Environmental fate of microplastics and common polymer additives in non-biodegradable plastic mulch applied agricultural soils

Numerous studies have been conducted to investigate the impact of microplastics on soil eco-system, yet little attention has been given to the specific effects of mulch microplastics and the leaching of plastic additives from mulch films. This review inspects the propensity of commonly used plastic additives in mulch films, such as Di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), and benzophenones (BPs), to migrate into soils and pose potential risks to soil biota. Further, we highlight the degradation of non-biodegradable plastic mulch films over time, which leads to an increase in the release of plastic additives and microplastics into agricultural soils. DEHP has been detected in high concentrations for example 25.2 mg/kg in agricultural soils, indicating a potential risk of uptake, translocation and accumulation in plants, ultimately altering soil physicochemical properties and affecting soil microflora and invertebrates. The review also explores how exposure to ultraviolet (UV) radiation and microbial activities accelerates the weathering of mulch films. Moreover, the resultant plastic additives and mulch microplastics can lead to genotoxicity and growth inhibition in earthworms (Eisenia fetida) and negatively impact the soil microbiome. Despite the significant implications, there has been a lack of comprehensive reviews comparing the effects of non-biodegradable mulch film additives on agricultural soil flora and fauna. Therefore, this review addresses the knowledge gaps providing a bibliometric analysis and eco-toxicological evaluation, discussing the challenges and future perspectives regarding mulch plastic additives and microplastics, thus offering a comprehensive understanding of their impact.