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The Off-Continent Flux Project

Information presented is factual at the time of creation.
If no transcript and/or closed-caption is available, please notify us.
[Music playing]





Art: This afternoon we're out on the





Neuse River in North Carolina collecting





bed-sediment samples. This is part of a





large national project that's intended





to calculate and determine the concentration





and masses of sediment-associated





off-continent flux of a variety of





chemical constituents. We're sampling





the sediment because the sediment is a





major carrier for things like trace





elements, nutrients, and a number of





organic pollutants like DDT, and PCBs.





Ordinarily, we would use suspended sediment,





but it would take a very long time to get a





sufficient mass of it to work with. So,





we're using bed sediment as a surrogate,





but we're not using the entire component





of all of the bed sediment, we're just





looking at the less than 63-micron fraction.





Those samples that we're collecting





are representative cross-sectional ones,





so that we've collected aliquots as





we've gone across the stream bed and





composited it, so that it represents





the entire river cross section.





And ultimately, we'll be collecting the





same kind of material at 130 river sites





all around the coast of the United States,





starting in Maine and going to the tip





of Florida, going from the tip of Florida





all the way over to the Texas-Mexico





border. And then, from Baja California,





all the way up the west coast and into





Washington because we're also gonna





collect samples from rivers that





discharge into Puget Sound.



What's the bottom feel like?





Erik: Mud with a lot of clams.





Art: Oh good!





Erik: Or oysters.





Art: That's what I needed.





Michelle: So Art, what's this you're using to collect sediment samples with?





Art: This is a petite PONAR and it's spring





loaded, and what happens is as long as





I keep tension on the line, the springs





stay shut because the two bars keep the





thing in place. When I hit the bottom,





the spring pops out. And, when I pull





up, it closes and that's how I collect the sample.





Michelle: And about how much of the sediment layer do you get with it?





Art: Well, it depends on the bottom and





how heavy it is. If the bottom is fairly





soft, we probably go down about six to





eight inches. But, we're only trying





to collect the upper one to two centimeters.





We got something. Well, we got a big clam.





Erik: Is there a minimum amount that you need or?





Art: Well, we can do the analysis on





two grams or less, but I want a representative sample.





Figure, roughly by about where that post is





Erik: Okay.





Art: and we'll start there. We'll see what the water depth is.





Erik: Okay.





Michelle: So Art, what are your expected results from this study?





Art: Well, we ultimately will come up with





a mass and concentrations for all the constituents





that we're measuring. Right now, approximately





260 megatons of sediment are discharged





to the Atlantic, Gulf, and Pacific. And,





those sediments contain high concentrations





of a variety of constituents. Some of





them are within a normal range, some of





them exceed those ranges. But, we won't





really know until we actually carry out





a chemical analysis on them.





The information we get from this will





give us a baseline level of chemical





transport, which can be used, in part,





to assess climate- change effects, so





it changes from climate change. It will





also help us identify those rivers that





have excessive concentrations and might





require additional monitoring.





One of the major aspects of this study is





to evaluate various factors that can affect





sediment chemistry. So, as part of this





study, we're collecting a lot of ancillary





data. We're collecting land-use





distributions within each basin, covering





such things as the amount of agriculture,





the amount that's forested, the amount





that's urbanized, the amount that's





undeveloped, and we're also looking at population density.





Previous work has shown that both the





population density and the amount of





urbanization, are the strongest or





single most important factors that





affect the sediment chemistry, and





also nutrient sediment chemistry.





At the end of this project, we will have





a series of calculated values that we





can compare against the actual measured





values in the samples we're collecting.





The calculated values will be first





baseline values, based on NAWQA bed-sediment





samples that were collected at 450 sites





around the U.S. The second will be based





on worldwide published averages for





suspended sediment. The third, will be based





on land-use distributions within each





basin. And then, the last will be based





on population density within each basin.





And, those calculated values will ultimately





be compared against the actual measured





values and hopefully, we'll have a





better idea of the factors that affect





sediment chemistry and we will actually





have values to evaluate those factors





against, because we're collecting real





samples that we're going to ultimately analyze.





Erik: You did it.





Art: It also looks like it's empty-- Totally clean.





It's about four feet. I don't think





you can hit it, well you might





be able to hit is with the paddle.





It's just sand.





We'll go downstream about a couple hundred yards.





Michelle: So Art, what do you think the





effects of climate change will be on the flux, sediment flux?





Art: Well, the two most significant effects





of climate change are going to be temperature





changes and changes in precipitation





patterns. Precipitation patterns are





going to affect the amount of sediment





that's being discharged because





it's a function of runoff, and





temperature changes will affect





weathering, which will affect the





chemistry of the sediment. So, both affects.





Michelle: How empty are we Erik?





Erik: Quite empty.





Art: Got sediment this time, not a lot,





but some. I'll take this and take a





duplicate and then we'll go home.





Done!





The major outcome of this exercise,





which will take about two years in





total, will be to establish a baseline





level for off-continent flux against





which we can measure subsequent changes





and hopefully, ascribe them to





climate effects or climate change.







[Music playing]







[End of Audio]

Details

Title: The Off-Continent Flux Project

Description:

Art Horowitz (U.S. Geological Survey) describes the U.S. Geological Survey study to estimate amounts of chemicals washed to the oceans from the continental United States.

Location: USA

Date Taken: 5/1/2011

Length: 12:00

Video Producer: Douglas A. Harned , National Water-Quality Assessment Program (NAWQA), USGS, North Carolina Water Science Center, Raleigh, NC


Note: This video has been released into the public domain by the U.S. Geological Survey for use in its entirety. Some videos may contain pieces of copyrighted material. If you wish to use a portion of the video for any purpose, other than for resharing/reposting the video in its entirety, please contact the Video Producer/Videographer listed with this video. Please refer to the USGS Copyright section for how to credit this video.

Additional Video Credits:

Art Horowitz: Scientist

Douglas Harned: Producer, Video, Editor

Michelle Moorman: Video

Erik Staub: Video

File Details:

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