塑料，包括微塑料 (MPs) 和纳米塑料 (NPs)，以及它们相关的化学物质，几乎在迄今为止采样的每个环境隔间和位置都被发现，并且它们的数量每年都在增加。(1) 作为回应，许多司法管辖区和国际社会正在采取措施遏制无处不在的塑料污染。(2) 这些举措必然依赖可靠的数据，从中可以自信地辨别来源、时间和地理趋势以及影响。然而，相对于其他形式的化学污染，塑料带来了独特的挑战。环保塑料由不同聚合物、尺寸、形状、表面功能、添加剂成分和风化程度的复杂混合物组成。(3) 必须充分捕捉这种复杂性，以解决从来源识别到了解食物网转移和毒性等一系列问题。然而，这种复杂性违背了对其他污染物需要数十年开发和验证的现有采样和表征方法的依赖。因此，迫切需要经过充分验证的方法来支持建立基线环境数据和评估影响的协议。为了应对这一挑战，塑料污染这一复杂而多方面的话题吸引了来自不同学科的科学家，从分析化学家到环境科学家，再到人类毒理学家和生态毒理学家（仅举几例）。这个虚拟问题汇集了不同的研究，其目标是推进研究 MP 和 NP 的统一方法。通过协调，我们指的是减少方法之间的差异，以便可以对获得的结果进行定量比较。相反，标准化指的是一套协议或程序，从而消除实践中的差异。后者不太可能及时实现。但是，MP 和 NP 社区可以努力使用具有可比性的协调方法。在走向协调的道路上，研究正在开发对所有环境隔间中的 MP 进行稳健、定量和非靶向表征和分析的程序，以及测试和探索 MP 和 NP 对生物群的影响。我们预计这个虚拟问题和其他后续研究将导致最佳实践的可用性和采用，并最终协调一致，使我们能够自信地在全球范围内对 MPs 和 NPs 污染进行基准测试，并了解其环境命运和影响。本文介绍的论文有助于开发与环境相关的 MP 和 NP 复杂混合物的统一测试材料、分析方法和实验方案。与任何新的研究领域一样，对于科学家如何定义和解决研究问题和假设以及开发分析、建模或实验方法以了解污染物对环境或健康的影响，最初存在多种方法。这种协调的目的是什么？结果的可比性最常被引用为协调的关键原因，并且有充分的理由。拥有现成的参考材料将允许校准仪器和测试方法。因此，分析设备的协调有利于就不同方法的分析检测限和工作参数达成共识。样本收集、处理和数据处理的统一最佳实践可确保报告的结果公正无误并避免分析伪影。此外，协调的方法可以简化表征和量化 MP（以及最终 NP）的整个流程，同时具有使该领域的新从业者更快上手的额外好处（即，没有人需要重新发明轮子）。总之，协调有助于理解整个领域的结果并将其置于背景中，并会减少不确定性。虽然努力采用统一的方法很重要，但同样重要的是要认识到所使用的方法必须适合所提出的研究问题。从本质上讲，这个阶段的探索在分析、实验设计、建模方法和暴露研究方面是受欢迎和需要的，以解决独特和有针对性的研究问题。此外，还应继续努力改进方法，例如，描述相关的不确定性和潜在偏差的特征。随着该领域的成熟，对质量保证/质量控制步骤的使用和明确解释的期望也越来越高，例如报告检测限 (4) 和使用与环境相关的 MP 进行毒性测试。采样评估的完整描述和证据、样品制备、MP 和 NP 的表征以及测试应该是所有研究的常规部分。(5) 最终，在不断发展的技术和协调之间存在平衡，一方面寻求新技术和探索允许新的发展，而协调允许比较。从事塑料污染研究的人员共同努力在 MP 和 NP 研究中实现最佳实践，以平衡整个领域的新方法和协调技术。在这个虚拟问题中，我们强调了有趣的发展，考虑到以新见解和适合目的的技术为特色的研究的二分法与导致最佳实践的协调方法，包括关于 (1) 分析方法开发的出版物，(2) 创建统一的测试材料，(3) 实验设计、采样和数据处理，以及 (4) MP 如何影响技术和环境系统。对现有分析方法的批判性审查和对前进道路的建议是该领域新手了解 MP 和 NP 分析领域的现状、挑战和研究差距的简单入门途径，包括关注矩阵的特定考虑因素水中的 MP，如 Elkhaltib 等人所总结。（6）和 Delgado-Gallardo 等人，（7）和土壤，由 Moeller 等人评估。(8) 评估用于量化轮胎路面磨损颗粒的热解 GC-MS 的 ISO 技术规范，Rauert 等。发现不同制造商的合成橡胶和添加剂成分存在很大差异。(9) 因此，作者发现使用 ISO 方法有可能低估环境浓度，作者建议需要进一步完善分析的协调。不断提出识别 MP 的新方法，例如 Primke 等人，他们探索了通过基于量子级联激光的高光谱红外化学成像快速可靠地确定 MP 的大小、形状和数量的方法。(10) 将这种技术的性能与现有最先进的傅立叶变换红外显微镜分析在许多不同环境样本中的性能进行比较，作者建议将这种方法作为快速 MPs 监测方法的可行途径具有非常详细的数据集。为了减少对 MP 的成像和表征的时间要求，Hufnagl 等人。在使用机器学习工具进行光谱测量后开发了自动化数据分析。(11) 在一些基于实验室的研究中，通过使用嵌入聚合物中的保守示踪剂（例如痕量金属）规避了 NPs 和 MPs 分析的挑战，以便更容易地量化和理解使用金属的命运和运输作为塑料的代用品。例如，凯勒等人。评估了 NP 颗粒和 MP 纤维通过不饱和多孔介质的传输 (12) 和 Heinze 等人。通过生物扰动检查土壤中 NPs 的运输 通过使用嵌入聚合物中的保守示踪剂（例如痕量金属）规避了 NP 和 MP 分析的挑战，以便通过使用金属作为塑料的替代品来更轻松地量化和理解命运和运输。例如，凯勒等人。评估了 NP 颗粒和 MP 纤维通过不饱和多孔介质的传输 (12) 和 Heinze 等人。通过生物扰动检查土壤中 NPs 的运输 通过使用嵌入聚合物中的保守示踪剂（例如痕量金属）规避了 NP 和 MP 分析的挑战，以便通过使用金属作为塑料的替代品来更轻松地量化和了解命运和运输。例如，凯勒等人。评估了 NP 颗粒和 MP 纤维通过不饱和多孔介质的传输 (12) 和 Heinze 等人。通过生物扰动检查土壤中 NPs 的运输地龙(13) 使用这种方法，使作者能够以更快的速度和准确性跟踪更小的粒子。正如 Bacha 等人所评论的那样，了解大塑料如何降解为 MP 和 NP 有助于生成可用于多项研究的测试材料。(14) 在这种情况下，Pfohl 等人。使用与行业相关的聚合物调整 NanoRelease 协议，以开发参数化的机械碎裂模型，使用不同的紫外线剂量和冷冻研磨来测量碎裂率。(15) 许多研究解决了进行生态毒性测试时实验设计和人工制品的混杂因素。例如，Hermsen 等人。批判性地审查了生物样品中 MP 的质量标准，作者指出，可变性和无法直接比较研究之间的结果可能是由于缺乏统一的方法。(16) 随后，作者提出了 10 个标准来衡量未来的研究，以努力协调未来的最佳实践。Petersen 等人评估了毒性试验中的混杂因素，特别是与 NP 和 MP 剂量的伪影以及缺乏对照实验有关。(17) Pikuda 等人还强调了与商业配方中防腐剂相关的问题，他们特别指出了非透析 MP 对生物体的急性毒性，因此，毒性主要与叠氮化钠有关，叠氮化钠是纳米塑料悬浮液中的一种防腐剂，而不是粒子本身。(18) 然而，在某些情况下，正如 Kim 等人所指出的，MP 中的化学物质可能会产生毒性。(19) 在这里，作者发现不良反应主要归因于可提取的添加剂，当这些添加剂在生物体暴露前被提取时，测试材料的急性毒性显着降低。此虚拟特刊中强调的其他论文评估实验设计，以促进不同研究结果的比较。例如，Kooi 和 Koelmans 指出，许多研究都在努力解决环境样本中 MP 的多样性，而当前的分类方法并没有捕捉到环境 MP 本质上连续和多样化的性质。(20) 因此，作者创建了一个三维概率分布，尽管这是一个简化的概念，它在概率风险建模中可能特别有用。为了更好地调整 MPs 研究中使用的方法，以获取以前在 MPs 暴露评估方面无法比拟的数据集，Koelmans 等人。建议一种方法来纠正不同暴露测试中颗粒大小、数量、体积和质量的差异，以解释用于创建物种敏感性分布的不同类型的 MP。(21) 同样，环境样本中 MP 的样本异质性也会影响采样和分析工作。白等。批判性地分析了采样方法，目的是开发统一的方法，特别侧重于捕获 MPs 的可变时空河流通量，(22) 和 Kittner 等人。使用统一的分析方法对多瑙河流域的 MP 进行了全面筛选。(23) 莫加多等人。使用泊松对数正态分布和粒子计数的不确定性评估和模拟影响 MP 量化的随机和系统效应，并提供用户友好的电子表格以促进研究组之间的协调。(24) 最后，很明显，MP、NP 和塑料添加化学品的多样性与环境测试系统的复杂性相结合导致了不同研究的结论。上面，我们概述了该领域的几种协调尝试，但仍然很缺乏的是可以在实验室组之间进行比较的测试材料。目前，大多数实验室都在内部生产自己的 MP 和 NP，但统一也将受益于一个更大的存储库，该存储库包含用于分析校准以及环境归宿和生物吸收比较的特征明确的标准。另一个需要进一步关注的问题是各种过程对 MPs 和 NPs 的理化表面特性的影响，这会影响它们的环境运输和与生物有机体的相互作用。塑料还会对技术和环境系统产生间接影响，(25-27) 这也是未来应该更深入探索的另一个领域。值得注意的是，其他颗粒污染物的分析和实验协调，例如工程纳米材料的环境健康和安全评估，需要很多年才能发展，并且在某些方面仍在进行中。尽管如此，有许多经验教训可以纳入 MP 和 NP 研究，例如，包括设计与环境相关的测试材料和暴露系统。(28) 在未来几年，我们期待看到这一研究领域的协调进展如何实现最佳实践，以支持学术研究并最终在未来更广泛地监测和测试 MP 和 NP 环境污染。Denise M. Mitrano 是瑞士苏黎世联邦理工学院环境系统科学系的助理教授。作为一名环境分析化学家，她专注于技术和环境系统中人为材料的分布和影响。她特别感兴趣的是开发分析工具，以系统地了解驱动粒子命运、运输和生物相互作用的机制和过程，例如工程纳米材料和纳米塑料和微塑料。在这种情况下，她的研究小组使用这些结果来评估各种生态系统和规模的人为材料的风险。通过研究环境科学、材料科学和政策的边界来促进新材料的可持续性和环境健康与安全，体现了对纳米材料和塑料的更安全设计方法的兴趣。她的工作最近获得了瑞士国家科学基金会 Marie Heim Vögtlin 年度杰出青年女研究员奖（2022 年）、2022 年 James J.ES&T和 ACS 环境化学分部，以及 2022 年原子光谱学新兴研究者奖。她目前担任ES&T Letters 的主题编辑. 本文引用了 28 篇其他出版物。这篇文章尚未被其他出版物引用。Denise M. Mitrano 是瑞士苏黎世联邦理工学院环境系统科学系的助理教授。作为一名环境分析化学家，她专注于技术和环境系统中人为材料的分布和影响。她特别感兴趣的是开发分析工具，以系统地了解驱动粒子命运、运输和生物相互作用的机制和过程，例如工程纳米材料和纳米塑料和微塑料。在这种情况下，她的研究小组使用这些结果来评估各种生态系统和规模的人为材料的风险。通过研究环境科学、材料科学和政策的边界来促进新材料的可持续性和环境健康与安全，体现了对纳米材料和塑料的更安全设计方法的兴趣。她的工作最近获得瑞士国家科学基金会 Marie Heim Vögtlin 年度杰出青年女研究员奖（2022 年）、2022 年 James J. Morgan 环境科学杰出贡献早期职业奖ES&T和 ACS 环境化学分部，以及 2022 年原子光谱学新兴研究者奖。她目前担任ES&T Letters 的主题编辑。本文引用了 28 篇其他出版物。
"点击查看英文标题和摘要"
Balancing New Approaches and Harmonized Techniques in Nano- and Microplastics Research
Plastics, including microplastics (MPs) and nanoplastics (NPs), along with their associated chemicals, are being found in virtually every environmental compartment and location sampled to date, and their abundance is increasing annually. (1) In response, numerous jurisdictions and the global community are taking steps to stem ubiquitous plastic pollution. (2) These initiatives necessarily rely on sound data from which sources, temporal and geographic trends in abundance, and effects can be confidently discerned. However, plastics pose unique challenges relative to other forms of chemical pollution. Environmental plastics are comprised of a complex mixture of different polymers, sizes, shapes, surface functionalities, additive compositions, and degrees of weathering. (3) This complexity must be adequately captured to tackle issues ranging from source identification to understanding food web transfer and toxicity. However, this complexity defies reliance on existing methods of sampling and characterization that for other pollutants took decades to develop and validate. As such, there is a pressing need for well-validated methods that underpin building baseline environmental data and protocols for evaluating impacts. In response to this challenge, the complex and multifaceted topic of plastics pollution attracts scientists from diverse disciplines, ranging from analytical chemists to environmental scientists to human toxicologists and eco-toxicologists (to name a few). This virtual issue draws together diverse studies unified by the goal of advancing harmonized methods for studying MPs and NPs. By harmonization, we refer to reducing variations between methods so that the results obtained can be quantitatively compared. In contrast, standardization refers to a set protocol or procedure and thus eliminating differences in practices. The latter is unlikely to be achieved in a timely fashion. However, the MPs and NPs community can strive toward using harmonized methods that allow for comparability. Along the road toward harmonization, studies are developing procedures for robust, quantitative, and nontargeted characterization and analysis of MPs in all environmental compartments as well as testing and probing impacts of MPs and NPs on biota. We anticipate that this virtual issue and other ensuing studies will lead to the availability and adoption of best practices and ultimately harmonization to enable us to confidently benchmark MPs and NPs pollution globally and to understand its environmental fate and impacts. The papers presented here contribute to the development of harmonized test materials, analytical approaches, and experimental protocols for environmentally relevant complex mixtures of MPs and NPs. As with any new field of research, there is initially a diversity of approaches on how scientists define and tackle research questions and hypotheses and develop analytical, modeling, or experimental methods to understand environmental or health impacts of a pollutant. What is the purpose of this harmonization? Comparability of results is most often cited as the key reason for harmonization, and with good reason. Having readily available reference materials would allow for calibration of instrumentation and test methods. Consequently, harmonization of analytical equipment is beneficial to achieve a consensus of analytical detection limits and working parameters of different approaches. Harmonized best practices for sample collection, handling, and data processing ensure that results reported are unbiased and avoid analytical artifacts. In addition, harmonized methods can streamline the entire pipeline of characterization and quantification MPs (and eventually NPs) while having the added benefit of bringing new practitioners in the field up to speed faster (i.e., no one needs to reinvent the wheel). In summary, harmonization can help to understand and contextualize results across the field and would decrease uncertainty. While it is important to strive for harmonized methods, it is also important to recognize that methods used must be tailored to the research question being asked. In essence, exploration at this stage is welcome and needed in terms of analytics, experimental design, modeling approaches, and exposure studies to address unique and targeted research questions. In addition, efforts should continue to improve methods by, for example, characterizing associated uncertainties and potential biases. As the field matures, so too do expectations for the use and clear explanation of quality assurance/quality control steps followed such as reporting limits of detection (4) and using environmentally relevant MPs for toxicity testing. Full descriptions and evidence of evaluation of sampling, sample preparation, characterization of MPs and NPs, and testing should be a routine part of all studies. (5) Ultimately, there is a balance between ever-evolving techniques and harmonization, where on one hand reaching for new techniques and exploration allows for new developments where harmonization allows for comparisons. Collectively, those working in plastics pollution research strive to achieve best practices in MPs and NPs research, which balances new approaches and harmonized techniques across the field. In this virtual issue, we highlight interesting developments considering the dichotomy of research featuring new insights and fit-for-purpose techniques with harmonized approaches leading toward best practices, including publications on (1) analytical method development, (2) creating harmonized test materials, (3) experimental design, sampling, and data processing, and (4) how MPs impact technical and environmental systems. Critical reviews of existing analytical methods and recommendations on paths forward are an easy entry pathway for those new to the field to appreciate the current state, challenges, and research gaps in the field of analysis of MPs and NPs, including focusing on matrix specific considerations of MPs in water, as summarized by Elkhaltib et al. (6) and Delgado-Gallardo et al., (7) and soils, as assessed by Moeller et al. (8) Assessing ISO technical specifications for pyrolysis GC-MS for quantification of tire road wear particles, Rauert et al. found high variability in synthetic rubber and additive compositions across manufacturers. (9) Consequently, the authors found that using ISO methods had the potential to underreport environmental concentrations, and the authors suggested that further refinement of harmonization of analysis is needed. New methods for the identification of MPs are continuously being suggested, as exemplified by Primke et al., who explored the rapid and reliable method for determination of the size, shape, and number of MPs by quantum cascade laser-based hyperspectral infrared chemical imaging. (10) Comparing the performance of this technique to that of the existing state-of-the-art Fourier transform infrared microscopy analysis in a number of different environmental samples, the authors suggest this approach as a viable path forward as a rapid MPs monitoring approach with a highly detailed data set. To reduce time demands on the imaging and characterization of MPs, Hufnagl et al. developed automating data analysis following spectroscopic measurements with machine learning tools. (11) In some laboratory-based studies, the challenges of analysis of NPs and MPs were circumvented by using a conservative tracer embedded in the polymer, such as a trace metal, to more easily quantify and understand the fate and transport by using the metal as a proxy for plastics. For example, Keller et al. assessed the transport of particles of NPs and fibers of MPs through unsaturated porous media (12) and Heinze et al. examined the transport of NPs in soil via bioturbation by Lumbricicus terrestis (13) using this approach, which allowed the authors to track smaller particles with greater speed and accuracy. Understanding how macroplastics degrade into MPs and NPs can help in the generation of test materials that can be used across multiple studies, as reviewed by Bacha et al. (14) In this context, Pfohl et al. adapted a NanoRelease protocol using industry-relevant polymers to develop a parametrized mechanistic fragmentation model using varying ultraviolet doses and cryo-milling to measure the rates of fragmentation. (15) A number of studies addressed confounding factors for experimental design and artifacts when conducting ecotoxicity tests. For example, Hermsen et al. critically reviewed the quality criteria for MPs in biological samples, where the authors noted the variability and inability to directly compare results between studies may be due to the lack of harmonized methods. (16) Subsequently, the authors suggest 10 criteria to benchmark future studies in an effort to harmonize best practices in the future. Confounding factors in toxicity tests were assessed by Petersen et al., especially in relation to artifacts of dosing of NPs and MPs and the lack of control experiments. (17) Issues related to preservatives in commercial formulations were also highlighted by Pikuda et al., who specifically noted the acute toxicity of nondialyzed MPs to organisms, and consequently, toxicity was mainly associated with sodium azide, a preservative in the stock suspension of nanoplastics, and not the particles themselves. (18) However, in some cases, chemicals in MPs can play a role in toxicity, as noted by Kim et al. (19) Here, the authors found that adverse effects were mainly attributable to the extractable additives, and when these additives were extracted before organism exposure, the acute toxicity of test materials significantly decreased. Other papers highlighted in this virtual special issue assess experimental design to facilitate comparison of results across different studies. For example, Kooi and Koelmans note that many studies struggle with the diversity of MPs in environmental samples and current classification approaches do not capture the essentially continuous and diverse nature of environmental MPs. (20) Consequently, the authors created a three-dimensional probability distribution, and although this is a simplified concept, it could be especially helpful in probabilistic risk modeling. To better align methods used in MPs research for previously incomparable data sets with respect to MPs exposure assessments, Koelmans et al. suggest an approach to correct for differences in particle size, number, volume, and mass in different exposure tests to account for different types of MPs used to create a species sensitivity distribution. (21) Likewise, sample heterogeneity of MPs in environmental samples can also impact sampling and analysis efforts. Bai et al. critically analyzed sampling methods with the goal of developing harmonized methods with a specific focus on capturing the variable spatiotemporal riverine fluxes of MPs, (22) and Kittner et al. conducted a comprehensive screening of MPs in the Danube River basin with a harmonized analytical approach. (23) Morgado et al. assessed and modeled the random and systematic effects affecting the quantification of MPs using Poisson-log-normal distributions and the uncertainty from particle counting and provided a user-friendly spreadsheet to facilitate harmonization between research groups. (24) Finally, it is evident that the diversity of MPs, NPs, and plastics-added chemicals combined with the complexity of environmental test systems has resulted in conclusions that differ from study to study. Above, we have outlined several attempts at harmonization in the field, but one which is still large lacking is test materials that can be compared among laboratory groups. Currently, most laboratories are producing their own MPs and NPs in house, but harmonization would also benefit from a larger repository of well-characterized standards for analytical calibration and environmental fate and biological uptake comparisons. Another issue that requires further attention is the impact of various processes on the physiochemical surface characteristics of MPs and NPs, which can impact both their environmental transport and interactions with biological organisms. Plastics can also have indirect impacts on technical and environmental systems, (25−27) which is another area that should be explored in more depth in the future, as well. It is worth noting that analytical and experimental harmonization for other particulate pollutants, such as environmental health and safety assessments of engineered nanomaterials, took many years to develop and in some regards is still ongoing. Nevertheless, there are many lessons learned that could be incorporated into MPs and NPs research, including, for example, designing environmentally relevant test materials and exposure systems. (28) In the coming years, we look forward to seeing how harmonization progresses in this field of research to enable best practices that support both academic research and eventually more widespread monitoring and testing of MPs and NPs environmental contamination in the future. Denise M. Mitrano is an Assistant Professor at ETH Zurich, Switzerland, in the Environmental Systems Science Department. As an environmental analytical chemist, she focuses on the distribution and impacts of anthropogenic materials in technical and environmental systems. She is particularly interested in developing analytical tools to systematically understand the mechanisms and processes driving the fate, transport, and biological interactions of particles, such as engineered nanomaterials and nano- and microplastics. In this context, her research group uses these results to assess risks of anthropogenic materials across various ecosystems and scales. An interest in a safer by design approach for both nanomaterials and plastics is exemplified by working on the boundaries of environmental science, materials science, and policy to promote sustainability and environmental health and safety of new materials. Her work has recently been recognized by the Swiss National Science Foundation Marie Heim Vögtlin Prize for Outstanding Young Woman Researcher of the Year (2022), the 2022 James J. Morgan Early Career Award for Outstanding Contributions to Environmental Science from ES&T and the ACS Division of Environmental Chemistry, and the 2022 Emerging Investigator in Atomic Spectroscopy Award. She is currently serving as a Topic Editor with ES&T Letters. This article references 28 other publications. This article has not yet been cited by other publications. Denise M. Mitrano is an Assistant Professor at ETH Zurich, Switzerland, in the Environmental Systems Science Department. As an environmental analytical chemist, she focuses on the distribution and impacts of anthropogenic materials in technical and environmental systems. She is particularly interested in developing analytical tools to systematically understand the mechanisms and processes driving the fate, transport, and biological interactions of particles, such as engineered nanomaterials and nano- and microplastics. In this context, her research group uses these results to assess risks of anthropogenic materials across various ecosystems and scales. An interest in a safer by design approach for both nanomaterials and plastics is exemplified by working on the boundaries of environmental science, materials science, and policy to promote sustainability and environmental health and safety of new materials. Her work has recently been recognized by the Swiss National Science Foundation Marie Heim Vögtlin Prize for Outstanding Young Woman Researcher of the Year (2022), the 2022 James J. Morgan Early Career Award for Outstanding Contributions to Environmental Science from ES&T and the ACS Division of Environmental Chemistry, and the 2022 Emerging Investigator in Atomic Spectroscopy Award. She is currently serving as a Topic Editor with ES&T Letters. This article references 28 other publications.
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