科研成果

Wetlands are major microplastic sinks with a large atmospheric input. However, many details of such deposited atmospheric microplastics entering into wetlands remain unclear, including temporal patterns of input and ecological effects. We monitored the aerial microplastics during four seasons in eleven economically developed cities along the lower reaches of the Yangtze River Basin, China. The average microplastic deposition rate was 512.31 items m−2 d−1, equivalent to an annual contribution of 17.46 metric tons of plastic to the surveyed wetlands with a total area of 1652 km2. These microplastics were predominantly composed of polyamide and polyethylene terephthalate with 61.85 ± 92.29 µm sized pellets, and we obtained similar results for microplastics intercepted on moss in wetlands. Microplastic input varied between wet and dry periods, primarily influenced by wind, rainfall and ozone concentration. Civilian vehicle density and textile industry were the primary socioeconomic factors driving microplastic deposition. Further indoor microcosm experiments revealed that moss phyllosphere bacterial community structure and function were influenced by microplastic abundance and size, exemplifying the unique ecological risks of aerially deposited microplastics to wetlands. These results indicate that mosses and their phyllosphere microbiota could serve as bio-indicators of aerial microplastic characteristics and impacts.

Plastisphere, characterized by microbial colonization on plastic debris, has attracted concern with its adverse environmental effects. The microbial features have been increasingly investigated; however, there lacks direct evidence for microplastics serving as carbon sources and enriching plastic-degrading microorganisms. Here, we obtained microbial communities from soil microplastics, analyzed the dissimilarity compared with soil, and characterized the plastic-degrading potential of isolates from plastisphere. Results showed the plastisphere communities significantly differed from soil communities and exhibited a higher relative abundance of Nocardia and Rhodococcus. To verify the selective enrichment of plastic-degrading microorganisms in the plastisphere, culture-based strategies were employed to evaluate the polyethylene (PE) degradation potential of two isolates Nocardia asteroides No.11 and Rhodococcus hoagii No.17. They could grow solely on PE and led to significant weight loss. FTIR and SEM analysis revealed the formation of new functional groups and the destruction of structural integrity on PE surfaces. Genes related to PE biodegradation were identified by genome-wide sequencing thus recognizing relevant enzymes and elucidating potential pathways. Overall, this report combined culture-free and culture-based approaches to confirm the plastic degradation potential of selectively enriched microorganisms in soil plastisphere, providing a positive perspective toward promoting microplastic biodegradation in farmland soil by enhancing natural microbial processes.

Polyhydroxyalkanoates (PHAs) are a class of microbially synthesized polyesters with diverse structures with renewability, biodegradability, good biocompatibility, and broad application prospects. However, the level of commercialization of PHAs remains low. The high recovery cost is one of the main reasons preventing the widespread use of these "green polymers". For decades, efforts have been made to explore lower-cost, greener, and more economical PHAs recovery strategies, and significant progress has been made. This review presents cell lysis and yeast surface display (YSD)-based bio-recovery strategies for PHAs, and then proposes a model hypothesis for protein-mediated secretion of PHAs drawing on the lipid secretion model to provide essential information for further cost reduction and efficiency in the recovery of PHAs. In addition, this review also highlights the bio-recovery strategy of extracellular PHAs based on synthetic biology and exploring specific PHAs secretion mechanism is a promising strategy for reducing the cost of PHAs recovery in the future.

Microplastics, recognized as some of the most pervasive and enduring pollutants, have emerged as a potential threat to environmental eco-health. While much is known about the effects of microplastics on soil microorganisms, our understanding of how they interact with terrestrial organisms and the underlying mechanisms remains limited. In this study, the effects of polyethylene microplastics at a concentration of 0.5 % (w/w) on the antioxidant enzymes, gut microbiota of Eisenia fetida and the soil microbiota on days 1, 3, 7, 15, and 30 were investigated. The results indicated that exposure to microplastics slightly increased the activities of superoxide dismutase (1.22-fold on day 3, 1.12-fold on day 7) and catalase (1.10-fold on day 3, 1.09-fold on day 7) in E. fetida, while exposure markedly decreased peroxidase activity (1.33- to 1.79-fold) throughout the whole period. Both the soil microbiota and the gut microbiota of E. fetida in terms of diversity and composition were significantly affected by the microplastic amendment, and their structure tended to be similar throughout the exposure time. The family Nocardiaceae was significantly enriched in both the soil and E. fetida gut biota with microplastic exposure. Our results demonstrated that the antioxidant enzyme response of E. fetida was closely related to both the microbiota, although this relationship with the gut microbiota may have been weakened by microplastic exposure. Overall, this study furnishes new perspectives on the ecotoxicity of microplastics, revealing significant implications for the vitality of soil-dwelling organisms and the overarching health of terrestrial ecosystems.

Microplastics are found in various human tissues and are considered harmful, raising concerns about human exposure to microplastics in the environment. Existing research has analyzed indoor and occupational scenarios, but long-term monitoring of ambient atmospheric microplastics (AMPs), especially in highly polluted urban regions, needs to be further investigated. This study estimated human environmental exposure to AMPs by considering inhalation, dust ingestion, and dermal exposure in three urban functional zones within a megacity. The annual exposure quantity was 7.37 * 104 items for children and 1.06 * 105 items for adults, comparable with the human microplastic consumption from food and water. Significant spatiotemporal differences were observed in the characteristics of AMPs that humans were exposed to, with wind speed and rainfall frequency mainly driving these changes. The annual human AMP exposure quantity in urban green land spaces, which were recognized as relatively low polluted zones, was comparable with that in public service zones and residential zones. Notably, significant positive correlations between the AMP characteristics and the pathogenicity of the airborne bacterial community were discovered. AMP size and immune-mediated disease risks brought by atmospheric microbes showed the most significant relationship, where Sphingomonas might act as the potential key mediator.

The plastisphere may act as reservoir of antibiotic resistome, accelerating global antimicrobial resistance dissemination. However, the environmental risks in the plastisphere of field microplastics (MPs) in farmland remain largely unknown. Here, antibiotic resistance genes (ARGs) and virulence factors (VFs) on polyethylene microplastics (PE-MPs) and polybutylene adipate terephthalate and polylactic acid microplastics (PBAT/PLA-MPs) from residues were investigated using metagenomic analysis. The results suggested that the profiles of ARG and VF in the plastisphere of PBAT/PLA-MPs had greater number of detected genes with statistically higher values of diversity and abundance than soil and PE-MP. Procrustes analysis indicated a good fitting correlation between ARG/VF profiles and bacterial community composition. Actinobacteria was the major host for tetracycline and glycopeptide resistance genes in the soil and PE-MP plastisphere, whereas the primary host for multidrug resistance genes changed to Proteobacteria in PBAT/PLA-MP plastisphere. Besides, three human pathogens, Sphingomonas paucimobilis, Lactobacillus plantarum and Pseudomonas aeruginosa were identified in the plastisphere. The PE-MP plastisphere exhibited a higher transfer potential of ARGs than PBAT/PLA-MP plastisphere. This work enhances our knowledge of potential environmental risks posed by microplastic in farmland and provides valuable insights for risk assessment and management of agricultural mulching applications.

Phyllosphere is the largest interface between the atmosphere and terrestrial ecosystems and serves as a major sink for atmospheric microplastics (MPs). It is also a unique habitat for microbiota with diverse ecological functions. This field study investigated the characteristics of atmospheric MPs adsorbed on leaves with automatic technology, and found their abundance was 3.62 ± 1.29 items cm−2. MPs on leaves were mainly below 80 µm, and dominated by polyamide, polyethene, and rubber. MPs on leaves correlated significantly with the structure and functions of the phyllosphere bacterial community (PBC). Both the MPs abundance and size distribution (MSD) were positively correlated with the α diversity and negatively correlated with the β diversity and network complexity of PBC. PBC functions of environmental and genetic information process were negatively correlated with MPs abundance, and functions related to human diseases and cellular process were positively correlated with MSD significantly. The relative abundance of Sphingomonas was significantly correlated with the MSD, suggesting that Sphingomonas might emerge as the key genus involved in the pathogenicity of PBC mediated by MPs. These results highlighted the ecological health risks of atmospheric MPs as they can be transferred anywhere and potentially increase the pathogenicity of local phyllosphere microflora.

The widespread secondary microplastics (MPs) in urban freshwater, originating from plastic wastes, have created a new habitat called plastisphere for microorganisms. The factors influencing the structure and ecological risks of the microbial community within the plastisphere are not yet fully understood. We conducted an in-site incubation experiment in an urban river, using MPs from garbage bags (GB), shopping bags (SB), and plastic bottles (PB). Bacterial communities in water and plastisphere incubated for 2 and 4 weeks were analyzed by 16S high-throughput sequencing. The results showed the bacterial composition of the plastisphere, especially the PB, exhibited enrichment of plastic-degrading and photoautotrophic taxa. Diversity declined in GB and PB but increased in SB plastisphere. Abundance analysis revealed distinct bacterial species that were enriched or depleted in each type of plastisphere. As the succession progressed, the differences in community structure was more pronounced, and the decline in the complexity of bacterial community within each plastisphere suggested increasing specialization. All the plastisphere exhibited elevated pathogenicity at the second or forth week, compared to bacterial communities related to natural particles. These findings highlighted the continually evolving plastisphere in urban rivers was influenced by the plastic substrates, and attention should be paid to fragile plastic wastes due to the rapidly increasing pathogenicity of the bacterial community attached to them.

As emerging pollutants, microplastics (MPs) are widely distributed in water, soil and atmosphere, and have become a popularly concerned environmental and social issue. The research on atmospheric microplastics (AMPs) started later than that on the MPs in soil and water, but AMPs’ potential environmental impacts are explored in an even wider range. Based on the literatures on AMPs since 2015 as well as those about MPs in water and soil, this paper systematically reviews the distribution, source, transport of AMPS and the environmental and ecological impacts of AMPs. The results show that AMPs are distributed in global atmosphere, and have been detected in the atmosphere of urban, suburban, remote areas and indoor air. The concentrations of AMPs were detected in a range 2 to 77000 n m–2 d–1 or 0 to 1583 n m–3. The distribution characteristics of MPs in atmosphere are affected by environmental factors such as indoor and outdoor environment, underlying surface type and airflow, etc. In general, the concentration and the diversity of AMPs’ shape and composition are higher in the places near to MPs the source, but the wind, precipitation and even local animals could reshape the characters of AMPs. The sources of AMPs are mainly the production, use and recycling processes of plastic products, as well as land and sea where MPs accumulated. Studies also showed that abrasion of vehicle tires and the use of synthetic textile are major sources. What’s noteworthy is that the COVID-19 pandemic has made masks as necessities of life, which indirectly exacerbated the pollution of AMPs. The transport of MPs can occur in atmospheric environment, such as suspension, deposition and diffusion, and is affected by the morphology of MPs, wind direction, precipitation and other atmospheric factors. The diffusion of MPs in atmosphere, also known as atmospheric transport, is an important part of the global plastic cycle. AMPs’ transport path is mostly studied of Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) by conducting backward trajectory simulation, and their transport volume is estimated mainly through deposition and aerodynamic model. In addition, AMPs have unique physical and chemical properties, which can affect regional atmospheric environmental quality, change regional and global climate. It could also adsorb heavy metals, organic pollutants and harmful microorganisms during transport, resulting in greater health risks to human. Also, AMPs could affect atmospheric ecosystems through food chains and providing microbial niches, and alter structure and functions of terrestrial forest and water ecosystems through deposition. There are still some unsolved scientific and technical questions. Due to the lack of standardized sampling and identification means, the past research methods on AMPs are different on sampling and physical analysis, which make information comparison difficult. The observations of AMPs’ environmental behaviors, the atmospheric transport, source attribution and trans-regional effects of AMPs are still limited. Therefore, some conclusions from laboratory researches cannot fully explain the uncertainty of in natural environment. Based on the analysis, it is suggested that future scientific research on AMPs should focus on standardization of research methods, the establishment of source list, transport mechanism and environmental and ecological impacts. It is necessary for the study of AMPs to establish a set of scientifically credible and technically feasible monitoring techniques as well. Because AMPs could be transported to different ecosystems and could enter the human body through a variety of ways, it is urgent to study the physiological and ecological status of human body and ecosystems which are continuously exposed to AMPs pollution.

The inhomogeneity of plastisphere and soil may result in different microbial communities, thus potentially affecting soil functions. Biodegradable plastics offer an alternative to conventional plastics, nevertheless, the inadequate end-of-life treatment of biodegradable plastics may release more microplastics. Herein, we collected PE and PBAT/PLA microplastics in plastic-mulching farmland in Hebei, China. The bacterial communities of soil, PE and PBAT/PLA plastisphere were investigated using 16 S high-throughput sequencing. We found that the structure of bacterial communities in PBAT/PLA plastisphere were significantly distinct from PE plastisphere and soil. The alpha diversities in PBAT/PLA plastisphere were significantly lower than PE plastisphere and soil. Statistical analysis of differentially ASVs suggested that PBAT/PLA microplastics act as a filter, enriching taxa with the capability to degrade plastic polymers such as Proteobacteria and Actinobacteria. Compared to PE plastisphere, PBAT/PLA plastisphere has networks of less complexity, lower modularity, and more competitive interactions. Predicted metabolic pathways involved in human diseases, carbohydrate metabolism, amino acid metabolism, and xenobiotic biodegradation and metabolism were promoted in PBAT/PLA plastisphere, along with the facilitation in abundance of genes associated with carbon and nitrogen cycling. Our results highlighted the uniqueness of plastisphere of biodegradable microplastics from conventional microplastics and their potential impact on soil functions