Study On The Mechanism Of Earthworm-Plant Synergistic Removal Of Chromium From Soil

With the development of industry,the pollution of chromium in the soil has become more and more serious,and it will enter the human body through the food chain,thereby causing harm to human health.At the same time,this non-degradability and accumulation make the treatment of chromium-contaminated soil very difficult.In this study,earthworms(Eisenia vulgaris,Eisenia viridis),plants(ryegrass,corn),and earthworms+plants were used as three treatment methods to treat different concentrations(15mg/kg,50mg/kg)of different types(acid,neutral,alkaline)chromium contaminated soil for remediation,the experiment period is 30 days,and the treatments were directly compared based on the analysis,the chromium removal rate is used as the main indicator to explore the mechanism of earthworms and plants to repair chromium pollution.The main conclusions are as follows:(1)After standing for 30 days,the removal rate of chromium under natural conditions(C1E0P0,C2E0P0)is almost 0.In this experiment,earthworms and plants are added to increase the removal rate of chromium.The removal rate of chromium by earthworms)+plants(ryegrass,corn)>the removal rate of chromium by earthworms>the removal rate of chromium by plants,the removal rate of chromium by Eisenia vulgaris and Eisenia viridis significant difference,the removal rate of chromium by ryegrass is significantly higher than that of corn;among them,the treatment of Eisenia vulgaris+ryegrass has the best chromium removal rate,and the removal rate of acid low chromium soil and high chromium soil is 81.16%and 75.88%,the removal rate of neutral low chromium soil and high chromium soil is 88.44%,79.47%.The removal rate of alkaline low chromium soil and high chromium soil is 73%and 69.58%.This treatment is in neutral soil is the best repair effect is in the middle.(2)Regardless of the type of soil conditions,after adding earthworms,the form of chromium in the soil changes significantly,from a residue state and an oxidizable state to an acid extractable state and a reducible state.After planting plants,the acid extractable and reducible chromium in soil is significantly reduced,while the residual and oxidizable chromium has no obvious change.After adding earthworms,plant biomass and chromium enrichment increased significantly,but almost all corn died in alkaline soil,so there was no significant change in corn biomass and enrichment in alkaline soil.(3)After adding earthworms and plants to acid soil,soil pH increased significantly,and organic matter decreased significantly.The removal rate of chromium was significantly positively correlated with pH and negatively correlated with organic matter;adding earthworms and plants to neutral soil.After that,soil pH tends to change to 7.00,organic matter increases significantly,pH is extremely negatively correlated with the removal rate of chromium in the soil,and OM is extremely positively correlated with the removal rate of chromium in the soil;add earthworms and plants to alkaline soil.Later(except for corn)soil pH decreased significantly,and organic matter increased significantly.The removal rate of chromium was significantly positively correlated with pH,and significantly negatively correlated with organic matter.(4)As earthworms enter the chromium-contaminated soil,the MDA and SOD enzymes in the earthworms increase significantly,while CAT and GST enzymes decrease significantly,and the removal rate of chromium in the soil is significantly positively correlated with MDA and SOD.(5)In acidic soil,at the phylum level,the main species in earthworms are Proteobacteria,Bacteroidota,Firmicutes and Actinobacteriota,among which Proteobacteria have the highest abundance,among which Paenibacillus,unclassified?f?Microbacteriaceae,and Micromonospora have become the dominant genera.In neutral soil,at the phylum level,earthworms are mainly.The proportion of species are Firmicutes,Proteobacteria and Actinobacteria,among which Firmicutes are the most abundant,among which Micromonospora and Gaiella are dominant bacteria Genus.In alkaline soil,at the phylum level,the main species in earthworms are Proteobacteria,Actinobacteria and Firmicutes,among which Proteobacteria have the highest abundance.Among them,Microbacterium,Ralstonia and Rhodococcus have become the dominant genera.