Alavian Petroody Somayye Sadat, Hashemi Seyed Hossein, Škrlep Luka, Mušič Branka, van Gestel Cornelis A M, Sever Škapin Andrijana
Environmental Sciences Research Institute, Shahid Beheshti University, Tehran 1983963113, Iran.
Slovenian National Building and Civil Engineering Institute, Dimičeva ulica 12, 1000 Ljubljana, Slovenia.
Polymers (Basel). 2023 Nov 4;15(21):4322. doi: 10.3390/polym15214322.
Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance-Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation.
污水处理厂产生的生物固体（生物污泥）是微塑料（MPs）向环境排放的一个重要来源。在微塑料进入环境之前削弱其结构可能会加速其降解并减少其在环境中的暴露时间。因此，我们研究了在70°C下施加的UV-A和UV-C对污水污泥中常见的三种类型微塑料，即聚丙烯（PP）、聚乙烯（PE）和聚对苯二甲酸乙二酯（PET），使用三种形状（纤维、线条、颗粒）的影响。将微塑料置于生物固体悬浮液中接受紫外线辐射，并以空气和水作为对照。使用衰减全反射傅里叶变换红外光谱法（ATR-FTIR）研究微塑料的结构变化和降解情况，并用扫描电子显微镜（SEM）分析表面形态。紫外线照射导致所有PP样品中出现羰基和羟基。在PE和PET中，这些基团仅在生物固体悬浮液中形成。羰基和羟基的存在随着照射时间的增加而增加。总体而言，紫外线辐射对生物固体悬浮液中的微塑料影响最大。由于测试样品的表面积与体积之比会影响降解速率，纤维比其他两种塑料形状降解得更多。UV-A在降解微塑料方面比UV-C略有效。这些发现表明，紫外线辐射与升高的温度相结合会影响废水生物固体中聚合物的结构，从而加速其降解。
