A volcanic crater in Indonesia over 7,700 feet (2,350 meters) above sea level is home to Earth’s largest acidic lake, with water like battery acid. In this excerpt from “Beyond The Sea: The Hidden Life in Lakes, Streams, and Wetlands” (Johns Hopkins University Press, 2024), author David Strayer examines the extreme chemistry of some of our planet’s natural lakes — and the life they host.
I know people who really like water chemistry. They spend all day thinking about redox reactions and mass balance and valences and solubility indices and spiraling metrics, and when the workday is over, they go out for a beer with their friends and talk about redox reactions and spiraling metrics. (In my experience, water chemistry enthusiasts are often beer connoisseurs as well, which makes sense in a weird way if you think of a glass of beer as a special kind of aqueous solution.)
These are people who when asked to name their favorite chemical element say “ooh, ooh, can I have three?” and then name five. I’m guessing that you’re not one of those people.
So instead of going into great detail, element by tedious element, about the enormous variation in the chemical content of inland waters, I’m just going to briefly talk about how much pH varies across inland waters, assume that is sufficient to make my point about the chemical diversity of inland waters, and move on to subjects that you like better than water chemistry.
You may remember from high school chemistry that pH is a measure of whether a substance is acidic or basic (or “alkaline”). Materials that are neutral (neither acidic nor basic) have a pH of 7, acidic materials have a pH less than 7 (household vinegar has a pH of about 2.5), and basic materials have a pH greater than 7 (household ammonia has a pH of about 11.5). The pH scale is logarithmic — a change in pH of one unit represents a 10-fold change in acidity (technically, a 10-fold change in the activity of hydrogen ions). So vinegar at a pH of 2.5 has about a billion times more hydrogen ion activity than does ammonia at a pH of 11.5.
The logarithmic scale allows us to conveniently express enormous differences in chemistry but makes it easy to forget that small differences on the pH scale can mean big differences in chemistry which can have large consequences.
For instance, the ocean today has a pH of around 8.1, which tells us that it is a little basic. Higher concentrations of carbon dioxide in the air resulting from fossil fuel burning have caused the…
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