Faikhaw Orasai, Wagner Stephan, Rynek Robby, Peng Guyu, Materić Dušan, Reemtsma Thorsten
Department of Environmental Analytical Chemistry, Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, 04318 Leipzig, Germany.
Institute for Analytical Research, Hochschule Fresenius, Limburger Str. 2, 65510 Idstein, Germany.
Sci Total Environ. 2025 Jan 1;958:177876. doi: 10.1016/j.scitotenv.2024.177876. Epub 2024 Dec 7.
Riverine suspended matter (river-SPM) contains large amounts of natural particles consisting of cellulose and lignin, posing a challenge for microplastic (MPs) analysis. Additionally, organic matter composition under seasonal and discharge-related dynamics varies for each river. Therefore, this study attempted to identify a universally applicable clean-up procedure to remove matrix particles with high organic matter content, mainly plant debris, from the river-SPM samples. This study tested six digestion procedures adapted from existing (ligno)cellulosic digestion/oxidation methods with a river-SPM sample followed by density separation using sodium polytungstate. From these, NaOCl treatment (CL) showed the highest efficiency of organic matter removal, eliminating 96-100 % of the matrix weight. Exposure of tested MPs (in size range of 100-500 μm) in the CL protocol showed no adverse effect on polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene terephthalate (PET). Similarly, no detrimental matrix effects were found on 100 μm spherical PS standard particles spiked in the river-SPM. This procedure achieved high recovery rates of tested plastics (92-100 %). In terms of method applicability, the procedure was successfully applied to samples from different seasons containing various matrix concentrations and compositions. Although samples with high amounts of plant debris needed to undergo this procedure twice, only minor alteration of the particle surface and IR spectrum of PS presented and no adverse effect on PP. To further tackle the high and varied concentration of plant-derived matrix in river-SPM samples, a novel sequential oxidation protocol (2DOCL) combining cellulose dissolution, Fenton's oxidation, and NaOCl oxidation was developed, resulting in a more (time) effective and predictable process, demonstrating no severely destructive effect on tested plastics. The sequential digestion protocol can be optimized for certain matrices as applying all steps will not be necessary.
河流悬浮物质（river-SPM）包含大量由纤维素和木质素组成的天然颗粒，这给微塑料（MPs）分析带来了挑战。此外，每条河流中与季节和流量相关的动态变化下的有机质组成各不相同。因此，本研究试图确定一种普遍适用的净化程序，以从river-SPM样品中去除高有机质含量的基质颗粒，主要是植物碎片。本研究采用了六种从现有的（木质）纤维素消化/氧化方法改编而来的消化程序，对一个river-SPM样品进行处理，随后使用多聚钨酸钠进行密度分离。其中，次氯酸钠处理（CL）显示出最高的有机质去除效率，消除了96%-100%的基质重量。在CL方案中测试的MPs（尺寸范围为100-500μm）对聚丙烯（PP）、聚乙烯（PE）、聚苯乙烯（PS）和聚对苯二甲酸乙二酯（PET）没有不利影响。同样，在river-SPM中添加的100μm球形PS标准颗粒也未发现有害的基质效应。该程序实现了测试塑料的高回收率（92%-100%）。在方法适用性方面，该程序成功应用于来自不同季节、含有不同基质浓度和组成的样品。尽管含有大量植物碎片的样品需要进行两次该程序，但PS颗粒表面和红外光谱仅有轻微变化，对PP没有不利影响。为了进一步应对river-SPM样品中高浓度且多样的植物源基质，开发了一种新的顺序氧化方案（2DOCL），该方案结合了纤维素溶解、芬顿氧化和次氯酸钠氧化，产生了一个更（节省时间）有效且可预测的过程，对测试塑料没有严重的破坏作用。顺序消化方案可以针对特定基质进行优化，因为并非所有步骤都有必要应用。
