Public Lab Research note

How many pellets are actually at the Dow outfall, compared to the Bianca Spill?

by eustatic | November 03, 2020 02:10 03 Nov 02:10 | #24913 | #24913

USES and others say that pellets are "unrecoverable." I wanted to see how many pellets I could recover across from the source, the Dow Taft plant, which manufactures polyethylene.

I did three "nurdle patrol" 10-minute method, picking up pellets by hand. I do think there's a limit to how many pellets you can pick up in 10 minutes, so I also recorded the distance as a measure of density.

Upstream of the Dow facility, I only collected 6 pellets in 131 m. Directly across from Dow, I collected 66 pellets in 183 m. This is 7 times as many per meter, and about 7 times as many per minute. Further downriver, I collected 96 pellets in 29.5 meters.

This is 70 times the amount from upstream, and ten times the amount from the other end of the spillway, although it's the same pellets per minute as the second transect.

But even 96 pellets is many fewer than the minimum pellets collected during the Bianca spill. Hand-collected pellets are at 250 pellets in 10 minutes, all collected within 1 meter. This is at least twice the amount of pellets downstream from Dow, more than three times the amount of pellets per minute, and 70 times the number of pellets per meter.

Using brooms, we've been able to collect thousands of nurdles in 10 minutes.

| | date| time| t| lat| long| Parish| Bank| pelletsN| distance (m)| Pellets/m|

| | 1| 10/21/2020| 3:16| 10| 29.99958| -90.4537| St Charles| East| 6| 131.77| 0.05| 0.60| | 2| 10/21/2020| 3:28| 10| 29.99955| -90.5435| St Charles| East| 66| 183.66| 0.36| 6.60| | 3| 10/21/2020| 4:03| 14| 29.99815| -90.4303| St Charles| East| 96| 29.5| 3.25| 6.86|

Here's a photo of the second transect, and the first and second transects on my separating table::

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second survey

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First and second sets.

upstream of Dowimage description

Here's the third set, downstream from Dow.

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pellets on the tide line.

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Third set, off Apple St in NORCO.

The other thing of note is the variety of pellets compared to the Bianca collections.

There is a larger, softer plastic pellet I have not been able to find in the typology, whichi s about 7mm wide on the longest axis.

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Softer nurdle downstream from Dow



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@eustatic "I do think there's a limit to how many pellets you can pick up in 10 minutes, so I also recorded the distance as a measure of density."

Do you have a datasheet you used for this activity you can share? What was your method for measuring the distance? UW COASST Marine Beach Debris Monitoring has a pacing measurement for example with instructions.

And holy smokes! Thanks for sharing the Slater Museum at University of Puget Sound resource -- they're in my area! I didn't realize they're doing a Nurdle Project. Checking it out now.

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