Effects of Microplastics on the Transport of Soil Dissolved Organic Matter in the Loess Plateau of China

Influence of landfill leachate microenvironment on the occurrence of microplastics: TOC changes are the main driving factor

Factors such as inorganic salts, heavy metals and organics in landfill leachate can affect the environmental behavior and transport properties of microplastics. However, the influence of the microenvironment on the behavioral effects of microplastics in landfill leachate is still limited. In this study, the abundance characteristics of microplastics in leachate from 15 landfills in the North China Plain were investigated. The results showed that the abundance of microplastics in the leachate in this region was 712.0 items/L, which was mainly composed of small particle size and long fibrous microplastics. The relationships between leachate physicochemical factors and microplastic accumulation patterns were explored using models such as structural equations. Among them, TOC (Total Organic Carbon) had the strongest driving effect on 50-100 μm microplastics. And it had different effects on different microplastics: it promoted the degradation of PET (Polyethylene terephthalate), while it inhibited the degradation of PVC (Polyvinyl chloride), FVMQ (Fluorosilicone rubber) and PSU (Polysulfone). The ridge regression model indicated that the interaction of landfill age with Cr (Chromium) and the interaction of redox potential with Cr were the key factors influencing the behavioral characteristics of microplastics in leachate. These results provide a scientific basis for the treating waste leachate and the controlling the emerging pollutants.

Enhanced ecological risk of microplastic ingestion by fish due to fragmentation and deposition in heavily sediment-laden river

The widespread occurrence of microplastics (MPs) in rivers has aroused increasing concerns. However, there remains a significant gap about its effect on fish with different species, especially in highly-sediment-laden rivers. Here, through a large-scale investigation of microplastics in the Yellow River, our research highlighted effects of heavily sediments on MPs contamination in fish gut. MPs were 100 % tested in water, sediment and fish gut samples, with MPs in the lower reach 2∼3 times larger than that of the upper reach. Most of the microplastics were small (<1 mm), fibrous and blue fragments, composed of polyethylene, polypropylene, and polyethylene terephthalate. Feeding habitat and environment significantly controlled MPs ingestion by fish (p < 0.05), of which filter feeders and species with broader dietary preferences exhibited higher ingestion abundance, omnivorous fish abundance up to 24.9 items/individual. Heavily sediment load accelerated the fragmentation and deposition of MPs (p < 0.05), leading to the generation of more and smaller MPs particles, increasing ecological risks to aquatic organisms. Downstream, smaller sediment size and higher organic matter content also facilitated microplastic accumulation. The prevalence of highly toxic polyvinyl chloride polymers was emerged as the major contributor to environmental risks. Our results suggested that the contribution and ecological risks of small microplastics are worth attention in the mid and lower reaches of the Yellow River.

Organic matter and microplastics nexus: A comprehensive understanding of the synergistic impact on soil health

The interactional nexus of microplastics (MPs) and organic matter (OM) can subtly disrupt the delicate balance of soil ecosystems, influencing nutrient dynamics, biodiversity, and overall soil health. To explore this complex interplay between MPs and OM concerning several perspectives, a comprehensive keyword search was conducted across key scientific databases, and the retrieved data was curated according to the PRISMA guidelines to reflect the objectives. Several studies have highlighted that organic-based inputs, such as manures, composts, and sewage sludge, widely used for soil amendment, are potential sources of MPs to soil contamination. These coinciding sources of MPs and OM raise potential concerns about their impact on overall soil health. MPs and OM have parallel characteristics and play a critical role in the soil organic carbon (SOC) and dissolved organic matter (DOM), critical for biogeochemical transformations and nutrient cycling. In light of this, the present review explores the multifaceted nexus between MPs and OM, explaining their interaction mechanisms and their effects on the biological and physicochemical properties of the soil. Despite significant implications on soil ecosystem, challenges remain in accurately quantifying the effects of MPs due to the complexities introduced by DOM. The intricate interaction between MPs and DOM can obscure analytical results, complicating efforts to separate and identify these pollutants effectively. Given these challenges, this review underscores the urgent need for innovative methods to characterize and quantify MPs in complex environmental matrices. Finally, we discuss emerging research directions aimed at advancing the detection and management of MPs in soil ecosystems.

Acetochlor promotes the aging of mulch-derived microplastics in soil by altering the plastisphere microbial community

Although many studies have already highlighted the effects of mulch-derived microplastics (MDMPs) on adsorbing and spreading organic pollutants, the ecological risks of MDMPs co-contaminated with herbicide and the interaction between them have not been clarified. In this study, the interactions between MDMPs from virgin and aged low-density polyethylene (LDPE) films and the herbicide acetochlor in soil were investigated by microcosmic experiments. Results showed that acetochlor in soil was significantly enriched on the surface of MDMPs, with higher concentration on aged-MDMPs compared to virgin-MDMPs. Acetochlor significantly accelerated the fragmentation of aged-MDMPs, leading to more oxygenated functional groups and promoting biofilm development. Acetochlor also notably altered plastisphere microbial community, with Pseudomonas dominating for an extended period in acetochlor-treated samples. This suggests that Pseudomonas may facilitate the aging of MDMPs, likely due to its dual ability to degrade both acetochlor and polyethylene. Additionally, acetochlor initially increased microbial diversity and interaction complexity in the plastisphere, but decreased them in later phase, resulting in a more specialized community. These findings reported here broaden our understanding of interactions between MDMPs and herbicide in soil and offer insights for improved farmland management practices.

Dynamic impact of polyethylene terephthalate nanoplastics on antibiotic resistance and microplastics degradation genes in the rhizosphere of Oryza sativa L

This study examined the effects of polyethylene terephthalate (PET) nanoplastics on the rhizosphere of Oryza sativa L., focusing on dynamic changes and interactions among microbial communities, antibiotic resistance genes (ARGs) and microplastic degradation genes (MDGs). PET exposure altered the structure and function of soil microbial, enabling specific microbial groups to thrive in polluted environments. High-dose PET treatments markedly increased the abundance and dissemination of ARGs, primarily via resistance mechanisms such as antibiotic efflux and target alteration. By providing additional carbon sources and surfaces for microbial attachment, PET stimulated the growth of microorganisms harboring MDGs, resulting in an increase in MDGs abundance. The elevated expression of MDGs facilitated the propagation of ARGs, with overlapping host microorganisms suggesting that certain microbial groups exhibit dual metabolic capabilities, enabling them to endure both antibiotic and microplastic pressures. Toxic byproducts of microplastic degradation, such as mono-ethylhexyl phthalate, further promoted ARGs dissemination by increasing horizontal gene transfer frequency. Structural equation modeling revealed that PET indirectly influenced ARGs and MDGs expression by altering soil C/N ratio, available phosphorus, and enzyme activities. Thus, nanoscale PET exacerbates ecological risks to soil microbial communities by driving co-propagation of ARGs and MDGs, highlighting the persistent threat of composite pollution to agroecosystems.

Microplastic-Induced Alterations in Soil Aggregate-Associated Carbon Stabilization Pathways: Evidence from δ13C Signature Analysis

Microplastics (MPs) are known to affect soil carbon stability in a numerous ways. However, the mechanisms by which they alter the carbon stability within soil aggregates remain unclear . Herein, a one-year field experiment was conducted in an arid agricultural region employing stable isotope techniques to evaluate the soil organic carbon flow in the presence of both persistent (PE, PVC) and biodegradable (PLA, PHA) MPs. PE and PVC reduced the stability of soil aggregates, while PLA and PHA maintained it. Additionally, organic carbon content increased in microaggregates but decreased in small macroaggregates for PE and PVC treatments. By contrast, treatment with PLA and PHA enhanced organic carbon content across aggregates. The δ13C values of PE- and PVC-treated aggregates ranged from -25.34 to -20.85‰, while those of PLA and PHA ranged from -16.29 to -9.26‰. Notably, MPs altered the direction of carbon flow between aggregates, reduced carbon flux, and accelerated carbon emissions. RFP and PLS-PM analyses revealed that persistent MPs affected carbon flow primarily via abiotic factors, whereas biodegradable MPs influenced it via biotic factors. These findings provide insights into the mechanisms by which MPs impact aggregate-associated carbon, highlighting their effects on soil ecosystem services.

Toxicological complexity of microplastics in terrestrial ecosystems

Microplastics (MPs), defined as plastic debris, smaller than <5 mm, are viewed as persistent contaminants that significantly modify terrestrial ecosystems and biodiversity by altering soil microbiota, structure, and functions. This paper summarizes MPs' interactions with various pollutants, including heavy metals and pesticides, also addressing socio-economic impacts, such as reduced agricultural yields and threats to regional fisheries. The study emphasizes the need for an on the basis of waste management model to mitigate these effects, advocating for collaborative efforts among stakeholders. Also, interdisciplinary studies incorporating material sciences, ecology, and environmental policy are essential to confront the challenges of MPs to ecological services. Additionally, the review highlights how MPs can serve as vectors for toxins to damage soil health and species survival. The overview underscores a complex interplay between environmental and socio-economic systems, addressing the urgency of harnessing MPs pollution and protecting ecosystem integrity and sustainability.

Modeling microplastic transport through porous media: Challenges arising from dynamic transport behavior

Modelling microplastic transport through porous media, such as soils and aquifers, is an emerging research topic, where existing hydrogeological models for (reactive) solute and colloid transport have shown limited effectiveness thus far. This perspective article draws upon recent literature to provide a brief overview of key microplastic transport processes, with emphases on less well-understood processes, to propose potential research directions for efficiently modeling microplastic transport through the porous environment. Microplastics are particulate matter with distinct physicochemical properties. Biogeochemical processes and physical interactions with the surrounding environment cause microplastic properties such as material density, geometry, chemical composition, and DLVO interaction parameters to change dynamically, through complex webs of interactions and feedbacks that dynamically affect transport behavior. Furthermore, microplastic material densities, which cluster around that of water, distinguish microplastics from other colloids, with impactful consequences that are often underappreciated. For example, (near-)neutral material densities cause microplastic transport behavior to be highly sensitive to spatio-temporally varying environmental conditions. The dynamic nature of microplastic properties implies that at environmentally relevant large spatio-temporal scales, the complex transport behavior may be effectively intractable to direct physical modeling. Therefore, efficient modeling may require integrating reduced-complexity physics-constrained models, with stochastic or statistical analyses, supported by extensive environmental data.

Effect of microplastics on soil greenhouse gas emissions: A global meta-analysis study

Microplastics (MPs) emerged as a critical global pollutant, yet their effects on soil greenhouse gas (GHG) emissions remain uncertain. This meta-analysis evaluates the effects of MPs exposure on GHG emissions and identifies key influencing factors. Regardless of any influencing factors, MPs exposure decreased N2O emissions by 28.5 %, while increased CO2 and CH4 emissions by 0.07 % and 28.6 %, respectively. However, these changes were statistically insignificant. The factors such as MPs concentration, shape, and type, initial soil type and pH, and the presence of additional additive were identified to significantly influence N2O emission response. The most substantial increase in N2O emissions occurred when MPs exposed to silt soils (+55.8 %), whereas the greatest inhibition was observed in soils with fertilizer addition (-48.8 %). CO2 emission response was significantly influenced by MPs size and shape, initial soil pH and type, experimental duration, and co-additives, with the MPs exposure in sand soils exhibiting the highest increase (+20.7 %) and the exposure of fiber MPs causing the largest reduction (-40.4 %). Additionally, MPs shape and initial soil pH and type were found to significantly affect CH4 emission response. The model selection analysis revealed that the response ratio [ln (RR)] of nirS gene to MPs exposure and MPs concentration were the most critical factors influencing N2O emissions, whereas the size, concentration, and type of MPs, ln (RR) of Chitinase, initial soil pH, additional additive, and experimental duration were the most important influencing factors for CO2 emissions. Overall, this study highlights the high uncertainty associated with the response of GHG emission to MPs exposure due to the complex interplay of abiotic and biotic processes mediated by MPs under varying conditions. In the future, extensive studies across diverse conditions of MPs (e.g., type, shape, and concentration) and soil (e.g., texture and pH) are still urgently needed.

Effects of LDPE and PBAT plastics on soil organic carbon and carbon-enzymes: A mesocosm experiment under field conditions

Although the effects of plastic residues on soil organic carbon (SOC) have been studied, variations in SOC and soil carbon-enzyme activities at different plant growth stages have been largely overlooked. There remains a knowledge gap on how various varieties of plastics affect SOC and carbon-enzyme activity dynamics during the different growing stages of plants. In this study, we conducted a mesocosm experiment under field conditions using low-density polyethylene and poly (butylene adipate-co-terephthalate) debris (LDPE-D and PBAT-D, 500-2000 μm (pieces), 0%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 2%), and low-density polyethylene microplastics (LDPE-M, 500-1000 μm (powder), 0%, 0.05%, 0.1%, 0.5%) to investigate SOC and C-enzyme activities (β-xylosidase, cellobiohydrolase, β-glucosidase) at the sowing, seedling, flowering and harvesting stages of soybean (Glycine Max). The results showed that SOC in the LDPE-D treatments significantly increased from the flowering to harvesting stage, by 12.69%-13.26% (p < 0.05), but significantly decreased in the 0.05% and 0.1% LDPE-M treatments from the sowing to seedling stage (p < 0.05). However, PBAT-D had no significant effect on SOC during the whole growing period. For C-enzyme activities, only LDPE-D treatments inhibited GH (17.22-38.56%), BG (46.7-66.53%) and CBH (13.19-23.16%), compared to treatment without plastic addition, from the flowering stage to harvesting stage. Meanwhile, C-enzyme activities and SOC responded nonmonotonically to plastic abundance and the impacts significantly varied among the growing stages, especially in treatments with PBAT-D (p < 0.05). These risks to soil organic carbon cycling are likely mediated by the effects of plastic contamination and degradation soil microbe. These effects are sensitive to plastic characteristics such as type, size, and shape, which, in turn, affect the biogeochemical and mechanical interactions involving plastic particles. Therefore, further research on the interactions between plastic degradation processes and the soil microbial community may provide better mechanistic understanding the effect of plastic contamination on soil organic carbon cycling.

Planting Enhances Soil Resistance to Microplastics: Evidence from Carbon Emissions and Dissolved Organic Matter Stability

Microplastics (MPs) have become a global hotspot due to their widespread distribution in recent years. MPs frequently interact with dissolved organic matter (DOM) and microbes, thereby influencing the carbon fate of soils. However, the role of plant presence in regulating MPs-mediated changes in the DOM and microbial structure remains unclear. Here, we compared the mechanisms of soil response to 3 common nonbiodegradable MPs in the absence or presence of radish (Raphanus sativus L. var. radculus Pers) plants. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) analysis revealed that MPs reduced the chemodiversity and biodiversity of dissolved organic matter (DOM). MPs enhanced the degradation of lignin-like compounds and reduced the DOM stability. Comparative analysis showed that MPs caused less disturbance to the microbial composition and metabolism in planted soil than in unplanted soil. In unplanted soil, MPs stimulated fermentation while upregulating photoautotrophic activity in planted soil, thereby enhancing system stability. The rhizosphere effect mitigated MPs-induced CO2 emissions. Overall, our study highlights the crucial role of rhizosphere effects in maintaining ecosystem stability under soil microbe-DOM-pollutant interactions, which provides a theoretical basis for predicting the resistance, resilience, and transitions of the ecosystem upon exposure to the anthropogenic carbon source.

The difference between tire wear particles and polyethylene microplastics in stormwater filtration systems: Perspectives from aging process, conventional pollutants removal and microbial communities

Tire wear particles (TWPs) in stormwater runoff have been widely detected and were generally classified into microplastics (MPs). TWPs and conventional MPs can be intercepted and accumulated in stormwater filtration systems, but their impacts on filtration, adsorption and microbial degradation processes of conventional pollutants (organic matters, nitrate and ammonium) have not been clarified. TWPs are different from MPs in surface feature, chemical components, adsorption ability and leaching of additives, which might lead to their different impacts on conventional pollutants removal. In this study, five different levels of aged polyethylene MPs (PEMPs) and aged TWPs contamination in stormwater filtration systems were simulated using thirty-three filtration columns. Results showed that ultraviolet aging treatment was less influential for the aging of TWPs than that of PEMPs, the specific surface area of aged PEMPs (1.603 m2/g) was over two times of unaged TWPs (0.728 m2/g) in the same size. Aged PEMPs and aged TWPs had different impacts on conventional pollutants removal performance and microbial communities, and the difference might be enlarged with exposure duration. The intensified aged PEMPs contamination generally promoted conventional pollutants removal, whereas aged TWPs showed an opposite trend. Mild contamination (0.01% and 0.1%, wt%) of aged PEMP/TWPs was beneficial to the richness and diversity of microbial communities, whereas higher contamination of aged PEMPs/TWPs was harmful. Aged PEMPs and TWPs had different impact on microbial community structure. Overall, the study found that TWPs were more detrimental than PEMPs in filtration systems. The research underscores the need for more comprehensive investigation into the occurrence, effects and management strategies of TWPs, as well as the importance of distinguishing between TWPs and MPs in future studies.

Microplastics from polyvinyl chloride agricultural plastic films do not change nitrogenous gas emission but enhance denitrification potential

The effects of microplastics (MPs) from agricultural plastic films on soil nitrogen transformation, especially denitrification, are still obscure. Here, using a robotized flow-through system, we incubated vegetable upland soil cores for 66 days with MPs from PE mulching film (F-PE) and PVC greenhouse film (F-PVC) and directly quantified the emissions of nitrogenous gases from denitrification under oxic conditions, as well as the denitrification potential under anoxic conditions. The impact of MPs on soil nitrogen transformation was largely determined by the concentration of the additive phthalate esters (PAEs) containing in the MPs. The F-PE MPs with low level of PAEs (about 0.006 %) had no significant effect on soil mineral nitrogen content and nitrogenous gas emissions under oxic conditions. In contrast, the F-PVC MPs with high levels of PAEs (about 11 %) reduced soil nitrate content under oxic conditions, probably owing to promoted microbial assimilation of nitrogen, as the emissions of denitrification products (N2, NO, and N2O) was not affected. However, the F-PVC MPs significantly enhanced the denitrification potential of the soil due to the increased abundance of denitrifiers under anoxic conditions. These findings highlight the disturbance of MPs from agricultural films, particularly the additive PAEs on nitrogen transformation in soil ecosystems.

Enhancing soil gross nitrogen transformation through regulation of microbial nitrogen-cycling genes by biodegradable microplastics

Microplastics (MPs) in agricultural plastic film mulching system changes microbial functions and nutrient dynamics in soils. However, how biodegradable MPs impact the soil gross nitrogen (N) transformations and crop N uptake remain significantly unknown. In this study, we conducted a paired labeling 15N tracer experiment and microbial N-cycling gene analysis to investigate the dynamics and mechanisms of soil gross N transformation processes in soils amended with conventional (polyethylene, PE) and biodegradable (polybutylene adipate co-terephthalate, PBAT) MPs at concentrations of 0 %, 0.5 %, and 2 % (w/w). The biodegradable MPs-amended soils showed higher gross N mineralization rates (0.5-16 times) and plant N uptake rates (16-32 %) than soils without MPs (CK) and with conventional MPs. The MPs (both PE and PBAT) with high concentration (2 %) increased gross N mineralization rates compared to low concentration (0.5 %). Compare to CK, MPs decreased the soil gross nitrification rates, except for PBAT with 2 % concentration; while PE with 0.5 % concentration and PBAT with 2 % concentration increased but PBAT with 0.5 % concentration decreased the gross N immobilization rates significantly. The results indicated that there were both a concentration effect and a material effect of MPs on soil gross N transformations. Biodegradable MPs increased N-cycling gene abundance by 60-103 %; while there was no difference in the abundance of total N-cycling genes between soils without MPs and with conventional MPs. In summary, biodegradable MPs increased N cycling gene abundance by providing enriched nutrient substrates and enhancing microbial biomass, thereby promoting gross N transformation processes and maize N uptake in short-term. These findings provide insights into the potential consequences associated with the exposure of biodegradable MPs, particularly their impact on soil N cycling processes.

Molecular Weights of Dissolved Organic Matter Significantly Affect Photoaging of Microplastics

The fate of ubiquitous microplastics (MPs) is largely influenced by dissolved organic matter (DOM) in aquatic environments, which has garnered significant attention. The reactivity of DOM is reported to be greatly regulated by molecular weights (MWs), yet little is known about the effects of different MW DOM on MP aging. Here, the aging behavior of polystyrene MPs (PSMPs) in the presence of different MW fulvic acids (FAs) and humic acids (HAs) was systematically investigated. Under ultraviolet (UV) illumination, O/C of PSMPs aged for 96 h surged from 0.008 to 0.146 in the lower MW FA (FA<1kDa) treatment, suggesting significant PSMP aging. However, FA exhibited a stronger effect on facilitating PSMP photoaging than HA, which can be attributed to the fact that FA<1kDa contains more quinone and phenolic moieties, demonstrating a higher redox capacity. Meanwhile, compared to other fractions, FA<1kDa was more actively involved in the increase of different reactive species yields by 50-290%, including •OH, which plays a key role in PSMP photoaging, and contributed to a 25% increase in electron-donating capacity (EDC). This study lays a theoretical foundation for a better understanding of the environmental fate of MPs.

Microplastics and Co-pollutants in soil and marine environments: Sorption and desorption dynamics in unveiling invisible danger and key to ecotoxicological risk assessment

Microplastics (MPs) and their co-pollutants pose significant threats to soil and marine environments, necessitating understanding of their colonization processes to combat the plastic pandemic and protect ecosystems. MPs can act as invisible carriers, concentrating and transporting pollutants, leading to a more widespread and potentially toxic impact than the presence of either MPs or the pollutants alone. Analyzing the sorption and desorption dynamics of MPs is crucial for understanding pollutants amplification and predicting the fate and transport of pollutants in soil and marine environments. This review provides an in-depth analysis of the sorption and desorption dynamics of MPs, highlighting the importance of considering these dynamics in ecotoxicological risk assessment of MPs pollution. The review identifies limitations of current frameworks that neglect these interactions and proposes incorporating sorption and desorption data into robust frameworks to improve the ability to predict ecological risks posed by MPs and co-pollutants in soil and marine environments. However, failure to address the interplay between sorption and desorption can result in underestimation of the true impact of MPs and co-pollutants, affecting livelihoods and agro-employments, and exacerbate poverty and community disputes (SDGs 1, 2, 3, 8, 9, and 16). It can also affect food production and security (SDG 2), life below water and life on land (DSGs 14 and 15), cultural practices, and natural heritage (SDG 11.4). Hence, it is necessary to develop new approaches to ecotoxicological risk assessment that consider sorption and desorption processes in the interactions between the components in the framework to address the identified limitations.

Effects of combined microplastics and heavy metals pollution on terrestrial plants and rhizosphere environment: A review

Microplastics (MPs) can enter the soil environment through industry, agricultural production and daily life sources. Their interaction with heavy metals (HMs) poses a significant threat to a variety of terrestrial ecosystems, including agricultural ones, thereby affecting crop quality and threatening human health. This review initially addresses the impact of single and combined contamination with MPs and HMs on soil environment, including changes in soil physicochemical properties, microbial community structure and diversity, fertility, enzyme activity and resistance genes, as well as alterations in heavy metal speciation. The article further explores the effects of this pollution on the growth characteristics of terrestrial plants, such as plant biomass, antioxidant systems, metabolites and photosynthesis. In general, the combined contaminants tend to significantly affect soil environment and terrestrial plant growth, i.e., the impact of combined contaminants on plants weight ranged from -87.5% to 4.55%. Similarities and differences in contamination impact levels stem from the variations in contaminant types, sizes and doses of contaminants and the specific plant growth environments. In addition, MPs can not only infiltrate plants directly, but also significantly affect the accumulation of HMs in terrestrial plants. The heavy metals concentration in plants under the treatment of MPs were 70.26%-36.80%. The co-occurrence of these two pollution types can pose a serious threat to crop productivity and safety. Finally, this study proposes suggestions for future research aiming to address current gaps in knowledge, raises awareness about the impact of combined MPs + HMs pollution on plant growth and eco-environmental security.

Soil chemical fumigation alters soil phosphorus cycling: effects and potential mechanisms

Soil chemical fumigation is an effective and popular method to increase agricultural productivity. However, the broad-spectrum bioactivity of fumigants causes harm to soil beneficial microorganisms involved in the soil phosphorous cycle, such as soil phosphorus solubilizing microorganisms (PSMs). We review the effects of soil chemical fumigation on soil phosphorus cycling, and the potential underlying mechanisms that ultimately lead to altered phosphorus availability for crops. These complex processes involve the highly diverse PSM community and a plethora of soil phosphorus forms. We discuss phosphatizing amendments aimed at counteracting the possible negative effects of fumigation on phosphorus availability, phosphorus use efficiency, and crop yields. We also emphasize distinguishing between the effects on soil phosphorus cycling caused by the chemical fumigants, and those caused by the fumigation process (e.g. plastic mulching). These are typically conflated in the literature; distinguishing them is critical for identifying appropriate amendments to remediate possible post-fumigation soil phosphorus deficiencies.

Parameters optimization for decontamination and fine physical regeneration pathways of polypropylene plastics from waste lunchboxes

Due to the development of the food delivery industry, a large amount of waste lunchboxes made of homo polypropylene (PP) plastic have been generated. This study developed a new technological strategy to effectively regenerate PP from waste lunchboxes. Through response surface curve analysis, it was found that under the optimal process conditions of hot alkali washing at 80 ℃, 30 min, and pH 13, the optimal contact angle was 65.55°, indicating a good oil stain removal effect. By identifying and analyzing the characteristics of impurities in waste lunchboxes, a physical sorting and granulation regeneration process was constructed. And through large-scale statistical analysis and data collection, it was further verified that recycled PP plastics maintained their physical stability and excellent processing performance. The quality stability of recycled PP plastics in terms of impurities content was also verified. By designing different formulations specifically, recycled PP was mixed with different virgin PP and antioxidants in appropriate proportions, and extruded into particles under 150-300 mesh filtration conditions to obtain modified recycled PP. Modified recycled PP was applied in textiles, clothing, and injection molded products. In conclusion, we achieve the up-cylcing of waste PP lunchboxes instead of down-cylcing.