Effects Of Phenolic Foam On Earthworm And Community And Function Of Microbes In Soil

Phenolic foam（PF）was used as a culture substrate in crop seedlings,cuttings,and other fields because of its high foam porosity,good breathability,and particular structure.With the increasing use of phenolic foam,most of phenolic foam were accumulated in the soil after being discarded,and the accumulation of phenolic foam associated microplastics（PF-MPs）have valuable and vital impacts on soil ecosystems.However,the effects of these microplastics on soil fauna and microbiome are still uncertain.In this paper,we analyzed the acute and chronic toxicity of PF-MPs on Eisenia fetida（E.fetida）and microbial enzyme activities using an artificial soil.We further investigated the effects of PF-MPs on soil microbes including microbial community,diversity,activity,and functions associated with CNPS cycles,and explored their effects on plant growth.The main findings are as follows:（1）The half lethal concentration of phenolic foam was higher than 5000mg·kg^-1.GSH-Px activities of E.fetida in soils treated with 0-5000 mg·kg^-1phenolic foam ranged from 15.06 to 56.96 U·mgport^-1,Meanwhile,the SOD activities of E.fetida in soils ranged from 20.81 to 58.10 U·mgport^-1.The consequence exhibited that activities of GSH-Px and SOD in soils with phenolic foam were significantly（P<0.05）higher than that in control soil,which indicating anti-oxidation response of E.fetida to granular phenolic foam.Soil respiration rates ranged from 0.041 to 0.055μmol·CO₂·g^-1·h^-1.Granular phenolic foam obviously（P<0.05）inhibited soil respiration,but no significant in S-NP and S-UE activities remained at a similar level.（2）PF-MPs(1-10 g·kg^-1)changed soil microbial community composition,and the effect was plant-dependable.Compared with control soil,the high concentration of PF-MPs significantly decreased Eukaryotic and Archaeal diversity.Bacteria and Eukaryote associated with MPs biodegradation,such as Bacteroidetes,Actinobacteria and Basidiomycota phylum were significantly enriched in the treatments with higher concentration of PF-MPs.Moreover,soil physicochemical properties and the concentration of PF-MPs also significantly affected Bacterial and Archaeal community structures in soils.Co-occurrence network analysis showed that the interactions between ASVs was mainly positive correlation which was greater than 52.27%,and the addition of PF-MPs would increase the positive correlation between Bacterial ASV.On the contrary,PF-MPs amendment reduced the positive correlation between Eukaryotic taxa and between Archaeal ASVs.The PF-MPs gradually increased keystone taxa and functional redundancy,the Bacterial,Eukaryotic and Archaeal connectors were greated than45.04%,18.18%,4.25,respectively.Actinobacteria,Ascomycota and Nitrososphareia,as the most detected phylum,play a critical role in maintaining soil ecological functions and community stability.（3）Low concentration of PF-MPs increased the absolute and relative abundance of some functional genes associated with carbon,nitrogen,phosphorus,and sulfur cycles,and gradually changed element cycling in soils.Meanwhile,the functional genes are also affected by plant species.The relative abundance of CNPS functional genes was significantly negative with Eukaryotic alpha diversity.（4）PF-MPs affected the N₂O and N₂ emission in soils by changing genes associated with nitrification.The addition of PF-MPs significantly reduced gaseous nitrogen in soils.Bacterial alpha diversity was significantly and positively correlated with N₂O emission.Besides,Eukaryotic alpha diversity is obviously and and negatively correlated with N₂O.PF-MPs significantly promoted soil respiration but had no significant impcact on soil acid phosphatase activity（S-ACP）.Eukaryotic and Archaeal alpha diversity were significantly and negatively correlated with S-ACP activity.The obvious and positive relationship between Eukaryotic diversity and plant biomass suggested that the declination of alpha diversity may also reduce plant growth.Eukaryotic and archaeal diversity significantly correlated with soil microbial activity and functional cycling,which may predict the effects of PF-MPs on plant growth,soil microbial activity and functional gene abundance,especially eukaryotes.