纳米Pd／Fe双金属颗粒对单氯酚及二氯酚的还原脱氯

采用改进液相化学还原法制备纳米Pd／Fe双金属颗粒，研究其钯化率为0．045％和0．135％的条件下分别对3种单氯酚（2-CP、3-CP和4-CP）和3种二氯酚（2，3-DCP、2，4-DCP和2，6-DCP）的脱氯反应。结果表明，合成的纳米Pd／Fe颗粒分散性良好，粒径分布介于25～40nm。纳米Pd／Fe双金属颗粒对单氯酚及二氯酚具有良好的去除效果，3种单氯酚和3种二氯酚的脱氯难易程度分别为2-CP〉4-CP〉3-CP和2，6-DCP〉2，4-DCP〉2，3-DCP，脱氯反应均符合拟一级反应动力学方程。通过还原脱氯实验揭示了分子中氯原子的化学环境对还原脱氯过程具有明显影响。     

纳米钯?铝双金属对水中3-氯酚的脱氯降解研究

采用置换沉积法制备了纳米钯/铝双金属催化剂,氢解还原去除水相中难降解有毒有机物3-氯酚(3-CP),考察了溶液pH、钯负载量、纳米钯/铝双金属投加量、反应温度对脱氯效果的影响并解析相关反应机制。结果表明:(1)初始pH 3.0时,沉积液中93.25%(质量分数,下同)～96.67%的钯可有效负载于铝材上。(2)在pH为3.0、纳米钯/铝双金属投加量为2g/L、钯负载量为1.16%(质量分数)、反应温度为25℃下降解初始摩尔浓度为0.389mmol/L的3-CP,反应终了时脱氯率在99%以上。利用纳米钯/铝双金属降解氯代有机污染物具有高效低耗的优势,在实际应用上具有较好的前景。     

Ni/Fe双金属降解四氯化碳和四氯乙烯的对比试验

以四氯化碳(CT)和四氯乙烯(PCE)为目标污染物,以批试验方法研究Ni/Fe双金属对CT和PCE的还原性脱氯.结果表明:Ni/Fe双金属可有效去除水中的CT和PCE;Ni/Fe双金属对CT和PCE的降解反应均符合准一级反应动力学方程;在相似的反应条件下,Ni/Fe双金属对CT和PCE脱氯的反应速率常数(kobs)之比为1.48和1.67,说明Ni/Fe双金属对CT的脱氯速率要快于对PCE的脱氯速率;Ni/Fe双金属可对PCE完全脱氯,但对CT脱氯过程中产生少量三氯甲烷(TCM).     

钯/铝双金属体系对3-氯酚的脱氯降解

研究了钯/铝双金属体系对水相中3-氯酚的催化脱氯降解效果,通过置换沉积制备了钯/铝双金属颗粒,考察了该双金属颗粒的稳定性以及溶液pH和钯负载量对脱氯效果的影响。结果表明,pH在4.0以下的酸性条件,钯负载量在1.43%时,可实现水相中3-氯酚的有效脱氯,反应30 min后0.389 mmol/L的3-氯酚转化率可达99%以上,产物主要为苯酚,而钯/铝颗粒在重复测试中能保持较好的稳定性,这与铝基材表面自发形成的氧化膜有关。钯/铝材料表征的结果表明,钯颗粒高度分散在铝基材表面,并极大地提高了铝基材的表面积,从而有助于后续的脱氯反应。     

粉煤灰沸石负载Ce^3＋／TiO2光催化降解水中的菲和荧蒽

以钛酸四丁酯为前驱体，粉煤灰合成沸石为载体，采用溶胶-凝胶方法，在低温条件下制备了稀土铈掺杂的TiO2光催化剂。利用SEM—EDS、XRD、FTIR对催化剂进行了分析和表征。以高压汞灯为灯源，对多环芳烃菲、荧蒽的降解进行了研究。实验考查了稀土铈掺杂质量分数、催化剂用量、溶液pH、目标物初始质量浓度等因素对光催化降解的影响，研究了其光降解动力学。结果表明，当稀土铈含量为0．5％，催化剂用量为3g／L，pH偏碱性时，催化效果最佳。光催化反应符合Langmuir—Hinshelwood动力学规律，菲、荧蒽的降解过程符合一级反应动力学，反应速率常数分别为0．0126min^-1，0．0099min^-1。     

UV-Vis/Fe(Ⅲ)/H2O2体系对水中雌酮的光降解

以250W照明金属卤化物灯为光源,研究了水中雌酮（E1）在UV-Vis／Fe（Ⅲ）／H2O2体系中的光降解;考查了初始pH、Fe（Ⅲ）、H2O2、E1初始浓度对E1光降解的影响。结果表明,UV-Vis／Fe（Ⅲ）／H2O2体系能有效地光降解E1,在[Fe（Ⅲ）30-20．8μmol／L、[H2O2]0=1664μmol／L、pH=3．0时,光照160min,18．5btmol／L E1的光降解率可达98．4%;在pH3．0～8．0范围内,pH初始值越小,E1降解率越大,反应初始速率越大;实验条件下,Fe（Ⅲ）、H2O2初始浓度越大,E1降解率越大,反应初始速率越大;E1初始浓度越低,E1降解率越大,反应初始速率越小。pH=3．0,实验浓度范围内的表观动力学方程为：dCE1／dt=0．00093[H2O2]^0.47[Fe（Ⅲ）]^0.62[E1]0.24;Fe（Ⅲ）是影响反应速率的主要浓度因素。     

微米Cu／Fe对污染土壤洗脱液中有机氯农药的降解

以表面活性剂TritonX-100（TX-100）为洗脱剂，某有机氯农药（organochlorinepesticides，OCPs）污染场地土壤为对象，七氯、氯丹和灭蚁灵为目标污染物，研究微米Cu／Fe双金属对污染土壤洗脱液中OCPs的降解效果。考察了洗脱液中OCPs初始浓度、洗脱液pH值、微米零价铁加入量和cu负载量对Cu／Fe去除OCPs效果的影响。结果表明，微米Cu／Fe可以有效的去除土壤洗脱液中目标污染物。当微米零价铁加入量为1．0g（25g／L），cu负载量为1．0％，洗脱液pH值为6．89时，Cu／Fe对2号土壤洗脱液中七氯、γ-氯丹、α-氯丹和灭蚁灵的去除效果最好，去除率分别为100．0％、99．3％、80．8％和71．1％。洗脱液中OCPs初始浓度越低，微米零价铁加入量越大，Cu／Fe对OCPs去除率越高；偏酸性条件有利于Cu／Fe对γ-氯丹和灭蚁灵的去除，而α-氯丹在中性条件下去除效果最好；1号土壤和2号土壤洗脱液的最佳铜负载量分别为2．O％和1．0％。     

羧甲基纤维素改性纳米钯铁双金属去除水中2,4-二氯苯酚的影响因素及机理

利用液相还原法制备了纳米零价铁(nZVI)、纳米钯铁双金属(Pd/Fe)、羧甲基纤维素(CMC)改性nZVI(CMC-Fe)和CMC改性钯铁双金属(CMC-Pd/Fe)4种铁基纳米材料，并用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对其进行了表征。研究了这4种材料对水中2,4-二氯苯酚(2,4-DCP)的表观去除率，考察了铁基纳米材料投加量、Pd负载量、溶液初始pH及污染物浓度等因素对CMC-Pd/Fe去除2,4-DCP的影响，并探讨了可能的作用机理。结果表明，在4种材料中，CMC修饰的CMC-Pd/Fe的分散性最好，粒径明显小于未用CMC修饰的nZVI和Pd/Fe。4种材料对2,4-DCP的表观去除率为CMC-Pd/Fe>CMC-Fe>Pd/Fe>nZVI。随着CMC-Pd/Fe投加量和Pd负载量的增加，CMC-Pd/Fe对2,4-DCP的表观去除率增大，而随着2,4-DCP浓度的升高，CMC-Pd/Fe对2,4-DCP的表观去除率下降。当溶液初始pH=3、5和7时，CMC-Pd/Fe对2,4-DCP的表观去除率分别为94.34%、99.50%和96.62%;...     

零价铁对土壤中2-氯硝基苯的还原作用

在常温常压下利用零价铁(Fe0)还原土壤中的2-氯硝基苯(o-CNB),研究反应条件对还原率的影响以及反应产物在不同反应阶段的变化.GC-MS检测结果显示,o-CNB在还原过程中先生成2-氯亚硝基苯,最终生成2-氯苯胺.反应时间、Fe0用量、温度和土壤初始pH值等均会对o-CNB的还原率产生影响,其中土壤初始pH值控制在偏酸性、土壤温度较高时能显著提高其还原率.当o-CNB的初始浓度约为2.5×10-6 mol/g,Fe0加入量是25 mg/g时,经过4 h反应,o-CNB的还原率可达99%以上.此外,还初步探讨了Fe0还原o-CNB的反应机理.     

超声波和零价铁联用对氯代苯酚脱氯降解作用的研究

采用超声波和零价铁联用对氯代有机物3氯苯酚(CP)、2,4-二氯苯酚(DCP)和2,4,6-三氯苯酚(TCP)模拟废水进行了脱氯处理研究。以单因素法, 考察了铁粉初始投加量、溶液的初始浓度、超声波功率和溶液的pH值等因素对氯代酚降解的影响，并探讨了降解反应动力学。结果表明，超声波和零价铁联用对氯酚具有显著的降解效果，当水样初始浓度为25 mg/L，溶液pH呈弱酸性，超声波功率为200 W时，氯代酚的脱氯效率达到最大值。降解反应符合准一级反应，CP、DCP和TCP的反应速率常数分别0.0613 h^-1、0.374 h^-1和0.197 h^-1。     

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.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

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.