Fate of Plastics in Oceans Fate of Plastics in Oceans Fate of - PowerPoint PPT Presentation

Fate of Plastics in Oceans Fate of Plastics in Oceans Fate of Plastics in the Oceans Tony L. Andrady PhD Research Triangle Institute Durham, NC 27709 Anthony L. Andrady January, 2004 Research Triangle Park, North Carolina

Degradation: two definitions : two definitions… …. . Degradation 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 + O 2 CO 2 + 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- -Induced Degradation Induced Degradation UV � 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 “ “Embrittlement Embrittlement” ” Measuring Disintegration by Extensibility = [L-L o ]/ L o L o L 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 100 SEA 75 50 25 AIR 0 0.0 2.5 5.0 7.5 10.0 12.5 15.0 Duration of Exposure (months)

Breakdown is Slower at Sea Breakdown is Slower at Sea 100 90 80 Percent Change in 70 Extensibility 60 50 40 30 20 10 0 Polyethylene Polypropylene Latex Balloons Styrofoam sheet tape 6m 12m 6m 10m

Biofouling Biofouling

Density Changes Due to Fouling Density Changes Due to Fouling

Photodegradable Six- -pack Rings pack Rings Photodegradable Six 1000 100 FLOATING AT SEA 10 IN AIR 1 0 4 8 12 16 WEEKS OF EXPOSURE

Molecular Weight at Embrittlement Embrittlement Molecular Weight at � Embritlled plastics Weeks Extensibility Mol. Weight avoid entanglement % X 1000 (g/mol) 0 775 (34) 223.0 � Also avoids distress from ingestion 3 54 (6) 67.3 � The particles can 6 46 (6) 45.1 still be ingested 9 24 (9%) 34.7 � Residual particles 13 25 (4) 38.3 are still polymeric 16 18 (3) 35.0 Embrittled

Degradation: two definitions : two definitions… …. . Degradation 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 + O 2 CO 2 + 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 Ocean Virgin Resin Pellets in the Ocean Mato et.al., et.al., Env Env. . Sci Sci. . Technol Technol., ., 35, 318 35, 318- -324 (2001) 324 (2001) Mato Float Plastic Resin

Partitioning of Pollutants Partitioning of Pollutants Pollutant C Log K’ (ng/g) (PP/Seawater) Water column 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 At equilibrium DDE 3.1 5.44 Nonyl phenol 8.9 4.92 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 Particles in gut Plastic in Fecal Pellet 1. Average particle size = 20 microns 2. Fresh zooplankton sample tested in a container

Zooplankton Calanus pacificus Zooplankton Calanus pacificus Plastic Particles in gut Plastic in Fecal Pellet 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 � � Ingestion Plastic Derelict Plastic � ? Breakdown Contamination Particles Fishing Particles + Pollution Gear A Likely Pollution Zooplankton, Pathway Krill, Etc. Predation � ? Entry Into Higher Bioavailability Marine Food Web Animals

What we need to find out What we need to find out Rates of biodegradation of plastics after 1. embrittlement. Consequences of ingestion of small particles of 2. plastics by zooplanktons and other invertebrates. Concentration of environmental pollutants by 3. plastics. The bioavailability of toxins concentrated in 4. plastics to the food web?