Unveiling the microplastics degradation and its transformative effects on soil nutrient dynamics and plant health – A systematic review

Abstract

A growing web of microplastic pollution and a long human love affair with plastic use could leave a hidden legacy that silently suffocates the ecological balance and disrupts the soil-plant nexus. Therefore, the present systematic review aims to provide an updated understanding on microplastics transformation in soil via various degradation mechanisms affecting nutrient dynamics and plant health, with important perspectives for future research. A query comprising of potent keywords was run on pronounced databases, and retrieved records were screened out using PRISMA guidelines considering recent research advances. Microplastics are persistent and take a long time to degrade due to their polymeric structure. However, photochemical and microbial degradation remained in the foreground, whereby the degradation of microplastics by fungi is estimated to be higher than the bacteria. The presence of microplastics favors increased microbial activity and altered soil physicochemical properties, which can disrupt nutrient dynamics. Despite slow mineralization, microplastics containing a considerable amount of carbon can alter the C/N ratio and microbial interaction. Microplastics led to a notable rise in the diversity of soil microbes responsible for N-fixation and P-solubilization. Furthermore, plant health can also be directly affected by the uptake of secondary microplastics via roots or stomata and/or indirectly by microplastic-induced alteration in soil properties, microbial activities, and/or nutrient dynamics. The ecotoxicity of microplastics may depend on the type of soil, polymer, and plant species types, but clear effects on growth parameters, photosynthesis, the antioxidant system, and enzymatic activities. Finally, research gaps are highlighted as an outlook for future studies on the complexity of soil ecosystems, plant health, and food security in response to microplastics pollution.