Gas Transfer in Lakes, Estuaries, and Oceans

The influence of wind is predominant in determining the liquid film coefficient for lakes, reservoirs, oceans, and many estuaries. Wind creates a shear on the water surface and generates turbulence below and on the water surface. Thus, this section deals with the measurement and prediction of the wind influence on liquid film coefficient. 

The opportunistic measurement techniques generally used are absorption and Rn disequilibrium (Asher and Wanninkhofi 1998). First, there is an estimate of a long-term ( 1,000 years) global gas transfer coefficient of = 6 x 10 m/s, developed by assuming steady state between pre-1950 radioactive decay in the oceans and absorption from the atmosphere (Broecker and Peng, 1982). In addition, nuclear testing since 1950 has increased concentration in the atmosphere. Thanks 

By contrast, the gas transfer estimates utilizing Rn measurements assumes steady state between Rn production from radioactive decay of nonvolatile Rd and gas transfer with the atmosphere. This assumption is possible because Rn has a half-life of only 3.8 days, so accumulation and lateral ocean fluxes of Rn is assumed to be minimal. Again, a potential problem is the active, versus inactive layer of the ocean in this case, the mixed layer depth that may change during an experiment. 

Measurement of Wind Influence with Deliberate Tracers 

Batch Technique. As with river reaeration measurements, tracers can also be put into lakes, estuaries, and oceans to measure the influence of wind on liquid film coefficient. If we have a volatile tracer in a lake with a well-established mixed layer, for example, we can apply the same batch reactor equation from Section 6.A, as though we had a well-mixed tank  

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