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A simple technique for continuous measurement of time‐variable gas transfer in surface waters
Author(s) -
Tobias Craig R.,
Böhlke John Karl,
Harvey Judson W.,
Busenberg Eurybiades
Publication year - 2009
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2009.7.185
Subject(s) - biogeochemical cycle , diel vertical migration , streams , tracer , environmental science , hydrology (agriculture) , chemistry , trace gas , sparging , volume (thermodynamics) , environmental chemistry , ecology , geology , computer network , physics , geotechnical engineering , organic chemistry , quantum mechanics , computer science , nuclear physics , biology
Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating whole‐ecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error‐prone components of these models. Here we present a simple and efficient modification of the SF 6 gas tracer approach that can be used concurrently while collecting other dissolved gas samples for dissolved gas mass balance studies in streams. It consists of continuously metering SF 6 ‐saturated water directly into the stream at a low rate of flow. This approach has advantages over pulse injection of aqueous solutions or bubbling large amounts of SF 6 into the stream. By adding the SF 6 as a saturated solution, we minimize the possibility that other dissolved gas measurements are affected by sparging and/or bubble injecta. Because the SF 6 is added continuously we have a record of changing gas transfer velocity (GTV) that is contemporaneous with the sampling of other nonconservative ambient dissolved gases. Over a single diel period, a 30% variation in GTV was observed in a second‐order stream (Sugar Creek, Indiana, USA). The changing GTV could be attributed in part to changes in temperature and windspeed that occurred on hourly to diel timescales.