| Microplastic,as an emergent pollutant,has received global attention due to their ubiquitous presence in the environment and unknown hazards to organisms.Recently,soil microplastic pollution has also received great attention.However,there is little information available on the effects of microplastic on heavy metal availability and microbial activity in the soil,especially near the e-waste recycling area.The organic and inorganic pollutants loaded in the microplastics may gradually release into the soils during the physicochemical or microbial aging processes.The microplastic and pollutants can affect the basic properties and microbial activity in soils.In this study,the polyvinyl chloride（PVC）microplastic with chemical additives was selected.The aim of this study was,1)to investigate the potentially release of heavy metals and mineral elements in PVC microplastic under the different concentrations of hydrogen peroxide（H2O2）solution（0,1%,3%,6%,12%,21%,and 30%）.2)to evaluate the addition rates（0,2.5%and 5%）of PVC microplastic on the bioavailability and chemical speciation transformation of heavy metals in acidic and alkaline soils from Xintong and Huanshan,respectively,and the seed germination and heavy metal uptake by radish during soil incubation experiment;3)to study the effects of PVC microplastic addition on the structure and function of soil bacterial and fungal communities by 16S r RNA and ITS gene sequencing techniques.The mainly results of this study were as follows:（1）According to the chemical oxidation of additives-loaded PVC microplastic by H2O2 under different concentrations,it was observed that there was no noticeable difference between raw and oxidized PVC microplastic surface area and morphology.The two most abundant elements in the PVC microplastic were Pb and Ca.The total concentrations of Pb and Ca in the PVC microplastic were 2832.14±38.11 mg kg-1 and173.18±6.96 g kg-1 respectively.The concentrations of the releasable heavy metals and mineral elements in the PVC microplastic were increased gradually with the concentrations of H2O2.The concentration of releasable Pb was 623.58 mg kg-1,and it was higher than the other metals.The results showed that the inner heavy metals in the PVC microplastic could release to the environment and cause soil and water pollution due to the chemical oxidation.（2）During the soil incubation experiment,the addition of PVC microplastic increased the value of acidic soil pH（from 4.58 to 7.69-7.90）.However,the pH of alkaline soil treated with PVC microplastic was not change.The concentrations of total Pb and Cd in acidic and alkaline soils,and the concentration of bioavailable Pb in alkaline soil were increased,but the concentrations of Cd,Mn,Pb,and Zn in acidic soil were significantly decreased with the addition of PVC microplastic.The residual form of Cd,Mn,Pb and Zn in the alkaline soil increased after incubation at days 120,but those in the acidic soil decreased.The higher application of PVC microplastic 5%（w/w）in soils reduced the germination index（GI）of radishes.The lower application of PVC microplastic 2.5%in soils decreased the concentrations of Cd,Mn and Zn in radish plant,but increased Pb concentration.Results indicated the additives-loaded PVC microplastic has different impact on acidic and alkaline soils pH and risk of heavy metal pollution,it was due to the chemical properties of PVC microplastic and basic properties of soils.（3）The analysis of soil microbial after soil incubation experiment showed that the addition of PVC microplastic reduced the bacterial abundance in the acidic soil,but it increased the fungal abundance in alkaline soil.The most dominant bacterial phyla is Proteobacteria,accounting for 30.97%-80.50%of the total bacterial sequences.The dominant fungi phyla were Ascomycota（29.51%-96.02%）,Basidiomycota（1.21%-22.41%）,Mortierellomycota（0.52%-58.38%）,and Rozellomycota（0.10%-1.79%）,respectively.The addition of PVC microplastic in the soils improved the growth ofγ-Proteobacteria,Bacteroidia andα-Proteobacteria,but it inhibited the growth of Gemmatimonadetes,δ-Proteobacteria and Actinobacteria in bacteria classes.The addition of PVC microplastic in the soils significantly changed the distribution of microorganisms,affected the community succession and construction,and decreased the interaction and connectivity of microbial.However,the addition of PVC microplastic promoted the specific functions and structure of soil microorganisms. |
