  We use the bailout embeddings of three-dimensional volume-preserving maps to
study qualitatively the dy- namics of small spherical neutrally buoyant
impurities suspended in a time-periodic incompressible fluid flow. The
accumulation of impurities in tubular vortical structures, the detachment of
particles from fluid trajectories near hyperbolic invariant lines, and the
formation of nontrivial three-dimensional structures in the distribution of
particles are predicted.
