understood. Plastic materials in the ecosystem, with the passage of time, are circulating between the different environmental components – from land to fresh water
(ponds, rivers, lakes, or streams), and from fresh water to marine (seas and oceans).
This movement will be determined by the distance of travelling within the system
such as the river, between the components such from the river to the sea, and the
types of land and distanced covered. Plastic trashes on the roadside may be
disintegrated by the moving vehicles or grass-cutting equipment. The microplastics
are then drained off towards the river system, and are easily distributed among
the environmental components, as compared to the macroplastics, before entering
the marine environment (Lambert 2018). Many hydrophobic pollutants, such as
polychlorinated biphenyls, dichlorodiphenyltrichloroethane, and dioxin, may get
adsorbed on the microplastic particles, either by physisorption or chemisorption.
This eventually influence the movement and bioavailability of these pollutants, but
at the same time, concentrate all the potential toxic components in one area or
location. Microplastics are formed in a variety of freshwater matrices, and in organic
samples and sediments, the detection and identification can be highly challenging.
In fresh water monitoring, the surface water, rivers, beaches, lakes, and sediments of
rivers and reservoirs have all been shown to contain an almost consistent concentration of microplastics. The ecotoxicological studies have explored the ingestion of
microplastics by different organisms and the side effects on their lives and habitats.
Over a short term of exposure, most of the research use primary microspheres of
polystyrene and polyethylene at high concentration, to show some evidences that
microplastics indeed cause diseases in the freshwater systems. For identification, sensitive detection, and analytical confirmation of the microplastic residues and composition, the combination of physical and chemical techniques with the application
of sophisticated equipments, are required (Lambert 2018).
2.2.1 Physical and Chemical Techniques
The conventional physical techniques for preliminary identification of plastics
involve sieving, filtration, and density separation. The visual examination of the
sample and the isolation of the desired ones may require an in-depth understanding
and experience in dealing with the samples containing plastic materials. There are
three major sampling techniques – volume reduction, selection, and bulk sampling.
Oftentimes in the study of marine eco-system, the sediment samples are collected
from the coastlines, and the water samples from the seashores. Sample separation
can be achieved through density gradient, sieving, filtering, and optical sorting of
the microplastics. The mesh size sieves and filters could estimate the size distribution. The two main size ranges of the microplastics that have been reported are
500 μm–5 mm based on the 500 μm sieve/net; and 1–500 μm or fractions retained on
the filter. The optical sorting helps in determining the type, shape, degradation, and
color of plastic particles. Most of the studies have identified that the plastic fragments found in abundance in marine environment are polyethylene and
64
Z. Tahir et al.
(ponds, rivers, lakes, or streams), and from fresh water to marine (seas and oceans).
This movement will be determined by the distance of travelling within the system
such as the river, between the components such from the river to the sea, and the
types of land and distanced covered. Plastic trashes on the roadside may be
disintegrated by the moving vehicles or grass-cutting equipment. The microplastics
are then drained off towards the river system, and are easily distributed among
the environmental components, as compared to the macroplastics, before entering
the marine environment (Lambert 2018). Many hydrophobic pollutants, such as
polychlorinated biphenyls, dichlorodiphenyltrichloroethane, and dioxin, may get
adsorbed on the microplastic particles, either by physisorption or chemisorption.
This eventually influence the movement and bioavailability of these pollutants, but
at the same time, concentrate all the potential toxic components in one area or
location. Microplastics are formed in a variety of freshwater matrices, and in organic
samples and sediments, the detection and identification can be highly challenging.
In fresh water monitoring, the surface water, rivers, beaches, lakes, and sediments of
rivers and reservoirs have all been shown to contain an almost consistent concentration of microplastics. The ecotoxicological studies have explored the ingestion of
microplastics by different organisms and the side effects on their lives and habitats.
Over a short term of exposure, most of the research use primary microspheres of
polystyrene and polyethylene at high concentration, to show some evidences that
microplastics indeed cause diseases in the freshwater systems. For identification, sensitive detection, and analytical confirmation of the microplastic residues and composition, the combination of physical and chemical techniques with the application
of sophisticated equipments, are required (Lambert 2018).
2.2.1 Physical and Chemical Techniques
The conventional physical techniques for preliminary identification of plastics
involve sieving, filtration, and density separation. The visual examination of the
sample and the isolation of the desired ones may require an in-depth understanding
and experience in dealing with the samples containing plastic materials. There are
three major sampling techniques – volume reduction, selection, and bulk sampling.
Oftentimes in the study of marine eco-system, the sediment samples are collected
from the coastlines, and the water samples from the seashores. Sample separation
can be achieved through density gradient, sieving, filtering, and optical sorting of
the microplastics. The mesh size sieves and filters could estimate the size distribution. The two main size ranges of the microplastics that have been reported are
500 μm–5 mm based on the 500 μm sieve/net; and 1–500 μm or fractions retained on
the filter. The optical sorting helps in determining the type, shape, degradation, and
color of plastic particles. Most of the studies have identified that the plastic fragments found in abundance in marine environment are polyethylene and
64
Z. Tahir et al.