Accuracy and precision analysis of chamber-based nitrous oxide gas flux estimates.
Accuracy and precision analysis of chamber-based nitrous oxide gas flux estimates.
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基于室的一氧化二氮气体通量估计的准确性和精度分析。
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
J. Baker
中科院分区：
文献类型：
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作者：
R. Venterea;K. Spokas;J. Baker
由于固有的非线性时间序列数据，基于室的土壤到大气一氧化二氮 (N 2 O) 气体通量的估计往往会低估实际排放率。理论上，可以通过调整测量条件以减少非线性和/或通过使用考虑所谓“室效应”的通量计算（FC）方案来最小化这种限制。当前的研究利用气体传输理论和随机分析来评估特定土壤和室内条件下 N 2 O 通量测定的准确性和精密度。分析表明，为提高通量估计的绝对精度而采取的措施，包括更短的部署时间、更大的腔室高度和非线性 FC 方案，也会增加通量估计的方差，其程度取决于与采样技术和分析仪器性能相关的误差。在通量没有任何实际变化的情况下，这些效应可能会产生 3% 至 70% 的变化系数，具体取决于测量条件。研究还表明，非线性 FC 方案容易产生正偏分布。这些影响降低了 N 2 O 通量估计的可信度，并抑制了对实验因素引起的差异的检测。一般来说，线性 FC 方案更有可能检测通量的相对差异，尽管在绝对值上不如非线性方案准确。这里描述的技术已被编入一个可访问的基于电子表格的工具中，用于评估特定测量条件下的准确性和精度权衡。
Chamber-based estimates ofsoil-to-atmosphere nitrous oxide (N 2 O) gas flux tend to underestimate actual emission rates due to inherently nonlinear time series data. In theory, this limitation can be minimized by adjusting measurement conditions to reduce nonlinearity and/or by using flux-calculation (FC) schemes that account for the so-called "chamber effect." The current study utilizes gas transport theory and stochastic analysis to evaluate accuracy and precision of N 2 O flux determinations under specific soil and chamber conditions. The analysis demonstrates that measures taken to increase the absolute accuracy of flux estimates, including shorter deployment times, larger chamber heights, and nonlinear FC schemes, will also increase the variance in flux estimates to an extent that depends on errors associated with sampling techniques and analytical instrument performance. These effects, in the absence of any actual variation in fluxes, can generate coefficients of variation ranging from 3 to 70% depending on measurement conditions. It is also shown that nonlinear FC schemes are prone to generating positively skewed distributions. These effects decrease confidence in N 2 O flux estimates and inhibit the detection of differences arising from experimental factors. In general, a linear FC scheme will be more likely to detect relative differences in fluxes, although less accurate in absolute terms than nonlinear schemes. The techniques described here have been codified into an accessible spreadsheet-based tool for evaluating accuracy and precision trade-offs under specific measurement conditions.