可见光/H2 O2/海藻酸铁非均相催化降解吖啶橙的研究

由海藻酸钠和氯化铁反应制备了海藻酸铁凝胶小球催化剂,考察了该催化剂的吸附和可见光下催化降解吖啶橙的性能.结果表明催化剂的吸附能力随pH升高而提高,且催化剂用量为40个凝胶小球时,可见光下吖啶橙能够在较宽pH值范围内脱色,脱色速率随H2O2的用量增加而增加,该反应符合Arrhenius规律,其表观活化能为49.6 kJ/mol.自由基清除剂的加入不会降低脱色速率,表明催化反应不是羟基自由基的机理,而与高活性的类{ Fe(Ⅳ)=O}高价铁中间产物有关.     

交联壳聚糖/Cu_2O复合颗粒可见光催化脱色活性艳红

利用壳聚糖对金属离子的吸附和螯合作用,通过简单的液相沉淀-还原过程一步原位合成了交联壳聚糖/Cu2O复合粒子。X射线衍射(XRD)和红外(FT-IR)测试结果表明,壳聚糖与Cu2O纳米微粒能有效复合。以活性艳红X-3B溶液为模拟印染废水,采用Langmuir-Hinshelwood假一级方程模拟交联壳聚糖/Cu2O复合粒子光催化脱色反应的动力学行为,从动力学角度系统研究染料初始浓度、反应体系pH、催化剂用量和反应体系气氛等因素对复合粒子可见光催化脱色反应速率的影响。结果表明,当染料溶液浓度较低时,光催化过程可视为假一级反应。降低活性艳红X-3B初始浓度和pH,增加催化剂用量和反应体系的含O2量都可显著增加光解脱色反应速率常数。相同条件下,与纯Cu2O相比,交联壳聚糖/Cu2O复合粒子对X-3B呈现出更好的吸附性和更高的可见光催化活性。     

CuO/TiO2-H2O2可见光催化亚甲基蓝脱色效果及影响因素研究

以水解法制备的锐钛矿型TiO2为载体,制备了CuO/TiO2型光催化剂.以亚甲基蓝为对象,在可见光照射下研究了H2O3加入量、pH值和催化剂投加量对脱色效果的影响,同时与改性前的TiO2催化剂进行了脱色效果的对比.结果表明亚甲基蓝在碱性条件下能较好脱色,H2O2用量和CuO/TiO2催化剂投加量分别为每1 000 mL反应液各加入10 mL和0.1 g时脱色最好;另外,TiO2催化剂也在碱性条件下能较好脱色,H2O2用量和催化剂投加量分别为每1 000 mL反应液各加入12.5 mL和0.1 g时脱色最好.最优条件下对比实验表明,CuO/TiO2型催化剂在可见光照射下具有很高的催化活性,亚甲基蓝2 h脱色率达到88%,远好于改性前的TiO2和Degussa P25催化剂.     

交联壳聚糖／Cu2O复合颗粒可见光催化脱色活性艳红

利用壳聚糖对金属离子的吸附和螯合作用,通过简单的液相沉淀一还原过程一步原位合成了交联壳聚糖／Cu2O复合粒子。x射线衍射（XRD）和红外（FT—IR）测试结果表明,壳聚糖与Cu2O纳米微粒能有效复合。以活性艳红X-3B溶液为模拟印染废水,采用Langmuir-Hinshelwood假一级方程模拟交联壳聚糖／Cu2O复合粒子光催化脱色反应的动力学行为,从动力学角度系统研究染料初始浓度、反应体系pH、催化剂用量和反应体系气氛等因素对复合粒子可见光催化脱色反应速率的影响。结果表明,当染料溶液浓度较低时,光催化过程可视为假一级反应。降低活性艳红X-3B初始浓度和pH,增加催化剂用量和反应体系的含O2量都可显著增加光解脱色反应速率常数。相同条件下,与纯Cu2O相比,交联壳聚糖／Cu2O复合粒子对X-3B呈现出更好的吸附性和更高的可见光催化活性。     

H2O2处理酸性大红GR染料废水的研究

通过对废水pH值、H2O2用量、催化剂用量、反应时间、反应温度等工艺条件的考察,确定了H2O2催化氧化处理酸性大红染料废水的最佳工艺条件pH 4、H2O2用量6 mL/L、催化剂用量3 g/L、反应时间100 min、反应温度70℃.在该条件下,COD和色度的去除率分别为76.7%和99.4%;通过反应前后的紫外-可见光光谱分析表明,H2O2催化氧化处理酸性大红GR染料废水有比较好的效果,为该工艺处理酸性大红GR染料废水提供了科学依据.     

H2O2处理酸性大红GR染料废水的研究

通过对废水pH值、H2O2用量、催化剂用量、反应时间、反应温度等工艺条件的考察，确定了H2O2催化氧化处理酸性大红染料废水的最佳工艺条件：pH4、H2O2用量6mL／L、催化剂用量3g／L、反应时间100min、反应温度70℃。在该条件下，c0D和色度的去除率分别为76．7％和99．4％；通过反应前后的紫外一可见光光谱分析表明，H2O2催化氧化处理酸性大红GR染料废水有比较好的效果，为该工艺处理酸性大红GR染料废水提供了科学依据。     

N掺杂TiO2可见光催化降解有机物机理研究

实验研究了掺杂N的TiO2光催化剂在可见光下对有机物的降解机理,研究方法有:加入自由基俘获剂探索对反应速率的影响、有机物降解过程TOC与脱色比较,化学探针法测定了实验中存在的HO.。结果表明,有机物在脱色的同时苯环也在断裂,说明有机物的降解是受无选择性的氧化剂攻击而完成;除亚甲基蓝以外,加入自由基俘获剂对可见光反应速率均有抑制现象,证明自由基的攻击是有机物可见光催化降解的主要途径。分别以二甲基亚砜和水杨酸为分子探针,实验结果证明了光催化反应系统中存在HO.物种,前者与HO.反应形成特定的偶氮结构有机物在425 nm处有吸收,后者与HO.反应生成2,3-二羟基苯甲酸和2,5-二羟基苯甲酸。亚甲基蓝、苯酚和水杨酸经5 h的可见光催化降解后,其TOC分别降低了62.8%、78.9%和96.0%,说明掺杂N的TiO2有较强的可见光催化降解有机物能力。     

UV/H2O2/草酸铁络合物光降解邻苯二甲酸二丁酯研究

研究了邻苯二甲酸二丁酯(DBP)在UV/H2O2/草酸铁络合物体系中的光降解.结果表明,UV/H2O2/草酸铁络合物能有效地光解DBP;在pH值为4时,DBP光解速率最快,中性和碱性条件下光解效率降低;DBP的光解速率随H2O2浓度的升高而增大,但H2O2浓度较大时,其对·OH的清除作用使DBP的光解速率减慢;[Fe3 ]/[C2O42]＜1/10,DBP光解速率随Fe3 浓度增大明显提高,[Fe3 ]/[C2O42]＞1/10时,引起DBP光解速率的增加不明显.     

石墨烯-二氧化钛复合物对泰乐菌素的光解作用

为了在可见光条件下有效光解去除抗生素,制备了石墨烯-二氧化钛复合物(Graphene-TiO2,G-TiO2),考察了不同因素对G-TiO2的光解作用的影响以及催化剂的重复利用效果。研究结果表明,G-TiO2在可见光下对泰乐菌素(tylosin,TYL)有一定的去除效果,光解速率随溶液pH的增加先增加后减小,随着TYL初始浓度的增加而减小。石墨烯含量为1%时光解效果最好,且催化剂有较好的重复利用性。初步分析,G-TiO2对TYL的去除包括吸附和光解2个过程,且光生空穴及·OH自由基反应可能是TYL光解的主要机制。本研究表明,G-TiO2是一种理想材料,可用于去除水中的抗生素微污染。     

复合纳米Fe2O3/TiO2可见光催化降解邻甲酚溶液的研究

以复合纳米Fe2O3／TiO2作为催化剂,日光色镝灯为光源,研究了邻甲酚溶液的可见光降解。考察了催化剂制备方法、催化剂使用量、溶液pH、催化剂重复使用等条件对可见光降解的影响。实验结果表明,1％Fe2O3／TiO2（n）对邻甲酚溶液的可见光降解效果最优,比Ti02（p25）的降解率提高了2．6倍。在实验条件下,可见光降解3h,邻甲酚溶液的浓度去除率达95．4％,TOC去除率为72．3％。在较宽的浓度范围内,邻甲酚的反应服从一级动力学反应方程,随着浓度的增大,反应速率常数不断降低。     

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.     

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.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

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.     

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.     

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.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.     

Biochemical interaction of six op delayed neurotoxicants with several neurotargets

Abstract

Five organophosphorous insecticides: Leptophos, EPN, Cyano‐fenphos, trichloronate and salithion proved to cause irreversible ataxia not only to chicken but also to mice and sheep. TOCP was included as a reference. Cyanofenphos blocked the catecholamine B‐receptor binding activity with ³H‐norepinephrine at a level similar to that of the specific inhibitor propranolol in the mouse heart preparation. In the lamb heart preparation, the B‐receptor was more sensitive to Leptophos, salithion and TOCP than to propranolol. The six compounds and their oxons were screened for their in‐vitro inhibition to monamine oxidase (MAO), acetyl cholinesterase (AChE) and neurotoxic esterase (NTE) in the brain of either mouse, lamb or chicken. It is believed that their AChE inhibition stands for their acute toxicity, while NTE inhibition is responsible for their paralytic ataxia.     

Phytoextraction of lead-contaminated soil using vetivergrass (<Emphasis Type="Italic">Vetiveria zizanioides</Emphasis> L.), cogongrass (<Emphasis Type="Italic">Imperata cylindrica</Emphasis> L.) and carabaograss (<Emphasis Type="Italic">Paspalum conjugatum</Emphasis> L.)

Background, Aims and Scope The global problem concerning contamination of the environment as a consequence of human activities is increasing. Most of the environmental contaminants are chemical by-products and heavy metals such as lead (Pb). Lead released into the environment makes its way into the air, soil and water. Lead contributes to a variety of health effects such as decline in mental, cognitive and physical health of the individual. An alternative way of reducing Pb concentration from the soil is through phytoremediation. Phytoremediation is an alternative method that uses plants to clean up a contaminated area. The objectives of this study were: (1) to determine the survival rate and vegetative characteristics of three grass species such as vetivergrass, cogongrass and carabaograss grown in soils with different Pb levels; and (2) to determine and compare the ability of the three grass species as potential phytoremediators in terms of Pb accumulation by plants. Methods The three test plants: vetivergrass (Vetiveria zizanioides L.); cogongrass (Imperata cylindrica L.); and carabaograss (Paspalum conjugatum L.) were grown in individual plastic bags containing soils with 75 mg kg⁻¹ (37.5 kg ha⁻¹) and 150 mg kg⁻¹ (75 kg ha⁻¹) of Pb, respectively. The Pb contents of the test plants and the soil were analyzed before and after experimental treatments using an atomic absorption spectrophotometer. This study was laid out following a 3 × 2 factorial experiment in a completely randomized design. Results On the vegetative characteristics of the test plants, vetivergrass registered the highest whole plant dry matter weight (33.85–39.39 Mg ha⁻¹). Carabaograss had the lowest herbage mass production of 4.12 Mg ha⁻¹ and 5.72 Mg ha⁻¹ from soils added with 75 and 150 mg Pb kg⁻¹, respectively. Vetivergrass also had the highest percent plant survival which meant it best tolerated the Pb contamination in soils. Vetivergrass registered the highest rate of Pb absorption (10.16 ± 2.81 mg kg⁻¹). This was followed by cogongrass (2.34 ± 0.52 mg kg⁻¹) and carabaograss with a mean Pb level of 0.49 ± 0.56 mg kg⁻¹. Levels of Pb among the three grasses (shoots + roots) did not vary significantly with the amount of Pb added (75 and 150 mg kg⁻¹) to the soil. Discussion Vetivergrass yielded the highest biomass; it also has the greatest amount of Pb absorbed (roots + shoots). This can be attributed to the highly extensive root system of vetivergrass with the presence of an enormous amount of root hairs. Extensive root system denotes more contact to nutrients in soils, therefore more likelihood of nutrient absorption and Pb uptake. The efficiency of plants as phytoremediators could be correlated with the plants’ total biomass. This implies that the higher the biomass, the greater the Pb uptake. Plants characteristically exhibit remarkable capacity to absorb what they need and exclude what they do not need. Some plants utilize exclusion mechanisms, where there is a reduced uptake by the roots or a restricted transport of the metals from root to shoots. Combination of high metal accumulation and high biomass production results in the most metal removal from the soil. Conclusions The present study indicated that vetivergrass possessed many beneficial characteristics to uptake Pb from contaminated soil. It was the most tolerant and could grow in soil contaminated with high Pb concentration. Cogongrass and carabaograss are also potential phytoremediators since they can absorb small amount of Pb in soils, although cogongrass is more tolerant to Pb-contaminated soil compared with carabaograss. The important implication of our findings is that vetivergrass can be used for phytoextraction on sites contaminated with high levels of heavy metals; particularly Pb. Recommendations and Perspectives High levels of Pb in localized areas are still a concern especially in urban areas with high levels of traffic, near Pb smelters, battery plants, or industrial facilities that burn fuel ending up in water and soils. The grasses used in the study, and particularly vetivergrass, can be used to phytoremediate urban soil with various contaminations by planting these grasses in lawns and public parks. ESS-Submission Editor: Dr. Willie Peijnenburg (wjgm.peijnenburg@rivm.nl)