Fate of Plastics in OceansFate of Plastics in Oceans

Tony L. Andrady PhDResearch Triangle Institute

Durham, NC 27709

Fate of Plastics in the Oceans

Anthony L. AndradyJanuary, 2004

Research Triangle Park, North Carolina

DegradationDegradation: 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 PlasticsFactors Causing Breakdown of Plastics

UV radiation in sunlight[290-400 nm]

Slow thermal oxidation[10-20°C rise doubles rate]

HydrolysisBiodegradation

UVUV--Induced DegradationInduced Degradation

Why it is ineffective in the ocean- available only to plastics less denser than waternot 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 OceanDensity 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 ““EmbrittlementEmbrittlement””

L

Extensibility = [L-Lo]/ LoLo

Plastic is said to be embrittledwhen extensibility is < 5%

Tensile strength (kg/sq.cm) is the force pre unit area at breaking point.Break

Extensibility of Polypropylene TapeExtensibility of Polypropylene Tape

0.0 2.5 5.0 7.5 10.0 12.5 15.00

25

50

75

100

Duration of Exposure (months)

SEA

AIR

Breakdown is Slower at SeaBreakdown is Slower at Sea

0102030405060708090

100

Polyethylenesheet

Polypropylenetape

Latex Balloons Styrofoam

6m 12m 6m 10m

Percent Change in

Extensibility

BiofoulingBiofouling

Density Changes Due to FoulingDensity Changes Due to Fouling

Photodegradable SixPhotodegradable Six--pack Ringspack Rings

0 4 8 12 161

10

100

1000

IN AIR

FLOATING AT SEA

WEEKS OF EXPOSURE

Molecular Weight at Molecular Weight at EmbrittlementEmbrittlement

Weeks Extensibility%

Mol. WeightX 1000 (g/mol)

0 775 (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 entanglementAlso avoids distress from ingestionThe particles can still be ingestedResidual particles are still polymeric

DegradationDegradation: 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 on the marine food web

-potential for biotransfer of toxins

-incomplete data

Virgin Resin Pellets in the OceanVirgin Resin Pellets in the OceanMatoMato et.al., et.al., EnvEnv. . SciSci. . TechnolTechnol.,., 35, 31835, 318--324 (2001)324 (2001)

Plastic ResinFloat

Partitioning of PollutantsPartitioning 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 ParticlesZooplanktons 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 ZooplanktonPolyethylene in Zooplankton

Plastic in Fecal PelletPlastic Particles in gut

1. Average particle size = 20 microns

2. Fresh zooplankton sample tested in a container

Zooplankton Zooplankton Calanus pacificusCalanus pacificus

Plastic in Fecal PelletPlastic Particles in gut

1. Average particle size = 20 microns

2. Fresh zooplankton sample tested in a container

Zooplanktons and Plastic ParticlesZooplanktons 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 webPlastics in the food web

Derelict Fishing

Gear

PlasticParticlesBreakdown

PlasticParticles

+ Pollution

Pollution

Contamination

Zooplankton,Krill, Etc.

?Ingestion

A LikelyPathway

Predation

Higher Marine Animals

Bioavailability?Entry Into

Food Web

What we need to find outWhat 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?