The Ultraviolet Irradiation Aging Characteristics of Microplastics in Soil under the Action of Biochar

Microplastics (MPs) coexist with biochar (BC) in soil. However, studies of the effects of BC application on MP aging in soils are few. Therefore, this study investigated the BC-mediated aging behavior of persistent microplastics (PMPs) and biodegradable microplastics (BMPs). Ultraviolet (UV) irradiation was used as the aging method, and four BC concentrations were applied to soil containing PMP-polyethylene (PE) and BMP-polybutylene adipate terephthalate (PBAT), which was analyzed to assess the effects of different BC concentrations on MP aging behavior in soil. The results revealed that the addition of BC accelerated the surface aging of PE and PBAT. Changes in carbonyl index (CI) and hydroxyl index (HI) indicated that high BC concentrations promoted UV-irradiation aging of PE and PBAT. Overall, 2 and 4% BC play a positive role in the formation of -OH groups in PE and PBAT. PE was susceptible to electrophilic attack, whereas PBAT underwent both electrophilic and nucleophilic attack.