二氯苯在土壤中的迁移行为和生物降解

主要从挥发、吸附与解吸、渗滤三个方面介绍了二氯苯在土壤中的迁移行为以及生物降解过程。探讨了二氯苯的物化性质、三种同分异构体的构型、土壤特性、外界环境条件等因素对二氯苯迁移行为的影响,以及迁移行为与生物降解的相互关系;同时介绍了可降解二氯苯的微生物种类、二氯苯好氧生物降解机理、共代谢现象,以及实验室研究方法。这些研究对于受二氯苯污染的土壤的修复具有理论指导意义。     

施氏假单胞菌N2代谢邻/间/对甲酚的特性研究

本论文以施氏假单胞菌N2为受试菌株,研究了N2菌对邻/间/对甲酚及其混合物的生物降解特性.结果表明,N2菌能以邻/间/对甲酚为唯一碳源和能源生长,但对3种异构体的降解速率各异.完全降解600 mg·L~(-1)的对甲酚仅需6 h,间甲酚则需24 h,但对邻甲酚的降解明显减缓;200 mg·L~(-1)邻甲酚48 h的降解率仅为11.38%.GC-MS结果分析发现,N2菌代谢甲酚途径主要为甲基氧化、芳环羟化,随后脱羧、开环裂解、降解转化至矿化,但3种甲酚的降解途径及酸性代谢产物的形成次序不一致.3种甲酚混合存在时可促进N2菌对其降解,这主要是因为混合碳源的协同作用减少了体系中因产酸过多引起的毒性,从而促进了N2菌对甲酚的降解矿化.     

模拟太阳光作用下间甲酚的水相和冰相光转化研究

本文研究了在模拟太阳光作用下间甲酚的水相和冰相光转化规律.考察了不同浓度的H2O2、NO-2和NO3^-对间甲酚光转化的影响,建立了不同条件下间甲酚光转化的动力学方程.结果表明,在模拟太阳光作用下间甲酚在水相和冰相中均可以发生光转化,间甲酚的冰相光转化速率小于水相.在本实验条件下,H2O2和NO2^-促进了间甲酚在水相...     

Fe-Mn/AC催化湿式过氧化氢氧化间甲酚

采用等体积浸渍法制备了一种新型Fe-Mn/AC催化剂,应用于催化湿式过氧化氢氧化(CWPO)间甲酚废水.通过SEM和XRF表征了其表面形态结构和元素组成,通过穆斯堡尔谱分析了催化剂中铁离子的存在形态,结果表明,新型Fe-Mn/AC催化剂中的铁以二价铁、三价铁以及四氧化三铁的形式存在.通过正交实验考察了CWPO降解间甲酚的影响因素,结果表明,各因素对间甲酚转化率影响的大小顺序依次为:底物初始p H值反应温度反应时间催化剂投加量.通过正交实验得到CWPO降解间甲酚的最佳反应条件.当间甲酚浓度为100 mg·L-1、反应温度为40℃、反应时间为40 min、催化剂投加量为0.6 g·L-1及底物初始p H值为3时,间甲酚转化率为99.8%,TOC去除率为28.3%.气相色谱/质谱联用没有检测到中间产物,气相色谱检测到CWPO降解间甲酚中间产物主要为乙酸和丙酸.     

全氟化合物同分异构体的环境行为及毒性效应研究进展

以全氟辛烷磺酸盐(PFOS)和全氟辛烷羧酸(PFOA)为代表的全氟化合物(PFASs)是一类新型持久性有机污染物,目前已经在全球自然环境、野生生物及人群中广泛检出,其环境与健康问题已引起人们的高度重视。传统的电氟化法生产工艺使PFASs产品存在碳链同分异构体。这些PFAS的同分异构体可能具有不同的环境行为和毒理效应。随着分析方法的逐渐成熟,目前,国外的学者已经在该研究领域进行了一些探索性的研究,并取得了一定的进展,而我国在该领域的研究相对较少。以PFOS和PFOA为例,在介绍了PFAS同分异构体的来源、命名和世界各地生产厂家的异构体组成等基本信息的基础上,还系统介绍了环境介质中PFAS同分异构体的分析方法、环境迁移转化差异及源分析研究;生物和人体的生物累积性及毒理学差异等;并对目前存在的问题进行了讨论,为今后PFAS同分异构体的环境问题研究提供相应的参考。     

间甲酚降解Citrobacter farmeri 的降解特性及代谢途径解析

考察了在不同温度、pH值、摇床转速、氮源等环境和营养条件下,间甲酚降解菌Citrobacter farmeri对降解速率和降解过程中反应液的TOC值、紫外吸收及酶活的变化.结果表明,Citrobacter,farmeri降解间甲酚的最适温度为35℃,培养基初始pH值为6.5-8.0,摇床转速为170 r·min~(-1),无机氮比有机氮和氨态氮比硝态氮更利于Citrobacter farmeri对间甲酚的降解;当间甲酚初始浓度低于375mg·l~(-1)时,Citrobacter farmeri降解间甲酚符合零级动力学方程;间甲酚初始浓度约为60 mg·l~(-1)时约4 h完全降解,TOG的去除率8 h内可达到77%,之后几乎不变;Citrobacter farmeri可完全降解约600 mg·l~(-1)的间甲酚,表现出高效与强耐受能力的结合.对酶活的测定发现,儿茶酚1,2-双加氧酶有明显增大,初步判断Citrobacter farmeri以邻位裂解的途径对间甲酚进行降解.     

利用前线分子轨道能预测有机物生物毒性的方法

本文以线性自由能理论为基础提出了一种利用分子轨道能预测有机物生物毒性的方法，并利用这种方法建立了预测氯代芳烃化合物发光菌毒性的定量相关方程。     

32种芳香化合物的好氧生物降解性表征

本文采用芳香化合物生物降解产生的二氧化碳量作为表征其生物降解性的指标，测定了３２囊芳香化合物好氧生物降解１２ｄ产生的二氧化碳量，在此基础上提出了定性划分有机物生物降解性的标准，按照此标准对３２种芳香化合物的生物降解性进行了划分；另外还探索了影响生物降解性的诸因素。     

有机污染物生物降解性预测模型

生物降解性是评估污染物环境持久性的重要依据,也是化学品是否获准生产及进入市场的评价指标。采用17位生物降解领域专家评估的生物降解等级数据,通过功能树(FT)算法建立了包含15个分子结构参数的初级生物降解和最终生物降解预测模型。外部验证结果表明,模型具有较好的预测准确性,初级生物降解性加权准确度(weighted accuracy,WA):训练集WA=84.1%,验证集WA=78.9%;最终生物降解性WA:训练集WA=91.0%;验证集WA=83.6%。预测正确性对化合物的杠杆值作图,表征了生物降解性模型的应用域。     

部分取代苯类在江水中的生物降解与结构相关性研究^1）

测定了27种取代苯类化合物在松花江江水中的生物降解性，采用量子化学MOPAC6．0－AM1法计算了化合物的分子量（MW），生成热（Hf)，分子总表面积（TSA）及高占有轨道能（EHOMO），结合辛配醇／水分配系数lgP及酸解离常数pKa对其中22种化合物BOD值进行了多元线性回归分析，得到如下模型：BOD＝105.73-0.439MW-0.076Hf-6.660lgP n=22,R^2=0.821,SE=8.250,F=27.56,P=0.000应用所得模型对其余5个化合物的生物降解性进行了预测，只有一个化合物相的相对预测误差大于20％，为20．8％，平均预测误差为12．4％。     

4种具有α-季碳结构的对位壬基酚异构体的合成和表征

不同来源工业壬基酚混合物(t-NP)中对位壬基酚(p-NP)异构体的组成各不相同,各异构体之间在环境行为等方面也存在着较大差异,因此在壬基酚的环境归趋、生态毒性以及雌激素活性等研究中迫切需要t-NP中不同单个异构体作为模型化合物,然而目前市场上能购买到的直链壬基酚(4-n-NP)异构体不能作为代表.以苯酚和4种含分支结构的壬醇为原料(苯酚与壬醇摩尔比为4:1),以BF3为催化剂,按照Friedel-Crafts烷基化方法合成了t-NP中常见的4种烷基链具有α-季碳结构的对位壬基酚的异构体,即4(3′,5′-二甲基-3′-庚基)-苯酚(p353NP),4(3′,6′-二甲基-3′-庚基)-苯酚(p363NP),4(2′,6′-二甲基-2′-庚基)-苯酚(p262NP)和4(3′-甲基-3′-辛基)-苯酚(p33NP).合成的壬基酚粗产物用硅胶柱色谱法提纯后的纯度达99%,并经紫外可见分光光度计、荧光分光光度计、HPLC、GC-MS、1H-和13C-NMR进行了表征.合成的4种p-NP异构体可被用于壬基酚的雌激素活性、毒理、代谢和环境归趋等研究.     

Biodegradation of Hexachlorocyclohexane by two species of Bacillus isolated from contaminated soil

Biodegradation of α, β, γ and δ hexachlorocyclohexane (HCH) isomers was studied in broth medium and soil microcosm by Bacillus circulans and Bacillus brevis isolated from contaminated soil. Degradation of α and γ isomers by both the bacterial isolates was higher than thermodynamically stable β and δ isomers. However, B. circulans was found more effective than B. brevis for β and δ isomers. Maximum rate of degradation was recorded at 150 mg/L followed by 100 and 50 mg/L. Soil microcosm study revealed maximum degradation of HCH isomers in the treatment containing natural soil, pesticide and bacterial inocula than the treatment having sterilised soil, pesticide and bacterial isolates. Chloride release was positively co-related with HCH degradation in broth medium as well as in soil microcosm, suggesting that B. circulans and B. brevis hold promising potential by having efficient enzyme(s) required for dechlorination of HCH from contaminated sites.     

Occurrence of and risk posed by highly carcinogenic dibenzo[def,p]chrysene isomers in urban soil

Dibenzopyrene and its isomers are considered the most potent carcinogens of all polycyclic aromatic hydrocarbons tested to date. However, despite public concerns over their deleterious effects, they have not been extensively studied. The occurrence of four highly carcinogenic isomers of dibenzopyrene – dibenzo[def,p]chrysene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene in urban soil samples from Shanghai, China, have been determined in this study, as well as that of benzo[a]pyrene and coronene. A total of 14 peaks with ions at m/z 302 were detected by gas chromatography-mass spectrometry. Although the concentrations of benzo[a]pyrene and the sum of the 16 priority polycyclic aromatic hydrocarbons were greater than that of dibenzopyrene and its isomers, the carcinogenic potency of the latter was higher than that of benzo[a]pyrene. The results also indicate that the relative carcinogenic potency of the four dibenzopyrene isomers in the samples is higher than that of the 16 priority polycyclic aromatic hydrocarbons.     

Ökotoxikologische Charakterisierung von Nonylphenol Isomeren

Background, Aim and Scope

Acute toxicity and estrogenic potency of six nonylphenol isomers, with nearly the same chemical structure and the same physico-chemical properties, were investigated in this study. Thes datasets give some insight into how far structure activity relationships can be used for these modes of action.

Methods

The toxicity of the isomers was investigated by the daphnia immobilisation test as well as the duckweed growth inhibition test. The estrogenic potency of the p-NP isomers was analyzed by MVLN-Reportergen-Assay.

Results

No differences between the isomers were found for baseline toxicity, neither in the daphnia immobilisation test nor in the duckweed growth inhibition test. Estrogenic potency of the isomers in the MVLN reportergen assay was markedly different for the tested isomers. The highest estrogenic potency was found for p353-NP, whereas p262-NP and p22-NP exhibited no estrogenic, but partial antagonistic potency in this assay.

Discussion

The results from this study clearly indicate how far simplification and structure activity relationships can be used in risk analysis. For bioconcentration and baseline toxicity structure activity relationships are possible and will allow simplification of the risk analysis. For special modes of action simple structure activity relationships are per se impossible. This was shown especially for the estrogen receptor interactions, where only small structural differences can lead to different modes of action.

Conclusions

It seems possible to reduce the effort for risk analysis, using combinations of measured data and predictive models. At the moment it seems unlikely that predictive models alone will and can be used for risk analysis.     

Analysis of the insecticide hexachlorocyclohexane isomers in biological media. A review

Hexachlorocyclohexane (HCH) and lindane were used as insecticides since 1949s. They were progressively banished in most of the nations in the world, because of the their persistence and their potential toxicity and carcinogenicity. They are still occurring in the environment. These insecticides and isomers (α-HCH, β-HCH…) were detected in all media, e.g. soils, sediments, potable water, vegetables, human and animal tissues and air. In this review, we present the synthesis of the analytical procedures and materials used to determine the HCHs isomers in media such as vegetables, human tissues, animals tissues and rations. The analytical techniques which are presented permit to select the best analytical conditions to detect HCHs isomers.     

Persistence of polychlorinated biphenyls in marine bivalves

Bivalves (Cerastoderma edule and Macoma balthica) which had previously been exposed to Aroclors^® 1242, 1254 and 1260 were able to reduce their tissue burdens of chlorobiphenyls with 2 to 5 chlorine atoms in short-term static assay systems. Elimination rates decreased with increasing chlorination and removal of isomers with more than 5 chlorine atoms was not recorded. Position, in addition to the number, of chlorine atoms influenced the persistence of chlorobiphenyls. Isomers with most ortho-substituted chlorine atoms were least persistent. Experiments with single isomers indicated variation in the elimination of low chlorinated isomers between bivalve species. These biological and chemical influences on tissue residues, together with environmental parameters such as temperature and suspended solids, are considered in relation to the use of bivalves as bio-indicators of marine pollution.     

Soxhlet extraction parameters’ influence on the recovery of polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) from a sediment,and artifact formation of PCDD

Soxhlet extraction of polychlorinated dibenzo‐p‐dioxins/dibenzofurans (PCDD/F) from sediment was studied using a designed experimental set‐up. Three variables were studied: three solvent combinations n‐hexane/methanol, dichloromethane/acetone and toluene/methanol; two extraction times, 8 and 16 h, and addition of bulk substances (sodium carbonate). The extraction efficiency was almost identical in all extractions, with the exception of extraction where toluene/ methanol was combined with sodium carbonate. In these samples a major effect was observed, due to formation of Hx‐, Hp‐ and OCDD isomers. Composition of formed PCDD was similar to PCDD isomers found in pentachlorophenol products.     

Accumulation of organochlorine insecticides in the blood of the general population of Nigeria

Gas Chromatographic determination of blood levels of organochlorine pesticides in people of Southern Nigeria is described. Among the compounds detected and quantified were the HCH‐isomers, DDT and its metabolites and dieldrin, the major pollutants being DDT, DDE and the HCH‐isomers. Delta‐HCH, HCB and Endrin were also detected in a few samples. Total DDT (DDT + DDE + DDD) ranged from 0.04–7.24 ppm, total HCH (alpha + beta + gamma) 0.08–5.64 ppm, and dieldrin 0.03–0.28 ppm.     

A study of neurotoxicity of BHC in relation to residual accumulation on the brain tissue of Heteropneustes fossilis (Bloch)

Neurotoxic effect of BHC, the organochlorine pesticide in Heteropneustes fossilis has been studied exposing at the dose concentrations of 1 ppm, 5 ppm and 10 ppm in lab aquarium for 96 hours over a period of one year. The results showed the behavioural abnormalities in different exposure concentrations such as dysfunction of endocrine gland, excretion of mucus, dispigmentation, sign of restlessness, erratic swimming with rapid jurkey movement, spiralling and convolution showing severe effect in central nervous system. Therefore an attempt has been made for monitoring of BHC residues viz. alpha, beta, gamma isomers in the brain tissue exposed to different sublethal concentrations using Gas liquid chromatography. The mean values of isomers were found to be 1.587 microg/gm for 1 ppm, 2.993 microg/gm for 5 ppm and 3.78 microg/gm for 10 ppm test group. Severe behavioural abnormalities were recorded at high dose concentration of pesticides with higher accumulation of pesticide residues in brain tissue.