Boundary condition for liquid-gas interface if there is mass transfer across it
 

Suppose, Air is flowing over a pool. And the flow is laminar. Now water is being evaporated from free liquid surface (e.i. liquid gas interface). So, for the mass transfer across the interface, the velocity boundary layer will be thickened. Right? In that case what would be the boundary condition for the momentum equation at the interface? (Say I know my species production rate and I am solving species transfer equation too)