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EPA Cracking Down on Urban and Agricultural Runoff Blamed for Dead Zones

By Matthew Berger

Nov 13, 2009

Nitrogen makes up almost 80 percent of the air in Earth’s atmosphere. But, since the 1960s, it has had a growing — and increasingly unsustainable — presence in the planet’s waterways, as well.

The 1960s was when the use of chemical fertilizers began to take off. Over the years, those fertilizers washed into rivers, bays and, eventually, oceans, becoming a major contributor to coastal pollution and “dead zones.”

One of the world’s largest dead zones today stretches from the mouth of the Mississippi River west along Louisiana's Gulf Coast. In the Chesapeake Bay, an annual summer dead zone results in multiple fish kills a year. Meanwhile, airborne nitrogen pollution from vehicles and power plants is affecting inland, high-altitude lakes, according to a in last week's issue of the journal Science.

The runoff from farms and from urban and suburban communities carries excess nutrients that eventually settle into coastal ecosystems. These nutrients provide food for huge algae blooms that both form a layer preventing the oxygen in the atmosphere from reaching deeper water and, when the algae die, use up the water’s oxygen as they decompose, thus creating the numerous dead zones that now dot the world’s seas.

In the Chesapeake Bay, the federal government is starting to take action.

Following an by President Obama on May 12 directing the federal government to become more involved in the cleanup of the Chesapeake, the Environmental Protection Agency issued a on Monday for the cleanup.

The plan allows states to continue programs that have worked, but also holds them accountable for reducing nutrient pollution and sets up possible sanctions if they fail. In light of the slow pace of cleanup efforts thus far, it would usher in what EPA senior Chesapeake adviser J. Charles Fox has called “a new era of federal leadership” in those efforts.

Congress is also currently considering bills to reauthorize the Chesapeake Bay and Gulf of Mexico Programs of the .

Cities are part of the problem, but modern agriculture practices are the largest contributor of nitrogen, phosphorous and sediment to the Chesapeake Bay, Peter Hughes of the agricultural consulting firm Red Barn Consulting told the Senate Committee on Environment and Public Works on Monday.

Ann Swanson of the Chesapeake Bay Commission echoed that conclusion, noting that nearly one-quarter of the bay watershed's land is devoted to agricultural production. Agricultural runoff hasn't been given the attention or blame it deserves, she said.

“While the states have made significant progress with point sources, we have not been successful with reducing the more diffuse non-point sources of nutrient pollution entering the bay,” Swanson said. “When one considers the vast and diverse nature of these pollution sources across the bay’s 64,000-square-mile watershed, it is not hard to see why we have fallen short in this area.”

Much like climate change, the effects of a nutrient-overload of the planet’s waters have only begun to be felt recently and come at the hands of human activity.

Likewise, the effort to contain the amount of nutrients in water has strong echoes of that to contain the amount of carbon in the air. “We must reduce the average total loads of nitrogen and phosphorus pollution to no more than 175 million pounds and 12.8 million pounds per year, respectively,” says the Chesapeake Bay Foundation’s 2008 .

Nitrogen in fertilizers is captured from the vast amount in the air around us, and it can be returned to the air by bacteria in soil and water that convert it into gas — a process called denitrification. But U.S. waterways are becoming nitrogen-saturated, scientists .

Denitrification also has a drawback: It produce nitrous oxide, a powerful greenhouse gas that the Intergovernmental Panel on Climate Change estimates has the global warming power of carbon dioxide over a 100-year period. It is the third largest contributor to climate change, behind carbon dioxide and methane.

Nitrous oxide can be produced naturally as part of the nitrogen cycle, but human activities have led to a sharp increase in its emission. They have pumped far more nitrogen into waterways than the life there knows what to do with. In the case of fertilizer, nitrogen for soils — and thus for food — which is naturally converted into biologically absorbable forms by bacteria in plants like legumes, is instead being mass produced in factories and added to farmland.

A September study in the journal called the disrupted nitrogen cycle one of three human-caused phenomena that threaten the habitability of the Earth.

“The rate at which N2 is removed from the atmosphere and converted to reactive nitrogen for human use,” say the study’s authors, is one of the “rates of change that cannot continue without significantly eroding the resilience of major components of Earth-system functioning.”


See also:

Organic Farming Yields Far Better Crop Resistance and Resilience

Food Production Can and Should Step Away from the Fossil Fuels

US Government Still Promoting Use of Coal Ash on Crops

Why Is the Media Afraid to Tackle Livestock's Role in Climate Change?


(Illustration: , NASA/GSFC)


Great post, really interesting stuff.

I agree with Miya, it's hard to see how the nitrogen levels are going to come down in the next few years. It's crazy to see that there's such an issue which really doesn't get enough coverage.

Obama's New Initiative

It is fantastic that the new American president is really pushing cause for concern on subjects such as this, especially after the destruction that was caused by the former president around the world. It is just as important to promote awareness and contribute efforts towards tree replanting initiatives in the rain forests, as trees play a vital part in the nitrogen cycle. Strategic replanting and felling could create balance for the current state of nitrogen gas saturation in certain areas, and under very precise scientific scrutiny and study could provide beneficial and measurable results.

Very informative

This is very informative. I never really knew that nitrogen posed this much of a problem.

disrupted nitrogen cycle

It produce nitrous oxide, a powerful greenhouse gas that the Intergovernmental Panel on Climate Change estimates has 298 times the global warming power of carbon dioxide over a 100-year period.

298 times ??
its unbelievible man.

No time to waste

The post has been very informative, but will it really be put to use. I don't see level of nitrogen coming down in next few decades. Like you said even denitrification is not of much help as the end product its going to produce would either be nitrogen gases or ammonium, both are as harmful as nitrogen itself. Reduction of CO2 and nitrogen comes as a package deal, if we reduce one using renewable sources of energy other is automatically reduced, this is true as far as industries are concerned but to reduce agricultural production of nitrogen, we will have to cut down on fertilizers and make our way towards organic farming, as nitrogen is amply produced naturally by leguminous plants and there is no way we can help that.

nitrogen is the new carbon

Thanks for this informative post! I work with nitrogen scientists and am painfully aware of how under-reported the issue is. thanks for helping shine the light on this pressing global challenge. readers interested in learning more about the myriad issues surrounding nitrogen can read the basics (and the not-so-basics, but told in plain language) here: .

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