In a story for Chemical & Engineering News, I report that little progress has been made in reducing farm runoff, the main cause of a “dead zone” in the Gulf of Mexico.
Despite decades of conservation efforts, nitrate pollution in the Mississippi River basin hasn’t improved. Between 1980 and 2008, nitrate levels have held steady at some sites in the river and its tributaries, while increasing by more than 70% at another, according to a new study by researchers at the U.S. Geological Survey (Environ. Sci. Technol., DOI: 10.1021/es201221s).
Since the mid-20th century, farmers in the Mississippi River basin have applied nitrogen and phosphorus fertilizer to their crops. Some of that fertilizer washes into the Gulf of Mexico, where it feeds algal blooms. As bacteria devour the algae, they suck dissolved oxygen from the water and create a dead zone: an area of low-oxygen water where many organisms cannot survive.
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