| Microplastics(MPs)pollution has gained much attention as a topical environmental issue.As an important site for the enrichment of terrestrial pollutants,the series of environmental impacts of MPs in soil cannot be ignored,there is an urgen t need for continuous and in-depth research of MPs.As a type of plastic commonly used in agricultural production,polyethylene(PE)and the large number of associated products has led to the widespread presence of PE-MPs in agricultural soil environment.In this study,we were used peas in the study in order to investigate the effect of MPs on seed germination,plant growth,soil physical and chemical properties and microbial comm unities properties.Based on the germination tests(applied PE-MPs with particle sizes of 5μm,0.1μm and 0.08μm within the concentrations of 50 mg/L,100 mg/L,200 mg/L,500 mg/L,1000 mg/L and 2000 mg/L)and the pot tests(applied PE-MPs with particle sizes of 550μm,50μm and 6.5μm within the mass concentrations of 0.5%,1.0%and 2.0%,two fertilisation treatments were also considered).The main conclusions of the study were as follows:(1)PE-MPs significantly shortened the average germination tim e of seeds,0.08μm PE-MPs had a significant effect on germination potential and germination rate.When the concentration increased to 2000 mg/L,seed germination rate was notably reduced and seed germination was affected.At the main time,the plant biomass,photosynthetic pigments and oth er substances accumulation behaviour showed a single change trend in concentration change.(2)PE-MPs had a significant impact on pea plant height,inhibiting the plant growth,with the inhibitory effect on pea plant height increasing notably as the concentration gradually increased,with 14%,19%and 34%reduction in pea plant height in each group of the low fertility treatment compared with the CK respectively.Under the low-fertility condition,PE-MPs significantly inhibited the total root length,root volume,surface area and the mean root diameter,and reduced the plant dry matter accumulation in peas.Besides,it led to a reduction in root-to-crown ratio,which increased with particle size and applied concentration.(3)PE-MPs mainly increased the content of≥2 mm and 0.25-2 mm particle size agglomerates and decreased the content of 0.053-0.25 mm and<0.053 mm particle size agglomerates in soil,while increasing the content of soil water-stable agglomerates(R0.25),mean weight diameter(MWD)and geometric mean diameter(GWD),and decreasing the soil fractal dimension(D).(4)Changes in the concentration of PE-MPs had an effect on the total soil nitrogen(TN)content under low fertility conditions.Soil nitrate nitrogen(NO3--N)and ammonium nitrogen(NH4+-N)has significantly-negatively correlation with microplastic particle size.Soil total phosphorus(TP)content has a significantly-negatively correlation with microplastic concentration.Soil microbial carbon(MBC)and microbial nitrogen(MBN)responded differently to microplastic concentration under different fertility conditions,showing an increase with microplastic application at low-fertility conditions,and a decrease with microplastic application at high-fertility conditions.The response of microbial phosphorus(MBP)to microplastics increased significantly with microplastic concentration only under the low-fertilizer conditions.Soil leucine aminopeptidase(LAP)and alkaline phosphatase(ALP)activities were mainly influenced by the microplastics concentration,with enzyme activity increasing and then decreasing with microplastics concentration.Soil β-1,4-glucosidase(BG)activity was more sensitive to the PE-MPs particle size,with D1 and D2 treatments showing an overall promotion of activity and D3 treatment having an inhibitory effect.(5)PE-MPs did not significantly change soil bacterial community number diversity and OTUs.The addition of PE-MPs significantly increased the relative abundance of Amoebacteria and Acidobacteria,and had a decline on the relative abundance of Firmicutes in phylum level.At the class level,it is mainly composed of α-proteobacteria,γ-proteobacteria,and parent chain bacteria.Microplastics mainly promote the relative abundance of γ-proteobacteria in soil.According to the Pearson correlation analysis between soil nutrients and enzyme activity on soil bacterial communities,it showed that PE-MPs can act directly on soil bacteria,and also indirectly on the abundance and diversity of soil bacterial communities through the effects on soil nutrients and enzyme activity.(6)PE-MPs significantly inhibited the diversity and OTUs of soil fungal communities under high-fertility condition.The dominant fungal communities in the soil at the phylum level mainly included Cysticercus,Ascomycetes and Streptomycetes,while the addition of microplastics significantly increased the relative abundance of Cysticercus and decreased the relative abundance of Ascomycetes and Streptomycetes;the dominant fungal communities in the soil at the phylum level included Sordariomycetes,Dothideales and Eurotiomycetes,where Sordariomycetes were significantly dominant in the soil,but their relative abundance was also affected by the relative abundance with Dothideales and Eurotiomycetes,and there may be competition between them.The correlation between soil nutrients and enzymatic activity on soil fungal communities showed that microplastics can directly affect soil bacteria,also indirectly affect the abundance and diversity of soil fungal communities through the effects on soil nutrients and enzymatic activity. |
PDF Full Text Request