By Brook Beeler,
Communication Manager, Eastern Region
We are all familiar with the term acid and we often hear about the pH scale, but what does it really mean? What is the pH scale really
all about?
It is a delicate dance at the molecular level. Let’s break it down.
The foundational parts
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Water molecules are made up of
one oxygen atom and two hydrogens.
Distilled water has a neutral pH of 7.
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Molecules are made of atoms and are generally considered
neutral, meaning they do not have a positive or negative electrical charge. Water
is an example of a neutral molecule made of one oxygen and two hydrogen atoms. A neutral molecule is considered stable and
happy.
In the molecular world, though, being happy isn’t always
good enough. Molecules are often in a state of flux. The atoms that make up
molecules tend to move around a lot. Molecules may break apart to form ions,
which do have a positive or negative electrical charge. Ions can be an atom or
multiple atoms combined. If our water molecule breaks apart, the likely
combinations of ions would be positively charged hydrogen and oxygen bonded to
hydrogen or hydroxide, resulting in a negative charge.
Acid and base
The pH scale helps scientists measure whether or not a solution is acidic or basic. In chemistry, a solution is defined by one substance being dissolved in another. Solutions are easiest to understand as a liquid, but it is important to note that they also exist in gas and solid forms.
An acid is a solution that has a higher concentration of
positively charged hydrogen ions (H) than negatively charged hydroxide ions (OH).
Common examples of acids are lemon juice and vinegar. A base has a higher
concentration of OH ions. Common examples are baking soda and household ammonia.
The scale ranges from 0 to 14. Smack dab in the middle (7)
is considered neutral, which is neither acidic nor basic. And what substance do
you suppose comes in at that number? Our happy water molecule. When water is in
a pure or distilled state, it measures a pH of 7.
The lower the number (0-7), the more acidic it’s considered. And the higher the
number (7 to 14), the more basic it is.
The pH scale may seem small, but each whole number represents
a ten-fold leap in concentration of either H ions or OH ions. For example, rain
is slightly acidic with a pH that measures about six. A grapefruit is
approximately three on the pH scale. That means that a grapefruit is 1,000
times more acidic than rain.
Both acids and bases play important roles. They help us
clean and, in some cases, make delicious salad dressings. However, an
overabundance of solutions that are too high or too low on the pH scale can
cause problems with our health and the environment.
Our work related to pH
pH affects people and the environment and can be toxic. At
very high or very low pH levels, those charged ions dancing around in solutions
want to find a mate of the opposite charge. They woo neutral molecules,
attracting them away from stability. For example, metals like aluminum become
soluble at a low pH. This means it is more likely to dissolve and move through
a solution and make its way into drinking water or the food chain. That’s no
good.
In bodies of water, pH is generally very stable and the
value doesn’t change much. However, if we notice that pH values change, it’s
likely an indication that some sort of pollution is affecting the water.
So we pay attention to pH. We require wastewater discharges and air
permits to address pH. It is a parameter often addressed in our
water quality improvement plans.
It can also indicate if a waste material is dangerous and has specific disposal
requirements according to state laws.
Holcim Inc. Toxics
Cleanup Site’s problem is with pH. Holcim owns property along the Spokane River in Spokane
Valley where soil and groundwater is contaminated with cement kiln dust.
Holcim and its predecessor companies operated a cement
manufacturing plant at the site until 1967. Cement kiln dust, a byproduct of
cement manufacturing, was landfilled on the northern portion of the site before
Washington state laws for
dangerous waste
prevented that practice.
Cement kiln dust has a high pH and is considered caustic. Because
we pay attention to pH and the complex nature of groundwater, proximity to the
river and location of drinking water wells, Ecology required the parties
responsible to investigate the contamination and evaluate cleanup options.
This cleanup site is in early stages of the cleanup process.
But Ecology is continuing to work with the property owner to give this site a
clean bill of health. A cleanup option will be selected and implemented
ensuring that there is a pH solution for the health of people and the
environment.
For current information visit the
Holcim Inc. cleanup site
webpage.
Tacoma-Pierce County Health Department lifted the swimming advisory for Ruston Way Waterfront near Les Davis Pier. Bacteria sources were corrected, and subsequent bacteria testing showed that water quality improved. The Health Department has removed the no contact advisory signs.
