氯苯类化合物的生物降解

经过2个月的驯化,从某染料厂和某毛纺厂活性污泥中分离出能够生长于1,4-二氯苯、1,2,4-三氯苯和六氯苯的4种微生物.通过测定该混合菌降解氯苯类化合物过程中的累积好氧量、微生物生长曲线及降解产物Cl^-的释放,证明在好氧条件下该混合菌能够以1,4二氯苯和1,2,4-三氯苯为唯一碳源和能源,降解产物Cl^-浓度的变化与微生物生长周期有关.通过好氧振荡瓶培养法测得3种氯苯的生物降解顺序为:1,4-二氯苯[356.7μg/(L·d)]>1,2,4-三氯苯[110.4μg/(L·d)]>六氯苯[～6μg/(L·d)],说明氯取代数越多,氯苯类化合物越难被好氧降解.     

施用堆腐有机肥对水稻土中六氯苯脱氯降解影响

采用水稻盆栽实验,供试土壤为红壤性水稻土和乌栅土,分别设定对照及添加1%和2%堆腐有机肥的处理,研究施用该有机肥对六氯苯(HCB)在种水稻土壤中还原脱氯降解的影响,并分析甲烷生成与HCB脱氯降解的关系.结果表明,18周之后,红壤性水稻土中HCB可提取态残留减少了28.6%～30.1%,乌栅土中HCB可提取态残留减少了47.3%～61.0%;水稻植株吸收的HCB及其降解产物量仅为土壤中HCB初始量的千分之几;HCB发生脱氯降解主要生成五氯苯(PeCB);由于乌栅土的pH和可溶性有机碳含量均高于红壤性水稻土,HCB在乌栅土中的脱氯降解效率较高;在红壤性水稻土中和乌栅土中,施用1%和2%堆腐有机肥分别在第6和第10周后显著抑制PeCB生成,且PeCB生成速率在有机肥的2个添加水平之间均无显著差异;产甲烷菌在脱氯降解中的作用因环境条件而异.     

BAT and BEP as instruments for reducing emissions of unintentionally produced POPs and development of guidelines under the stockholm convention

The 6th Intergovernmental Negotiating Committee (INC 6), under the Stockholm Convention on POPs, gave an expert group the mandate to develop guidelines for the application and implementation of best available techniques (BAT) and best environmental practices (BEP) for the prevention and reduction of unintentionally produced and emitted POPs, including polychlorinated dibenzodioxins/-furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB). Measures to reduce or eliminate the release of these POPs to the environment can be found in Article 5 of the Convention. BAT and BEP are already being applied as emission reduction instruments in a number of industrialised countries and are elements of other major international treaties, e.g. the UN ECE Protocol on POPs and the Marine Convention's OSPAR and HELCOM, and of the EU Directive for Integrated Pollution Prevention and Control (IPPC Directive). Existing concepts are presented and compared with the requirements of the Stockholm Convention. Consequences, perspectives and questions for the future intersessional work of the above-mentioned Expert Group are discussed.     

Dehalogenation potential of municipal waste incineration fly ash

BACKGROUND, AIMS AND SCOPE: It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450 degrees C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash matter therefore plays the decisive role. In the present paper, the function of important components responsible for the dehalogenation activity of MWI-FA is analysed and compared with the model fly ash. METHODS: With the aim of accounting for the dehalogenation activity of MWI-FA, the following studies of hexachlorobenzene (HCB) dechlorination were performed: The role of copper in dehalogenation experiments was evaluated for five types of metallic copper. The gasification of carbon in MWI-FA was studied in the 250-350 degrees C temperature range. Five different kinds of carbon were used, combined with conventional Cu(o) and activated nanosize copper powder. The dechlorination experiments were also carried out with Cu(II) compounds such as CuO, Cu(OH)2, CuCl2 and CuSO4. The results were discussed from the standpoint of thermodynamics of potential reactions. Based on these results, the model of fly ash was proposed, containing silica gel, metallic copper and carbon. The dechlorination ability of MWI-FA and the model fly ash are compared under oxygen-deficient atmosphere. CONCLUSIONS: The results show that, under given experimental conditions, copper acts in the dechlorination as a stoichiometric agent rather than as a catalyst. The increased surface activity of copper enhances its dechlorination activity. It was found further that the presence of copper leads to a decrease in the temperature of carbon gasification. The cyclic valence change from Cu(o) to Cu+ or Cu2+ is a prerequisite for the dehalogenation to take place. RECOMMENDATION AND OUTLOOK: Thermodynamic analysis of the dechlorination effect, as well as the comparison of dechlorination pathways on MWI-FA and model fly ash, can provide a deeper understanding of the studied reaction.     

Monitoring bioaccumulation and toxic e ects of hexachlorobenzene using the polyurethane foam unit method in the microbial communities of the Fuhe River,Wuhan

Hexachlorobenzene （HCB） is a chlorinated aromatic hydrocarbon that was widely used for seed dressing in prevention of fungal growth on crops, and also as a component of fireworks, ammunition, and synthetic rubbers. Because of its resistance to degradation and mobility, HCB is widely distributed throughout the environment and is accumulated through food chains in different ecosystems. In this study, a preliminary investigation was carried out on the bioaccumulation and the toxic effects of HCB in the microbial （protozoan in particular） communities in the Fuhe River, Wuhan, a water body receiving industrial wastewaters containing HCB and other pollutants, using the standardized polyurethane foam units （PFU） method. Field samples were taken from eight stations established along the Fuhe River in January and August 2006. The concentration ratios of HCB in microbial communities and in water were 9.66-18.64, and the microbial communities accumulated 13.29-56.88 μg/L of HCB in January and 0.82-10.25 μg/L HCB in August. Correlation analysis showed a negative correlation between the HCB contents in the microbial assemblage, and the number of species and the diversity index of the protozoan communities. This study demonstrated the applicability of the PFU method in monitoring the effects of HCB on the level of microbial communities.     

环境因素对六氯苯厌氧降解活性的影响

在厌氧污泥具备了较好的六氯苯（HCB）降解能力的基础上,采用标准血清瓶实验方法考察了反应温度、初始pH、摇床转速和营养元素等环境因素对厌氧污泥降解HCB活性的影响。实验设计的反应温度为25、30、35和40℃;初始pH为5.0、6.0、7.0和8.0;摇床转速为0和150r·min-1;营养元素有葡萄糖和维生素b12。用HCB浓度随时间的减少来表征微生物对其的降解活性。结果表明,反应温度对HCB的降解速率有很大影响,适宜温度为35℃左右。初始pH对HCB降解活性没有显著影响,但显示出有随初始pH增大而HCB降解活性增加的趋势。与静置条件相比,一定的混合作用有利于提高HCB的降解活性。有葡萄糖存在条件下,维生素b12对HCB的降解活性有明显的促进作用。温度及外加碳源（葡萄糖）是影响HCB厌氧降解活性的重要因素,并推测葡萄糖在HCB降解过程中提供电子供体方面发挥了重要作用。     

吹扫捕集-气相色谱质谱法测定地表水中12种氯苯类有机物

采用吹扫捕集-气相色谱质谱联用法测定地表水中的12种氯苯类有机污染物,特别是一些半挥发性的多氯苯化合物如五氯苯、六氯苯等。在室温下分析时,当进样体积为25.0 mL,吹扫时间为11 min,解析时间为3 min,采用全扫描方式定量分析时,方法检出限为0.02~1.50μg/L。不同浓度水平的加标回收率为86.0%~113%,相对标准偏差为1.3%~17.5%;实际样品加标回收率为84.4%~119%,相对标准偏差为2.2%~18.9%。该法具有简便高效、灵敏度高、有机溶剂用量少等优点,适用于饮用水和地表水中氯苯类化合物的测定,并为突发性环境污染事件氯苯类有机物的快速响应提供了一种快速有效的检测方法。     

Linking empirical estimates of body burden of environmental chemicals and wellness using NHANES data

Biomonitoring of industrial chemicals in human tissues and fluids has shown that all people carry a “body burden” of synthetic chemicals. Although measurement of an environmental chemical in a person's tissues/fluids is an indication of exposure, it does not necessarily mean the exposure concentration is sufficient to cause an adverse effect. Since humans are exposed to multiple chemicals, there may be a combination effect (e.g., additive, synergistic) associated with low-level exposures to multiple classes of contaminants, which may impact a variety of organ systems. The objective of this research is to link measures of body burden of environmental chemicals and a “holistic” measure of wellness. The approach is demonstrated using biomonitoring data from the National Health and Nutrition Examination Surveys (NHANES). Forty-two chemicals were selected for analysis based on their detection levels. Six biological pathway-specific indices were evaluated using groups of chemicals associated with each pathway. Five of the six pathways were negatively associated with wellness. Three non-zero interaction terms were detected which may provide empirical evidence of crosstalk across pathways. The approach identified five of the 42 chemicals from a variety of classes (metals, pesticides, furans, polycyclic aromatic hydrocarbons) as accounting for 71% of the weight linking body burden to wellness. Significant interactions were detected indicating the effect of smoking is exacerbated by body burden of environmental chemicals. Use of a holistic index on both sides of the exposure-health equation is a novel and promising empirical “systems biology” approach to risk evaluation of complex environmental exposures.     

厌氧混合培养条件下六氯苯生物降解的外加碳源必要性

采用标准血清瓶实验探讨了厌氧污泥对六氯苯(HCB)的降解活性以及各种环境因素的影响.结果表明,经过14d的HCB驯化,厌氧污泥具备了较好的降解HCB能力;反应温度对HCB的降解速率有很大影响,适宜温度为35℃左右;葡萄糖、甲酸、乙酸、丙酸和丁酸等有机碳源的存在明显促进了HCB的厌氧降解,其中甲酸和乙酸的加入极其重要;根据实验结果推测出,产甲烷过程对HCB的生物降解发挥了重要作用.     

光助Fenton氧化法降解水中六氯苯的研究

采用光助Fenton氧化法处理六氯苯模拟废水,考察了反应时间、Fe3 与H2O2摩尔比、Fenton试剂用量、初始pH、六氯苯初始浓度、光强对六氯苯降解效果的影响,并初步探讨了六氯苯的降解动力学规律.结果表明.光助Fenton法降解六氯苯的最佳工艺条件为:紫外灯功率为300 W、Fe3 投加量为1.0 mmol/L、H2O2投加量为5.0 mmol/L、反应时间为60 min、初始pH为3,在此条件下,浓度为500μg/L的HCB的去除率可达91.3%.UV辐射与Fenton氧化对HCB的降解具有协同效应.光助Fenton法对HCB的降解符合一级反应动力学方程,表观速率常数为0.04 min-1,与Fenton法相比,提高了近9倍.