热改性蛇纹石对Pb~(2+)的吸附平衡及动力学研究

采用等温吸附法比较了天然的蛇纹石和700℃热改性处理的热改性蛇纹石对含铅废水的吸附效果,并采用Langmuir、Freundlich方程及Lagrange假二级动力学方程、粒内扩散方程对实验数据进行了拟合,研究了pH对吸附效果的影响,并对2种蛇纹石做了X衍射。结果表明:Pb2+质量浓度大于50mg/L时,热改性蛇纹石吸附效果更好,吸附率在92%以上;天然蛇纹石对Pb2+的吸附符合Freundlich方程和Lagrange假二级动力学方程,以化学吸附为主,有多个控速步骤,热改性蛇纹石对Pb2+的最大吸附量为78.13mg/g;在pH6的条件下,天然蛇纹石对Pb2+的吸附效果更好。     

海带对镉的吸附动力学与热力学研究

采用批量平衡法研究了海带对镉的吸附的动力学与热力学,并采用Lagrange假一级动力学方程、假二级动力学方程、Langmuir等温线方程、Freundlich等温线方程以及Dubimim-Radushkevich等温线方程对实验数据进行了拟合.结果表明,在4种温度下海带对镉的吸附率均随吸附反应时间增加而增大,在60 min时达到最大,此后基本保持不变,随着温度由20℃升高至50℃,其最大吸附率呈下降趋势,由90.2%降至77.5%;海带对镉的吸附动力学符合Lagrange假二级动力学方程;海带对镉的吸附热力学符合Langmuir等温线方程和Dubimim-Radushkevich等温线方程,表明吸附主要发生在海带表面的活性区位,属于单分子层吸附,其吸附平均活化自由能E为11.4 kJ/mol,表明该吸附过程为化学吸附,在4种温度下吉布斯自由能变化量△AG°均为负值,吸附焓变△H°也为负值,表明海带对镉的吸附为放热反应,能自发进行.     

天然和CPB改性沸石对Hg2+的吸附特征

通过静态实验研究溴代十六烷基吡啶(CPB)改性沸石和天然沸石对废水中Hg2+的吸附特性,探讨了吸附动力学、吸附平衡和吸附热力学机制。研究表明:Langmuir方程能较好地描述2种沸石对Hg2+的吸附,CPB改性沸石对Hg2+的吸附率得到显著提高。实验条件下,改性沸石对Hg2+的吸附率从67.5%提高到98.9%,吸附容量从0.521 mg/g提高到3.07 mg/g。利用准一级动力学方程、假二级动力学方程、颗粒内扩散模型和Elovich方程分别对动力学过程进行拟合,发现2种沸石对Hg2+的吸附均满足假二级动力学方程,且离子的颗粒内扩散对整个吸附过程有影响。动力学拟合、D-R方程拟合和热力学研究综合表明:2种沸石对Hg2+的吸附既存在化学吸附又存在物理吸附,吸附吉布斯自由能变(△G0)、焓变(ΔH0)、熵变(ΔS0)均小于0,反应为自发的放热反应,低温有利于吸附的进行。     

十六烷基三甲基溴化铵改性沸石对腐殖酸的吸附性能研究

以十六烷基三甲基溴化铵(CTAB)为改性剂,制备了CTAB改性沸石,并用于对腐殖酸的吸附性能研究。考察了pH、吸附时间及腐殖酸初始浓度对CTAB改性沸石吸附腐殖酸的影响,采用吸附等温方程和反应动力学方程进行拟合分析,并利用扫描电子显微镜(SEM)、X射线光电子能谱仪(XPS)、傅立叶转换红外光谱分析仪(FTIR)对沸石改性前后进行结构表征。结果表明,在温度为25℃、转速为200r/min的条件下,选择pH为7.0、腐殖酸初始质量浓度为10mg/L、吸附时间为180min,此时CTAB改性沸石对腐殖酸的平衡吸附容量为0.16mg/g。相比Freundlich吸附等温方程(R2=0.967),CTAB改性沸石对腐殖酸的吸附更符合Langmuir吸附等温方程(R2=0.998),吸附机制为单分子层吸附。准一级反应动力学方程和准二级反应动力学方程均可以描述CTAB改性沸石对腐殖酸的吸附(R2=0.978)。吸附实验后的CTAB改性沸石上出现了甲基、亚甲基、羟基与羰基伸缩振动吸收峰,说明沸石已负载了CTAB,且腐殖酸已被CTAB改性沸石吸附。     

改性粉煤灰合成沸石对甲基橙的吸附动力学

以粉煤灰(FA)为原料,采用水热晶化一步法制备了Na P1型沸石(ZFA),对合成产物的结构进行了表征,并采用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对其进行改性。通过静态吸附实验,研究了改性后Na P1型沸石(MZFA)对水溶液中甲基橙的吸附特性,从动力学角度探讨了吸附机理。结果表明,在所研究的浓度条件下,改性Na P1型沸石对甲基橙的吸附符合Langmuir等温吸附方程,在25℃时,静态饱和吸附量(Qm)为64.76 mg/g。动力学分析表明,改性Na P1型沸石对溶液中甲基橙的吸附符合准二级动力学模型。     

天然和CPB改性沸石对Hg^2＋的吸附特征

通过静态实验研究溴代十六烷基吡啶（CPB）改性沸石和天然沸石对废水中Hg^2＋的吸附特性,探讨了吸附动力学、吸附平衡和吸附热力学机制。研究表明：Langmuir方程能较好地描述2种沸石对Hg^2＋的吸附,CPB改性沸石对Hg^2＋的吸附率得到显著提高。实验条件下,改性沸石对Hg^2＋的吸附率从67．5％提高到98．9％,吸附容量从0．521mg／g提高到3．07mg／g。利用准一级动力学方程、假二级动力学方程、颗粒内扩散模型和Elovich方程分别对动力学过程进行拟合,发现2种沸石对Hg^2＋的吸附均满足假二级动力学方程,且离子的颗粒内扩散对整个吸附过程有影响。动力学拟合、D-R方程拟合和热力学研究综合表明：2种沸石对Hg^2＋的吸附既存在化学吸附又存在物理吸附,吸附吉布斯自由能变（△G^0）、焓变（△H^0）、熵变（△S^0）均小于0,反应为自发的放热反应,低温有利于吸附的进行。     

氢氧化钠改性沸石对水中Cu~(2+)的吸附特性研究

利用氢氧化钠对天然沸石进行改性,将天然沸石和改性沸石用于吸附去除水中的Cu~(2+),分析了p H、温度、Cu~(2+)初始浓度、吸附时间对Cu~(2+)吸附性能的影响,并对吸附过程的吸附等温模型及吸附动力学进行研究。结果表明,改性沸石对Cu~(2+)的吸附性能明显优于天然沸石,当沸石投加量为10 g/L,Cu~(2+)为200 mg/L,p H为6.67,温度为50℃时,天然沸石和改性沸石对Cu~(2+)的吸附量分别为2.02、2.69 mg/g。Langmuir和Freundlich吸附等温模型均能较好地描述两种沸石对Cu~(2+)的吸附过程。天然沸石对Cu~(2+)的吸附行为更符合准一级动力学方程,而准二级动力学方程对改性沸石的吸附行为拟合度更好。两种沸石对Cu~(2+)的吸附均为非均相吸附,且内扩散过程不是唯一的速控步骤。     

海水改性沸石处理氨氮废水

沸石因具有独特的架状结构而表现出良好的选择吸附和离子交换性能,在废水处理中被广泛应用,但吸附容量偏低,需要进行改性。针对天然沸石的局限性,研究了不同改性方法对氨氮吸附的影响,确定了最佳的沸石改性方法,并进行了吸附等温模型,吸附动力学研究。结果表明,采用高温300℃焙烧后再用预处理后的海水浸泡24 h改性沸石去除氨氮效果最佳。当活化沸石投配量为10 g/L,接触时间为150 min,进水氨氮浓度为37.91 mg/L时,沸石对氨氮吸附容量为4.08 mg/g,氨氮去除率为90.45%;沸石及改性沸石对氨氮的吸附等温线符合Langmuir方程和准一级动力学方程。用海水来改性沸石的方法,不仅可提高沸石对氨氮的吸附容量和吸附速度,而且无任何添加药剂,具有简单易行、费用低廉的优点,为沸石在水处理工程中的应用提供技术支撑。     

NaCl改性沸石对氨氮吸附性能的研究

采用NaCl溶液对天然沸石进行改性,考察了NaCl浓度、温度及沸石用量对改性效果的影响。通过表面特征分析、吸附机制分析、吸附等温试验和吸附动力学试验,进一步比较了天然沸石和改性沸石对氨氮的吸附性能。结果表明,在NaCl溶液为6%(质量分数)、温度为303 K、天然沸石用量为15 g(以100 mL的NaCl溶液计)的优化条件下,改性沸石对氨氮的吸附效果最佳。扫描电子显微镜(SEM)和比表面积(BET)分析可知,沸石经改性后表面变粗糙,平均吸附孔径变小,比表面积变大。2种沸石对氨氮的吸附过程均可用Langmuir、Freundlich吸附等温方程较好地拟合,在温度为303 K时,改性沸石比天然沸石单分子层饱和吸附量增幅为34%以上。颗粒内扩散是沸石吸附氨氮的限制性因素,其吸附动力学较符合准二级反应动力学方程,拟合结果表明改性沸石具有更好的动力学性能,其吸附速率常数略大于天然沸石。     

硅烷化改性沸石对重金属离子的吸附性能

制得一种用于重金属废水处理的新型硅烷化改性沸石吸附剂,成本低、效果显著且稳定。通过对改性沸石表征,分析了改性对沸石结构的影响。结果表明,改性一定程度降低了原沸石的晶体特征,但基本上保持了其结构组成;硅烷化改性成功地在沸石上接枝了氨基。对硅烷化沸石的特性研究,得出硅烷化沸石对Ni2+、Cu2+、Zn2+和Pb2+吸附最佳投加量为1、1、1.6和0.6 g/L,且此时对4种离子的去除率也较好;吸附动力学研究得出,其吸附过程可用二级动力学方程较好地拟合;吸附达到平衡时,4种金属离子的平衡吸附量分别为11.23、17.41、15.45和59.42 mg/g;硅烷化沸石对金属离子的吸附行为更符合Langmuir模型,为化学吸附;在酸性条件下(pH=2～6),硅烷化沸石仍保持一定的吸附能力,具有一定的耐酸性。     

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.