永定河上游地表水-地下水水化学特征及其成因分析

永定河上游流域是冀西北重要的水源涵养区和生态屏障区,受气候变化和高强度人类活动影响,径流减少和水环境恶化问题日益突出.深入研究自然和人类活动共同影响下的地表水-地下水水化学特征及其成因,可为区域水资源可持续利用提供科学参考.本研究利用（δ²H和δ¹⁸O）氢氧同位素关系明确地表水和地下水来源,并在此基础上结合数理统计和水文地球化学方法,分析水化学特征及其成因.结果表明,地表水和地下水主要来源于降水.受自然因素及人类活动的共同影响,洋河和桑干河流域水化学类型差异显著.整体上,地表水离子浓度表现为：桑干河>洋河.桑干河流域地表水主要阳离子为Na⁺,主要阴离子为Cl^-和SO₄^2-,且水化学类型多样;洋河流域地表水主要阴阳离子分别为HCO₃^-和Ca²⁺,水化学类型分布相对集中.影响地表水水化学的自然因素主要为矿物溶解和蒸发,但人类活动却体现出流域差异,其中桑干河为支流的工业废水排放,而洋河流域为农业生产和城市.然而,由工业废水排放和酸雨输入导致的地表水Cl^-和SO₄^2-浓度持续增加,是地表水资源可持续利用的限制因素.因此,未来桑干河流域地表水资源利用要综合考虑总盐分和水化学组成的影响,而洋河流域主要考虑总盐分的影响.因地制宜地进行地表水资源利用,是永定河上游水资源可持续利用和恢复地下水位行之有效的措施.     

安徽涡河流域水化学与同位素特征及水体转化关系

以安徽涡河流域为研究区域,通过采集涡河地表水、浅层地下水和中深层地下水样品,运用Gibbs图、离子比例和MixSIAR模型等方法对各类水体的水化学参数和氢氧同位素进行分析,揭示并量化了各类水体之间的转化关系.结果表明,研究区地表水和地下水主要呈现中性至弱碱性,地表水的水化学类型以Cl·SO₄ ·HCO₃ -Na和Cl·SO₄ -Na型为主,浅层地下水以HCO₃ -Ca·Mg和HCO₃ -Mg·Na型为主,中深层地下水主要为Cl·HCO₃ -Na型.各类水体的水化学特征受到岩石风化、蒸发浓缩及正向阳离子交换等多重因素共同影响.地表水和地下水的δ¹⁸O和δ²H分布特征表明大气降水是该区域水体的主要补给来源,且地下水δ¹⁸O和δ²H值与K⁺、Na⁺、Cl^-、SO₄ ^2-和NO 3^-浓度存在显著相关性.根据MixSIAR模型分析结果,地表水接受大气降水和浅层地下水的贡献率分别为46.5 %和53.5 %;浅层地下水的补给来源分别为大气降水（57.4 %）和地表水（42.6 %）;中深层地下水的补给主要来自上游地下水的侧向径流补给.     

汾河流域地表水水化学同位素特征及其影响因素

汾河是山西的母亲河.由于水资源过度开发及社会经济发展影响,生态环境恶化.经过一系列治理保护措施,水质得到改善.利用统计学、Piper三线图和Gibbs模型等方法,分析了汾河流域地表水水化学和氢氧同位素特征及其来源,揭示了汾河流域地表水水质演化过程.结果表明,汾河干流地表水中主要水化学组分沿着径流路径含量逐渐增加;汾河上游地表水水化学类型主要以HCO₃·SO₄·Cl-Ca·Na·Mg为主,中游和下游地表水水化学类型主要以SO₄·HCO₃·Cl-Ca·Na·Mg为主.汾河流域地表水水化学组成主要受岩石风化作用和蒸发结晶作用影响,而降雨影响较小.Na⁺和K⁺主要来源于蒸发盐岩的溶解以及周边黄土中含Na矿物溶解,水体中Ca²⁺、Mg²⁺和HCO₃^-主要来源于碳酸盐岩的溶解,SO₄^2-除来源于石膏的溶解,还可能来源于汾河周边黄土层中硫化矿物的溶解.干流地表水δD和δ¹⁸ O平均值分别为-62.60‰和-8.42‰,氢氧同位素特征进一步表明其主要受蒸发作用的影响.流域内支流及岩溶水水化学组分差异较大.结果可为汾河流域生态修复保护及生态文明建设提供依据.     

武汉长江新城地下水化学特征及成因分析

为研究武汉地下水水化学特征及形成原因,以长江新城为研究区,于2019年7-9月采集地表水和地下水样品,对区内地下水和地表水进行测试分析.基于水化学结果,运用数理统计、离子比值分析、矿物饱和指数等方法,揭示了长江新城的水化学演化过程和主要离子来源.结果表明,区内地下水阳离子以Ca²⁺为主,阴离子以HCO₃^-为主,地下水和地表水的补给来源密切相关.地下水主要受岩石风化作用控制,同时还受一定程度的蒸发浓缩作用影响,主要离子来源受碳酸盐岩溶解沉淀控制,也存在硅酸盐岩和蒸发盐岩风化溶解作用的影响.地下水受生活污水和农业肥料施用影响较大.     

店埠河流域地表水-地下水水化学特征及其成因分析

巢湖是我国水污染防治的重点水体,但近年来一直处于较高的富营养化水平.以巢湖二级支流店埠河流域内的地表水和地下水为研究对象,测试不同水体水化学组成和氢氧同位素值,综合运用数理统计、Piper三线图、Gibbs图和离子比值等方法,分析其季节性和空间变化特征,探讨地表水和地下水的水化学特征和形成机制.结果表明,①大气降水是店埠河流域地表水和地下水的主要补给来源,地表水的蒸发分馏效应比地下水更显著.不同时期,地表水比地下水更富集氢氧稳定同位素.地表水和地下水中氢氧稳定同位素均呈季节性变化特征,丰水期相对富集,枯水期相对贫化.②店埠河流域地表水和地下水均为弱碱性水,地表水中各离子浓度明显小于地下水,地表水中阳离子以Ca²⁺和Na⁺为主,地下水中阳离子以Ca²⁺为主,水体中的优势阴离子均为HCO₃^-.地表水的水化学类型以HCO₃·Cl-Na·Ca型水为主,地下水以HCO₃-Na·Ca型水为主.③地表水和地下水主要水化学指标浓度具有一定的时空差异性.从丰水期到枯水期,地表水中TDS、K⁺、Na⁺、Ca²⁺、Mg²⁺、Cl^-和SO₄^2-浓度整体呈现上升趋势.地下水中Na⁺、Ca²⁺和Mg²⁺浓度整体变化不大,略有增加趋势,Cl^-、SO₄^2-和NO₃^-浓度整体呈上升趋势.从上游到下游,地表水中主要水化学指标浓度呈现先减小后增大的趋势,NO₃^-浓度增幅最大.地下水在径流方向上主要水化学指标浓度整体变化不大,但呈现出排泄区大于补给区的规律.④水体水化学特征的形成主要受水-岩作用控制,同时还受到人为因素影响.水-岩作用主要为硅酸盐岩、盐岩和碳酸盐岩等矿物的风化溶解.污水处理厂污水、生活污水和粪肥等污染物已明显改变了局部水体的水化学特征.⑤与2016年相比,地表水中的NO₃^-浓度已有不同程度地减少,当地政府进行的氮污染控制工作已取得一定成效,但仍需在店埠河下游、部分支流（定光河和马桥河）和部分居民点加强对污水及粪肥的污染防控.     

平朔矿区不同水体水化学特征及氟分布成因

为了探明采煤驱动下平朔矿区所在流域内不同水体水化学特征及氟分布成因,综合运用水化学图解、主成分分析和地球化学模拟等方法,对2020~2021年采集的468组地表水、地下水和矿井水样品进行分析.结果表明,地表水、地下水和矿井水均呈近中性至弱碱性;地表水和矿井水中优势阴离子为SO₄^2-,地下水中优势阴离子为HCO₃^-,Ca²⁺是所有水体中的优势阳离子.地表水和矿井水水化学类型以SO₄·HCO₃-Ca·Mg为主.地下水水化学类型主要为HCO₃-Ca·Mg,采煤区的浅层或深层地下水存在HCO₃·SO₄-Ca·Mg型.水体水化学主要受碳酸盐岩风化溶解、采煤活动以及含氟矿物的风化溶解影响,采煤和工农业等人类活动加速了不同水体间水化学转换,尤其是浅层地下水.水体ρ（F^-）介于0.10~1.76 mg·L^-1,其中,42%浅层地下水F^-浓度高于国家饮用水安全限值;时空分布上,西北至东南地下水中F^-浓度平均值呈增加趋势,3月和8月F^-浓度偏高.高氟浅层地下水化学呈现偏碱性和高Na⁺特征.F^-富集主要受采煤活动和含氟矿物风化溶解影响,水体中方解石饱和加速了含氟矿物的风化溶解.     

艾比湖区域景观格局与河流水质关系探讨

为进一步明确景观格局对河流水质的影响.本研究选择新疆艾比湖区域为研究对象,以28个水质采样点为中心,建立100、200、300、400 m的河流缓冲区,并提取土地利用/覆被-景观格局数据.首先,通过主成分分析获得水环境的主要水质变量.其次,利用多元线性回归探讨研究区不同宽度缓冲区土地利用/覆被-景观格局变化对河流水质的影响,获得水质管理的有效缓冲区.结果表明：①2015年5月,在艾比湖区域测得的18个地表水水质指标中提取TDS、SO₄^2-、NH₄⁺-N、HCO₃^-、Na⁺和TP这6个水质指标.②对斑块密度（PD）、最大斑块指数（LPI）、边缘密度（ED）、景观形状指数（LSI）、蔓延度指数（CONTAG）进行统计分析,发现人类活动在4个缓冲区内强弱不均.③本文在不同尺度的缓冲区下,将PD、LPI、ED、LSI、CONTAG和TDS、SO₄^2-、NH₄⁺-N、HCO₃^-、Na⁺、TP分别进行相关性分析,发现300m缓冲区相关性最为显著.④在300m缓冲区内,通过多元线性回归分析,将TDS、HCO₃^-与其各自对应的景观指数的关系进行定量化表达,进一步探明区域流域地表水与周围一定缓冲区范围内的景观格局的内在关系.     

会仙岩溶湿地地下水主要离子特征及成因分析

以我国最大的低海拔岩溶湿地会仙岩溶湿地为研究区,对该区丰水期、平水期和枯水期共采集的27组地下水样品中常规离子进行检测和分析,在分析会仙岩溶湿地地下水主要离子化学特征和不同时期变化基础上,运用单指标污染标准指数法对不同时期地下水进行污染评价,利用多元统计、Gibbs模型和离子比例关系识别地下水主要离子成因.结果表明,研究区内岩溶地下水主要为弱碱性淡水,Ca²⁺和HCO₃^-为优势离子.不同时期地下水主要离子总浓度顺序为：平水期 > 丰水期 > 枯水期,枯水期水质优于丰水期和平水期.地下水中K⁺和NO₃^-主要受含水层空间分布差异影响,Mg²⁺、SO₄^2-、NO₂^-、NH₄⁺和TDS受时空尺度综合作用,Na⁺、Ca²⁺、HCO₃^-和Cl^-为水体中较稳定离子.受碳酸盐岩控制,丰水期、平水期和枯水期地下水化学类型具有高度一致性,HCO₃-Ca水占比分别为77.78%、77.78%和88.89%.地下水主要受SO₄^2-、NO₃^-和NO₂^-污染,NO₃^-出现极严重程度污染样点,SO₄^2-在丰水期和平水期出现较重污染样点.地下水化学组分主要受水岩作用控制,Ca²⁺和HCO₃^-主要来源于方解石风化溶解,少量水点受白云岩、白云质灰岩及硫铁矿控制导致Mg²⁺和SO₄^2-浓度偏高,K⁺、Na⁺、SO₄^2-、NO₃^-和Cl^-部分来源于大气降水,Na⁺和Cl^-部分来源于当地居民生活,K⁺与种植施用的钾肥相关,NO₃^-主要来源是化学肥料.     

黄河流域内蒙古段水化学同位素特征及水体转化关系

以黄河流域内蒙古段为研究区,于2021年7月（丰水季）和10月（枯水季）采集降水、黄河干流、黄河支流与季节性河流、乌梁素海、哈素海、岱海、灌区渠系和地下水等水样,测试不同类型水体的水化学组成和氢氧同位素值.综合运用Piper三线图、Gibbs图、离子比例和MixSIAR混合模型等研究方法,分析了黄河流域内蒙古段水化学演变规律,并揭示降水、地表水和地下水的转化关系.结果表明,研究区地下水和地表水均偏弱碱性,水体中优势阴离子为Cl^-,优势阳离子为Na⁺,地表水水化学类型以Cl ·SO₄-Na ·Mg和SO₄ ·HCO₃-Na ·Mg为主,地下水水化学类型以Cl ·SO₄-Na ·Mg和SO₄ ·HCO₃-Na ·Ca.地下水Ca²⁺和Mg²⁺主要来源于硅酸盐和蒸发岩的溶解,地表水Ca²⁺和Mg²⁺主要源于碳酸盐岩溶解,且水中碳酸和硫酸参与了碳酸盐矿物和硫化矿物溶解的过程,不同水体Na⁺和Cl^-均受人为污染源的影响.受季节效应影响,地表水和地下水δD和δ¹⁸ O丰水期较枯水期高,研究表明,地表水在接受大气降水补给后受到了蒸发分馏作用的影响,地下水补给源复杂.MixSIAR模型揭示出,研究区地表水是地下水的主要补给来源,占总补给量的52.4%~62.2%,大气降水是地表水的主要补给来源,占总补给量的85.4%~97.1%.     

张家口地区枯水期地下水水化学特征及其成因机制分析

为更好支撑首都水源涵养功能区和生态环境支撑区建设,开展张家口地区枯水期地下水水化学特征及其形成机制研究,对地下水资源合理开发利用具有重要参考意义.采集41组地下水样品,运用描述性统计分析、Piper三线图、相关性分析、Gibbs图及离子比值等方法,分析了研究区地下水水化学类型、组成特征和控制因素.结果表明,研究区地下水整体呈弱碱性,总硬度变化范围为105.00~1 433.00 mg·L^-1,ρ（TDS）变化范围在137.00~2 286.00 mg·L^-1,坝上地区地下水中总硬度和TDS质量浓度均高于坝下地区.研究区地下水中HCO₃^-和Na⁺为主要优势阴、阳离子.地下水中主要组分超标率最高的为总硬度,超标率为36.59%,坝上地区地下水中各组分的超标率和最大超标倍数均大于坝下地区.研究区地下水水化学类型以HCO₃-Ca·Mg·Na型为主,坝上地区和坝下地区水化学类型差异较小,SO₄^2-、Cl^-、HCO₃^-、Na⁺和Mg²⁺对TDS的贡献最大.地下水水化学特征受盐岩、钠长石和白云岩等岩石矿物风化溶滤作用、阳离子交换作用和人类活动的共同影响,蒸发结晶和大气降水对研究区地下水主要离子来源贡献较小.坝上地区地下水受人类活动影响要大于坝下地区,其中NO₃^-主要来源于农业活动.     

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.     

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.     

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.     

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.