短链氯化石蜡研究现状

作为一种潜在的持久性有机污染物,短链氯化石蜡(Short chain chlorinated paraffins,SCCPs)近年来正在接受斯德哥尔摩公约的审查。它具有持久性、生物富集性,长距离迁移、高毒性等特点,可能会对生态环境和人体健康造成威胁,目前许多国家已经对SCCPs推出了禁令。中国生产的氯化石蜡(CPs)由于没有相关产品标准的限制,其成份多少都会含有一定SCCPs,中国每年都会消费大量的CPs,在消耗的同时会产生较大的排放量,这些排放所造成的潜在环境污染风险是不可估量的。本文通过查阅相关文献,对短链氯化石蜡研究现状进行了整理。     

PCDD/PCDF,chlorinated pesticides and PAH in Chinese teas

Four samples of Chinese tea (two green teas, and two brick teas) were analyzed for their concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF), chlorinated pesticides and PAH. The infusions prepared from these teas were also analyzed for PCDD/PCDF. The levels of DDT and its metabolites in tea leaves were within the safety limit of 0.2 mg/kg. Rather high levels of total PAH were obtained in brick tea (1048–1162 mg/kg), when compared with green tea (497–517 mg/kg). In terms of PCDD/PCDF, the concentrations of green tea and brick tea differed by a factor of 16, while the concentrations of all infusions were within a factor of 2. The dioxin concentrations in green tea leaves can be explained through uptake of atmospheric PCDD/PCDF. The higher concentrations in the brick tea leaves are due the longer exposure time, and to certain extent, the use of old leaves, branches and roots when making the tea, and additional components such as soil particulates through contamination. Certain Chinese populations drinking a large amount of brick tea (>3 l per day) indicated that individuals of these populations consume more tea than Europeans or North Americans result in a comparably higher intake of PCDD/PCDF. Tea consumption can attribute to up to 10% of the TDI recommended by WHO (only PCDD/PCDF considered, no PCB analyzed).     

Ni-Fe/泡沫镍催化还原体系脱氯工艺参数的优化及表征

以泡沫镍做载体,采用电沉积法制备出镍/铁/泡沫镍双金属催化还原剂,并对目标污染物氯乙酸进行了脱氯研究,分析了催化还原剂在制备过程中沉积液浓度、电流密度对催化活性的影响,采用扫描电子显微镜对双金属体系表征以观察所制备的催化还原剂的表面形貌,可以观察到采用电沉积制备的Ni/Fe-泡沫镍双金属还原剂在基体泡沫镍上分布均匀、密集、呈针状结构,在一定电流密度下,沉积60 min的情况下无团聚现象。研究表明,本研究所制备的镍-铁/泡沫镍双金属催化还原剂对氯乙酸具有良好的脱氯效果。     

Biotransformation of phenolics with laccase containing bacterial spores

Treatment of effluents containing phenols such as textile dyes with fungal laccases is usually limited to the acid to neutral pH range and moderate temperatures. Here we demonstrate for the first time that spore-bound laccases which are stable at high temperatures and pH values can be used for phenolic dye decolorisation. Laccase containing spores from Bacillus SF were immobilized on alumina pellets. Both immobilized and free spores were able to completely decolorize the common textile dyes Mordant Black 9, Mordant Brown 96/Mordant Brown 15, and Acid Blue 74 within 90 min of incubation time and decolorized solutions were successfully used in re-dyeing.     

An eleven‐year study of chlorinated hydrocarbon insecticide residues in bovine fat in illinois, 1972–1982

Abstract

Bovine fat samples in Illinois were monitored for residues of chlorinated hydrocarbon insecticides from 1972 through 1982. The percentage of fat samples that were contaminated with all chlorinated hydrocarbons decreased during the 11‐year study. The percentage of samples contaminated with DDT and its analogs decreased most markedly from 82.4% in 1972 to 2.1% in 1982. The percentage of samples contaminated with aldrin/dieldrin and heptachlor/heptachlor epoxide began to decline in 1980 and continued to decrease through 1982.     

Enhanced catalytic complete oxidation of 1,2-dichloroethane over mesoporous transition metal-doped γ-Al_2O_3

High-surface-area mesoprous powders of γ-Al2O3 doped with Cu2+, Cr3+, and V3+ions were prepared via a modified sol–gel method and were investigated as catalysts for the oxidation of chlorinated organic compounds. The composites retained high surface areas and pore volumes comparable with those of undoped γ-Al2O3 and the presence of the transition metal ions enhanced their surface acidic properties. The catalytic activity of the prepared catalysts in the oxidation of 1,2-dichloroethane(DCE) was studied in the temperature range of 250–400°C. The catalytic activity and product selectivity were strongly dependent on the presence and the type of dopant ion. While Cu2+- and Cr3+-containing catalysts showed100% conversion at 300°C and 350°C, V3+-containing catalyst showed considerably lower conversion. Furthermore, while the major products of the reactions over γ-alumina were vinyl chloride(C2H3Cl) and hydrogen chloride(HCl) at all temperatures, Cu- and Cr-doped catalysts showed significantly stronger capability for deep oxidation to CO2.     

Anaerobic dechlorination and redox activities after full-scale Electrical Resistance Heating (ERH) of a TCE-contaminated aquifer

The effects of Electrical Resistance Heating (ERH) on dechlorination of TCE and redox conditions were investigated in this study. Aquifer and groundwater samples were collected prior to and after ERH treatment, where sediments were heated to approximately 100 degrees C. Sediment samples were collected from three locations and examined in microcosms for 250 to 400 days of incubation. Redox activities, in terms of consumed electron acceptors, were low in unamended microcosms with field-heated sediments, although they increased upon lactate-amendment. TCE was not dechlorinated or stalled at cDCE with field-heated sediments, which was similar or lower compared to the degree of dechlorination in unheated microcosms. However, in microcosms which were bioaugmented with a mixed anaerobic dechlorinating culture (KB-1) and lactate, dechlorination past cDCE to ethene was observed in field-heated sediments. Dechlorination and redox activities in microcosms with field-heated sediments were furthermore compared with controlled laboratory-heated microcosms, which were heated to 100 degrees C for 10 days and then slowly cooled to 10 degrees C. In laboratory-heated microcosms, TCE was not dechlorinated and redox activities remained low in unamended and lactate-amended sediments, although organic carbon was released to the aqueous phase. In contrast, in field-heated sediments, high aqueous concentrations of organic carbon were not observed in unamended microcosms, and TCE was dechlorinated to cDCE upon lactate amendment. This suggests that dechlorinating microorganisms survived the ERH or that groundwater flow through field-heated sediments carried microorganisms into the treated area and transported dissolved organic carbon downstream.     

Foliar Phenolics in Sugar Maple (Acer Saccharum) as a Potential Indicator of Tropospheric Ozone Pollution

Tropospheric O₃ has been implicated in the declining health of forest ecosystems in Europe and North America and has been shown to have negative consequences on human health. We have measured tropospheric ozone (O₃) in the lower canopy through the use of passive monitors located in five woodlots along a 150 km urban–rural transect, originating in the large urban complex of Toronto, Canada. We also sampled foliage from 10 mature sugar maple trees in each woodlot and measured the concentration of a number of phenolic compounds and macronutrients. O₃ concentrations were highest in the two rural woodlots, located approximately 150 km downwind of Toronto, when compared to the woodlots found within the Greater Toronto Area. Foliar concentrations of three flavonoids, avicularin, isoquercitrin, and quercitrin, were significantly greater and nitrogen concentrations significantly lower at these same rural woodlots, suggesting some physiological disruption is occurring in those sites where exposure to tropospheric O₃ is greater. We suggest that foliar phenolics of sugar maple may be a biochemical indicator of tropospheric ozone exposure.     

Recent trends in the decomposition of chlorinated aromatic hydrocarbons by ultrasound irradiation and Fenton's reagent

Over the past few years, a large number of studies have been conducted on the use of ultrasound for decomposition of harmful organic pollutants, particularly chlorinated aromatic hydrocarbons (CAH) in wastewater. The published reports cover a variety of applications, including both ultrasonic treatment alone and in combination with other methods, e.g., advanced chemical oxidation processes. This article presents a review of recent work on ultrasonic-based methods of CAH decomposition, with emphasis on the applications of ultrasound alone and in combination with Fenton's reagent, as attractive advanced oxidation systems. In the first part of this review, the basic principles of sonochemical treatment are presented, followed by a review of the applications of ultrasound alone for CAH degradation. In the second part, the mechanisms of CAH degradation with Fenton's reagent and its application for CAH degradation are summarized. In the final part, studies on the applications of ultrasound together with Fenton's reagent are reviewed. The reported results suggest that a combination of ultrasound and Fenton's reagent is more attractive for practical application than the use of either method separately. Further studies, however, are required in this area because the reaction mechanism and the relationship between the reaction rates and process parameters for such a combined process are not yet well established.     

Reductive dechlorination of chlorinated methanes in cement slurries containing Fe(II)

Degradative solidification/stabilization (DS/S) is a novel remediation technology that combines chemical degradation with conventional solidification/stabilization. The applicability of the Fe(II)-based DS/S to treating chlorinated alkanes was tested by characterizing degradation reactions of carbon tetrachloride (CT) and its daughter products in cement slurries containing Fe(II). Degradation kinetics of CT and chloroform (CF) were generally very rapid with reaction rates comparable to rates that can be obtained with zero-valent iron. Dechlorination reactions of CT proceeded primarily via a hydrogenolysis pathway, which yielded CF and methylene chloride (MC) as major products and chloromethane and methane as minor products. However, reaction pathways other than hydrogenolysis also appeared to be important at very high pH conditions. MC apparently was resistant to dechlorination reactions over a period of about two months. Kinetics of CT and CF transformation were strongly dependent on pH with an optimal value around 13, which was higher than found previously for PCE. When the initial CF concentration varied between 0.01 and 1 mM, and the Fe(II) dose was 104 mM, pseudo-first-order kinetics generally described the degradation reactions of CF. However, there was also some indication of substrate saturation kinetics in these experiments. This suggests that a saturation model would better describe the kinetics in systems with higher concentration of substrates or lower concentration of the reactive surfaces.