Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA.
Biological Sciences and Environmental Program, Loyola University New Orleans, New Orleans, LA, USA.
Sci Total Environ. 2022 Dec 10;851(Pt 2):158022. doi: 10.1016/j.scitotenv.2022.158022. Epub 2022 Aug 12.
Understanding the fate of plastics in the environment is of critical importance for the quantitative assessment of the biological impacts of plastic waste. Specially, there is a need to analyze in more detail the reputed longevity of plastics in the context of plastic degradation through oxidation and fragmentation reactions. Photo-oxidation of plastic debris by solar UV radiation (UVR) makes material prone to subsequent fragmentation. The fragments generated following oxidation and subsequent exposure to mechanical stresses include secondary micro- or nanoparticles, an emerging class of pollutants. The paper discusses the UV-driven photo-oxidation process, identifying relevant knowledge gaps and uncertainties. Serious gaps in knowledge exist concerning the wavelength sensitivity and the dose-response of the photo-fragmentation process. Given the heterogeneity of natural UV irradiance varying from no exposure in sediments to full UV exposure of floating, beach litter or air-borne plastics, it is argued that the rates of UV-driven degradation/fragmentation will also vary dramatically between different locations and environmental niches. Biological phenomena such as biofouling will further modulate the exposure of plastics to UV radiation, while potentially also contributing to degradation and/or fragmentation of plastics independent of solar UVR. Reductions in solar UVR in many regions, consequent to the implementation of the Montreal Protocol and its Amendments for protecting stratospheric ozone, will have consequences for global UV-driven plastic degradation in a heterogeneous manner across different geographic and environmental zones. The interacting effects of global warming, stratospheric ozone and UV radiation are projected to increase UV irradiance at the surface in localized areas, mainly because of decreased cloud cover. Given the complexity and uncertainty of future environmental conditions, this currently precludes reliable quantitative predictions of plastic persistence on a global scale.
了解塑料在环境中的命运对于定量评估塑料废物的生物影响至关重要。特别是，需要更详细地分析在氧化和碎片反应的背景下塑料所谓的耐久性。太阳紫外线辐射（UVR）对塑料碎片的光氧化使材料容易随后发生碎片。氧化后和随后暴露于机械应力下产生的碎片包括次级微或纳米颗粒，这是一类新兴的污染物。本文讨论了 UV 驱动的光氧化过程，确定了相关的知识空白和不确定性。在光碎片过程的波长敏感性和剂量响应方面存在严重的知识空白。考虑到自然紫外线辐射的异质性，从沉积物中没有暴露到浮漂、海滩垃圾或空气传播塑料的完全紫外线暴露，据认为，UV 驱动的降解/碎片的速率也将在不同地点和环境小生境之间差异很大。生物现象如生物污垢将进一步调节塑料对紫外线辐射的暴露，同时也可能独立于太阳紫外线辐射对塑料的降解和/或碎片产生影响。由于保护平流层臭氧的《蒙特利尔议定书》及其修正案的实施，许多地区的太阳紫外线辐射减少，将以不同的地理和环境区域不均匀的方式对全球 UV 驱动的塑料降解产生影响。全球变暖、平流层臭氧和紫外线辐射的相互作用预计将增加局部地区表面的紫外线辐射，主要是因为云量减少。考虑到未来环境条件的复杂性和不确定性，这目前使得无法对全球范围内塑料持久性进行可靠的定量预测。
