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[1]
Small plastic particles in
Coastal Swedish waters.
KIMO Sweden
Consultants
www.n-research.se
Dr. Fredrik Norén
+46-(0)70-299 23 85
Lysekil 2007-08-29
B
lue plastic fibre, diameter ~20µm
[2]
Summary
KIMO Sweden has given N-research an assignment to perform a pilot-study to assess
the abundance of small, microscopic, plastic particles in Swedish west coast waters.
N-research has taken water samples from nineteen locations, both planktonic and
from benthic sediments, and conducted analyses thereof.
In this pilot study we found:
• There is a considerably higher amount of small plastic particles when using an
80µm mesh to concentrate the water samples. Up to 100 000 times higher
concentrations of small plastic fibers was retained on a 80µm mesh compared
to a 450µm mesh
• The amount of plastic particles, concentrated with a 80µm mesh net, was in
the range of 150 – 2400 per m3
• The amount of plastic particles, concentrated with a 450µm mesh net, was in
the range of 0,01 – 0,14 per m3 which is comparable to earlier surveys (0,01 –
7 per m3).
• A very high concentration, 102 000 per m3 of plastic particles (diam. ~0.5 -
2mm) was found locally in the harbour outside a polyethene production plant.
If you have further questions on this report, please contact:
fredrik.noren@n-research.se
[3]
Introduction
KIMO Sweden has given N-research an assignment to perform a pilot-study to assess
the abundance of small, microscopic, plastic particles in Swedish west coast waters.
N-research have sampled and analyzed nineteen water samples and three samples
from bottom sediments along the Swedish west coast, from Gothenburg and 120km
northwards.
Earlier investigations has shown that the number of small, microscopic, plastic
particles has increased in number in recent time and correlating to increased
production of plastic materials (Thompson et al. 2004). Further, the plastic particles
are vectors for organic pollutants (Mato et al. 2001; Takada 2006; Rios et al. 2007)
and are a lethal threat to seabirds (Ryan 1987), fish (Vlietstra and Parga 2002) and
invertebrates (Thompson et al. 2004).
The abundance of larger plastic debris has been more extensively assessed than their
microscopic counterparts and this survey aims, for the first time, to quantify the
concentration of microscopic plastic particles in the sea.
[4]
Methods
Earlier investigations have been performed, generally, in two ways; by using a
plankton net in order to concentrate the plastic particles from surface water or by
washing low-density particles from sediment samples. In order to enable comparison
with previous studies, this pilot study was performed using similar methods
(Thompson et al. 2004). The methodology was also extended by sampling with a net
with finer mesh to include smaller plastic particles (<450μm).
Sampling sites
Sixteen sites along the Swedish west coast were chosen for sampling in such a way
that a distribution was achieved between outer and inner archipelago as well as
between localities influenced and not influenced by harbours. See table 1.
Table 1 Sample locations during the pilot study
Sampling site Notes Sample device / type
Lysekil, Southern harbour Many leisure boats in the
harbour during the sampling. 80µm mesh
Lysekil, Southern harbour
Sample from the innermost
harbour, Much litter in the water.
Sheltered site. 80µm mesh
Lysekil, Southern harbour
Not the same water package as
in the major harbour, but
“cleaner” Gullmar Fjord water. 80µm mesh
Lysekil, Släggö (Island outside
Southern harbour) Gullmar Fjord water 80µm mesh
Björkö harbour A windy day with good water
exchange. 80µm mesh
Björkö ferry Clear water 80µm mesh
Tjuvkils huvud, harbour Small harbour, sampling in
sheltered part of harbour. 80µm mesh, sediment
Stenungsund, location 3
Industrial area, samples from
the inner part of bay with
seaweed vegetation 80µm mesh, sediment
Stenungsunds harbour Harbour outside shopping center 80µm mesh
Stenungsund, location 4 Industrial area, sampled from
the rocks 80µm mesh
Stenungsund, industry harbour The official industrial harbour of
Stenungsund 80µm mesh, sediment
Lysekil, Gäven-Byxeskär
Between Gäven and Byxeskär
(1 – 1.5 nautical miles west of
Lysekil) 80µm mesh
Lysekil, Gäven South of Gäven (2.5 nautical
miles west of Lysekil) 80µm mesh
Lysekil, Gullmar fjord,
Blåbergsholmen West of Blåbergsholmen 450µm mesh
Lysekil, Islandsberg, sample 1 West of wave energy park 450µm mesh
Lysekil, Islandsberg, sample 2 East of wave energy park 450µm mesh
Metods used in previous studies
In order to quantify the amount of plastic particles in the water mass a plankton net
trawl, intended for fish egg and larvae (1x2 meter with 0.947mm mesh), was trawled
[5]
at five knots for ten minutes (Colton et al. 1974). In other studies a “Manta trawl”
(0.9x0.15m, with 333μm mesh) was used and the trawling distance varied between 5
km and 19 km, which yields an approximate volume of 675m3 to 2565m3 (Moore et al.
2001; Lattin et al. 2004).
In order to quantify the amount of plastics in sediment samples a trowel and Ekman
sampler was used in order to collect the samples. The sediment was then stirred in
high salinity water solution (1 kg NaCl/l), the supernatant was filtered an examined
for plastic particles (Thompson et al. 2004).
In the most recent studies plastic particles were qualitatively determined as a specific
plastic polymer by the use of FTIR (Fourier Transformation Infra Red Spectrometry)
combined with a microscope (Thompson et al. 2004).
Plastic particles in surface water
Two methods were used;
A. A known volume of surface water was poured from a 5 litres measuring jug
(unknown plastic) into a phytoplankton net of nylon fabric (rectangular meshes,
80μm, Fig. 1c) into a collection container
of polypropylene. The surface water was
sampled from 0-0.3 meter depth. The
concentrate was filtered onto a 2.0μm
filter (ø45mm, polycarbonate, Osmonics
Inc.). The filter was rinsed with 100 ml
tap water in order to avoid salt crystals
and left to dry for at least 24h., before
examination under a stereo microscope
(20x/40x) or fluorescence microscope
(100x/200x/400x). In order to facilitate
the analysis and enable partial sampling,
the filter was divided into eight equally
sized parts. The entire filter was analysed
for all samples except the one with the
highest amount of plastic particles. For
this sample only two eighth parts were
analysed and the average value was used
as an estimate of the concentration (249
and 263 particles). A control was
performed where 20 litres of tap water
was concentrated and analysed in the
same way as the sea water samples in
order to see if any plastic material in the
sampling equipment could have ended up
in the samples. No plastic fibres/particles
were found in this control.
B. A zooplankton net with mesh-size 450μm
was dragged, just below the surface,
behind a small motor boat making 1-2
knots for about 10 minutes. A speed log
inside the net was measuring the flow of water inside the net in order to calculate
the amount of water volume filtered. The concentrate from the net, 0.5 litres was
poured into a storage container (PVC) and brought to the laboratory for analysis.
Figure 1. Microscopes and plankton net (80µm)
used in the survey
[6]
The samples were poured into petridishes and analysed with reference to plastic
particles, which were sorted out with tweezers and a Pasteur pipette for
examination under a stereo microscope and microscope.
Following criteria were used to define a plastic particle (see fig 2 for an example);
• No cellular or organic structures are visible in the plastic particle/fibre
• If the particle is a fibre it should be equally thick, not taper towards the ends
and have a three-dimensional bending (not entirely straight fibres which
indicates a biological origin)
• Clear and homogeneously coloured particles (blue, red, black and yellow)
• If it is not obvious that the particle/fibre is coloured, i.e. if it is transparent or
whitish, it shall be examined with extra care in a microscope under high
magnification and with fluorescence microscopy in order to exclude an organic
origin.
In the analyses the particles were examined conservatively and only particles that
complied with the above criteria were included as plastic particles. The main
consequence of this is that transparent fibres were not included because of their
similarity to antennae and fibres from different organisms (animals, plants and
protists). This can have led to an underestimation of white/transparent plastic fibres.
Red fibres were also scrutinized with extra care, because of their similarity to young
algae sprouts. These were discriminated by studying the fibre in a microscope under
higher magnification and with fluorescence microscopy, making the chloroplasts of
the red algae clearly visible.
Figure 2 Different plastic particle in the water. A. Red plastic fibres (diam. ~70µm) B. Blue plastic particle C.
Blue plastic fibre (diam~100µm) D. White/transparent plastic film, 1*1,5cm E. Milky-white plastic spheres,
diam. ~0,4-2mm F. Milky-white plastic spheres and suspected tar particles.
Plastic particles in sediments
A high-saline solution (about 20 % salinity) was prepared. The 100 ml sediment
samples were poured into the saline solution, was stirred for about a minute and left
for at least 20 minutes before decanting and filtering the supernatant through a 2μm
filter. Filtration and analysis was performed with the same methods that were used
for analysis of plastic particles in surface water (described above).
[7]
Results & discussion
The pilot study presents some remarkable results;
1. The plastic fibres concentrated in the 80μm mesh net are much more
numerous (~1000 times more) than the reported number of plastic particles
with 333/450 μm mesh nets (see table 2 and 3). This indicates that the
number of small plastic particles passing through a zooplankton net might be a
considerably larger source of pollution than realised before. These particles
have also been reported to be ingested by filter-feeding invertebrates
(Thompson et al. 2004) and possibly bioaccumulate in higher trophic levels of
the food chain. Given the fact that organic pollutants accumulate on the plastic
particles (Mato et al. 2001), this amount of small particles is extraordinarily
serious since the area/volume quota of the particles increases with smaller
particle volume (a large amount of small plastic particles may be a larger
vector of organic pollutants than fewer large ones). We recommend
continued studies of plastic particles in this size fraction and studies of
bottoms sediments in order to examine historical occurrence or these
particles. Have they increased in correlation to the production of plastics?
2. There seems to be a local emission of plastic particles at Stenungsund with the
highest amount of plastic particles around the loading port for the plastic
producing plants. The amount of small plastic particles reached over 100,000
per m3. We recommend more detailed and extensive studies of the area at
Stenungsund, with more sampling sites, that determination of plastic species
with the aid of FTIR microscopy is performed and that the sampling
methodology is developed further (for instance by using plastic free sampling
equipment). Since this is a pilot study we do not want to name the industry
outside which the sampling has been done.
3. The amount of plastic particles concentrated with the 450μm mesh net is less
than reported from other sea areas, see table 3. We recommend further
sampling along the Bohus Coast, both in the inner and outer parts of the
archipelago and in the known litter areas further out where different currents
meet. Furthermore, the net mesh should be in the same size as in previous
studies i.e. 333μm, in order to exclude differences in result depending on mesh
size.
[8]
Plastic particles in the surface water
A. The result of the sampling with an 80μm net demonstrates that there is a large
amount of small plastic particles in the sea. We have not found any previous study
estimating concentrations of such microscopic particles since previous studies always
have used a zooplankton net with a mesh size exceeding 333μm.
The number of plastic particles differed between sites. In the harbour of Lysekil,
which is well frequented by leisure boats, a large amount of plastic fibres were found
that might come from wearing on ropes. In the waters outside the Lysekil harbour, at
Björkö and at Tjuvkil the number of plastic particles was lower.
In the harbour of Stenungsund a very special type of plastic particles is found (see
figure 2 E & F). The occurrence might originate from careless handling in connection
with loading of plastic pellets from the plastics industry in Stenungsund. We are
however very careful about commenting on the source of this pollution until more
qualified studies have been made in the area. In the laboratory, the particles showed
the following properties: They were not dissolved in ethanol, acetone or xylene. The
particles melted after having been heated gently on a microscope slide with a spirit
burner. They emitted a distinct smell of plastics, as they were melting (smell of
melted plastic rope end). Furthermore the plastic resolidified after having cooled and
could easily be scratched with a sharpened glass needle.
Table 1 Number of plastic particles concentrated with 80µm plankton net
The amount of particles in number per m3
Red fibres
Blue
fibres
Black /
transp.
Milky-
white
spheres
Σ particles
per m3
+/-
sd
Lysekil, Southern harbour 50 1 900 450 0 2 400
Lysekil, Southern harbour,
inner harbour 100 550 500 0 1 150
Lysekil, Southern harbour,
nrthern Släggö 50 350 200 0 600
Lysekil, outer Släggö 50 100 50 0 200
Björkö harbour, mean of 2
samples 0 400 250 0 450 283
Björkö ferry,mean of 3
samples 0 200 100 0 167 126
Tjuvkils huvud, harbour 50 200 0 0 250
Stenungsund, location 3 25 0 25 1 575 1 625
Stenungssunds leisure-
boat harbour 50 150 50 850 1 100
Stenungsund, location 4 50 300 50 750 1 150
Stenungsund, industrial
harbour 0 150 0 102 400 102 550
Lysekil, Gäven-Byxeskär 80 120 320 40 560
Lysekil, Gäven 70 160 80 0 310
[9]
B. The result of the samplings with a 450μm mesh net indicates that the amount of
plastic particles in any case is not alarmingly higher than in other sea areas, compare
tables 2 and 3. The sampling with the 450μm was performed within a small
geographic area (outside Skaftö in the water system of the Gullmar Fjord) which does
not give us an indication on the regional occurrence since different currents can
contain different amounts of plastic particles. As plastic particles drift and floats with
the currents it is important to study the number of plastic particles in different water
packages and not only at a geographical site. We used a 450μm net while previous
studies have used a 333μm net, a consequence of this difference could be that we
have underestimated the number of small plastic particles. We also have not filtered
as large volumes as previous studies did (they filtered ~10 times larger volumes).
Table 2 Number of plastic particles concentrated with 450um zooplankton net
Particles Colour
Size
(mm) Sum
Sample
volume
(m3)
Number
per m3
Sample 1 1 plastic film Milkywhite / transp. 1 130 0.01
Sample 2 2 extruded.polystyrene white 2*3 10 72 0.14
2 extruded polystyrene white 1*1
1 hard plastic particle white 3*3*1
5 plastic film milkwhite/transparent 3*4
Sample 3 1 plastic particle white 2*3*2 5 141 0.04
1 plastic particle white/transparent 5*5*1
1 plastic particle white/transparent 2*2*1
1 plastic particle white 2*3*2
1plastic film grey/transparent 30*20*1
Table 3 Results from previous studies
Reference Particle concentration
(per m3)
Sea Sample type
(Moore et al. 2005) 0.43 – 2.23 North Pacific Offshore, surface
-II- 5.0 – 7.25 North Pacific Inshore, surface
-II- 0.017 North Pacific Offshore, subsurface
(Thompson et al.
2004) 0.01 – 0.06 Scottland-
Shetland
(Lattin et al. 2004) 0.5 – 18 Kalifornien Inshore, surface
(Carpenter et al. 1972) 0.01 – 2.6 USA north east Coastal waters
[10]
Plastic particles in sediments
The result of the studies of plastic particles in sediments also shows that there is a
local littering source at Stenungsund. In other respects, the number of particles from
the harbour at Tjuvvik was consistent with the number of particles found in
sediments along the English coast (Thompson et al. 2004), i.e. between 1 and 10
particles per 100ml sediment.
Tabell 4 Number of plastic particles concentrated from sediment samples
Site
Sample
volume Particles Colour Size (mm)
Tjuvkils harbour 100ml 2 plastic Milkwhite/transparent 7*1*1
5 plastic Milkwhite/transparent 1*1*1
Stenungsund, industrial
harbour 100ml
332 plastic
spheres Milkwhite/transparent t 0,5-1mm diam.-
Stenungsund, location 3 100ml 34 plastic
spheres Milkwhite/transparent 0,5-1mm diam.
[11]
Referenser
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Atlantic. Science 185:491-497.
Lattin, G. L., C. J. Moore, A. F. Zellers, S. L. Moore, and S. B. Weisberg. 2004. A comparison of
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