应用化学提取法评价大气颗粒物中重金属的生物有效性

以广州市楼顶降尘为研究对象,在分析其粒度分布和重金属总量的基础上,采用单一化学提取法（DWLP、TCLP）和多级化学提取法（SEP）研究了大气颗粒物中4种重金属元素的生物有效性。结果表明：样品中96％以上颗粒小于100μm,其中10μm和2．5μm以下颗粒分别占33％和11％。大气颗粒物中重金属含量很高,Cu、Pb、Zn和Cd的平均含量分别为362．43、1033．81、830．32和5．80mg／kg,是广东省环境土壤背景值的17～64倍。单一提取法中,TCLP的提取效率明显高于DWLP,表明pH值是影响大气颗粒物中重金属释放的主要因素。SEP法结果显示,Zn和Cd的生物可利用态比例远高于Cu和Pb。经DWLP和TCLP法提取后,颗粒物中重金属的总含量有不同程度的降低,生物可利用态所占比例明显增加。通过综合分析,发现SEP此其他两种方法更适用于评价大气颗粒物中重金属的生物有效性。     

黄棕壤铁铝氧化物与土壤稳定性有机碳和氮的关系

用6%NaOCl氧化不同粒级的黄棕壤,得到稳定性有机碳和氮的样品.用选择性溶提技术提取铁铝氧化物的含量,与稳定性有机碳和氮的关系表明:在2～250μm粒级上,游离铁、无定形铁和络合态铁含量的变化范围分别为6～60.8g/kg、0.13～4.8g·kg-1和0.03～0.47g·kg-1,在2μm粒级上分别为43.1～170g·kg-1、5.9～14.0g·kg-1和0.28～0.78g·kg-1.在2μm粒级上,无定形铝和络合态铝含量变化范围分别为0.08～1.34g/kg和0.11～0.47g/kg,在2μm粒级上分别为2.96～6.20g·kg-1和0.38～0.78g·kg-1.水稻土黄棕壤的选择性溶提铁的含量一般高于旱地黄棕壤,而选择性溶提铝的含量低于旱地黄棕壤.在2～250μm粒级上,土壤稳定性有机碳和有机氮含量变幅分别为0.93～6.0g·kg-1和0.05～0.36g·kg-1,在2μm粒级上分别为6.05～19.3g·kg-1和0.61～2.1g·kg-1,水稻土的稳定性有机碳和氮的含量高于旱地黄棕壤.在2～250μm粒级上,稳定性有机碳与有机氮比值(C稳/N稳)的变幅为9.50～22.0,在2μm粒级上分别为7.43～11.54.在2～250μm粒级上,土壤有机碳(氮)的稳定性指数SIC和SIN的变化分别为14.3～50.0和11.9～55.6,在2μm粒级上分别为53.72～88.80和40.64～70.0;旱地黄棕壤的SIC和SIN一般低于水稻土的,水稻土黄棕壤有利于有机碳和氮的保存.各种形态的铁铝氧化物含量与稳定性有机碳(氮)含量呈极显著正相关,且氧化物铁铝含量和稳定性有机碳(氮)含量在黏粒部分最高,即细粒级能保护土壤有机碳(氮).     

再悬浮作用下大环江和刁江沉积物中Pb、Cd和As的释放

该文采用再悬浮模拟装置模拟再悬浮过程中大环江和刁江回水区沉积物中溶解态和颗粒态Pb、Cd和As的含量变化,计算不同扰动强度下的释放通量,以评价再悬浮过程对大环江和刁江水体重金属含量的影响。结果表明,大环江和刁江柱样中上覆水中的DO、p H和SS随扰动均呈增加趋势,3种重金属在颗粒物-水相间的分配系数高于孔隙水-沉积物;再悬浮作用能使沉积物中溶解态重金属迁移进入上覆水中,Pb和Cd迁移能力强于As;再悬浮过程中大环江上覆水中溶解态Pb、Cd及As的总平均通量分别为-0.04、-0.06、0μg/(m~2·min),刁江上覆水中溶解态Pb、Cd及As总平均通量分别为-1.3、-0.01、0.55μg/(m~2·min)。     

密云水库上游铁尾矿各粒级组分重金属研究

以北京市密云水库上游铁矿区为研究对象,研究了尾矿砂中重金属的含量及形态与粒级分布之间的关系。采集铁尾矿样品5件,使用尼龙筛将其划分为4个粒级组分(75、75~180、180~250、250μm),使用ICP-OES测定各粒级组分中重金属元素Mn、Cu、Pb、Zn、Ni和Cd元素的含量,并测定Fe元素含量。并用BCR连续提取法和ICP-OES测定各粒级组分中Mn、Cu、Pb、Zn、Ni和Cd元素不同化学形态的含量。重金属总量随粒度分布特征研究表明,同一样品不同粒级组分中重金属总量有很大差异。Mn和Cu元素主要集中在细粒径(75μm)和粗粒径(250μm)组分中,Pb、Zn和Ni元素在粗粒径组分中含量比较高。各个样品相同的粒级组分中,重金属元素含量从高到低依次为MnZnCuNiPbCd。重金属形态随粒度分布特征研究表明,Mn、Cu、Pb元素可交换态和Mn、Cu、Zn、Ni元素易还原态主要集中在细粒径和粗粒径组分中,环境危害性大。不同矿区尾矿样品相同粒级组分中,重金属形态分布有很大差别。重金属元素总量与p H值之间进行相关性分析表明,Mn、Cu元素两两之间表现出非常显著的相关性(r0.9,P0.01),说明这2种元素有相同或相似的来源。Pb、Zn、Cd元素与其它元素相关性很小,说明Pb、Zn、Cd元素与其它元素来源于不同的矿物成分。     

废电路板热拆解过程中颗粒污染物的排放特征

文章对废旧电路板(WPCBs)加热拆解过程产生的颗粒物、颗粒物所富集的重金属(Sb、Zn、Cr、Pb、Cd、Cu)与多溴联苯醚(PBDEs)进行研究。结果表明,加热拆解过程中排放的PM_(10)颗粒物总浓度、颗粒态重金属总含量、颗粒态∑_(39)PBDEs含量分别为2 243μg/m~3、33.53μg/m~3、9 535 ng/m~3。PM_(2.5)细颗粒占释放颗粒物的63%,其中0.4～0.7μm粒径段的颗粒物浓度最大。PM_(10)中各重金属含量由高到低依次为:SbPbZnCuCrCd,其中Sb和Pb的排放浓度分别为21.86μg/m~3和6.74μg/m~3。Pb、Cd、Cu的质量中值直径(MMAD)2.5μm,主要分布于细颗粒,而Sb、Zn、Cr集中于粗颗粒。PBDEs的排放以四溴联苯醚为主,占78.68%。∑_(39)PBDEs的MMAD值1,低溴代PBDEs主要集中于细颗粒,而高溴代PBDEs主要吸附于粗颗粒。对WPCBs加热拆解过程产生不同粒径颗粒中重金属和PBDEs的分布特征研究,为颗粒物的污染控制和风险评价提供科学依据。     

垃圾焚烧厂排放颗粒物组分粒径分布特征

本研究采用静电低压撞击器(ELPI)采集垃圾焚烧厂排放颗粒物,分析颗粒物中元素和碳组分,对其中OC、EC和重金属元素在14个粒径段的粒径特征进行分析,并建立了垃圾焚烧厂源PM_1、PM_(2.5)和PM_(10)的元素和碳组分成分谱,以期为精细化来源解析提供参考.结果表明,垃圾焚烧厂排放颗粒物的主要组分有Al、Si、S、Ca、Cr、Fe、OC和EC等(质量分数≥1%),其中OC和Ca的含量较高,在PM_(2.5)中的质量分数分别为10. 15%和12. 37%;重金属含量Cr Pb Zn Mn Cu Cd Ni,其中Cr和Pb在PM_(2.5)中的质量分数分别为1. 83%和0. 74%,Cr在PM_1中的质量分数达到3. 53%; OC在2. 39～3. 99μm和6. 68～9. 91μm这2个粒径段的含量达到峰值,分别占OC总含量的15. 02%和20. 45%,但在细颗粒物中的含量高于在粗颗粒物中的含量,EC在细颗粒物中的含量远高于在粗颗粒物中的含量,在0. 382～0. 613μm粒径段占14. 8%; Cr、Mn、Ni、Cu、Zn、Cd和Pb等重金属元素主要富集于细颗粒中.     

不同粒径钨尾砂中重金属的含量及形态研究

以江西省赣南地区牛孜石、画眉坳、西华山钨矿尾砂库为研究对象,采集钨尾砂样品3份,使用标准筛将其细分为7个粒径等级(450μm)。以BCR连续提取法对重金属进行形态提取,ICP-OES测定不同粒径钨尾砂颗粒物中Cr、Mn、Cu、Zn、Cd、As、Pb、Ni重金属各形态的含量。研究结果表明:不同粒径的尾砂中重金属的含量差异明显,Cu、Zn元素在粒径>380μm的颗粒物中含量较高,Cr、Cd、Pb、Ni、Mn元素则在粒径<25μm的颗粒物中有着很高的含量,特别是Pb,该粒径中的含量远高于其他任何粒径区间。重金属形态随尾砂粒径分布表明:不同矿区同一粒径的尾砂各形态重金属所占比例差异明显,但相同的是,粒径大于450μm的颗粒物中Cu、Zn可交换态形式所占比例较高,而粒径小于25μm的极细颗粒物中,可溶态的Ni含量很高,需要采取有效管理措施以遏制可能发生的污染。     

重庆市大气TSP中重金属分布特征

分析了重庆市主城 7区渝中区、九龙坡区、渝北区、南岸区、江北区、沙坪坝区以及清洁对照区 (北碚区 )的总悬浮颗粒物(TSP)监测结果。结果表明 :重庆市 7区中 ,只有渝中区和北碚区达到国家二级标准 ,而九龙坡区、渝北区、江北区、南岸区和沙坪坝区均超过国家二级标准 (<0 .2 mg/ m3) ,说明重庆市颗粒物污染严重 ,空气质量不容乐观。用等离子体发射光谱仪 (ICP- AES)测定分析了 TSP中 5种重金属 ,结果显示 :九龙坡区 Cd和 Pb含量平均值最高分别为 0 .0 1 2 1μg/ m3,0 .4632μg/ m3,Zn的含量渝中区最高为 1 .52 2 5μg/m3,Cu和 Cr的含量沙坪坝区最高分别为 0 .1 2 96μg/ m3、0 .471 9μg/ m3。富集因子法分析结果显示 :主城 7区 TSP中 5种重金属的富集系数均大于 1 0 ,而且大 1～ 3个数量级 ,说明重庆市的重金属污染主要来自于人类活动。     

重庆市典型降雨径流中颗粒物粒径与重金属污染输出特征研究

选择重庆市渝北区水泥路面、沥青路面和屋顶面等3种典型的下垫面,以及中华坊、柏林公园汇水区作为新旧城区的典型代表,收集降雨径流样品,研究山地城市降雨径流中颗粒物粒径分布与重金属含量之间的关系。结果表明:在典型场降雨径流事件中,重金属输出形态主要是以颗粒态形式;初期径流中颗粒态Pb、Ni、Cu、Cd和Cr的百分数均超过60%。水泥路面、沥青路面和屋顶面3个下垫面径流中颗粒物粒径<240μm的体积百分数分别为92.66%、86.16%、91.74%,进入下水道后<240μm的颗粒物的体积百分数减少到81.77%;在柏林公园和中华坊汇水区,径流中颗粒物粒径<240μm的体积百分数分别为84.34%和92.13%。水泥路面和沥青路面径流中重金属含量与颗粒物总量均在0.05水平上显著相关;柏林公园和中华坊径流中重金属(除Cr和Pb外)与颗粒物不存在显著相关性。不同粒径段颗粒物与重金属之间的相关性差异明显,重金属主要是与<52μm粒径段的颗粒物总量极显著相关(Pearson相关系数>0.758),表明重金属主要与细小的颗粒物结合,山地城市降雨径流中重金属的污染控制关键是去除下垫面累积的细颗粒。     

春季东、黄海溶解甲烷的分布和海气交换通量

于2011年3月17日～4月6日对东、黄海海域进行了大面调查,采集了45个站位不同深度的海水样品,对溶解甲烷(CH4)浓度进行了测定,并估算了其海-气交换通量.结果表明,东、黄海表层海水中溶解甲烷的浓度变化范围是2.39～29.67nmol.L-1,底层海水中甲烷浓度范围是2.63～30.63 nmol.L-1,底层浓度略高于表层,表明底层水体或沉积物中存在甲烷的源.春季东、黄海海域表、底层溶解甲烷的分布特征基本一致,即从近岸向远海逐渐降低,主要受长江冲淡水输入和黑潮水入侵的影响.春季东、黄海海域表层海水中CH4饱和度为93%～1 038%.利用Liss and Merlivat公式(LM86)、Wanninkhof公式(W92)和现场测定的风速估算出春季东、黄海海域CH4的海-气交换通量分别为(2.85±5.11)μmol.(m2.d)-1和(5.18±9.99)μmol.(m2.d)-1,根据本研究结果和文献数据初步估算出东海和黄海年释放甲烷量分别为7.05×10-2～12.0×10-2Tg.a-1和1.17×10-2～2.20×10-2Tg.a-1.春季东、黄海海域表层海水中CH4均呈过饱和状态,是大气中CH4的净源.     

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.     

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.