Fate of Plastics in Oceans

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Fate of Plastics in Oceans
Plastics in the Oceans A technical perspective
Tony Andrady September, 2005

• Tony L. Andrady PhD
• Research Triangle Institute
• Durham, NC 27709

RTI International, Research Triangle Park, North
Carolina 27709
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Plastics and the Future

• The growth rate of plastics in the US has been
  phenomenal!
• 115 billion pounds in 2004
• As a material plastics offer some unique
  advantages in numerous applications including
  marine applications.
• Global population trends and economic
  considerations predict that plastics production
  and use will increase in the future. This will
  invariably create an increasing amount of
  plastics waste.
• The challenge is to minimize the component
• of that waste that ends up in the oceans.

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Specific Gravity of Plastics
Density of Sea Water T, Salinity, pressure
1.025
Negatively buoyant plastic materials impact the
benthic environments and generally are not
encountered in beach clean-up or surface water
counts.
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Breakdown of Plastics in Oceans

• UV radiation in sunlight 290-400 nm
• Slow thermal oxidation
• Hydrolysis (degradation by water)
• Biodegradation

Breakdown and disintegration of plastics floating
in the marine environment is very much slower
than that exposed on land.

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ASTM D5437-93 Exposure Method
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Extensibility of Polypropylene Tape
 
   
 
lo
l

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Reasons for Retardation

• Lower sample temperatures
• No chance of heat build-up in sample
• Lower temperature much slower oxidation
• Also, negatively buoyant material gets no UV at
  all
• Biofouling of Sample Surface
• Sample surface covered by foulants
• Effective shielding from UV radiation

12 22 33 C
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Extensibility as a Measure
Percent Change in Extensibility
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Molecular Weight at Embrittlement

• Enhanced photodegradable polyethylene in Miami
  (FL)
• Embritlled plastics avoid entanglement
• The particles can still be ingested
• Possible ingestion-related distress to lower
  organisms
• Residual particles are still polymeric. No
  mineralization has occurred. The material does
  not participate in the carbon cycle

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Photodegradable Six-pack Rings
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Enhanced Photodegradation
POLYETHYLENE
PHOTODEGRADABLE
Low molecular weight residue
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Microplastics Debris

• What is known about how plastics degrade in the
  environment strongly suggest that microplastics
  would be a product of disintegration.
• Microplastics (20 microns in diameter) observed
  both in the sediment (Thompson, 2004) and in
  surface waters (Moore, 2003)
• What is the impact of microplastics on filter
  feeders and the zooplankton population?
• 99 percent of marine species are benthic. What is
  the impact of microplastics on these?
• What is the role of microplastics in transferring
  invasive species within the marine environment
  Murray, 2000

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Zooplanktons and Plastic Particles

• Euphasia pacifica
• Particle size can be small enough to be ingested
• Will they ingest polyethylene?

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Polyethylene in Zooplankton
Plastic Particles in gut
Plastic in Fecal Pellet
1. Polyethylene particles of average particle
size of 20 microns 2. Freshly caught zooplankton
sample tested in a container
Pictures courtesy Professor A. Aldredge (Santa
Barbara)
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What we know.

• Plastics degradation at sea is almost exclusively
  via photodegradation and occurs much slower
  compared to that on land.
• Embrittled plastics products present little or no
  entanglement/ ingestion threat to higher marine
  animals.
• The disintegration sequence of plastics in the
  ocean generates plastics microparticles
• Microparticles concentrate organic compounds
  (including toxic compounds) present in sea water
• These microparticles can be readily ingested by
  some zooplanktons.

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What we do not know.

• Is there any serious impact due to ingestion of
  bioinert plastics?
• Will they ingest microplastics laden with
  concentrated chemicals?
• - Natural safety mechanisms exist for krill
• Pseudo-nitzschia sp (diatom in toxic and
  non-toxic forms)
• Krill fed on toxic diatoms stop feeding for
  awhile
• Are the chemicals bioavailable to zooplankton?
  Are there ecosystem level consequences?
• Can the chemical species flow up the food pyramid
  to human consumers?

Domoic acid
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Thank You for Caring!
We did not inherit this earth and its oceans from
our forefathers. We have merely borrowed it from
our children
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Thank You for Caring!
We did not inherit this earth and its oceans from
our forefathers. We have merely borrowed it from
our children
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Cassins Aucklet DA transfer pathway
Need to consume 67 of body mass/day of
krill Translates into 31 µg/g of toxin in bird
tissue Chicks 40g of food (adult 120 g/day) 10
31 µg/g FDA limit is 20 31 µg/g animal tissue
for humans.
(Ptychoramphus aleuticus )