Organic pollutants adsorbed on microplastics: Analytical methodologies and occurrence in oceans

The massive use of plastics in several products has generated microplastic debris worldwide. Besides their negative effect on marine organisms by ingestion, microplastics are a contamination vector due to their capacity to transport organic pollutants around our planet. To evaluate the magnitude of this issue, it is necessary to know what kinds of contaminants are adsorbed on microplastics, as well as their concentrations. In order to assess the adsorption and desorption of pollutants from microplastics, effective and reliable extraction procedures are required. In this overview, literature reports, in which extraction, separation and determination methods have been applied to analyse the organic pollutants adsorbed on microplastics, are revised and discussed. Furthermore, the worldwide occurrence of organic compounds found on microplastics in oceans is reviewed and the results obtained from different geographical areas and their global distribution trends are compared. Priority organic pollutants, such as polycyclic aromatic hydrocarbons, hexachlorocyclohexanes, polychlorinated benzenes, perfluoroalkyl substances or bisphenol analogues, have been widely found on microplastic samples. Future research that focuses on different kinds of emerging pollutants is required.     

Current trends and analytical methods for evaluation of microplastics in stormwater

Stormwater runoff is an important source of microplastics (plastic particles <5 mm) into the aquatic environment and studies documenting the microplastics abundance and their characteristics are constantly expanding. The lack of standardized methods as well as the development of many analytical techniques to evaluate microplastics greatly influence reported results and calls for a better understanding of approaches adopted by microplastic studies in stormwater. Hence, this paper aims to systematically review currently employed methods for sampling, isolating and identifying microplastics and to summarize the data on the abundance of microplastics in the samples of water, sediment and biota collected from stormwater, stormwater catchment areas and stormwater discharging sites. There were significant methodological variations between the studies throughout the experimental procedures and different techniques including, sieving, digestion (chemical and enzyme), density separation and filtration were reported for microplastics extraction from sample matrix. A combination of visual sorting and spectroscopic approaches such as infrared and Raman was adopted to identify and study microplastic characteristics such as shape, size, color and polymer. The microplastic abundance in each sample matrix was different with relatively high concentrations of smaller size particles (10−500 μm), majorly fibrous shaped (51 %) and polymers of polypropylene (27 %) and polyethylene (26 %). Finally, we conclude by identifying analytical challenges and suggesting appropriate methods that can be implemented to enable effective monitoring and comparison of microplastic contamination in stormwater.     

微塑料介导重金属在陆生植物中迁移及生物效应的影响

随着地膜在现代化农业中的广泛应用,微塑料在土壤中的残留问题日益严重。环境中释放的微塑料可能会与先前存在的重金属相互作用,导致生物效应(生物积累/毒性),并对人类健康和农产品安全构成威胁。目前,大多数研究集中于单一影响因素在土壤系统中的暴露和转化分析,有关微塑料和共存金属对环境联合影响的相当有限。本文综述了微塑料与重金属来源、相互作用机理与影响因素的研究现状,阐述了陆生植物对二者联合污染的生理响应。此外,未来的研究还应重点探讨微塑料与重金属共同在植物上暴露的具体分子机制、通过食物链对人类健康的影响、与其他混合污染物联合作用及微塑料老化过程对重金属迁移动态变化过程的影响。     

How well-protected are protected areas from anthropogenic microplastic contamination? Review of analytical methods,current trends,and prospects

Microplastics have sparked global concern due to their negative effects on organisms' health and the environment. Microplastics research in protected areas (marine and freshwater) has recently gained prominence and is expected to grow in the coming years. This review of 36 published studies examines current progress and identifies future research challenges. It begins with an overview of microplastic evaluation methodologies, followed by a discussion of recent advances in the abundance of microplastics in water, sediment, biota, wet and dry deposition, and particulate matter. Current quality assurance and control measures are also summarized. The majority of studies (44 %) examined sediment samples. In biota, the gastrointestinal system was the most evaluated for microplastics. Digestion (using H₂O₂ and KOH) and density separation (using NaCl) are the most common microplastic extraction methods. We found that microplastic contamination is pervasive in all the surveyed protected areas, with varying levels of abundance geographically, and over 50 % of the biota ingest microplastics. The methodological discrepancies amongst the investigations, from sampling to microplastics characterization, make it difficult to compare the results and generate baseline data on microplastic contamination levels. Close monitoring and a standardized approach are thus required to determine the extent to which microplastics might enter and persist in protected area environments, as well as to devise effective mitigating strategies.     

Spectro-Microscopic Techniques for Studying Nanoplastics in the Environment and in Organisms

Nanoplastics (NPs), small (<1 μm) polymer particles formed from bulk plastics, are a potential threat to human health and the environment. Orders of magnitude smaller than microplastics (MPs), they might behave differently due to their larger surface area and small size, which allows them to diffuse through organic barriers. However, detecting NPs in the environment and organic matrices has proven to be difficult, as their chemical nature is similar to these matrices. Furthermore, as their size is smaller than the (spatial) detection limit of common analytical tools, they are hard to find and quantify. We highlight different micro-spectroscopic techniques utilized for NP detection and argue that an analysis procedure should involve both particle imaging and correlative or direct chemical characterization of the same particles or samples. Finally, we highlight methods that can do both simultaneously, but with the downside that large particle numbers and statistics cannot be obtained.     

水环境中微塑料的样品采集与分析进展

微塑料在环境中难以降解,可在水体、沉积物等环境介质中长期存在,并在水生生物体内积累,成为人们高度关注的环境问题之一。有关水环境中微塑料的污染研究尚处于起步阶段,快速、高效、准确的检测技术是水环境中微塑料研究的重要环节,对于优化研究路线、分析研究结果、总结微塑料污染规律至关重要。本文结合国内外微塑料污染研究进展,介绍了微塑料污染现状,并通过对环境样品中微塑料的采样、预处理以及定性定量分析方法的系统比较,总结了现行各种检测方法的优缺点及各自应用范围,最后指出了进一步研究的方向。     

土壤微塑料污染及生态环境效应研究进展

微塑料作为一种新的污染物,具有粒径小、疏水性强、性质稳定、可以吸附多种污染物等特点,近年来受到了广泛的关注。目前关于微塑料的研究主要集中在水环境中,土壤环境中的微塑料研究相对滞后。土壤与人类生活息息相关,但土壤微塑料污染的现状却不容乐观,土壤微塑料的环境效应需要重视。本文综述了土壤微塑料的来源、分离和鉴定方法、微塑料在土壤环境中的行为和生态效应,并对土壤微塑料的研究前景进行了展望。     

环境样品中微塑料分析技术研究进展

微塑料一般是指直径小于5 mm的塑料纤维、碎片或颗粒。环境中的微塑料来源广泛,性质稳定,是疏水性有机污染物和重金属的理想载体。微塑料易被浮游生物、鱼类及低等生物误食,并在食物网各营养级之间发生转移和富集,对食品安全存在潜在风险。开展微塑料分析技术研究是研究微塑料在环境中的分布、迁移、转化、归趋和生态毒理效应的基础。该文综述了国内外环境样品中微塑料的采集、分离提取、定性鉴别技术的研究进展,并探讨了各方法的优缺点。最后针对现阶段微塑料分析方法存在的问题和不足,展望了环境中微塑料分析技术的发展趋势。     

土壤样品中微塑料的分析方法研究进展

微塑料作为一种新型污染物,因其粒径小、难以降解、本身含有多种污染物、且易吸附疏水性有机污染物和重金属等产生复合污染,已成为国内外学者研究的热点问题。微塑料广泛存在于土壤环境中,进入土壤中的微塑料会影响土壤理化性质,同时影响土壤动物生长、植物生长和微生物活动等,并且,微塑料会在土壤中发生迁移或沿食物链传递从而对人类健康构成潜在风险。高效、统一、准确的微塑料分析方法是研究微塑料在土壤中分布、迁移、归趋和生态风险的基础。本文对近年来土壤中微塑料的采集、分离提取、鉴定量化和分析方法的质量保证等方面的研究进展进行了评述,比较了各个方法的优缺点及应用范围。最后,结合国内外微塑料污染最新研究进展,针对目前土壤微塑料分析方法存在的问题,对今后土壤微塑料分析技术的发展趋势进行了展望。     

Metal-Organic Framework-based Wood Aerogel for Effective Removal of Micro/Nano Plastics

The large amount of microplastic pollution in the aquatic environment has been regarded as a major challenge facing the world. Although some traditional water treatment processes can effectively remove microplastics in the millimeter range, research is still needed to solve the problem of removing smaller microplastics. Here, we made a durable zinc metal-organic framework-based composite material ZIF-8@Aerogel by in situ growing ZIF-8 on wood aerogel fibers, which can successfully remove microplastics in simulated water and seawater. The removal efficiencies on micro/nano plastics including poly(1,1-difluoroethylene)(60-110 nm) and polystyrene(90-140 nm) reached 91.4% and 85.8%, respectively. This work is expected to provide a new and efficient way to remove small-sized microplastic particles in the environment.     

Microextraction methods for the determination of phthalate esters in liquid samples: A review

1,2‐Benzenedicarboxylic acid esters, commonly referred to as phthalate esters, form a group of compounds that are mainly used as plasticizers in polymers. Because phthalate esters are not chemically bound to the plastics, they can be released easily from products and migrate into the food or water that comes into direct contact. Due to their widespread use, they are considered as ubiquitous environmental pollutants. Phthalate esters are regarded as endocrine disrupting compounds by means of their carcinogenic effect. Phthalate esters can be analyzed by gas chromatography or high‐performance liquid chromatography, however, their sensitivity and selectivity limit their direct use for determination of phthalates at very low level of concentrations exist in environmental samples with complex matrices. Therefore a sample pretreatment prior to their analysis is necessary. In this review, the historical development and overview of sample preparation methodologies have briefly been discussed and a comprehensive application of these methods in combination with different analytical techniques for preconcentration and determination of phthalate esters in various matrices have been summarized. Finally, a critical comparison of the different approaches in terms of enrichment factors achieved, extraction efficiency, precision, selectivity and simplicity of operation is provided.     

Methods for determination of polybrominated diphenyl ethers in environmental samples - review

Polybrominated diphenyl ethers (PBDEs) are a group of persistent organic pollutants. They are used as flame retardants in plastics, paints, varnishes and textile materials. PBDEs pose great risk to the environment because of their high persistence and ability to get into the environment easily due to the lack of chemical bonds with the matrix of materials, to which they are added. Global research studies confirmed the occurrence of those compounds in the majority of elements of water and land environment. Analysis of PBDEs in environmental samples is one of the specific analytical methods of criteria that comprise low detection limits and high selectivity. The analysis of PBDEs in environmental samples is one of the specific analytical methods, in which the main criteria are low detection limits and high selectivity. In this article, a literature review of methods for environmental sample preparation and analysis of the PBDE content was presented. The article discusses the potential of modern extraction techniques such as: solid-phase microextraction, single-drop microextraction, dispersive liquid-liquid microextraction, microwave-assisted extraction, cloud point extraction, hollow fibre-liquid phase microextraction and others for the separation of PBDEs from environmental samples with a complex matrix. Among the methods for qualitative and quantitative determination of PBDEs, a particular focus was put on gas chromatography/mass spectrometry with various injection techniques and different types of sample ionisation.     

Analysis of organic compounds in environmental samples by headspace solid phase microextraction

The analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent-free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi-volatile analytes from non-volatile compounds, thus greatly reducing the interferences from non-target compounds. This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl-benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi-volatile compounds, such as PAHs, from complex matrices.     

Determination of lanthanides by source excited energy dispersive X-ray fluorescence (EDXRF) method after preconcentration with ammonium pyrrolidine dithiocarbamate (APDC)

A new analytical procedure for determination of lanthanides in environmental samples after chemical separation from major matrix elements on DOWEX 50W-X8 resin followed by preconcentration with chelating agent ammonium pyrrolidine dithiocarbamate (APDC) and analyses of thin targets by energy dispersive X-ray fluorescence (EDXRF) method using ¹⁰⁹Cd as the source of excitation was presented. Characteristic L X-ray lines of the lanthanides were used for calculations of the net peak area and mass concentrations. The influence of pH value of the solution and addition of organic matter on the complexation was investigated. Percentage of recovery of each lanthanide after separation on DOWEX 50W-X8 resin was also determined. Accuracy of the method was tested on standard reference materials and real environmental samples (red mud material). For that purpose samples of standard reference materials and red mud were prepared as thick targets and directly analyzed (without the separation step) by EDXRF method using ²⁴¹Am as the excitation source. In that case lanthanides concentrations were determined over their characteristic K X-ray lines and results were compared with those obtained after separation/preconcentration step described above. Results showed that selected lanthanides made stable complexes with APDC in the alkaline medium with the maximum recovery at pH = 8. The presence of organic matter slightly modified the complexation by means of somewhat higher recovery percentage at pH lower than 7 and approx. 20% lower recovery at pH higher than 7.

Recovery of the elements after separation on DOWEX 50W-X8 resin and preconcentration with APDC at pH = 8 varied from 91.4% (Pr) to only 24.9% in the case of Dy.

Concentrations of lanthanides measured in standard reference material and environmental samples of red mud after microwave digestion, separation on DOWEX 50W-X8 resin, preconcentration with APDC at pH = 8 and recalculation on the percentage of recovery were in good agreement with certified values in the case of SRM as well as with the concentrations obtained by direct determination over K lines using ²⁴¹Am excitation source in the case of red mud leading to the conclusion that presented method was applicable for the determination of lanthanides in real environmental samples.     

Polymer Multi-Block and Multi-Block+ Strategies for the Upcycling of Mixed Polyolefins and Other Plastics

Due to a continued rise in the production and use of plastic products, their end-of-life pollution has become a pressing global issue. One of the biggest challenges in plastics recycling is the separation of different polymers. Multi-block copolymers (MBCPs) represent an efficient strategy for the upcycling of mixed plastics via induced compatibilization, but this approach is limited by difficulties associated with synthesis and structural modification. In this contribution, several synthetic strategies are explored to prepare MBCPs with tunable microstructures, which were then used as compatibilizer additives to upcycle mixtures of polyolefins with other plastics. A multi-block⁺ strategy based on a reactive telechelic block copolymer platform was introduced, which enabled block extension during the in situ melt blending of mixed plastics, leading to better compatibilizing properties as well as better 3D printing capability. This strategy was also applicable to more complex ternary plastic blends. The polymer multi-block strategy enabled by versatile MBCPs synthesis and the multi-block⁺ strategy enabled by in situ block extension show exciting opportunities for the upcycling of mixed plastics.     

废弃塑料光催化转化制备低碳数有机化合物

大量废弃塑料引发了一系列的环境和生态问题,其转化和利用一直受到广泛关注.塑料中含有丰富的碳元素,但这些碳元素往往以惰性的C–C键和C–H键形式存在,因此如何利用这些碳资源成为一大难题和挑战.以往部分研究已经提供了塑料催化转化制备碳材料、化学品和燃料的可能性,但是自然界中的废弃塑料总量庞大,需要考虑其转化过程中的能量来源.地球上有丰富的太阳能资源,光催化过程有可能利用太阳能来实现温和条件下的废弃塑料转化.在以往的研究中,光催化塑料降解和光催化塑料重整过程主要关注的目标产物分别是CO₂和H₂.相较而言,光催化塑料转化制备低碳数有机化合物的过程有望助力碳循环经济的发展.近年来报道了一些光催化塑料转化制备低碳数有机化合物的研究工作,这些研究为获取和利用塑料中的碳资源提供了新的研究思路和策略.本文概括对比了光催化塑料降解、光催化塑料重整和光催化塑料转化制备低碳数有机化合物三种过程的差异,包括其中的目标产物和相应的反应活性物种.此外,本文总结了光催化塑料转化制备低碳数化合物的反应方法.简要地说,塑料可以经过光催化选择性氧化、氧化偶联和水解脱氢等策略来得到低碳数的化学品和燃料,涉及利用光催化氧化过程断裂塑料中的C–C键,利用水解过程断裂塑料的C–N和C–O键,以及利用光催化脱氢过程断裂中间产物的O–H键和N–H键等关键步骤.在光催化塑料转化到低碳数有机产物的文献报道中,主要涉及液固相反应体系和反应器,需要考虑反应溶剂的选择.水是理想的溶剂,但对塑料的溶解能力有限.当使用其他有机溶剂时,需要利用同位素标记实验验证产物中的碳物种来源.此外,实际废弃塑料上残留的其他杂质会影响光催化剂的吸光过程,降低光催化反应效率,因此亟需设计和开发合理的光反应器来提高对光能的利用率,实现塑料的高效转化.虽然塑料制备低碳数化学品和燃料的光催化转化策略已有研究报道,但未来仍需探索更加高效的转化路线.此外,塑料主要呈现高分子聚合物的结构,未来的研究可以借鉴对生物质等天然聚合物分子的转化策略.     

Quality assessment for methodological aspects of microplastics analysis in soil

Over the last several years, a number of studies have concentrated on the occurrence, potential sources, and ecological implications of soil systems. However, the studies’ methodological aspects have received little attention. Thus, this study performed a quality assessment for the methodological aspects of soil microplastics studies by adopting the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) evaluation method. A total of 35 soil microplastic studies have been evaluated in terms of methodological aspects using 13 criteria, namely, sampling methods and strategy, sample processing and storage, sample size, laboratory preparation, clean air conditions, chemical purity, negative control, positive control, sample pre-treatment, microplastics particle data, particle size, particle shape and polymer type identification. The quality assessment findings indicated that no study scored a maximum of two in all criteria, reiterating the urgent need for enhanced quality assurance for future soil microplastics studies. The average quality assessment scores in soil microplastics studies also indicated that the conditions requiring the most improvement involve both the criteria of positive controls and the criteria of clean air conditions. With a value of zero in 13 assessed criterion, the relevance of the study’s findings in environmental risk assessment was restricted, suggesting that future studies should consider strengthening the implementation and reporting of QA/QC protocol. Adoption of proper quality assurance and contamination control measures will guarantee high data quality and establish confidence in the study’s findings, which allow for reproducibility and comparability as well as acceptability to be utilized in risk assessments.     

Advances in miniaturization and increasing sensitivity in analysis of organic contaminants in marine biota samples

In recent years there has been much progress in the miniaturization of sample treatment approaches for the analysis of organic contaminants. Whilst much focus has been given to analysis of liquid matrices (e.g., water, biological fluids), equivalent approaches for lipid rich biota samples have seen significantly less progress. This is especially the case for samples of very small organisms commonly employed as standard test species in ecotoxicity studies. Typically, the extractable biotic sample size available for body residue analysis is very small and the total pollutant accumulation can vary significantly between species types according to factors such as organism size, lipid content and exposure conditions. Depending on the physical and chemical characteristics of the analyte(s) in question, extraction and purification, especially from more complex matrices, appears to be one of the main bottlenecks in achieving their quantification. The current article presents a review of the available micro-extraction methods for small marine biota samples, focusing on environmentally important organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides.     

Simply Applicable Method for Microplastics Determination in Environmental Samples

Microplastics (MPs) have gained significant attention in the last two decades and have been widely researched in the marine environment. There are, however, less studies on their presence, routes of entry, and impacts on the biota in the soil environment. One of the main issues in the study of MPs is a lack of standardized methods for their identification in environmental samples. Currently the most commonly used techniques are thermal desorption gas chromatography–mass spectrometry (GC–MS) methods and pyrolysis followed by GC–MS. In this study, headspace-solid phase microextraction followed by GC–MS is proposed as a simple and widely applicable method for the determination of commonly present polymer MPs (polyethylene terephthalate, polystyrene, polyvinyl chloride, polyethylene, and polypropylene) in environmental samples, for analytical laboratories with basic equipment worldwide. The proposed method is based on the identification of compounds, which are formed during the well-controlled melting process of specific coarse (1–5 mm) and fine fraction (1 mm–100 μm) MPs. The method was upgraded for the identification of individual polymer type in blends and in complex environmental matrices (soil and algae biomass). The successful application of the method in complex matrices makes it especially suitable for widescale use.     

Antimony in the environment as a global pollutant: a review on analytical methodologies for its determination in atmospheric aerosols

This review summarizes and discusses the research carried out on the determination of antimony and its predominant chemical species in atmospheric aerosols. Environmental matrices such as airborne particulate matter, fly ash and volcanic ash present a number of complex analytical challenges as very sensitive analytical techniques and highly selective separation methodologies for speciation studies. Given the diversity of instrumental approaches and methodologies employed for the determination of antimony and its species in environmental matrices, the objective of this review is to briefly discuss the most relevant findings reported in the last years for this remarkable element and to identify the future needs and trends. The survey includes 92 references and covers principally the literature published over the last decade.