Ⅳ级风险区,其中太湖微塑料生态风险应受到更为广泛地关注.     

滇池近岸水体微塑料污染与富营养化的相关性

内陆淡水湖泊微塑料污染受到广泛关注,但与水体富营养化的相关性尚不明晰.在滇池沿岸布设24个采样点,研究了近岸表层水体微塑料丰度、聚合物成分、粒径、颜色及形态,同步测定富营养化相关水质指标并计算富营养化状态指数.结果表明,滇池近岸水体微塑料丰度在800~6000 n·m^-3之间,平均为2867 n·m^-3,检出的聚合物类型主要是聚对苯二甲酸乙二醇酯（polyethylene terephthalate,PET）、聚醚型聚氨酯（polyetherurethane,PEU）、聚丙烯（polypropylene,PP）、聚乙烯（polyethylene,PE）和聚醋酸乙烯酯（polyvinyl acetate,PVAc）.微塑料粒径以0.2~0.5 mm为主,纤维状微塑料是最主要的检出形态,其次为碎片和薄膜.24个监测点中,处于重度、中度、轻度富营养化和中营养水平的样点数分别占8.33%、58.33%、29.17%和4.17%,主要污染物为总氮（TN）.相关性分析发现滇池近岸水体微塑料丰度与TN质量浓度呈极显著正相关（P<0.01）,与叶绿素a（Chl-a）呈负相关,但未达到显著性水平（P>0.05）,靠近昆明市主城区的北岸水体中微塑料丰度和TN质量浓度均显著高于其他三岸,主要来源于污水处理厂尾水排放.     

海州湾潮间带沙蚕对沉积物微塑料的指示作用

2018年7月于海州湾潮滩设置3个断面共9个站位,通过对海州湾潮滩沉积物中以及沙蚕体内微塑料的丰度和形态特征的研究,探讨了沙蚕体内微塑料的来源,以及沙蚕对潮滩沉积物微塑料的指示作用.结果表明,潮滩沉积物中微塑料的平均丰度为（0.49±0.17） n·g^-1,处于国内近岸环境研究的较高水平.所有检测到的微塑料中,最为丰富的形态和颜色类型分别为纤维和黑灰色,材质以聚乙烯（polyethylene,PE）、聚酯纤维（polyester,PET）和聚苯乙烯（polystyrene,PS）为主.沙蚕中微塑料检出率为77.78%~86.67%,平均丰度为（6.68±2.21） n·ind^-1,其丰度与个体质量显著正相关（r=0.42,P=0.002）,个体质量1.5 g以上的沙蚕中微塑料丰度显著高于<0.5 g和0.5~1 g两个组别（F₃=141.029,P=0.000）,微塑料形态以黑色或蓝色小纤维为主,主要材质同样为聚乙烯和聚酯纤维.通过对0~3 mm范围内的微塑料各项特征分析发现,沉积物与沙蚕中的微塑料丰度强相关（r=0.79,P=0.01）,其主要形态组成（r=0.90,P=0.035）和材质组成（r=0.73,P=0.024）同样显著相关,表明沙蚕会摄取沉积环境中的微塑料,存在与沉积物之间的微塑料交换,沙蚕作为沉积物中微塑料污染指示生物物种是可行的.     

南水北调丹江口库区土壤中微塑料分布特征及风险评估

为探究丹江口库区土壤中微塑料赋存特征及影响因素,通过对果园、旱地、水田和湿地进行土壤样品采集,利用密度分选、显微镜观察和拉曼光谱仪测定等方法对土壤中微塑料进行鉴定.结果表明,研究区采集的64个样本均有微塑料检出,丰度范围为645~15161 n·kg^-1.空间分布上,库尾高于库中和库首,且表层土壤（0~20 cm）中微塑料的丰度明显低于下层土壤（20~40 cm）.微塑料主要类型为聚丙烯（26.4%）和聚酰胺（20.2%）,粒径主要集中在50~500 μm之间（75%）,常见形状为碎片状（66.2%）.相关性分析显示,土壤微塑料丰度与土地利用、距水面和住宅的距离、人口密度和土壤性状密切相关.从微塑料污染风险来看,72.1%区域微塑料聚合物污染指数处于Ⅲ级和Ⅳ级,丹江口库区存在一定的微塑料污染风险.研究结果可为微塑料风险评估提供支撑.     

广东省近岸海域微塑料赋存特征与风险评价

微塑料在海洋环境中广泛存在,成为了一种备受关注的新污染物. 为揭示广东省近岸海域表层海水中微塑料的污染特征,自江门至汕头选择了9个海湾（河口）,通过现场采样、氧化消解、目视识别和成分鉴定等方法探究微塑料的分布和组成特征,解析其潜在来源,并结合污染负荷指数法和聚合物风险指数法评估其生态风险. 结果表明,广东省近岸海域30个表层海水样品中均检出微塑料,微塑料的丰度范围为70~920 n·m^-3,平均丰度为（295.3 ±175.3）n·m^-3. 空间分布上,微塑料的最高丰度出现在珠江口,最低丰度出现在神泉湾. 组成特征上,微塑料的主要成分为聚丙烯（31.2%）、酚醛树脂（16.0%）、聚对苯二甲酸乙二醇酯（15.3%）和聚乙烯（10.9%）,主要形状、颜色和尺寸类别分别为纤维（57.5%）、透明（72.0%）和0.5~1 mm（32.8%）. 微塑料的可能来源主要包括水产养殖、渔业捕捞、航海、旅游、市政污水排放和洋流输送. 模型评价结果显示,微塑料的污染负荷风险较低,但聚合物风险处于中-高水平. 研究结果为广东省塑料污染治理行动方案提供数据基础,并为海洋微塑料污染防治工作提供支撑.     

淮河流域安徽段水体和沉积物微塑料赋存特征及风险评估

为探究淮河流域安徽段水体与沉积物微塑料赋存特征及生态风险级别,采用野外采样、体式显微镜、扫描电镜、傅里叶红外光谱（FTIR）以及风险指数（H）和污染负荷指数（PLI）模型等方法,分析了流域水体和沉积物微塑料现状,并进行了微塑料生态风险评估.结果表明,流域各点位微塑料检测率为100%,表层水与沉积物微塑料平均丰度分别为（39800±3367） n ·m^-3和（5078±447） n ·kg^-1,下游微塑料平均丰度要高于上游和中游.水体和沉积物微塑料粒径以20~150 μm为主,占比分别为82.96%和80.77%.微塑料形状主要为纤维（水体76.05%、沉积物84.53%）、薄膜（水体21.83%、沉积物15.43%）和碎片（水体2.12%、沉积物0.04%）.水体和沉积物中微塑料主要以透明颜色为主,占比分别为63.31%和83.69%.水体和沉积物主要以聚乙烯（水体65.74%、沉积物80.62%）和聚丙烯（水体18.43%、沉积物9.71%）为主,微塑料主要来源于农业薄膜、废弃渔具渔网和港口人为废弃的塑料袋.微塑料风险指数（H）模型评估表明部分点位风险指数较高,淮河流域安徽段微塑料风险等级为Ⅱ级,污染负荷指数（PLI）模型评估表明流域地表水体和沉积物总体上生态风险较低.     

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.