MICROPLASTIC POLLUTION MODULE-I;PART-2.pptx

MICROPLASTIC AND ITS VARIOUS ASPECTS
MODULE-I
PART 2
By: SOHAIL AKBAR
B.TECH, M.E.

INTRODUCTION TO MICROPLASTICS
• Microplastic (MP) refers to any piece of plastic smaller than 5 mm to 1 μm in
size along its longest dimension.
• Plastics <1 mm in size along its longest dimension, is term Mini-Microplastic
(MMP).
• Plastic <1 μm in size is considered to be a Nanoplastic (NP).
• Due to incredibly small size of nanoplastics and thus, the difficulties in detecting
and recovering them, most studies of the aquatic environment tend to ignore
nanoplastics and only focus on microplastics and mini-microplastics.
2

WHAT ARE PLASTICLES?
• Plasticle (PLT) is a shortened version of the expression ‘plastic particles’ and was
introduced as a part of a newly developed standardized size and colour sorting
(SCS) system for the effective categorizing of microplastics, based on their size
and appearance.
• The word plasticle is an all-inclusive term used to describe any piece of
plastic smaller than 5 mm in size along its longest dimension and therefore
includes microplastics, mini-microplastics and nanoplastics.
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The standardized size categories of pieces of plastic
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For clear view, kindly copy-paste
it in ms word and read
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TYPES OF MICROPLASTICS
MICROPLASTICS (MP) MINI-MICROPLASTICS (MMP)
Palletes (nurdles) Microbeads
Fragments Microfragments
Fibres Microfibres
Films Microfilms
Foam Microform
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<5mm– 1mm <1mm– 1μm

PLASTIC PALLETES OR NURDLES
• Nurdles, or plastic pellets, are small lentil-sized pieces of plastic that are the
building blocks for most plastic products.
• Nurdles are by definition a microplastic because they are less than 5mm in size.
• They are melted down and made into many plastic items, from clothes to cars,
food wrappers to artificial Christmas trees.
• It takes roughly 600 nurdles to create one small plastic disposable water bottle.
• Nurdles are increasingly finding their way into the natural environment,
particularly the ocean, threatening a variety of marine wildlife.
• They are the second largest source of microplastics in the ocean.
7

• During manufacturing or other processes in the
supply chain (e.g. transport), a fraction of pellets
can be spilled or lost to the environment.
• Once in the environment, these small particles of
plastics do not biodegrade and cannot be removed.
• They accumulate in animals, including fish and
shellfish, and are consequently also consumed by
humans in food.
8
• They contribute to the pollution with other microplastics, which have been found
in marine, freshwater and terrestrial ecosystems as well as in food and drinking
water.
• Their continued release contributes to permanent pollution of our ecosystems
and food chains.
• Exposure to microplastics in laboratory studies has been linked to a range of
negative (eco)toxic and physical effects on living organisms.

MICROBEADS
• Microbeads are small, solid, manufactured plastic particles that are <1mm-1μm
in diameter and do not degrade or dissolve in water.
• They are mainly made of Polyethylene (PE) and Polymethyl Methacrylate (PMMA).
• In cosmetics, ‘microplastic’ refers to all types of tiny plastics particles intentionally
added to personal care & cosmetic products.
• They may be added to a range of products, including rinse-off cosmetic, personal
care and cleaning products.
• They are relatively cheap ingredient and are used in these products for a variety
of purposes including – as an abrasive or exfoliant, a bulking agent, to prolong
shelf-life, or for the controlled release of active ingredients.
9

• If washed down the drain after use, they can end up in rivers, lakes, and oceans.
• They persist in the environment and have a damaging effect on marine life, the
environment and human health. This is due to their composition, ability to adsorb
toxins and potential to transfer up the marine food chain.
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FIBRES/MICROFIBRES
• Microplastics originating from textiles typically have a fibre shape, and are
therefore often referred to as “microfibres” (<1mm – 1μm).
• A large number of materials in our daily life (e.g. furniture, textiles etc.) are made
of synthetic and natural fibers.
• Textiles are a major source of microplastic pollution.
• Textiles made of fibres of natural origin (as opposed to the synthetic fibres that
cause microplastic release) shed microfibres as well.
• Moreover, textiles can also be a source of other shapes of microplastics, originating
from the various types of materials or accessories used in clothes and textile
products, such as prints, coatings, buttons and glitter.
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• Abrasion and release of fibers from synthetic fabrics is a major contributor to
microplastic pollution.
• Shedding of >1900 microplastic fibers from washing of an individual polyester
garment resulted in >100 fibers per liter effluent water (Browne et al., 2011).
• In comparison, polyester-cotton-blends loose substantially less fibers compared to
pure acrylic or polyester fabrics.
• It is estimated that synthetic textiles are responsible for a global discharge of
between 0.2 and 0.5 million tonnes of microplastics into the oceans each year.
• According to Boucher and Friot (2017), approximately 35% of microplastics
released to oceans globally originate from washing synthetic textiles, while the
United Nations Environment Programme (UNEP) estimates it to be around 16%.
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• Although microfibre shedding decreases over
successive washes, the wearing out of fabrics as
garments age also leads to an increase in microfibre
shedding.
• As a result, fast fashion garments accounts for a
particularly high level of microfibre release, as these
typically contain a high share of synthetic fibres and
they wear out quickly.
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• Waste water treatment plants can filter out a large share — but not all — of
microfibres. However, if adequate sewage and waste water treatment systems are
not in place, microfibres will be emitted to the aquatic environment, which is
disastrous.

Microplastic fibers — threat to aquatic organisms and recommendations
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FOAM/MICROFOAM
• Polystyrene foam (<5mm) has been at the center of attention for a variety of
reasons. It piles up in landfills, causes problems for recycling centers and is a
major source of water pollution, with a damaging impact on our ocean
ecosystems.
• PS foam is a single-impact material with no market for recycling.
• As a result, polystyrene products are quickly discarded and make their way onto
beaches and into landfills.
• Single-use Styrofoam items find their way into the environment at high volumes —
represents 30% of all landfill space by volume.
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• “Polystyrene foam (Styrofoam) comprise 90% of all
marine debris, with single-use food and beverage
containers being one of the most common items
found in ocean and coastal surveys.”
• “Polystyrene brick is one of the main components of
a floating dock” – This material is typically
unencapsulated (not protected) with an outer cover
to prevent the polystyrene from breaking down into
tiny foam beads. As a result, they eventually break
down into small enough pieces to be considered
microplastics.
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FRAGMENTS/MICROFRAGEMNTS
• Microplastic fragments (microfragments) are among the most abundant
microplastics found in marine ecosystems throughout the world.
• Due to their limited commercial availability, microfragments are rarely used in
laboratory experiments.
• Typically created through the deterioration of larger macroplastic debris,
microplastic fragments (microfragments) are irregularly shaped particles
commonly composed of polyethylene, polypropylene and polystyrene.
• Microfragments, are highly variable in size.
• For example, microplastics sampled in the Delaware and Chesapeake Bays (USA)
with 200–333 µm mesh nets reported microfragments ranging from 300 to
1000 µm at concentrations averaging between 0.19 and 1.24 pieces per cubic
meter.
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• Fragmentation of plastics at sea occurs through photodegradation, physical
impacts and other processes and results in the generation of a larger number of
smaller particles.
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FILM/MICROFILM
• Plastic film is often believed to be a significant contributor to microplastic pollution
in farmland soil, however, its direct impact in areas with high human
activities remains unclear due to the presence of multiple pollution sources.
• In the context of agriculture, plastic mulch films have drawn significant attention
due to their extensive use and improper disposal.
• Large plastics can break down into smaller ones due to UV radiation, industrial
production, and other factors.
• The formed small plastics with a size of less than 5 mm are called microplastics
film, are widespread in the ecosystem.
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• The presence of Microplastics film in the terrestrial
ecosystem are much more than that in the ocean.
• They can act as carriers for pollutants
and microorganisms and affect the soil ecosystem in
many ways – can affect the structure and function of
the microbial community, causing changes in the
decomposition of organic materials, nutrient
metabolism, soil respiration, and greenhouse gas
emission.
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MICROPLASTICS CLASSIFICATION
21
INCLUDES:
Microbeads found in personal
care products,
Plastic pellets (or nurdles)
used in industries, and
Plastic fibres used in
synthetic textiles (e.g. nylon).
Others

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PRIMARY MICROPLASTICS:
• Primary microplastics are small pieces of plastic that are purposefully
manufactured. They are usually used in facial cleansers and cosmetics, or in air
blasting technology. In some cases, their use in medicine as vectors for drugs was
reported.
• Primary microplastics enter the environment directly through any of various
channels—for example, product (e.g., personal care products being washed into
wastewater systems from households), unintentional loss from spills during
manufacturing or transport, or abrasion during washing (e.g., laundering of
clothing made with synthetic textiles).

• Microplastic "scrubbers", used in exfoliating hand cleansers and facial scrubs,
have replaced traditionally used natural ingredients, including ground almond
shells, oatmeal, and pumice.
• Primary microplastics have also been produced for use in air blasting technology.
This process involves blasting acrylic, melamine, or polyester microplastic
scrubbers at machinery, engines, and boat hulls to remove rust and paint.
• As these scrubbers are used repeatedly until they diminish in size and their cutting
power is lost, they often become contaminated with heavy metals such
as cadmium, chromium, and lead.
• Although many companies have committed to reducing the production
of microbeads, there are still many bioplastic microbeads that also have a long
degradation life cycle similar to normal plastic.
23

• After the Microbead-Free Waters Act of 2015, the use of microbeads
in toothpaste and other rinse-off cosmetic products has been discontinued in the
US, however since 2015 many industries have instead shifted toward using FDA-
approved "rinse-off" metallized-plastic glitter as their primary abrasive agent.
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25
INCLUDES:
Fragments
MicroFilms (degraded from
larger plastic materials)

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SECONDARY MICROPLASTICS:
• Form from the breakdown of larger plastics; this typically happens when
larger plastics undergo weathering, through exposure to, for example, wave
action, wind abrasion, and ultraviolet radiation from sunlight.
• Over time, a culmination of physical, biological, and chemphotodegradation,
including photo-oxidation caused by sunlight exposure, can reduce the structural
integrity of plastic debris to a size that is eventually undetectable to the naked
eye. This process of breaking down large plastic material into much smaller pieces
is known as fragmentation.

• It is considered that microplastics might further degrade to be smaller in size,
although the smallest microplastic reportedly detected in the oceans at present is
1.6 μm (6.3×10−5 in) in diameter.
• The prevalence of microplastics with uneven shapes suggests that fragmentation is
a key source.
• Also, it was observed that more microplastics might be formed from biodegradable
polymer than from non-biodegradable polymer in both seawater and fresh water.
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SOURCES OF MICROPLASTICS
Percentage contribution:
• Synthetic textiles,
• Tires,
• City dust,
• Road markings,
• Marine coatings,
• Personal care products, and
• Engineered plastic pellets.
29

• Sources of microplastics
are mainly classified into
1. Land-based sources.
2. Ocean-based sources.
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Land-based sources of microplastics:
• Responsible for 80–90% of microplastics in water bodies.
• Include plastic bags, bottles, cosmetics and personal care products, construction
materials, clothing and Plastic incinerators (generate bottom ash that contains
microplastics).
• Construction materials, single-use plastics, household products, packaging items,
food and drink packaging waste, and waste generated from shipbuilding are some
of the most significant sources of larger plastic objects on land.
• Sewage sludge and industrial activities, particularly those using granules and
small resin pellets, are other probable sources of microplastic discharge into the
aquatic environment from land.
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Ocean-based sources of microplastics:
• Approximately 10–20% of microplastics discharged into the aquatic environment
come from ocean-based sources, including seaside tourism, commercial fishing,
marine vessels, and offshore industries.
• Discarded or lost fishing gear, such as plastic monofilament lines and nylon nets,
are a significant source of microplastics that can float at different depths in the
ocean. Over 600,000 tonnes of fishing gear are thrown away in the ocean each
year, contributing to the problem.
• Shipping microplastic waste, commonly released from shipping and naval vessels,
also adds to the problem.
• Moreover, a massive quantity of plastic waste from offshore industries, such as
petrochemicals, is being released into marine ecosystems. 32

DEGRADATION: BIOTIC AND ABIOTIC
• The degradation or breakdown of MP in the environment is a result of both biotic
and abiotic processes.
• MPs are broken down by living things like bacteria, fungi, and
other microorganisms during a process known as “biotic degradation”, where the
bacteria degrade the MP's by enzymatically disassembling them into smaller
pieces.
• “Abiotic degradation”, sometimes called non-biological degradation, is the
disintegration of MP through physical weathering, hydrolysis, and photochemical
reactions. Sunlight (UV radiation), temperature, mechanical stress, and
chemical reactions are some conditions that can cause abiotic deterioration.
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BIOTIC DEGRADATION AND BIODEGRADABLE PLASTICS
• Degradation of biodegradable plastics relies upon biological processes that utilize
the carbon present in the plastic as an energy source.
• However, in order for a plastic to be able to degrade, it must undergo a two-stage
procedure;
• Stage 1–Degradation
 Oxygen, moisture, heat, ultraviolet light or microbial enzymes break the carbon–
carbon bonds of the long polymer chains resulting in fragmentation of the
plastic.
 The degree to which these various factors have any effect depends upon the
molecular structure of the polymer.
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• Stage 2–Biodegradation
 Once the polymer has fragmented sufficiently, the shorter carbon polymer
chains are able to pass through microbial cell walls.
 The carbon in the chains is then utilized as a food and energy source by the
microbes, before being converted to biomass, water, carbon dioxide or methane
gases.
 Ultimately, this depends upon whether the conditions are aerobic or anaerobic.
However, it is the conversion of this carbon by microbes that signifies that
biodegradation has indeed occurred.
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• In order for a plastic to be considered biodegradable, this two-step process of
degradation must take place at an acceptable rate and not have a negative impact
on the surrounding environment in which the biodegradation is taking place.
• Thus, the inherent value of a biodegradable plastic depends upon its effects
on the environment, such as
1. the effect on biota,
2. the stability of soil conditions,
3. the emission of methane gas, and
4. the contamination of ground water.
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Some popular “biodegradable plastics” are:
1. Polyhydroxybutyrate (PHB):
 PHB is a thermoplastic which belongs to the polyester class of compounds.
 PHB is insoluble in water and thus has better resistance against hydrolytic
degradation than other biodegradable plastics, which are soluble in water or
sensitive to moisture.
 Furthermore, the material exhibits good resistance to ultraviolet light.
 There are many items available which are made from PHB, such as
shampoo bottles, cups and golf tees.
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2. Polycaprolactone (PCL):
 Has a low melting point of 60°C and is therefore unsuitable for high temperature
applications.
 However, it is occasionally blended with other plastics to improve impact
resistance or plasticize PVC.
 Owing to its biodegradative properties in the human body, which occurs at a
slower rate than polylactic acid (PLA), there is considerable research underway
to develop implantable devices or sutures that can remain in the body for long
periods of time before breaking down when no longer required.
 Furthermore, the encapsulation of drugs with PCL for controlled and targeted
drug delivery systems has been successfully accomplished
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3. Polylactic acid (PLA):
• Derived from lactic acid, PLA has a large variety of applications, such as product
packaging material, tableware and feedstock material for desktop 3D printers.
• Owing to the substances ability to degrade to the innocuous lactic acid
monomer, PLA is used within the human body for medical implants, such as pins,
rods and screws.
• In the body, PLA completely degrades within 6–24 months, depending on the
precise composition.
• Furthermore, lactic acid can be copolymerized with glycolic acid to create
poly(lactic-co-glycolic acid) (PLGA), a biodegradable and biocompatible polymer.
PLGA can be used for the targeted delivery of drugs within the body, such as the
antibiotic amoxicillin. 39

• When these biodegradable plastic materials are discarded into the environment,
complete biodegradation takes about 2 weeks in the case of discard into a
sewage treatment facility and approximately 2 months in the case of discard
into soil or aquatic environments.
40
The degradation, and
subsequent biodegradation, of
a polylactic acid bottle.
DAY 1 DAY 28 DAY 38 DAY 58 DAY 80

Plastic degrading insects, fungi and other microorganisms:
• Some insects will consume plastics to reach a food source, such as cockroaches
chewing through plastic bags containing bread.
• Similarly, woodworm have been found to have bored into PVC when the
material has been in close contact with wood. While these insects are not
consuming plastic materials for energy, an example of true ingestion and
biodegradation of a plastic material by an insect have been recently documented.
• In a study, it was reported that the larvae (waxworms) of the Indian mealmoth
are capable of consuming thin polyethylene films. Following ingestion of the plastic,
the bacterial strains present in the gut of the waxworms (Enterobacter asburiae
YT1 and Bacillus sp. YP1) were discovered to have degraded some of the
polyethylene film.
41

• Upon inspection, by way of scanning electron microscope (SEM), it was observed
that 0.3–0.4μm pitting had occurred on the films surface.
42
Fig: Waxworms consuming
polyethylene film.

• Microorganisms, such as “sulphur bacteria”, can form biofilms on plastic
materials and secrete sulphuric acid. Similarly, acids can be secreted by some
species of fungi.
• This can have a detrimental effect on a minority of plastics which are susceptible to
acids, such as polyamides (Nylons).
• Endophytic fungus – discovered in the Amazon rainforest – was found to contain a
serine hydrolase enzyme that allowed the fungus to feed solely on polyester
polyurethane (PUR) in an aerobic, as well as anaerobic (oxygen-free), environment.
• Bacillus subtilus, Bacillus pumilus and Kocuria palustris pelagic bacteria are
capable of biodegrading low-density polyethylene (LDPE) in vitro.
43

ABIOTIC DEGRADATION
• Abiotic degradation of plastics refers to the weathering of plastic materials from
environmental factors, such as mechanical force, temperature, light, gases and
water.
• When exposed to the weathering elements, plastics undergo mechanical
disintegration, and experience freeze-thaw cycles, pressure changes, water
turbulence and damage caused by animals.
• This mechanical breakdown, nonetheless, differs from degradation, as the
molecular bonds do not change and the materials simply endure morphological
modifications.
44

Photo-oxidative Degradation:
• Photo-oxidative degradation refers to the breakdown of plastics by light.
• Microplastic litter on land, such as beaches, or floating on the surface of the ocean
will inexorably be exposed to large amounts of direct sunlight and thus suffer the
effects of exposure to high intensity ultraviolet light (UV) for significant periods of
time.
• Most plastics tend to be susceptible to UV light because they contain photo-
reactive groups, termed “chromophores”. These groups readily absorb high-
energy UV radiation, which results in the breaking of chemical bonds.
• However, there are some exceptions.
45

• For example, PVC has good resistance to UV light simply because it does not
possess the relevant UV chromophore.
However, PVC still exhibits some degree of photo-sensitivity. This is
suspected to occur as a result of abnormalities in the polymer matrix, such as the
presence of C═O and O—O groups.
• Mechanism: Photo-oxidative degradation of a plastic material occurs when
photons of ultraviolet (UV) light, particularly in the UVB region (315–280 nm) of the
electromagnetic spectrum initiate the process of decomposition of the plastic by
way of the free radical polymer chain reaction.
• While UV light tends to have a minimal effect on the propagating steps of the
radical chain reactions, progression of the degradation can continue, even after UV
exposure has been discontinued, as a result of induced thermal-oxidative
decomposition. 46

• As a result, the mechanical properties of the plastic can be significantly impaired,
even from as little as 1% oxidation.
• Common signs of photo-oxidative damage to plastics are yellowing, hazing,
cracking and embrittlement.
• The plastic may also start to exhibit a colour shift and take on a noticeably
bleached chalky appearance on any areas which have been exposed to
sunlight, in comparison to areas which have been shielded.
• An example of photo-oxidative degradation of a small fragment is shown in the
next slide.
47

• Initially, the fragment (shown) had a patch of fouling
covering part of its surface.
• Once this fouling was removed, then apparently the
dark region underneath the fouling becomes
protected from sunlight while the regions exposed to
the sun had oxidized and turned white.
48
• Thus, to protect against such oxidative damage, plastics are typically stabilized
with the addition of chemicals, such as carbon black hydroxybenzophenone or
amines which have been sterically hindered to impart ultraviolet resistance and
permit outdoor use.

The resistance of common plastics to ultraviolet light
49

Atmospheric Oxidation and Hydrolytic Degradation:
• Atmospheric Oxidation: The presence of oxygen in the atmosphere can catalyze
the breakdown of some plastic materials. For example, PVC degrades via the
removal of hydrogen chloride (dehydrochlorination) to form double bonds.
• However, this decomposition process tends to only occur down to a maximum
depth of 1 mm from the surface exposed to the environment.
50

• This is because the oxygen in the atmosphere is unable to permeate to any further
reaction sites beyond that depth. As such, PVC is only partially vulnerable to
atmospheric oxidation.
• However, if the environment is particularly dynamic, such as the interactions of
waves and rocks, the surface of the PVC may become pitted and abraded, thereby
revealing new reaction sites which are suitable for oxidation.
• Nevertheless, oxygen is not the only gas that can attack plastics. In urban
environments, high levels of industrial and domestic activity result in greater levels
of pollutants in the atmosphere, in comparison to rural and remote regions.
• Consequently, ozone and oxides are produced and several of these pollutants can
have degradative effects on plastic.
51

• For example, when polyethylene and polypropylene are exposed to sunlight in
the presence of atmospheric oxygen and the pollutant sulphur dioxide,
crosslinking of the polymer chains occur. Similarly, Nylon 6,6 is susceptible to
attack by the pollutant nitrogen dioxide.
• Hydrolytic Degradation: When some plastic materials are submerged in water,
diffusion of the water into the amorphous regions of the plastic occurs. In some
plastics, such as polytetrafluoroethylene, there is only negligible absorbance
while in others the rate of absorption is considerable, such as with Nylons.
• However, the diffusion of water into the polymer matrix can result in the addition
of water molecules to the polymer by way of the cleavage of chemical bonds
(hydrolysis).
52

• For example, the polyester polyethylene terephthalate (PET) is hydrolyzed at
temperatures above the glass transition temperature (73–78°C) in which a scission
reaction, catalysed by oxonium ions or hydrogen ions produced by the carboxyl
end groups, breaks the primary bonds of the polymer chain resulting in irreversible
damage. Other plastics that suffer the effects of moisture are polyurethanes.
53

DISTRIBUTION AND FATE OF MICROPLASTIC IN THE
ENVIRONMENT
• Determining the fate of microplastics in the environment is inherently difficult,
mainly due to their small size. Moreover, the vast array of ways through which
these materials enter the environment, as well as the timescales necessary to
ascertain their degradation, make their accurate quantification rather difficult.
• As an artificial product, plastic sources are mostly inland. Nonetheless, due to
their discharge in domestic and industrial wastewaters, transport by wind and
surface run-off, up to 80% of these materials end up in the oceans – due to the low
density of the majority of plastic materials.
• Driven by winds and ocean currents, plastic debris can be transported across vast
distances and these materials can be found throughout the oceans, including the
North and South Poles, remote islands and the deep ocean. 54

• However, microplastics have been found to be considerably more
preponderant in coastal areas than in offshore regions, something that can be
attributed to anthropogenic activities, namely, in populated areas with intensive
industrial and commercial activities.
• In spite of the low density of the most commonly used plastics, including PE, low-
density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene
(PP) (Table 1), plastic debris can be found throughout the water column.
• When directly released into the aquatic environment, particles made up of
materials with a specific gravity >1 tend to sink and those with a specific
gravity <1 tend to remain buoyant.
55

• Nonetheless, these materials’ densities may vary along the time due to
heteroaggregation, and also due to other phenomena, including microbial
colonization (biofouling).
56

Concentrations of plastic debris in oceans’ surface waters. Different colours
indicate distinct concentration ranges
57

• Generally, a typical sample of microplastic will be composed of several different
types of plastic. However, the most common types of plastic encountered in the
aquatic environment are polyethylene, polypropylene, polystyrene,
polyethylene terephthalate and polyvinyl chloride.
• Out of these, the three most common types of microplastic in the aquatic
environment are polyethylene, polypropylene and polystyrene.
• Once microplastics enter the aquatic environment, their behaviour tends to falls
into three categories:
1. Physical behaviour, such as accumulation, sedimentation and migration.
2. Chemical behaviour, such as the adsorption and absorption of pollutants.
3. Biological behaviour, such as ingestion by biota, translocation and trophic
transfer.
58

59
An overall representation of environmental fate of plastics

Microplastic Pollution in Terrestrial Environment
• MPs enter soil from varied sources including land application of sewage sludge,
organic fertilizers from composting, improper waste disposal, use of plastic mulch
film and greenhouse covering in agricultural applications, irrigation with MP-
enriched polluted water, and from atmospheric deposition.
• Soil applied with sewage sludge for 15 years had much greater concentrations of
plastic fibres than soil where no sewage had been applied.
• Furthermore, a study of earthworms (Lumbricus terrestris) found that <150
μm polyethylene microplastics in the litter reduced growth rate and
increased mortality of the worms at concentrations in the litter of 28%, 45%
and 60% dry weight.
60

Microplastic Pollution in Terrestrial Environment
• In a study of industrial sites in California and Hawaii, the samples of microplastics
collected were found to be composed of polypropylene (80–90%) and polyethylene.
• In a study, which collected atmospheric fallout using stainless steel funnels in 20 L
glass jars and subsequently identified the material with infrared spectroscopy,
between 2 and 355 microplastics per m2 per day, were reported to deposited.
• Furthermore, it was estimated that 29% of the microplastics were synthetic fibres
and over the course of a year, between 3 and 10 tonnes of fibres would be
deposited from the atmosphere over a 2500 km2 area.
• Consequently, atmospheric fallout may well be another route in which
microplastics can reach the aquatic environment in significant volumes.
61

Microplastic Pollution in Freshwater Environment
• MPs enter rivers and are often eventually transported to oceans.
• Depending on hydrodynamics, however, freshwater ecosystems can also act as
sinks, and retain a substantial proportion of MP inputs.
• Reported values of MPs in freshwater ecosystems vary greatly, from near-zero to
several millions of particles per cubic meter.
• These differences are attributed to geography (i.e., sampling location), types of
human activities, and sampling methods used.
• Hydrologic conditions also affect concentrations of MPs.
• In urban and non-urban watersheds, the concentrations of MPs are believed to be
higher during runoff events than those under low-flow conditions.
62

• MPs data in freshwater has addressed – lakes, reservoirs, and some major rivers.
• An expedition of the US Great Lakes determined that all samples except one
contained plastics; the frequency of occurrence among Lake Superior, Lake Huron,
and Lake Erie were 100%
• Among the top six largest lakes in Switzerland, all samples contained MPs,
which were found in beach sediments, lake, and river surfaces, 87.5%, and 100%,
respectively.
• In surface water samples collected from four estuarine tributaries of the
Chesapeake Bay, MPs were found in 59 of 60 samples.
63

• Concentrations of MPs in freshwater systems are highly variable, likely a
consequence of several factors including particle size, human population density,
economic and urban development, waste management practices, and hydrologic
conditions.
• An inverse relationship between MP concentration and particle size has been
observed in many studies of rivers, lakes, and oceans i.e., as the particle size
decreases the concentration of MP increases and vice versa.
• Wastewater treatment plants (WWTPs) are recognized to be a significant source of
MPs to freshwater.
64

Microplastic Pollution in Marine Environment
• Marine life is more disturbed by plastic waste because ocean become a dump yard
for running water system either directly via riverine system as river ultimately
end up meeting with the ocean or indirectly as waste water treatment plant
dispose of their waste directly in the ocean or in river which end up by meeting the
marine water body.
• However, the size of sediment and distribution of MP is influenced by oxidative
degradation (either photo- or thermal initiated), friction and biodegradation.
• The typical shape of microplastics consists of pellets, fibers and fragments, but
majority of microplastics in Oceans are microfibers.
65

• Distribution and abundance of microplastics is chiefly determined by
environmental and anthropogenic factors.
• Environmental factors include: runoff, infiltration, river discharge, wind action,
ocean currents, cyclones, river hydrodynamics, wave current, tides and
movement/dispersion of animals.
• Anthropogenic factors include: either industrial or tourism or transport activities
which further led to accumulation of plastic debris in environment.
• The environmental factors play vital role in determining the distribution of
microplastics more intensely than anthropogenic activities, however anthropogenic
activities are the core source of production of these plastic wastes.
66

• Abundance of microplastics in oceans distribute across various strata of Ocean.
• In the sediments-water systems, microplastics only sink and accumulate in the
sediment when their density exceed seawater (>1.02 g/cm3); otherwise it tends to
float on the sea surface or in the water column.
• Hence low density microplastics float on surface layer of ocean water whereas high
density microplastics sinks down to benthos layer.
• Buoyancy of microplastics can depend on befouling in which former biomass
accumulation led to increase in microplastics density and later can decrease
microplastics density which is responsible for sinking, neutral or floating action of
microplastics.
67

• Beaches serves as a reservoir of highly fragmented plastic debris that
transport microplastics back to costal water and finally to open ocean.
• The concentration of microplastics is usually higher in upper layer i.e. epipelagic
layer than the immediate lower mesopelagic layer; this may be due to preferential
flow or animal movement.
• Usually, sea platforms and marine trafficking are responsible for microplastics in
far off Ocean, whereas microplastics in near shore originate mostly from waste
water, runoffs, rivers etc.
• Terrestrial environment also determines the concentration of microplastics as
harbor and industries add huge amount of plastic debris either directly or
indirectly which add up to the accumulation of microplastics in the ocean.
68

The global abundance of microplastics in marine surface waters and sediments
• Ultimately, the concentration of microplastics in the aquatic environment is
expected to increase dramatically in the coming years, mainly as a result of the
increasing production of plastic materials, the mismanagement of plastic
waste, the influx of microbeads from industry and consumer products via
effluent and the degradation of large plastic litter.
• Nevertheless, many regions of the world have introduced legislation aimed at
reducing the use of light-weight plastic bags. Consequently, this legislation
significantly helps towards alleviating the number of plastic bags which end up in
the aquatic environment and the potential for their breakdown into microplastics
or their ingestion by marine biota.
69

70
The global abundance of plastics in surface waters and sediment in the marine environment

Microplastic Pollution in Snow
• Recently in 2022, Scientists have found Microplastics in freshly fallen Antarctic
snow for the first time on land surface, which can influence the climate
by accelerating melting of ice.
• Finding microplastics in fresh Antarctic snow highlights the extent of plastic
pollution into even the most remote regions of the world.
• Researchers gathered samples of snow from 19 different sites in the Ross Ice
Shelf in Antarctica and discovered plastic particles in all of them.
• There were 13 different types of plastic found, with the most common
being PET (Polyethylene Terephthalate), commonly used to make soft drink
bottles and clothing. The possible sources of microplastics were examined.
71

• An average of 29 microplastic particles per litre of melted snow, which is higher than
marine concentrations reported previously from the surrounding Ross Sea and in
Antarctic sea ice.
• Origin: Microplastics in Antarctica may originate from both local sources and long-
range transport. Direct sources of microplastics to the Antarctic environment may
include fragmentation of plastic equipment from research stations, clothing worn by
base staff and researchers, and mismanaged waste. Microplastics may also enter the
Antarctic environment via long-range transport by ocean currents, ocean to
atmosphere exchange, and both short- and long-range atmospheric transportation.
Wastewater treatment plants (WWTPs) have been identified as a source of entry of
microplastics to the environment worldwide and so to the Antarctica. 72

What are the Implications of this Finding?
• Both Local and Wider Effects:
– Microplastics can have harmful substances stuck on to their surfaces such
as heavy metals, algae.
– So they can provide a way in which harmful species can make it into some
remote and sensitive areas, that otherwise wouldn't get there.
– Humans inhale and ingest microplastics via air, water and food. High levels of
ingested microplastics in the human body have the potential to cause
harmful effects, including cell death and allergic reactions.
73

• Can lead to Global Warming and other Disasters:
– Microplastics may be increasing the impact of global warming. Scientists say
dark-coloured microplastics deposited at these locations can make things
worse by absorbing sunlight and enhancing local heating.
– Clean snowpacks, icefields and glaciers can reflect much of the sunlight, but
other polluting particles such as black carbon (have also been found on icefields
and glaciers of the Himalayas) – and scientists say they accelerate the melting
there.
– The rapid thinning and retreat of glaciers also poses a threat to water supplies
and agriculture in mountain regions around the world.
74

Microplastic Pollution in Atmosphere
• The presence of MPs in the air has been reported from different regions and in air
masses over water bodies, demonstrating MPs’ capability of long-range transport
and wide spatial distribution away from their source of origin.
• Few studies, have looked at MPs in “atmospheric aerosols – which are being
identified as a significant pathway for inhalation of MPs by humans and animals”.
• A recent study suggested that MPs can be transferred up to a distance of ~95 km.
• MPs in the air are released from: wear and tear of clothing material, by washing
and drying, erosion of synthetic rubber tires, deterioration of house furniture,
emissions from the synthetic textile industry, emissions from vinyl chloride and
polyvinyl chloride (PVC) industries, and contamination from city dust.
75

• In addition, substantial
quantities of plastics are being
burned in open landfills on a
daily basis, which results in
the volatilization of various
harmful compounds that
inevitably integrate into the
atmospheric aerosol.
76
Fig: Sources of microplastics in the atmosphere and their
health implications.

HEALTH IMPLICATIONS OF ATMOSPHERIC MICROPLASTICS
• Studies have reported Localized inflammation and genotoxicity among humans
due to inhalation of MPs.
• Smaller MPs affect human pulmonary system – fibers up to 250 µm were detected
in the human lung.
― reduced lung capacity, coughing, and breathlessness were observed.
• MP deposition is more likely to occur in the upper airway tract (i.e., nose, mouth,
and throat) when inhaled and would reach the gut if ingested.
• Fine MPs are believed to translocate to the circulatory system and other organs.
77

SAMPLING OF MICROPLASTICS
• The analysis of microplastics in the environment starts with sample collection as a
first step.
• Selection of an appropriate sampling technique/method is essential as it will
determine the types of microplastics that are collected, separated, identified and
subsequently reported.
• The method of sample collection is influenced by many factors. However, primarily
the matrix to be sampled (water, sediment, soil, air or biota) will determine
the abundance, size and shape of the microplastics obtained. There are no
universally accepted methods for sampling any of these matrices and the methods
available all have potential bias.
78

• Importantly, with any sampling strategy, the cost benefit is an essential
consideration.
• Thus, the methods used should be simple enough to allow for replication and
reproducibility, as well as being cheap enough to be accessible, while ensuring
precision, accuracy and minimal contamination.
STANDARDIZATION OF SAMPLE COLLECTION TECHNIQUES
 While there is no standardization for collecting microplastics, the standardized
size and colour sorting (SCS) system for the effective categorizing of
microplastics, based on their size and appearance are most commonly used.
79

 To effectively monitor microplastics in the environment, the collection of
microplastics from the environment shall require standardization through the
development of standard operating procedures (SOPs) and rigorous quality control
measures.
Ques. The abundance of microplastics in environmental samples, or the concentrations
used in laboratory based experiments, are often expressed with differing units of
measurement, which in some cases can be incomparable. (Why??)
 In general, the abundance of microplastics is commonly presented either as a
numerical or mass concentration.
80

 In case of water samples, the abundance of microplastics is expressed as the
weight or number of microplastics per area (such as km2 for sea surface samples)
or per volume (such as m3 for water columns).
 In case of sediments, the abundance of microplastics is recorded as the weight or
number of microplastics per sediment area or weight [wet weight (ww) or dry weight
(dw)], as well as volume (mL or L).
 This wide variation in the way in which the abundance of microplastics are
quantified shows that the comparisons between studies is often very difficult. For
that reason, it has been suggested that environmental studies should provide
sufficient information to allow unit conversion and that preferably both numerical
and mass concentrations are provided.
81

SAMPLING METHODS
• There are three main sampling methods used for recovering microplastics from
the environment, each has its own advantages and disadvantages:
1. Selective sampling.
2. Volume reduced sampling.
3. Bulk sampling.
• In many cases, more than one sampling method are used, particularly where both
water and sediment samples are required.
82

Selective Sampling:
 In this, items visible to the naked eye are directly extracted from the environment,
such as on the surface of the water or sediment.
 Advantage: This method is adequate in situations where different microplastics of
similar morphology and of a size greater than 1 mm are present, such as primary
microplastic pellets and similarly shaped secondary microplastics.
 Limitation: more heterogeneous items are often overlooked, particularly when they
are mixed with other beach debris. Despite this, selective sampling has been
extensively used and is reported in 24 of the 44 studies involving the extraction of
microplastics from sediment.
83

Volume Reduced Sampling:
 In this, the volume of the bulk sample is reduced until only the specific items of
interest for further analysis remains. Thus, the majority of the sample is discarded.
 Advantage: This method is typically utilized to collect samples from surface water
because it has the advantage that large areas or quantities of water can be
sampled.
 Limitation: the disadvantage of volume reduced sampling is that, discarding the
vast majority of the sample introduces the risk of underrepresentation of the
abundance of microplastics in the sample due to the potential loss of
microplastics.
84

Bulk Sampling:
 In this, the entire sample is taken without reducing its volume.
 Has Practical limitation pertained to the amount of sample that can be collected,
stored and processed.
 Theoretical advantage of this method is that, all the microplastics in the sample
can be collected, regardless of their size or visibility. Furthermore, processing the
full sample prevents any microplastics from being lost or overlooked during the
sampling process, as can happen in selective sampling or volume-reduced
sampling.
 Additionally, the reduction in handling of the sample can also help to decrease any
contamination by reducing the amount of time that the sample is exposed to the
surrounding environment.
 While this method was undertaken in 1 seawater study and 18 sediment studies, it
has been used less frequently in more recent studies.
85

ENVIRONMENTAL PARAMETERS
• When collecting samples in the environment, it is important to take into
consideration and to record the prevailing weather conditions, not only on the day
of sampling but in the period leading up to sampling.
• On the day of sampling, it is necessary to note the wind direction as this may
influence any potential contamination from the person carrying out the sampling,
as well as from others nearby.
• Furthermore, the time of sampling in relation to the tidal height (be it diurnal or
semi-diurnal) should also be noted, as should the stage in the tidal cycle.
• These will impact the sampling of both water and sediment from marine and
estuarine environments. 86

ENVIRONMENTAL PARAMETERS
• It has been reported in several studies that increased rainfall prior to sampling
can have a significant positive impact on the amount of plastic debris
observed, particularly in tropical areas, and where there is a freshwater influence.
• Certainly, the quantity of debris entering the marine environment is reported to
increase with rainfall, and a significantly greater abundance of neustonic plastic
litter has been observed within some coastal surface water following storm events.
• Thus, documentation of the prevailing weather conditions is necessary when
sampling for microplastics and is particularly important when sampling in the
marine environment.
87

CONTAMINATION MITIGATION STRATEGIES
• The contamination of a solid or liquid environmental sample with microplastics
that were not originally part of that sample is one of the major issues involving the
examination of samples.
• Indeed, the processes involved in the collection, separation and identification of
samples for microplastics often result in the inadvertent introduction of
microplastics that would not otherwise be found in the sample.
• For e.g., Mini-microplastics (particularly microfibers) can be introduced from the
ambient air, but also via the use of sampling or laboratory equipment, improper
storage of samples or even from the clothing of the researchers themselves.
88

CONTAMINATION MITIGATION STRATEGIES
• In many cases this contamination can compromise the analysis, leading to
overestimations of the abundance of microplastics in the sample.
• For this reason, several methods have been suggested to help reduce this type of
contamination. For e.g.,
― During sample collection, samples should always be collected downwind to
prevent air borne contamination and collected, transported and stored using
non-plastic tools or containers, such as aluminium trays.
― When handling samples, synthetic clothing should always be avoided and
natural fibers, such as cotton should be worn wherever possible.
90

― Samples should have to be kept covered to reduce exposure to the ambient air
and the processing of samples in a clean room or sterile laminar flow hood may
be particularly effective, although this is not likely to be practical in many
instances.
― Particular attention needs to be paid in the laboratory during sample handling
or processing and all equipment and laboratory surfaces should be cleaned with
alcohol and then rinsed with distilled water before use.
― Some forensic techniques such as the detection of solid particulate matter on
surfaces using adhesive tapes can be used effectively.
― The concentration of solid airborne particulates during the analysis of
microplastics can be monitored using dampened filter paper and glass petri-
dishes 91

Conclusion: A strict contamination mitigation protocol,, should be adhered to
when collecting and handling samples for microplastic analysis.
Indeed, it has been demonstrated in several studies that when adequate
cleaning is undertaken, the abundance of background fibers is considerably
reduced.
92

SAMPLING IN AQUATIC ENVIRONMENT
• Microplastics are commonly found in most water bodies and the strategy used to
collect water samples for the examination of microplastics depends upon the type
of aquatic environment to be sampled.
• In terms of their distribution in aqueous environments and owing to their
physiochemical properties, such as variations in density, shape and chemical
composition, microplastics can be found floating on surface waters, suspended in
the water column or in the depths of the ocean.
• The specific location of the microplastics in the water shall influence whether
horizontal sampling along the water’s surface is required, or whether vertical
sampling through the water column is needed. 93

• Key parameters to be considered for Aquatic Sampling:
1. The physical environment to be sampled (e.g., area, depth, flow),
2. The type of sample to be collected (positively buoyant upon the water surface,
negatively buoyant at depth or neutrally buoyant in between), and
3. The sampling method to be employed (vertical or horizontal towing or pumping
from the water column).
94

• The choice of sampling strategy depends upon the purpose of the study:
95

SAMPLING IN AQUATIC ENVIRONMENT – FRESHWATER
• Both lentic (relatively still) and lotic (flowing) freshwater systems are
influenced by the same physical forces, such as wind and water currents, which
can influence the transport and accumulation of microplastics in the marine
environment.
• However, since bodies of freshwater (for. E.g., lakes) are generally smaller in size,
the influence of these forces may be greater, thereby resulting in potentially larger
spatial and temporal differences in the mixing and transport of microplastics.
• Furthermore, site-specific physical drivers, such as advective transport
(influenced by velocity) and diffusive/dispersive transport (influenced by
turbulence), can have an impact on the distribution and concentrations of
microplastics in the fresh water environment and will greatly be influenced by
geology and relief.
96

SAMPLING IN AQUATIC ENVIRONMENT – FRESHWATER
• 6 studies of microplastics in freshwater systems were being done by in large – with
one in Asia, three in Europe and two in North America. All these studies used nets
with mesh sizes of 300–800 μm for collecting samples and the collection
techniques were similar to those used in the marine environment.
• When sampling freshwater, it is particularly important to provide a good
characterization of both the water body studied and the surrounding area,
describing land use and possible sources of pollution. Furthermore, in freshwater
environments there may be a larger amount of organic debris in comparison to
marine waters, particularly from vegetation – which may add up to the complexity.
97

SAMPLING IN AQUATIC ENVIRONMENT – ESTUARIES
• Estuaries – transitional zone between river and the marine environment.
• They are subject to both marine influences (tides, waves and saline water) and
riverine influences (flowing freshwater), which form a partially enclosed body of
brackish water that is connected to the open sea. They are typically close to urban
areas and therefore have been identified as ‘microplastic hotspots’.
• However, little is known regarding the characterization of microplastics in
estuarine ecosystems, or on the influence of estuarine salinity gradients on the
transportation and deposition of microplastics.
• As with freshwater sites, the prevailing weather, such as wind and rainfall, has
been proven to play a significant role in influencing the distributions and
abundance patterns of microplastics within the estuarine environment.
98

SAMPLING IN AQUATIC ENVIRONMENT – MARINE
• The vast majority of sampling for microplastics has occurred in the marine
environment, which ranges from the relatively shallow coastal littoral zone that can
be heavily influenced by tides, to the abyssal oceanic pelagic environment.
• Due to the vastness of the oceans and the wide variation in the abundance of
microplastics in these waters, volume reduced techniques are generally practiced.
• As with freshwater systems, samples from marine waters can either taken from the
surface of the water or from within the water column.
99

AQUATIC MARINE ENVIRONMENT SAMPLING – SURFACE WATER SAMPLING
• Most common method for sampling microplastics in surface waters – Plankton
Sampling – utilize monofilament nylon mesh plankton nets of various designs.
• Occasionally, alternative methods, such as a Rotating Drum Sampler, have also
been used.
• The most common type of net used for microplastic sampling in surface waters is
the “neuston net”.
― commonly used for the horizontal sampling of both the epineuston (organisms
which live in the air on the surface film of the water) and the hyponeuston
(organisms which live just beneath the water’s surface).
100

101
Fig (a): A neuston net, used to sample surface waters.

AQUATIC MARINE ENVIRONMENT SAMPLING – SURFACE WATER SAMPLING
• Certainly surface sampling works best in calm flat waters, but in more open
waters where the depth of the net may vary considerably, the use of a more stable
manta trawl or catamaran is recommended.
― The manta trawl has wing-like structures on each side of the net to maintain
stability and buoyancy in the water, whereas
― The catamaran has two runners on each side of the net to provide stability and
buoyancy.
• Typical sizes of the net used for the collection of microplastics range from 53 μm to
3 mm with the most frequent size being 333 μm.
102

103
Fig (b): A manta trawl
Fig (c): A catamaran

AQUATIC MARINE ENVIRONMENT SAMPLING – WATER COLUMN SAMPLING
• Uses techniques and equipment developed for zooplankton sampling in both the
marine and freshwater environments.
• The mesh size of zooplankton nets is typically larger than plankton nets.
• Typical size of the nets used for the collection of microplastics is 500 μm and at a
depth of 1–212 m.
• The water column can be sampled both horizontally and vertically.
104

Horizontal sampling of the Water Column
• For sub-surface horizontal sampling of microplastics, a “bongo net” is used.
• It comprises of a pair of circular aluminium frames connected to a central axle to
which a flow meter and pair of nylon plankton nets are attached.
• The net is lowered to a chosen depth, often just above the bottom, and towed at
this depth at a set speed for a set amount of time and then recovered.
• For example, lowering the net to 212 m depth at a rate of 50 m per minute, then
trawling for 30 seconds, and then recovering the net at a rate of 20 m per minute.
• Various depths can be trawled to establish where in the water column
microplastics of different densities are located. 105

106
Fig: A bongo net, used for horizontal or Vertical sampling of water column

Vertical sampling of the Water Column
• For vertical sampling of microplastics, the net is either pulled up towards the
surface from a specified depth to give an overview of the entire water column. This
can be done by pulling a bongo net upwards.
• However, in rough waters, the vessel will pitch and roll thereby pulling on the net
briefly and then releasing it, resulting in slack in the towing wire.
• To compensate for this, a spring mechanism can be fitted between the towing wire
and the bongo net to compensate for the motion of the vessel and ensure the net is
pulled upwards at constant speed. The water column can also be sampled
vertically by opening and closing at discrete depth layers.
107

Vertical sampling of the Water Column
• For example, using a modified multiple-net tucker trawl, which is a messenger
operated closing net, allows specific depth layers to be sampled without
contamination.
• Other techniques can also be used for the sampling of microplastics from the water
column, such as direct in situ filtration and bulk sampling with subsequent
filtration.
• Furthermore, the use of a Continuous Plankton Recorder (CPR) can be used to
sample from 10 m depth.
108

Schindler-Patalas Plankton trap
• Developed for sampling planktons which in turn is used to sample microplastic.
• Working:
 Initially the container is lowered to the desired depth in the water column.
 The device can then be closed under the control of the operator to allow sample
collection at a chosen depth.
 Consequently, quantification is precise as a known volume of water is sampled.
 Limitation: due to the small volume of the containers, they may require a large
number of replicates to give a more precise estimate of abundance.
109

110
Fig: The Schindler-Patalas plankton trap, used for sampling the water column
for microplastics.

QUANTIFICATION AND IDENTIFICATION OF SAMPLES
• Accurate quantiﬁcation of MPs is done by counting them in order to express
results as particle number, providing at the same time the evaluation of their size,
colour, and shape distribution.
• Not all particles are visible to the naked eye; therefore, the use of a
stereomicroscope is necessary for a preliminary visual sorting. This process
requires considerable time and resources in terms of researchers involved in
counting hundreds of particles per sample and a high risk of data overestimation
for false positives.
• To this purpose, recently, researchers tried to develop automatic image analysis
approaches for time-efficient, accurate and harmonized data analysis
111

• The spectroscopic methods (FTIR and Raman) are the most commonly used for the
chemical identiﬁcation of MPs.
• These techniques are nondestructive, and therefore, after sample acquisition it is
possible, for example, to further process the bigger particles with other techniques
(e.g., Py–GC–MS) to obtain additional and complementary information on the
composition of plastic polymers.
• Moreover, a minimal amount of sample is required, given that these methodologies
are able to identify different types of polymers at a resolution from about 10µm
(FTIR) to 0.5µm (Raman) by comparing the IR spectrum of an unknown plastic
sample with spectra of known polymers provided by matching them to spectral
libraries through database comparison algorithms. 112

• FTIR and Raman spectroscopy identifies MP particles via their vibrational
spectrum, which is unique for every polymer type.
• Coupling the spectrometer (FTIR or Raman) to a microscope, small particles are
measurable (100µm–1µm) through the “micro”-spectroscopy (µ-FTIR and µ-Raman).
• Methodologies/instruments used for the characterization/identification of
MPs and their advantages and disadvantages will now be discussed.
• Py–GC–MS stands for Pyrolysis–Gas Chromatography–Mass spectrometry. It’s a
Powerful technique for mass determination.
113

Fourier-Transform Infrared (FTIR) Spectroscopy
• FTIR is highly accurate in identifying the type of plastic present by producing
highly specific infrared (IR) spectra which contain distinct band patterns, thereby
allowing differentiation between plastic materials and natural materials.
• The technique relies upon the actuality that most molecules absorb light in the
infrared region of the electromagnetic spectrum.
114

• With a wavelength longer than that of visible light, and just outside the red region
of the visible spectrum, infrared light exhibits a wavelength of 750 nm–1 mm.
• If a sample is irradiated with a beam of infrared light, analysis of the elements
such as carbon, hydrogen, nitrogen and oxygen can be undertaken by measuring
the degree to which the molecules in the sample absorb specific wavelengths of the
infrared light.
• The photons which make up the infrared light may be absorbed by the sample
(absorption) or may not interact with the sample and pass straight through
(transmittance).
• The molecules of the sample which absorb photons gain energy and as a
consequence, the bonds of the molecules will distort more energetically by means
of bending and stretching (see Fig). 117

118
Thus, infrared spectroscopy is a technique
which irradiates a sample with specific wavelengths of
infrared light and then examines the transmitted light to
deduce the amount of energy that was absorbed by the
molecules at each wavelength, thereby providing
information about the molecules present in the sample.
By measuring the amount of absorption of
infrared radiation at different frequencies, it is possible
to generate an absorption spectrum that can provide
insight concerning the molecular structure of the
sample.

• Different types of plastic have unique combination of atoms, no two plastic
materials will produce an identical IR spectrum.
• For this reason, FTIR spectrums are unique to each type of plastic and can be used
to positively identify the type of plastic that a microplastic is composed of.
• Since FTIR collects spectral data at a high resolution over a wide range of spatial
frequencies (typically 4000–600 cm−1), the technique is particularly suited for
identifying the different groups of specific atoms (functional groups) in a molecule.
119

120
Fig: Fourier-transform infrared (FTIR) spectrometer

• Infrared spectroscopy can be problematic with regard to the preparation of
samples. Thus, suitable processing of the sample is required to allow the
transmission of infrared radiation.
• This can be achieved in three ways:
1. Suspension of the polymer within a compressed potassium bromide (KBr)
disc that is transparent to infrared light.
2. Dispersion of the polymer in mineral oil.
3. Dissolution of the polymer in a solvent.
• The KBr method is predominantly difficult because in that the attainment of a
suitably transparent disc requires a very specific set of conditions to be met.
121

• For this reason, relatively large pieces of plastic are best analyzed by using a
reflectance technique, such as Attenuated Total Reflection (ATR).
• Attenuated Total Reflection (ATR): it requires that the sample to be in
sufficiently close proximity to a small crystal to allow penetration of infrared
radiation into the sample. This can be achieved by making use of a clamp to press
the sample against the crystal.
• The crystal is typically composed of either germanium (Ge), diamond or zinc
selenide (ZnSe).
• Once in contact with the crystal, an evanescent wave propagates 0.5–5 μm past
the crystal surface and into the surface of the sample.
122

123
Fig: Attenuated total reflection (ATR)
Limitations of ATR technique:
The material being analyzed must have
a refraction index which is lower than the
crystal, otherwise infrared light will be lost to
the sample.
Furthermore, the degree to which a
sample is in contact with the crystal directly
affects the intensity of the observed bands. This
is because shorter wavelengths cannot
penetrate deeply into the sample.

FTIR Microscope:
• Used for microplastics < 500 μm, an can be utilized in three different modes, such
as transmittance, reflectance and ATR.
• This allows the collection of a spectrum from a sample, as well as mapping of the
sample and even simultaneous visualization.
• Modes of operation:
1. Transmission mode: in this, light from the source passes through the sample,
and transmitted energy is measured to generate a spectrum. Therefore, it
requires the transparency of the filter substrate and minimum thickness for the
tested MP particles.
124

2. Reflectance mode: in this, the incident beam passes back through the sample by
reflection on an IR reflective substrate. Reflection may also take place within the
material and thus could cause a measurable signal even for thick and partly
absorbing materials; however, the reflected signal is often disturbed by reflection
errors caused by light scattering on the morphological properties (size, shape,
refractive index) of the MP particle.
3. ATR Mode: in this, an ATR accessory operates by measuring the changes that
occur in an internally reflected IR beam when the beam comes into contact with a
sample. The sample is placed in optical contact with ATR crystal, and the surface
is irradiated with an evanescent wave induced in the crystal material interface.
(continued on next slide)
125

When the sample absorbs energy, the evanescent wave will be
attenuated. The attenuated beam returns to the crystal, then exits the opposite
end of the crystal, and is directed to the detector to generate IR spectrum.
The penetration depth (dp) of light through the sample using ATR is
not constant and it depends on the corresponding wave-numbers and the
refractive indices of sample and ATR crystal. It is estimated as follows:
126
Where, λ is the wavelength of incident light;
ns and nc are refractive index of sample and crystal,
respectively; and θ is the angle of incidence.
As seen, dp is proportional to the wavelength and
therefore inversely proportional to the wave-number.

127
Fig: Fourier-transform
infrared (FTIR)
microscopy

• The FTIR microscope is capable of molecular mapping analysis which is useful for
detecting microplastics in sediments without the need for visual identification.
• However, due to refractive errors, this has proven extremely difficult with
irregularly shaped microplastics.
• Consequently, the FTIR microscope has to be used in ATR mode to identify
irregularly shaped microplastics, such as microfragments.
128

• (FTIR) spectroscopy reference spectra for plastic materials: Figure shows the
comparison of transmission and ATR mode based on FTIR spectra of polystyrene,
polypropylene, and polyethylene. Sample thickness in the range of 50–100 μm
129

Advantages of FTIR:
 Easy to use.
 Many particles can be analyzed simultaneously.
 Automatization available.
 Short time of analysis for single particles.
 Evaluation of size and shape.
 Detecting the intensity of oxidation.
 Report particles with shape and size information.
 Efficient transmission and reflection mode.
 Nondestructive technique.
130

Disadvantages of FTIR:
 Difficulty in characterizing black particles.
 Long time of analysis to measure multiple particles.
 Measures huge areas without particles.
 Detectors have to be cooled with liquid nitrogen.
 The analysis requires expert personnel.
 Huge data sets (several GB per filter).
 No total mass determination.
 Expensive.
131

Raman Spectroscopy
• In this, the identification of microplastics can be done by directing a beam of
monochromatic laser light (incident beam) onto the sample in question which
results in some of the light becoming absorbed, reflected or scattered.
• The scattered light is collected, headed towards a detector, and transformed into a
characteristic spectrum, which can then be interpreted.
• The vast majority of scattered light is in the form of Rayleigh scattering and has the
same frequency as the incident light; on an average, only one photon in every 30
million will be inelastically scattered.
• The number of inelastically scattered photons is proportional to the size of the
molecular bonds.
132

133
Fig: Raman Spectroscopy
A great advantage of Raman spectroscopy over
FTIR spectroscopy is that water tends to have a
negligible effect on the technique since the very
small bonds present in a molecule of water will
scatter very few photons.

Raman Spectroscopy
• With respect to the frequency of the
incident beam, Raman inelastically
scattered light can have an increased
frequency towards the blue end of the
electromagnetic spectrum (anti-Stokes
shift), or a decreased frequency towards
the red end of the electromagnetic
spectrum (Stokes shift).
• This change in frequency equates to the
vibrational frequency of a molecular bond.
134

Raman Spectroscopy
• Raman spectroscopy permits the observation of very slight variations in:
1. the polymers molecular conformity.
2. the degree of crystalline regions, with respect to amorphous regions.
3. the stereoregularity of the polymer.
• For these reasons, Raman spectroscopy is recognized as an excellent choice in the
analysis of polymer morphology and provides valuable information about
orientation effects and the crystalline structure of the polymer.
• Like FTIR spectroscopy, Raman spectroscopy is also a non-destructive technique
that does not affect the sample.
135

Raman Spectroscopy
• Raman spectroscopy can also be coupled to microscopy (Raman
microspectroscopy) to identify microplastics as small as 1 μm.
• Thus, the great advantage of Raman spectroscopy is the ability to provide
structural and chemical characterization of samples as small as 1 μm, which other
spectroscopic techniques cannot achieve.
136

• Raman spectroscopy reference spectra for plastic materials:
137
Intensity
(counts)

• Raman spectroscopy reference spectra for plastic materials:
138
Intensity
(counts)

Raman Spectroscopy
• Different measurement modes for analysis of microplastics with Raman
microscopy:
1. Manual particle by particle measurement.
2. Automatic measurement (Raman mapping and automatic particle detection).
• In manual particle-by-particle analysis, the operator must choose each item,
which should be analyzed and start each Raman measurement separately.
Thereby, measurement parameters can be adjusted individually for each particle to
obtain high quality Raman spectra.
• To facilitate automatic measurement, one might use Raman mapping or
automatic particle detection and measurement. For both, a motorized microscopic
stage and appropriate software is necessary.
139

Table: Advantages and disadvantages of different measurement modes for analytics of
microplastics with Raman microscopy
140

Table: Advantages and disadvantages of different measurement modes for analytics of
microplastics with Raman microscopy
141

Exemplary illustration of Raman mapping and automatic particle detection and
measurement of microplastics on an aluminum coated polycarbonate membrane filter
(magnification 50x532 nm, acquisition 2x2s); (a) microscopic images for Raman
mapping with measuring grid with a spot distance of 2 μm, (b) microscopic image
converted to grey scale for automatic particle detection, the center of each recognized
particle is marked with a red spot. 142

Advantages and limitations of Raman Spectroscopy for
microplastic analysis
143

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