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Elements heavier than hydrogen or helium that are present in the atmospheresof white dwarfs with effective temperatures lower than 25,000 K, are believedto be the result of accretion. By measuring the abundances of these elementsand by assuming a steady-state accretion, we can derive the composition of theaccreted matter and infer its source. The presence of radiative levitation,however, may affect the determination of the accretion rate. We presenttime-dependent diffusion calculations that take into account radiativelevitation and accretion. The calculations are performed on C, N, O, Ne, Na,Mg, Al, Si, S, Ar, and Ca in hydrogen-rich white dwarf models with effectivetemperatures lower than 25,000 K and a gravity of log g = 8.0. We show that inthe presence of accretion, the abundance of an element supported by theradiative levitation is given by the equilibrium between the radiative andgravitational accelerations, unless the abundance predicted by the steady-stateaccretion is much greater than the abundance supported by the radiativeacceleration.

Effect of Radiative Levitation on Calculations of Accretion Rates in White Dwarfs