Sore throat is a symptom, not a disease. In each case, there was a different cause that dictated a different treatment. The scratchy throat probably was a mechanical problem caused by dry, heated winter air and aggravated by my friend's tendency to breathe through her mouth when she sleeps.
Biogeochemistry includes the history of the great carbon reservoirs in the crust of the Earth, like limestone rocks and the coal deposits, as well as the distribution of nitrate and phosphate in the ocean.
The ocean contains the largest active pool of carbon near the surface of the Earth. The natural flows of carbon between the atmosphere, ocean, terrestrial ecosystems, and sediments is fairly balanced, so that carbon levels would be roughly stable without human influence.