Measurement of gas-exchange rate in streams by the oxygen–carbon method
Measurement of gas-exchange rate in streams by the oxygen–carbon method
复制标题
用氧碳法测量流中的气体交换率
作者：
R. Pennington;A. Argerich;R. Haggerty
河流与大气之间的气体交换速率是衡量河流生态过程和河流中碳处理的必要条件。目前的方法包括经验关系的水力学，直接注入示踪气体，和建模的基础上O2或C的昼夜曲线。所有现有的方法都有优点和缺点，大多数仅限于点测量或无法测量汇率的昼夜变化。研究人员继续寻找更好的技术，特别是对于气体交换率高、初级生产力低的陡峭溪流。我们提出了O2−C（OC）方法，通过同时测量O2和溶解无机C（DIC）来计算气体交换速率。气体交换率通过求解O2和DIC的组合流传输方程来计算。输出是以与输入O2和C数据相同的采样频率的通气率的时间序列。在美国俄勒冈州的一条四级山地河流中的现场试验表明，该方法适用于下游气体浓度梯度和饱和度亏损较大的河流河段。调整至17°C（3.25/h）的平均模拟通气速率与直接气体注入的3.22/h值一致。用模拟通气率（−1.69 g O2 m−2 d−1）计算的生态系统净生产量与直接注气（−1.60 g O2 m−2 d−1）获得的结果一致。该模型假设呼吸商为常数，但结果表明呼吸商可能随时间变化。敏感性分析表明，OC法的应用仅限于O2和CO2浓度变化≥ 1.4 μmol/L，O2和CO2饱和度亏损≤ 1.4 μmol/L的河段。OC方法的初步应用表明，它可能是有用的从业人员有兴趣在连续测量气体交换率。
The gas-exchange rate between streams and the atmosphere is needed to measure in-stream ecological processes and C processing in rivers and streams. Current methods include empirical relationships to hydraulics, direct injection of a tracer gas, and modeling based on O2 or C diel curves. All existing methods have strengths and drawbacks and most are limited to point measurements or are unable to measure diel variation in exchange rate. Researchers continue to search for better techniques, particularly for steep streams with high rates of gas exchange and low primary productivity. We present the O2−C (OC) method for calculating gas-exchange rates via simultaneous measurement of O2 and dissolved inorganic C (DIC). Gas-exchange rates are calculated by solving the combined stream transport equation for O2 and DIC. The output is a time-series of aeration rates at the same sampling frequency as the input O2 and C data. Field tests in a 4th-order montane stream in Oregon, USA, indicate that the method is suitable for stream reaches with high downstream gas-concentration gradients and saturation deficits. The mean modeled aeration rate adjusted to 17°C (3.25/h) agreed well with the value of 3.22/h from direct gas injection. Net ecosystem production calculated with the modeled aeration rate (−1.69 g O2 m−2 d−1) was consistent with the result obtained with direct gas injection (−1.60 g O2 m−2 d−1). An assumption of the model is a constant respiration quotient, but results indicated that the respiration quotient may be time variable. Sensitivity analysis indicated that application of the OC method is limited to reaches with a suitable change in combined O2 and CO2 concentration ≥ ∼4 μmol/L and combined O2 and CO2 saturation deficits ≈ 4 μmol/L, characteristic of smaller gaining streams. Preliminary application of the OC method indicates it could be useful to practitioners interested in continuous measurement of gas-exchange rates.
影响因子：
2.7
作者：
Demars, Benoit O. L.;Thompson, Joshua;Manson, J. Russell
通讯作者：
Manson, J. Russell
影响因子：
11.6
作者：
Perkins, Daniel M.;Yvon-Durocher, Gabriel;Woodward, Guy
通讯作者：
Woodward, Guy