Environmental Enlightenment #189
By Ami Adini - Re-issued June 3, 2016

This is a SHORT, LIGHT and SIMPLE newsletter. Its purpose is to rekindle in the initiated terminology they have once learned, and enlighten the uninitiated on terms they may have heard but never known the meaning of.

Where Did That Chemical Go?

Acknowledgement is given to a book of this name by Ronald E. Ney, Jr., Ph.D., Van Nostrand Reinhold, New York, 1990, on which this material is based.

To dissipate in the environment means to reduce to the point of disappearing.

Dissipate derives from Latin dissipare “to disperse,” from dis- “apart” + supare “to throw.”

For example…

The dust devil in this picture will eventually collapse and dissipate.


Image credit: NASA/U. of Michigan

The plume of smoke from the brushfire is dissipating into the surrounding air.

A chemical can dissipate in a variety of ways:

  • It can break down to other chemicals, more toxic or less.

For example, left for natural bacteriological attack, tetrachloroethylene (aka PCE, perc and other names: a carcinogenic solvent used in dry cleaning operations and degreasing of metals) will break up to CO2 (carbon dioxide) and trichloroethylene (carcinogen), which in turn will decompose to dichloroethene and CO2, continuing to vinyl chloride (highly toxic) and CO2, and down to ethene or ethane plus CO2.

  • It can scatter.

See how the ink diffuses (scatters) in water.



  • It might adsorb (attach) to soil particles



  • It might evaporate.


Image credit: Ron Kurtus & School for Champions, LLC

  • It could be sucked out by plants or animals.

We measure the rate of dissipation by the half-life of the chemical in the environment.

Half-life is the time it takes for the chemical to be reduced by one-half of its original amount. The lost 50% could be in the form of breakdown products.

For example, the time required for the body to eliminate one-half of the total amount of caffeine consumed varies widely. In healthy adults, caffeine’s half-life is approximately 4.9 hours (Ref. Wikipedia).

This is why breakdown products must be identified and studied in the same way the parent chemical is studied.

The dissipation of a chemical may be real, as in the breakdown of the parent chemical to its daughters.

The dissipation may not be real, as in the case when the chemical migrated from the source area elsewhere.

Image Credit: Maine Geological Survey http://www.maine.gov/doc/nrimc/mgs/explore/water/facts/aq-04.htm

One must always remember this: the fact that a chemical cannot be found does not mean it is not there. Good testing will establish its whereabouts.

You can find past issues of "Environmental Enlightenment" at www.amiadini.com - A wealth of information about environmental site assessments in the real estate transactions and issues concerning assessment and cleanup of contamination in the subsurface soil and groundwater.

Call me if you've got any questions. There are no obligations.

Ami Adini & Associates, Inc.
Environmental Consultants
Underground Storage Tank Experts
818-824-8102; 818-824-8112 fax

Ami Adini is a mechanical engineer, California Registered Environmental Assessor,Level II (Exp.), and president of AMI ADINI & ASSOCIATES, INC. (AA&A), an environmental consulting firm specializing in all phases of environmental site assessments, rehabilitation of contaminated sites and upgrading of underground storage tank facilities. AA&A supplies practical solutions to environmental concerns using the highest standards of ethics and integrity while providing its clients with maximum return on their investments.