BATON ROUGE, Louisiana - 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.