Study On Calculation Method Of Soil Carbon Flux Based On Maxwell-stefan Diffusion Model

Soil science research is an important topic in current ecological environment research.The carbon flux of soil respiration reflects the ability of the region to absorb carbon dioxide and the activity of soil.It is of great significance for the study of ecology and agriculture.At present,the carbon flux monitoring method used in scientific research is mainly dynamic gas chamber method,which has the characteristics of convenient carrying,real-time data acquisition and high precision,but there are also some shortcomings that prevent continuous monitoring for a long time.To solve this problem,this study proposes the Maxwell-Stefan diffusion model and designs the open gas chamber as the main body of the monitoring instrument,and applies the diffusion gradient theory to the monitoring of soil respiration.Through the simulation experiment and the results of field monitoring,the following research results were obtained:(1)There is mass conservation in the free convection diffusion process of soil gas in an open gas chamber.By modeling the linear diffusion phase and the dynamic equilibrium phase,and deriving the equilibrium formula,the relationship between soil respiration rate and gas flow velocity and CO2 gas concentration distribution is obtained.It is theoretically verified that open air chambers are feasible for measuring soil respiration rate.(2)In the simulation and measured results,the carbon dioxide concentration of each layer sensor shows a stable concentration gradient after steady state,which indicates that the application of Maxwell-Stefan diffusion theory in the field is feasible.(3)The open-type gas chamber method proposes to convert the conventional equipment based on the time-varying rate of carbon dioxide into a rate-based change rate,and eliminates the suppression of soil respiration by the closed air chamber,so that long-term sustainable monitoring can be performed.(4)Through long-term monitoring experiments and comparison with the monitoring results of Li-8100,the results similar to Li-8100 were obtained,which proved that the monitor proposed by the research institute can achieve accurate measurement of carbon flux.This study not only provides theoretical basis and practical experience for open soil respiration monitors,but also provides an innovative and practical method for solving the problem oflong-term accurate monitoring of soil carbon flux.