Organic fertilizer and irrigation water are the primary sources of microplastics in the facility soil, Beijing

Microplastics in rice-based farming systems and their connection to plastic waste management in the Chicoral district of Espinal-Tolima

The presence of microplastics (MPs) in agricultural soils is a growing concern, especially in rice cultivation systems, where information is limited, particularly in Latin America. Given the economic importance of this crop in Colombia and the generation of plastic waste from some associated practices, it is crucial to determine the presence of MPs related to agricultural activities in soils dedicated to this activity. This study evaluated the presence of MPs in soils and irrigation water of rice crops in Chicoral, Tolima, Colombia, during two contrasting seasons. Soil samples from seven plots (upper, middle, and lower zones) and water samples from seven points along the irrigation canal were collected. MPs were found in all samples, with similar concentrations in water samples collected in the rainy and dry seasons (0.11 ± 0.10 vs. 0.10 ± 0.06 items/m3, respectively), and higher abundance in soil samples during the rainy season (4 ± 2.71 vs 3.62 ± 1.92 items/50 g). Fragments and fibers were the most abundant forms of plastics (53 % water, 55 % soil), predominantly larger than 100 μm and blue in color. Polypropylene (PP) was the most abundant polymer (50 %) in the meso- and macroplastic samples. Our results suggested that MPs contamination in rice crop soils at Chicoral is influenced by irrigation water transport and improper plastic waste management, highlighting the need for further research on their effects on agricultural systems.

Tracking the source of microplastics in soil-an exploratory case study in peach orchards from east-central Portugal

In the last 20 years, world plastic production has increased rapidly, reaching 4.00 × 1011 kg in 2022. However, less than 10% was recycled. Moreover, most conventional plastics are persistent and, therefore, remain in the environment long after their release. Although most studies on microplastic contamination focus on a single environmental compartment, an integrated and multicompartment approach is highly recommended considering the multitude of interactions between those compartments. This study addresses this knowledge gap, investigating the presence and potential sources of microplastics (MP) in agricultural soils under typical conditions of the Mediterranean region, characterised by dry summers and relatively moist and mild winters (Csa according to the Köppen-Geiger classification). For this, 19 orchards from east-central Portugal were used as case study sites, and a total of 111 samples were analysed. Soil content in MP was assessed in 3 soil layers (0-5, 5-15 and 15-25 cm). To quantify potential sources to soil, information from farmers was used, and samples from irrigation water, atmospheric deposition and manure were analysed. Optical assessment with the assistance of a stereomicroscope was used for MP quantification. The 0-5 cm soil layer showed a lower content (average of 2.2 particles·g-1) and higher particle sizes (average of 168 µm) than deeper soil layers. The identified sources contributed with 1.02 × 105 particles·m-2·year-1. Irrigation water was the main source, representing 55.9% of the aforementioned input rate encountered for the 3 identified MP sources. Additional knowledge is needed regarding the possible variation in MP content throughout the year and between years and the polymer identification, not only in samples collected from soil but also from its main contamination sources. Furthermore, this study should be extended to other crops and regions as part of broader soil health monitoring.

Driving factors and sources of microplastics in soils in the Yellow River source area

Microplastics (MPs) are widespread in various environments worldwide, they pose a serious threat to ecosystems. As a typical remote area, the Qinghai-Tibetan Plateau (QTP) has a sophisticated road system. However, the contributions of anthropogenic and natural factors to MP accumulation in remote plateau regions remain unclear. Here, we investigated the distribution, driving factors, and main sources of MPs in the source area of Yellow River on the QTP. MPs in soil showed an average abundance of (75.39 ± 49.16) items/kg, which was approximately 1-103 lower than that in the lower sections of Yellow River. Film, transparent color, and polyethylene were the common shapes, colors, and polymers, respectively. Under different land uses, MP abundance was remarkably higher in nonagricultural soils than in farmland. The influencing factors, source analysis on the basis of MP characteristics, and statistical analysis (redundancy analysis and structural equation modeling) showed that MP abundance was influenced by nonagricultural activities (tourism, traffic, and grazing). Utilizing the conditional fragmentation model, we further revealed that MP abundance in the upstream and downstream regions was related to roadside dust (traffic) and atmospheric dust. It was associated with human activities, including plastic packaging waste from tourism and herdsmen, in the midstream region. Moreover, MPs in farmland were related to local sources (fertilizers). These results provide valuable information on MP distribution in headstream areas and thus contribute to controlling potential MP pollution on the QTP.

Macro- and micro-plastic accumulation in soils under different intensive farming systems: A case study in Quzhou county, the North China Plain

The macroplastics (MaPs) and microplastics (MiPs) polluting agricultural soils raise great concerns. Unfortunately, scientists know little about the occurrence of MaPs/MiPs in soil among different farming systems. In this study, we analyzed MaPs/MiPs in soils (0-30 cm) collected from six different farming systems (wheat-maize rotations, cotton, vegetables, permanent orchards, greenhouses with and without mulching) in Quzhou county, the North China Plain, by using fluorescence microscope and micro-Fourier transform infrared spectroscopy. The results showed that the abundance of MaPs and MiPs ranged from 0.2 to 46.8 kg ha-1, and 4.1 × 103-3.7 × 104 items kg-1, respectively. The prominent colors of the MaPs were white and black. The predominant shape, size and chemical composition of soil MiPs were fragments (45-62%), <1 mm (98-99%), and polyethylene (38-43%), respectively. MaPs were mainly detected in the 0-10 cm soil layer. MiP abundance in the 0-10 cm soil layer was significantly higher than that in the 20-30 cm soil layers among different farming systems, except for the fields with wheat-maize rotations and permanent orchards (p < 0.05). Overall, cotton fields showed the highest MaP and MiP abundance, followed by vegetable fields and orchards. Redundancy analysis revealed that tillage practices and plastic film management greatly influence the size distribution of MiPs. A strong negative correlation between large-sized plastic fractions (0.2-1 mm) and tillage frequency was tested while the years of application of plastic films and the abundance of plastic residues showed a strong positive correlation with small-sized plastic fractions (<0.2 mm). Our findings conclude that agricultural mulch films are an important source of MaPs and MiPs in agricultural soil and distributions are strongly influenced by agricultural management practices and farming systems. Further studies should take farming systems and farming practices into account, thereby exploring the potential mechanisms of plastic fragmentation and granularization in agricultural soil.

Effects of polyethylene and poly (butyleneadipate-co-terephthalate) contamination on soil respiration and carbon sequestration

To address plastic pollution in agricultural soils due to polyethylene plastic film mulch used, biodegradable film is being studied as a promising alternative material for sustainable agriculture. However, the impact of biodegradable and polyethylene microplastics on soil carbon remains unclear. The field experiment was conducted with Poly (butyleneadipate-co-terephthalate) debris (PBAT-D, 0.5-2 cm), low-density polyethylene debris (LDPE-D, 0.5-2 cm) and microplastic (LDPE-Mi, 500-1000 μm) contaminated soil (0% (control), 0.05%, 0.1%, 0.2%, 0.5%, 1% and 2% w:w) planted with soybean, to explore potential impacts on soil respiration (Rs), soil organic carbon (SOC) and carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidizable carbon (EOC), particulate organic carbon (POC), mineral-associated organic carbon (MAOC)), and C-enzymes (β-glucosidase, β-xylosidase, cellobiohydrolase). Results showed that PBAT-D, LDPE-D and LDPE-Mi significantly inhibited Rs compared with the control during the flowering and harvesting stages (p < 0.05). SOC significantly increased in the PBAT-D treatments at both stages, and in the LDPE-Mi treatments at the harvesting stage, but decreased in the LDPE-D treatments at the flowering stage. In the PBAT-D treatments, POC increased but DOC and MAOC decreased at both stages. In the LDPE-D treatments, MBC, DOC and EOC significantly decreased but POC increased at both stages. In the LDPE-Mi treatments, MBC and DOC significantly decreased at the harvesting stage, while EOC and MAOC decreased but POC increased at the flowering stage. For C-enzymes, no significant inhibition was observed at the flowering stage, but they were significantly inhibited in all treatments at the harvesting stage. It is concluded that PBAT-D facilitates soil carbon sequestration, which may potentially alter the soil carbon pool and carbon emissions. The key significance of this study is to explore the overall effects of different forms of plastic pollution on soil carbon dynamics, and to inform future efforts to control plastic pollution in farmlands.

Global soil microplastic assessment in different land-use systems is largely determined by the method of analysis: A meta-analysis

Although microplastics (1 μm - 5 mm, MP) are increasingly recognised as a novel entity of pollutants, we still lack a basic understanding of their prevalence in different terrestrial environments. Here, we aimed at performing comparisons of MP concentrations (items kg-1) in different agro-ecosystems, with specific focus on input pathways and land uses, while accounting for the plethora of method variations available, such as analysed MP sizes, sampling depths, density separation solutions, as well as removal of organic matter. We found that the current global means of MP loads, from 89 studies (553 sites), benchmarks 2900 ± 7600 MP items kg-1 soil, substantially more than the global median of 480 MP items kg-1. Roughly 81 % of the studies were conducted in Asia; hence, continent-wide comparisons are still hampered by low study numbers for most regions. Maximum MP numbers were found for soils under both greenhouses and plastic mulching (5200 ± 8300 items kg-1), followed by arable soils with sludge amendments (3700 ± 8800 items kg-1), surprisingly without evidence of elevated MP loads in horticultural fields relative to other agricultural management practices. Intriguingly, global MP loads significantly increased with decreasing levels of urbanisation, i.e., they were highest in rural areas. Yet, quantitative comparisons among sites are biased by the methodology selected for MP analyses. Apart from inconsistencies in sampling depth and size of screened MP particles, across all sites and treatments, largest MP loads were commonly found when using high-density solutions rather than low-density ones, and when soil organic matter removal was performed after, and not before, the density separation step.

Nanoplastics indirectly compromise lettuce growth in hydroponic systems via microbial extracellular vesicles derived from Curvibacter fontanus

Recent studies confirm that nanoplastics (NP) cause severe microbial imbalances in various ecosystems, significantly affecting microbial diversity and abundance. Hydroponic systems vital for lettuce production are increasingly threatened by NP contamination in irrigation water and this issue is gaining global attention. This study investigates microbial species in hydroponic irrigation water altered by NP exposure and their impact on lettuce growth. While NP (108-1010 particles/L) did not directly harm or accumulate in lettuce, significant changes in water parameters and microbial communities were observed, particularly an increase in Curvibacter fontanus abundance. Inoculation of sterile irrigation water with NP and C. fontanus led to lettuce mortality, suggesting C. fontanus as a critical mediator. Furthermore, extracellular vesicles (EVs) isolated from C. fontanus, treated with NP, were shown to suppress leaf development, growth, antioxidant defenses, and lettuce survival. This study concludes that NP-induced microbial shifts, particularly involving C. fontanus EVs, indirectly harm hydroponic lettuce production.

Distribution, characteristics, and ecological risks of microplastics in the Hongyingzi sorghum production base in China

Microplastics (MPs), an emerging pollutant of global concern, have been studied in the Hongyingzi sorghum production base. In this study, we investigated MPs in the surface soil (0-10 cm) and deeper soil (10-20 cm) in the Hongyingzi sorghum production base. Pollution characterization and ecological risk evaluation were conducted. The results revealed that the MP abundance ranged from 1.31 × 102 to 4.27 × 103 particles/kg, with an average of 1.42 ± 1.22 × 103 particles/kg. There was no clear correlation between the MP abundance and soil depth, and the ordinary kriging method predicted a range of 1.26 × 103-1.28 × 103 particles/kg in most of the study area, indicating a relatively uniform distribution. Among the 12 types of MPs detected, acrylates copolymer (ACR), polypropylene (PP), polyurethane (PU), and polymethyl methacrylate (PMMA) were the most frequently detected. These MPs primarily originated from packaging and advertising materials made from polyurethane and polyester used by Sauce Wine enterprises, as well as plastic products made from polyolefin used in daily life and agricultural activities. The particle size of MPs was primarily 20-100 μm. Overall, the proportion of the 20-100 μm MP was 95.1% in the surface soil layer and 86.7% in the deeper soil layer. Based on the pollution load index, the MP pollution level in the study area was classified as class I. Polymer hazard index evaluation revealed that the risk levels at all of the sampling sites ranged from IV to V, and ACR, PU, and PMMA were identified as significant sources of polymer hazard. Potential ecological index evaluation revealed that most of the soil samples collected from the study area were dangerous or extremely dangerous, and the surface soil posed a greater ecological risk than the deeper soil. These findings provide a scientific foundation for the prevention, control, and management of MP pollution in the Hongyingzi sorghum production base.

Wastewater-associated plastispheres: A hidden habitat for microbial pathogens?

Wastewater treatment plants (WWTPs) receive wastewater from various sources. Despite wastewater treatment aiming to remove contaminants, microplastics persist. Plastic surfaces are quickly colonized by microbial biofilm ("plastispheres"). Plastisphere communities are suggested to promote the spread and survival of potential human pathogens, suggesting that the transfer of plastispheres from wastewater to the environment could pose a risk to human and environmental health. The study aimed to identify pathogens in wastewater plastispheres, specifically food-borne pathogens, in addition to characterizing the taxonomic diversity and composition of the wastewater plastispheres. Plastispheres that accumulated on polypropylene (PP), polyvinyl chloride (PVC), and high-density polyethylene propylene (HDPE) surfaces exposed to raw and treated wastewater were analyzed via cultivation methods, quantitative reverse transcription PCR (RT‒qPCR) and 16S rRNA amplicon sequencing. RT‒qPCR revealed the presence of potential foodborne pathogenic bacteria and viruses, such as Listeria monocytogenes, Escherichia coli, norovirus, and adenovirus. Viable isolates of the emerging pathogenic species Klebsiella pneumoniae and Acinetobacter spp. were identified in the plastispheres from raw and treated wastewater, indicating that potential pathogenic bacteria might survive in the plastispheres during the wastewater treatment. These findings underscore the potential of plastispheres to harbor and disseminate pathogenic species, posing challenges to water reuse initiatives. The taxonomic diversity and composition of the plastispheres, as explored through 16S rRNA amplicon sequencing, were significantly influenced by the wastewater environment and the duration of time the plastic spent in the wastewater. In contrast, the specific plastic material did not influence the bacterial composition, while the bacterial diversity was affected. Without efficient wastewater treatment and proper plastic waste management, wastewater could act as a source of transferring plastic-associated pathogens into the food chain and possibly pose a threat to human health. Continued research and innovation are essential to improve the removal of microplastics and associated pathogenic microorganisms in wastewater.

The addition of humic acid into soil contaminated with microplastics enhanced the growth of black gram (Vigna mungo L. Hepper) and modified the rhizosphere microbial community

Microplastics have polluted agricultural soils, posing a substantial risk to crop productivity. Moreover, the presence of microplastic pollution has caused a disturbance in the composition of the microbial community in the soil surrounding plant roots, therefore impacting the growth of beneficial bacteria. A study was conducted to examine if humic acid (HA) can counteract the harmful effects of microplastics (MPs) on the growth of black gram crops and the composition of the rhizosphere soil microbial community, to reduce the negative impacts of microplastics on these microorganisms and crops. The research was carried out using mud pots and the plastic utilized for the experiment consisted of 60% high-density polyethylene (HDPE) and 40% polypropylene (PP). The soil was enriched with lignite-based potassium humate, which had a pH range of 8.0-9.5 and with 65% humic acid. The experiment consisted of six treatments: T1, which served as the control without HA and MP; T2, which involved the use of HA at a concentration of 0.15% w/w; T3, which involved the use of MP at a concentration of 0.2% w/w; T4, which involved the use of MP at a concentration of 0.4% w/w; T5, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.2% w/w; and T6, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.4% w/w. The plant growth characteristics, including germination percentage, nodule number, and chlorophyll content, were measured. In addition, the DNA obtained from the rhizosphere soil was analyzed using metagenomics techniques to investigate the organization of the microbial population. Seedlings in soil polluted with MP exhibited delayed germination compared to seedlings in uncontaminated soil. Following 60 days of growth, the soil samples treated with T5 (0.2% MP and 0.15% HA w/w) had the highest population of bacteria and rhizobium, with counts 5.58 ± 0.02 and 4.90 ± 0.02 CFU g-1 soil. The plants cultivated in T5 had the most elevated chlorophyll-a concentration (1.340 ± 0.06 mg g-1), and chlorophyll-b concentration (0.62 ± 0.02 mg g-1) while those cultivated in T3 displayed the lowest concentration of chlorophyll-a (0.59 ± 0.02 mg g-1) and chlorophyll-b (0.21 ± 0.04 mg g-1). Within the phylum, Proteobacteria had the highest prevalence in all treatments. However, when the soil was polluted with MPs, its relative abundance was reduced by 8.4% compared to the control treatment (T1). Conversely, treatment T5 had a 3.76% rise in relative abundance when compared to treatment T3. The predominant taxa found in soil polluted with MP were Sphingomonas and Bacillus, accounting for 19.3% of the total. Sphingomonas was the predominant genus (21.2%) in soil polluted with MP and supplemented with humic acid. Humic acid can be used as a soil amendment to mitigate the negative effects of MPs and enhance their positive advantages. Research has demonstrated that incorporating humic acid into soil is a viable method for maintaining the long-term integrity of soil's physical, chemical, and biological characteristics.

Using machine learning to reveal drivers of soil microplastics and assess their stock: A national-scale study

The issue of microplastic (MP) contamination in soil is a significant concern. However, due to limited large-scale studies and stock assessments, our understanding of the drivers of their distribution and fate remains incomplete. To address this, we conducted a comprehensive study in China, collected MP data from 621 sites, and utilized machine learning techniques for analysis. Our findings revealed 9 key factors influencing the distribution of soil MPs, highlighting their nonlinear influence processes. Among these factors, atmospheric deposition emerged as the most dominant driver, while wind and precipitation could lead to the transformation of soil from a sink to a source of MPs. MP concentrations in Chinese soils vary from 1.4 to 4333.1 particles/kg, with human activities significantly affecting their distribution, resulting in higher concentrations in the east and lower concentrations in the west. The estimated MP stock in Chinese soils is 1.92 × 1018 particles, equivalent to a mass of 2.11-8.64 million tonnes. This stock alone surpasses that found in global oceans, making global soil the largest reservoir of MPs. Overall, this study enhances our understanding of the environmental behavior of MPs and provides valuable data and theoretical support for the prevention, control, and management of this contamination.

Contamination of consumer composts by metals, microplastics and other microscopic debris

Very little information exists on the particle and chemical contamination of consumer (horticultural) composts. In this study, anthropogenic microcellulosics (AMCs), microplastics (MPs) and other microscopic debris, along with anthropogenically impacted metals (Cu, Zn, Pb), have been determined in 12 composts (seven garden composts and five growbags) purchased at outlets in the UK. AMCs and MPs, determined microscopically, were present in all samples at up to about 1100 kg-1 dw. AMCs were more abundant and were dominated by fibres constructed of rayon and cotton, while petroleum-based MPs exhibited a greater diversity in shape and polymeric construction (including polyolefins, polyethylene terephthalate, polyvinyl chloride, resins, paints and rubbers). Other microdebris, present in much smaller concentrations in the composts, consisted of fragments of glass, metal and machined wood and spherical glass beads. Concentrations of the anthropogenically impacted metals, Cu, Pb and Zn, determined directly by energy-dispersive X-ray fluorescence spectrometry, were heterogeneously distributed and averaged 52.4, 192 and 51.6 mg kg-1 dw, respectively. Although concentrations of anthropogenic particles were not related to cost or type of compost, physico-chemical properties or metal concentrations, a significant relationship between Pb content and particle diversity (number of polymers and debris types) was established. This relationship might result from the general contamination of the environment by both Pb and anthropogenic particulates, or the association of the metal with various types of material (e.g. paints, polyvinyl chloride, glass). Despite the ubiquity and diversity of MPs and microdebris in consumer composts, an understanding of their impacts on plant growth, either directly or indirectly (e.g. by interacting with metals), is unknown.

Screening of optimal cleaning methods to reduce microplastic residues on strawberry surfaces: Characterization of microplastics in strawberry wash water

Microplastics are widespread in facility strawberry greenhouses and can be deposited on the surface of strawberries through air currents. Investigating effective cleaning methods represents a viable strategy to reduce human ingestion of MPs. Therefore, different cleaning methods were compared: ultrasonic cleaning for 30 min, deionized water rinsing once, deionized water immersion for 30 min, and fruit immersion in washing salt for 30 min. The MPs in strawberry washing water were analyzed and compared using laser direct infrared imaging to investigate their characteristics and the optimal reduction of MPs on the surface of strawberries. The quality of the cleaning results was in the following order: water immersion > washing salt immersion > water rinsing > ultrasound. Water immersion was 1.3-2 times more effective in removing microplastics than other treatments. Furthermore, 21 polymer types were detected in the samples. Most MPs were less than 50 µm in size. The main polymers in this size range were polyamide, chlorinated polyethylene, and polyethylene terephthalate, and they mainly existed as fragments, fibers, and beads. This study provides a valuable reference for reducing human intake of microplastics through fresh fruits and vegetables.

Microplastics occurrence and distribution characteristics in mulched agricultural soils of Guizhou province

Microplastics pollution in agricultural soil is increasingly recognized, but the specific situation varies with geography, climate conditions, and farming practices. The karst landscape, a typical geomorphology in China, demands a deeper understanding of microplastics pollution in such areas. This research zeroes in on Guizhou, a province known for its karst formations, by collecting soil samples from the mulched cultivation layer in ten counties and cities. The study employed metallographic microscopy, scanning electron microscopy (SEM-EDS), and Fourier-transform infrared spectroscopy (FT-IR) to analyze the presence and distribution of microplastics. Results show that polyethylene is the predominant component of microplastics in the mulched agricultural soils of Guizhou, primarily existing as irregular fragments in black, transparent, and translucent forms, with diameters of 40 ~ 120 μm and rough surfaces marked by significant erosion. The concentration of microplastics varies from 143.28 to 3,283.46 items/kg, averaging 1,150.60 ± 647.86 items/kg. The majority of particles accounting for 64.79% are sized between 10 ~ 100 μm. A highly significant positive correlation (p < 0.001) is found between mulching duration and microplastics concentration, indicating that prolonged mulching increases microplastics accumulation in farmlands. Additionally, crop type, irrigation method, and soil type also influence microplastics concentration. This study highlights the escalating issue of microplastics pollution in China's karst regions, underscoring the need for attention.

Unraveling the characteristics of microplastics in agricultural soils upon long-term organic fertilizer application: A comprehensive study using diversity indices

Microplastics negatively impact soil health and productivity. Organic fertilizers constitute significant contributors of microplastics in agricultural soils. Nevertheless, comprehensive data on the diversity of microplastics in long-term fertilized soils remain unavailable. In this study, we assessed the presence of microplastics in soils subjected to application of three different organic fertilizers (pig manure, chicken manure, and sludge composts) over 12 years, and evaluated the potential ecological risks posed by microplastic accumulation. The average microplastic abundance in soil was 368.88 ± 207.97 (range: 90-910) items/kg. Microplastic abundance differed among fertilization treatments, with substantial increases of 16.67%, 71.67%, and 61.43% upon low to high application of the three treatments, respectively. Overall, the microplastics predominantly comprised fibers (70.94%) and fragments (25.25%), of which a substantial proportion constituted light-colored microplastics (transparent and white). The size of microplastics was mainly concentrated in the 1-2 mm range (39.96%), with rayon, polypropylene, polyester, and polyethylene being identified as the major types. The risk assessment indices of the three treatments were 229.38, 257.64, and 175.89, respectively, and were all classified as level 4 (high risk). The microplastic diversity integrated index and principal component analysis revealed that microplastics were uniformly distributed throughout the 0-20 cm soil depth consequent to tillage activity. Together, these findings provide a comprehensive assessment of microplastic pollution in long-term fertilized soils and serve as a scientific basis for reducing microplastic contamination in agricultural soils.

Distribution patterns and environmental risk assessments of microplastics in the lake waters and sediments from eight typical wetland parks in Changsha city, China

The quality of water in urban parks is closely related to people's daily lives, but the pollution caused by microplastics in park water and sediments has not been comprehensively studied. Therefore, eight typical parks in the urban area of Changsha, China, were selected, and Raman spectroscopy was used to explore the spatial distributions and compositions of the microplastics in the water and sediments, analyze their influencing factors, and evaluate their environmental risks. The results showed that the abundances of surface water microplastics in all parks ranged from 150 to 525 n L-1, and the abundances of sediment microplastics ranged from 120 to 585 n kg-1. The microplastics in the surface water included polyethylene terephthalate (PET), chlorinated polyethylene (CPE), and fluororubber (FLU), while those in the sediments included polyvinyl chloride (PVC), wp-acrylate copolymer (ACR), and CPE. Regression analyses revealed significant positive correlations between human activities and the abundances of microplastics in the parks. Among them, the correlations of population, industrial discharge and domestic wastewater discharge with the abundance of microplastics in park water were the strongest. However, the correlations of car flow and tourists with the abundance of microplastics in park water were the weakest. Based on the potential ecological risk indices (PERI) classification assessment method, the levels of microplastics in the waters and sediments of the eight parks were all within the II-level risk zone (53-8,549), among which the risk indices for Meixi Lake and Yudai Lake were within the IV risk zone (1,365-8,549), which may have been caused by the high population density near the park. This study provides new insights into the characteristics of microplastics in urban park water and sediment.

Antibiotics and microplastics in manure and surrounding soil of farms in the Loess Plateau: Occurrence and correlation

The wide use of animal manure in farmland operations is a source of soil nutrients. However, the return of manure affected antibiotics and microplastics in the soil, thus the potential ecological risks cannot be overlooked. This study investigated the distribution of different antibiotics and microplastics and their correlation. It was found that multiple classes of veterinary antibiotics and microplastics could be detected simultaneously in most manure and soil. In manure, the average concentration of tetracycline antibiotics was higher than fluoroquinolones and sulfonamides. A much lower concentration of antibiotics was found in the soil samples relative to manure. The abundance of microplastics ranged from 21,333 to 88,333 n/kg in manure, and the average abundance was 50,583 ± 24,318 n/kg. The average abundance was 3056 ± 1746 n/kg in the soil. It confirmed that applying organic fertilizer to agricultural soil and the application of plastic mulch in farmlands introduced microplastics. Moreover, microplastics were found to be significantly correlated with antibiotics (r = 0.698, p < 0.001). The correlation between microplastics and antibiotics in soil was significantly weaker than that in manure. Farms could be the hotspot for the co-spread of microplastics and antibiotics. These findings highlighted the co-occurrence of antibiotics and microplastics in agricultural environments.

Is the application of organic fertilizers becoming an undeniable source of microplastics and resistance genes in agricultural systems?

The application of organic fertilizers is becoming an undeniable source of microplastics and antibiotic resistance genes (ARGs) in agricultural soils. The complex microbial activity further transfers resistance genes and their host bacteria to agricultural products and throughout the entire food chain. Therefore, the current main focus is on reducing the abundance of microplastics and ARGs in organic fertilizers at the source, as well as managing microplastics and ARGs in soil. The control of microplastic abundance in organic fertilizers is currently only achieved through pre-composting selection and other methods. However, there are still many shortcomings in the research on the distribution characteristics, propagation and diffusion mechanisms, and control technologies of ARGs, and some key scientific issues still need to be urgently addressed. The high-temperature composting of organic waste can effectively reduce the abundance of ARGs in organic fertilizers to a certain extent. However, it is also important to consider the spread of ARGs in residual antibiotic-resistant bacteria (ARB). This article systematically explores the pathways and interactions of microplastics and resistance genes entering agricultural soils through the application of organic fertilizers. The removal of microplastics and ARGs from organic fertilizers was discussed in detail. Based on the limitations of existing research, further investigation in this area is expected to provide valuable insights for the development and practical implementation of technologies aimed at reducing soil microplastics and resistance genes.

An evaluation on microplastic accumulations in Turkish soils under different land uses

Microplastic (MP) pollution is now widely reported in soil ecosystems. However, the level of this pollution in soil ecosystems has not been sufficiently elucidated. Moreover, there is little understanding of how land use conditions affect the occurrence and distribution of MPs in soils. Therefore, this study examined 55 soil samples (44 agricultural and 11 urban) from the Mediterranean, Aegean, and Marmara regions of Türkiye, representing both agricultural and urban land uses. The samples were analyzed for MP distribution characteristics, such as abundance, shape, size, color, and type. Different types of MPs were detected in the soil samples, and their averages in agricultural and urban soils were 192.7 ± 14.2 and 127.3 ± 21.6 particles kg-1, respectively. MP abundance in the soil exhibited variations between different land uses, with agricultural areas showing higher levels compared to urban areas. In agricultural soils, MPs were predominantly blue-colored (44.6 %), in the form of fibers (74.9 %), smaller than 1000 μm (66.1 %), and primarily constituted polyethylene (90.8 %). In urban areas, MPs were also blue-colored (54.7 %), had a fiber shape (64.2 %), smaller than 1000 μm (70.6 %), and mostly belonged to the polyethylene category (78.5 %). A significant difference in MP concentrations was observed between agricultural and urban areas, reflecting the influence of distinct land uses on MP levels. Moreover, Principal Component Analysis (PCA) revealed that soil properties, including pH, electrical conductivity, organic matter, aggregate stability, average weight diameter, sand, clay, and silt, emerged as the primary determinants influencing the abundance and size of MPs within the soil. These findings contribute valuable insights into the origins of soil MPs and the intricate connections between MPs and varying soil characteristics across diverse land use categories.

Organic amendment in climate change mitigation: Challenges in an era of micro- and nanoplastics

As a global strategy for mitigating climate change, organic amendments play critical roles in restoring stocks in carbon (C) depleted soils, preserving existing stocks to prevent further soil organic carbon (SOC) loss, and enhancing C sequestration. However, recent emerging evidence of a significant proportion of micro- and nanoplastics (M/NPs) occurrence in most organic substrates (e.g., compost manure, farmyard manure, and sewage sludge) compromises its role in climate change mitigation. Given the predicted surge of soil M/NPs proliferation in the coming years, we argued whether organic amendment remains a reliable climate change mitigation strategy. Toxicity effects of M/NPs influx within the soil matrix disrupt plants and their associated key microbial taxa responsible for crucial biogeochemical processes and restructuring of SOC, leading to increasing emissions of potent greenhouse gases (GHGs, e.g., CO2, CH4, and N2O) that feedback to aggravate the rapidly changing climate. Here, we summarize evidence based on literature that the discovery of M/NPs in organic substrates compromises its role in the climate change mitigation strategy. We briefly discuss the overview of synthetic fertilizers and their impact on SOC and atmospheric emissions. We discuss the role of organic amends in climate change mitigation and the emergence of M/NPs in it. We discuss M/NPs-induced damages to SOC and subsequent emissions of GHGs. We briefly highlight management approaches to clean organic substrates of M/NPs to improve their use in agrosystems and provide recommendations for future research studies. We found that organic amendment plays pivotal role in modulating the biotic and abiotic drivers responsible for climate mitigation. However, M/NPs in organic amendments weaken the regulatory mechanisms of organic amendments in plant-soil systems. We conclude that organic amendments of soils are critical for restoring SOC and mitigating the rapidly changing climate; yet, the discovery of M/NPs in organic substrates put their usage in a dilemma.

Distribution of microplastic contamination in the major tributaries of the Yellow River on the Loess Plateau

Microplastic pollution in rivers had gained increased attention worldwide. However, the differences in microplastic characteristics among major tributaries of large rivers and the environmental factors influencing these characteristics remain uncertain. Through field investigation and indoor experiments, the distribution of microplastics and their driving factors were investigated at 96 sampling sites along the three main tributaries (Huangfuchuan, Wuding and Yan River) of the Yellow River in the Loess Plateau. The results revealed that the average microplastic abundance followed this order: Yan River (430.30 items kg-1) > Wuding River (145.09 items kg-1) > Huangfuchuan River (253.33 items kg-1). The abundance was lower than that in most parts of the world. There was a generally increasing trend in average microplastic abundance from upstream to downstream in the three rivers. The most frequently observed microplastic colors observed were black and white, and the most common polymer type were PE and PS in all three rivers. The dominant shape and size in the three rivers were fiber and particles measuring 0.5-5.0 mm, all accounting for more than half of the total microplastic content. The microplastic abundance, shape, and size were primarily influenced by mean annual precipitation and population density. This relationship can be attributed to the fact that increased population density driven by higher demand and consumption of plastic products, while augmented rainfall aggravated the occurrence of floods and provided conditions for plastic degradation and accumulation. This study will provide fundamental data for pollution assessing and ecological protection of the Yellow River, and provide a certain reference for future management and protection on the Loess Plateau.

Characteristics and seasonal variation of microplastics in the wastewater treatment plant: The case of Bursa deep sea discharge

Microplastics (MPs) are an emerging pollutant that can be detected in all ecosystems, especially aquatic ecosystems. Wastewater treatment plants (WWTPs) are important point sources of MP release into the sea. In this study, the characteristics of MPs in wastewater and sludge samples taken from different units of WWTP in Bursa-Gemlik district for 12 months were investigated. Wastewater and sludge samples collected from 7 different points were classified as size, shape, color, and counted. The amount of MP in the influent and effluent of the WWTP, respectively; 107.1 ± 40.2 MP/L and 4.1 ± 1.1 MP/L. Although the MP removal efficiency of the WWTP is 96.17 %, approximately 74,825,000 MP is discharged into the Marmara Sea every day. The amount of MP in the sludge is 14.3 ± 7.1 MP/g. The amount of MP accumulated in 22tons of waste sludge formed daily in WWTP was calculated as 314,600,000 MP, and the annual accumulated amount was calculated as approximately 1.15 × 1011 MP. The MPs in the WWTP were mainly 1-0.5 mm in size. Fibers were the dominant MP shape in both the wastewater and sludge samples. Black and transparent were the dominant MP colors. Seven different polymer types of MPs were detected, which were mainly types of polyethylene, polypropylene, and polyethylene terephthalate. Despite the high removal efficiency in the investigated WWTP, it has been shown that it acts as an important source of MPs to the sea ecosystem due to the high discharge rates.