On the possibility that rotation causes latitudinal abundance variations   in stars
  The effect of rotation of a star on the distribution of chemical species in radiative zones is discussed. Gravity darkening generates a large radiative force on heavy element ions which is directed toward the equatorial plane. Taking iron as an example, it is shown that this force may produce drift velocities similar to, and larger than, the typical velocities of bulk motion due to meridional circulation. This potentially allows large chemical abundance inhomogeneities to build up across a meridian over the lifetime of the star -- particularly near the equatorial plane. This enhancement may be significantly reduced if the mass loss of the star is strongly metallicity dependent, in which case the mass-loss rate may be enhanced in the equatorial plane. 
John M. Porter (Liverpool John Moores University)