| Due to the unreasonable use of pesticides,it often results in some pesticide residues and harm to subsequent crops.Biochar is an ideal soil remediation agent for contaminated farmland,which can improve the soil and reduce the effectiveness of pollutants.It has recently been discovered that the aging of biochar in the soil will cause changes in its physical and chemical properties and its ability to adsorb pollutants,thereby affecting its environmental application value.Therefore,it is of great significance to study the changes in the aging process of biochar and its influence on the adsorption capacity of pollutants.In this experiment,corn stalk biochar was used as the research object to study the changes in its surface characteristics and the physical and chemical properties of biochar-soil during its natural aging process,as well as the changes in aging biochar and the adsorption characteristics of biochar-soil to monosulfuron-ester during the same period.conclusion as below:（1）Aging changes the properties of biochar.The characterization of the aged biochar found that the biochar released organic matter into the soil environment at the early stage of aging,which increased the specific surface area of ??the biochar from 22.81 m2·g-1 to 55.16 m2·g-1,and the adsorption sites increased,as the aging time increased,The pore structure is destroyed.Elemental analysis and XPS analysis show that biochar aging is a gradual process from the surface to the inside.During the aging process,the carbon content decreases from 77.70% to 72.73%,and the nitrogen and oxygen elements increase from 1.99% and 15.40% to 5.71% and 5.71% respectively.18.19%,surface polarity and hydrophilicity increased.The results of nuclear magnetic resonance and Fourier transform infrared spectroscopy show that aliphatic substances are easily degraded during the aging process,and a large number of oxygen-containing functional groups（-OH and-C-O-C-,etc.）are generated.The adsorption test showed that the adsorption of monopyrimsulfonate by biochar conformed to quasi-second-order kinetic adsorption and Freundlich,indicating that it was mainly chemical adsorption,and the adsorption capacity first increased and then decreased,and reached the maximum in 200 d.（2）The application of biochar into the soil can improve the physical and chemical properties of the soil and increase the adsorption of the monopyrisulfonate in the soil.With the aging of biochar,the physical and chemical properties of biochar-soil are constantly changing.For example,the organic carbon content of C3 treatment increased by 12.63% compared with that of 10 d at 200 d,and the cation exchange capacity reached the maximum at 10 d,and then gradually decreased,and soil bulk density gradually increased during the aging process.（3）The adsorption of biochar-soil to monopyrimsulfonate is physical adsorption,diffusion is the main process that restricts the adsorption of monopyrimsulfonate by biochar-soil,and pore filling may be the main adsorption mechanism.Aging will affect the adsorption of biochar-soil on monopyrisulfone esters,similar to the effect of aging on the adsorption of monosulfonyl esters by biochar,and both reach the maximum at 200 d,which is related to the changes in biochar-soil organic matter content and soil particle surface structure related.（4）By comparing the adsorption of biochar and biochar-soil to monosulfuron-ester,the adsorption capacity changes in the same way,and the adsorption capacity of biochar-soil to monosulfuron-ester is less than that of the same mass of biochar and soil.The adsorption capacity of monopyrimsulfonate.In summary,biochar can significantly improve the physical and chemical properties of soil and increase soil adsorption of monosulfuron-ester.However,the aging of biochar in the soil will cause changes in its surface characteristics and the physical and chemical properties of biochar-soil,which in turn affects Absorption capacity of monopyrimsulfonate by itself and biochar-soil. |
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