Environmental Enlightenment #210
By Ami Adini - Reissued June 28, 2017

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 knew the meaning of.

Power of Simplicity
The EPA’s Citizen’s Guide to Cleanup Technologies

Series 9: In Situ Chemical Reduction

See our Newsletter, Environmental Enlightenment #200, for introduction to one highly valuable, plainly written series of Citizen’s Guides published by the EPA at http://www.clu-in.org/products/citguide

With this issue we introduce the EPA’s Citizen’s Guide to In Situ Chemical Reduction. You can reach it through the hyperlink under the blue header below.


The building blocks of matter are atoms; and atoms have nuclei (cores) surrounded by shells of rotating electrons.

Licensed under GNU Free Documentation License, Version 1.2

The word oxidation originally implied reaction with oxygen. Ultimately, the meaning was generalized to include all processes involving loss of electrons.

When oxygen combines with iron to make rust, the iron loses electrons to the oxygen; thus, the iron is oxidized.

Photograph by Tony Fischer, licensed under Creative Commons Attribution-Share Alike 2.0 Generic License

When sodium combines with chlorine to make table salt, the sodium loses electrons to the chlorine; thus, we say that the sodium has been “oxidized” even though no oxygen is present.

  Salt shaker  salt shaker

The word reduction originally referred to the loss in weight upon heating a metallic ore to extract the metal. In other words, ore was "reduced" to metal.

Photograph by Hans Splinter and licensed under Creative Commons Attribution-Share Alike 2.0 Generic License

Antoine Lavoisier (1743-1794) showed that this loss of weight was due to the loss of oxygen as a gas.

Later, scientists realized that the metal atom gains electrons in this process. The meaning of reduction then became generalized to include all processes involving gain of electrons.


Oxidation and reduction go together. He who donates is oxidized. He who gains is reduced.

Even though "reduction" seems counter-intuitive when speaking of the gain of electrons, it might help to think of reduction as the loss of oxygen, which was its historical meaning.

(Acknowledgement: http://en.wikipedia.org/wiki/Redox#Etymology)

A reducing agent is a chemical that causes reduction. In the case of rust, the iron acts as a reducing agent on the oxygen.

is the amount of mass that an object contains per unit volume.

Examples for units of volume are ounce, quart, teaspoon, cubic centimeter, liter, bushel, barrel, cord, golf bag, Sydney Harbor, and more.

Photograph by La Citta Vita (http://www.flickr.com/photos/la-citta-vita/) and licensed under Creative Commons Attribution-Share Alike 2.0 Generic License

Thus density can be expressed as kilograms per liter, pounds per bushel, tons per Sydney Harbor, and more.

The universal force of gravity is pull between masses.

The more material we have per unit of volume, the stronger is the gravity pull; thus, denser is heavier.

And Archimedes tells us that objects denser than water sink in water.

“Titanic Sinking” by Willy Stöwer (1912)

stands for “dense non-aqueous phase liquids.” These are other-than- water (non-aqueous) liquids denser (therefore heavier) than water.

When DNAPLs get in groundwater they sink to the bottom of the aquifer.

Perchloroethylene (PCE) (a dry cleaning solvent) is a DNAPL.

(Source: Washoe County NV Water Resources Department)

Examples of other DNAPLs include coal tar, PCBs, mercury and extra-heavy crude oil.

In chemistry, valence indicates the number of electrons that a chemical reaction has added or taken away from an element. The higher the valence, the stronger is the combining power of that element.

(Acknowledgement http://en.wikipedia.org/wiki/Valence_%28chemistry%29)

Illustration from Hints to Golfers by Niblick, published 1902

The origin of the word valence is from a Latin valere meaning strength. Words like valiant, value and valor derive from valere.

The image below represents a molecule of water: two hydrogens in connection with one oxygen.

Source: NASA


The oxygen has pulled one electron from each hydrogen into the outer electronic shell of the oxygen.

We say that the oxygen is in a valence of -2 and each of the hydrogens is in a valence of +1.

Chromium can appear in a valence of 3 in one chemical and in a valence of 6 in another chemical. In its 3-valence chromium is benign, while in the 6-valence it is a harsh carcinogen.

Metals in pure form are not stable in the environment (gold is an exception). We have to extract them from naturally occurring ores, and we invest great energy in the process.

Paraburdoo iron ore mine in the Pilbara Region of Western Australia; Photo by Calistemon and licensed under the Creative Commons Attribtion-Share Alike 3.0 Unported License

 Zero Valent Metals are metals in their pure form. They can’t wait to impart electrons to others. Thus we use them as reducing agents.

A common reducing agent is Zero Valent Iron (ZVI).

A 700g individual Chinga iron meteorite (Ataxite, class IVB).
Source: Wikimedia Commons (H. Raab) and licensed under GNU Free Documentation License, Version 1.2

Go to the EPA’s Citizen’s Guide to In Situ Chemical Reduction at http://www.clu-in.org/download/Citizens/a_citizens_guide_to_in_situ_chemical_reduction.pdf for the rest. It is simple and fun to read.

You can find past issues of "Environmental Enlightenment" at www.amiadini.com with wealth of information about issues concerning assessment and cleanup of contamination in the subsurface soil and groundwater.

Call me if you have any questions. There are no obligations.

Ami Adini Environmental Services, Inc.
Environmental Engineering Consultants & Contractors
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California Lic. #1009513 A B HAZ ASB
818-824-8102; mail@amiadini.com

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