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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >An open chamber system for measuring soil surface CO2 efflux: Analysis of error sources related to the chamber system
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An open chamber system for measuring soil surface CO2 efflux: Analysis of error sources related to the chamber system

机译：用于测量土壤表面CO2排放量的开放式气室系统：与气室系统相关的误差源分析

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An open dynamic chamber is a widely used method for soil CO2 efflux measurements. However, any uncontrolled air flow between the inside and outside of the chamber that is created by differences between the inflow and outflow rates can cause errors in soil CO2 efflux measurements. Estimates of these errors are reported here. A system was constructed in which compensation air of known CO2 concentration was introduced into the chamber and the CO2 concentration was measured in the outflow. The flows of air into and out of the chamber were controlled by two separate mass flow controllers, and the pressure difference between the chamber and the ambient air was measured. When the inflow was larger than the outflow, the measured efflux decreased, whereas when the inflow was smaller than the outflow, the efflux increased. With low fluxes this error was statistically significant when the difference between the flow rates was > 30%. The difference between flow rates had a larger effect on efflux rates during high efflux than during low efflux. The effect of air mixing inside the chamber on the reliability of the efflux measurement was tested. Without sufficient mixing it was not possible to get stable efflux readings with this type of chamber technique. The open chamber measurements described here were also compared to closed static measurements based on syringe samples taken manually from the chamber. On average the CO2 efflux values measured with closed static technique were 11% lower than those measured with open dynamic method. [References: 22]
机译：开放式动态腔室是用于土壤CO2流量测量的广泛使用的方法。但是，由于流入和流出速率之间的差异而导致的腔室内外之间任何不受控制的空气流动都可能导致土壤CO2外流测量的误差。这些错误的估计值在此处报告。构造了一个系统，在该系统中，将已知CO2浓度的补偿空气引入室中，并测量流出物中的CO2浓度。流入和流出腔室的空气流由两个独立的质量流量控制器控制，并测量了腔室与周围空气之间的压力差。当流入量大于流出量时，测得的流出量减少，而当流入量小于流出量时，流出量增加。对于低通量，当流速之间的差异> 30％时，此误差在统计上是显着的。流速之间的差异对高排出量的影响比对低排出量的影响大。测试了腔室内空气混合对流出测量的可靠性的影响。如果没有充分混合，则使用这种类型的腔室技术将无法获得稳定的外排读数。还基于手动从腔室获取的注射器样品，将此处描述的开放腔室测量值与封闭静态测量值进行了比较。平均而言，采用封闭式静态技术测得的CO2排放量比采用开放式动态方法测得的CO2排放量低11％。 [参考：22]

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