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Microplastics in a Marine Environment: Review of Methods for Sampling, Processing, and Analyzing Microplastics in Water, Bottom Sediments, and Coastal Deposits



The basic approaches, methods, and procedures for collecting and analyzing samples of microplastics in a marine environment are briefly described.
ISSN 0001-4370, Oceanology, 2018, Vol. 58, No. 1, pp. 137–143. © Pleiades Publishing, Inc., 2018.
Original Russian Text © M.B. Zobkov, E.E. Esiukova, 2018, published in Okeanologiya, 2018, Vol. 58, No. 1, pp. 149–157.
Microplastics in a Marine Environment: Review of Methods
for Sampling, Processing, and Analyzing Microplastics in Water,
Bottom Sediments, and Coastal Deposits
M. B. Zobkov* and E. E. Esiukova
Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
Received December 15, 2015; accepted July 3, 2016
Abstract—The basic approaches, methods, and procedures for collecting and analyzing samples of micro-
plastics in a marine environment are briefly described.
DOI: 10.1134/S0001437017060169
Contamination of a marine environment by micro-
plastics is currently an urgent ecological problem
barely covered in the Russian scientific press. The
main difficulty when providing quantitative assess-
ment of microplastics in marine environment is the
absence of standard procedures for collecting and ana-
lyzing samples of water, bottom sediments, and coastal
Today, plastics are one of the most demanded
materials used worldwide. The physicochemical prop-
erties of plastics, mainly endurance, light weight, and
durability combined with low manufacturing costs
make this material nearly irreplaceable in the produc-
tion of domestic goods, construction, and industry.
According to various estimates, the worldwide
annual production of plastics ranges from 275 to
299 mln t [13, 26, 29, 37], whereas the scales of utiliza-
tion and reprocessing are much lower.
Plastic products gradually break down under natu-
ral conditions. This results in huge amounts of macro-,
micro-, and nanoparticles, which are the most harm-
ful to the environment. The specific density of plastic
is clo se to that of water. Because of this, synthetic litter
is easily transported from a catchment area into lakes
and rivers and finally enters the seas and the World
Ocean [5, 37, 45]. Microplastics have various sizes and
low density. As a consequence, many living organisms
perceive them as food [2, 4, 19]. Since their enzymatic
system cannot break plastic down, ingestion of the lat-
ter is harmful by itself for organisms and may cause a
fatal outcome [9, 14, 16, 35]. However, the largest
concerns arise from the fact that microplastics are able
to adsorb contaminants on their surfaces [3, 12, 17, 27,
38] and thereby become a secondary source of con-
taminants. The latter travel up the food chain and
accumulate in higher predators and humans [25, 32].
In addition to the secondary microplastics, which
originate from breakdown of staff or large litter debris,
there are primary ones that penetrate the water bodies
in their initial state [18, 25]. These are plastic granules,
or pellets. They serve as a raw material for manufactur-
ing plastic sheets or ready-to-use items. The cosmetic
industry [15, 18, 44] uses micro granules (microspheres,
nanospheres, microcapsules, nanocapsules) [28, 44].
Currently, there is no final opinion on particle size that
corresponds to microplastics, but the majority of
researchers [20, 45] agree that these are particles from
0.5 to 5 mm in their larger dimension. Some authors
proposed a lower limit close to 0.3 mm [10] due to wide-
spread water sampling techniques using zooplankton
nets with a mesh size of 333 μm [18]; the maximum par-
ticle size corresponding to the definition of microplastic
continues to be a matter of discussion [32]. It is no acci-
dent that particles from 0.5 to 5 mm are considered as a
special group. This is due to the substantial technical
difficulties inherent to analyzing particles smaller than
0.5 mm [20]. In the present review, we adhere to exactly
this dimensional range when determining microplastic
particles. As yet, there is no clear answer to the question
which synthetic substances can be classified as micro-
plastics. This problem has been solved for the majority
of polymers, such as polyethylene, polypropylene,
polystyrene, etc. However, no solution has been found
for other anthropogenic substances such as alkyd resins
or viscose.
The first reports on the discovery of microplastics in
plankton samples go back to early 1970s [6, 7], but only
now is the problem of microplastics in the World Ocean
becoming a matter of discussion in foreign scientific lit-
erature [5, 11, 15, 25, 40]. Microplastics is an extremely
heterogeneous ensemble of particles that vary in size,
shape, color, density considerably and may incorporate
OCEANOLOGY Vol. 58 No. 1 2018
a wide variety of synthetic polymers. This is why reliable
methods of sample collecting, sample preparation, and
plastic detection remain one of the main difficulties in
quantitative assessment of the environment. Nearly all
researchers raise the question of developing standard
procedures. Despite the fact that the first steps in this
direction have already been taken [33], the problem as a
whole remains unsolved.
Nevertheless, many scientists devote efforts to
develop and test techniques for collecting and preparing
samples of water, bottom sediments, and coastal depos-
its, as well as to develop methods for detecting micro-
plastics in samples. Current laboratory procedures for
analyzing microplastics in a marine environment devel-
oped by NOAA [33] for studying marine litter have cer-
tain drawbacks and are voluntary in nature, while mon-
itoring programs require relying on specific solutions
depending on the problems to be solved.
To date, the occurrence and detection of micro-
plastics in a marine environment have not been raised
in Russian scientific publications. To expand the audi-
ence interested in contamination of a marine environ-
ment by microplastics and for convenience in search-
ing for relevant information, we have prepared transla-
tions of a number of foreign scientific papers on the
acquisition and analysis of samples of microplastics in
a marine environment, as well as descriptions of pro-
cedures and standards for testing the polymers. These
translations are available at site of the Shirshov Insti-
tute of Oceanology, Russian Academy of Sciences
337-anons-publikatsii) and involve complete transla-
tion of laboratory techniques for analyzing microplas-
tics in a marine environment [33] supplemented by
critical comments by authors, discussion of methods
for measuring the specific density of noncellular plas-
tic [22, 34], a method for determining plastic in water
samples with our improvements, and a complete bib-
liography of the sources found. Our intention is to
expand this list as new reviews appear. Among others,
we suggest adding author methods for obtaining and
processing samples of microplastics in water, bottom
sediments, and coastal deposits based on our own and
advanced foreign experiences.
Below is a brief description of the main approaches,
methods, and techniques for obtaining and analyzing
samples of microplastics in a marine environment.
Different types of equipment [42, 34] and analyti-
cal laboratory methods [20, 39] are needed for sam-
pling and determining plastic particles of different size
groups. Particle size determines the inf luence on the
life of oceanic communities and migration pathways in
the ocean.
Samples of microplastics in a marine environment
can be collected (1) from the surface layer, (2) from the
water column, and (3) by sampling bottom sediments or
(4) coastal deposits. Samples can be (1) selective,
(2) bulk, or (3) volume-reduced.
Selective sampling in situ means that plastic debris
usually is recognized by the naked eye and is picked up
from the sandy beach surface. This technique is useful
during assessment of plastic granules and is suitable
due to their spherical shape and relatively large sizes
(up to several millimeters), which facilitates their rec-
ognition on the sandy surface. However, chances of
missing plastic are high when it is mixed with other
rubbish or has an irregular shape.
No concentration of plastic takes place when bulk
samples are collected. Such a technique is the most
popular when studying bottom sediments, but it is
rarely used for water sampling due to low plastic con-
tent in water. Bulk sampling is preferable when visual
identification of plastic is impossible, i.e., if particles
are mixed with the bottom sediments or particles are
too small for filtration at the sampling site or for the
naked eye recognition.
The volume-reduced method is the most applicable
for water sampling and sometimes for bottom sedi-
ments. In this case, the volume of the initial sample is
decreased and only a small fraction of it containing
microplastics remains for subsequent analysis. Sam-
ples of bottom sediments and sand can be sieved
directly at the sampling site on the beach or aboard a
vessel, while water samples are usually concentrated
by filtration of large volumes of water through plank-
ton nets. The bulk and volume-reduced samples
require extra processing under laboratory conditions.
According to the NOAA recommendations [33],
the following procedures can be used for separating
microplastic particles from environmental samples
depending on their size: (1) flow Nanofiltering or
nanofractioning of particles smaller than 1 μm;
(2) a standard filter for particles sizing from 0.2 to
1 μm; (3) the use of phytoplankton neuston net 50–
80 μm (Phyto-P net); (4) zooplankton neuston net
(Zoo-P net) 330 μm; (5) a 5 mm sieve for sieving. It is
difficult to compare the results from sieving and
plankton nets. Therefore, it is recommended to use
sieves with a 500 μm mesh and separately process the
particles retaining and passing through the sieve as a
mandatory operation within each of the above proce-
dures [20]. This makes it possible to compare the results
from density separation and filtering to the data
obtained from analysis of larger fractions (0.5–5 mm)
with sieves.
Surface water samples. Neuston nets are mainly
used in this case. The main advantage is fast filtering of
large volumes of water and obtaining of a concentrated
sample. The nets make it possible to get a representa-
tive sampling from a large water surface, to collect
plastic particles of the millimeter range, and concur-
rently collect microplastics and zooplankton to com-
pare their amounts.
The mesh and opening sizes are the most import-
ant characteristics of sampling nets. However, the
parameters of sampling nets are rarely reported in full
OCEANOLOGY Vol. 58 No. 1 2018
and the mesh size is usually the only parameter men-
tioned in publications. The mesh size depends on the
research goals and varies from tens of microns to mil-
limeters, but it corresponds to the mesh size of zoo-
plankton nets on average. The opening size of neuston
nets is up to 2 m2. The length of these nets for surface
sampling varies substantially from one to several
meters, but nets 3–4 m long are the most common. The
surface layer sampled by such nets is about 15–25 cm
thick. The buoyancy of a net is supported by special
floats (manta trawl) or catamaran (neuston catama-
ran). The net towing speed varies from 1 to 5 knots.
The use of catamaran facilitates sampling in rough sea
conditions while the efficiency a manta trawl decreases
due to submersion of its inlet in waves. Therefore, the
latter net is applicable in calm waters. Duration of
towing varies from minutes to hours depending on the
SPM content in water.
The use of nets with different mesh sizes consider-
ably hampers comparison of the measurement results.
Samples from the water column. Zooplankton nets,
a continuous plankton recorder (CPR) [43], a near-
bottom trawl for catching benthic organisms (epiben-
thic sled) [31], and various submersible pumps are the
most commonly used tools in the water column. The
water intake system of a research vessel is used too, but
rarely. Niskin bottles are employed for full-volume
sampling of waters. Different studies used different
methods for water sampling at depth ranges from one
to hundreds of meters.
Samples of coastal deposits. The samples were
mainly collected at different parts of a beach and the
choice of the specific site can influence the analysis
results. The sample collection (or series of collections)
is performed (1) over the entire beach, (2) within a
number of separate zones, (3) along the alignment of
different zones of a beach, (4) along the line of maxi-
mum tide or uprush (on the upper beach), and (5) in
ditches or trenches beyond the beach.
Simple tools are frequently used for collecting sam-
ples of plastic granules and fragments (tweezers, metal
spoons, or scoops) or particles are simply collected by
hand using a special container or bag. The collecting
strategy varies: movement in the same direction along
the shoreline and picking up material with a spoon or
scoop or sometimes from a certain area within a spe-
cial frame. In a number of cases, stratified sampling
with special tubes is used.
Sampling units directly depend on the tools used.
In the case of frames or pipes, the concentrations were
calculated per area (from several cm2 to 5 m2). In other
cases, the concentration is calculated per sample
weight, which can range from hundreds of grams to
10 kg, or per sample volume, which varies from tens of
milliliters to several liters.
As a rule, the sampling comprises the upper 5 cm
of sediment, but it may be limited to the surface of a
beach or as deep as tens of centimeters. Microplastics
are able to accumulate in sand in the same way as
organic particles and can be buried in deeper layers.
In this case, it is desirable to use a stratified sampling
procedure with a tube.
Bottom sediments samples. Procedures for bottom
deposits sampling for microplastics content are similar
to those to determine their chemical composition or for
biological assessment. The samples are collected by
grabs (Ekman-Birdge, Van- Veen, Peter son), a bottom
trawl, or core sampler. The distribution of microplastics
as particulate matter in bottom sediments may be sub-
stantially heterogeneous. Therefore, it is necessary to
perform several sediment samplings to obtain a single
representative sample when using point-by-point
devices such as a grab or a corer. This is particularly
important in the case of compact samplers.
Conservation, storage, and quality control. Incorrect
storage of samples can cause a change in their particle
size distribution due to partial destruction of plastic
particles and, as a consequence, the impossibility of
their detection by available methods. Therefore, when
storing or transporting samples, it is desirable to use
procedures that can maintain the plastic in its initial
state at the moment of sampling from the environment.
The principles of storage and conservation of sam-
ples before laboratory analysis: (1) in darkness (if pos-
sible, at 4°С regardless of sample matrix), (2) freezing
(down to –20°С) the samples of bottom sediments
and filters, (3) the use of various fixing solutions (eth-
anol, DESS, 4–5% formalin solution, 5–10% HCl
solution), (4) combined use of fixing solution and
storage at 4°С, (5) drying at room temperature and
storage in the dark (shipborne analysis).
It is proper to avoid and replace when possible the
potential sources of plastic contamination (plastic lab-
oratory ware, plastic sieves and devices) for metal or
glassware. However, it is impossible in the case of nets
and a number of other instruments. A control with
empty samples is obligatory when plasticware is used
for storing the samples. The contamination of samples
may be due to insufficient air quality in the laboratory,
particles of synthetic working cloths, poor cleaning of
tools, loosely closed containers with samples, paint
particles broken off from the side of the vessel by sam-
plers, or particles of synthetic nets used for water sam-
pling. Blank samples must be used in routine for con-
tamination monitoring.
Sample preparation. There are four main stages:
(1) density separation, (2) filtering, (3) sieving, and
(4) organic matter digestion. All are aimed at separat-
ing microplastic particles from the main sample mate-
rial (water, bottom sediments, and sand) and remov-
ing of organic material.
Density separation. The specific density of most
plastics ranges from 0.8 to 1.70 g/cm3.The range
extends down from <0.05 g/cm3 for expanded polysty-
rene and up to 2.1–2.3 g/cm3 for polytetrafluoro-
ethylene/Teflon [8]. Generally, the density of sand
OCEANOLOGY Vol. 58 No. 1 2018
and other deposits is 2.65 g/cm3. This difference is
used widely to separate comparatively light plastics
from heavier soil particles by placing the sample in a
saturated saline solution and mixing it for a certain
period of time. After mixing, sand and bottom sedi-
ments settle out, while lighter particles (including
plastic ones) remain suspended or float on the solu-
tion surface. The floating particles are collected for
further processing. As a separating solution, fresh or
tap water, sea water, a concentrated NaCl solution
(with a density of 1.2 g/cm3), sodium polytungstate,
lithium metatungstate, zinc chloride, sodium iodide,
and other salts are used. Lightweight and foamed plas-
tics, whose density is less than 1 g/cm3, can also be
separated using fresh water. Plastics that float in sea-
water include expanded polystyrene and high- and
low- density polyethylene and polypropylene. Poly-
styrene in solid form emerges only in a saturated saline
NaCl solution. Elastic and rigid polyvinyl chloride
(PVC), polyethylene terephthalate (PET), and nylon
float up in a sodium metatungstate solution. Since the
density of some plastics reaches 1.7 g/cm3, the use of a
saturated solution of sodium chloride and especially
fresh water can lead to underestimation of the total
microplastic content. Various instruments (shakers,
mixers, centrifuges, flotators, and separators) are
employed to mix the solution. In the simplest case, the
sample is placed in a beaker and mixed with a glass stir
rod. The time of mixing is one of the main parameters
of the extraction. It can vary considerably depending
on the volume of the sample and can range from tens
of seconds to several hours. The settling time also var-
ies greatly and ranges from a few minutes to a day. It is
also expedient to carry out sequential extractions from
the sediment, which leads to increase in the efficiency
of microplastics extraction significantly, but at the
expense of increasing the analysis time also. The most
effective extraction method at this time involves the
Munich Plastic Sediment Separator (MPSS) [21].
Filtration. Vacuum filtration is usually employed
for a solution obtained at the density separation stage
that contains afloat plastic particles. For this, fiber-
glass, polycarbonate membrane, paper, nitrocellulose,
and silicon filters specially designed for FT-IR spec-
troscopy are used. The pore size varies from 1 to
1.6 μm. Filters with a pore size of 2 μm are rarely used.
Sometimes, the working solution with afloat particles
is passed through a fine mesh.
Filtration is also used to isolate microplastics from
bulk water samples. In this case, filters up to 15 cm in
diameter and with a pore size of up to 47 μm are used.
It is possible to collect microplastic particles from
the surface of the solution with tweezers. For separa-
tion of large particles, samples before filtration can be
passed through a sieve with a mesh size of 500 μm [20].
An important point is the process of moving the f loat-
ing particles from the surface of the solution to the fil-
ters and sieves. To prevent any loss of analyte associ-
ated with the adherence of particles to the walls of the
laboratory ware, it is recommended to sequentially
wash the walls of glassware directly on the filter.
Sieving. Microplastics can be isolated from samples
by sieving the latter through sieves with different mesh
sizes. The material on the sieves is further sorted, and
the remainder that has passed through the sieve is dis-
carded. The use of sieves with meshes of various sizes
makes it possible to separate microplastic particles into
several size groups. A cascade of several sieves (one to
six) with sizes of 0.038 to 4.75 mm is usually used. The
sieve material is usually stainless steel or copper.
Filters and sieved material is dried at room tem-
perature or in desiccators. The temperature in the des-
iccators varies greatly in different methods (from 60 to
90°C), but the standard [24] sets the conditions for
preparing plastic samples before testing and recom-
mends not to exceed the temperature of 50 ± 2°C, with
a drying time of 24 h with subsequent bringing the
temperature to normal conditions in a desiccator. This
is established to prevent changes in the composition
and physicochemical properties of the plastics.
Organic matter digestion. The amount of natural
organic matter (algae, zooplankton, and phytoplank-
ton and remnants of tests and shells of marine organ-
isms) in samples can significantly exceed the volume
of the analyte. Plastic particles are susceptible to foul-
ing by some forms of brown algae and bacterial film.
This can introduce an error in determining certain
physical characteristics, e.g., specific density. To elim-
inate the effect of biomaterial dissolution in alkalis,
acids, and oxidizers or decomposition by enzymes are
applied. Sometimes ultrasonic washing of plastic par-
ticles in distilled or deionized water is used to remove
possible surface contamination by sand or silt.
It is important to use proper identification tech-
niques for analysis of different size groups of plastics.
Today, visual detection methods, pyrolysis gas chro-
matography with mass spectrometry, etc. are widely
used, but the spectrometric techniques yield the most
qualitative identification results.
Identification of microplastics. Visual examination
(with the naked eye or a microscope) and sorting of
concentrated samples are often the first step in sepa-
rating plastic from organic residues and other non-
plastic waste, such as glass or resin. In the case of
visual examination without a microscope, attribution
of a particle to the plastics is usually determined by
such subjective characteristics as gloss, brightness,
unusual color, shape, structure or elasticity or hard-
ness determined by tweezers.
Microplastic particles larger than 1 mm can be
visually detected under a microscope in accordance
with the following rules [36]:
(1) Cell structure and other organic forms of parti-
cles are absent.
(2) Fibers should have uniform color and thickness
along the entire length.
OCEANOLOGY Vol. 58 No. 1 2018
(3) Particles must have a clean and uniform color.
(4) If they are transparent or a white, then they
should be examined by a fluorescence microscope at
large magnification.
In some cases, it is proposed that white, transpar-
ent, and black particles should not be accounted as
plastics, because they interfere with biological mate-
rial and other substances. This approach deliberately
underestimates the microplastic content and should
be applied with caution.
It is expedient to use pyrolysis gas chromatogra-
phy with mass spectrometry (pyrolysis GC-MS,
PyrGC-MS) and FT-IR spectrometry.
Visual methods should not be used separately from
chemical or spectroscopic ones (the latter should be
used to confirm the results of visual determination). To
identify microplastics of lower size groups, only the
spectrometric method should be used (although this
method is very time-consuming) [41]. The choice of a
representative detection method is of paramount
importance in evaluating microplastics contamination.
Microplastic particles found in a marine environ-
ment can be characterized by several criteria, such as
size, shape, specific density, color, chemical composi-
tion, and concentration in water. Therefore, micro-
plastics analysis can be divided into two main compo-
nents: morphological description with determination
of the physical and chemical characteristics of parti-
cles and quantitative analysis with determination of
the chemical composition of the polymers.
Physicochemical characteristics. Particle size is the
main characteristic, with the exception of chemical
composition. The size of a particle is usually under-
stood as its length according to the largest dimension.
The size can be determined directly, using measuring
instruments, e.g., a microscope with a graduated scale,
a digital microscope, or a caliper in visual analysis; indi-
rectly using a set of sieves with separation of a sample of
microplastics into size groups; or with combined use of
sieves and measuring instruments. The size groups of
particles assigned during the analysis depend directly on
the sampling and separation techniques used and are
related to the nominal sizes of the filters or sieves
Microplastics particles differ in shape: they can be
spherical, irregular, or long fibers. The shape of parti-
cles depends on the degree of destruction and the res-
idence time in the environment. For morphological
characterization of the surface of plastics, scanning
electron microscopy (SEM) and some of its variants
are used, but no method has yet been developed to
determine how long the particle had been in the
marine environment.
The number of categories used to classify microplas-
tic particles depends on the aim of the study and varies
greatly. The morphological description of microplastics
is based on the origin, type, shape, color, and/or degree
of degradation. The reference collections describing the
characteristics of the particles found in the sea have high
Color is one of the main characteristics of plastics
when using visual identification. The most common
color is white or close to it (faded yellow, cream-col-
ored). The color of particles can introduce uncertainty
into the extraction process in cases where plastic is hid-
den by a large number of biological residues. Particles
with bright colors are highly likely to be selected as plas-
tic, while those with faded colors can easily be missed,
thus contributing a fraction of bias to the analysis pro-
cess . Color i s used to as ses s the d egree of ph otodegrada -
tion, the residence time of a particle on the water sur-
face, and the degree of fouling and weathering.
A number of indirect characteristics, such as specific
density or color, make it possible to roughly identify the
polymer of which the particle consists. However, to
make a final decision, chemical analysis is needed
For a rough identification of the polymer type, sub-
jective characteristics such as the color of the f lame or
smell of smoke released during its burning can be used.
Although plastics belong to amorphous materials,
many of them (HDPE, PVD, PP, PET, etc.) have a
partial crystal structure and can be characterized by a
certain melting point, which can be used for an
approximate evaluation of the type of polymer. The
melting point of plastic granules can be evaluated by
differential scanning calorimetry.
To determine the specific density, it is expedient to
use the method proposed by Kolb and Kolb [30], the
method for measuring the density of noncellular plas-
tics by the titrimetric method [22], or a similar flota-
tion method [1]. However, it is worth considering that
these methods are designed to determine the density
of noncellular plastics only.
The use of such indirect characteristics as density,
color, or melting point can be useful for rapid and
inexpensive determination of the polymer type of plas-
tic granules, since the granules manufacturer describes
these characteristics. However, this approach cannot
be used for plastic fragments, since their shape and
color vary within a wider range, in particular, due to
fragmentation and erosion, and cannot be unambigu-
ously associated with a particular type of plastic.
Determination of the chemical composition of
microplastics and the type of polymer. To identify
microplastics, analytical techniques such as pyrolysis
GC-MS, Raman spectroscopy, SEM, and some of its
varieties are used, as well as IR Fourier spectrometry.
Pyrolysis GC-MS is used to assess the chemical
composition of microplastic particles by analyzing the
gaseous products of their thermal decomposition. A
polymer is identified by characteristic pyrograms, via
their comparison with reference pyrograms of known
pure polymer samples. Pyrolysis GC-MS makes it
possible to determine the types of polymers with suff i-
cient accuracy. However, in the case of analysis of
microplastics, this approach has a significant disad-
OCEANOLOGY Vol. 58 No. 1 2018
vantage: particles must be manually placed in a pyrol-
ysis tube. Since manual manipulation is applicable
exclusively to relatively large particles, this imposes a
limit on the minimum size of microplastics to be ana-
lyzed. In addition, the method allows one to analyze
only one particle per cycle, and is therefore poorly
suited for processing a large number of samples.
Raman spectroscopy is an efficient chemical anal-
ysis method. In contrast to IR-spectrometry, Raman
scattering results from inelastic scattering of light by
molecules of a substance, and scattered light differs
from the exciting one in terms of wavelength. Advan-
tages of this technology are no need for sample prepa-
ration, the ability to conduct measurements directly in
water, and the use of glass or quartz cells for measur-
ing. By combining this method with microscopic anal-
ysis, it is possible to obtain a more powerful tool for the
study of microplastics – Raman microspectroscopy,
which also provides information on the crystal struc-
ture of a polymer. Raman microspectroscopy makes it
possible to determine the type of a polymer for ultras-
mall plastic particles up to a few microns in size.
At present, IR spectrometry is most commonly
used to identify microplastics. This method compares
the IR absorption spectrum or transmission of a sam-
ple with the spectra of known synthetic substances.
For this, various spectrometric instruments are used:
an infrared spectrometer, an IR Fourier spectrometer,
and an infrared spectrometer for near-IR operation.
They can determine a wide range of polymers, e.g.,
PP, PE, and polyester. However, for microplastic par-
ticles studied on a conventional IR spectrometer,
technical difficulties arise due to the small particle
size. This problem can be solved by using micro-IR
Fourier spectrometry, as well as measurement of spec-
tra under conditions of attenuated total ref lectance
(ATR). In some cases, these approaches can be
achieved by purchasing additional equipment: a spe-
cial microscope or ATR-FTIR cells available for many
modern FTIR spectrometers. The combination of
these two approaches (micro-ATR and FT-IR analy-
ses), in addition to measuring the particle spectra,
makes it possible to add visualization and mapping of
samples and to automate the determination of the
polymer type. However, this procedure is very expen-
sive, time-consuming, and requires highly qualified
specialists; however, it is most suitable for identifying
microplastic particles and exhibits high reliability and
reproducibility. In connection with the laboriousness
of spectrometric analyzers, they are often used to
determine not all the material obtained from the sam-
ple, but only some fraction of the latter.
To increase the effectiveness of monitoring pro-
grams, it should be remembered that the choice of an
appropriate method for selecting and identifying
microplastics is crucial for assessing this type of con-
tamination [41]. When planning monitoring studies, it
is important, if possible, to adhere to the most strin-
gent requirements for sampling, preparation, and
analysis of samples while retaining the maximum
amount of information for comparison of the results
obtained by different research groups in order to esti-
mate the magnitude of the problem on a global scale.
When developing new methodological approaches, it
should be remembered that plastics are industrial
materials whose testing methods are already widely
known. These methods, with some modifications, can
be improved and implemented for analysis of micro-
plastics. Some standards [23] describe sample prepa-
ration techniques that can also be adapted for use in
this field.
We hope that this material will help other research-
ers in solving problems of estimating the amount and
dynamics of microplastics in a marine environment
and determining its role in the world pollution.
This work was supported by the Russian Science
Foundation, project no. 15-17-10020.
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Translated by G. Karabashev
... The production of plastics has increased from 1.5 million tons in the 1950s to 335 million tons in 2016 globally, while plastics are degraded, transported, and discharged into a variety of formulations in environment [1]. While plastics are rarely biodegradable, they are commonly fragmented into huge amounts of macro-, micro-, and nanoparticles through different processes and under natural conditions, making them ubiquitously harmful pollutants to the environment worldwide [2][3][4]. Therefore, the fate of plastics in the environment is determined by their physicochemical properties, including endurance, light weight, and durability in association with low manufacturing costs. These properties make plastics a unique material for the production of goods in the household, construction, and industrial sectors. ...
... These properties make plastics a unique material for the production of goods in the household, construction, and industrial sectors. According to various estimates, the worldwide annual production of plastics ranges from 275 to 299 million metric tons (Mt), whereas much lower scales of utilization and reprocessing have been reported [4]. ...
... MPs in environment make them deceptively perceived as food by many living organisms. Since MPs cannot be broken down by an enzymatic system, MPs ingestion by organisms is harmful and potentially fatal by itself [4]. However, the primary concerns arise from the fact that MPs are prone to adsorb contaminants on their surfaces, thereby becoming a secondary source of contaminants. ...
Full-text available
During the last decades, one of the most contentious environmental issues has been the investigation of the fate of microplastics (MPs) and detrimental consequences in natural and water resources worldwide. In this respect, it is critical research firstly to track the ways in which MPs are determined as key anthropogenic pollutants in terms of ecological risk and secondly to plan feasible policies under which the role of science and society in tackling this global issue in the future should be prioritized. In this study, a systematic theoretical, technical, and planning analysis was developed in alignment with a Scopus search deployed in the second half of the year 2021 and covering a wide chronological range (from 1970s onwards) and thematic contexts of analysis by using keywords and key phrases organized into two groups. The document results were graphically represented, revealing the main scientific focus of studies. Subsequently, our study investigated the quantitative assessment methods of MPs in marine environments, denoting the range of standard procedures applied for collecting and analyzing samples of water, bottom sediments, and coastal deposits. The technological part of the study includes the presentation of the relevant analytical techniques applied for MPs tracking and monitoring in water resources, determining the wide spectrum of plastic compounds traced. Of particular interest was the determination of environmental depletion and human implications caused, even by extremely low concentrations of MPs, for marine biota, posing potential risks to marine ecosystems, biodiversity, and food availability. Finally, the research proposed the challenges of actions needed to support scientific, industry, policy, and civil society communities to curb the ongoing flow of MPs and the toxic chemicals they contain into water resources, while rethinking the ways of plastics consumption by humanity.
... Sediment and agglomerated sewage water samples were collected from 12 sampling locations (upper, middle, and downstream) of four ditches (three locations on each ditch). In total 12 Kg (1 Kg on each location) of sediment samples at the top 2.5 cm of the layer were collected using a pre-cleaned stainless-steel shovel (Zobkov and Esiukova, 2018). Also, 12 L (1 L on each location) of agglomerated sewage water was collected using stainless-steel buckets (Zobkov and Esiukova, 2018). ...
... In total 12 Kg (1 Kg on each location) of sediment samples at the top 2.5 cm of the layer were collected using a pre-cleaned stainless-steel shovel (Zobkov and Esiukova, 2018). Also, 12 L (1 L on each location) of agglomerated sewage water was collected using stainless-steel buckets (Zobkov and Esiukova, 2018). Most studies focus on the MPs present in the top (0-5 cm) surface depth, as the surface layer of the compartments (Sediment and Agglomerated sewage water) are regarded as the most polluted layer (Willis et al., 2017). ...
Full-text available
Microplastics (MPs) pollution in water bodies, wastewater, and sewage is of concern due to their probable effects on the environment and human health. This study is a first-time attempt to evaluate MPs occurrence, abundance, characteristics, and polymeric types in sediment and agglomerated sewage water from several urban ditches in Bahir Dar, Ethiopia, in two class sizes (> 0.5 and < 0.5 mm). Out of the total of 239 MP particles, 61.09% were of <0.5 mm and this dominant fraction was transparent and consisted of fragmentary shapes. The mean abundances of <0.5 mm particles were 5 ± 1.00 items/ 50 g in sediment and 3.00 ± 1.00 items/50 ml in agglomerated sewage water. Similarly, the abundances of >0.5 mm fractions were 2.33 ± 0.58 items/50 g in sediment and 1.33 ± 0.58 items/50 ml in Agglomerated sewage water. Polyethylene (PE), Polypropylene (PP), polyethylene terephthalate (PET), Polystyrene (PS), polyamide (PA), and polyvinylchloride (PVC), were the most detected plastics. However, PET and PVC were not detected in the agglomerated sewage water samples.
... Since 2011, several review studies have addressed the methodologies for the sampling, pretreatment, characterization, and quantication of MPs from the aquatic environment. 31,32,[100][101][102] However, the detection, pretreatment, quantication, and characterization of MPs in aqueous water are still analytical challenges and lead to the study of unrealistic high concentrations in lab-scale experiments manifesting some misleading toxicological impacts under natural conditions. 103 On the other hand, it is difficult to compare the data obtained in the eld studies because of the lack of standard methods for sampling techniques towards the identication and quantication of MPs. ...
... Besides, SEMenergy dispersive X-ray spectroscopy (SEM-EDS) and environmental scanning electron microscopy-EDS (ESEM-EDS) have been utilized for both evaluating the morphologies of MPs and elemental analysis of polymers. 89,102 In addition to the non-destructive spectroscopic techniques, GC-MS and LC-based technologies may be employed for the quick characterization of MPs in the aqueous water. 43 Both procedures can test polymer types, and with adequate calibration, quantitative ndings can be achieved, simplifying the assessment of MP pollution. ...
Hundreds of review studies have been published focusing on microplastics (MPs) and their environmental impacts. With the microbiota colonization of MPs being firmly established, MPs became an important carrier for contaminants to step inside the food web all the way up to humans. Thus, the continuous feed of MPs into the ecosystem has sparked a multitude of scientific concerns about their toxicity, characterization, and interactions with microorganisms and other contaminants. The reports of common subthemes have agreed about many findings and research gaps but also showed contradictions about others. To unravel these equivocal conflicts, we herein compile all the major findings and analyze the paramount discrepancies among these review papers. Furthermore, we systematically reviewed all the highlights, research gaps, concerns, and future needs. The covered focus areas of MPs' literature include the sources, occurrence, fate, existence, and removal in wastewater treatment plants (WWTPs), toxicity, interaction with microbiota, sampling, characterization, data quality, and interaction with other co-contaminants. This study reveals that many mechanisms of MPs' behavior in aquatic environments like degradation and interaction with microbiota are yet to be comprehended. Furthermore, we emphasize the critical need to standardize methods and parameters for MP characterization to improve the comparability and reproducibility of the incoming research.
... Lately, MPs studies have suggested Fenton's reagent (a mixture of H 2 O 2 and ferrous ions, Fe 2+ ) as an efficient tool for isolating MPs from samples (Hurley et al., 2018;Prata et al., 2019). For some scenarios, ultrasonic cleaning of samples in a clean glass beaker filled with either ethanol or distilled water, is essential for desorbing material from MPs surface (Zobkov and Esiukova, 2018). Subsequent to organic matter removal, a separation of MPs from the matrix in air sample is carried out. ...
Micro-sized plastics were first examined for atmospheric environment in 2016. From then on, they have been detected in both indoor and outdoor atmospheric samples, with indoor environments demonstrated as containing a big proportion of these particles. The sparse distribution of these particles, is attributed to their swift and long distance transportation that is mainly eased by their tiny size (1 μm to 5 mm) and low density. Due to ongoing limitation on detectable size, analysis methods together with a lack of standardized sampling and analytical procedures, few studies were conducted on airborne microplastics (MPs). Thus, the facts regarding the occurrence, global spatial distribution, fate, and threats to ecosystem and human health of airborne MPs, are still far from being fully clarified. This literature review is a broad depiction of a state of knowledge on atmospheric MPs. Within it, robust and concise information on the sources, inspection, transport, and threats pertaining to airborne MPs are presented. Particularly, the paper entails some information concerning traffic-generated MPs pollution, which has not been frequently discussed within previously published reports. In addition, this paper has widely unveiled sectors and aspects in need of further attention, with the gaps to be filled pinpointed.
... In the Results and Discussion sections, the term "size" refers to the directly measured longest dimension of the PPs. The specific density of PPs was measured by the titrimetric method (Khatmullina & Isachenko, 2017;Zobkov & Esiukova, 2018), which was 1.045 ± 0.002 g/cm 3 . ...
To indicate the potential role of Gmelinoides fasciatus, an invasive species of Lake Onego, in the inclusion of microplastics (MPs) into food webs, several indicators were evaluated: its ability to ingest MPs, the preferred size ranges, and the ingestion intensity. For this purpose, irregularly shaped polystyrene co‐polymer particles (ABS plastics, artificially crushed) of four size classes (<50; 50‐100; 100‐250; >250 µm) were used. G. fasciatus actively ingested microplastic particles, and in treatment with particles of 100‐250 µm in size, the consumption rate was the highest. The crustaceans that survived the experiment ingested smaller particles than the deceased ones. Based on the size‐frequency distributions of the ingested particles and the same in the suspension, crustaceans preferred smaller particles than were in suspension. Mean size of the ingested particles was 100 ± 5 µm. However, considering the actual concentration of MPs fragments in the sediments of Lake Onego, in natural conditions, the negative effect of MPs fragments on G. fasciatus population is unlikely. At the same time, the ability of the invasive species G. fasciatus to consume MPs and their active integration into the food webs of Lake Onego through consumption by fish can be considered reliable factors of the entry of MPs in the fish of Lake Onego. This article is protected by copyright. All rights reserved.
... As a result, smaller-sized MPs may not be analyzed by pyrolysis GC-MS. Another limitation is that one can only analyze one MP per cycle, which could be time-consuming for a large sample volume (Zobkov et al., 2018). ...
The gravity of the impending threats posed by microplastics (MPs) pollution in the environment cannot be over-emphasized. Several research studies continue to stress how important it is to curb the proliferation of these small plastic particles with different physical and chemical properties, especially in aquatic environments. While several works on how to monitor, detect and remove MPs from the aquatic environment have been published, there is still a lack of explicit regulatory framework for mitigation of MPs globally. A critical review that summarizes recent advances in MPs research and emphasizes the need for regulatory frameworks devoted to MPs is presented in this paper. These frameworks suggested in this paper may be useful for reducing the proliferation of MPs in the environment. Based on all reviewed studies related to MPs research, we discussed the occurrence of MPs by identifying the major types and sources of MPs in water bodies; examined the recent ways of detecting, monitoring, and measuring MPs routinely to minimize projected risks; and proposed recommendations for consensus regulatory actions that will be effective for MPs mitigation.
Microplastics (MPs) are environmental pollutants of growing concern, and awareness of MPs pollution in marine and freshwater environments has increased in recent years. However, knowledge of MPs contamination in riverine sediments in Ireland is limited. To address this, we collected and analysed sediment samples from 16 selected sites along the River Barrow. Microplastics were extracted through a density separation method, after which their size, colour, and shape were analysed under a stereo microscope (Optica SZM-2). Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to identify polymer types. A total of 690 MPs were recovered from the 16 sites, with fibres as the dominant MP type. The highest concentration of MPs was 155 MP fibres kg⁻¹ wet sediment found in samples collected from Graiguenamanagh, Co. Kilkenny (GK). The majority of the recovered MPs were polyethylene (PE), polypropylene (PP), nylon, and cellulose acetate (CA) fibres. Overall, this study highlighted the presence of MPs in Irish river sediments and provided a baseline for future studies on MPs pollution. Further research is needed to better understand sources, distribution, and effects of MPs in freshwater ecosystems.
Full-text available
Understanding the impacts of microplastics on living organisms in aquatic habitats is one of the hottest research topics worldwide. Despite increased attention, investigating microplastics in underwater environments remains a problematic task, due to the ubiquitous occurrence of microplastic, its multiple modes of interactions with the biota, and the diversity of the synthetic organic polymers composing microplastics in the field. Several studies on microplastics focused on marine invertebrates, but to date, the benthic sea slugs (Mollusca, Gastropoda, Heterobranchia) were not yet investigated. Sea slugs are known to live on the organisms on which they feed or to snack while gliding over the sea floor, but also as users of exogenous molecules or materials not only for nutrition. Therefore, they may represent a potential biological model to explore new modes of transformation and/or management of plastic, so far considered to be a non-biodegradable polymer. In this study, we analysed the stomachal content of Bursatella leachii, an aplysiid heterobranch living in the Mar Piccolo, a highly polluted coastal basin near Taranto, in the northern part of the Ionian Sea. Microplastics were found in the stomachs of all the six sampled specimens, and SEM/EDX analyses were carried out to characterize the plastic debris. The SEM images and EDX spectra gathered here should be regarded as a baseline reference database for future investigations on marine Heterobranchia and their interactions with microplastics.
A method for the determination of polyorganosiloxanes (by silicon) in water using high-resolution electrothermal atomic absorption spectrometry with a continuous spectrum source and preliminary extraction of polyorganosiloxanes by benzene from the analyzed sample is proposed. The quantitative determination of polyorganosiloxanes (by silicon) was carried out on a contrAA ® 700 atomic absorption spectrometer in a cross-heating furnace. Natural water was used to optimize the parameters of the temperature – time program of the atomizer. To eliminate chemical interference during silicon determination by proposed method, graphite cuvettes were modified with a permanent modifier to form a carbide coating. A solution of sodium tungstate was used as a permanent modifier. Thermal stabilization of silicon in a graphite furnace was achieved in the presence of a mixed palladium-magnesium modifier in the nitrate form. The accuracy of the results was confirmed by spike test. The developed method of analysis was used to determine the content of polyorganosiloxanes (by silicon) in natural water. The metrological characteristics of the method were assessed in the range of determined silicon contents 0.01 – 100 mg/dm ³ .
This chapter describes types and levels of contaminants released into the marine environment due to anthropogenic activities. The main sources of contamination and physico‐chemical properties of these substances are covered, as well as the common analytical methods used for their detection and quantification. The following are the main contaminants dealt with: heavy metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, pesticides, dioxins, brominated flame retardants, surfactants, endocrine‐disrupting compounds, pharmaceutical and personal care products, microplastics and nanoparticles. Also addressed are contaminant absorption and efficiency, kinetic modelling in contaminant bioaccumulation, factors affecting bioconcentration, mussel monitoring programmes and biological markers of pollution in marine mussel species, which include enzyme reactions, specific proteins, acetylcholinesterase inhibition, lysosome membrane stability and permeability, peroxisome proliferation, morphological damage and physiological and genotoxicity markers.
Full-text available
Simplified physical models and geometrical considerations reveal general physical and dynamical properties of microplastic particles (0.5–5 mm) of different density, shape and size in marine environment. Windage of extremely light foamed particles, surface area and fouling rate of slightly positively buoyant microplastic spheres, films and fibres and settling velocities of negatively buoyant particles are analysed. For the Baltic Sea dimensions and under the considered idealised external conditions, (i) only one day is required for a foamed polystyrene particle to cross the sea (ca. 250 km); (ii) polyethylene fibres should spend about 6–8 months in the euphotic zone before sinking due to bio-fouling, whilst spherical particles can be retained on the surface up to 10–15 years; (iii) for heavy microplastic particles, the time of settling through the water column in the central Gotland basin (ca. 250 m) is less than 18 h. Proper physical setting of the problem of microplastics transport and developing of physically-based parameterisations are seen as applications.
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This book describes how man-made litter, primarily plastic, has spread into the remotest parts of the oceans and covers all aspects of this pollution problem from the impacts on wildlife and human health to socio-economic and political issues. Marine litter is a prime threat to marine wildlife, habitats and food webs worldwide. The book illustrates how advanced technologies from deep-sea research, microbiology and mathematic modelling as well as classic beach litter counts by volunteers contributed to the broad awareness of marine litter as a problem of global significance. The authors summarise more than five decades of marine litter research, which receives growing attention after the recent discovery of great oceanic garbage patches and the ubiquity of microscopic plastic particles in marine organisms and habitats. In 16 chapters, authors from all over the world have created a universal view on the diverse field of marine litter pollution, the biological impacts, dedicated research activities, and the various national and international legislative efforts to combat this environmental problem. They recommend future research directions necessary for a comprehensive understanding of this environmental issue and the development of efficient management strategies. This book addresses scientists, and it provides a solid knowledge base for policy makers, NGOs, and the broader public.
An expedition on the sailing vessel Sea Dragon was organized and carried out by the 5 Gyres Institute to explore the presence and distribution of plastic pollution in the eastern South Pacific. The first sample was taken at 33°05'S, 81°08'W, subsequent samples were collected approximately every 50 nautical miles until reaching Easter Island, and then again every 60 miles along the same transect in the direction of Pitcairn Island to 24°49'S, 126°61'W. The transect length and direction was determined by using a computer model developed at the University of Hawaii to estimate the accumulation zone for plastic pollution in the SPSG (South Pacific Subtropical Gyre). The samples were later rinsed in salt water, which floated most of the plastic to the surface for removal. Using a dissecting microscope, plastic was removed from preserved natural material, and then sorted by rinsing through Tyler sieves. Analogously, high counts and weights in samples 22 and 23 were obtained during a short period of weaker wind.
Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025. Copyright © 2015, American Association for the Advancement of Science.
Plastics can be found in food packaging, shopping bags, and household items, such as toothbrushes and pens, and facial cleansers. Due to the high disposability and low recovery of discharged materials, plastics materials have become debris accumulating in the environment. Microplastics have a dimension <5 mm and possess physico-chemical properties (e.g., size, density, color and chemical composition) that are key contributors to their bioavailability to organisms. This review addresses the analytical approaches to characterization and quantification of microplastics in the environment and discusses recent studies on their occurrence, fate, and behavior. This critical overview includes a general assessment of sampling and sample handling, and compares methods for morphological and physical classification, and methodologies for chemical characterization and quantification of the microplastics. Finally, this review addresses the advantages and the disadvantages of these techniques, and comments on future applications and potential research interest within this field.
Determining the exact abundance of microplastics on the sea surface can be susceptible to the sampling method used. The sea surface microlayer (SML) can accumulate light plastic particles, but this has not yet been sampled. The abundance of microplastics in the SML was evaluated off the southern coast of Korea. The SML sampling method was then compared with bulk surface water filtering, a hand-net (50 μm mesh), and a Manta trawl net (330 μm). The mean abundances were in the order of SML water > hand-net > bulk water > Manta trawl net. Fourier transform infrared spectroscopy (FT-IR) identified that alkyds and poly(acrylate:styrene) accounted for 81% and 11%, respectively, of the total polymer content of the SML samples. These polymers originated from paints and the fiber-reinforced plastic (FRP) matrix used on ships. Synthetic polymers from ship coatings should be considered to be a source of microplastics. Selecting a suitable sampling method is crucial for evaluating microplastic pollution.
Microplastic litter is a pervasive pollutant present in aquatic systems across the globe. A range of marine organisms have the capacity to ingest microplastics, resulting in adverse health effects. Developing methods to accurately quantify microplastics in productive marine waters, and those internalized by marine organisms, is of growing importance. Here we investigate the efficacy of using acid, alkaline and enzymatic digestion techniques in mineralizing biological material from marine surface trawls to reveal any microplastics present. Our optimized enzymatic protocol can digest >97% (by weight) of the material present in plankton-rich seawater samples without destroying any microplastic debris present. In applying the method to replicate marine samples from the western English Channel, we identified 0.27 microplastics m(-3). The protocol was further used to extract microplastics ingested by marine zooplankton under laboratory conditions. Our findings illustrate that enzymatic digestion can aid the detection of microplastic debris within seawater samples and marine biota.