设施菜田土壤氮磷淋失对镁改性生物炭施用的响应OA

To address leaching pollution from excessive nitrogen(N)and phosphorus(P)accumulation in greenhouse vegetable soil,this study prepared unmodified biochars(MB from corn stover,BB from bamboo)and Mg-modified biochars(Mg-MB,Mg-BB)at 550 ℃.Batch adsorption experiments,soil column leaching experiments,and characterizations(Scanning electron microscope-energy dispersive spectroscppy,Fourier transform infrared spectroscopy)were conducted to explore the adsorption performance of Mg-modified biochars for coexisting N and P,and their mitigation effect on N and P leaching in greenhouse vegetable soil.Results showed that Mg modification did not destroy the biochar carbon skeleton,but introduced Mg—O bonds(620 cm-1)and enhanced the intensity of oxygen-containing functional groups(—OH,—COOH).Adsorption experiments indicated that all biochars except BB treatment fitted the Langmuir model,with better fitting to the pseudo-second-order kinetic model,suggesting monolayer homogeneous chemisorption as the dominant mechanism.Mg modification increased the maximum theoretical adsorption capacity of biochars for NO3-:Mg-MB and Mg-BB treatments increased by 81.18％and 7.77％,compared with MB and BB treatments,respectively,with Mg-BB treatment showing the highest NO3-adsorption.For PO43-,the maximum adsorption capacities of Mg-MB and Mg-BB treatments were 1.21 and 2.09 times those of MB and BB treatments,respectively,while MB and Mg-MB treatments had higher P adsorption than BB and Mg-BB treatments.In soil column leaching experiments,all biochar treatments significantly reduced N and P leaching compared to treatment without biochar:Mg-BB treatment had the best N leaching mitigation(44.36％reduction),and Mg-MB treatment had the best P leaching mitigation(21.52％reduction).Mg-modified biochars showed lower N and P leaching than their unmodified biochars.Specifically,Mg-BB treatment significantly reduced the proportions of dissolved inorganic nitrogen,dissolved organic nitrogen,and nitrate nitrogen in leachate by 17.24％,10.61％,and 12.88％,compared with BB treatment;Mg-MB treatment reduced the proportions of soluble reactive phosphorus and soluble organic phosphorus by 6.81％and 3.66％,compared with MB treatment.In conclusion,Mg modification enhances adsorption capacity of biochars for coexisting N and P,with feedstock-dependent functional differentiation:Mg-BB treatment is more suitable for N leaching mitigation,while Mg-MB treatment is better for P leaching mitigation.This provided a basis for targeted material selection in nutrient management and environmental risk control of greenhouse vegetable soil.