铈改性Al2O3担载Pd催化剂的CO氧化性能研究

浸渍法制备了Al₂O₃+CeO₂为载体的Pd催化剂,对制备中各因素对催化剂效果的影响作了初步研究。考察了活性组分含量与催化剂性能的关系以及焙烧温度、水蒸气对催化剂活性的影响。结果表明,稀土Ce元素的存在使催化剂的性能得到明显改善。制备过程中焙烧步骤对催化剂的活性影响很大,催化剂制备必须高于600℃焙烧。     

Mn的氧化价态对Mn/γ-Al2O3催化剂催化臭氧氧化气相低浓度甲苯的影响

采用共沉淀法,以Al₂O₃为载体制备Mn/γ-Al₂O₃和Mn-Ce/γ-Al₂O₃催化剂,并分别在N₂气氛和O₂气氛下焙烧。采用固定床连续流动反应器,研究所制备催化剂在室温条件下催化臭氧氧化甲苯的性能。通过XRD、XPS和FTIR等手段对催化剂的结构和组成进行表征。结果表明,Mn/γ-Al₂O₃催化剂具有良好的催化臭氧氧化甲苯和催化臭氧自身分解的性能,共沉淀法制备催化剂的最佳Mn负载量为20%。O₂气氛焙烧和Ce的加入,可以有效提高催化剂的活性和寿命。原因是O₂气氛焙烧和Ce的加入可以提高Mn的氧化价态。催化剂失活的主要原因是有机副产物在催化剂表面吸附堆积,失活催化剂在550℃、空气气氛下焙烧可恢复催化性能。     

Co3O4/介孔分子筛催化剂对苯催化完全氧化的研究

分别以介孔分子筛MCM-41、MCM-48、SBA-15为载体,采用等体积浸渍法制备了氧化钴/介孔分子筛催化剂,利用N₂吸附、X射线衍射、程序升温还原等技术对催化剂进行了表征,考察了Co₃O₄的负载量及载体的孔结构对催化剂完全催化氧化苯的性能的影响。结果表明,Co₃O₄的负载量为20%时,催化剂的催化活性最好;载体的孔径和催化剂的可还原性能是影响催化活性的主要因素,催化剂活性顺序为Co₃O₄ /SBA-15> Co₃O₄ /MCM41> Co₃O₄ /MCM-48。     

用H2O2/Fe3+处理高浓度含甲醛废水的研究

研究采用H₂O₂/Fe³⁺催化氧化处理高浓度含甲醛废水,探讨了双氧水和催化剂投加量、反应pH及反应温度等操作条件对处理效果的影响,并通过酸溶解回用失活催化剂。结果表明,较优的操作条件为：H₂O₂/COD（质量比）=2.2～2.6,Fe³⁺/H₂O₂（摩尔比）=0.048～0.058,反应pH 1.80～2.68,反应温度50℃,反应时间40 min;在上述操作条件下,甲醛去除率达到99%以上,COD去除率达到85%以上。失活的催化剂可通过稀酸溶解后循环使用,其效果与三价铁盐作催化剂的基本相同。采用H₂O₂/Fe³⁺处理含甲醛废水具有比采用H₂O₂/Fe³⁺较优的效果。     

锰铜复合催化剂常温催化氧化NO

采用浸渍法,以γA1₂O₃为载体制备了常温下对NO具有良好催化氧化活性的Mn-Cu复合催化剂。系统考察催化剂组分、焙烧温度等与催化剂性能的关系,结果显示200℃干燥所得催化剂的活性最好,催化剂15%Mn-24%Cu/Al₂O₃在常温下对NO的催化氧化效率达到50%以上。XRD分析表明,催化剂活性组分为Cu（OH）Cl,且随反应时间延长催化性能下降,其物相由Cu（OH）Cl转变为活性较低的Cu₂（OH）₃Cl相。     

类Fenton氧化技术去除榨菜生产废水COD的研究

研究了紫外光照射下类Fenton试剂对榨菜生产废水COD的去除,考察了光照时间、初始pH值、过氧化氢用量、FeCl₃·6H₂O用量等因素对榨菜废水中COD去除率的影响。结果表明,光照时间60 min,初始pH值3,H₂O₂（30%）的用量为理论值的120%,c₀(H₂O₂)∶c₀［Fe(Ⅲ)］=11.6∶1.0时,COD去除率效果为最佳,达到79%。当H₂O₂投加总量不变时,去除率随着投加次数的增多而增大。     

锰掺杂WO3-TiO2复合光催化剂的制备及其性能研究

溶胶-凝胶和浸渍相结合的方法制备锰掺杂WO₃-TiO₂复合光催化剂，RXD表征，考察WO₃和Mn²⁺掺入量、焙烧温度、焙烧时间及催化剂用量对光催化降解甲基橙的影响。结果表明，500℃焙烧2h，掺杂量n_{（Mn²⁺）}∶n_（WO3）∶n_（TiO2）＝0.8∶1∶100时，光催化活性最高，光催化降解甲基橙溶液，120min后，降解率达90%, 比单纯 TiO₂的光催化活性提高81%。     

微气泡曝气 O3/ H2O2处理 RO 浓水的效能及影响因素简

采用O₃/H₂O₂高级氧化工艺处理炼油厂反渗透（RO）浓水,用溶气泵加压溶气并产生微气泡强化传质,确定装置运行条件,考察气体中臭氧浓度、H₂O₂/O₃初始摩尔比、pH和温度对O₃/H₂O₂处理RO浓水效果的影响,并对RO浓水处理效能进行研究。结果表明,随着气体中臭氧浓度的增加,COD的去除率基本呈线性增加;加入适当量H₂O₂能提高臭氧氧化RO浓水的效果,H₂O₂/O₃初始摩尔比在0~0.8范围内,COD的去除率先增加后下降,H₂O₂/O₃初始摩尔比为0.5时COD去除率最大;pH从6.84增加到9.01,COD去除率逐渐增大,pH为10.03时COD去除率反而降低;在14~28℃范围内,温度低时,升高温度COD去除率增加较大,温度较高时,升高温度对COD去除率的影响较小。为考察该工艺的稳定性,在H₂O₂/O₃初始摩尔比为0.5、溶液pH为8~9、臭氧浓度为80~100 mg/L、温度为10~28℃条件下,对COD为90~140 mg/L的RO浓水氧化处理4~10 h,出水COD维持在39.9~49.9 mg/L,达到《城镇污水处理厂污染物排放标准（GB 18918-2002）》中的一级A标准;去除1 g COD消耗O₃ 1.4~3.3 g,消耗O₃与H₂O₂的总氧量为2.2~4.4 g。     

CuO/γ-Al2O3的制备及其湿式催化氧化性能研究

针对常温常压的废水双氧水催化氧化,采用浸渍法制备CuO/γ-Al₂O₃催化剂,利用比表面积、XRD手段表征了制备工艺对催化剂的影响,以模拟苯酚废水为研究对象考察催化剂的催化性能。研究表明,焙烧温度和活性组分含量等显著影响催化剂的性能,催化剂对双氧水催化氧化苯酚溶液具有较高的催化活性。     

催化湿式氧化法处理高浓度唑螨酯生产废水的研究

对唑螨酯生产过程中产生的高浓度实际废水采用催化湿式氧化技术在鼓泡式固定床反应器连续反应装置上进行处理。实验表明,制备的复合负载型催化剂CuO-MnO₂-Cr₂O₃/ZrO₂-CeO₂在处理该废水时具有较好的催化活性。通过对反应温度、反应压力、反应空速、气液比和进水pH等工艺条件的考察,得出最佳的工艺条件为：反应温度=220℃,反应压力=5.8 MPa,空速＝1.8 h^-1,V（气）∶V（水）＝260∶1,进水pH＝9,在此条件下COD去除率达到95.2％。     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.