金属氧化物催化剂上吡啶催化燃烧

为了研究催化燃烧法净化挥发性有污染物的可能性,考察了金属氧化物催化剂上吡啶的氧化活性及氧化过程ＮＯｘ控制能力,吡啶氧化产物ＮＯｘ随反应温度升高呈现极大值。催化剂的氧化活性ＮＯｘ控制能力呈正比关系。     

三元催化转化器与空燃比的关系

车辆通常应用的三元催化转化器，大多是将催化元素钯（Ｐｄ）、铂（Ｐｔ）和铑（Ｐｈ）贵金属涂敷在蜂窝状的陶瓷载体上，制成具有不锈钢外壳的罐状物，安装在车辆排气管上。当车辆排放的废气通过三元催化转化器时，可提供较大的反应面积，使ＨＣ，ＣＯ和ＮＯｘ发生氧化和还原反应。其工作机理为：还原反应ＮＯｘ＋ＣＯＮ２＋ＣＯ２ＮＯｘ＋ＨＣＮ２＋ＣＯ２＋Ｈ２ＯＮＯｘＮ２＋Ｏ２氧化反应ＨＣ＋Ｏ２ＣＯ２＋Ｈ２ＯＣＯ＋Ｏ２ＣＯ２从机理分析看出，三元催化转化器的氧化和还原反应将ＮＯｘ，ＨＣ和ＣＯ有害物质转换成无害物质。大量的机…     

三元催化转化器与空燃比的关系

车辆通常应用的三元催化转化器，大多是将催化元素钯（Ｐｄ）、铂（Ｐｔ）和铑（Ｐｈ）贵金属涂敷在蜂窝状的陶瓷载体上，制成具有不锈钢外壳的罐状物，安装在车辆排气管上。当车辆排放的废气通过三元催化转化器时，可提供较大的反应面积，使ＨＣ，ＣＯ和ＮＯｘ发生氧化和还原反应。其工作机理为：还原反应ＮＯｘ＋ＣＯＮ２＋ＣＯ２ＮＯｘ＋ＨＣＮ２＋ＣＯ２＋Ｈ２ＯＮＯｘＮ２＋Ｏ２氧化反应ＨＣ＋Ｏ２ＣＯ２＋Ｈ２ＯＣＯ＋Ｏ２ＣＯ２从机理分析看出，三元催化转化器的氧化和还原反应将ＮＯｘ，ＨＣ和ＣＯ有害物质转换成无害物质。大量的机…     

SO2和NOx对大气的污染及其净化处理

燃烧等带来的ＳＯ２、ＮＯｘ是酸雨的主要来源，当ＳＯ２排放量正逐渐得到控制时，ＮＯｘ却还在增长，因而应推广较成熟的选择化还原除ＮＯｘ法和加强氧化气氛下烃类化合物还原ＮＯｘ的研究，也应该寻找比石灰石－石膏法更好的除ＳＯ２措施。     

煤燃烧过程中NOx产生机制及影响因素

煤燃烧产生的ＮＯｘ有三个来源，热力型ＮＯｘ快速型ＮＯｘ和燃料型ＮＯｘ，在１３００℃下主要是燃料型ＮＯｘ。燃煤过程中ＮＯｘ的形成是分两步进行，首先燃料中的杂环氮化物受热分解，产生ＮＨ３或ＨＣＮ，随挥发物释放出来，氧化生成ＮＯｘ残留在煤焦中的氮在煤焦燃烧时生成ＮＯｘ。挥发分中的ＮＨ３、ＨＣＮ同时也可以还原ＮＯｘ气体，研究表明脱硫用的石灰石、ＣａＯ或多或少地增加ＮＯｘ的排放，认为是ＣａＯ催化了ＮＯｘ形成     

燃气火焰中热力型NOx的生成与控制

燃气火焰中热力型ＮＯｘ以ＮＯ为主，以ＮＯ为主，燃烧温度对ＮＯ生成起决定作用，空气系数也主要通过改变燃烧温度影响ＮＯｘ生成。燃烧温度大于１８００Ｋ时，有较多ＮＯ生成。降低燃烧温度与保持高效燃烧相协调是控制ＮＯｘ生成的关键。     

上海市NOx分布状况及其影响因素

以一种简易可靠的大气ＮＯｘ测量方法，大范围地调查了上海市区的ＮＯｘ浓度状况。结果表明，上海市ＮＯｘ浓度分面状况，在不同性质的街区，不同地段，不同道路之间，存在明显差异，居民区大气中ＮＯｘ的浓度可达到国家一级标准要求，但市区各道路网超标严重，平均是一级标准的１．７倍，道路网ＮＯｘ的分布总体呈东南低，北和西北高的梯次。影响城市ＮＯｘ浓度分布的主要因素有：交通、风力、地形、绿化等，在城市建设规划时，应充     

国外动态

利用混合技术控制氮氧化物排放美国ＥｎｔｒｏｐｙＴｅｃｈｎｏｌｏｇｙ &ＥｎｖｉｒｏｎｍｅｎｔａｌＣｏｎｓｕｌ ｔａｎｔｓ，ＬＰ(ＥＴＥＣ)介绍了一种新的混合技术 ,它能像选择性催化还原 (ＳＣＲ)方法一样提供同样的ＮＯｘ的工作特性。这一新技术结合ＥＴＥＣ的废气循环(ＩＦＧＲ)和燃烧改进 (Ｃ -Ｍｏｄｓ)方法 ,这种方法使ＮＯｘ达到最低排放率。通常在燃烧天然气和轻油时生成的ＮＯｘ来自大气中氮的高温氧化 (或固氮 )。这反应能被模拟成为温度的指数函数和氧浓度的平方根函数。混合的概念控制这二个关键参数———燃烧过程中的温…     

广州大气NOx浓度影响因素的灰色关联分析

文章运用灰色系统理论中的关联分析方法分析与广州大气ＮＯｘ浓度有关的几个因素。结果表明，广州市区平均车流量和道路面积是影响ＮＯｘ浓度水平的两个最主要因素，文章用灰我ＧＭ（１，１）模型预测了ＮＯｘ浓度的变化趋势，最化提出了控制和治理ＮＯｘ污染的相应对策。     

煤燃烧过程中影响NOx转化的因素探讨

利用管式沉降炉对煤粉燃烧过程中的反应温度、初始氧浓度、反应时间、煤的挥发分及含氧量对燃料氮向ＮＯｘ转的影响进行了试验研究，摸清了反应的规律，找出了影响转化的显著因素。     

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

ＲｅｍｏｖａｌｏｆｈｅａｖｙｍｅｔａｌｓｆｒｏｍｓｅｗａｇｅｓｌｕｄｇｅｂｙｌｏｗｃｏｓｔｉｎｇｃｈｅｍｉｃａｌｍｅｔｈｏｄａｎｄｒｅｃｙｃｌｉｎｇｉｎａｇｒｉｃｕｌｔｕｒｅＷｕＱｉｔａｎｇ，ＮｙｉｒａｎｄｅｇｅＰａｓｃａｓｉｅ，ＭｏＣｅｈｕｉＦ...     

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.