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Fate of Plastics in Oceans Fate of Plastics in Oceans

Tony L. Andrady PhD

Research Triangle Institute Durham, NC 27709

Fate of Plastics in the Oceans

Anthony L. Andrady

January, 2004

Research Triangle Park, North Carolina

Degradation Degradation: two definitions : two definitions… …. .

1. Weakening of the material and disintegration into small pieces.

• end point

polymer particles.

• Photodegradation – relatively quick.
• 2. Complete chemical breakdown of the plastic or

mineralization

• Polymer + O2

CO2 + water

• Biodegradation. Very slow.

Factors Causing Breakdown of Plastics Factors Causing Breakdown of Plastics

UV radiation in sunlight

[290-400 nm]

Slow thermal oxidation

[10-20°C rise doubles rate]

Hydrolysis Biodegradation

UV UV-

• Induced Degradation

Induced Degradation

Why it is ineffective in the ocean

• available only to plastics less denser than water

not for nylons, plastics in crab pots, weighted derelict gear)

• available only prior to fouling of the surface.
• rate of breakdown increases with temperature.

(significant on land but greatly reduced at sea)

Density of Plastics Found in the Ocean Density of Plastics Found in the Ocean

• Gear-related plastics
• polyethylene [0.92-0.97]
• polypropylene [0.91]
• nylon [1.14]
• polyester [1.38]
• Packaging-related plastics
• polyethylene, polypropylene
• PVC
• polyester
• polystyrene (styrofoam) [<0.2]

Density of Sea Water {T, Salinity, pressure} ~ 1.025

Measuring Disintegration by Measuring Disintegration by “ “Embrittlement Embrittlement” ”

L

Extensibility = [L-Lo]/ Lo

Lo

Plastic is said to be embrittled when extensibility is < 5% Tensile strength (kg/sq.cm) is the force pre unit area at breaking point. Break

Extensibility of Polypropylene Tape Extensibility of Polypropylene Tape

0.0 2.5 5.0 7.5 10.0 12.5 15.0 25 50 75 100

Duration of Exposure (months) SEA AIR

Breakdown is Slower at Sea Breakdown is Slower at Sea

10 20 30 40 50 60 70 80 90 100

Polyethylene sheet Polypropylene tape Latex Balloons Styrofoam

6m 12m 6m 10m Percent Change in Extensibility

Biofouling Biofouling

Density Changes Due to Fouling Density Changes Due to Fouling

Photodegradable Six Photodegradable Six-

• pack Rings

pack Rings

4 8 12 16 1 10 100 1000

IN AIR FLOATING AT SEA WEEKS OF EXPOSURE

Molecular Weight at Molecular Weight at Embrittlement Embrittlement

Weeks Extensibility %

• Mol. Weight

X 1000 (g/mol)

775 (34) 223.0 3 54 (6) 67.3 6 46 (6) 45.1 9 24 (9%) 34.7 13 25 (4) 38.3 16 18 (3) 35.0 Embrittled

Embritlled plastics

avoid entanglement

Also avoids distress

from ingestion

The particles can

still be ingested

Residual particles

are still polymeric

Degradation Degradation: two definitions : two definitions… …. .

1. Weakening of the material and disintegration into small pieces.

• The end point is polymer particles.
• Photodegradation – relatively quick.
• 2. Complete chemical breakdown of the plastic or

mineralization

• Polymer + O2

CO2 + water

• Biodegradation. Very slow.

Why Insist on Mineralization? Why Insist on Mineralization?

* Equitable protection of the marine

ecosystem!

* Potential impact of plastics debris

• n the marine food web
• potential for biotransfer of toxins
• incomplete data

Virgin Resin Pellets in the Ocean Virgin Resin Pellets in the Ocean

Mato Mato et.al., et.al., Env Env. . Sci Sci. . Technol Technol., ., 35, 318 35, 318-

• 324 (2001)

324 (2001)

Plastic Resin

Float

Partitioning of Pollutants Partitioning of Pollutants

Pollutant C (ng/g) Log K’ (PP/Seawater) PCB 138,160 8.3 6.06 PCB 132, 153 7.9 6.19 PCB 187 1.8 5.73 PCB118 8.7 5.71 PCB 110, 77 11.2 5.63 PCB 105 6.0 5.77 Σ all PCB 117 5.37 DDE 3.1 5.44 Nonyl phenol 8.9 4.92

Water column

At equilibrium

Water column Adams (2002) - PCB#52 and Pyrene

• Log K ~ 4-6 (polyethylene)

Zooplanktons and Plastic Particles Zooplanktons and Plastic Particles

• Euphasia pacifica

Particle size can be

small enough to be ingested

Will they eat it?

Field study with Professor

Alice Aldredge

Polyethylene in Zooplankton Polyethylene in Zooplankton

Plastic in Fecal Pellet Plastic Particles in gut

• 1. Average particle size = 20 microns
• 2. Fresh zooplankton sample tested in a container

Zooplankton Zooplankton Calanus pacificus

Calanus pacificus Plastic in Fecal Pellet Plastic Particles in gut

• 1. Average particle size = 20 microns
• 2. Fresh zooplankton sample tested in a container

Zooplanktons and Plastic Particles Zooplanktons and Plastic Particles

• Zooplanktons can ingest

<20 micron particles.

Given a choice between

staple algae and plastic these showed no preference.

Physiological effects of

such ingestion are not known

Field study with Professor

Alice Aldredge

Plastics in the food web Plastics in the food web

Derelict Fishing Gear Plastic Particles Breakdown

• Plastic

Particles + Pollution Pollution Contamination

• Zooplankton,

Krill, Etc.

?

Ingestion

A Likely Pathway

Predation

• Higher

Marine Animals Bioavailability

?

Entry Into Food Web

What we need to find out What we need to find out

1.

Rates of biodegradation of plastics after embrittlement.

2.

Consequences of ingestion of small particles of plastics by zooplanktons and other invertebrates.

3.

Concentration of environmental pollutants by plastics.

4.

The bioavailability of toxins concentrated in plastics to the food web?