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Lawn Nitrates

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On any given day, you'll see proud homeowners watering and fertilizing their yards, trying to cultivate a lush carpet of green grass. Or maybe they’re proudly watching you mow that lush carpet of green grass. In any case, as you'll learn in this Science Update, researchers are discovering that the perfect lawn might come at a price.


Transcript

A lawn that's a lab. I'm Bob Hirshon and this is Science Update.

At the State University of New York at Stony Brook, students are growing a ten foot by ten foot patch of lawn, and fertilizing it, just as any proud suburbanite might. But this swath of green is more than just decorative. According to Stony Brook geologist Gilbert Hanson, the groups are monitoring the lawn to see how much nitrate from fertilizer travels down into the groundwater. Hanson says nitrates in drinking water can be dangerous, especially for young children.

Hanson:
For young babies and for older people it causes what's called blue baby syndrome. And that is it interferes with your hemoglobin so that it cannot pick up oxygen. And it in some cases can kill babies.

He says that while nitrates do sometimes show up in suburban drinking water, it's not known whether they come from lawns, septic systems, or are left over from abandoned farms.

Hanson:
And we see inputs from all three. If it's from previous farming, it doesn't matter, because that water will disappear. But if it's from septic tanks and fertilizer then of course we're continually adding it to the groundwater.

So this study will help determine whether the perfect lawn could be hazardous to your health. For the American Association for the Advancement of Science, I'm Bob Hirshon.


Making Sense of the Research

As the report mentions, nitrates are especially worrisome for young babies, because they can cause "blue-baby syndrome." This happens because their bodies tend to convert the nitrate into nitrite. Nitrite prevents a blood protein called hemoglobin from picking up oxygen and shuttling it around the body. As a result, the babies suffocate and sometimes even die. Babies who are fed with infant formula, which is mixed with polluted tap water, are most vulnerable to this condition.

Hanson's team studied the problem on their experimental lawn using instruments called lysimeters. These are devices that are implanted below the surface of the lawn, and collect the water that passes through the lawn. By studying this water, they hoped to determine exactly how substantial the nitrate levels in the groundwater were, and whether the lawn fertilizers raised those levels significantly.

Hanson believed that if lawn chemicals were, in fact, polluting the groundwater, then the only reasonable solution was to start cutting them back. The other alternatives were importing water from somewhere else, or cleaning up the water with sophisticated chemical treatments. Both of these are expensive and logistically complicated.

Groundwater pollution has been linked to other environmental problems. For example, farm animal manure often washes into rivers and streams, polluting the water. Chemicals in agricultural fertilizers also can promote the growth of toxic algae, which produce poisonous chemicals that kill fish. And in the Gulf of Mexico, nitrate runoff triggers a process that starves the water of oxygen, making it impossible for most sea creatures to live there. Unfortunately, as the human and farm animal population continue to increase, so will these kinds of environmental hazards.

Now try and answer these questions:

  1. How can nitrates in drinking water impact health?
  2. Why do nitrates pose less risk if they are left over from previous farming practices?
  3. Why is this problem particularly serious for the residents of Long Island?
  4. Can you think of some other possible sources of groundwater pollution?
  5. Environmental problems often involve a clash of short-term needs with long-term consequences. Can you think of some other examples? What are the challenges in dealing with problems like this?

For Educators

The World Resources Institute's EarthTrends website includes succinct and up-to-date information on the sources and consequences of water pollution.

Take your students on an exploration of the EPA's Watersheds site to see where in the United States there are the biggest pollution problems.

Or try the Role of Plants in Water Filtration activity found on the EPA website, which describes a simple and inexpensive experiment that you and your students can do to demonstrate how contaminants can be removed from water.


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