massatotransport

Massatotransport is a term sometimes used to describe the collective movement of mass within and between phases, driven by gradients in concentration, temperature, pressure, or electric potential. In practice, it overlaps with the broader field of mass transfer or mass transport phenomena, and its exact usage can vary by discipline. The central idea is to understand how species move and distribute themselves in space and over time.

The fundamental mechanisms include diffusion, convection (advective transport), dispersion, and, in charged systems, electromigration. In simple one-component systems, diffusion is described by Fick’s laws. Fick’s first law states that the diffusive flux J is proportional to the negative gradient of concentration (J = -D∇C). Fick’s second law describes how concentration changes in time due to diffusion (∂C/∂t = D∇^2C). When bulk flow is present, the convection-diffusion equation applies: ∂C/∂t + v·∇C = D∇^2C, where v is the velocity field. For multi-component mixtures, the Maxwell-Stefan formulation provides a more detailed description of coupled diffusive fluxes among species.

In porous media and environmental contexts, massatotransport models often combine advection, dispersion, and diffusion to predict contaminant transport in soils and groundwater. In biology and medicine, the focus includes transmembrane transport, active transport, facilitated diffusion, and related kinetic processes that govern how substances cross biological membranes.

Terminology varies, and some texts reserve the terms mass transfer or mass transport for these concepts. Massatotransport thus serves as a broader umbrella term that, in many applications, aligns with the established framework of diffusion, convection, and related transport processes.