Heterogeneity of plastic residue was determined by both mulch film and external plastic pollutants in the farmland of Northeast China

Micro/nanoplastics in the Shenyang city atmosphere: Distribution and sources

The contamination of atmospheric particulate matter with diameters ≤2.5 μm (PM2.5) by micro/nanoplastics has increasingly attracted scholarly interest. These micro/nanoplastics can be inhaled into the human respiratory system, potentially leading to respiratory and circulatory diseases. However, current methodologies for quantifying small-sized micro/nanoplastics are inadequate, leading to a limited understanding of their determination and sources. This study aims to conduct both qualitative and quantitative analyses of micro/nanoplastics in PM2.5 in Shenyang City utilizing pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), while also investigating their pollution characteristics and sources. Micro/nanoplastics were detected in all atmospheric PM2.5 samples, with polyethylene (PE) and polyvinyl chloride (PVC) identified as the predominant components. The highest recorded mass concentration of micro/nanoplastics was 28.92 μg/m3, with an average concentration of 7.62 μg/m3, accounting for 12.33% of the total PM2.5 mass. The findings indicate a positive correlation between the concentrations of PM2.5 and micro/nanoplastics, suggesting that PM2.5 may serve as a significant transmission medium. The primary sources of micro/nanoplastics have been identified as domestic, industrial, and agricultural activities. This study represents the first assessment of micro/nanoplastics in Shenyang, highlighting the importance of understanding their characteristics and sources. It provides compelling evidence regarding airborne pathways and the potential health impacts of atmospheric microplastics on human health.

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.

Development and Experiment of an Innovative Row-Controlled Device for Residual Film Collector to Drive Autonomously along the Ridge

The field harvesting process of harvesting machinery is often affected by high workload and environmental factors that can impede/delay manual rowing, thereby leading to lower efficiency and quality in the residual film collector. To address this challenge, an automatic rowing control system using the 4mz-220d self-propelled residual film collector as the experimental carrier was proposed in this study. Cotton stalks in the ridges were chosen as the research object, and a comprehensive application of key technologies, machinery, and electronic control was used, thereby incorporating a pure tracking model as the path-tracking control method. To achieve the automatic rowing function during the field traveling process, the fuzzy control principle was implemented to adjust the forward distance within the pure tracking model dynamically, and the expected steering angle of the steering wheel was determined based on the kinematic model of the recovery machine. The MATLAB/Simulink software was utilized to simulate and analyze the proposed model, thus achieving significant improvements in the automation level of the residual film collector. The field harvesting tests showed that the average deviation of the manual rowing was 0.144 m, while the average deviation of the automatic rowing was 0.066 m. Moreover, the average lateral deviation of the automatic rowing was reduced by 0.078 m with a probability of deviation within 0.1 m of 95.71%. The research study demonstrated that the designed automatic rowing system exhibited high stability and robustness, thereby meeting the requirements of the autonomous rowing operations of residual film collectors. The results of this study can serve as a reference for future research on autonomous navigation technology in agriculture.

Extraction and decontamination of microplastics from high organic matter soils: A simple, cost-saving and high efficient method

This article introduces a simple, cost-saving and high efficient for the extraction and separation of microplastics (MPs) from soil with a high organic matter (SOM) content. In this study, MP with particle sizes of 154-600 μm of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were artificially added into the five Mollisols with the high SOM. Three flotation solutions were used to extract these MPs from soils, and four digestion solutions were used to digest the SOM. As well, their destruction effects on MPs were also examined. The results showed that the flotation recovery rates of PE, PP, PS, PVC and PET were 96.1%-99.0% by ZnCl2 solution, while were 102.0%-107.2% by rapeseed oil, were 100.0%-104.7% by soybean oil. The digestion rate of SOM was 89.3% by H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h, and this was higher than by H2O2 (30%), NaOH and Fenton's reagent. However, the digestion rate of PE, PP, PS, PVC and PET were 0.0%-0.54% by H2SO4:H2O2 (1:40, v:v), and this was lower than by H2O2 (30%), NaOH and Fenton's reagent. As well, the factors influencing on MP extraction was also discussed. Generally, the best flotation solution was ZnCl2 (ρ > 1.6 g cm-3) and the best digestion method was H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h. The optimal extraction and digestion method were verified by the known concentrations of MPs (recovery rate of MPs was 95.7-101.7%), and this method was also used to extract MPs from long-term mulching vegetable fields in Mollisols of Northeast China.

Impact of plastic film mulching on microplastic in farmland soils in Guangdong province, China

Plastic mulch film is often believed to be a significant contributor to microplastic pollution in farmland soil, however, its direct impact in areas with high human activities remains unclear due to the presence of multiple pollution sources. This study aims to address this knowledge gap by investigating the impact of plastic film mulching on microplastic pollution in farmland soils in Guangdong province, China's largest economic province. The macroplastic residues in soils were investigated in 64 agricultural sites, and the microplastics were analyzed in typical plastic film mulched and nearby non-mulched farmland soils. The average concentration of macroplastic residues was 35.7 kg/ha and displayed a positive correlation with mulch film usage intensity. Contrarily, no significant correlation was found between macroplastic residues and microplastics, which exhibited an average abundance of 22,675 particles/kg soil. The pollution load index (PLI) model indicated that the microplastic pollution level was category I and comparatively higher in mulched farmland soils. Interestingly, polyethylene accounted for only 2.7% of the microplastics, while polyurethane was found to be the most abundant microplastic. According to the polymer hazard index (PHI) model, polyethylene posed a lower environmental risk than polyurethane in both mulched and non-mulched soils. These findings suggest that multiple sources other than plastic film mulching primarily contribute to microplastic pollution in farmland soils. This study enhances our understanding of microplastic sources and accumulation in farmland soils, offering crucial information on potential risks to the agroecosystem.

Microplastic migration and distribution in the terrestrial and aquatic environments: A threat to biotic safety

Plastics production has been increasing over years, while their recycling rate is lower, resulting in huge amounts of microplastics (MP) accumulating in the environment. Although the environmental behaviors of MPs have been focused on in recent years, the migration, distribution and adverse effects of MPs in terrestrial and aquatic environments are still not systematically understood. In this review, based on the newest publications from the core database of the Web of Science, both the migration and distribution of MPs were summarized, as well as MPs transfer in biota and their biological effects were also focused on. Generally, the complicated and numerous pathways of MPs migration lead to their distribution throughout or nearly all environments on a global scale. However, the migration mechanisms of MPs with various sizes, shapes, and colors by physicochemical and biological processes, and the prediction models of MP migration and distribution, are deficient, despite these properties being highly related to MPs migration and bio-safety. Although MPs have already invaded microorganisms, plants, animals, and even human beings, the biological effects still need more study, so far as their sizes and shapes and also their composition and adsorption are concerned. Moreover, based on the highlights and deficiencies of current studies, further studies have also been proposed. This review aims to help people re-evaluate the uncertain behaviors of MPs in various environments, and could be helpful to fully understand their biological effects in different environmental conditions.