Environmental fate, aging, toxicity and potential remediation strategies of microplastics in soil environment: Current progress and future perspectives

Effects of polyurethane microplastics combined with cadmium on maize growth and cadmium accumulation under different long-term fertilisation histories

Agricultural production uses different types of fertilisation treatments, typically employing the combined application of organic fertiliser (OF) or organic-inorganic fertiliser (OIF) to improve soil quality. When coupled with cadmium (Cd), microplastics (MPs) affect plant growth and Cd accumulation in soils treated with different fertilisers. This study systematically examined the effects of polyurethane (PU) MPs coupled with Cd on the growth characteristics, root metabolite characteristics, rhizosphere bacterial community structure, and Cd bioavailability of maize under different long-term fertilisation treatments and soil types (red/cinnamon soil). The combined effects of PU MPs and Cd on maize growth differed across fertilisation treatments. Under OF, maize plants accumulated more Cd than under OIF. The accumulation of Cd in maize plants in red soil was twice that in cinnamon soil. Under OF, PU MPs promoted Cd activation by decreasing the soil pH, while root metabolites promoted Cd adsorption sites by synthesising specific amino acids, degrading aromatic compounds, and synthesising pantothenic acid and coenzyme A. Under OF, PU MPs can lower the soil pH to promote the activation of cadmium, while root metabolites promote root growth and increase cadmium adsorption sites by synthesizing specific amino acids, degrading aromatic compounds, and synthesizing pantothenic acid and coenzyme A, hereby promoting root Cd absorption. Under OIF, PU MPs act by influencing the biosynthesis of amino acids in root metabolites, enriching energy metabolism pathways, promoting the transport and translocation of mineral nutrients, thereby amplifying the "toxic effects" of Cd. This study provides new insights into the risk assessment of PU MPs and Cd coupling under different fertilisation treatments, and suggests that the prevention and control of combined PU MPs and Cd pollution in red soil under OF treatment should receive more attention in the future.

Effect of microplastics used in agronomic practices on agricultural soil properties and plant functions: Potential contribution to the circular economy of rural areas

The extensive use of plastic materials and their improper disposal results in high amounts of plastic waste in the environment. Aging of plastics leads to their breakdown into smaller particles, such as microplastics (MPs) and nanoplastics. This research investigates plastics used in agricultural practices as they contribute to MP pollution in agricultural soils. The distribution and characteristics of MPs in agricultural soils were evaluated. In addition, the effect of MPs on soil properties, the relationship between MPs and metals in soil, the effect of MPs on the fate of pesticides in agricultural soils and the influence of MPs on plant growth were analysed, discussing legume, cereal and vegetable crops. Finally, a brief description of the main methods of chemical analysis and identification of MPs is presented. This study will contribute to a better understanding of MPs in agricultural soils and their effect on the soil-plant system. The changes induced by MPs in soil parameters can lead to potential benefits as it is possible to increase the availability of micronutrients and reduce plant uptake of toxic elements. Furthermore, although plastic pollution remains an emerging threat to soil ecosystems, their presence may result in benefits to agricultural soils, highlighting the principles of the circular economy.

Micro/nanoplastics: Critical review of their impacts on plants, interactions with other contaminants (antibiotics, heavy metals, and polycyclic aromatic hydrocarbons), and management strategies

Microplastic/nanoplastics (MPs/NPs) contamination is not only emerging threat to the agricultural system but also constitute global hazard to the environment worldwide. Recent review articles have addressed the environmental distribution of MPs/NPs and their single-exposure phytotoxicity in various plant species. However, the mechanisms of MPs/NPs-induced phytotoxicity in conjunction with that of other contaminants remain unknown, and there is a need for strategies to ameliorate such phytotoxicity. To address this, we comprehensively review the sources of MPs/NPs, their uptake by and effects on various plant species, and their phytotoxicity in conjunction with antibiotics, heavy metals, polycyclic aromatic hydrocarbons (PAHs), and other toxicants. We examine mechanisms to ameliorate MP/NP-induced phytotoxicity, including the use of phytohormones, biochar, and other plant-growth regulators. We discuss the effects of MPs/NPs -induced phytotoxicity in terms of its ability to inhibit plant growth and photosynthesis, disrupt nutrient metabolism, inhibit seed germination, promote oxidative stress, alter the antioxidant defense system, and induce genotoxicity. This review summarizes the novel strategies for mitigating MPs/NPs phytotoxicity, presents recent advances, and highlights research gaps, providing a foundation for future studies aimed at overcoming the emerging problem of MPs/NPs phytotoxicity in edible crops.

Microplastic contamination in the agricultural soil-mitigation strategies, heavy metals contamination, and impact on human health: a review

Microplastic pollution has emerged as a critical global environmental issue due to its widespread distribution, persistence, and potential adverse effects on ecosystems and human health. Although research on microplastic pollution in aquatic environments has gained significant attention. However, a limited literature has summarized the impacts of microplastic pollution the agricultural land and human health. Therefore, In the current review, we have discussed how microplastic(s) affect the microorganisms by ingesting the microplastic present in the soil, alternatively affecting the belowground biotic and abiotic components, which further elucidates the negative effects on the above-ground properties of the crops. In addition, the consumption of these crops in the food chain revealed a potential risk to human health throughout the food chain. Moreover, microplastic pollution has the potential to induce a negative impact on agricultural production and food security by altering the physiochemical properties of the soil, microbial population, nutrient cycling, and plant growth and development. Therefore, we discussed in detail the potential hazards caused by microplastic contamination in the soil and through the consumption of food and water by humans in daily intake. Furthermore, further study is urgently required to comprehend how microplastic pollution negatively affects terrestrial ecosystems, particularly agroecosystems which drastically reduces the productivity of the crops. Our review highlights the urgent need for greater awareness, policy interventions, and technological solutions to address the emerging threat of microplastic pollution in soil and plant systems and mitigation strategies to overcome its potential impacts on human health. Based on existing studies, we have pointed out the research gaps and proposed different directions for future research.