As discussed by Jenkins (2003), determinations of elemental abundances from interstellar absorption line observations may require estimation of the fraction in unobserved ionization states, such as Na II, K II, or Ca III. Such estimates require knowledge of the rates for ionization and recombination processes. Neutral or negatively-charged dust grains provide a pathway for ion neutralization that for some cases can be faster than ordinary radiative recombination with free electrons (Weingartner & Draine 2001).