that the Chinese Yangtze River catchment is the largest contributor, followed by the Ganges River catchment. With the growing awareness in recent years, some studies are focusing on Asian rivers (Blettler et al. 2018; van Emmerik et al. 2019a; Jambeck et al. 2015; OCMCBE 2015). Surface samplings at the Chinese Yangtze River mouth showed considerably higher plastic concentrations than any other sampled river worldwide (Zhao et al. 2014), with a reported 4137 particles per cubic meter. The significant differences between sampled estuarine concentrations and nearshore monitoring in the area confirmed that the Yangtze River is a major regional source of plastic input into the marine environment. Kataoka et al. (2019) reported of the MP concentrations on 29 Japanese river surfaces, which may be a source of MPs for the MP hotspot in the East Asian seas. They found MPs in 31 of the 36 sites and demonstrated that concentration of MPs in the river basins were dependent on population density, urbanization, and biological oxygen demand (BOD), which suggested that river water quality and plastic pollution in rivers are related.
2.5.3 The Problem of Freshwater Microplastics in Developing Countries
The problem of freshwater plastic pollution occurs more in developing countries due to the lack of proper waste management systems in these countries. As a result, the waste is directly disposed of into open areas or water bodies like rivers, from which they reach the oceans (OCMCBE 2015; Kaza et al. 2018). As observed by van Emmerik et al. (2019a), rivers in South East Asia are known to be major contributors of plastic waste into the marine ecosystem, but with no proper observation and monitoring of these riverine plastic wastes, the sources and fate of these MPs remain unknown. The current research on freshwater plastic pollution is mainly focused on the developed countries with almost no proper monitoring in the developing countries (Blettler et al. 2018; Blettler & Wantzen 2019). This disparity is mainly because the countries doing quality research in sciences (especially experimental) are countries with a high‐income economy (OECD 2017). From an environmental perspective this cannot be sustainable, as the developing countries are generating the largest amount of solid wastes due to high population growth and high consumption rate, with no proper solid waste management (UNHSP 2016). Furthermore, many developed countries are dumping their solid wastes by exporting to these low‐income countries, adding to the environmental issues in these countries. Lastly, the largest river drainage systems are located in these countries (Latrubesse 2008) and they are now recognized as the largest potential contributors of plastic to the marine ecosystem. Thus, due to these reasons, extensive quantification and monitoring of sources and transport pathways, as well as fluxes of riverine MPs in these countries is urgently required.
2.5.4 Status of India's Freshwater Plastic Problem
The plastic consumption rate among the Indian population is among the highest in the world, and results in the generation of approximately 5.6 million tons of plastic waste per year (Toxics Link 2014). Not surprisingly, India is described as the twelfth largest contributor of marine plastic pollution in the world (Jambeck et al. 2015), but very few studies to date have investigated the presence of MPs in the water or sediment in freshwater or estuarine environments in India. Recently there have been a few studies on MPs pollution in India but most of these studies are on coastal or marine sediments (Jayasiri et al. 2013; Reddy et al. 2006; Robin et al. 2020; Suman et al. 2020) and studies on fresh water environments are almost non‐existent (Table 2.1). Owens & Kamil (2020) carried out a study of plastic pollution in a river in Kerela, India (Karamana River) and Indonesia (Tukad Badung River).
In one of the first reports on MPs in the freshwater environments in India, Sruthy & Ramasamy (2017) studied the sediments of Vembanad Lake, a Ramsar site in India with low‐density polythene dominating the sediment samples. The authors pointed out that as the locals consume the aquatic fishes and clams from this lake, the fate of MPs entering humans via the food web is a potential threat. Ram & Kumar (2020) studied MPs from Sabarmati River sediments, where they reported that higher amount of MPs were observed in the river in areas near landfill sites from where the surface runoff might have carried the plastic debris to the river. Sarkar et al. (2019) estimated distribution of meso‐ and microplastics in the sediments of the lower reaches of the river Ganga, where they observed a relation between MPs abundance and other water quality parameters such as BOD. Karthik et al. (2018) studied MPs particles at beaches along the southeast coastal region of India, where they found the highest abundance of MPs on beaches adjacent to the river mouth. They also found the MPs in 10.1% of the 79 fishes they studied. Reddy et al. (2006) reported the observed plastic debris in the marine sediments on the coast of Gujarat, and a group of researchers reported plastic particles in the beaches of Mumbai (Jayasiri et al. 2013). Veerasingam et al. (2016) studied the MPs in surface sediments along the Chennai coast during March 2015 (pre‐Chennai flood) and November 2015 (post‐Chennai flood) and found that the MPs in the sediments increased threefold in post flooding, which may be due to huge input of MPs through the Cooum and Adyar rivers during the flood. This study highlights the importance of rivers as sources of plastic pollution to the marine environment.
Table 2.1 Concentrations and sizes of microplastics reported in samples from freshwater environments (studies from India).
| Sl. No. | Location | Average concentration | Method | Sample type | Size | Polymer type | References |
|---|---|---|---|---|---|---|---|
| 1 | River Ganga | 11.48–63.79 ng/g | FT‐IR | Sediments | 63–850 μm, 850 μm–5 mm | PET, PE | Sarkar et al. (2019) |
| 2 | Sabarmati River | 134.53–581.70 mg/kg | SEM | Sediments | 4 mm–75 μm | Plastic debris and fibers | Ram & Kumar (2020) |
| 3 | Vembanad Lake | 0.27 g/l | Raman | Sediments | 0.2–1 mm | *HDPE, LDPE, PP, PS | Sruthy & Ramasamy (2017) |
| 4. | Netravathi River | 288 pieces/m3 (water), 96 pieces/kg (sediment) 84.45 pieces /kg (soil) | – | Water, sediments, and soil | 5–0.3 mm | PE, PET | Amrutha & Warrier (2020) |
* Low‐density polyethylene (LDPE) High‐density polyethylene (HDPE).
In India, plastic litter is documented to have caused serious damage to biodiversity in places like Cochin, Lakshadweep, Sutrapada, Vembanad Lake, Chilika Lake, Mandapam, Kilakkarai, Erwadi and Periyapattinam. There are multiple cases of ingestion and entanglement from plastic debris leading to mortality of marine mammals and birds in the country. The tourism and fishing industries are significant contributors of plastic pollution in India, especially in the coastal areas, as these areas are being affected
