It is difficult to think of an area of biological, chemical or environmental science where acid-base chemistry is irrelevant. Even in organic solvents there are protonations and deprotonations that are important for catalysis. The only systems where acid-base chemistry plays little or no role are non-aqueous solvents where water is rigorously excluded. Otherwise, wherever there is water there is a possible role for acids and bases to affect chemical reactivity. In human health we can identify gastrointestinal health as a major area for pH to play a role. In fact, almost everyone uses some kind of anti-acid at some time or other to prevent reflux of gastric flid from causing damage to the esophagous. Blood pH is crucial for health. The chemical changes that affect blood pH are diseaes states that affect hemoglobin, which is a major regulator of the pH due to its relative abundance. In general, blood needs to be colloidally stable and thus the pH must be maintained in the correct range to prevent aggregation or premature clotting. This aspect of human health is so vital that even small deviations from the optimum can have very negative consequences.
Environmental aspects of acid-base chemistry are exremely important to the overall heatlh of ecosystems. Unfortunately, we have evidence that there are significant changes in the global pH balance. These changes are perhaps among the most serious problems we face. Ironically, the public debate over fossil fuel use often centers on the issue of "global wamring", which is a minor problem for our ecosystem. The pH balance is the true global problem that we need to confront. Both the ocean and our soils are becoming more acidic. At some point the soil will not longer be fertile and it will become useless for food production. Forests will die and whole ecosystems may cease to exist.
The situation in the oceans is even more serious. Diatoms are responsible for producing 40% of the air we breath. Their shells are made of calcium carbonate. As the ocean pH decreases the stability of calcium carbonate decreases. We can already see these effects in the bleaching and descruction of coral reefs. Coral reefs are also mainly composed of a base material that continus calcium carbonate as well. However, the diatom shells are essential for the survival of these microscopic organisms that exist throughtou the ocean and produce O2 by photosynthesis. The interrelationship between the calcium carbonate shells, carbon dioxide and hydrogen carbonate (also known as bicarbonate) is crucial to an understanding of the stability of diatom shells and other marine life forsm that depends on CaCO3. The next video discusses how HCO3- is a reservoir in the ocean. The ocean is vast and it is hard to imagine that such a huge reservoir could be changing. However, the data suggest that the pH of the ocean is decreasing steadily.
It seems that ocean acidification is the forgotten problem in the public debate over the effects of CO2 in the atmosphere.. The facts are clear. CO2 is entering the ocean at a rate of approximate 7 billion tons per year. Despite the huge volume of the ocean this is a sufficiently large amount that the ocean pH is decreasing at a rate of approximate 0.002 pH units per year (a conservative esimate). At this rate we can expec the ocean pH to decrease by another 0.2 pH units in the next 100 years. As the pH decreases CaCO3 is increasingly destabilized. There is already evidence for thinning of shells and changes caused by the decreases of the past 100 years. At some point the diatoms will be unable to form shells and will die en masse. Humankind will confront a major reduction in the O2 levels on the planet. The only hope is that another life form (hopefully photosynthetic) could take over when the diatoms cease to exist. This process appears to be irreversible in the short run (meaning the time scale of hundreds to thousands of years). The data show very clearly where we are headed and the only question is how long it will take to reach the tipping point.
