微塑料
光降解
低密度聚乙烯
差示扫描量热法
傅里叶变换红外光谱
环境化学
聚苯乙烯
结晶度
聚乙烯
材料科学
化学
聚合物
化学工程
有机化学
复合材料
光催化
热力学
物理
工程类
催化作用
作者
Gholamreza Bonyadinejad,Maryam Salehi,Amali Herath
标识
DOI:10.1016/j.scitotenv.2022.156385
摘要
The accelerated use of plastic products for agricultural practices has raised global concern regarding their negative impacts on soil health. This study aims to better understand the combined influence of polymer characteristics and environmental conditions on microplastic photodegradation within the agricultural soil system. For this purpose, the photodegradation behavior of low density polyethylene (LDPE) microplastics was studied through accelerated UVA radiation experiments under two different relative humidity (RH10 and RH70) and soil deposition conditions. The variations of plastics' surface physiochemistry due to the accelerated photodegradation were studied using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), and Field Emission Scanning Electron Microscopy (FE-SEM). The carbonyl and vinyl indices were calculated using the ATR-FTIR information to compare the degree of microplastics' photodegradation. The plastics' bulk characteristics, including the percentage of crystallinity and molecular weight distributions, were examined using the Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography (GPC). Furthermore, the extent of UVA light interaction with the microplastics was studied by determining spectral quantum yield. The results demonstrated that new LDPE microplastics with a lower molecular weight (Mw = 233 kD) were subjected to a greater extent of photodegradation than those with greater molecular weight (Mw = 515 kD). Elevated relative humidity (RH70) limited the photooxidation process of microplastics and consequently reduced the surface chemistry alterations. Deposition of soil particles with respect to the plastic particles impacted the photodegradation behavior. The microplastics covered by soil particles were not degraded, unlike those deposited next to the soil particles. The knowledge developed through this study could encourage the farmers and agricultural stakeholders to apply more efficient practices to remove plastic residuals after harvesting and conduct proper plastic disposal practices to protect soil health.
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