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Old 20-10-2019, 08:57   #1
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Concerning microplastics

Ran across this, today.

https://pubs.acs.org/doi/pdf/10.1021...stlett.9b00532

Quote:
Sunlight Converts Polystyrene to Carbon Dioxide and Dissolved Organic Carbon
Collin P. Ward, Cassia J. Armstrong, Anna N. Walsh, Julia H. Jackson, and Christopher M. Reddy

ABSTRACT: Numerous international governmental agencies that steer policy assume that polystyrene persists in the environment for millennia. Here, we show that polystyrene is completely photochemically oxidized to carbon dioxide and partially photochemically oxidized to dissolved organic carbon.
Lifetimes of complete and partial photochemical oxidation are estimated to occur on centennial and decadal time scales,
respectively. These lifetimes are orders of magnitude faster than biological respiration of polystyrene and thus challenge the prevailing assumption that polystyrene persists in the environment for millennia. Additives disproportionately altered the relative susceptibility to complete and partial photochemical oxidation of polystyrene and accelerated breakdown by shifting light absorbance and reactivity to longer wavelengths.
Polystyrene photochemical oxidation increased approximately 25% with a 10 C increase in temperature, indicating that temperature is unlikely to be a primary driver of photochemical oxidation rates. Collectively, sunlight exposure appears to be a governing control of the environmental persistence of polystyrene, and thus, photochemical loss terms need to be included in mass balance studies on the environmental fate of polystyrene. The experimental framework presented herein should be applied to a diverse array of polymers and formulations to establish how general these results are for other plastics in the environment.
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Old 20-10-2019, 09:21   #2
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Re: Concerning microplastics

Interesting.

Different plastic types (polymers) have different toxicities, accumulate various contaminants to different extents, and also generally accumulate bacteria, viruses, chemicals and harmful algae.
Some polymers are soluble in water while the others are not.
Insoluble:
polystyrene (PS)
polyethylene (PE)
polypropylene (PPE)
polymethyl methacrylate (PMMA)
polyvinyl chloride (PVC)
polyisobutilene (PIB)
Water soluble:
polyethyleneglycol (PEG)
polyacrylic acid (PAA)
polyacrylamide (PAM)
polyvinyl alcohol (PVA)
Oxo-degradable plastics are conventional plastics that contain additives that promote the oxidation of the material under certain conditions. They are used in applications such as agricultural films, rubbish and carrier bags, food packaging, and landfill covers. They can break down into very small particles, potentially contributing to environmental contamination by microplastics.
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Old 20-10-2019, 11:35   #3
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Re: Concerning microplastics

This is such a more complex topic that the mainstream press can deal with. Gord is right, the term "plastic" is so generic as to be useless in any evaluation of risk/benefit.

There are plastics that float, and some that sink. I seriously doubt the ones that sink to the bottom of the ocean are significantly more of an hazard that the silica in the sand, on the other hand they will be there a long time. Plastics that float stay in the "biosphere" longer, but are also more exposed to the UV degradation. If the plastic degrades from a "macro plastic" to a "micro plastic" it doesn't magically stop there. In fact, micro plastics are even less stable because they have such a huge surface area relative to volume.

Finally, one thing that is NEVER mentioned is that many "plastics" contain a LOT of non-plastic.. Some "plastics" contain more inorganic "filler" like calcium carbonate ("limestone") or calcium sulfate (gypsum) than actual polymer, in the same way that our FRP boat hulls contain a large fraction by weight of glass along with the plastic. In a lot of studies that try to do a material balance on plastic in the ocean this fact is ignored by people who really should know better.

Like so many things, the impact of plastics on the environment is likely to be MORE significant than presented by people who make their living making plastic, and just as likely to be LESS significant than presented by people who make a living from donations and research grants. Always follow the money...

We have been on a lot of remote leeshores in the world. And there is a lot of plastic washed up, which I have to assume is a reasonable sample of the macro bits of plastic in the ocean. Commercial fishing gear is the most common by volume, shoes are probably the single most common consumer item. Despite looking, we have never, ever, seen a single plastic drinking straw. That is a silly place to waste effort at reducing pollution. It is a classic of making people feel good without having a useful impact.
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Old 21-10-2019, 20:17   #4
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Re: Concerning microplastics

Quote:
Originally Posted by billknny View Post
We have been on a lot of remote leeshores in the world. And there is a lot of plastic washed up, which I have to assume is a reasonable sample of the macro bits of plastic in the ocean. Commercial fishing gear is the most common by volume, shoes are probably the single most common consumer item. Despite looking, we have never, ever, seen a single plastic drinking straw. That is a silly place to waste effort at reducing pollution. It is a classic of making people feel good without having a useful impact.
I guess the type and quantities vary by location.
In Canada the shore-line cleanups have cigarette butts as the #1 identifiable plastic, drink bottles #2. Straws and stirrers #9.
Logically we should ban cigarette filters. They make the cigarettes more lethal and more convenient.
Banning plastic drink containers is a no-brainer but I suspect the various industries involved have too much influence.
Micro plastic contamination of our seafood is a very real thing so I don't think the sinking plastic is as benign as you think.
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Old 21-10-2019, 20:54   #5
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Re: Concerning microplastics

Quote:
Originally Posted by bcboomer View Post
I guess the type and quantities vary by location.
In Canada the shore-line cleanups have cigarette butts as the #1 identifiable plastic, drink bottles #2. Straws and stirrers #9.
Logically we should ban cigarette filters. They make the cigarettes more lethal and more convenient.
Banning plastic drink containers is a no-brainer but I suspect the various industries involved have too much influence.
Micro plastic contamination of our seafood is a very real thing so I don't think the sinking plastic is as benign as you think.
I get the whole virtue-signalling thing about cigarette filters (ex-smoker myself) but cellulose acetate *does* degrade in soil, in as little as 4-9 months. Not sure how long it lasts in seawater. Like another commenter, the majority of plastics I saw on remote island beaches, was fishing net and flip flop shoes. I see plastic bottles at sea along the eastern seaboard of the US, but not many. We chased down a silvery mylar "Happy Birthday" balloon last month, because it flashed so rhythmically my wife was convinced it was a distress signal. You could see that plastic literally a mile away.
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Old 21-10-2019, 21:58   #6
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Re: Concerning microplastics

[QUOTE=mabowers;3001032]I get the whole virtue-signalling thing about cigarette filters (ex-smoker myself) but cellulose acetate *does* degrade in soil, in as little as 4-9 months. Not sure how long it lasts in seawater./QUOTE]

I'm an ex smoker too, although unfiltered, but every thing I see says up to 10 years.

You might look at this study:
https://tobaccocontrol.bmj.com/content/20/Suppl_1/i25

Very toxic to fish
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