Is it Advection? Convection?
Environmental Enlightenment #118
“Ad” in Latin means “toward”, and “vection” comes from “vehere” meaning, to carry. Put them together and we get “advection.”
The concept of Advection is that something is being carried forward by the movement of something else. It is a technical term.
If we stretch it non-technically, we can say that the transport of people by train is “advection.”
In meteorology, advection is the horizontal transfer of any atmospheric property (hot air, cold air, moist air, etc.) by the wind.
“Con-“ in Latin is “together,” and “vection” derives from “vehere” meaning to carry. Stitch them together and we have “convection.”
The basic concept of Convection is that when you suspend heavy and light particles together, the lighter particles move up and heavier particles sink down.
A non-technical illustration of the concept might be a human pyramid.
Technically, Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity.
For a live demonstration, watch the video to the right.
The illustration below depicts toxic vapors carried under the building by convection.
The field of vapor intrusion investigations is still evolving
Acknowledgment: “ Screening For Environmental Concerns At Sites With Contaminated Soil and Groundwater; INTERIM FINAL – February 2005;” California Regional Water Quality Control Board, San Francisco Bay Region, Oakland, California.