Is there a recognised definition of ‘Microplastics’ ?

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MichaelG.
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Is there a recognised definition of ‘Microplastics’ ?

#1 Post by MichaelG. » Wed Dec 04, 2019 11:22 pm

I have just read this, from Fox News

https://www.foxnews.com/science/oceans- ... e-realized

and I am utterly bemused.

How can quantitative surveys of ‘Microplastics’ have any credibility ?

MichaelG.
.

Note: The published paper is available via the link in the ‘News’ report.
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wporter
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Re: Is there a recognised definition of ‘Microplastics’ ?

#2 Post by wporter » Thu Dec 05, 2019 12:35 am

"How can quantitative surveys of ‘Microplastics’ have any credibility ?"

Why not?

When you read a simplistic summary of research in the popular press, sometimes it makes no sense. You will have to read the journal article to understand the constraints and methodologies involved, and to understand the conclusions. You certainly won't get any of that from Fox News.

MichaelG.
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Re: Is there a recognised definition of ‘Microplastics’ ?

#3 Post by MichaelG. » Thu Dec 05, 2019 9:17 am

wporter wrote:
Thu Dec 05, 2019 12:35 am
When you read a simplistic summary of research in the popular press, sometimes it makes no sense. You will have to read the journal article to understand the constraints and methodologies involved, and to understand the conclusions. You certainly won't get any of that from Fox News.
Yes, I am aware of that ... which is why I downloaded the paper.

However sensationalised the ‘Fox News’ summary might be ... there is a simple underlying fact stated by Brandon et al
Abstract
Microplastics (< 5 mm) have long been a concern in marine debris research, but quantifying the smallest microplastics (< 333 μm) has been hampered by appropriate collection methods, like net tows. We modified standard epifluorescence microscopy methods to develop a new technique to enumerate < 333 μm microplastics (mini-microplastics) from filtered surface seawater samples and salp stomach contents. This permitted us to distinguish mini-microplastics from phytoplankton and suspended particles. […]


My bemusement was due to the revelation that they found it necessary and appropriate to define a new sub-category of mini-microplastics [sic] when I had previously assumed that the existing broad definition of microplastics as particles less than 5mm meant what it said !!

It now appears that in much of previous research it meant “less than 5mm but greater than 333 μm”

I find that shocking

MichaelG.
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Hobbyst46
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Re: Is there a recognised definition of ‘Microplastics’ ?

#4 Post by Hobbyst46 » Thu Dec 05, 2019 9:27 am

MichaelG wrote:...
Thanks for posting this, Michael. I find the fluorescence analysis of tiny particles interesting.

Edit:
The classification by the original researchers of particles as <5mm, <333 um in the Introduction section of their article seems indeed to me non-decisive.
However, their aim is clearly defined. Citation:

"We aimed to isolate, identify, and quantify microplastics 5–333 μm in size, a subgroup of microplastics which we termed mini-microplastic."
I think that the "key" number of 333 um is based on a popular standard mesh size of the tow net.

The main challenge in that research was discrimination between plastics and other collected particles from the sea water according to fluorescence at different wavelengths. A fairly intriguing topic IMHO; and may I suggest, that at least some fun experiments along that line can be performed by hobbyists who own fluorescence microscopes, a boat and plankton nets, and a lot of spare time... (Bob ? ;) )
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MicroBob
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Re: Is there a recognised definition of ‘Microplastics’ ?

#5 Post by MicroBob » Thu Dec 05, 2019 3:00 pm

Hi together,
the collection of particles between 333µm and 5mm really is not useful to determine the scope of the micro plastic problem.
There may have been a cause for this selective fishing: Most plancton is below 333µm and one avoids a net full of algae and protozoa with a few plastic particles in between.
In my view smaller particles will be more likely to be eaten by us and do harm.

I will put this on my to-do list for fluorescence microscopy. It would be a good test to create micro plastic from specific plastics and check whether they can be identified by their fluorescence. With FIJI it might pe possible to count them in an image.

Bob

MichaelG.
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Re: Is there a recognised definition of ‘Microplastics’ ?

#6 Post by MichaelG. » Thu Dec 05, 2019 5:32 pm

Hobbyst46 wrote:
Thu Dec 05, 2019 9:27 am
Citation:

"We aimed to isolate, identify, and quantify microplastics 5–333 μm in size, a subgroup of microplastics which we termed mini-microplastic."
I think that the "key" number of 333 um is based on a popular standard mesh size of the tow net.
Agreed ... I think that much is clear

Perhaps I expressed my initial thoughts poorly, but my concern is that; in the light of this paper, it appears that many previous studies are invalidated [assuming that the definition of microplastic was plastic particles of less than 5mm] ... Which is why I asked the question.

MichaelG.

.

Edit: according to Wikipedia, the definition is attributable to NOAA
Microplastics are very small pieces of plastic that pollute the environment.[1] Microplastics are not a specific kind of plastic, but rather any type of plastic fragment that is less than 5 mm in length according to the U.S. National Oceanic and Atmospheric Administration (NOAA).[2][3] They enter natural ecosystems from a variety of sources, including cosmetics, clothing, and industrial processes.
Ref. https://en.wikipedia.org/wiki/Microplastics

... and I note this, from page 10 of reference [2]
While there is no requirement for a “lower bound” in size, as a practical matter defining microplastics as those that range between 5mm and 333μm recognizes the common use of 333μm mesh neuston nets commonly used in the field to capture plankton and floating debris.
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