Molecular diffusion of CF3SF5 in pure water and artificial seawater

Abstract

We have experimentally determined the diffusion coefficient for trifluoromethyl sulfur 1 pentafluoride (CF 3 SF 5) in pure water and artificial seawater over a temperature range of-2.0 ºC 2 to 30.0 ºC. A working gas standard containing known concentrations of CF 3 SF 5 and sulfur 3 hexafluoride (SF 6) was prepared. The working standard was allowed to diffuse across a water 4 barrier, stabilized with agar gel, and the diffused gas was swept into a gas chromatograph with an 5 electron-capture detector to measure the resulting gas mixing ratio. The mixing ratios for both 6 CF 3 SF 5 and SF 6 were measured to determine the diffusivity for each species. The diffusion 7 coefficient for SF 6 was determined during these experiments as a check against existing literature 8 values and to validate our experimental setup. The experimental data were fit to the Arrhenius 9 equation to yield the following equations and 10 , where R is the gas constant in units of kilojoules per mole per kelvin 11 and T is the temperature in kelvin. At the mean temperature of the ocean, 18 ºC, 12 and cm 2 /s. The diffusion coefficients for 13 SF 6 matched the literature data within 4.3% for all temperatures.

Lagrangian Geography of the Deep Gulf of Mexico

“…17 show snapshots of the evolution of a narrow Gaussian (normalized to represent a probability density) initially near the chemical tracer injection site for two diffusivity choices. The middle panels show the case of pure stirring since the simulation uses a diffusivity of 7 3 10 210 m 2 s 21 , a molecular value for CF 3 SF 5 at mean ocean temperature estimated by Vardner and Loose (2016). The bottom panels use an eddy diffusivity of 50 m 2 s 21 , estimated by an anonymous reviewer from the product of a characteristic length of 5 km (estimated from the resolution of the RAFOS floats' positions) and a characteristic velocity of 0.1 m s 21 [a value that can be considered typical and consistent with diffusion diagrams of Okubo (1971) for the surface ocean and arguably also useful for the quite energetic deep GoM].…”