Table 2. Examples of Results from Studies Comparing k₆₀₀ for CO₂ and CH₄ in Order of Lower to Higher k_600CO2/k_600CH4 Ratios^a.

source	systems	Caq method		k600 (m d–1)
		CO2	CH4	CO2		CH4		CO2/CH4
				min	max	min	max
McGinnis et al.18	temperate lake	Eq	Eq	1.97	7.2	3.7	22	0.4
Paranaíba et al.6	three tropical reservoirs	Eq	Eq	0.1	7.9	0.2	19.1	0.4
Prairie and del Giorgio13	boreal reservoir and lakes	Eq	Hs	0.1	9.3	0.1	25	0.43
Rantakari et al.19	two boreal lakes	Hs	Hs	0.5	3.4	1.1	14.5	0.56
Rosentreter et al.20	six mangrove estuaries	Eq	Eq	1	24	1	28	0.83
Beaulieu et al.5	temperate river	Hs	Hs	0.2	13.7	0.4	16.8	< 1
Guérin et al.4	tropical reservoir	Hs	Hs	0.05	1.9	0.1	2.2	1.16
This study	four boreal lakes	Hs, Eqb	Hs	0.1	2.4	0.1	2	1.68
Rosentreter et al.7	mangrove river estuary	Eq	Hs	0.3	48	0.02	16	2.78

^aEq and Hs denote measurements with flow through equilibrator and headspace extraction techniques, respectively, for surface water concentrations. The equilibrated chambers technique includes headspace extraction in floating chambers allowed to equilibrate.

^bEquilibrated chambers were used in 21 of the samples from OBJ, and headspace extraction was used in the remaining 11 samples from OBJ and in SOR, BOL, and SOD.