https://phys.org/news/2018-06-river-unique-chemical-signature.html

"While increased Mississippi River sulfate and its isotope signatures do not directly impact people, they are certainly symptoms of, and another way to gauge, the magnitude of our impact on natural chemical cycles," said Bryan Killingsworth, the lead author of the study, who conducted this research for his Ph.D. with Huiming Bao, the Charles L. Jones professor in the LSU Department of Geology & Geophysics. Killingsworth is currently a post-doctoral researcher at the European Institute for Marine Studies in Plouzané, France.

The process of pyrite rusting, or oxidation, that produces sulfate also generates acid. The acid can make rocks, such as limestone, dissolve at a faster rate, which can release carbon dioxide into the atmosphere. The acid also increases the amount of dissolved chemicals from rocks into rivers, and may contribute to ocean acidification.