106
D. J. Sarkar et al.
PVC, etc.) to water partitioning coefficients (log K PW ), and it was found that good correlation exists between log K OW and log K PW suggesting adsorption of the organic
chemicals on to plastic particles is driven by hydrophobic interaction (O’Connor
2016). Further, study shows that plastic particles with smaller size have better capacity to adsorb hydrophobic pollutants (Brandl et al. 2015). Beside these parameters,
the properties of surrounding media (e.g. pH, specific conductivity, etc.) also influence the adsorption process and subsequently the dissociation of chemical pollutants
from the plastic particles. Not only organic pollutants, it was also reported that heavy
metals also get accumulated on the MPs surface (Brennecke et al. 2016). The source
of these data is mainly from marine system; however, little report is available on
freshwater and terrestrial ecosystem. The accumulation of these pollutants occurs
through sorption process which may be physisorption or chemisorptions. Another
mechanism is pore-filling process, which happens when the hydrophobic pollutants
enter the polymer matrix filling the small pores. The process is highly dependent
on the pore diameter and the molecular size of the pollutants. The sorption of pollutants (either physic or chemisorption) on the MPs surface is highly dependent on
the environmental parameters viz. pH, temperature, ionic strength, etc., and polymer characteristics. MPs characteristics like polymer type, density and crystallinity,
types of additives, etc., influence the sorption kinetics (Brennecke et al. 2016). It was
postulated that sorption and diffusion of pollutants occur mostly in the amorphous
region of the plastic material as compared to the crystalline region which is more
ordered and tightly packed. For these reasons, low-density polyethylene (LDPE)
was reported to be used for passive sampling of PAHs, PCBS and other hydrocarbons from the aquatic environments (Bao et al. 2012). As compared to high-density
polyethylene (HDPE), the LDPE contains high concentration of branches that prevent the polymer chain to stack side by side resulting low crystallinity and low density
(0.90–0.94 g cm
3 ). Besides these parameters, the most important factor is particle
size of MPs which will influence the sorption parameters proportionally.
4.5 Detection of Microplastics in the Aquatic System
The analysis of MPs in the aquatic environmental samples is highly challenging and
strongly depends on the compartments viz. water phase (surface water and water
column) and solid phase (shoreline sediments, riverbed or lakebed sediments). The
process becomes more tedious with high organic loading samples. Due to organic
nature, the analytical options of MPs are limited especially when they are present in
association of other natural organic matrix. It is easy to extract the large-sized MPs
through filtering water samples or through density-based fractionation of sediments.
However, it is very difficult to separate smaller MPs or nanoplastics from the water
and sediment matrix. Moreover, the microscopic identification becomes tedious for
transparent or semi-transparent plastic particles.
D. J. Sarkar et al.
PVC, etc.) to water partitioning coefficients (log K PW ), and it was found that good correlation exists between log K OW and log K PW suggesting adsorption of the organic
chemicals on to plastic particles is driven by hydrophobic interaction (O’Connor
2016). Further, study shows that plastic particles with smaller size have better capacity to adsorb hydrophobic pollutants (Brandl et al. 2015). Beside these parameters,
the properties of surrounding media (e.g. pH, specific conductivity, etc.) also influence the adsorption process and subsequently the dissociation of chemical pollutants
from the plastic particles. Not only organic pollutants, it was also reported that heavy
metals also get accumulated on the MPs surface (Brennecke et al. 2016). The source
of these data is mainly from marine system; however, little report is available on
freshwater and terrestrial ecosystem. The accumulation of these pollutants occurs
through sorption process which may be physisorption or chemisorptions. Another
mechanism is pore-filling process, which happens when the hydrophobic pollutants
enter the polymer matrix filling the small pores. The process is highly dependent
on the pore diameter and the molecular size of the pollutants. The sorption of pollutants (either physic or chemisorption) on the MPs surface is highly dependent on
the environmental parameters viz. pH, temperature, ionic strength, etc., and polymer characteristics. MPs characteristics like polymer type, density and crystallinity,
types of additives, etc., influence the sorption kinetics (Brennecke et al. 2016). It was
postulated that sorption and diffusion of pollutants occur mostly in the amorphous
region of the plastic material as compared to the crystalline region which is more
ordered and tightly packed. For these reasons, low-density polyethylene (LDPE)
was reported to be used for passive sampling of PAHs, PCBS and other hydrocarbons from the aquatic environments (Bao et al. 2012). As compared to high-density
polyethylene (HDPE), the LDPE contains high concentration of branches that prevent the polymer chain to stack side by side resulting low crystallinity and low density
(0.90–0.94 g cm
3 ). Besides these parameters, the most important factor is particle
size of MPs which will influence the sorption parameters proportionally.
4.5 Detection of Microplastics in the Aquatic System
The analysis of MPs in the aquatic environmental samples is highly challenging and
strongly depends on the compartments viz. water phase (surface water and water
column) and solid phase (shoreline sediments, riverbed or lakebed sediments). The
process becomes more tedious with high organic loading samples. Due to organic
nature, the analytical options of MPs are limited especially when they are present in
association of other natural organic matrix. It is easy to extract the large-sized MPs
through filtering water samples or through density-based fractionation of sediments.
However, it is very difficult to separate smaller MPs or nanoplastics from the water
and sediment matrix. Moreover, the microscopic identification becomes tedious for
transparent or semi-transparent plastic particles.