[en] A self-consistent theory is presented for particle flows in the flux surface, radial particle fluxes and the radial electric field in a tokamak. The effects of beam-impurity momentum exchange, radial transfer of toroidal momentum, and the poloidal variation in density and potential which ensue when v/sub phi/ approx. = v/sub th/ are treated - the interaction among these effects is non-linear. Model problem predictions based on the theory indicate enhanced inward impurity transport with strong counter-injection and outward impurity transport with strong co-injection of neutral beams