Effects Of Microplastics And Cadmium On Plant Growth And The Diversity Of Arbuscular Mycorrhizal Fungi

In terrestrial ecosystems,microplastics(MPs)and heavy metals are common pollutants,but it is not clear how they affect plants,soil microorganisms,soil physical and chemical properties and the availability of heavy metals.Therefore,the potted maize experiment was used to explore single and combined effects of cadmium(Cd)and MPs with different particle sizes(0.6-1mm,and 100-154 ?m),types(PE,PS,and PLA)and concentrations(i.e.,0,0.1%,1%,and 10%).This experiment explored the effects of MPs and Cd on maize biomass,chlorophyll content,plant absorption of Cd,bioconcentration factor(BCF),transport factor(TF),soil pH,available Cd,soil arbuscular mycorrhizal(AM)fungi diversity and species composition structure.The main results were as follows:1.PE(0.6-1 mm)treatment: when PE treatment was added alone,with the increase of PE concentration,the shoot and root biomass of maize did not change significantly,the content of chlorophyll a and the ratio of chlorophyll a/b increased obviously,and the abundance and diversity of AM fungal community did not change significantly.When both PE and Cd were added,with the increase of PE concentration,the shoot and root biomass of maize decreased but not significantly.Soil pH and the bioavailability of Cd in the soil increased.BCF of Cd in the roots increased,but TF did not change.There was no significant change in the abundance and diversity of AM fungi.2.PE(100-154 ?m)treatment: When PE was added alone,with the increase of PE concentration,the shoot and root biomass of maize did not change significantly,the changes in chlorophyll indicators were not considerably,and the soil pH decreased.Moreover,the abundance and diversity of the AM fungal community did not change significantly,but the composition of the community changed,and PEappreciably increased the relative abundance of Glomus.When both PE and Cd were added,the shoot biomass did not change significantly,the root biomass decreased significantly,the soil pH,the availability of Cd in soil and the BCF of Cd in roots increased significantly.There was no significant change in TF.There was no significant change in the abundance and diversity of AM fungi,but there was a significant change in Glomus and Paraglomus when PE(100-154 ?m)and Cd combined.3.PS(100-154 ?m)treatment: When PS was added alone,with the increase of PS concentration,the shoot biomass of maize did not change much,the root biomass decreased,the chlorophyll index did not change significantly,and the soil pH did not change.In addition,the abundance,diversity and composition of the AM fungal community did not change considerably.When PS and Cd were added at the same time,the aboveground and underground biomass decreased significantly,the soil pH increased,the bioavailability of Cd in the soil increased,and other indicators did not change significantly.The abundance of AM fungi did not change significantly,diversity decreased significantly,and species composition changed significantly.4.PLA(100-154 ?m)treatment: When PLA was added alone,as the PLA concentration increased,the shoot and root biomass of maize significantly decreased(especially at 10% concentration),the chlorophyll ratio decreased,and the soil pH increased considerably.In addition,the abundance of the AM fungal community did not change significantly,the diversity increased significantly,and the community composition changed distinctly.When PLA and Cd were added at the same time,the aboveground and underground biomass decreased significantly,the soil pH increased significantly,the total chlorophyll content decreased conspicuously,and the availability of Cd in the soil increased.The abundance and diversity of AM fungi did not change significantly,and the species composition structure significant changed.The results of the study found that under a single Cd treatment,Cd inhibited the shoot and root biomass of plants,and reduced the production of chlorophyll content.The Cd absorbed by plants increased significantly,without significantly changing the abundance and diversity of AM fungi.The type and concentration of MPs had a significant influence on the measurement parameter.Under the combined treatmentof MPs and Cd,the two had a significant interaction on multiple indexes.For example,compared with no Cd addition,Cd addition treatments(PE and Cd,PS and Cd)all appreciably reduced plant biomass and inhibited normal plant growth;all treatments combined with the two significantly increased soil pH and Cd bioavailability.In addition,the treatment with Cd addition did not conspicuously change the abundance and diversity of AM fungi compared with the treatment without Cd addition.Here,we found that although MPs increased the availability of Cd in the soil,they had no significant effect on the content of Cd in plants.MPs mainly affected the absorption of Cd by affecting the growth of plants.This article can provide a reference for understanding the biological effects and ecological risks of microplastics and heavy metal pollutants in soil.