The problem of the characterization of a conservative mass transfer is studied in the case of a system where the hydrodynamic. conditions may vary. This approach is a "system analysis" refering to the space occupatcd by the mass during its transfer. A transformation model of impulse responses, determined from tracer test in transient state, permits to obtain the response in time-concentrations of a system from an input of several injected masses. The transfonnation method can be applied both in non stationary and linear systems. Il has to be employed when the space occupated by the mass during its transfer and the hydrodynamic conditions of the system are independent. For constant volume, the applications in columns in a laboratory show the limits of the method according to phenomena of tracer density in a tube. In chalky granular medium, the non linear phenomena of the adsorption or matrix diffusion limit the transformation of impulse responses in a small range of flowrates. For tracer tests realized in the kar$tic system of Ouysse in the "Causse de Gramat" (Lot, France), the use of the transformation method of impulse responses show the validity of the application in different hydrodynamic periods. In karstic media, the range of flowrates, where the transformations can be realized, is dependent of the karstification of the studied system. So the flows can he modified according to the hydrodynamic conditions.
