Study On The Heavy Metal Enrichment Characteristics Of Moso Bamboo On Composite Heavy Metal Contaminated Soil

Moso bamboo(Phyllostachys pubescens)has high biomass accumulation capacity and has potential as a phytoremediation species.In this thesis,moso bamboo was selected as a phytoremediation species for tailings complex heavy metal contaminated soils,and in response to the decommissioning of a tailings mine in southern China and the ecological restoration needs around the mine site,the three-year-old Phyllostachys pubescens was used as a research object in a standard guest soil testbed for complex heavy metal contaminated soils.The study investigated the physiological response of moso bamboo to heavy metal stress by measuring photosynthetic parameters,chlorophyll fluorescence parameters and antioxidant metabolizing enzyme activities.The main findings of the study are as follows.(1)The study showed that the heavy metal content of Cr,Mn,Fe,Ni,Cu,Zn and Pb decreased by 64 %,82 %,48 %,85 %,73 %,58 % and 89 %(P<0.05)respectively in the inter-rooted soil compared to the non-inter-rooted soil under control conditions.Under treatment group conditions,the heavy metal content of Cr,Mn,Fe,Ni,Cu,Zn and Pb decreased by 46 %,41 %,21 %,48 %,54 %,63 % and 20 %(P<0.05)respectively in the inter-rooted soil compared to the non-rooted soil.The root system of moso bamboo significantly reduced the heavy metals in the soil.The results of the soil enzyme activity study showed that under treatment group conditions,cellulase activity increased by 27.4%(P<0.05),sucrose enzyme activity by 9.2%(P<0.05),urease activity by 17.7%(P<0.05)and catalase by 20.1%(P<0.05)in the inter-root soil compared to the non-root soil.The moso bamboo root system significantly increased the enzyme activity in the soil and restored the function of the heavy metal contaminated soil.(2)Compared to the control group,the height of moso bamboo decreased by 22.6%,leaf length by 25.9%,leaf width by 21.3% and basal diameter by 26.7%(P<0.05).The photochemical quenching index(q P)and non-chemical quenching index(NPQ)of moso bamboo decreased by 29.8% and 42.2% respectively(P<0.05),and the intracellular CO2 concentration and water utilisation decreased by 31.4% and 36.9% respectively(P<0.05).The activities of peroxidase(POD)and catalase(CAT)decreased by 32.9% and 22.6%(P<0.05)respectively,but did not affect superoxide dismutase(SOD)and malondialdehyde(MDA)content.It also did not affect the fibre morphology and the composition of the cell wall of moso bamboo.(3)The enrichment of heavy metals in different parts of the moso bamboo varied from root > leaf > stem > node > branch,with moso bamboo root and moso bamboo leaf being the main organs enriched in heavy metals.Above-ground and below-ground enrichment of moso bamboo under different treatments.The above-ground content of Cr,Mn,Ni,Cu,Zn and Pb was significantly greater than that of the below-ground roots,with transfer coefficients of 2.92,3.06,1.85,4.95,7.48 and 2.44 for the moso bamboo treatment groups.The results of principal component analysis showed a significant separation of principal component 1(PC1)of moso bamboo heavy metal elemental metabolism under different treatments,indicating that high concentrations of heavy metal stress significantly interfered with the mineral metabolism of moso bamboo.The results of the weighted network analysis showed that Ni was at the centre of the regulatory network of mineral metabolism and had the most significant effect on the other six heavy metals.ni showed positive correlations with Fe,Mn and Cu,and negative correlations with Cr,Pb and Cu.The results of the correlation heat map showed that four heavy metals,Mn,Zn,Ni and Fe,were significantly correlated with Ci,POD,CAT,NPQ and q P in moso bamboo.(4)Compared with the non-root soil,the heavy metal contents of Cr,Mn,Fe,Ni,Cu,Zn and Pb decreased by 52%,88%,41%,55%,52%,91% and 47% respectively(P<0.05)in the inter-root soil of the tailings area.This indicates that the three native bamboo species in the tailings area significantly reduced the content of seven heavy metals in the soil and had a remediation effect on the heavy metal contaminated soil in the tailings area.The enrichment of Cr,Mn,Ni,Cu,Zn and Pb by above-ground stems,branches,leaves and nodes of the three native bamboo species was significantly greater than that of the lower ground roots.In contrast,the high concentration of Fe may have prevented its transfer to the above-ground parts,resulting in no significant enrichment of Fe in the above-ground parts of the three native bamboo species.Native bamboo species 1 showed the highest total enrichment of Cr,native bamboo species 2 showed the highest total enrichment of Mn,Ni and Pb,and native bamboo species 3 showed the highest total enrichment of Fe,Cu and Pb.