Agriculture Alters Mississippi River Chemistry

Agriculture Alters Mississippi River Chemistry

Feb, 2008  - Over the past 50 years, 
farming has altered the hydrology and chemistry of the Mississippi River, 
injecting more carbon dioxide into the river and raising river discharge, 
finds a study by researchers at Louisiana State and Yale universities. 
LSU Professor R. Eugene Turner and graduate student Whitney Broussard, 
along with their colleagues at Yale, tracked changes in the discharge of 
water and the concentration of bicarbonate, which forms when carbon 
dioxide in soil water dissolves rock minerals. 
Bicarbonate in rivers plays an important, long-term role in absorbing 
atmospheric carbon dioxide, a greenhouse gas. 
Oceans then absorb this carbon dioxide, but become more acidic in the 
process, making it more difficult for marine organisms to form hard shells 
- a necessary function in coral reefs. 

Researchers concluded that liming and farming practices, such as changes 
in tile drainage, tillage practices and crop type, are most likely 
responsible for the majority of the increase in water and carbon in the 
Mississippi River, North America's largest river. 
"It's like the discovery of a new large river being piped out of the corn 
belt," said Pete Raymond, lead author of the study and associate professor 
of ecosystem ecology at the Yale School of Forestry and Environmental 
Studies. 
The research team analyzed 100 year old data on the Mississippi River 
warehoused at two New Orleans water treatment plants, and combined it with 
data on precipitation and water export. 
"The water quality information we used has been sitting idle for over 50 
years in an attic in New Orleans, waiting to be discovered," said 
Broussard, who is pursuing a doctoral degree in coastal ecology at LSU. 
"I felt like a treasure-hunter when we opened those boxes in that 100-plus 
degree attic to find those data logs. You never know where your research 
will take you if you're open to suggestion and serendipity." 
Turner, distinguished professor of coastal ecology, added, "and [where it 
will take you] if you have the benefits of long-term collaborations of 
trusting and high-quality academic research groups." 
The research team used the data to demonstrate the effects of this excess 
water on the carbon content of the river, and they argue that the 
additional water in the river is altering the chemistry of the Gulf of 
Mexico as by increasing the amount of nutrients and pollution the river 
transports to the Gulf. 
"We're learning more and more about the far-reaching effects of American 
agriculture on rivers and lakes. This also means that the agricultural 
community has an incredible opportunity to influence the natural 
environment in a positive way, more than any other contemporary 
enterprise," said Broussard. 
"If we want to clean the water, we have to steward the land with right 
agriculture." 
The study, "Anthropogenically Enhanced Fluxes of Water and Carbon from the 
Mississippi River," is published in the current issue of the journal 
"Nature." 

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