What is advection or convection?

• A. The exposure route.
• B. The normal movement or migration of a contaminant through a medium.
• C. The contact of a contaminated medium with a receptor population.
• D. The release of material from a source.

Answer: (B)

Advection, or convection, is the transport of contaminants by the bulk flow of the fluid itself. In groundwater, for example, water moving through soil pores carries dissolved contaminants along at the groundwater velocity; in a river, the contaminant travels downstream with the current. This describes the normal movement or migration of a contaminant through a medium—the substance is carried with the moving fluid.

This is distinct from exposure-related terms or source terms: exposure route refers to how a person might be exposed, the actual contact with a receptor population is the exposure event, and release from a source is the emission of material from its origin. Advection specifically targets how the contaminant moves through the environment via fluid flow.