Chem Prof wrote this; blame him for this shyte.
Over two months ago, a news article appeared in the Oregonian:
I wondered how look it would take for the complaints to appear. It took until June 30.
Chuck Weise wrote in Anthony Watts' blog, WattsUpWithThat a post called
I was surprised by the basic errors in chemistry made by the writer and those who commented on WUWT, so I wrote a few comments (they appear under the name Chem Prof). I was dismayed by the barrage that followed.
This is not
about politics. It is about arithmetic and simple arithmetic functions.
Chuck Weise's
WUWT post says
nothing about
sources of error in measurements of pH,
nothing about
sources or sinks of hydrogen ions in ocean brine,
nothing about
complex equilibria,
nothing about
the effects on hydrogen ion concentration due to other species,
nothing about
non-ideal behavior of hydrogen ion in solution.
Here are things
that he actually wrote:
(1) "As
you also know, there are 14 orders of magnitude that define the pH scale from zero to fourteen
units as per this equation. "
This is
incorrect. The pH scale is open-ended.
(2) So if we
moved .1 units towards acidity from the alkaline 8.2 to 8.1 oceans and compared the
change, we have [delta H+] = 8 E-9/6 E-9 = 1.33 or a 33% increase in the hydrogen
ion concentration, not an increase of 33% in the pH. None the less, that is how the
story was reported and it is wrong.
In fact, the
story does not mention pH at all. Lori Tobias quotes Alan Barton (hatchery
research manager at Whiskey Creek Shellfish Hatchery on Netarts Bay), ' "Over the
last 100 years we've made the ocean a little more acidic than it used to
be," he said.
"There is a 30 percent increase in the acidity of the ocean. If you are an oyster lover,
that little bit more acid is a big problem. Eventually it will put our hatchery out of
business." '
No mention of
pH.
Here is a list
of every reference to acids, acidification, or acidity in the article:
"Rising
levels of carbon dioxide -- which lead to increased acidity in the ocean water, or ocean acidification
-- were making it difficult, if not impossible, for the larvae to
grow."
"The shell
[of oyster larvae] is easy to dissolve and sensitive to acidic
conditions, Barton said,
unlike the hard adult oyster shell that's made of calcite."
"Some say
it is impossible for the larvae to grow the shell; some say they can, but it is really
hard to do.They use a lot of energy and don't grow. Whether it is impossible or
just difficult, they are still dead. We know that the ocean acidification is causing our
problem."
"The impact
of ocean acidification is heightened by upwelling, which occurs when winds blowing
from the north push the ocean surface waters away from the coastline, allowing deeper
waters to move to the top. The deeper waters are already higher in carbon
dioxide from all the decomposition below. Water that upwells is always higher in
acidity, but our use of fossil fuels has added to the carbon dioxide in the atmosphere,
in turn increasing ocean acidity, Barton said. "
"Over the
last 100 years we've made the ocean a little more acidic than it used to be," he
said. "There is a 30 percent increase in the acidity of the ocean.
If you are an oyster lover,
that little bit more acid is a big problem. Eventually it will put our hatchery out of
business."
That is it. No
mention of pH.
(3) "You
agreed with me in my premise that hydrogen ion concentration makes up the pH but it
is not defined by that number because the number of ions in an aqueous solution
of water are very large. "
This is
incorrect. Chuck Weise is correct earlier when he says that pH is defined by
the equation pH = -
Log[H+], where [H+] is the hydrogen ion concentration. Now he says it isn't defined
'by that number.' This is just wrong. In fact, pOH and pK, and for that matter,
pAnything are defined in a similar manner:
pAnything = -Log(Anything)
with the
corresponding unique inverse relationship
Anything=10^(-pAnything) .
This is done in
chemistry all the time because the scale of chemical quantities such as concentration varies by many orders of
magnitude.
How do chemists
describe how much of a given substance is present in a solution? There are a
number of ways, but every single one of them can be related to the molar concentration of
a substance, that is, moles of substance per liter of solution, which is usually written
as [X], where X is the substance in solution; it links two quantities: (a) the moles of
a given material - a specific way of counting the molecules or ions of a given type
and (b) the volume of the solution measured in liters.
For example,
hydrogen ion concentration, written [H+], represents the moles of hydrogen ion in
a liter of solution. 0.00010 mole of hydrogen ion in each liter of solution is written as 0.00010 moles/Liter or 0.00010 M when abbreviated. The quantity 'moles per liter' is also called 'molar' for short; so a 0.50 molar NaCl solution has 0.50 moles of NaCl per liter of solution.
What does Chuck
Weise mean by "the number of ions in an aqueous solution of water are very
large"
? I have no idea and it is irrelevant.
Comments that
argue that "It’s even more complicated than that, because there are buffers
involved" or something like that are missing the whole point of the
acid-base chemistry of a buffered
solution. The presence of a buffer (another weak acid or base) in significant
quantity makes it more difficult to change the pH of a solution, not
easier. So a significant decrease in the pH of a buffered solution is a clear
indication that a significant source of acid has been added.
Some comments
represent serious scientific ignorance:
"It is
being assumed by these people that the ocean obeys the second law of
thermodynamics, it does not
because of surface tension."
"The oceans
are infinitely buffered."
"A pH change
of .1 corresponds to a change in hydrogen ion concentration of ..007%."
"A pH
change from 8.2 to 8.1 cannot be truthfully described as ‘becoming ‘more
acidic’. "
"the
acidity isn’t increasing; the alkalinity is decreasing."
"pH is
(negative) log because that is how organisms perceive acidity. They don’t
perceive it in a linear
scale, so it shouldn’t be quoted in one. No-one, but no-one talks about acidity other than via
pH."
"The reason
the change in pH is meaningless in this situation is that in a pure system
where only H+ is
considered to be driving pH, the change is one gram of hydrogen ions in one billion liters
of water."
"Weren’t
they lucky to have chosen the H+ ion concentration as reference, and not the OH- (OH
minus) ion concentration?"
"Chem Prof
seems to have misunderstood the nature of the complaint. The ion concentration is
not the acidity (or alkalinity) as munderstood in pH. It is not used to derive the pH
from -log10 of H+ ions...The measurements of the ocean are of pH...The ion
concentration is derived from the pH. Not the other way round."
"As a
Chemical Professor – cough! – you will be aware that there is a p[OH] measure
too. So why not quote
the alarming story that – oh noes! – hydroxide concentration in the oceans has fallen
by 80%. I would hope you would see how stupid it was to use it, regardless of
being technically true."
NOTE: That isn't
true; a 0.1 decrease in pH corresponds to a 0.1 increase in pOH, with a corresponding
decrease in [OH-] of 26.0%. If you are mystified by this, please note this arithemetic:
1.26 x 0.794 = 1.00 .
On additional note:
"I’ve copied a discussion from Wikipedia..." is not the strongest
line of argument one
might take.
Quite
a few comments indicate there is confusion between the ideas of variability
in a measurement
and an error in a measurement. There is a large variability in the
height of a
human, varying from 0.55 m tall Chandra Bahadur Dangi of Nepal to 2.45 m tall Zeng
Jinlian of the People's Republic of China. This natural variation does not
preclude us
from measuring individual height to a precision of 0.001 m or better. And
variations in
human height are worthy of study:
Chao-Qiang
Lai, of the Jean Mayer Institute wrote
'
..."How much variation (difference between individuals) in
height is attributable to genetic effects and how much to nutritional
effects?" The
short answer to this question is that about 60 to 80 percent of the difference in
height between individuals is determined by genetic factors, whereas 20 to 40 percent
can be attributed to environmental effects, mainly nutrition.'
He adds,
“Heritability
allows us to examine how genetics directly impact an individual's height. For example, a
population of white men has a heritability of 80 percent and an average height of 178
centimeters (roughly five feet, 10 inches). If we meet a white man in the street who is
183 cm (six feet) tall, the heritability tells us what fraction of his extra height is caused
by genetic variants and what fraction is due to his environment (dietary habit
and lifestyle). The man is five centimeters taller than the average. Thus, 80 percent
of the extra five centimeters, or four centimeters, is due to genetic variants,
whereas one centimeter is due to environmental effects, such as nutrition.”
Notice that one
is still able to make a strong scientific statement about a 1 cm height
difference in spite of a
200 cm wide variation in human height.
Some
comments were made by those hanging their hats on the high ionic strength of sea water (it is
significant, about 0.73
mole/liter) or the difference between the activity of hydrogen ions and [H+],
but forgetting entirely that the activity of a 10^(-8) molar solution is ---- 10^(-8) molar ! Debye-Hückel theory plays no
role in this whatsoever.
Chuck Weise
adds, "In all of the work- ups and computations I have seen NOAA and others do when
talking about ocean acidity, the units have always been referenced in units of pH. I
have never seen work- ups in ion concentration" and misses the
point again.
Some comments
are rich with irony:
"Does
anyone know how much CO2 it would take to change 1.3 billion cubic kilometres of [buffered - my
clarification] salt water from pH 8.2 to 8.1?"
"Because
even though the numbers do calculate to roughly 30%, it’s incredibly inappropriate to
apply percentages with pH."
"To many
non-scientific readers this implies a hugely significant increase in environmental
impacts – 30% more acidic ! NOAA compound the misleading nature of this
statement by not making it clear that this is a reference to a percentage change in
hydrogen ion concentrations."
Willis
Eschenbach: ..."applying
percentages to logarithmic scales doesn’t work."
Exactly.
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