Technical note: drifting versus anchored flux chambers for measuring greenhouse gas emissions from running waters

[摘要] Stream networks have recently been discovered to be major but poorly constrainednatural greenhouse gas (GHG) sources. A fundamental problem is that severalmeasurement approaches have been used without cross-comparisons. Fluxchambers represent a potentially powerful methodological approach if robustand reliable ways to use chambers on running water can be defined. Here wecompare the use of anchored and freely drifting chambers on various streamswith different flow velocities. The study clearly shows that (1) anchoredchambers enhance turbulence under the chambers and thus elevate fluxes,(2) drifting chambers have a very small impact on the water turbulence under thechamber and thus generate more reliable fluxes, (3) the bias of the anchoredchambers greatly depends on chamber design and sampling conditions, and(4) there is a promising method to reduce the bias from anchored chambers byusing a flexible plastic foil collar to seal the chambers to the water surface, rather than havingrigid chamber walls penetrating into the water. Altogether, these resultsprovide novel guidance on how to apply flux chambers in running water, whichwill have important consequences for measurements to constrain the globalGHG balances.

[学科分类] 地球化学与岩石