Turbulent mixing and eddy diffusion effectively maintain a uniform atmospheric composition within the homosphere up to the turbopause, where molecular diffusion begins to dominate.
The claim describes standard atmospheric science: the region below the turbopause (the homosphere) maintains a constant relative chemical composition driven by turbulent mixing and eddy diffusion. Retrieved papers 0, 1, and 6 explicitly confirm this fundamental mechanism and the transition to molecular diffusion at the turbopause boundary.