三峡库区消落带土壤中硫酸盐还原菌对汞甲基化作用的影响

为探究三峡水库这一特殊的周期性干湿交替环境中,硫酸盐还原菌(sulfate-reducing bacteria,SRB)是否在汞的生物甲基化过程中起主导作用,本文以库区消落带原土为研究对象,以灭菌土+接种硫酸盐还原菌Desulfovibrio africanus(D.africanus,DSM-2603)为对照(试验A),在每公斤土壤分别添加0、1、5 mg汞浓度条件下,模拟研究原土(试验B)中总汞(THg)和甲基汞(MeHg)含量的动态变化、总硫酸盐还原菌(SRB)数量变化,以及影响土壤中甲基汞含量的环境因子分析.结果表明,淹水状况有利于THg从土壤中释放,且Hg含量越高,释放越快;菌株D.africanus对汞具生态适应性,其菌数与MeHg含量显著正相关:在5 mg·kg~(-1)Hg条件下,D.africanus菌数可达3.65×10~4cfu·g~(-1),MeHg含量也高达7.60×10~4ng·kg~(-1).值得注意的是,试验B处理中,一方面消落区原土中SRB菌数较少,平均仅193 cfu·g~(-1);另一方面,土壤MeHg含量较低:在5mg·kg~(-1)Hg条件下,MeHg含量仅为5.54×10~3ng·kg~(-1),且总SRB菌数与MeHg含量无显著相关性.由此可以推测,在三峡水库消落区这种非严格厌氧土壤环境中,SRB并非优势菌群,其中还存在着其它对生物汞甲基化起主导作用的好氧或兼性厌氧微生物种群.     

三峡库区涪陵和忠县两地居民发汞含量水平及影响因素分析

为评价三峡库区居民汞暴露风险,在三峡库区腹心地带的涪陵和忠县两地采集了238份当地居民头发样本,分析了总汞(THg)和甲基汞(Me Hg)含量.结果表明,两地居民头发THg、Me Hg平均含量分别为(0.50±0.54)μg·g~(-1)、(0.35±0.25)μg·g~(-1).其中,涪陵居民头发THg、Me Hg平均含量分别为(0.71±0.87)μg·g~(-1)、(0.53±0.46)μg·g~(-1),均高于忠县居民头发THg[(0.41±0.36)μg·g~(-1)]、Me Hg[(0.28±0.26)μg·g~(-1)]平均含量水平,但两地头发总汞平均含量均低于美国EPA安全参考剂量(1μg·g~(-1)).不同年龄段的居民发汞含量存在显著性差异(P0.05),其中40~50岁年龄段居民发汞含量最高;不同性别间发汞含量差异不显著(P0.05),但女性发汞含量略高于男性.居民发汞含量与食鱼频率呈正相关,渔民发汞含量显著高于非渔民发汞含量(P0.01),且渔民头发样本总汞含量均值(1.44±0.79)μg·g~(-1)超过了EPA安全参考剂量.两地吸烟者头发总汞含量[(0.55±0.24)μg·g~(-1)、(0.58±0.54)μg·g~(-1)]均显著高于非吸烟者头发总汞含量[(0.51±0.30)μg·g~(-1)、(0.36±0.26)μg·g~(-1)].三峡库区居民汞暴露风险总体较低,但渔民存在一定的汞暴露风险.     

不同母质发育土壤Cd环境行为对水分管理模式的响应差异

为探明不同母质发育稻田土壤Cd环境行为对水分管理模式变化的响应差异,通过不同的水分管理模式(长期淹水、湿润灌溉和干湿交替),在3种外源Cd水平下(0.5、 2.0和5.0mg·kg~(-1)),对2种母质发育稻田土壤(黄泥田和麻砂泥)进行培养试验,分析了土壤氧化还原电位(Eh值)、pH值、土壤溶液Cd含量及土壤Cd赋存形态等指标.结果表明,不同母质发育土壤pH值和Eh值对水分管理模式变化的响应存在差异,土壤pH值变化率分别为长期淹水:-2.61%(黄泥田)和2.25%(麻砂泥),干湿交替:-1.96%(黄泥田)和0.52%(麻砂泥),湿润灌溉:-4.08%(黄泥田)和-0.52%(麻砂泥), 2种母质土壤Eh值与pH值呈极显著负相关; 2种母质类型土壤溶液Cd质量浓度随水分管理模式变化规律一致,且该质量浓度麻砂泥高于黄泥田,其均值分别为:1.03μg·L~(-1)(黄泥田), 1.07μg·L~(-1)(麻砂泥);水分管理模式对不同母质发育土壤中有机结合态和铁锰结合态Cd含量影响不显著,长期淹水会促进Cd向残渣态转化,且在黄泥田中这一促进作用比在麻砂泥中强.因此,在应用水分管理调控土壤Cd生物有效性的过程中,需根据土壤母质类型区别实施.     

微生物对汞矿区农田土壤汞甲基化的影响

为研究典型汞矿区农田土壤中汞的甲基化作用,实验以受汞污染的旱田土壤和稻田土壤为对象,分别进行灭菌,促进硫酸盐还原菌(SRB)活性处理,抑制SRB活性处理以及促进铁还原菌(FeRB)活性处理,分析非微生物作用和微生物作用对土壤甲基汞(MeHg)生成的影响.结果表明,促进SRB活性处理的土壤MeHg生成量最高,其中旱田土MeHg增量为0.15~0.38μg·kg~(-1),稻田土壤MeHg增量为1~2μg·kg~(-1);抑制SRB活性处理和促进FeRB活性处理的MeHg增量较小,最高值仅为0.025μg·kg~(-1).相比于旱田土壤,稻田土壤具有更高的汞甲基化能力,其MeHg生成量是旱田土壤的4~9倍.土壤SRB数量与MeHg生成量具有相同的变化趋势,二者具有显著的正相关性(R~2=0.57,P0.01).因此,该研究区土壤汞甲基化作用主要是微生物汞甲基化作用,且主要的汞甲基化细菌是SRB.此外,稻田是农田中MeHg生成的活跃地区,在评估和控制MeHg对人体健康危害时需要重点关注.     

三峡水库消落带土壤与优势植物淹水后对土-水系统汞形态的影响

三峡库区消落带落干期植被生长茂盛,蓄水后消落带被淹没,土壤-植物系统在长时间淹水情况下,随着体系内物理化学性质的改变,汞形态也会发生变化,从而对库区水生生态系统中汞含量以及形态带来一定的影响.为此,本研究选取三峡库区4种优势植物室内栽培,再进行室内模拟淹水试验,研究淹水后土壤、水体中甲基汞(Me Hg)以及其他形态汞的变化.结果表明,淹水过程中植物的存在有利于土壤Me Hg的生成,同时对上覆水不同形态汞浓度影响显著.狗牙根作为消落带优势种,由于其体内总汞及甲基汞含量较高,淹水后对土壤以及上覆水系统中甲基汞以及其他汞形态的影响最为明显.淹水第90 d,狗牙根+土+江水(B1)处理土壤Me Hg的含量最高,为(1 135.86±113.84)ng·kg~(-1),是不加植物的对照处理土+江水(CK2)中土壤Me Hg含量的2倍左右;上覆水总甲基汞(TMe Hg)、溶解态甲基汞(DMe Hg)、总汞(THg)、溶解态汞(DHg)和活性汞(RHg)均呈峰值偏左的抛物线状变化,在第30 d时达到峰值,其中B1处理上覆水TMe Hg、THg和DHg最高,分别为(2.88±0.06)、(40.29±2.42)和(35.51±3.77)ng·L~(-1),三者中溶解态汞是其主要存在形式.因此可以推测三峡库区消落带植物淹水后将增加水库汞污染负荷.     

盐渍化条件下污灌区土壤重金属的释放特征

以受盐渍化和重金属双重胁迫的天津污灌区土壤为研究对象,通过径流实验和淋溶实验,探讨盐渍化土壤重金属的释放特征及对水质安全的影响.研究的盐分种类为污灌区土壤盐渍化进程中的主要盐分Na Cl,设置的盐度梯度为7个,添加质量分数为0(CK)~5%,污染土壤中Cd、Pb和Hg含量分别为2.21、234.1和0.601 mg·kg~(-1).结果表明,(1)不同盐度处理下产流所需时间为(51'25″±15″),盐度对径流产流时间影响不显著;(2)随着Na Cl盐度梯度的提高,土壤径流和淋溶液中Cd、Pb和Hg的累计释放量均显著上升.Cd累计释放量从CK的53.40μg·kg~(-1)(径流)和55.63μg·kg~(-1)(淋溶)分别提高到5%Na Cl盐度处理的122.56μg·kg~(-1)(径流)和135.79μg·kg~(-1)(淋溶),Pb的累计释放量从CK的168.30μg·kg~(-1)(径流)和94.44μg·kg~(-1)(淋溶)分别提高到5%Na Cl盐度处理的340.68μg·kg~(-1)(径流)和201.93μg·kg~(-1)(淋溶),Hg的累计释放量从CK的39.66μg·kg~(-1)(径流)和9.60μg·kg~(-1)(淋溶)分别提高到5%Na Cl处理的89.37μg·kg~(-1)(径流)和11.97μg·kg~(-1)(淋溶).同时,径流及淋溶液中可溶态重金属含量显著上升,颗粒态含量有所下降,其所占比例也显著下降.Cl-含量与重金属累计释放量之间关系可以用线性或对数模型拟合.(3)高盐度处理下径流和淋出液中Cd浓度超过地下水水质Ⅲ类标准,对环境及地下水存在一定威胁;径流和淋溶前期Pb浓度超过Ⅲ类标准;径流和淋溶过程中Hg浓度均超过Ⅲ类标准,风险较高.本研究结果表明高强度降雨强度下污染农田土壤重金属释放风险不可忽视.     

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NH⁺₄-N和DOC含量,沉积物中NO^-₃-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(266.42μg·m^-2·h^-1)>高强度(199.10μg·m^-2·h^-1)>低强度(152.93μg·m^-2·h^-1)>长期淹水(9.57μg·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...     

水泥粉尘对农田土壤污染的环境磁学响应

为了探索水泥工业生产与厂周围农田土壤环境变迁之间的关系,在安徽省凤阳县水泥工业区周围农田内采集了麦地土壤和3条测线(EW、N-W、N-S)上稻田土壤,对土壤样品及水泥粉尘的磁学参数和金属元素(Al、Fe、K、Ca、Mg、Na、Cr、Ba、Mn、Zn)含量进行了测量.结果显示,两类土壤样品的磁学性质主要由磁铁矿控制,磁性矿物含量高于土壤母质参考值、低于水泥粉尘,磁性矿物粒径介于土壤母质和水泥粉尘之间.麦地土壤样品中Ca、Zn含量的平均值(85.4 g·kg~(-1)、101.0 mg·kg~(-1))高于3条测线上稻田土壤的平均值(10.6 g·kg~(-1)、51.0 mg·kg~(-1)(E-W);11.0g·kg~(-1)、68.0 mg·kg~(-1)(N-S);8.9 g·kg~(-1)、55.6 mg·kg~(-1)(N-W)),且大幅高于土壤母质参考值(5.9 g·kg~(-1)、29.9 mg·kg~(-1)),但低于水泥粉尘的值(344.0 g·kg~(-1)、110.3 mg·kg~(-1)).内梅罗指数PN结果显示,麦地土壤样品呈现出重度污染(5PN20),3条测线上稻田土壤样品呈现出轻度污染到中度污染的特征(1PN3),离水泥厂越近污染越严重.所有土壤样品的磁学参数χ、SIRM、χARM与PN存在显著正相关关系(r=0.918、0.944、0.968).因此,磁学参数χ、SIRM、χARM可以作为农田土壤被水泥粉尘污染程度的指示.     

东新开河小流域土壤汞空间分布特征及风险评价研究

研究选择松花江三级支流东新开河小流域,在其干流及支流选定了13个河流断面,测定并讨论了断面两侧岸带土壤总汞的空间分布、污染现状和生态风险。结果表明,小流域内土壤汞含量为14μg·kg~(-1)～499μg·kg~(-1),均值为(78±11.87)μg·kg~(-1),其中超过长春市土壤背景值(40μg·kg~(-1))的采样点占比为63.8%。流域总体表现为无汞污染(污染指数为-0.11),最高处汞污染为强(污染指数为3.06)。流域总体中有中度潜在生态风险(78),潜在生态风险最高处为极强(499)。     

江西典型钨矿开采对周边环境稀土元素含量的影响

研究了江西省典型钨矿区开采和冶炼对周边农田土壤、水体和白菜中稀土元素含量的影响.结果表明:钨矿区周边农田土壤中稀土元素含量范围在256~459 mg·kg~(-1)之间,平均值为373 mg·kg~(-1),土壤中稀土含量均高于江西省和全国土壤稀土元素含量的背景值,分别是它们的1.77倍和1.99倍.矿区河水中稀土元素浓度达3086μg·L~(-1),为对照区河水稀土元素浓度的497倍.矿区15个样地白菜稀土元素含量范围为773~5992μg·kg~(-1),平均值为3007μg·kg~(-1),为非矿区白菜稀土元素含量的5.22倍,矿区白菜稀土元素含量远超过我国蔬菜卫生标准稀土元素含量的限值(0.70 mg·kg~(-1)),说明钨矿开采冶炼已造成周边环境的污染,并对矿区居民身体健康构成潜在威胁.     

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.