10.2 Causes of Pollution and Eutrophy in Ganga River
10.2.1 Metal Pollution
The heavy metal pollution is gaining global attention because of their abundance,
toxicity, nonbiodegradable nature, and persistence in the environment (Fu et al.
2014). The unprecedented increase in urbanization, industrialization, and economic
development enhances the addition of heavy metals to water bodies worldwide. Both
the natural and anthropogenic sources, including rock weathering, soil erosion,
domestic and industrial effluents, agricultural leachate, coal burning, etc., contribute
to water pollution (Singh and Pandey 2014; Alvarez-Vazquez et al. 2017). Both
point and nonpoint sources contribute to metal pollution in the Ganga River (Yadav
and Pandey 2017a).
In the Ganges basin, ~2500 MLD industrial waste is generated (Trivedi 2010),
and the middle segment (from Kannauj to Varanasi) adds the largest amount of
industrial effluents to the river. The industrial sectors, including tannery, battery, and
electroplating and heavy duty in Kannauj and Kanpur city; engineering in Allahabad; and locomotives and carpet industries in Varanasi city, are considered to be
main sources of metal pollution. Tanneries alone constitute ~58% of grossly polluting industries in the middle stretch of the Ganga River. Besides this, a large amount
of metals are added through tributaries in the main river. For example, over
359 industries add their effluents to the Yamuna tributary which is finally released
to the Ganga River (CPCB 2016). Recent studies conducted in our laboratory show
long-distance atmospheric transport as well as deposition of metals in the Ganga
River (Pandey and Pandey 2009; Pandey et al. 2010). A recent study (Pandey et al.
2010) shows that the Ganga River receives 0.78–18.65 g ha
À1 year
À1 Cd, 0.48–6.28 g ha
À1 year
À1 Cr, and 152.7–447.50 g ha
À1 year
À1 Zn in Varanasi region only
through atmospheric deposition. A basin-scale study by Siddiqui and Pandey
(2019a) shows that only ~44.44% samples of Cr and 33.33% of Cd are below
their respective permissible limits of 50 and 3.0 μg L
À1 (Bureau of Indian Standards,
BIS 2012). Similarly, ~54.63% samples of Cu, ~ 66.66% of Pb, ~44.44% of Mn,
~66.66% of Fe, and ~33.33% of Ni samples along the basin have exceeded their
permissible limits.
The overall concentrations of metals in the river are influenced by multiple factors
such as the magnitude of external loading, source partitioning, chemical composition, adsorption, and episodic events driven by fluctuating river flow, sediment
delivery, and urban-industrial discharge (Yadav and Pandey 2017a; Jaiswal and
Pandey 2018). The sediment composition, redox potential, pH, and cation exchange
capacity of the system are the major determinants that regulate dissolution, precipitation, absorption, and complexation of metals in the sediment and, consequently,
their bioavailability, associated toxicity to aquatic organisms, and impact on the food
web (Jaiswal and Pandey 2018, 2019d; Siddiqui and Pandey 2019a; Verma and
Pandey 2019).
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
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10.2.1 Metal Pollution
The heavy metal pollution is gaining global attention because of their abundance,
toxicity, nonbiodegradable nature, and persistence in the environment (Fu et al.
2014). The unprecedented increase in urbanization, industrialization, and economic
development enhances the addition of heavy metals to water bodies worldwide. Both
the natural and anthropogenic sources, including rock weathering, soil erosion,
domestic and industrial effluents, agricultural leachate, coal burning, etc., contribute
to water pollution (Singh and Pandey 2014; Alvarez-Vazquez et al. 2017). Both
point and nonpoint sources contribute to metal pollution in the Ganga River (Yadav
and Pandey 2017a).
In the Ganges basin, ~2500 MLD industrial waste is generated (Trivedi 2010),
and the middle segment (from Kannauj to Varanasi) adds the largest amount of
industrial effluents to the river. The industrial sectors, including tannery, battery, and
electroplating and heavy duty in Kannauj and Kanpur city; engineering in Allahabad; and locomotives and carpet industries in Varanasi city, are considered to be
main sources of metal pollution. Tanneries alone constitute ~58% of grossly polluting industries in the middle stretch of the Ganga River. Besides this, a large amount
of metals are added through tributaries in the main river. For example, over
359 industries add their effluents to the Yamuna tributary which is finally released
to the Ganga River (CPCB 2016). Recent studies conducted in our laboratory show
long-distance atmospheric transport as well as deposition of metals in the Ganga
River (Pandey and Pandey 2009; Pandey et al. 2010). A recent study (Pandey et al.
2010) shows that the Ganga River receives 0.78–18.65 g ha
À1 year
À1 Cd, 0.48–6.28 g ha
À1 year
À1 Cr, and 152.7–447.50 g ha
À1 year
À1 Zn in Varanasi region only
through atmospheric deposition. A basin-scale study by Siddiqui and Pandey
(2019a) shows that only ~44.44% samples of Cr and 33.33% of Cd are below
their respective permissible limits of 50 and 3.0 μg L
À1 (Bureau of Indian Standards,
BIS 2012). Similarly, ~54.63% samples of Cu, ~ 66.66% of Pb, ~44.44% of Mn,
~66.66% of Fe, and ~33.33% of Ni samples along the basin have exceeded their
permissible limits.
The overall concentrations of metals in the river are influenced by multiple factors
such as the magnitude of external loading, source partitioning, chemical composition, adsorption, and episodic events driven by fluctuating river flow, sediment
delivery, and urban-industrial discharge (Yadav and Pandey 2017a; Jaiswal and
Pandey 2018). The sediment composition, redox potential, pH, and cation exchange
capacity of the system are the major determinants that regulate dissolution, precipitation, absorption, and complexation of metals in the sediment and, consequently,
their bioavailability, associated toxicity to aquatic organisms, and impact on the food
web (Jaiswal and Pandey 2018, 2019d; Siddiqui and Pandey 2019a; Verma and
Pandey 2019).
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
223