As the emerging contaminants, the behavior and fate of microplastics (MPs) were highly related to the interactions with surrounding organic matters. However, information on the effects of molecular sizes of organic matters on the interaction is still lacking. In this study, the bulk algal-derived organic matter (AOM) samples were obtained and further fractionated into high molecular weight (HMW-, 1kDa-0.45 μm) and low molecular weight (LMW-, < 1 kDa) fractions. The interaction between MPs [polyethylene (PE) and polystyrene (PS)] and these MW-fractionated AOMs were characterized by dissolved organic carbon, fluorescence and absorbance spectroscopy, and fourier transform infrared (FTIR) analysis. Results showed that presence of AOM could effectively inhibit the release of additives from MPs. Further analysis found that the inhibition extents decreased in the order of HMW- > bulk > LMW-AOM. The absorbance and fluorescence spectroscopy showed that aromatic protein-like substances in HMW fraction exhibited higher adsorption affinity to MPs than the bulk and LMW counterparts. The strong sorption of aromatic substances may offer more binding sites for additives to inhibit the release of organic substances. Moreover, two dimensional FTIR correlation spectroscopy revealed that the HMW non-aromatic substances were preferentially adsorbed onto PS, which led to an enhanced adsorption capacity to additives by forming H-bonding. Therefore, the MW- and component-dependent heterogeneities of AOM samples must be fully considered in evaluating the environmental behavior of MPs.

中文翻译：

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在藻类衍生有机物存在的情况下，微塑料中有机物的释放抑制：分子量依赖性抑制异质性的影响


作为新兴污染物，微塑料（MP）的行为和命运与周围有机物的相互作用高度相关。然而，关于有机物分子大小对相互作用影响的信息仍然缺乏。在本研究中，获得了大量藻类有机物 (AOM) 样品，并进一步分为高分子量（HMW-，1kDa-0.45 µm）和低分子量（LMW-，< 1 kDa）部分。通过溶解有机碳、荧光和吸收光谱以及傅里叶变换红外 (FTIR) 分析来表征 MP [聚乙烯 (PE) 和聚苯乙烯 (PS)] 与这些 MW 分级 AOM 之间的相互作用。结果表明，AOM 的存在可以有效抑制 MPs 中添加剂的释放。进一步分析发现，抑制程度按HMW->bulk>LMW-AOM的顺序降低。吸光度和荧光光谱表明，HMW 级分中的芳香族蛋白样物质比本体和 LMW 级分中的芳香族蛋白类物质对 MPs 表现出更高的吸附亲和力。芳香物质的强吸附作用可以为添加剂提供更多的结合位点，从而抑制有机物质的释放。此外，二维 FTIR 相关光谱显示，HMW 非芳香族物质优先吸附在 PS 上，通过形成氢键，增强了对添加剂的吸附能力。因此，在评估MP的环境行为时，必须充分考虑AOM样品的MW和组分依赖性异质性。