| Microplastics(MPs),plastic particles with a diameter smaller than 5mm,are considered the Trojan horse of PM2.5 and trace metals in water.They are widely distributed in water,air,soil,and even found in the digestive tracts of fish and human blood,posing direct or indirect impacts on ecological and human health.This study employed a combined method of microscopic observation and Fourier transform infrared spectroscopy analysis to determine the morphology and types of microplastics,investigating their characteristics and distribution in water sources and sediments.In addition,metagenomic sequencing was utilized to analyze the microbial community structure and functional genes,revealing the interaction between microorganisms and MPs,as well as the impact of different types of microplastics on microbial communities and functional genes related to biogenic element cycling.These findings can provide valuable insights for further studying the impact of microplastics on China’s freshwater ecosystem.The primary results of this study are as follows:(1)The abundance of microplastics in samples collected from Yiquan Lake was found to be in the range of 15.00-17.50 n/L for water samples and 3600.00-6050.00 n/kg for sediment samples,indicating a high level of contamination.Fibrous microplastics were found to be the most prevalent type in water samples,accounting for 42.42%,while particle-shaped microplastics were dominant in sediment samples,representing 38.86%of the total.The color of microplastics in water samples was mainly transparent and blue,while those in sediment samples were mostly transparent and yellow.Fourier Transform Infrared(FTIR)analysis revealed that polyethylene and polypropylene were the most prevalent microplastics in water samples,while polyethylene terephthalate and polystyrene were more prevalent in sediment samples.These results indicate that the sampling location is significantly impacted by microplastic pollution,which is likely caused by human activities,and further monitoring and evaluation are necessary.(2)After conducting metagenomic analysis of microbial community function,it was determined that microplastics have a significant impact on microbial community structure,species abundance,and diversity.Among the three types of microplastics(polyethylene,polypropylene,and polystyrene)added in simulated experiments,polyethylene had the most pronounced effect on the microbiome,resulting in a significant decrease in microbial abundance.Through Circos analysis and functional contribution analysis,it was found that microplastics had a significant impact on the biogenic sulfur cycle,leading to changes in its functional contribution.Specifically,polyethylene was found to have the greatest impact on the sulfur cycle among the three types of microplastics,with the most significant changes observed in correlation analysis and the highest rate of functional contribution change.(3)A simulated experiment was conducted to investigate the effects of hydrostatic pressure,an environmental factor that significantly influences the microbial ecology at the sediment-water interface of reservoirs.Fourier-transform infrared spectroscopy analysis revealed that,in the presence of microorganisms,an increase in hydrostatic pressure led to changes in the size and shape of microplastics in sediment samples.The impact of hydrostatic pressure was particularly pronounced for small microplastics(20-500 μm),promoting the decomposition of fibers,particles,and fragments into smallersized microplastics.Notably,the average size of polyethylene terephthalate microplastics decreased from 425.78 μm under atmospheric pressure to 366.62 μm under 0.7 MPa hydrostatic pressure.Additionally,high hydrostatic pressure increased the relative abundance of plastic-degrading bacterial genera,such as Rhodococcus,Flavobacterium,and Aspergillus.Eight genes related to the biodegradation of polystyrene,polyethylene,and polyethylene terephthalate microplastics were annotated,including paa K,lad A,and tph A3.The abundance of tph A3 was negatively affected by hydrostatic pressure,providing evidence for how microbial metabolism of polyethylene terephthalate can lead to a reduction in microplastic size. |
