Processes driving the degradation of polybrominated diphenyl ethers in terrestrial environment

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants, have gained the attention of many researchers due to their persistence in various environmental matrices. Their usage in numerous consumer products has lent credence to their ability to retard flammable gas formation and brought attention to their ubiquitous occurrence in the environment. PBDEs have been described as endocrine-disrupting chemicals because of their interference with the endocrine system in aquatic and terrestrial animals. In spite of the progress in research over the decades on PBDEs, a full understanding of the environmental behavior and fate of this contaminant is still elusive. Therefore, terrestrial contamination of PBDEs has been evaluated in conjunction with their levels of toxicity, transformation, and transport in various environmental compartments. This review provides a wider perspective of the behavior of PBDEs in the terrestrial environment. Through examining the numerous studies on the environmental contamination of PBDEs, a number of mounting concerns and data gaps have been identified. Numerous methodologies have been discussed including adsorption, catalytic, photocatalytic, electrocatalytic, photo-electrocatalytic, aerobic, and anaerobic degradation. The comparative PBDE degradation analysis suggests that the oxidative degradation pathway is the most appropriate way of wastewater treatment while the role of other soil ingredients on subsurface treatments is still under investigation.     

加速溶剂萃取-分子筛固相萃取-气相色谱-串联质谱法测定土壤中多氯萘北大核心CSCD

新污染物引发的环境和健康风险正逐步受到社会各界的广泛关注,我国第十四个五年规划和2035年远景目标纲要明确“重视新污染物治理”。作为新型的持久性有机污染物,多氯萘(PCNs)在土壤中通常处于痕量水平,一般需要经过多层硅胶柱/氧化铝柱等复杂的净化方法,再结合有效的分析手段才能实现准确测定。关注土壤中多氯萘分离分析方法可以为掌握和监管其在土壤中的污染状况提供技术和方法支持。研究以13X分子筛作为固相萃取吸附剂,评价了其对多氯萘的净化效果。研究发现:使用正己烷作为上样溶剂和淋洗剂,10 mL二氯甲烷/正己烷(2∶15,v/v)为洗脱溶剂,可以实现PCNs与脂类大分子等干扰物的选择性分离,且多氯萘内标的平均回收率为56.1%~88.0%。与凝胶渗透色谱法、弗罗里硅土固相萃取柱以及多层硅胶柱/氧化铝柱相比,13X分子筛对土壤提取液的净化效果优于前两种净化方法,可以获得与多层硅胶/氧化铝柱相近的净化效果(53.0%~117.0%),而且操作更加简单,环境更加友好,分析成本大幅度下降。在此基础之上,建立了加速溶剂萃取-分子筛固相萃取,结合气相色谱-三重四极杆质谱法测定土壤中PCNs的分析方法。PCNs同族体的方法检出限为0.009~0.6 ng/g。采用基质加标法评价了本方法的精密度和准确度,CN-3、13、42、46、52、53、73、75在低、中、高加标水平下的平均加标回收率分别为70%~128%、71%~115%和61%~114%,测定结果的相对标准偏差分别为4.2%~23%、6.5%~31%和4.7%~22%,满足痕量分析的要求且平行性较好。从整个分析流程来看,13X分子筛有望成为新污染物净化的新型固相萃取吸附剂,并在土壤新污染物普查中发挥重要作用。     

Visualizing Redox Chemistry: Probing Environmental Oxidation–Reduction Reactions with Indicator Dyes

One of the important questions in the chemistry of pollutant degradation is the identity and distribution of chemical agents that are responsible for reduction reactions in the environment. Reduction occurs primarily in water-saturated environments, such as sediments, soils, and sludges. Redox indicators can be used (i) as chemical probes to obtain fundamental insights into biogeochemical processes and (ii) as the basis for demonstrations suitable for teaching aspects of environmental chemistry. This paper explores the latter with examples that involve a variety of indicators (indigo sulfonates, resazurin, etc.), environmental media (anaerobic sediments and granular iron metal), and physico-chemical processes (oxidation-reduction, adsorption, and diffusion). The results show that reduction by either media (sediments or iron metal) is primarily, although not always entirely, a surface reaction. This situation results in indicator behavior that is interesting and challenging for students with a wide range of backgrounds.     

A perspective on environmental models and QSARs

A general review is presented of the roles of QSARs and mass balance models as tools for assessing the environmental fate and effects of chemicals of commerce. It is argued that all such chemicals must be assessed using a consistent and transparent methodology that uses chemical property data derived from QSARs, or experimental determinations when possible and applies evaluative or region-specific environmental models. These data and models enable an assessment to be made of the key chemical features of persistence, bioaccumulation, potential for long-range transport and toxicity. The other key feature is quantity used or discharged to the environment. A taxonomy of environmental models is presented in which it is suggested that rather than develop a single comprehensive model, the aim should be to establish a set of coordinated and consistent models treating evaluative and real environmental systems at a variety of scales from local to global and including food web models, organism-specific models and human exposure and pharmacokinetic models. The concentrations derived from these models can then be compared with levels judged to be of toxic significance. A brief account is given of perceived QSAR needs in terms of partitioning, reactivity, transport and toxicity data to support these models.     

A perspective on environmental models and QSARs

A general review is presented of the roles of QSARs and mass balance models as tools for assessing the environmental fate and effects of chemicals of commerce. It is argued that all such chemicals must be assessed using a consistent and transparent methodology that uses chemical property data derived from QSARs, or experimental determinations when possible and applies evaluative or region-specific environmental models. These data and models enable an assessment to be made of the key chemical features of persistence, bioaccumulation, potential for long-range transport and toxicity. The other key feature is quantity used or discharged to the environment. A taxonomy of environmental models is presented in which it is suggested that rather than develop a single comprehensive model, the aim should be to establish a set of coordinated and consistent models treating evaluative and real environmental systems at a variety of scales from local to global and including food web models, organism-specific models and human exposure and pharmacokinetic models. The concentrations derived from these models can then be compared with levels judged to be of toxic significance. A brief account is given of perceived QSAR needs in terms of partitioning, reactivity, transport and toxicity data to support these models.     

Electrochemistry-mass spectrometry for mechanistic studies and simulation of oxidation processes in the environment

Electrochemistry (EC) coupled to mass spectrometry (MS) has already been successfully applied to metabolism research for pharmaceutical applications, especially for the oxidation behaviour of drug substances. Xenobiotics (chemicals in the environment) also undergo various conversions; some of which are oxidative reactions. Therefore, EC-MS might be a suitable tool for the investigation of oxidative behaviour of xenobiotics. A further evaluation of this approach to environmental research is presented in the present paper using sulfonamide antibiotics. The results with sulfadiazine showed that EC-MS is a powerful tool for the elucidation of the oxidative degradation mechanism within a short time period. In addition, it was demonstrated that EC-MS can be used as a fast and easy method to model the chemical binding of xenobiotics to soil. The reaction of sulfadiazine with catechol, as a model substance for organic matter in soil, led to the expected chemical structure. Finally, by using EC-MS a first indication was obtained of the persistence of a component under chemical oxidation conditions for the comparison of the oxidative stability of different classes of xenobiotics. Overall, using just a few examples, the study demonstrates that EC-MS can be applied as a versatile tool for mechanistic studies of oxidative degradation pathways of xenobiotics and their possible interaction with soil organic matter as well as their oxidative stability in the environment. Further studies are needed to evaluate the full range of possibilities of the application of EC-MS in environmental research.     

Modeling the Environmental Fate of Atrazine

Abstract

Mathematical simulation models of fate and transport of chemicals have been identified by researchers and regulators as potentially valuable tools for improving the understanding of the environmental behavior of chemicals which may be released to the environment as a consequence of routine (i.e., normal manufacturing, use, disposal) and non-routine (e.g., accidental spillage) events. In this context, CHEMFRANCE, a regional fugacity model level III, which calculates the environmental distribution of organic chemicals in 12 defined regions of France, or France as a whole, has been designed. The aim of this study is to show that CHEMFRANCE provides valuable simulation results for understanding the environmental fate behavior of atrazine.     

Occurrence, fate and determination of cytostatic pharmaceuticals in the environment

We review the literature on the analysis of pharmaceutically-derived cytostatic compounds in the environment. Cytostatics are a major class of chemotherapy drugs used extensively in the fight against cancer. They are a broad group of mostly organic compounds possessing a diverse range of physico-chemical parameters. Their differences and their presence in the environment in trace amounts make their determination in complex matrices a major challenge. Despite the good scientific foundations laid by those in the field, it is apparent that past research has focused mainly on hospital effluents and few have analyzed environmental samples. Importantly, no study has looked at environmental transformation products that, along with human metabolites, could contribute to overall toxicity. To improve understanding of the chemodynamics of cytostatics in natural waters, it is essential to have more data on the occurrence and the fate of these compounds, including their human metabolites and environmental transformation products. This approach will require advanced sampling techniques and state-of-the-art analytical tools, including the latest separation methods and cutting-edge instrumentation.     

效应引导的污染物分析与识别方法

识别环境样品中主要贡献污染物有助于确定环境风险的来源,是环境治理的前提。单一的化学分析和生物学检测方法常常遗漏主要贡献污染物的信息。效应引导的污染物识别(effected-directed analysis, EDA)是以生物检测引导组分分离、化学分析与污染物鉴定的实用方法,是环境风险评价以及环境样品中主要贡献污染物筛查与识别的有力手段。该方法已成功用于环境中遗传毒物、内分泌干扰物和芳香烃受体效应污染物等污染物的鉴定,为特定污染地区贡献污染物及其来源的确定提供了宝贵的基础数据。本文综述了EDA中所应用的样品提取、分离策略、生物效应检测以及贡献化合物的识别方法,总结了近年来以EDA为手段在环境中识别的效应污染物并对目前EDA应用所存在的问题与未来的发展趋势进行了分析。     

Development and Evaluation of Sampling and Analytical Techniques for Investigating Air-Water Exchange of Chemicals

Abstract

Gas exchange across the air-water interface is one of the three major transport pathways for atmospheric inputs of organic pollutants in the Great Lakes. It is essential to advance our knowledge of the air-water exchange processes to improve our understanding of the environmental pathways and fate of a variety of persistent and toxic chemicals. Two complementary prototype devices were developed and tested for direct characterization of air-water exchange processes. One was a sparger device which was used to determine the (truly) dissolved concentration of a given chemical in water, and hence its potential for diffusive transfer at the air-water interface. The other was a flux chamber with which the chemical mass transfer rate from the water surface to the atmosphere (or vice versa) was determined. Ambient air and air from the sparger and flux chamber were collected/concentrated on multi-bed adsorbent tubes, followed by thermal desorption GC-MS analysis. Collected water samples were filtered and then concentrated on adsorbent tubes which were subject to similar thermal desorption GC-MS analytical procedures. The combination of these techniques provides a useful means for the estimation of the mass transfer rates of chemicals across the air-water interface.     

Predicting the biodegradation products of perfluorinated chemicals using CATABOL

Perfluorinated chemicals (PFCs) form a special category of organofluorine compounds with particularly useful and unique properties. Their large use over the past decades increased the interest in the study of their environmental fate. Fluorocarbons may have direct or indirect environmental impact through the products of their decomposition in the environment. It is a common knowledge that biodegradation is restricted within non-perfluorinated part of molecules: however, a number of studies showed that defluorination can readily occur during biotransformation. To evaluate the fate of PFCs in the environment a set of principal transformations was developed and implemented in the simulator of microbial degradation using the catabolite software engine (CATABOL). The simulator was used to generate metabolic pathways for 171 perfluorinated substances on Canada's domestic substances list. It was found that although the extent of biodegradation of parent compounds could reach 60%, persistent metabolites could be formed in significant quantities. During the microbial degradation a trend was observed where PFCs are transformed to more bioaccumulative and more toxic products. Perfluorooctanoic acid and perfluorooctanesulfonate were predicted to be the persistent biodegradation products of 17 and 27% of the perfluorinated sulphonic acid and carboxylic acid containing compounds, respectively.     

Occurrence of pharmaceutical metabolites and transformation products in the aquatic environment of the Mediterranean area

The presence of pharmaceutically active substances (PhACs) in aquatic ecosystems is of great concern due to their constant occurrence in different water systems and potential negative effects on the quality of water and living organisms. After consumption, PhACs are excreted as the parent compound, and/or as free or conjugated metabolites, which might finally arrive to surface and ground waters after their incomplete removal (and possible degradation) in the wastewater treatment plants (WWTP). A large amount of data about parent PhACs in water has been reported in the literature in the last decade; however, there is a lack of information about the presence of their metabolites and transformation/degradation products (TPs). Recent publications report that PhACs found in water are only the “top of the iceberg” in relation to the environmental impact associated to the consumption of PhACs. From a scientific-technological point of view, the overall study of PhACs is a challenge and requires to advance with respect to current knowledge and analytical capacities, considering several key aspects, such as the reliable identification and quantification of the compounds, the improvement of the removal efficiency by the WWTPs, the study of their behaviour in the environment (e.g. persistence and biodegradability), and the environmental risk assessment, considering not only the parent PhACs but also their transformation/metabolism products. In this work, it is intended to delve into this problem, presenting a detailed overview on metabolites and TPs of PhACs in environmental waters from the Mediterranean area. Analytical and environmental problems associated to the determination of these compounds are briefly commented, ending the paper with the main conclusions and expected future trends in relation to this field.     

Protein adsorption and transport in polymer-functionalized ion-exchangers

A wide variety of stationary phases is available for use in preparative chromatography of proteins, covering different base matrices, pore structures and modes of chromatography. There has recently been significant growth in the number of such materials in which the base matrix is derivatized to add a covalently attached or grafted polymer layer or, in some cases, a hydrogel that fills the pore space. This review summarizes the main structural and functional features of ion exchangers of this kind, which represent the largest class of such materials. Although the adsorption and transport properties may generally be used operationally and modeled phenomenologically using the same methods as are used for proteins in conventional media, there are noteworthy mechanistic differences in protein behavior in these adsorbents. A fundamental difference in protein retention is that it may be portrayed as partitioning into a three-dimensional polymer phase rather than adsorption at an extended two-dimensional surface, as applies in more conventional media. Beyond this partitioning behavior, however, the polymer-functionalized media often display rapid intraparticle transport that, while qualitatively comparable to that in conventional media, is sufficiently rapid quantitatively under certain conditions that it can lead to clear benefits in key measures of performance such as the dynamic binding capacity. Although possible mechanistic bases for the retention and transport properties are discussed, appreciable areas of uncertainty make detailed mechanistic modeling very challenging, and more detailed experimental characterization is likely to be more productive.     

Environmental aspects of tributyltin

The tributyltin species, the active ingredient in some antifouling paint formulations, is perhaps the most acutely toxic chemical to aquatic organisms ever deliberately introduced to water. It has been demonstrated to have an adverse effect on shellfish in France and England, and as a consequence the use of tributyltin-containing antifouling paints has been restricted in these countries. Other countries have banned the use of tributyltin-containing antifouling paints or are contemplating restrictions. This article reviews such environmental aspects of tributyltin as methods of analysis, toxicity, environmental occurrence, persistence and fate. Tributyltin concentrations in many locations may be high enough to cause chronic toxicity or harmful effects in some aquatic organisms, and in some locations the tributyltin concentrations may be high enough to be acutely toxic to some organisms. Biological degradation of tributyltin in water and sediment appears to be the most important factor limiting the persistence of tributyltin in aquatic environments. To some degree, then, the persistence of tributyltin in aquatic environments depends upon the nature of the ecosystem. Tributyltin exhibits low-to-medium persistence in water and moderate persistence in sediment. A summary is given of the regulatory status of tributyltin in some countries, and recommendations are made for further research.     

湿度对Cu/TCNQ金属有机双层膜化学传质的影响研究

采用真空蒸发方法制备了Cu/TCNQ金属机双层膜. 系统研究了湿度对CuTCNQ络合物形成过程的影响规律, 结果表明湿度对膜的化学反应传质过程有明显加速作用. 过程机制在干燥条件与湿度作用条件下有本质不同: 前者为固体化学扩散机制, 而后者为水溶液电化学反应机制. 进一步深入分析传质时间与湿度的关系后发现, 湿度条件下薄膜对水分子的吸附是反应传质速度的控制步骤.     

Structure-fate relationships of organic chemicals derived from the software packages E4CHEM and WHASSE

A risk assessment of chemicals is to be performed on the basis of the model EUSES, developed by the Commission of the European Union. The model package E4CHEM (Exposure Estimation for Potentially Ecotoxic Environmental Chemicals), developed in 1984-1992, is presented and applied in this paper as a model which allows a model-supported evaluation of chemicals. E4CHEM consequently does not have the wide applicability and technical comfort of the more recently developed model EUSES. The simulation models of E4CHEM characterize the chemical behavior in the environment by many aspects. Hence, there is a need to condense all of these aspects to get a clear impression of what will be the fate of the chemicals. Starting with the already published concept of exposure maps, we will discuss how partial orders may be helpful in establishing generalized structure-fate relationships. The software WHASSE is applied.