基于Maxwell-Stefan扩散模型的土壤碳通量计算方法研究

目前土壤碳通量的监测方法存在一定的缺点,导致无法长时间精确监测。针对这一问题,提出用Maxwell-Stefan扩散模型进行碳通量的计算,并建立开放型气室模型进行仿真研究。根据仿真程序生成的不同高度的浓度时间序列,基于Maxwell-Stefan扩散模型计算二氧化碳通量值,将计算结果与仿真设定值进行对比。其中,设定通量为0.5 μmol·m^-2·s^-1时,计算结果为0.547 μmol·m^-2·s^-1;设定通量为1.0 μmol·m^-2·s^-1时,计算结果为0.969 μmol·m^-2·s^-1;设定通量为2.0 μmol·m^-2·s^-1时,计算结果为2.122 μmol·m^-2·s^-1。运用该算法计算的误差均在10%以内。另外,与Fick扩散模型的计算结果进行对比,在3组实验下,Maxwell-Stefan模型计算所得的通量值都更加接近于设定值。本研究的结果表明,Maxwell-Stefan扩散模型适用于土壤呼吸碳通量的计算,并且具有较好的计算结果,从理论上验证了该模型用于土壤碳通量计算的可行性和准确性。

Study on calculation method of soil carbon flux based on Maxwell-Stefan diffusion model

There are certain disadvantages in the monitoring methods of soil carbon flux, which led to inability to accurately monitor for long period. To solve this problem, the present study proposed a method to calculate the carbon flux by using Maxwell-Stefan diffusion model, and establish an open-chamber in order for simulation. According to the multiple altitude of concentration, the carbon flux was calculated based on Maxwell-Stefan model, and was compared with the simulation settings. The calculated result was 0.547 μmol·m^-2·s^-1 when the set flux was 0.5μmol·m^-2·s^-1, the calculated result was 0.969 μmol·m^-2·s^-1 when the set flux was 1.0 μmol·m^-2·s^-1, and the calculated result was 2.122 μmol·m^-2·s^-1 when the set flux was 2.0 μmol·m^-2·s^-1. The error calculated by this method was less than 10%. In addition, compared with the calculation results of the Fick diffusion mode, the flux values calculated by the Maxwell-Stefan model were closer to the set values in three experiments. The experimental results proved that Maxwell-Stefan model was appropriate to calculate the carbon fluxes of soil respiration and it had favourable accuracy. The present study verified the feasibility and accuracy of the Maxwell-Stefan model in calculating soil carbon flux theoretically.