Study On The Adsorption Of Soil EDNA On Cornstalk Biochar And Its Influencing Factors

Environmental DNA（eDNA）is the sum of DNA from different biological sources in the environment,which can last for months.The eDNA mainly comes from the litters,metabolites and dead residues of organisms.The environmental and ecological effects of eDNA have been widely concerned.For example,eDNA can monitor the invasion of alien biological species,indicate the impact of environmental pollutants on the ecosystem,and promote the resistance of plant rhizosphere to the erosion of pathogenic bacteria.It needs to be particularly pointed out that,as an important component of eDNA,the intergenerational transmission and horizontal transfer of Antibiotics Resistance Genes（ARGs）in the microbial community accelerate its diffusion in the environment,leading to the emergence of a large number of drug-resistant bacteria.The risks to the environment and human health are incalculable.As an environment-friendly material,biochar has been widely used in soil carbon sequestration,improvement and pollution control.Due to its huge surface area,abundant functional groups and porous structure,biochar has shown excellent adsorption capacity for all kinds of organic matter,including antibiotics and pesticides.Previous studies have shown that biochar has a strong adsorption effect on organic matter.As an important organic matter in the soil environment,eDNA has an ecological function that cannot be ignored.The application of biochar will affect the ecological function and environmental application of soil eDNA,and even change the migration behavior of resistance genes in the soil.In this study,the properties of biochar prepared at four pyrolysis temperatures（300℃,400℃,500℃,600℃）were compared,and the adsorption of eDNA by biochar and its influencing factors were studied.The results can provide a theoretical basis for the effect of biochar application on soil eDNA and its ecological function.The results show that:（1）The properties of biochar prepared at different pyrolysis temperatures differ greatly.With the increase of pyrolysis temperature,the surface of biochar becomes rougher,the specific surface area and pore volume gradually increase,and the proportion of mesopores（2-50 nm）gradually increases from 40%to 73%.The polarity of biochar decreases gradually with the temperature,and the functional groups such as hydroxy-OH and aliphatic-CH decrease gradually,and the carbon structure becomes more unsaturated.（2）The adsorption kinetics and the final amount of DNA were significantly different between low temperature and high temperature biochar.The low temperature biochar had a higher adsorption rate,and the pseudo-secondary adsorption rate constant K of low temperature biochar was about 10 times that of high temperature biochar.The final adsorption capacity of high-temperature biochar is higher,and the adsorption capacity of high-temperature biochar can reach 4 mg·g-1,while that of low-temperature biochar is generally around 2 mg·g-1.The high temperature biochar has a large specific surface area,and the biochar pore size is more conducive to DNA adsorption in the pore.However,the surface of low temperature biochar has more oxygen-containing functional groups,which is conducive to the improvement of initial adsorption rate,but it also has a higher negative charge density and a higher electrostatic repulsion force with DNA,which is not conducive to the continuous adsorption.（3）The adsorption behavior of DNA was affected by different ambient temperatures.The adsorption rate of biochar was the highest at 4℃,which indicated that low temperature was beneficial to increase the adsorption rate.The adsorption capacity was the highest at 20℃,which was because the increase of temperature intensified the surface diffusion of DNA,which was conducive to the adsorption,but the further increase of temperature was not conducive to the further increase of the adsorption capacity.（4）The higher the valence state of metal ions,the more obvious the promotion of biochar adsorption DNA system;Zn²⁺,Mn2+and Mg²⁺,which are both divalent metal ions,show different adsorption promotion effects.Zn²⁺tends to bind to DNA base,increasing the number of DNA adsorption sites to promote adsorption,while Mg²⁺tends to bind to DNA phosphate group,making limited contribution to the adsorption system.Mn²⁺adsorption promotion effects are between them.