| Autor: |
Rovelli, L., Attard, K. M., Heppell, C. M., Binley, A., Trimmer, M., Glud, R. N. |
| Předmět: |
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| Zdroj: |
Limnology & Oceanography, Methods; Oct2018, Vol. 16 Issue 10, p696-709, 14p |
| Abstrakt: |
Headwater streams are important in the carbon cycle and there is a need to better parametrize and quantify exchange of carbon‐relevant gases. Thus, we characterized variability in the gas exchange coefficient (k2) and dissolved oxygen (O2) gas transfer velocity (k) in two lowland headwaters of the River Avon (UK). The traditional one‐station open‐water method was complemented by in situ quantification of riverine sources and sinks of O2 (i.e., groundwater inflow, photosynthesis, and respiration in both the water column and benthic compartment) enabling direct hourly estimates of k2 at the reach–scale (~ 150 m) without relying on the nighttime regression method. Obtained k2 values ranged from 0.001 h−1 to 0.600 h−1. Average daytime k2 were a factor two higher than values at night, likely due to diel changes in water temperature and wind. Temperature contributed up to 46% of the variability in k on an hourly scale, but clustering temperature incrementally strengthened the statistical relationship. Our analysis suggested that k variability is aligned with dominant temperature trends rather than with short‐term changes. Similarly, wind correlation with k increased when clustering wind speeds in increments correspondent with dominant variations (1 m s−1). Time scale is thus an important consideration when resolving physical drivers of gas exchange. Mean estimates of k600 from recent parametrizations proposed for upscaling, when applied to the settings of this study, were found to be in agreement with our independent O2 budget assessment (within < 10%), adding further support to the validity of upscaling efforts aiming at quantifying large‐scale riverine gas emissions. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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