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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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In: Water collection

Tags: ArtHorowitz BedSediment DouglasHarned Metals Sediment SedimentFlux USGS WaterQuality

 

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