Advection describes the passive movement of a substance (or Heat) with the moving fluid. The purely advective transport leads to a shift of material particles with the field velocity v of the groundwater in the direction of the flow vector.

 

Purely advective mass transport

 

The equation for the advective mass flux is:

 

The field velocity v is the quotient of the Darcy velocity v_f and the porosity n:

 

The concentration of the dissolved substance is c.

 

Diffusion