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A comprehensive investigation of industrial plastic pellets on beaches across the Laurentian Great Lakes and the factors governing their distribution


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Industrial, pre-consumer pellets are a major type of plastics pollution found on shorelines worldwide. This study investigates the distribution and characteristics of plastic pellets accumulated on beaches of the Laurentian Great Lakes of North America and provides a “snapshot” of pellet distribution in a lake system that accounts for 21% of the world's freshwater reserves. We sampled pellets simultaneously from 10m² quadrats on 66 beaches and characterized the 12,595 pellets collected (average of 19.1 pellets/m²). Forty-two beaches contained pellets and 86% of the pellets were found on three beaches: Rossport (Lake Superior), Baxter (Lake Huron), and Bronte (Lake Ontario). The number of pellets on each beach was compared with factors hypothesized to control their accumulation. In general, positive correlations were found between pellet abundance and watershed population, number of plastic-related industries, and proximity to a river mouth, although for Lake Superior, abundance was related to a train spill that took place over 10 years ago. Beach grain size appears to be related to pellet abundance, with very fine sand, fine sand and medium sand containing the greatest number of pellets. All pellets were visually characterized based on size, color, shape, weathering, and distinguishing traits. The predominant color was white, oblate shapes were most common, and the main distinguishing trait was a dimple. Most pellets showed little evidence of weathering, with the weathered samples mainly from Lakes Erie and Ontario. Lake Ontario pellets were the most varied, with 6/7 shapes, 35/40 colors, and 21/25 distinguishing traits, indicating a wider range of pellet sources compared to the other lakes. Polymer compositions were mainly polyethylene (PE) and polypropylene (PP). Our results will lead to increased recognition of regional pellet pollution in the Great Lakes watershed, thereby motivating change during their production, transport and use.
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A comprehensive investigation of industrial plastic pellets on beaches
across the Laurentian Great Lakes and the factors governing
their distribution
Patricia L. Corcoran
,Johanna de Haan Ward
,Ian A. Arturo
, Sara L. Belontz
, Tegan Moore
Carolyn M. Hill-Svehla
, Kirsty Robertson
, Kelly Wood
, Kelly Jazvac
Department of Earth Sciences, University of Western Ontario, London, ON, Canada
Department of Statistical and Actuarial Sciences, University of Western Ontario, London, ON, Canada
Department of Visual Arts, University of Western Ontario, London, ON, Canada
Surface Science Western, University of Western Ontario, London, ON, Canada
Department of Studio Arts, Concordia University, Montreal, QC, Canada
Shorelines of the GreatLakes are littered
with industrial plastic pellets.
42 of 66 beaches contained pellets, for
an average of 19.1 pellets/m
Abundance increased with number of
plastic industries and proximity to
river mouths.
Variety was greatest on a beach in a wa-
tershed containing 112 plastic indus-
Pellets were most abundant on very
ne, ne, and medium sand beaches.
abstractarticle info
Article history:
Received 11 April 2020
Received in revised form 21 July 2020
Accepted 23 July 2020
Available online 25 July 2020
Editor: Damia Barcelo
Plastic pellets
Plastic industry
Laurentian Great Lakes
Pellet spills
River mouth
Grain size
Industrial, pre-consumer pellets are a major type of plastics pollution found on shorelines worldwide.This study
investigates the distribution and characteristics of plasticpellets accumulatedon beaches of the Laurentian Great
Lakes of North America and provides a snapshotof pellet distribution in a lakesystem that accounts for 21% of
the world's freshwater reserves. We sampled pellets simultaneously from 10m
quadrats on 66 beaches and
characterized the 12,595 pellets collected (average of 19.1 pellets/m
). Forty-two beaches contained pellets
and 86% of the pellets were found on three beaches: Rossport (Lake Superior), Baxter (Lake Huron), and Bronte
(Lake Ontario). The numberof pellets on each beach was compared withfactors hypothesized to control their ac-
cumulation. In general, positive correlations were found between pellet abundance and watershed population,
number of plastic-related industries, and proximity to a river mouth, although for Lake Superior, abundance
was related to a train spill that tookplace over 10 years ago. Beach grain size appears to be related to pellet abun-
dance, withvery ne sand, ne sand andmedium sand containingthe greatest numberof pellets. All pellets were
visually characterized based on size, color, shape, weathering, and distinguishing traits. The predominant color
was white, oblate shapes were most common, and the main distinguishing trait was a dimple. Most pellets
showed little evidence of weathering, with the weathered samples mainly from Lakes Erie and Ontario. Lake On-
tario pellets were the most varied, with 6/7 shapes, 35/40 colors, and 21/25 distinguishing traits, indicating a
wider range of pellet sources compared to the other lakes. Polymer compositions were mainly polyethylene
Science of the Total Environment 747 (2020) 141227
Corresponding author.
E-mail address: (P.L. Corcoran).
0048-9697/Crown Copyright © 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (
Contents lists available at ScienceDirect
Science of the Total Environment
journal homepage:
(PE) and polypropylene (PP). Our results will lead to increased recognition of regional pellet pollution in the
Great Lakes watershed, thereby motivating change during their production, transport and use.
Crown Copyright © 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
1. Introduction
The global proliferation of plastic debris has been widely docu-
mented in both aquatic and terrestrial environments. The rst thermo-
sets, synthetic materials that melt when heated and solidify when
cooled, were developed in the late 19th and rst half of the 20th centu-
ries. Of all thermoplastics produced, polyethylene (PE) and polypropyl-
ene (PP) are the most common (Andrady and Neal, 2009). Both PE and
PP are derived through polymerization of hydrocarbon monomers in
the presence of heat and a catalyst. Once formed, the plastic is cut into
small particles by a pelletizer and the pellets (also known as nurdles)
are then transportedto industries to be melted and extruded or molded
into common plastic products. Unfortunately, numerous pellets are lost
during production, transport and storage (Karlsson et al., 2018). Spilled
or discarded pellets make their way into drainage systems, circulate
through the surface waters of rivers, lakes, seas, and oceans, and are
eventually deposited along shorelines. Documenting, quantifying, and
characterizing pellets provides information that can potentially be
used to change policy or industry behavior in favour of the thoughtful
handling of these materials.
Plastic pellets have been reported from beaches across the globe for
over 45 years (e.g. Carpenter and Smith, 1972;Gregory, 1977;
Zbyszewski et al., 2014;Fernandino et al., 2015;Karlsson et al., 2018).
Identication of pellets thousands of kilometres from the nearest pellet
production or use facility (e.g. Corcoran et al., 2014) indicates that pellet
buoyancy results in long-range transport. If a pellet is encrusted with
minute biota (e.g. Carpenter et al., 1972), the potential for introduction
of invasive species is increased. In addition, pellets have been shown to
adsorb and release persistent organic pollutants (POPs) such as
polychlorinated biphenyls (PCBs), dichloro-diphenyltrichloroethane
(DDT), hexachlorocyclohexanes (HCHs), and polycyclic aromatic hy-
drocarbons (PAHs) (e.g. Mato et al., 2001;Rios et al., 2007;Ogata
et al., 2009;Heskett et al., 2012;Koelmans et al., 2016). International
Pellet Watch, initiated in 2005 by Hideshige Takada, shows that pellets
have been found in over 50 countries, proving that pellet pollution is
truly a globalissue ( Similarly,
The Great Nurdle Hunt, organized by UK charity FIDRA, aggregates
citizen-collected data on pellets. As of the time of writing, over 3000
Nurdle Huntshave taken place, with at least one on every continent
( Once in the environment, pellets
can be ingested by aquatic wildlife such as ocean sh, squid, and sea-
birds (e.g. Braid et al., 2012;Van Franeker and Lavender Law, 2015;
Miranda and de Carvalho-Souza, 2016). Although few studies focus on
the physiological effects of pellet ingestion, numerous investigations
show that microplastic (<5 mm plastic particles) ingestion can affect
feeding behavior, reproduction, and growth of aquatic organisms
(Chae and An, 2017).
Pollution of the Laurentian Great Lakes with plastic debris was rst
documented in 2011 in a study examining plastic particle distribution
and degradation along the shoreline of Lake Huron (Zbyszewski and
Corcoran, 2011). Subsequent investigations focused on the presence of
micro- and macroplastic debris in surface waters of the Great Lakes
and its tributaries (Eriksen et al., 2013;Baldwin et al., 2016;Lenaker
et al., 2019), shorelines (Hoellein et al., 2014;Zbyszewski et al., 2014;
Driedger et al., 2015), and benthic lake and river sediment (Corcoran
et al., 2015;Ballent et al., 2016;Dean et al., 2018;Corcoran et al.,
2020). Plastic pellets were components of the debris load in surface
water and beach studies, with very minor amounts reported from ben-
thic zones, as a result of their low density and high surface area.
Zbyszewski and Corcoran (2011) and Corcoran et al. (2015) showed
that pellets are major components of shorelines in the Great Lakes,
with as many as 33 pellets/m
(Baxter Beach, Lake Huron) and 21 pel-
(Humber Bay), respectively.
The overall objective of this study was to record a snapshotof the
distribution of plastic pellets along shorelines of the ve Laurentian
Great Lakes of North America; a lake system that may be considered a
smaller-scale, freshwater proxy for the world's oceans. The Great
Lakes have approximately 16,500 km of shoreline and hold 21% of the
world's surface freshwater reserves. An essential freshwater resource,
they are simultaneously the location of intense agricultural and indus-
trial activity, including signicant plastics manufacturing. Understand-
ing how pellets enter and are transported and distributed through the
lake system is essential in the reduction of pellet pollution.
In this study, we aim to determine the relationships between the
quantity, types and distribution of pellets in each lake to ascertain:
1) the inuence of plastic industries and watershed population, 2) the
inuence of spatial location with respect to proximity of river mouths
and major highways, and location within or outside bays, and 3) the in-
uence of depositional processes as related to beachgrain size. By statis-
tically examining these relationships, we convey the extent of pellet
pollution and its possible sources. Through this work, we strive to
raise awareness of the plastic pellet issue and to inspire policy develop-
ment in terms of proper handling of pellets throughout the supply
2. Materials and methods
2.1. Regional setting
The Laurentian Great Lakes are located in central North America,
straddling the boundary between Canada and the United States
(Fig. 1a). Covering an area of 244,000 km
, the Great Lakes system ac-
counts for approximately 21% of the world's surface fresh water and is
home to >30 million people (EPA, 2019). It is composed of the ve
main lakes Superior, Michigan, Huron, Erie, and Ontario. Each lake has
its own sub-basins (
greatlakesbasin.pdf) and unique water current patterns (Beletsky
et al., 1999;EPA, 2019).
2.2. Field sampling
A total of sixty-six beaches were surveyed for plastic pellets between
October 7th and 21st in 2018. The number of sampling locationsaround
each lake varied with lake size. Eighteen beaches were sampled on Lake
Superior, 15 on Lake Michigan, 14 on Lake Huron, 10 on Lake Erie, and 9
on Lake Ontario (Fig. 1b). Each lake was surveyed by two people, except
Lake Superior where two people surveyed 15 beaches and three other
people surveyed the remaining 3 beaches. In total, thirteen samplers
were involved in the eldwork, all were given detailed instructions
prior to departure, and all were familiar with the appearance of plastic
pellets. At each beach, samplers were instructed to i) take photographs
of the beach, strandline, and any plastic debris identied, ii) measure
the grain size of the natural sediment on the beach; if this proved dif-
cult, samplers collected sediment and brought it backto the lab for mea-
surement, iii) collect all plastic debris along the strandline. The latter
step was conducted bystretchinga 10 m measuring tape perpendicular
to the strandline and collecting pellets and other plastic debris within
1 m of the tape (Fig. 2a). Plastics from only the top 5 cm of the beach
2P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
surface were collected using bare hands if the sediment was wet. Metal
sieves were used if the sediment was dry and ne enough to pass
through the sieve openings, thereby leaving pellets and plastic debris
>2.5 × 3 mm remaining in the sieve. Pellets and other plastic debris
were stored in paper bags, and each bag was labelled according to
lake and beach name. The paper bags were brought back to the Univer-
sity of Western Ontario for pellet characterization.
2.3. Pellet characterization
A total of 508 pellets were randomly selected for chemical analysis
using Fourier transform infrared spectroscopy (FTIR) at Surface Science
Western, University of Western Ontario. Pellet surfaces were analyzed
using platinum attenuated total reectance (Pt-ATR) equipped with a
diamond crystal in the main box (Bruker Tensor II spectrometer). This
experimental setup allowed for analysis of an area of approximately
2mm×2mmtoadepthof0.65μm. The spectra were collected
from 4000 to 400 cm
with a resolution of 4 cm
. Some of thepellets
were also analyzed in cross-section. A total of 101, 99, 105, 100, and 103
pellets were analyzed from Lakes Superior, Erie, Huron, Michigan, and
Ontario, respectively.
Over the course of six months, the pellets were separated from other
plastic items and each pellet was characterized according to size, shape,
diagnostic trait, visible weathering, and color (Fig. 2bf). Information
concerning each pellet was entered into a database for statistical analy-
sis. The size of each pellet was measured with a ruler by nding the
plane of maximum projection, then measuring the long (l) and interme-
diate (i) axes and multiplying them together. The short axis (thickness)
of each pellet was not measured due to time constraints. The shape of
each pellet was categorized as either circular (l = i and pellet has no an-
gular edges), square (l = i and pellet has four angular edges), rectangu-
lar (l > i and has four angular edges), oblate (l > i and pellet has no
angular edges), cylindrical (l > i; pellet is a circular prism), cylindrical
irregular (l > i and pellet is not similar on all edges of the circular
prism), or irregular (l > i and pellet has no well-dened shape). Diag-
nostic traits (e.g. rims, lines, dimples) were visually determined and di-
vided into23 categories. Color was visually determined and divided into
38 categories. Because six people were involved in pellet characteriza-
tion, the categories for shape and diagnostic traits were cross-checked
among examiners. Color was not cross-checked and therefore repre-
sents the greatest source of characterization error given that different
individuals see color in different ways.
2.4. Spatial analysis
The number of plastic suppliers, distributors and users were deter-
mined from ThomasNet Supplier Discovery and Google Maps using
the search terms plasticsand polymerswithin a 100300 km radius
of each lake depending on the size of each lake basin. Coordinates were
assigned to each facility for mapping purposes.
Mapping and spatial analysis for Fig. 7 was performed using ArcMap
10.5. Spatial analysis methods for determining population density by
watershed were modied from Ballent (2016). Dissemination block
area boundary les were provided from Statistics Canada (2020) and
were joined to 2016 census data collected from the Canadian Census
Analyzer (2014). Dissemination block data were used for Ontario. The
prole variables selected from the population and dwelling counts for
2016 included previously normalized data, population density per
square kilometer. United States Census Bureau block-level data were
used from the 2010 US Census for each of the eight states in the Great
Lakes Basin. Watersheds were mapped at the USGS HUC-8 and Ontario
Tertiary levels, which are equivalent (Neff et al., 2005). Census data
were clipped to watersheds and were converted to raster using 100 m
cell size. Zonal statistics were used to determine the population per wa-
tershed, and watersheds were mapped using approximate quantiles.
Direct Drainageareas, which indicate islands and land adjacent to
the Great Lakes that were not incorporated into the watershed
shapeles were not considered in population analysis.
2.5. Statistical analysis
In order to determine whether pellet distribution was related to
river mouth proximity, any beach within 5 km of a river was given a
truevalue, with beaches >5 km from a river mouth assigned a
falsevalue for statistical analysis. Similarly, any beach sampled that
was located in a bay was given a truevalue, as opposed to beaches
outside bays, which were given falsevalues. Proximity to major high-
ways was determined using the Trans-Canada and 400-series (Canada)
Fig. 1. Spatialand pellet abundance details.A) Location of the Great Lakes system in NorthAmerica. B) Sixty-six sampling locationsalong Great Lakesbeaches, with relative abundances of
pellets indicated.
3P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
and Interstates (U.S.), and distances ranged from 1 to270 km. Figs. 2 to 6
were created in R version 3.6.0., using the package ggplot2 version 3.2.0
(Wickham, 2016). Fig. 1 was created using the package ggmap, version
3.0.0 (Kahle and Wickham, 2013).
3. Results
The total number of pellets collected from around the Great
Lakes was 12,595, for an overall average of 19.1 pellets/m
. A total
of twenty-four beach sampling quadrats contained no pellets
(Fig. 1b). The total number of pellets found on Lake Superior
beaches was 1341, for an average of 7.5 pellets/m
; 67% of the
beaches contained pellets. On Lake Michigan beaches, a total of
728 pellets were collected, for an average of 4.9 pellets/m
73% of the beaches containing pellets. A total of 7471 pellets were
but only 43% of the beaches contained pellets. Lake Erie beaches
contained 302 pellets, for an average of 3.0 pellets/m
beaches contained pellets. Finally, Lake Ontario beaches contained
2753 pellets with an average of 30.6 pellets/m
the beaches contained pellets. The overall pellet counts from
Lakes Huron, Ontario and Superior beaches are skewed as a result
of one beach on each lake accounting for 73% (Rossport Lake Supe-
rior), 96% (Bronte Lake Ontario), and 97% (Baxter Lake Huron) of
the pellets (Fig. 3). Removal of these outliers indicates that the
beaches sampled on Lake Michigan contained the greatest number
of pellets, followed by beaches on Lakes Erie, Superior, Huron, and
then Ontario (Fig. S1).
Fig. 2. Sampling site and pellet characteristics. A) Sampling pellets from a 1 × 10 m quadrat along the strandline of a Lake Superior beach. B) Examples of three distinct types of pellets.
Clockwise from top left: black, oblate; bl ack, cylindrical; black, oblate, rimmed. Note that the three types are of different sizes. C) Examples of the three most common shapes,
clockwise from upper left: two circular pellets (rie beads), two oblate, and three cylindrical. D) and E) Distinguishing traits of pellets sampled. Clockwise from top left in D: rimmed
and nodule; dimple and dirty; rough and broken; rimmed and hole; rimmed. Clockwise from top left in E: groove; dimple and nodule; lines and dirty; lines and dirty. F) Weathered
pellets with distinguishing traits such as dirty, rough and broken. The two lower left pellets are coalesced (joined together).
4P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario
Number of Pellets
Number of Pellets
Humber Bay
Huron Beach
Lakeview Park
Pigeon River
Port Austin
Port Clinton
Porter on the Lake
Presque Isle
Providence Bay
Temperance River
Traverse City
Ontario Park
Batchawana Bay
Cedar Beach
Sherman Park
Park Point
Ogden Dunes
Evangola Park
Port Stanley
Harbor Beach
Grand Marais Dunes
Grand Marais
Green Bay
Holiday Harbour
Private Pfeiffer
South Beach
Colchester Beach
Crescent Beach
Warren Dunes
Sunset Beach
Sodus Point
Katherine Cove
Holland State
Fairport Harbor
Bay View
Wasaga Beach
Colonel Samuel
James N Allen Park
Point Clark
Bay City
12th Street
Beach Name
Humber Bay
Huron Beach
Lakeview Park
Pigeon River
Port Austin
Port Clinton
Porter on the Lake
Presque Isle
Providence Bay
Temperance River
Traverse City
Ontario Park
Batchawana Bay
Cedar Beach
Sherman Park
Park Point
Ogden Dunes
Evangola Park
Port Stanley
Harbor Beach
Grand Marais Dunes
Grand Marais
Green Bay
Holiday Harbour
Private Pfeiffer
South Beach
Colchester Beach
Crescent Beach
Warren Dunes
Sunset Beach
Sodus Point
Katherine Cove
Holland State
Fairport Harbor
Bay View
Wasaga Beach
Colonel Samuel
James N Allen Park
Point Clark
Bay City
12th Street
Baxter Beach
Bronte Beach
Beach Name
Fig. 3. Pellet abundance per sampling quadrat on each beach. Lower graph includes all beaches and inset includes only those beaches with 200 pellets or less. Twenty-four beaches contained no pellets. Bars are color-coded according to lake. (For
interpretation of the references to color in this gure legend, the reader is referred to the web version of this article.)
5P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
3.1. Pellet compositions
The FTIR results show that 85.8% of the pelletsare composed of poly-
ethylene (PE), 8.5% are polypropylene (PP), 1.6% are thermoplastic
olen (TPO), and 1.0% are ethylene vinyl acetate (EVA) (Table S1). Poly-
styrene (PS), butadiene-styrene, acrylonitrile butadiene styrene (ABS),
nylon, PP/PE blend, and PE/Polyamide blend make up <2.2% of the pel-
lets. Two pellets were unknown polymers and 2 were minerals. Lakes
cylindrical irregular
ShapeDistinguishing Traits
Number of Pellets
Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario
Number of Pellets
white bubble inside
dimple, rimmed
dimple, nodule
dimple, seam
Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario
Fig. 4. Bar graphs illustrating the shapes and distinguishing traits of pellets found on the beaches of each lake. A) The most common shape found on all lakes was oblate, followed by
cylindrical, then circular. B) The most common distinguishing trait found on all lakes was a dimple, although 74% of the pellets contained no distinguishing trait at all.
6P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
yellow white
yellow pink
yellow orange
yellow grey
yellow green
yellow beige
white red
white brown
purple blue
pink brown
orange white
orange red
orange grey
grey white
grey purple
grey pink
grey orange
green white
green grey
green brown
cyan purple
brown red
brown orange
brown grey
blue grey
blue beige
beige grey
Number of Pellets
Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario
Proportion of Pellets
yellow white
yellow pink
yellow orange
yellow grey
yellow green
yellow beige
white red
white brown
purple blue
pink brown
orange white
orange red
orange grey
grey white
grey purple
grey pink
grey orange
green white
green grey
green brown
cyan purple
brown red
brown orange
brown grey
blue grey
blue beige
beige grey
Fig. 5. Graphsillustratingthe distributionof pellet colors foreach lake. A) The main pelletcolor found on beachesof all lakes was white.The second most commoncolor was black,although
black pellets were notfound on Lake Superiorbeaches. B) Lake Ontario beaches contained the greatest varietyof pellet colors with35/40 colors, whereas the lakewith the poorest variety
of pellet colors was Superior with only 5/40 colors. (For interpretation of the references to color in this gure legend, the reader is referred to the web version of this article.)
7P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
Erie and Ontario contained the greatest variety of polymer composi-
tions, whereas the pellets analyzed from Lake Superior were composed
of only PE and PP.
3.2. Pellet characteristics
Pellet types on each beach were assigned to pellets of the same size,
and with the same color, shape, diagnostic feature, and visible surface
weathering (Table S2; Fig. 2b). Pellet types on different beaches within
the same lake were compared only for Lake Superior. The sheer volume
of different pellets on beaches of the other four lakes prohibited type
comparisons for this part of the study. Pellet sizes varied between 2
and 42 mm
, with a median of 12 mm
and a mean of 13.7 mm
Mean sizes for each lake were 17.9 (Superior), 14.5 (Michigan), 13.4
(Huron), 14.5 (Erie) and11.9 (Ontario). A one-way analysis of variance
(ANOVA) was conducted to compare the lake effect on individual pellet
size, that is, to test that there is a signicant difference in mean pellet
size between lakes. This was signicant at the p < 0.01 level. The pre-
dominant pellet shape overall was oblate (Fig. 4a). Cylindrical, oblate,
and circular pellets were the most common shapes and were identied
in samples from beaches on all ve Great Lakes (Fig. 2c). A total of 9329
pellets had no diagnostic traits. Of the other 3266 pellets, dimples were
by far the most common (Lakes Ontario, Huron, Michigan and Supe-
rior), followed by lines (Lakes Ontario and Huron) and nodules (Lake
Ontario) (Figs. 2d, e, 4b). The sampled quadrats on the three beaches
with the greatest number of pellets show that Baxter Beach (Huron)
and Bronte Beach (Ontario) contained the largest variety of pellets
with respect to distinguishing traits, whereas Rossport beach (Superior)
mainly contained pellets with no distinguishing traits.
Pellet color, although a subjective category, shows that the majority
of the pellets on beaches in the Great Lakes Basin were white, followed
by black and grey (Fig. 5a). Lake Ontario, and specically Bronte Beach,
contained the greatest variety of pellet colors, with thirty-ve of the
forty color types (Fig. 5b). Pellets from Lake Huron and Lake Michigan
contained thirteen of forty colors, twelve of forty colors were repre-
sented in Lake Erie pellets, and Lake Superior pellets were of only four
color types (Fig. 5b). A total of 96.4% of the pellets on Lake Superior
beaches were white, oblate, 18 mm
and with no diagnostic traits
(Type 3405in Table S2). These pellets are the result of a train derailment
that occurred in 2008 near Terrace Bay, Ontario, which spilled pellets
into Lake Superior (
mystery-solved-182329).We also documented the relative degree of
weathering of each of 436 PE pelletsanalyzed by FTIR. Peaks in the spec-
tra between 1710 and 1775 cm
are increased absorption peaks,
which are indicative of oxidized material. Oxidation was classied as
low if there was little to no evidence of absorption peaks at about
1715 cm
relative to the characteristic PE peak height at around
1471 cm
(Fig. S2). The results in Table S1 indicate that 13.7% of the
pellets analyzed were weathered, with the greatest percentage of
weathered pellets in Lakes Ontario, Michigan and Erie. We also
attempted to visually note the number of pellets that appeared exten-
sively weathered, as determined through color change (fading or
yellowing), increase in surface roughness (e.g. pits and microfractures),
embrittlement, and abundance of external particles adhered to surfaces
(e.g. Zbyszewski and Corcoran, 2011;Brandon et al., 2016;Cai et al.,
2018)(Fig. 2f). Of the 15,595 pellets examined, 2.4% showed extensive
evidence of weathering (Table S3). By individual lake, the percentages
of pellets that were visually identied as weathered were <0.01% (Su-
perior), <0.01% (Michigan), 2% (Huron), 10.6% (Erie), and 0.04% (On-
tario). A comparison of the results indicates that visual
characterization of weathering is not as precise as chemical identica-
tion. This may be due to challenges in recognizing discoloration in pel-
lets with dark colors (e.g. black, blue).
The numberof pellets in each beach quadratwas related to grainsize
of the beach sediment. All samplers used the grain size classication
chart of Wentworth (1922), except for the very ne silt tocoarse silt cat-
egories, which were grouped into siltbecause only two beaches fell
into the category (Fig. 6). The mixedcategory was added to indicate
beaches with polymodal grain sizes (containing more than two), and
the organicscategory was added for the Pigeon River beach on Lake
Superior, which was completely covered in logs, sticks and leaves. The
results in Fig. 6 indicate that the majority of pellets were identied on
beaches composed of very ne sand, ne sand, medium sand and
mixed grain populations. These grain size categories also showed the
Grain Size
Pebbles + Cobbles
Very coarse sand
Coarse sand + Cobbles
Coarse sand
Medium sand
Fine sand
Very fine sand
Number of Pellets
Fig. 6. Boxplots displaying the relationship between pellet abundance and grainsize on beaches. The means forvery ne sand, ne sand, and medium sand were greaterthan other grain
size grades, which suggests that pellets preferentially accumulate on sandy beaches compared to silty, granular, pebbly and cobble beaches.
8P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
greatest ranges in number of pellets, especially ne sand and medium
sand. Therefore, although pellets appear to accumulate preferentially
on sandy beaches, some sandy beaches contained no pellets.
3.3. Population and plastic industry
High pellet abundances across the Great Lakes were correlated with
large population numbers (Fig. 7). We recognize that the general popu-
lation does not have access to pre-production plastic pellets, however,
distinguishing between industry proximity and watershed population
is challenging because most pellet manufacturers, suppliers and distrib-
utors are located in high population areas (Fig. 7). An exception is Lake
Superior, which has the lowest overall watershed populations of all the
Great Lakes, with only four of the twenty-ve watersheds containing
>50,000 people. Removal of the high pellet count at Rossport beach,
which is a direct result of the train derailment, leaves a total of 368 pel-
lets (2.0 pellets/m
). Furthermore, removal of all pellets from Lake Su-
perior beaches that originated from the spill (Type 3405 in Table S2)
leaves only 48 pellets (0.3 pellets/m
Lake Michigan pellet counts appear to be greater with an increased
number of plastic industries, particularly in the southeastern and south-
western portions of the lake (Fig. 7). The three northernmost sampling
locations and two southernmost sampling locations contained a mean
of 2 pellets(0.2 pellets/m
) and these were the regions with the lowest
number of industries.
Beaches along the northern half of Lake Huron contained no pellets
and twenty-one of those twenty-four watersheds had total populations
<100,000 (Fig. 7). In contrast, the southern half of Lake Huron (includ-
ing the southern coastline of Georgian Bay) is composed of twenty wa-
tersheds, nine of which have a population>100,000; pellet abundances
are substantially greater in the southern (67.1 pellets/m
the northern (0 pellets/m
) parts of the lake (Fig. 7).In particular, the lo-
cation with the highest pellet counts across all ve Great Lakes is in the
Sarnia region at the southern end of the lake. Although most of the plas-
tic industries in this region are found along the St. Clair River, which
ows south into Lake St. Clair, several creeksdraining the industrial sec-
tor ow into southern Lake Huron. We have visually identied numer-
ous pellets within and along at least one of these creeks. Although
pellets arewidely distributed across LakeErie, there appears to be no re-
lationship between pellet abundance and the location and density of
plastic industries (Fig. 7). Notwithstanding, the great variety in pellet
compositions and colors for Lake Erie samples compared to other
lakes supports the hypothesis that multiple industrial sources are
Of the twenty-two watersheds surrounding Lake Ontario, sixteen
have watershed populations >100,000 and two watersheds contain
Fig. 7. GISmap displaying pellettotals at each beach(yellow dots), and locations ofplastic distributors, manufacturers,and suppliers throughout the entire Great Lakes basin.Watersheds
are divided by thick black lines and total population per watershed is indicated in various shades of grey. Note how the pellet totals are greatest in Lake Huron and Lake Ontario. (For
interpretation of the references to color in this gure legend, the reader is referred to the web version of this article.)
9P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
>1,000,000 people. The high pellet count of 26.4 pellets/m
at Bronte
Beach falls within one of these watersheds (Fig. 7). Bronte Beach is lo-
cated within an approximately 160 km long corridor spanning two wa-
tersheds (Credit-16 mile, Humber-Don) that contain 415 identied
plastic industries (Fig. 7).
3.4. Location relative to bays, river mouths and major highways
The number of pellets at each sampling quadrat was compared with
proximity to rivers, location within bays, and proximity to major high-
ways. Thirty-one of the sixty-six beaches sampled are located within
5 km of a river, and these contained a mean number of 373 pellets
(Table S2). Notably, the three beaches with the highest pellet counts
(Baxter, Bronte, and Rossport) are all located within 5 km of a river.
For sampling locations with <200 pellets, the mean was 36. The
thirty-ve beaches located >5 km from a river had a mean of 20 pellets.
Atwo-sample,one-tailedt-test on the data containing all locations pro-
duces a p-value of 0.0747, indicating that there is a signicantly greater
amount of pellets on beaches within 5 km of a river mouth.
Of all of the beaches sampled, seventeen were located within a bay
and the mean number of pellets for these beaches was 21 (Table S2).
The 49 beaches located outside bays produced a mean pellet abundance
of 240. For locations with <200 pellets, the means for pellet abundance
within bays (21) and outside bays (29) were not statistically signicant.
A simple two-sample t-test on thedata containingall locations produces
a p-value of 0.4214, indicating that there is no signicant difference in
mean number of pellets on beaches within and outside bays. The num-
ber of pellets at each sampling location was also plotted against distance
to a major highway. The data points display no correlation between the
two variables (Fig. S3).
4. Discussion
The main objective of this study was to determine the factors con-
trolling the abundance and distribution of plastic pellets along beaches
throughout the Great Lakes watershed. The results of this study high-
light some of the major controls on pellet distribution during late Au-
tumn, 2018.
4.1. Inuence of plastic industries and watershed population
Not surprisingly, the data show that in the basin as awhole, high pel-
let abundance can be related to high watershed population and greater
numbers of plastic industries, as the two factors are positively corre-
lated. The two beaches with the greatest number of pellets (Bronte-
Lake Ontario; Baxter-Lake Huron) are spatially associated with a signif-
icant number of plastic industries, indicating their inuence on pellet
abundance. Lake Superior contained the beach with the third highest
number of pellets (Rossport), but this abundance is neither due to wa-
tershed population nor industry, as both factors are relatively negligible
for this lake. Instead, the pellets on Lake Superior beaches are a result of
a spill from a train derailment, indicating that pellets are not only lost at
the source or destination, but also in transit.
Interestingly, Lake Erie beaches contained the lowest number ofpel-
lets, but displayed a wide pellet distribution across its beaches.The plas-
tic debris distribution models of Hoffman and Hittinger (2017) and
Cable et al. (2017) suggest that most plastic pollution in Lake Erie
would accumulate in the water along the southern shoreline. However,
we did not see a correlation between our beached pellet data and the
surface water accumulation models. The lack of a statistical relationship
between pellet abundance, watershed population, and number of plas-
tic industries for Lake Erie may be a function of its short hydraulic resi-
dence (retention) time. According to the EPA (2019), Lake Erie has a
residence time of approximately 2.6 years, whereas in contrast,the res-
idence time for Lake Superior is 191 years.
There does appear to be a correlation between our pellet data and
Hoffman and Hittinger's (2017) modelled movement of plastic debris
for Lake Michigan. Both data sets show a greater accumulation of plastic
debris in the southern portion of the lake. Unlike Lake Erie, Lake Michi-
gan has a high hydraulic residence time of 99 years (EPA, 2019), and
therefore, residence time does not appear to control the low number
of pellets on Lake Michigan beaches overall. The low pellet numbers, es-
pecially for the high population watershed in which 12th Street beach
was sampled (with 0 pellets found), and wide distribution of pellets
across beaches of Lake Michigan may be a result of: i) the drainage of
Chicago's land into the Mississippi River system instead of Lake Michi-
gan through a complex natural and articial hydrological network
known as the Chicago Area Waterway System (CAWS) (Duncker and
Johnson, 2016), ii) a low overall release/spill of pellets, or iii) the pellets
being retained in surface water and not deposited on the beaches. Com-
paring the movement of surface water currents within each lake is be-
yond the scope of this project, but retention of pellets in surface
waters may be a function of the complexity of the current patterns
(e.g. number of gyres, current strength and speed) in different seasons
of the year.
Interestingly, there were statistically signicant differences in pellet
sizes between lakes. The largest pellets were identied on Lake Superior
and the smallest were found on Lake Ontario. We considered that this
could be related to a decrease in size with extended weathering asa pel-
let travels through the Great Lakes system, but the results show that
Lake Erie beaches contained the most highly weathered pellets and
their average size of 14.5 mm
is equivalent and greater than the size
averages for Lake Michigan and Lake Huron, respectively. Instead, the
average size differences, much like color and shape, probably reect
the producers' preferences, and have little to do with environmental
We investigated the characteristics of each pellet in order to identify
different pellet types on each beach, which would help nd clues
concerning source. The number of different pellet types on the most
pellet-rich beach of each lake included: 6/973 (Rossport-Superior),
426/7268 (Baxter-Huron), 79/167 (Sheboygan-Michigan), 58/127
(Fairport Harbor-Erie), and 1291/2635 (Bronte-Ontario). These results
suggest that there is an order of magnitude fewer sources of pellets to
Lake Superior than to Lake Huron, and that Lake Huron contains an
order of magnitude fewer pellet sources than Lakes Ontario, Erie and
Michigan. Lake Ontario, and specically Bronte Beach, contained the
greatest number of pellet types per total pellets. If plastic industries
are purposefully or inadvertently allowing pellets to spill into or near
tributaries in the Credit-16 mile and Humber-Don watersheds (which
ow into Lake Ontario), this could explain the wide range of pellet
types washing up on Bronte Beach. While large, instantaneous spills
have required cleanups (e.g. Terrace Bay, ON and Pocono Creek, PA), in-
dustries responsible for long-term, regular releases of pellets have not
had such requirements. However, a recent federal decision sets a new
precedent. For decades, the Formosa Plastics Facility in Point Comfort,
TX discharged plastic pellets and powders into Lavaca Bay despite
their permit allowing only trace amounts of oating debris
(Waterkeeper v. Formosa, June, 2019a). In the Final Consent Decree,
the US District Court required, among other remedial measures, that
past discharges of plastics had to be cleaned up, future discharges
abated, and that Formosa put $50 million USD towards Environmental
Mitigation Projects (Waterkeeper v. Formosa, Nov., 2019b).
4.2. Inuence of spatial location (river mouths, bays, highways)
Plastic pellets are normally transported from manufacturer to
processer by train, truck or ship. The pellets spilled from a rail car into
Lake Superior in 2008 continue to be deposited along the lake's shore-
line, but the long hydraulic residence time of the lake suggests that
the pellets may remain suspended in the water column for a century
or more. Plastic pellets spilled during transport via trucks (e.g. https://
10 P.L. Corcoran et al. / Science of the Total Environment 747 (2020) 141227
creek/article_970503dd-90a8-578c-8a51-bfe2f0214693.html), could
also make their way into drainage systems, creeks and other water-
courses, and eventually become deposited into large bodies of water.
We attempted to discern if a positive relationship exists between pellet
abundance on Great Lakes beaches and proximity to major highways.
The data indicate that no correlation could be found, which may be a
function of distance between source (truck) and sink (lake).
We also hypothesized that once pellets enter a lake, they would
preferentially accumulate inbays or other protected inlets. No statistical
support for this hypothesis wasevident inour data, which suggests that
the low density of pellets causes them to recirculate throughout each
lake, become beached during high onshore wind and wave events,
and then become transported back into the lake during high rain, lake
water or offshore wind events.
One factor that positively affects the abundance of pellets onbeaches
in our study isproximity toriver mouths. A statistically greater number
of pellets were found on beaches located within 5 km of a river mouth.
This supports models showing that rivers are one of the main pathways
transporting plastic debris from land to larger bodies of water (Lebreton
et al., 2017;Schmidt et al., 2017). Studies have also shown that
microplastics, including pellets, are abundant in tributaries owing
into the Great Lakes watershed (Corcoran et al., 2015;Baldwin et al.,
2016;McCormick et al., 2016;Lenaker et al., 2019), and therefore, trib-
utaries could represent major pathways for input of pellets to the lakes.
4.3. Inuence of depositional processes as related to beach grain size
The preferential deposition and/or retention of pellets on beaches
with sand-size sediment is likely a function of waveenergy in the depo-
sitional environment. Beaches composed of grains larger than medium
sand require relatively high energy, and cobble beaches, such as Mara-
thon (Superior) and Porter on the Lake (Ontario) contained no pellets.
Although high wave energy would transport pellets onto the beach,
that same energy redistributes the pellets back into the water. Beaches
composed of silt or organics (e.g. Port Clinton-Huron; Pigeon River-
Superior) also contained no pellets, but this is instead due to the wave
energy being too low for sufcient landward transport. Although it is
expected that grooming affects the distribution of pellets across a
beach, only 6 of the 66 beaches had been groomed prior to sampling
(Table S3), and therefore, we could not statistically test this hypothesis.
5. Conclusions and future work
The present basin-wide investigation of plastic pelletsrepresents the
largest simultaneous sampling campaign for pellets in the world. The
study emphasizes the major controls on pellet pollution in the Lauren-
tian Great Lakes. Factors that correlate positively with elevated pellet to-
tals are high watershed population numbers, high density of plastic
industries, <5 km distance from a river mouth, past evidence of pellet
spills, and beach grain sizes ranging between very ne and medium
sand. The low number of pellet types and compositions on Lake Supe-
rior beaches and the high number of types and compositions on Lake
Ontario beaches support the inuence of plastic manufacturers and
processers on pellet pollution. Ideally, pellet types across all ve lakes
should be compared in order to determine whether pellets are being
transported throughout the Great Lakes system. This is the next logical,
albeit lengthy extension of the present study. We are planning to survey
each sampling site and collect pellets in October 2023, to compare pellet
abundances from Year 1 and Year 5. The results will hopefully highlight
whether awareness and mitigation of pellet spills has improved. An ad-
ditional next step in this comprehensive investigation is to determine
whether the pellets on Great Lakes beaches have adsorbed persistent
organic pollutants (POPs) on their surfaces. The combination of plastic
debris and harmful pollutants could prove detrimental to aquatic ani-
mals and grazing birds in the various ecosystems of the Great Lakes.
Finally, the identication of shape, size, diagnostic trait, and color
provided in Table S2 could prove very useful for pellet manufacturers
and processers who wish to determine whether their products are con-
tributing to pellet pollution in the Great Lakes watershed.
Supplementary data to this article can be found online at https://doi.
CRediT authorship contribution statement
Patricia L. Corcoran: Conceptualization, Data curation, Formal anal-
ysis, Methodology, Project administration, Supervision, Visualization,
Writing - original draft. Johanna de Haan Ward: Formal analysis, Soft-
ware, Visualization, Writing - review & editing. Ian A. Arturo: Data
curation,Formal analysis, Investigation, Methodology, Software, Visual-
ization, Writing - review & editing. Sara L. Belontz: Conceptualization,
Data curation, Formal analysis, Investigation, Methodology, Software,
Visualization, Writing - review & editing. Tegan Moore: Conceptualiza-
tion, Data curation, Formal analysis, Investigation, Writing - review &
editing. Carolyn M. Hill-Svehla: Data curation, Formal analysis, Writing
- review & editing. Kirsty Robertson: Conceptualization, Data curation,
Formal analysis, Writing - review& editing. Kelly Wood: Conceptualiza-
tion, Data curation, Formal analysis, Writing - review & editing. Kelly
Jazvac: Conceptualization, Data curation, Funding acquisition, Writing
- review & editing.
Declaration of competing interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inu-
ence the work reported in this paper.
This investigation would not have been possible without help from
numerous individuals. We are grateful to Zhaoming Jiang, Jasmine Nieva,
and Nina Kozikowski for assisting with pellet characterization, and Lorena
Rios Mendoza, Christina Battle, Eeva Siivonen, Daniela Leon Vargas, Chia-
An Lin, and José Avalos for helping with beach surveys. Thank you to
Heather Davis who was involved with conceptualization of the project.
Thanks go out to Doug Woolford and Simon Bonner for their input
concerning statistical methods, and to Elliott Elliott for assisting with in-
dustry searches. Rebecca Sarazen conducted FTIR analysis of the pellets.
This work was supported by SSHRC Insight Grant #435-2017-1253 (Lead
Applicant: Kelly Jazvac). We acknowledge that the eldwork for this re-
search took place on the traditional territories of the Anishinabewaki,
Haudenosaunee, Huron-Wendat, Attiwonderonk (Neutral), Onondaga,
Odǫhwęja:deˀ(Cayuga), Onöndowa'ga:(Seneca), Wenrohronon, Erie,
Miami, Peoria, Meškwahki·aša·hina (Fox), Bodéwadmiké (Potawatomi),
oθaakiiwakihinaki(Sauk),Odawa,Petun,Metis,Očeti Šakówiŋ(Sioux),
Kiikaapoi (Kickapoo), and Menominee peoples. We are grateful to the In-
digenous peoples who have been protectors of the Great Lakes since time
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... Nevertheless, estuaries are known sinks for many environmental pollutants, and are subject to inputs of plastics from terrestrial, marine and freshwater environments (Vermeiren et al., 2016). Additionally, estuaries are often locations where urban centres develop, and human population densities have consistently been associated with plastic pollution (Browne et al., 2011;Nakao et al., 2020;Corcoran et al., 2020;Vetrimurugan et al., 2020). Of particular ecotoxicological importance is pollution by microplastics (plastics ≤5 mm, Arthur et al., 2009, Hidalgo-Ruz et al., 2012, because their small size allows for their uptake by a range of organisms throughout the food web (Au et al., 2017). ...
... At the scale of individual habitats, structural complexity caused by vegetation or rocky substrates, and the grain size and organic matter content of sediments have been highlighted as potentially influential factors of microplastic contamination (Vermeiren et al., 2016(Vermeiren et al., , 2021Enders et al., 2019;Corcoran et al., 2020;Harris, 2020;Bronzo et al., 2021). Nonetheless, the evidence has often been conflicting. ...
... Our results argue for explicitly accounting for sediment properties when comparing microplastic contamination levels among sites, similar to approaches commonly used to normalize assessments of sediment contamination for other pollutants (Kersten and Smedes, 2002). Specifically, we observed an exponential decrease in small microplastics with increasing grain size (Fig. 4), which is in line with experimental observations of greater retention of microplastics in fine compared to coarser substrata (Waldschläger and Schüttrumpf, 2020) and field observations on oceanic beaches (Vermeiren et al., 2021), lake shores (Corcoran et al., 2020) and estuarine sites (Enders et al., 2019). Despite this close relation between microplastic size and sediment grain size, it is noteworthy that there was no clear, direct relation between the size distribution profile of microplastics and sediment grains (the latter showing a much flatter distribution, Fig. 2). ...
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The high accumulation potential of estuaries for plastics, particularly microplastics, poses a threat to the high societal value and biodiversity they provide. To support a spatially refined evaluation of the risk that microplastic pollution poses to fauna utilizing estuarine sedimentary habitats, we investigated the distribution of microplastics (lower limit of quantification, LOQ = 62 μm) at the sediment surface of two dominant habitats, and subsequently compared microplastic burdens between two crabs species utilizing these habitats. Microplastics were dominated by low density polyolefins (45–50 %), comparable to the polymer composition of macroplastics. The vast majority (99 %) of microplastics were ≤1 mm, and increased exponentially (with an exponent of 2.7) in abundance at smaller sizes, hinting at three-dimensional fragmentation. Our results suggest that the presence of vegetation needs to be accounted for in risk assessments with small microplastics (≥62 μm and ≤1 mm) on average 2.6 times more prevalent within reed beds compared to mudflats. Additionally, sediment properties also play a role with an exponential decrease in small microplastic abundance at coarser sediments, increased organic matter content, and decreased water content. These results suggest that at specific locations, such as the study area, local sources can provide a substantial contribution to microplastics contamination. To translate these habitat- and site-specific differences into a risk assessment relevant for macroinvertebrates, ecological traits such as differences in feeding modes should be accounted for, as we found substantial differences in both size and abundance of microplastics in gastrointestinal tracts of two crab species, Chiromantes dehaani and Chasmagnathus convexus, with different feeding modes.
... Consequently, industrial additives can also be desorbed into the environment from plastic pellets (Hammer et al., 2012). Such debris are hazardous, as they strand and accumulate along coastal areas globally, which may promote the persistence of these contaminants in the environment (Teuten et al., 2009), especially on sandy beaches where these particles tend to accumulate (Moreira et al., 2016;Corcoran et al., 2020). ...
... Excirolana armata has high mobility and abundance on beaches with fine sands from Rio de Janeiro to northern Patagonia (Defeo et al., 1997;Lozoya et al., 2010). This is an important feature regarding model organisms for plastic pellets toxicity since there is a tendency for such particles to accumulate in sandy beaches with fine sands (Corcoran et al., 2020;Vermeiren et al., 2021). E. armata is also resistant to environmental stress (Laurino and Turra, 2021), and ecologically dominant, in terms of abundance throughout many sandy beaches of South America (Lercari and Defeo, 2003). ...
Microplastics, including plastic pellets, get stranded on sandy beaches. They persist in the oceans for long periods and frequently carry contaminants. Acute and chronic toxicity has been observed when marine organisms are exposed to high densities of plastic pellets in laboratory assays. We investigated the toxicity of beach-stranded plastic pellets on macrobenthic populations (Excirolana armata; Crustacea; Isopoda) under natural conditions (in situ). We simulated different pellets densities on a beach not contaminated by pellets, exposing isopods for 6 h and testing possible behavioral responses (i.e., vertical displacement) and mortality effects. No effect was observed on vertical displacement, but higher mortality was reported for organisms exposed to plastic pellets. The lowest pellet density tested commonly found in coastal areas was sufficient to trigger mortality. We also observed that lethargic individuals (near-death) were preyed on by the healthy individuals remaining in the test chambers.
... Although industrial runoff was commonly mentioned as a potential pathway in the literature ( Fig. 2A) and the presence of plastics in aquatic systems from industry is well documented (particularly from pre-production pellets (e.g., Carpenter and Smith 1972;Ogata et al. 2009)), very few studies have yet quantified microplastics in runoff and effluent from industry directly. Runoff from plastic industries has been reported as a source of microplastics to beaches (Zbyszewski and Corcoran 2011;Zbyszewski et al. 2014;Corcoran et al. 2020), sediments (Ballent et al. 2016), and rivers (Lechner et al. 2014;Lechner and Ramler 2015;Grbic et al. 2020;Li et al. 2020;Tsui et al. 2020). Other industry sectors, such as textile mills, have also been noted as sources to nearby waters . ...
Although many studies have focused on the importance of littering and (or) illegal dumping as a source of plastic pollution to freshwater, other relevant pathways should be considered, including wastewater, stormwater runoff, industrial effluent/runoff, and agricultural runoff. Here, we conducted a meta-analysis focused on these four pathways. We quantified the number of studies, amount and characteristics of microplastics reported, and the methods used to sample and measure microplastics from each pathway. Overall, we found 121 studies relevant to our criteria, published from 2014 to 2020. Of these, 54 (45%) quantified and characterized microplastics in discharge pathways. Although most focused on wastewater treatment plant effluent (85%), microplastic concentrations were highest in stormwater runoff (0.009 to 3862 particles/L). Morphologies of particles varied among pathways and sampling methods. For example, stormwater runoff was the only pathway with rubbery particles. When assessing methods, our analysis suggested that water filtered through a finer (<200 um) mesh and of a smaller volume (e.g., 6 L) captured more particles, and with a slightly greater morphological diversity. Overall, our meta-analysis suggested that all four pathways bring microplastics into freshwater ecosystems, and further research is necessary to inform the best methods for monitoring and to better understand hydrologic patterns that can inform local mitigation.
... In laboratory conditions, polymers were mostly used in irregular shape (21; 37.8%) mainly because primary pellets used under experimental settings are grounded with a grinder that turns them into a powder of irregular particles. The spherical shape is the second most used particle type (16; 28.1%) giving valuable information taking into consideration the high presence of pellets, spheres <5 mm that constitute the raw material for plastic products, in the marine environment (Corcoran et al., 2020). A total of 9 studies (15.8%) were carried out with polymers of different shapes and three of them focused on the characterization of plastic items of a specific area, hence, their shape was subjected to the litter identified in the study area. ...
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The marine environment has numerous impacts related to anthropogenic activities including pollution. Abundances of microplastics (MPs) and other pollutants are continuously increasing in the marine environment, resulting in a complex mixture of contaminants affecting biota. In order to understand the consequences, a review of studies analyzing combined effects of MPs and other types of pollutants in bivalves has been conducted as species in this group have been considered as sentinel and bioindicators. Regarding studies reviewed, histological analyses give evidence that MPs can be located in the haemolymph, gills and gonads, as well as in digestive glands in the intestinal lumen, epithelium and tubules, demonstrating that the entire body of bivalves is affected by MPs. Moreover, DNA strand breaks represent the first form of damage caused by the enhanced production of reactive oxygen species in response to MPs exposure. The role of MPs as vectors of pollutants and the ability of polymers to adsorb different compounds have also been considered in this review highlighting a high variability of results. In this sense, toxic impacts associated to MPs exposure were found to significantly increase with the co-presence of antibiotics or petroleum hydrocarbons amongst other pollutants. In addition, bioaccumulation processes of pollutants (PAHs, metals and others) have been affected by the co-presence with MPs. Histological, genetic and physiological alterations are the most reported damages, and the degree of harm seems to be correlated with the concentration and size of MP and with the type of pollutant.
Plastic waste can carry organisms such as bacterial pathogens and antibiotic resistance genes (ARGs) over long distances. However, only few studies have been conducted on the occurrence of ARGs in plastic waste from mangrove wetlands. This study evaluated the distribution characteristics and ecological risks of plastic waste from mangroves in the coastal areas of the South China Sea. The correlation between anthropogenic activity levels and abundance of ARGs in mangroves was evaluated. Transparent and white were the common colors of plastic waste in mangroves. The main shapes of plastic waste were foam and film. The predominant types of plastic waste order were as follows: polyethylene (30.18 %) > polypropylene (27.51 %) > polystyrene (23.59 %). The living area (LA) mangroves had the highest polymer hazard and pollution load indices of 329.09 and 10.03, respectively. The abundance of ARGs (5.08 × 108 copies/g) on the plastic surface in LA mangroves was significantly higher than that of the other mangrove areas. Furthermore, there was a significant correlation between ARGs and intI1 on the plastic surface in mangroves. Correlation analysis between the ARGs and intI1 showed that most of the ARGs were correlated with intI1 except for msbA. In LA mangroves, sociometric and environmental factors showed significant correlations with the absolute abundances of the four ARGs and intI1, indicating that anthropogenic activities may lead to changes in the amount of ARGs on plastic surfaces. Furthermore, the ARG storage of plastic waste from different mangroves was as follows: protected areas (3.12 × 1017 copies) > living areas (2.99 × 1017 copies) > aquaculture pond areas (2.88 × 1017 copies). The higher ARG storage of LA mangroves, with the smallest area, greatly increased its ecological risk. The results of this study can provide basic data for processes that influence the distribution of plastic waste and ARGs in mangroves.
Marine litter represents a threat to the marine environment, being estimated that around eight million items are discarded daily in the ocean. Monitoring marine debris became a relevant topic of research as marine litter is one of the descriptors of the Marine Strategy Framework Directive, for European Union's member states. Nevertheless, the patterns and processes governing the disposal of waste in coastal areas are still not clear. Our study relates characteristics of eleven coastal areas in Portugal (urbanization, slope, distance to an estuary, length, and type of substrate) to the type and abundance of marine litter found. A total of 7743 items were identified, with the main types of litter found being plastic (71.2%), paper (16.3%), and sanitary waste (9.1%). A clear spatial distribution pattern was observed, with more litter items recorded in the zone corresponding to the high tide line (2.3 items m⁻²). It was also verified that both beaches and seasons influenced the amount of litter found. Plastic, the dominant marine litter group, was abundant on the vast majority of beaches. It was possible to identify litter with land and sea origins. The litter with land origin came mainly from sanitary and sewage-related waste while the litter with marine origin came mainly from fisheries, including aquaculture.
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Microplastic pollution has become an environmental concern worldwide. In this study, the occurrence, abundance, and composition of microplastics (MPs) in sediment of the Vaal River, South Africa were assessed. Twenty-five sediment samples were collected from the Vaal River using a Van Veen grab sampler, samples underwent digestion, density separation, and filtration prior to physical and chemical analysis. Following the extraction, potential MPs were visually identified under a Nikon stereomicroscope, aided by chemical characterization using Raman spectroscopy. The results revealed 100% prevalence in sediment samples, with an average abundance of 463.28 ± 284.08 particles/kg_dw. Small-sized MPs of 2 mm and less were the most abundant, representing more than 82% of the total particles. Fragments and coloured MPs were the most dominant compared to other shapes and transparent particles, accounting for 63% and 60%, respectively. Microplastics were identified as polyethylene (PE) (both high and low density), polypropylene (PP), and polyethylene co-vinyl acetate (PEVA), polyester (PES), polyurethane foam (PU), and polyethylene/hexene-1-copolymer (PEH). These findings reveal elevated levels of MP contamination within the Vaal from secondary sources. Potential sources include wastewater effluent, anthropogenic activities, surface run-off from urban centres, inflow from tributaries, and recreational activities.
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Concerns regarding the impacts of microplastics in the global environment have brought into focus the need to understand better their origins, transport, and fate. Wastewaters (WW) are important in this regard: discharges from households, commercial and industrial premises, and surface run-off deliver microplastics to wastewater treatment plants (WWTPs) via sewerage systems, through which they are removed along with sewage sludge or destined for release into the environment in treated effluent. This review provides a contemporary and critical analysis of factors influencing the quantities and composition of microplastics (MPs) reaching wastewater treatment plants, including both primary and secondary sources. Three specific areas of concern were highlighted. First, current legislation, where present, needs to address regulation of microplastics in personal care and cosmetic products that cross international borders. Secondly, accurate estimation of microplastics arising from some sources and activities (e.g., mis-managed waste and hand washing of textiles) is challenging and estimated contributions of associated microplastics remain unsatisfactory as a basis for management decisions. Thirdly, information relating to microplastics in personal care and cosmetic products used by male consumers is lacking and contributions of such products to wastewater remain uncertain. We recommend that (1) voluntary practices and programmes should be replaced with formal regulation to achieve compliance, and (2) the role of consumers’ behaviour in generating microplastics that are destined for wastewater treatment plants remains largely unknown and that more research in this domain is needed.
Studies in the oceans and The Great Lakes have found several orders of magnitude less plastic in surface samples than predicted by input estimates. Some plastic likely sinks after entering the water because it is naturally more dense than freshwater. For less dense particles, it has been proposed that biofouling, or the buildup of organic materials on the plastic, can cause them to become more dense and ultimately induce sinking. In this work we compare two different functional biofouling models: one basic algal growth population model and one model that assumes photosensitive defouling. We investigate the effects within the scope of a large-scale hydrodynamic model that includes advection, vertical diffusion, and sediment deposition applied to both Lake Erie and Lake Ontario. We find that deposition rates are dependent on the fouling method and lake depth. Lastly, we use the model to develop a first pass mass estimate for the sediment deposition rate in Lake Ontario.
Microplastic categorization schemes are diverse, thereby posing challenges for cross‐study comparisons. Further, categorization schemes are not necessarily aligned with, and thus useful for applications such as source reduction initiatives. To address these challenges, we propose a hierarchical categorization approach that is “fit for purpose” to enable the use of a scheme that is tailored to the study’s purpose and contains categories which, if adopted, would facilitate inter‐study comparison. The hierarchical categorization scheme is flexible to support various study purposes (e.g., to support regulation, toxicity assessment) and it aims to improve the consistency and comparability of microplastics categorization. Categorization is primarily based on morphology, supplemented by other identification methods as needed (e.g., spectroscopy). The use of the scheme was illustrated through a literature review aimed at critically evaluating the categories used for reporting microplastics morphologies in North American freshwater environments. Categorization and grouping schemes for microplastic particles were highly variable, with up to 19 different categories used across 68 studies, and nomenclature was inconsistent across particle morphologies. Our review demonstrates the necessity for a “fit for purpose” categorization scheme to guide the information needs of scientists and decision‐makers for various research and regulatory objectives across global, regional, and local scales. This article is protected by copyright. All rights reserved.
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Microplastic contamination was studied along a freshwater continuum from inland streams to the Milwaukee River estuary to Lake Michigan and vertically from the water surface, water subsurface, and sediment. Microplastics were detected in all 96 water samples and 9 sediment samples collected. Results indicated a gradient of polymer presence with depth: low-density particles decreased from the water surface to the subsurface to sediment, and high-density particles had the opposite result. Polymer identification results indicated that water surface and subsurface samples were dominated by low-density polypropylene particles, and sediment samples were dominated by more dense polyethylene terephthalate particles. Of the five particle-type categories (fragments, films, foams, pellets/beads, and fibers/lines), fibers/lines were the most common particle-type and were present in every water and sediment sample collected. Fibers represented 45% of all particles in water samples and were distributed vertically throughout the water column regardless of density. Sediment samples were dominated by black foams (66%, identified as styrene–butadiene rubber) and to a lesser extent fibers/lines (29%) with approximately 89% of all of the sediment particles coming from polymers with densities greater than 1.1 g cm–3. Results demonstrated that polymer density influenced partitioning between the water surface and subsurface and the underlying surficial sediment and the common practice of sampling only the water surface can result in substantial bias, especially in estuarine, harbor, and lake locations where water surface concentrations tend to overestimate mean water column concentrations.
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Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies.
Investigations of microplastic abundances in freshwater environments have become more common in the past five years, but few studies concern the factors that control the distribution of microplastics in river systems. We sampled benthic sediment from 34 stations along the Thames River in Ontario, Canada, to determine the influence of land use, grain size, river morphology and relative amount of organic debris on the distribution of microplastics. Once counted and characterized for shape, color and size, microplastic abundances were normalized to the results from Fourier Transform Infrared Spectroscopy (FTIR) on randomly selected particles. The results indicate that 78% of the fragments and only 33% of the fibers analyzed were plastic. The normalized microplastic quantities ranged from 6-2444 particles per kg of dry weight sediment (kg-1 dw). The greatest number of microplastics were identified in samples of the finest grain sizes and with the greatest amount of organic debris. Although there was no significant difference between microplastic abundances in urban versus rural locations, the average microplastic count for urban samples was greater (269 kg-1 dw versus 195 kg-1 dw). In terms of river morphology, samples from along straight courses of the river contained fewer microplastics than samples from inner and outer bends. Overall abundances confirm how rivers contain a significant number of plastic particles and thus may be major conduits of microplastics to lake and ocean basins.
Sediment samples were collected from nearshore, tributary and beach environments within and surrounding the northern part of Lake Erie, Ontario to determine the concentrations and distribution of microplastics. Following density separation and microscopic analysis of 29 samples, a total of 1178 microplastic particles were identified. Thirteen nearshore samples contained 0–391 microplastic particles per kg dry weight sediment (kg⁻¹), whereas 4 tributary samples contained 10–462 kg⁻¹ and 12 beach samples contained 50–146 kg⁻¹. The highest concentrations of nearshore microplastics were from near the mouths of the Detroit River in the western basin and the Grand River in the eastern basin, reflecting an urban influence. The highest microplastic concentrations in beach samples were determined from Rondeau Beach in the central basin where geomorphology affects plastics concentration. The Welland Canal sample in the eastern basin contained the greatest concentration of microplastics of the tributary samples, which is consistent with high population density and shipping traffic. The overall abundance of microplastic in northern Lake Erie nearshore, tributary and beach samples is 6 times lower than in sediment sampled from northern Lake Ontario. The nearshore and beach sample results potentially reflect the transport patterns of floating plastics modeled for Lake Erie, which predict that the majority of plastic particles entering the lake are transported to southern shoreline regions rather than northern areas.
A substantial fraction of marine plastic debris originates from land-based sources and rivers potentially act as a major transport pathway for all sizes of plastic debris. We analyzed a global compilation of data on plastic debris in the water column across a wide range of river sizes. Plastic debris loads, both microplastic (particles <5 mm) and macroplastic (particles >5 mm) are positively related to the mismanaged plastic waste (MMPW) generated in the river catchments. This relationship is nonlinear where large rivers with population-rich catchments delivering a disproportionately higher fraction of MMPW into the sea. The 10 top-ranked rivers transport 88–95% of the global load into the sea. Using MMPW as a predictor we calculate the global plastic debris inputs form rivers into the sea to range between 0.41 and 4 × 10⁶ t/y. Due to the limited amount of data high uncertainties were expected and ultimately confirmed. The empirical analysis to quantify plastic loads in rivers can be extended easily by additional potential predictors other than MMPW, for example, hydrological conditions.
Most plastic pollution originates on land. As such, freshwater bodies serve as conduits for the transport of plastic litter to the ocean. Understanding the concentrations and fluxes of plastic litter in freshwater ecosystems is critical to our understanding of the global plastic litter budget and underpins the success of future management strategies. We conducted a replicated field survey of surface plastic concentrations in four lakes in the North American Great Lakes system, the largest contiguous freshwater system on the planet. We then modeled plastic transport to resolve spatial and temporal variability of plastic distribution in one of the Great Lakes, Lake Erie. Triplicate surface samples were collected at 38 stations in mid-summer of 2014. Plastic particles >106 μm in size were quantified. Concentrations were highest near populated urban areas and their water infrastructure. In the highest concentration trawl, nearly 2 million fragments km−2 were found in the Detroit River—dwarfing previous reports of Great Lakes plastic abundances by over 4-fold. Yet, the accuracy of single trawl counts was challenged: within-station plastic abundances varied 0- to 3-fold between replicate trawls. In the smallest size class (106–1,000 μm), false positive rates of 12–24% were determined analytically for plastic vs. non-plastic, while false negative rates averaged ~18%. Though predicted to form in summer by the existing Lake Erie circulation model, our transport model did not predict a permanent surface “Lake Erie Garbage Patch” in its central basin—a trend supported by field survey data. Rather, general eastward transport with recirculation in the major basins was predicted. Further, modeled plastic residence times were drastically influenced by plastic buoyancy. Neutrally buoyant plastics—those with the same density as the ambient water—were flushed several times slower than plastics floating at the water's surface and exceeded the hydraulic residence time of the lake. It is likely that the ecosystem impacts of plastic litter persist in the Great Lakes longer than assumed based on lake flushing rates. This study furthers our understanding of plastic pollution in the Great Lakes, a model freshwater system to study the movement of plastic from anthropogenic sources to environmental sinks.
Measurements of microplastics in biota and abiotic matrices are key elements of exposure and risk assessments for this emerging environmental pollutant. We investigated the abundance of microplastics in field-collected biota, sediment and water. An improved sediment extraction method, based on density separation was developed. For analysis of microplastics in biota we found that an adapted enzymatic digestion protocol using proteinase K performed best, with a 97% recovery of spiked plastic particles and no observed degradation effects on the plastics in subsequent Raman analysis. Field analysis revealed that 8 of 9 tested invertebrate species from the North Sea and 68% of analyzed individuals of brown trout (Salmo trutta) from the Swedish West Coast had microplastics in them. Based on the number of plastic particles per kg d.w. the microplastic concentrations found in mussels were approximately a thousand-fold higher compared to those in sediment and surface water samples from the same location.
Plastic pollution in the world's oceans has received much attention, but there has been increasing concern about the high concentrations of plastic debris in the Laurentian Great Lakes. Using census data and methodologies used to study ocean debris we derive a first estimate of 9887 metric tonnes per year of plastic debris entering the Great Lakes. These estimates are translated into population-dependent particle inputs which are advected using currents from a hydrodynamic model to map the spatial distribution of plastic debris in the Great Lakes. Model results compare favorably with previously published sampling data. The samples are used to calibrate the model to derive surface microplastic mass estimates of 0.0211 metric tonnes in Lake Superior, 1.44 metric tonnes in Huron, and 4.41 metric tonnes in Erie. These results have many applications, including informing cleanup efforts, helping target pollution prevention, and understanding the inter-state or international flows of plastic pollution.