Human activity greatly impacts the natural chemistry of the largest river in North America — the Mississippi River. In a new, large-scale study, LSU geologists have identified a unique chemical signature in the river.
Human activity greatly impacts the natural chemistry of the largest river in North America — the Mississippi River. In a new, large-scale study, LSU geologists have identified a unique chemical signature in the river.
Materials containing carbon, oxygen, nitrogen and sulfur build up, break down and transfer between the atmosphere, freshwater, the ocean and rocks. Dissolved sulfate is a key chemical compound in this process and can be found nearly everywhere including rivers, lakes, the ocean and drinking water. To better understand how sulfate transfers between rocks and the ocean, the geologists extracted and analyzed 135 Mississippi River water samples for dissolved sulfate. They compared the ratios of the heavier versus lighter forms of sulfur and oxygen, or their isotopes, which provided them with a unique signature to trace. They found that 75 percent of the sulfate in the Mississippi River comes from the rusting of pyrite minerals in rocks, which is a naturally occurring process that is also greatly enhanced by human activities such as coal mining.
“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.
Read more at Louisiana State University
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