scientific methodology to evaluate the load of microplastics in soil in general and
agricultural fields in particular has not been standardized. Since quantification
methodology itself is not standardized, assessing its actual impact on the ecosystem
is therefore still at large. Even though few techniques are available they are time
consuming and data from different agricultural fields is seldom collected (Corrandini
et al. 2019). There are few reports available in recent times to evaluate the effect of
components of plastic on soil microflora or accumulation of microplastics in soil
conditions.
7.4.1 Microplastics in the Soil Environment
Terrestrial environment is known to receive microplastics from several sources. The
main contributor is the human activities associated with environmental sources
which are in circulation (Machado et al. 2018a). Atmospheric precipitation (Dris
et al. 2016), circulating natural water (Nizzetto et al. 2016), plastic mulches (Ng et al.
2018; Zhou et al. 2020; Huang et al. 2020), and even the compost obtained from the
domestic and industrial solid and liquid waste used as an agricultural amendment
(Weithmann et al. 2018) contribute to plastic pollution in soil. Scheurer and Bigalke
(2018) reported the presence of microplastics even in mountainous and inhabited
area up to 0.002% of soil dry weight. After reaching the soil, the process of
bioturbation provides microplastics an opportunity to get into the soil matrix (Huerta
Lwanga et al. 2017; Rillig et al. 2017; Maass et al. 2017) in association with soil
management practices (Steinmetz et al. 2016) and percolating water (Zubris and
Richards 2005) and other agriculture field related activities. Once it is done it is not
known scientifically what happens to these plastics (Machado et al. 2018b) and
hence in this connection plastic degrading rhizosphere microflora need to be
evaluated. If it is not effectively degraded it leads to accumulation in the environment and present data reveals that already 7% of microplastic weight is present in the
soil (Fuller and Gautam 2016).
Every year the amount of plastic added to soil is constantly increasing leading to
more accumulation, even traditional tillage practices increase its distribution. As the
amount of plastic is increasing even different size plastics such as macro and mega
are added to soil along with microplastic to the agricultural soils (Changrong et al.
2014; Liu et al. 2014; Rillig et al. 2017a; Steinmetz et al. 2016).
7.4.2 Quantification of Microplastic in Soil
Few techniques available to evaluate the microplastics in soil include visual sorting
of the plastics (Lots et al. 2017), use of portable spectroradiometer with range
350–2500 nm, Raman and Fourier-transform infrared spectroscopy (FT-IR)
(Crawford and Quinn 2017), pyrolysis-gas chromatography-mass spectrometry
(Pyr-GC-MS) (Ziajahromi et al. 2017), and thermal desorption GC-MS (Dumichen
et al. 2015, 2017). Even though visual sorting is considered as cheap and simpler
7 Microbe-Mediated Mitigation of Abiotic Stress in Plants
237
agricultural fields in particular has not been standardized. Since quantification
methodology itself is not standardized, assessing its actual impact on the ecosystem
is therefore still at large. Even though few techniques are available they are time
consuming and data from different agricultural fields is seldom collected (Corrandini
et al. 2019). There are few reports available in recent times to evaluate the effect of
components of plastic on soil microflora or accumulation of microplastics in soil
conditions.
7.4.1 Microplastics in the Soil Environment
Terrestrial environment is known to receive microplastics from several sources. The
main contributor is the human activities associated with environmental sources
which are in circulation (Machado et al. 2018a). Atmospheric precipitation (Dris
et al. 2016), circulating natural water (Nizzetto et al. 2016), plastic mulches (Ng et al.
2018; Zhou et al. 2020; Huang et al. 2020), and even the compost obtained from the
domestic and industrial solid and liquid waste used as an agricultural amendment
(Weithmann et al. 2018) contribute to plastic pollution in soil. Scheurer and Bigalke
(2018) reported the presence of microplastics even in mountainous and inhabited
area up to 0.002% of soil dry weight. After reaching the soil, the process of
bioturbation provides microplastics an opportunity to get into the soil matrix (Huerta
Lwanga et al. 2017; Rillig et al. 2017; Maass et al. 2017) in association with soil
management practices (Steinmetz et al. 2016) and percolating water (Zubris and
Richards 2005) and other agriculture field related activities. Once it is done it is not
known scientifically what happens to these plastics (Machado et al. 2018b) and
hence in this connection plastic degrading rhizosphere microflora need to be
evaluated. If it is not effectively degraded it leads to accumulation in the environment and present data reveals that already 7% of microplastic weight is present in the
soil (Fuller and Gautam 2016).
Every year the amount of plastic added to soil is constantly increasing leading to
more accumulation, even traditional tillage practices increase its distribution. As the
amount of plastic is increasing even different size plastics such as macro and mega
are added to soil along with microplastic to the agricultural soils (Changrong et al.
2014; Liu et al. 2014; Rillig et al. 2017a; Steinmetz et al. 2016).
7.4.2 Quantification of Microplastic in Soil
Few techniques available to evaluate the microplastics in soil include visual sorting
of the plastics (Lots et al. 2017), use of portable spectroradiometer with range
350–2500 nm, Raman and Fourier-transform infrared spectroscopy (FT-IR)
(Crawford and Quinn 2017), pyrolysis-gas chromatography-mass spectrometry
(Pyr-GC-MS) (Ziajahromi et al. 2017), and thermal desorption GC-MS (Dumichen
et al. 2015, 2017). Even though visual sorting is considered as cheap and simpler
7 Microbe-Mediated Mitigation of Abiotic Stress in Plants
237