Scale depicting the concentration of pH and examples of solutions.

iBase ID

396742

Creator

Joyce, Katherine Spencer

Title

Scale depicting the concentration of pH and examples of solutions.

Type

Illustration

Date

10/29/2013

File name

graphics/Oceanus50n2/75.jpg

Notes

Caption from Oceanus magazine, vol. 50, no. 2, page 75:
A common response Sarah Cooley gets when she speaks to community groups about ocean acidification is, "What do you mean, ocean acidification? The ocean is not acidic! Seawater is never going to get below pH7".
The term "ocean acidification" is somewhat confusing, said Cooley. The pH of seawater is near 8, which makes it mildly alkaline, or basic–-but any decrease in the pH of a liquid is considered acidification.
"It's a lot easier to say ocean acidification than ocean "de-al-kalinization" she said.
The term pH is an index of how many protons, or hydrogen ions (H+), are dissolved and free in a solution. The pH scale goes from 0 to 14. A fluid with a pH of 7 (like distilled water) is neutral. Below 7, it is acidic. Above 7, it is alkaline.
The more below or above 7 a solution is, the more acidic or alkaline it is. The scale is logarithmic, not linear, so a drop from pH 8.2 to 8.1 indicates a 30 percent increase in acidity; a drop from 8.1 to 7.9 indicates a 150 percent increase in acidity. Bottom line: Small-sounding changes in ocean pH are actually quite large and definitely in the direction of becoming less alkaline, which is the same as becoming more acidic.
If you think about it, we use descriptive words like this all the time. A person who stands 5'5" tall and weighs 300 pounds isn't thin. If he loses 100 pounds, he still won't be thin, but he will be thinner than he was before he went on the diet. (And we are more likely to comment that hes looking trimmer than to say he's not as fat as he used to be.)
Image Of the Day caption:
The pH scale, shown here, indicates the concentration of hydrogen ions (H+) in a liquid. Above pH7, a fluid is alkaline; below 7, it is acidic. Seawater is slightly alkaline, but has become more acidic in recent years due to increasing carbon dioxide in the atmosphere. Because the pH scale is logarithmic, a small change in pH represents a big change in relative acidity, which can have devastating effects on organisms that use calcium carbonate to build shells, spines, or other hard structures. Many scientists at WHOI are working to understand how ocean acidification affects marine organisms and, ultimately, human communities.

Credit line

Illustration by Katherine Spencer Joyce

Copyright statement

Other restrictions

Provenance

URL