Microplastics and nanoplastics in the soil-plant nexus: Sources, uptake, and toxicity

The agricultural sector is increasingly dependent upon the use of plastic products to enhance productivity. In addition to many incidental inputs, plastic fragments are progressively accumulating in soil following the degradation of plastic products. Microplastics (MPs, <5 mm) and nanoplastics (NPs, <1 µm) in agricultural soils have caused substantial concerns recently. The insidious interactions between plants, soil, and MPs/NPs in the agricultural environment could affect soil health, crop productivity, and threaten food safety and human health. Importantly, finer NPs can be taken up by plants, induce oxidative stress and negatively affect plant growth. Even though interactions of MPs/NPs with plants in the plant-soil nexus have been reported, a comprehensive review of the state of knowledge is lacking, which hinders continued progress in this emerging field. This review aims to fill the gap by extensively summarizing MPs/NPs sources in agriculture, techniques to investigate, impact on soil properties and accumulation in the plants. The synergistic effect of organic and inorganic co-contaminants and MPs/NPs are highlighted due to the widespread presence of these chemicals in agricultural soils. This review also presented possible mechanisms of MPs/NPs phytotoxicity. Although new information is emerging there is a paucity of data on the fate and impact of MPs/NPs in the plant-soil nexus. More efforts are needed to elucidate the fate and impact of MPs/NPs in agricultural soils to gain a deeper understanding of their health and safety implications.