Exploring Trends and Characteristics of Plastic Debris in the North Atlantic Ocean
Abstract
Much research over the past two decades demonstrates the ubiquity of that ocean plastic
pollution across the world’s oceans. Through these works, some of the environmental
consequences of plastic pollution have been well detailed while others remain un-quantified.
Though public awareness of ocean plastic debris has increased over the same period,
much is misunderstood. Many people still only think of this pollution as large “islands”
of trash and focus solely on the effects of large pieces of plastic on larger animals.
In reality, much of the plastic ocean debris consists of confetti-sized pieces distributed
throughout the oceans, with higher concentrations in the center of the major ocean
gyres at the convergence of the ocean surface currents. This study, as part of a larger
NSF-funded project, investigates a large dataset of smaller plastic pieces collected
from the North Atlantic between 1991 and 2007. It tracks how the size parameters (e.g.
area and mass) of different plastics found in the ocean vary with time and geographic
location. In a previous marine plastics study, Moret-Ferguson et al (2010) measured
longest-edge particle size, mass, and density of individual plastic fragments from
50 tows taken throughout the North Atlantic Ocean by Sea Education Association (SEA).
They found that for each sample area, both longest edge particle size and mass decreased
from the 1990s into the 2000s.
This project extends the Moret-Ferguson study to several other characteristics of
individual plastic fragments, revisiting the same large dataset of over 1000 plastic
pieces collected from the same 50 net tows over 16 years. A reevaluation of the data
shows that Polyethylene (PE) dominates the assemblages over all other polymer types
in ratios unexplained by plastic production data. It hints at a possible preferential
breakdown of Polypropylene (PP) over PE to sizes smaller than the mesh size of collection
nets. A slight decrease in mass over the time period between 1991-1995 and 2004-2007
is seen, but a firm conclusion on this point is not yet possible. An analysis of the
shape of plastic pieces demonstrates that the assumptions of a near-spherical or cubic
shape to microplastics in debris-tracking models can be reasonable. Tracking plastic
debris over geographic space shows a non-uniform mixture of plastic polymer and form
types within the North Atlantic, and a significant difference in size of plastic assemblages
north and south of 30°N. It also hints at changes in the makeup of plastic assemblages
with proximity to land. Finally, a descriptive analysis and glossary of terms was
developed to help classify plastic debris, and proved useful in identifying polymer
types under the microscope. Hopefully this framework can become a standard applied
throughout future analyses of ocean plastic debris.
Type
Master's projectPermalink
https://hdl.handle.net/10161/9570Citation
Collins, Theophilos (2015). Exploring Trends and Characteristics of Plastic Debris in the North Atlantic Ocean.
Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/9570.Collections
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