  Recent solar abundance analyses (Asplund et al. 2004; Lodders 2003) revise
downward the abundances of C, N, O, Ne, and Ar, which reduces the solar
photospheric Z/X to 0.017, and Z to ~0.013. Solar models evolved with standard
opacities and diffusion treatment using these new abundances give poor
agreement with helioseismic inferences for sound speed profile, convection zone
helium abundance, and convection zone depth. Here we present helioseismic
results for evolved solar models with these reduced photospheric abundances,
trying varying diffusion treatments. We compare results for models with no
diffusion, enhanced thermal diffusion, and enhanced diffusion of C, N, O, Ne,
and Mg only. We find that while each of these models provides some improvements
compared to a solar model evolved with the new abundances and standard physics,
none restores the good agreement with helioseismology attained using the
earlier abundances of, e.g., Grevesse & Sauval (1998). We suggest that opacity
increases of about 20% for conditions below the convection zone, or the
possibility of accretion of lower-Z material at the surface as the sun arrived
at the main sequence, should be investigated to restore agreement. In addition,
the new abundance determinations should be re-considered, as, if they are
correct, it will be difficult to reconcile solar models with helioseismic
results.
