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Richard Coupe: Today we’re going to talk about the National Water-Quality Assessment
program and part of a component of that is our Agricultural Chemical Transport study.
This is a study looking at the effects of agriculture on water quality at seven different
sites across the country. And today specifically though we’re going to being talking about
an area in Northwest Mississippi, our Mississippi Alluvial Plain commonly referred to as the
Delta. And we’re going to talk to some farmers, were going to talk to some scientists and
we’re going to take a little bit of a tour of the Delta.
So Richard what have you been working on as far as the NAWQA Program?
Richard Rebich: Well, for the last couple of years I helped out with sparrow modeling
that the NWQA Program is doing. The team that I worked with help to develop a SPARROW model
for total nitrogen and total phosphorous in the south central United States.
Richard Coupe: So what does a SPARROW model do?
Richard Rebich: It relates water-Quality information that we collect in the field to landscape
characteristics, sources of a particular pollutant, and it also relates it to those things that
deliver those pollutants to a receiving stream.
Richard Coupe: So what would be the most important results or the most significant results that
you found from this study?
Richard Rebich: The one thing that I thought was really interesting was how much of the
nitrogen load was contributed by atmospheric deposition. It was greater than 40 percent.
So with the other sources of nitrogen and phosphorous the higher sources came from the
agricultural industry from fertilizer and manure inputs.
Richard Coupe: Does this relate to the Gulf hypoxia zone at all?
Richard Rebich: Yes, it would have a pretty good affect there. The hypoxia zone-- recent
studies are pointing towards nutrients as the reasons, and so we're in the southern
part of the United States or areas that contribute to the hypoxia zone, and we're able to see
this as we map the loads for our particular study area, so that was the other thing that
we did.
Richard Coupe: Great. Thanks.
Richard Coupe: Heather, what part of the Agricultural Chemical Transport study have you really found
to be interesting?
Heather Welch: I think it was more of a spinoff from that project. We started looking or we
were asked to see if we could use the data that we had collected to see if the biofuels
initiative had any impact on water quality and quantity in the Mississippi Delta.
Richard Coupe: What was the biofuels initiative?
Heather Welch: Well, it was implemented by Congress in 2006, and it was to push to make
gasoline used-- up to 15 percent of it needed to be ethanol, and in America it's corn-based
ethanol. So we were able to see that between 2006 and 2007 there was a large conversion
from cotton in the Delta over 450,000 acres were converted from cotton to corn the following
year in 2007.
Richard Coupe: So what were the significant results from this study?
Heather Welch: So the results were we found that in that switch from 2006 to 2007 we increased
I guess the loss of storage in the aquifer, and in the year 2007 we used more water than
we would have used had it been in cotton like the year before. Also using the SPARROW model
saw that we could be increasing the amount of nitrogen yield leaving from the Yazoo River
Basin into the Mississippi River and then on down to the Gulf of Mexico.
Richard Coupe: Thanks.
Heather Welch: So what is the most interesting thing that you've worked on in the Delta as
a part of ACT study?
Richard Coupe: I've been working on fate and transport of glyphosate. Glyphosate is a nonselective
herbicide used in the United States for crop production. It's been used in the 1970s, but
it really took off in the early 1990s when genetically-modified crops specifically corn,
cotton and soybean were modified so that you could use glyphosate for weed control. And
then the amount glyphosate being used has just jumped up enormously. There hasn't been
a lot of work on the fate and transport of glyphosate because it's very difficult to
analyze for, very expensive.
But we were able to do a two-year study at to different locations one in Iowa and one
in Mississippi looking at multiple-sized basins, looking at how the fate and transport of glyphosate
changed as you moved in different agricultural and climatic areas. And we were able to sort
of relate the occurrence of glyphosate to three different factors one being use, which
makes sense if you use it. If you use more of it you're going to see more of it, and
of course in Mississippi because of our warmer climate and our heartier weeds we probably
used more than they did in Iowa so we saw more.
Additionally, we saw it was related to hydrology or precipitation rainfall you need water to
move agricultural chemicals off the fields. So in areas where they have more runoff you'll
see more glyphosate, and the third factor was sort of the flow path or the route of
the water as it moves off the field and into the stream-- does it go through the ground?
or does it go through over the top of the landscape. This makes a difference because
landscape has a high affinity to adsorption to soil particles, and if it goes through
the ground it has a tendency to adsorb and you'll see less glyphosate in your stream
if the water gets there through the soil. That's been a very interesting study and it's
been quite well received.
Richard Coupe: So Jeannie tell us a little bit about what you've been doing for the Agricultural
Chemical Transport Study.
Jeannie Barlow: So I've been working on the role of groundwater / surface-water exchange
on the transport of agricultural chemicals in the Bogue Phalia basin.
Richard Coupe: And why is this important to study?
Jeannie Barlow: Actually at first we thought it wasn't important to study. We've sampled
the groundwater in the Delta and have never found much of any agricultural chemicals in
the groundwater. So the assumption was that there was very little interaction between
the surface water and the groundwater since the surface water always had agricultural
chemicals in it of some form. But what we found is that actually it's not the hydrology
that's preventing the exchange of groundwater/ surface water. It's the chemistry of our groundwater
system. So for example in our study area found that we actually were in connection with the
aquifer, and we were generally gaining and losing some movement of water both ways. But
it was the chemistry within the stream bed and the aquifer that was actually causing
nitrogen this example to be reduced in two.
Richard Coupe: So what are the major conclusions you found from this study?
Jeannie Barlow: We find that we have huge swings in both the direction of the movement
of water between the groundwater and surface water, and also that this has a fairly large
impact on the chemistry of surface water and could have impact on what we're finding in
the ground.
Richard Coupe: Okay, thanks.
Jeannie Barlow: Thank you.
Richard Coupe: Claire, what have you been working on as far as part of the Agricultural
Chemical Transport Study?
Claire Rose: I've been working on a paper regarding metolachlor movement throughout
the environment. Metolachlor is an organic chemical that's applied as an herbicide, so
it's usually applied before they plant- it’s pre emergent.
Richard Coupe: And where is the study area that you're looking at for this?
Claire Rose: So you have pretty good coverage of the United States. You have the Mississippi,
California in the San Joaquin Valley, we have study in Maryland and a couple in the Midwest.
We have Indiana and Nebraska, and all these areas that we were studying are agricultural
areas. So we wanted to understand how the agricultural chemicals that are applied to
increase the productivity of crops move throughout the environment after they're applied, where
they go and basically have a good idea of what's going on across the U.S.
Richard Coupe: So what would be the most significant results you've found so far?
Claire Rose: I've found that it's really interesting that a lot of the areas have similar allocations
of metolachlor and its degradates throughout the seven environmental compartments. But
where you apply metolachlor, where it's used, you are going to find it or its degradates
and you're going to find them in every single environmental compartment through which water
flows. So that's an important thing to keep in mind about chemicals in the environment.
Richard Coupe: That's great. Thank you.
Claire Rose: Thank you.
[End of Audio]
Duration: 11 minutes
scientist interviews 2 Richard Coupe, Richard Rebich, Heather Welch,
Jeannie Barlow, Claire Rose