  A process specific to the dynamics of the heavy impurities in turbulent
tokamak plasmas is found and analysed. We show that the parallel stochastic
acceleration is strongly coupled to the perpendicular transport and generates a
radial pinch velocity. The interaction is produced with the hidden drifts, a
quasi-coherent component of the motion that consists of a pair of average
radial velocities in opposite directions. The parallel acceleration breaks this
symmetry and yields a radial average velocity that can be in the inward or
outward direction. The transport of the tungsten ions in three-dimensional
turbulence is analysed in the frame of a test particle model using numerical
simulations. The results show that the acceleration induced pinch can be
important for W impurity transport in present days tokamaks and in ITER.
