The Physiological And Biochemical Response Of R. Japonicum L On Fe³⁺?Co²⁺?Ni²⁺ Stress And Carbonization After Enrichment

The rapid development of modern industrial and energy industries has inevitably brought serious heavy metal pollution to the environment,which is potentially harmful to human health and the ecological environment in the long term.Bioremediation has received great attention and development in recent years,especially the phytoremediation technology has shown great potential in heavy metal pollution management.Therefore,this project uses R.japonicum L,a moss with strong resilience,as the research object to investigate the phytoremediation and plant response to the pollution of Fe³⁺,Co²⁺and Ni²⁺heavy metals in the water body.The physiological and biochemical responses of R.japonicum L in photosynthetic physiology,antioxidant physiology and metabolome level,and the enrichment ability and characteristics of heavy metals,as well as the treatment method of biomass carbonization after enrichment of heavy metals,were investigated to provide scientific basis for the elucidation of biological effects of Fe³⁺,Co²⁺and Ni²⁺polluted water bodies and biological treatment of wastewater.The main research results are as follows.1.The oxidative stress substance content of sand moss was partially increased under the stress of Fe³⁺,Co²⁺and Ni²⁺.The O₂^-content of sand moss reached the highest and significantly higher than the control(P<0.05)after high concentration of Fe³⁺(125mg/L),Co²⁺(25mg/L)and Ni²⁺(25mg/L)stress,and the Co²⁺and Ni²⁺stress concentrations were positively correlated with the O₂^-content of sand moss;while the Fe³⁺and Co²⁺stress concentrations were positively correlated with the·OH production rate was positively correlated.Both medium(25 mg/L)and high concentration of Fe³⁺stress significantly promoted the production of all oxidative stress products in sand moss.For the antioxidant enzyme system,the POD,SOD and CAT activities of sand moss were increased under low concentration(5 mg/L)Fe³⁺stress,among which the POD and CAT activities were significantly higher than the control,while the antioxidant enzyme activities of sand moss under low concentration of Co²⁺(1 mg/L)and Ni²⁺(1 mg/L)stress were lower than the control and decreased with increasing stress.Therefore,the mitigation of stress in Co²⁺and Ni²⁺stresses was mainly through the ASA-GSH cycle pathway,in which ASA and GSH concentrations and GPX activities increased with increasing stress under Co²⁺stress,and APX and GST activities also increased significantly;for Ni²⁺stress,the GSH concentration and APX,GPX and GST activities of sand moss were positively correlated with the stress concentration.Under Fe³⁺stress,the ASA,GSH concentration,GPX and GST activities of sand moss increased with the increase of stress concentration,and the APX enzyme activity also increased significantly.In general,sand moss increased antioxidant enzyme activities in response to stress at low Fe³⁺concentration(5mg/L),while ASA-GSH cycle received generally positive feedback under Fe³⁺,Co²⁺,and Ni²⁺stresses.In photosynthetic physiological studies,chlorophyll content of sand moss increased under medium and low Fe³⁺,Co²⁺,and Ni²⁺stress(P<0.05)and significantly decreased under high Fe³⁺,Co²⁺,and Ni²⁺stress(P<0.05);light energy absorption and photoelectron conversion efficiency of PSII decreased under low concentrations of Fe³⁺,Co²⁺,and Ni²⁺,and photodamage to The energy ratio of photodamage and heat dissipation part increased under high concentration of Fe³⁺,Co²⁺stress and increased the energy ratio of photochemical reaction at the same time.It showed that the PSII efficiency of sand moss decreased after Fe³⁺,Co²⁺and Ni²⁺stresses and caused damage to sand moss.Sand moss,on the other hand,alleviated the stress by increasing the energy share of photochemical reactions.In terms of ion enrichment,the enrichment of sand moss for Fe³⁺,Co²⁺and Ni²⁺increased with the increase of stress concentration,and the enrichment of Fe³⁺,Co²⁺and Ni²⁺reached 5.64 mg/g,4.13mg/L and 1.09 mg/L under high stress concentration,respectively;Fe elements had regularity in subcellular distribution,and most Fe ions were retained in the cell wall and structures outside the cell wall,and the cell boundary of sand moss was blurred under high concentration of Fe³⁺and Ni²⁺stress.2.The metabolite analysis of sand moss after 125 mg/L Fe³⁺stress identified 288 metabolites,and 114 metabolites with significant differences were screened compared with the control group,among which 11 metabolites were up-regulated and 103 metabolites were down-regulated.The up-regulated metabolites were mainly organic acid small molecules and lipid metabolites,which were distributed in the TCA cycle pathway,glycerol metabolism pathway,pyrimidine and derivative metabolism pathway and signal molecule transduction metabolism pathway;the down-regulated metabolites mainly included 29 amino acid molecules,19 sugar and derivatives,29 organic acid small molecules,9 lipid metabolites and other kinds of metabolites.Analysis of the differential metabolites by pathway enrichment algorithm showed that high concentration of Fe³⁺stress mainly affected the aminoacyl-t RNA biosynthesis pathway and ABC transporter protein metabolic pathway,and significantly inhibited most amino acid metabolic pathways,followed by sugar and derivative metabolic pathways,alkaloid synthesis and purine metabolic pathways.3.The sand moss and the sand moss loaded with Fe,Co and Ni were charred at 1000?for1.5h,and the materials were characterized by SEM,FT-IR,XRD,XPS,XRF and other methods.The results show that the sand moss biomass char has a dense mesoporous distribution of surface morphology,retains some functional oxygen-containing functional groups,and has strong chemisorption;the sand moss biomass loaded with Fe³⁺,Co²⁺,Ni²⁺has most metal ions located in the core of char structure after charring,and the loaded char has a high ratio of metal ion content,and the capacitance test results show that the different heavy metals loaded show different The capacitance test results show that different heavy metal loadings show different capacitance performance,indicating that the sand moss loaded with Fe,Co and Ni metal ions has some potential for electrochemical applications after charring.