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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.


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]


Title: The Off-Continent Flux Project


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:

Suggest an update to the information/tags?

Streamflow (Set) RSS Media RSS USGS Data Grapher Tutorial - Introduction USGS Data Grapher Tutorial - Setting Up Your First Graph
In: Water collection

Tags: ArtHorowitz BedSediment DouglasHarned Metals Sediment SedimentFlux USGS WaterQuality


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