Effects Of Fe-Mn Oxide-modified Biochar On Wheat Growth And Quality In PAEs-contaminated Soil

The pollution of phthalate esters(PAEs)in farmland soil is becoming more and more serious.PAEs not only has a negative impact on the growth of crops,but also can enter the human body through the food chain,posing a potential threat to human health.Therefore,it is urgent to develop effective methods to reduce the accumulation of PAEs in crops and achieve food safety.In this paper,iron manganese oxide modified biochar(FMBC)was prepared by impregnation and sintering from corn straw pyrolysis biochar(BC).The effects of two biochar materials on photosynthesis,biomass,quality enzyme activity,accumulation of PAEs in wheat tissues and grain quality of wheat under DBP or DEHP stress were studied by pot experiment.The main results are as follows(1)Compared with DBP and DEHP contaminated soil(control),BC and FMBC increased photosynthetic rate,transpiration rate,intercellular CO₂concentration and stomatal conductance at booting stage,and the maximum photochemical efficiency(Fv/F_M),actual photochemical quantum rate(?)and electron transfer rate(ETR)of fluorescence parameters also increased.The results showed that the application of BC and FMBC promoted the photosynthesis of wheat in DBP and DEHP contaminated soil,promoted the synthesis of organic matter and increased the biomass of wheat.This may be due to the decrease of PAEs uptake,which reduced the toxicity of PAEs to wheat.(2)Compared with the control,DBP and DEHP contents in roots,leaves and grains decreased significantly with the increase of BC and FMBC(P<0.05).After BC application,DBP and DEHP contents in wheat grains decreased by 2.2%-44.5%and2.02%-43.6%,respectively.After FMBC application,DBP and DEHP contents in wheat grains decreased by 19.9%-74.3%and 22.9%-73.9%,respectively,indicating that BC and FMBC had a good effect on reducing PAEs absorption by wheat.The decrease of FMBC was more obvious.(3)At booting stage,the activities of glutamic pyruvate transaminase(GPT)and glutamine synthetase(GS)in leaves and granule bound starch synthase(GBSS),soluble starch synthase(SSS)and ADP-glucose pyrophosphorylase(AGP)in grains of BC and FMBC treatments were significantly increased(P<0.05).The results showed that the application of BC and FMBC promoted wheat quality synthesis,and the effect of FMBC was more obvious than that of BC.It was confirmed by molecular docking that1)the ester group on PAEs can form hydrogen bond with the residue on GBSS;2)PAEs can combine with the residue on GBSS through hydrophobic interaction due to its aromatic ring structure and poor water solubility.These two interactions will block the entry of the substrate or occupy the binding sites of the reactants,and ultimately inhibit the activity of GBSS.(4)The application of BC and FMBC significantly increased amylopectin,amylose,soluble protein content,mineral element content(Fe,Mn,K and Ca)(P<0.05),and amino acid content increased.In DBP contaminated soil,with the increase of BC and FMBC,the amylose content of wheat grain increased by 2.3%-30.0%and 12.8%-50.6%compared with the control;in DEHP soil,the amylose content of wheat grain increased by 2.6%-18.0%and 4.1%-40.8%.The results showed that BC and FMBC reduced the absorption of PAEs and increased the activities of enzymes related to starch and protein formation,thus improving the quality of wheat.The addition of BC and FMBC increased the content of mineral elements needed for plant growth in soil,which provided more nutrition for plants.The results showed that compared with BC treatment,the addition of FMBC significantly improved the photosynthesis,biomass,PAEs residue and grain quality of wheat under PAEs pollution.It indicated that FMBC was a good soil remediation material.