Air Pollution and Emission
The emission of gases from traffic constitutes an important source of environmental
pollution all over the world (Hofman et al. 2014). These emissions depend mainly
on the type of transport and fuel. Potential sources of contaminants associated with
railways include diesel exhaust, and the abrasion of brakes, wheels, and rails, as
well as dust from the transport of minerals and treated railway ties (Levengood et al.
2015).
The main pollutants emitted from the diesel-powered locomotives are carbon
dioxide (CO 2 ), methane (CH 4 ), carbon monoxide (CO), nitrogen oxides (NO x ),
nitrous oxide (N 2 O), sulphur dioxide (SO 2 ), non-methane volatile organic compounds (NMVOC), particulate matter (PM) and hydrocarbon (HC) (Plakhotnik
et al. 2005; Cheng and Yan 2011). Some studies reported higher levels of PM 10
(where the subscript indicates the largest diameter of the particles in microns) and
PM 2.5 near railways, higher than the standard level allowed (Beychok 2011) for the
USA, Europe, and Asia (Park and Ha 2008; Kamani et al. 2014).
A growing number of monitoring studies have used bioindicator plant species as
surrogates of air pollution across railways (e.g., Rani et al. 2006; Hofman et al.
2014). For example, Rani et al. (2006) studied the micromorphology of leaf parts of
Croton bonplandianum, Cannabis sativa and Calotropis procera along a gradient
of distances from the railway and concluded that the number of stomata and epidermal cells were lower near railways than at 4 kilometers away from the railway.
However, no statistical tests were used to evaluate the correlation between railway
distance and the number of stomata and epidermal cells. To the best of our
knowledge, Rybak and Olejniczak (2013) authored the only published study that
measured the accumulation of polycyclic aromatic hydrocarbons (PAH) in animal
species. Using Agelenids spider webs to collect dust suspended in the air, they
concluded that spiders are efficient indicators of PAHs in roads, but not in railway
viaducts due to heavier traffic in the former.
Soil Pollution
With the increase in the human population and vehicles, emissions arising from
transportation have become one of the most important sources of heavy metal,
PAHs and herbicides in the soil (Malawaka and Wilkomirski 2001; Böjersson et al.
2004). Fuel combustion, vehicular and track material abrasion, and leaked cargo
emit particles containing metals that are deposited in the soils, where they can
remain for many years due to their low biodegradability (Zhang et al. 2012).
As most products of vehicle emissions are neither biologically nor chemically
degraded, they can affect the growth of plants and ecosystems (Chen et al. 2014a,
b). In fact, plants and soil organisms are the first recipients of the emission pollutants (Malawaka and Wilkomirski 2001). Ongoing research indicates that plant
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The emission of gases from traffic constitutes an important source of environmental
pollution all over the world (Hofman et al. 2014). These emissions depend mainly
on the type of transport and fuel. Potential sources of contaminants associated with
railways include diesel exhaust, and the abrasion of brakes, wheels, and rails, as
well as dust from the transport of minerals and treated railway ties (Levengood et al.
2015).
The main pollutants emitted from the diesel-powered locomotives are carbon
dioxide (CO 2 ), methane (CH 4 ), carbon monoxide (CO), nitrogen oxides (NO x ),
nitrous oxide (N 2 O), sulphur dioxide (SO 2 ), non-methane volatile organic compounds (NMVOC), particulate matter (PM) and hydrocarbon (HC) (Plakhotnik
et al. 2005; Cheng and Yan 2011). Some studies reported higher levels of PM 10
(where the subscript indicates the largest diameter of the particles in microns) and
PM 2.5 near railways, higher than the standard level allowed (Beychok 2011) for the
USA, Europe, and Asia (Park and Ha 2008; Kamani et al. 2014).
A growing number of monitoring studies have used bioindicator plant species as
surrogates of air pollution across railways (e.g., Rani et al. 2006; Hofman et al.
2014). For example, Rani et al. (2006) studied the micromorphology of leaf parts of
Croton bonplandianum, Cannabis sativa and Calotropis procera along a gradient
of distances from the railway and concluded that the number of stomata and epidermal cells were lower near railways than at 4 kilometers away from the railway.
However, no statistical tests were used to evaluate the correlation between railway
distance and the number of stomata and epidermal cells. To the best of our
knowledge, Rybak and Olejniczak (2013) authored the only published study that
measured the accumulation of polycyclic aromatic hydrocarbons (PAH) in animal
species. Using Agelenids spider webs to collect dust suspended in the air, they
concluded that spiders are efficient indicators of PAHs in roads, but not in railway
viaducts due to heavier traffic in the former.
Soil Pollution
With the increase in the human population and vehicles, emissions arising from
transportation have become one of the most important sources of heavy metal,
PAHs and herbicides in the soil (Malawaka and Wilkomirski 2001; Böjersson et al.
2004). Fuel combustion, vehicular and track material abrasion, and leaked cargo
emit particles containing metals that are deposited in the soils, where they can
remain for many years due to their low biodegradability (Zhang et al. 2012).
As most products of vehicle emissions are neither biologically nor chemically
degraded, they can affect the growth of plants and ecosystems (Chen et al. 2014a,
b). In fact, plants and soil organisms are the first recipients of the emission pollutants (Malawaka and Wilkomirski 2001). Ongoing research indicates that plant
6 Railway Disturbances on Wildlife: Types, Effects, and Mitigation …
83