Soil microplastic pollution has attracted wide attention. Due to the complexity of soil matrix, there is no standard method for extracting microplastics from soil. In order to explore the standard separation method of soil microplastics, the extraction effects of three different treatment methods of pre-digestion, post-digestion and pre-digestion and post-digestion on polyethylene (PE), polypropylene (PP), polystyrene (PS), polyamide resin (PA), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), polyhydroxyalkanoate (PHA) and polybutylene adipate (PBAT) in red soil, cinnamon soil and black soil were evaluated. The results show that the total recovery rate of microplastics in the three soils ranged from 96% to 102%. Considering the removal of matrix effect and the degree of damage to the target microplastics, the optimal digestion scheme is post-digestion of soil. The optimal soil microplastics extraction method is based on the microplastics separation device with saturated ZnCl₂ solution for 3 times density flotation, and then 5 μm aperture nitrocellulose filter membrane vacuum filtration, using 30% (w) H₂O₂ under the condition of 70 ℃ to digest and remove soil organic matter. After the completion of digestion, vacuum filtration is performed again. The organic matter in the soil can then be effectively removed while extracting microplastics.

Microplastic pollution in the soil has become a growing public concern globally. The application of livestock and poultry manure compost is considered to be an important pathway for the accumulation of microplastics in soils. However, the understanding of microplastic pollution in fecal compost is still limited. In this study, the distribution characteristics of microplastics in composts of commercial chicken, cow, goat, and pig manure in four provinces of China were investigated. Microplastics in manure composts were extracted by sieving and digestion with Fenton's reagent, and their color, size, shape, type, and abundance were further analyzed. The results show that transparent, black, red, and blue are the dominant colors of microplastics in manure composts. The shapes of microplastics in manure composts include fibers, fragments, films and granules, with fibers being the highest. The dominant size of microplastics in manure composts is <1 mm, which accounted for 27.6% to 69.5%; and the dominant polymer types of microplastics in manure composts are polyester (PES), polypropylene (PP), and polyethylene (PE), which accounted for 87.8% to 97.0%. The abundance of microplastics in manure composts ranges from (2 054.8 ± 493.9) to (9 131.0 ± 600.7) items·kg^-1. The results of this study confirmed that manure compost is an important source of microplastics in agricultural soil, and the contribution of manure compost application to the abundance of microplastics in agricultural soil of China is estimated to be 1.1 × 10¹⁴ items per year. The above results provide basic data and scientific basis for revealing the pollution characteristics and regional differences of microplastics in manure composts, and the source identification of microplastics in agricultural soils.

Large amounts of plastic wastes have accumulated in terrestrial ecosystem due to the abuse of plastic products. Soil ecosystem is facing great stresses by the micro/nano plastics, the fractions that fragmented from the weathered plastic wastes, and by extreme weather events such as high temperature, drought, and heavy rainfall caused by the global climate change. The climatic environmental factors such as temperature and precipitation affect the occurrence, transportation, conversion, and toxicity of micro/nano plastics in soil. The effects of different climatic factors on pollution characteristics and migration of micro/nano plastics in soil were reviewed. The combined effects of different climatic factors and micro/nano plastics on the soil ecology were also discussed. It was found that warming, drought, freeze-thaw, and flood could increase the abundance of micro/nano plastics in soil and accelerate the aging of micro/nano plastics. The soil properties, nutrient cycling, and plant growth could be influenced by the combination of climatic factors and micro/nano plastics. The soil carbon and nitrogen cycling were significantly affected by warming or drought accompany with existences of micro/nano plastics. Future research should focus on the effects of typical climatic factors on the aging characteristics and environmental behavior of micro/nano plastics and their joint effects on key biogeochemical cycling processes in soil.

Taking polystyrene micro-particles (PS) and tylosin (TYL) as experimental objects, the effect of the application of PS on adsorption kinetics and thermodynamics characteristics of TYL onto four typical Chinese farmland soils with different physicochemical properties was studied. The results show that PS could enhance the adsorption capacity of those four soils towards TYL. The enhancement was more significant on clay soils than that on loam soils. Soils added with 1% PS had little impact on the adsorption process of TYL, which could be well fitted with the pseudo-second-order kinetic model (R²>0.97). The sorption process was divided into three stages as external diffusion, intra-particle diffusion and adsorption equilibrium according to the intraparticle diffusion model. The adsorption isotherm was close to the Freundlich or Langmuir model (R²>0.97). The adsorption capacity of TYL onto soil with PS was apparently weakened along with the increase of pH or ionic strength. The adsorption was a multiphase process with hydrophobic and electrostatic interactions playing the dominant roles.

As a new pollutant, microplastics pollution has become a global environmental issue. Agricultural soils contaminated with microplastics pose a potential threat to the food chain and terrestrial ecosystems. This study utilized a mesocosm device to simulate changes of different biotic (springtail, earthworm density, plant roots) and abiotic (type and aging of microplastics, exposure time, flooding) factors in agricultural soils and explored their effects on the vertical migration of microplastics in the soil driven by earthworms. Results show that the vertical migration of microplastics decreased with increasing soil depth, and was positively influenced by springtail and high densities of earthworms. The growth of plant roots tended to retain microplastics in the surface soil layer and reduce the vertical migration of microplastics by earthworms. The type of microplastics also had an impact on vertical migration in the order of PE > PS > PET. Short-term aging had no significant effect on the vertical migration of microplastics in soil, but exposure time and flooding promoted the migration of microplastics to deeper soil layers. This study provides a scientific basis for understanding the vertical migration patterns and influencing factors of microplastics in agricultural soils under earthworm activities.

Microplastic pollution, as a global environmental problem, still shows huge challenges in frontier scientific issues. Currently, the research is increasing on the uptake of microplastics by plants, as well as response of plants to microplastics. However, research on environmental factors affecting the uptake of microplastics by plants is still limited. Based on the hydroponic experiment in laboratory, the quantitative uptake of polystyrene (PS) microplastics (0.2 μm) by wheat seedling (Triticum aestivum) was investigated under different temperature and humidity conditions (high transpiration environment: 30 ℃, 55% RH; low transpiration environment: 10 ℃, 85% RH). Furthermore, the changes in wheat growth and the physiological state were also analyzed, including indicators of morphology, photosynthesis and biochemistry. The results show that the accumulation amount of microplastics in wheat increased significantly with the increase of exposure concentration. Besides, the uptake amount of microplastics by wheat roots was 1.5 times higher in high transpiration environment than those in low transpiration environment. Under high transpiration environment, PS microplastics inhibited growth of wheat root and the activity of peroxidase in wheat shoot. Under the condition of high concentration with 200 mg·L^-1 of PS microplastics, it showed a significant decrease in the content of chlorophyll b but significant increase in the content of malondialdehyde in wheat roots and activity of superoxide dismutase in wheat shoots. Under low transpiration environment, a high concentration (200 mg·L^-1) of PS microplastics caused the content of malondialdehyde significantly increased in wheat shoots. But there were no obvious changes in photosynthesis and the activity of antioxidize in wheat. In conclusion, this study provides powerful evidences that the uptake of microplastics and the corresponding phytotoxic effects on wheat seedling are closely related to the environmental temperature and humidity, as well as the exposure concentration of PS microplastics. The results of this study can provide technical support for the quantitative analysis of uptake and transfer of microplastics by higher plants, and further provide scientific basis for the risk assessment of microplastics in terrestrial ecosystems.

Polyvinyl chloride (PVC) microplastics are commonly found in greenhouse soils. They are highly phytotoxic and pose a serious threat to plant growth and development. Therefore, measures to reduce the phytotoxicity of PVC microplastics are urgently needed. Biochar is known for its strong adsorption capacity. It can effectively passivate soil contaminants and has been widely used in the remediation of soil contamination. Additionally, biochar has exhibited great application potential for improving soil quality and increasing crop yields. To determine the effect of biochar on PVC microplastic phytotoxicity in greenhouse soils, the growth, physiological and with biochemical indices of lettuce (Lactuca sativa) were analyzed under single exposure to PVC microplastics and combined exposure to PVC microplastics and with biochar at different concentrations. The results show that the chlorophyll content of lettuce leaves exposed to single PVC microplastics was significantly increased compared to the control group (P<0.01). However, the biomass of root and shoot of lettuce was reduced by 23.54% and 12.04%, respectively. This may be attributed to the adhesion of PVC microplastics to the surface of lettuce roots, which induced the production and accumulation of hydrogen peroxide (H₂O₂) in the roots and caused oxidative damage, thus affecting the normal physiological function of the roots. The addition of 0.5% to 2.5% biochar to the PVC microplastics-contaminated soil resulted in a decrease in malondialdehyde (MDA) levels in lettuce roots and leaves and an increase in lettuce biomass compared to the single PVC microplastics exposure treatment group. However, the high concentration (5.0%) of biochar exacerbated the oxidative damage to lettuce roots and attenuated its growth-promoting effect on lettuce. These results suggest that the phytotoxicity of soil microplastics can be mitigated by the addition of appropriate amounts of biochar, and can provide a scientific basis for addressing soil microplastic pollution in agriculture.

Soil has become an important gathering place for microplastics (MPs) due to agricultural activities, atmospheric deposition, and surface runoff. The accumulation of microplastics in soil affects the growth and development of terrestrial plants, posing a threat to the safety of terrestrial ecosystems and food chains. Therefore, it is crucial to study the effects of microplastics on terrestrial plant growth and development. This article reviews research progress on the effects of microplastics on plant growth and development as well as on rhizosphere environments, and proposes prospects and suggestions for strengthening related research. Microplastics can adhere to plant surfaces, enter into plants through root tips, affect seed germination and root system development, induce oxidative stress responses, alter photosynthetic intensity, produce cytotoxicity and genotoxicity while affecting plant metabolism and nutrient absorption. The phytotoxicity of microplastics depend on their characteristics (concentration, size, shape, composition and charge) as well as different plants at various stages of growth. Microplastics can also change the characteristics of plant rhizosphere soil and microbial communities, indirectly affecting plant growth. This article summarizes research on the effects of microplastics on terrestrial plant growth and rhizosphere environment, and discusses future research directions on MPs in soil-plant system, providing scientific basis and technical support for risk prevention and control of microplastic pollution in soil and land ecosystems.

Micro/nano plastics (MNPs) is a newly emerging class of pollutant widely distributed in soil. MNPs can affect soil animals and cause ecological toxicity risks. In this paper, an updated review of research progress in this aspect has been conducted. Common soil animals such as earthworms, nematodes, and spring worms can ingest MNPs and affect the distribution of MNPs in soil through digestion and excretion. The toxic effects of MNPs can manifest at various levels, including individual, tissue, and molecular levels, causing effects such as growth and development delays, altered motor behavior, reproduction toxicity and neurotoxicity in soil animals. The toxic effects of MNPs are related to mechanisms such as intestinal injury, metabolic changes, oxidative stress, and abnormal expression of related genes, which may vary depending on the type and size of MNPs. The toxicity of MNPs is also related to the release of plastic additives and other pollutants loaded by MNPs. In addition, soil animals can transmit MNPs to humans by becoming a food or a part of the food chain and cause health risks. Finally, future research directions are outlined.

Microplastics, as a new type of pollutant, are widely present in various environmental media. The contamination of microplastics in soil environments has attracted global attention. The theme of this study revolves the contamination of microplastics in agricultural soil. Based on a summary and analysis of the latest research progress at home and abroad, a review was made of the impact of microplastics on the physicochemical properties of agricultural soil, soil microbial biomass, microbial community structure and function. Microplastics that enter agricultural soil through agricultural activities and other pathways will undergo weathering and degradation under non-biological and biological processes, and affect soil physicochemical properties, nutrient cycling, and the interaction of pollutants, thereby affecting soil microbial biomass, microbial community structure and diversity, soil enzyme activity, and soil biogeochemical processes such as carbon and nitrogen cycling, as well as pollutants degradation. The impacts of microplastics on the above indicators are related to various factors such as the properties of microplastics, soil type, and exposure conditions. This paper provides a prospect for future research directions on microplastics in soil, in the hope of providing reference and ideas for future research.

Extensive use of plastic products in daily life generates a huge sum of microplastics in soil environment. In recent years, research on microplastics has become a hot topic because of their small size, difficulty in degradation, ease to transfer with the food chain, and other characteristics. Based on existing literature, this review systematically analyzes how microplastics affect soil microbial metabolism and soil activity by changing soil physical and chemical properties and microbial ecology. Also, this review summarizes in detail the effects of microplastics on CO₂, N₂O, and CH₄ emissions. Finally, the mechanism of soil greenhouse gas emissions, the impact of different types of microplastics, and the advanced understanding of microplastics under actual soil conditions are discussed on the basis of available literatures.

Micro/nano plastics (MNPs) pollution has evolved into a global environmental issue that must be addressed. MNPs can enter the soil and accumulate in the soil for long-term and thus pose a potential risk to soil ecosystem health. From the perspectives of soil biological health effects and food chain risks, this paper reviews the research progress in the investigation of soil MNPs, discusses the effects of soil MNPs on plants, animals, and microorganisms, and summarizes the transport of MNPs in terrestrial organisms and the food chains. In addition, the future research directions of MNPs in soils are also prospected. MNPs exist widely in soils with different functions, and can be absorbed by plants, ingested by animals, and thus entering the human body through the terrestrial food chain. In the future, it is necessary to strengthen the research on the pollution process and biological health effects of MNPs in soil, and to strengthen the risk assessment of MNPs in the soil eco-system and the food chain transmission, so as to provide scientific guidance and technical methodological reference for the monitoring, control and management of MNPs in soils.

There is an increasing application of biodegradable plastics as sustainable alternative due to the serious pollution of traditional non-biodegradable plastics. However, their relatively slow degradation rates under natural environmental conditions still pose potential ecological and environmental risks. Until now, limited studies have been carried out to study the nanoscale degradation mechanism and fragmentation potential of biodegradable plastics in soil environment concerning global warming. In the present study, the biodegradable bag-derived microplastics (polylactic acid, PLA) were selected to analyze the changes of their physicochemical properties on nanoscale in soil environment at different temperatures (room temperature at 25 ℃ and high temperature at 50 ℃) for 0, 7 and 14 days aging based on an atomic force microscopy-infrared spectroscopy system (AFM-IR). The results show that the surface roughness of PLA gradually increased with aging time (7 d, 14 d) at both the two temperatures with highest roughness was observed at 50 ℃, indicating that the surface fragmentation of PLA was faster in soil environment at higher temperature. Nano-infrared spectrum (nanoIR) imaging analysis show that the signal of C-O functional group and its proportion of distribution area were much higher on aged PLA surface (37.9%-50.8%) than unaged ones (21.1%), and the signal of C-O was stronger at 50 ℃ than at 25 ℃ after 14 days aging. Similarly, compared to unaged ones, the C=O signal and its distribution area on aged PLA surface were also enhanced, indicating an oxidization process during aging. The results of Lorentz contact resonance (LCR) analysis reveal that the frequency of the first vibration peak on PLA surface at 25 ℃ followed the sequence of 14 days >7 days > initial control, suggesting an increased rigidity of PLA surface with aging time. In addition, the rigidity of PLA surface was enhanced after 7 days but got weak after 14 days aging. Nano thermal analysis (nano-TA) show that the glass transition temperature (Tg) of 7 days-aged PLA surface increased compared to unaged ones. However, the Tg decreased and its distribution heterogeneity was enlarged at 50 ℃ after 14 days aging. These results implied an exfoliation corrosion of aged PLA surface. Future research should focus on the surface exfoliation corrosion process and the quantification of new-formed micro-nano plastics. This study provides technical theoretical and methodological supports for studying the fragmentation potential and assessing its environmental risk of biodegradable plastics in soil environment.

Plastic pollution is an emerging global environmental issue and public focal concern. Microplastic materials are derived mainly from the continuous degradation and fragmentation of large plastic materials and pose a risk to the receiving environments, especially to soil. The present study investigated the challenges from microplastic pollution, and recommendations for the processes on controlling microplastic pollution and their management in China are put forward. These include the development of standardized methods for monitoring microplastics in soil; inclusive of microplastics into soil environmental quality standards; improvement in the recovery of agricultural plastic wastes; improvement of the efficacy of waste treatment; and encouraging scientific and technological innovation. Of course, it is a priority to manage the main sources of microplastic pollution to reduce harm to the health of the soil. All of these are expected to provide constructive ideas for the prevention and controlling of microplastic contamination in China.