Management of arsenic and selenium present in fly ash leachate at disposal facilities is a significant environmental concern. Attenuation of arsenic (III and V) and selenium (IV and VI) by 18 soils collected from 3 ash disposal sites was investigated in batch and column studies. Adsorption isotherms were measured for each species from aqueous solutions of CaCl₂, CaSO₄, KCl, and K₂SO₄ as a function of pH. For a given soil, the magnitude of adsorption was as follows: As(V) > Se(IV) > As(III) > Se(VI). However, the oxide content, which is also well reflected in % clay for the soils in this study, and pH resulted in the best correlation to adsorption magnitude. Adsorption decreased with increasing pH, likely due to same charge repulsion between oxy anions and deprotonated soil surface functional groups. Adsorption was affected some by the background electrolyte with increasing calcium concentrations resulting in an increase in adsorption while sulfate suppressed adsorption. For the column studies, As (III and V) and Se (IV and VI) spiked 1 mM CaSO₄ solutions were pumped through soil columns at site-specific pore water velocities and column effluent was monitored for pH and concentration of each species for several hundred pore volumes. The order of elution followed batch isotherm trends; however, the retardation factor (R) calculated from batch isotherm were not always in good agreement with column breakthrough. Column sections were extracted with 1 mM CaSO₄ (desorption isotherm) and 0.1M/0.1M NaH₂PO₄/Na₂HPO₄ followed by a HNO₃-H₂O₂ digestion. Extraction data for As(V and VI) and Se(IV and VI) indicated that precipitation and oxidation reactions that were not significant in the batch isotherm studies were the primary reasons for lack of agreement between predicted and observed R values.