News / USA

Study: Mississippi River Overwhelmed by Agricultural Chemicals

Dead pogies float in a fish kill in a pass near Bay Joe Wise on the Louisiana coast, Thursday, Sept. 16, 2010.
Dead pogies float in a fish kill in a pass near Bay Joe Wise on the Louisiana coast, Thursday, Sept. 16, 2010.
Greg Flakus
Every spring a so-called "dead zone" develops in the Gulf of Mexico near the mouth of the Mississippi River.

Spreading up to 13,600 square kilometers and extending all the way to the eastern Texas shoreline, the zone results from nitrogen-heavy river water pouring into the gulf, where it promotes the growth of algae. As the algae dies, it sinks to the bottom where it decomposes and depletes oxygen from the water, a condition called hypoxia that is deadly to fish and shrimp.

While scientists know what causes a hypoxic zone, a recently published study by two Austin-based hydrogeologists shows the solution may prove a hard sell for those landlocked to the north.

According to Dr. Bayani Cardenas, Associate Professor at the University of Texas's Jackson School of Geosciences, river bank sediments naturally filter water-borne contaminants, typically removing nitrates that otherwise create dead zones downstream.

"You can think of it as a spiraling flow back around the bank of the river," said Cardenas, the study's lead author. "A water molecule goes into the bank and then comes back out into the river at some downstream point, and it does that repeatedly as it travels downstream." 

And yet nitrate-heavy waters of the Mississippi River have been pouring into the gulf each spring. Determined to find out why, Cardenas, his recent study shows, found that although more than 99 percent of the river’s water does pass through sediment on its way south, the system is overwhelmed by sheer the amount of nitrogen it carries.

The Mississippi river system carries water to the gulf from 33 states and two Canadian provinces where chemicals like nitrogen are used extensively in agriculture. Farmers say the use of such chemicals is essential to produce food for a growing world population.

But Cardenas says his research shows that something needs to be done.

“If you want to curtail this process it has to be at the source, just less inputs from the start," he said, explaining that the majority of contaminants wreaking havoc on Louisiana's gulf fishermen are introduced to the water system in states farther to the north.

Aaron Packman, Associate Professor of Civil and Environmental Engineering at Northwestern University, agrees. He says farmers may be able to better control the amount of nitrate fertilizer they put on fields.

“How much fertilizer do you need to give you good yields and then how much is maybe a marginal gain from adding lots more fertilizer?" he said. "There is really a question here: can you maybe [reduce the amount] and get close to the same level of yield without having such a negative impact?”

Packman also says solutions need to be implemented upstream from Louisiana, which has a relatively small section of the river.

“The Mississippi river system is 40 percent of the surface area of the continental United States," he said. "I think it takes some further work in the distributive areas upstream that are the source of a lot of the nutrient.”

Filtration by the river system has been weakened by human-made “improvements” such as levees and canals that aid transportation and help control floods. But Cardenas says filtration works better when the river meanders through twists and turns, forcing the water to spend more time in the sediment that cleans it.

“A straight channel won’t offer this buffering," he said. "A very sinuous channel provides a lot of the contact of the river water with the sediment.”

While Louisiana has embarked on a project to divert more river water through wetlands to filter it and increase coastal silt deposits, this will have only a limited effect if states farther upstream do not take action as well.

In coming months, storms will stir the gulf waters and diminish the oxygen-depleted zone, but it will return next year and grow larger in years ahead if something isn’t done to reduce the flow of nitrogen in the Mississippi.

Cardenas's study appears in a recent issue of Nature Geosciences.

You May Like

Hostage Crisis Could Divide Japan Over Plans to Boost Military

Japanese Chief Cabinet Secretary Yoshihide Suga said Monday the government is working closely with the Jordanian government to secure the release of remaining Japanese hostage Kenji Goto More

Video Brussels Shaken as New Greek Leader Challenges Europe’s Austerity Drive

Country's youngest ever PM Alexis Tsipras, 40, sworn in Monday and says he will restore dignity to Greece by ending spending cuts More

Multimedia National Geographic Photo Camps Empower Youth

Annual mentoring program's mission is to give young people a voice to tell their own stories through photography More

This forum has been closed.
Comment Sorting
Comments
     
by: Ian from: USA
May 24, 2014 3:53 PM
Instead of apply more and more fertilizer , why don't we reduce the amount of fertilizer , and pump the same water from the river back into the irrigation system .
The farmers could save money that they have to spend to buy fertilizer , apply too much of it , waste the money down stream . We can save the fish & shrimp at the same time


by: Gerald Rivers
May 24, 2014 1:38 PM
The book titled The Silent Spring by Rachel Carson conveys clearly what the environmental impact is through pollution. Sadly many people don't worry about it until it is too late and then it becomes irreversible.

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Obama Urges Closer Economic Ties During Historic India Visiti
X
Aru Pande
January 26, 2015 9:33 PM
U.S. President Barack Obama says the United States and India must do better to capitalize on untapped potential in their economic relationship - by removing some of the roadblocks to greater trade and investment. As VOA correspondent Aru Pande reports from New Delhi, Obama spoke after participating in India’s Republic Day celebration.
Video

Video Obama Urges Closer Economic Ties During Historic India Visit

U.S. President Barack Obama says the United States and India must do better to capitalize on untapped potential in their economic relationship - by removing some of the roadblocks to greater trade and investment. As VOA correspondent Aru Pande reports from New Delhi, Obama spoke after participating in India’s Republic Day celebration.
Video

Video US, EU Threaten New Russia Sanctions Over Ukraine

U.S. President Barack Obama has blamed Russia for an attack by Ukrainian separatists that left dozens dead in the port of Mariupol and cast further doubt on the viability of last year’s cease-fire with the Kyiv government. VOA’s Michael Bowman reports from Washington.
Video

Video White House Grapples With Yemen Counterterrorism Strategy

Reports say the U.S. has carried out a drone strike on suspected militants in Yemen, the first after President Barack Obama offered reassurances the U.S. is continuing its counterterrorism operations in the country. The future of those operations has been in question following the collapse last week of Yemen’s government. VOA White House correspondent Luis Ramirez reports.
Video

Video Kerry Warns Against Violence in Nigeria Election

US Secretary of State John Kerry visited Nigeria Sunday in a show of the level of concern within the U.S. and the international community over next month’s presidential election. Chris Stein reports.
Video

Video Zoo Animals Show Their Artistic Sides

The pursuit of happiness is so important, America's founding fathers put it in the Declaration of Independence. Any zookeeper will tell you animals need enrichment, just like humans do. So painting, and even music, are part of the Smithsonian National Zoo's program to keep the animals happy. VOA’s June Soh met some animal artists at the zoo in Washington. Faith Lapidus narrates.
Video

Video Worldwide Photo Workshops Empower Youth

Last September, 20 young adults from South Sudan took part in a National Geographic Photo Camp. They are among hundreds of students from around the world who have learned how to use a camera to tell the stories of the people in their communities through the powerful medium of photography. Three camp participants talked about their experiences recently on a visit to Washington. VOA’s Julie Taboh reports.
Video

Video Saudi, Yemen Developments Are Sudden Complications for Obama

The death of Saudi Arabia's King Abdullah and the collapse of Yemen’s government have cast further uncertainty on U.S. efforts to fight militants in the Middle East and also contain Iran’s influence in the region. VOA White House correspondent Luis Ramirez reports on the new complications facing the Obama administration and its Middle East policy.
Video

Video Progress, Some Areas of Disagreement in Cuba Talks

U.S. and Cuban officials are reporting progress from initial talks in Havana on re-establishing diplomatic ties. U.S. Assistant Secretary of State (for Western Hemisphere Affairs) Roberta Jacobson said while there was agreement on a broad range of issues, there also are some “profound disagreements” between Washington and Havana. VOA State Department correspondent Pam Dockins has the story.
Video

Video US, Japan Offer Lessons as Eurozone Launches Huge Stimulus

The Euro currency has fallen sharply after the European Central Bank announced a bigger-than-expected $67 billion-a-month quantitative easing program Thursday - commonly seen as a form of printing new money. Henry Ridgwell reports for VOA from London on whether the move might rescue the eurozone economy -- and what lessons have been learned from similar programs around the world.
Video

Video Nigerian Elections Pose Concern of Potential Conflict in 'Middle Belt'

Nigeria’s north-central state of Kaduna has long been the site of fighting between Muslims and Christians as well as between people of different ethnic groups. As the February elections approach, community and religious leaders are making plans they hope will keep the streets calm after results are announced. Chris Stein reports from the state capital, Kaduna.
Video

Video As Viewership Drops, Obama Puts His Message on YouTube

Ratings reports show President Obama’s State of the Union address this week drew the lowest number of viewers for this annual speech in 15 years. White House officials anticipated this, and the president has decided to take a non-traditional approach to getting his message out. VOA White House correspondent Luis Ramirez reports.
Video

Video S. Korean Businesses Want to End Trade Restrictions With North

Business leaders in South Korea are calling for President Park Geun-hye to ease trade restrictions with North Korea that were put in place in 2010 after the sinking of a South Korean warship.Pro-business groups argue that expanding trade and investment is not only good for business, it is also good for long-term regional peace and security. VOA’s Brian Padden reports.

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More

All About America

AppleAndroid