Mapping Microplastics Along The Ganges River Basin

Combined flows from the Ganges-Brahmaputra-Meghna river basin could send up to three billion microplastics each day into the Bay of Bengal.

AsianScientist (Feb. 22, 2021) – Combined, the Ganges-Brahmaputra-Meghna river basin accounts for up to three billion microplastic particles entering the Bay of Bengal on a daily basis, according to new research. The findings were published in Environmental Pollution.

Originating in the Himalayas and emptying into the Bay of Bengal, the Ganges is not only the most sacred river in Hindu tradition; it’s also the world’s most populous. Along with the Brahmaputra and Meghna rivers, over 655 million inhabitants rely on the water provided by the combined river basin.

Despite the river basin’s central importance to religion and livelihood, it is also one of the world’s most heavily polluted waterways. Every day, untreated human and industrial sewage flows through drainage canals and into the rivers—compromising the health of the humans and wildlife that depend on them for survival.

Over two expeditions in 2019, the National Geographic Society’s Sea to Source Ganges expedition set to map the microplastics generated by human activities along the Ganges-Brahmaputra-Meghna river basin. The first of its kind so far, the expedition was led by researchers from the University of Plymouth, along with colleagues from the Wildlife Institute of India and University of Dhaka, among others.

During the pre-monsoon (May to June) and post-monsoon seasons (October to December), the researchers collected 120 samples by pumping river water through a mesh filter to capture any particles. The samples were gathered across ten sites, ranging from Harsil—a village closest to to the Ganges’ source—to Bhola in southern Bangladesh where the river basin meets the Bay of Bengal.

The team identified microplastics in 71.6 percent and 61.5 percent of the pre-monsoon and post-monsoon samples, respectively. More than 90 percent of the microplastics found were fibers, with clothing materials like rayon (54 percent) and acrylic (24 percent) as the most abundant.

Pre-monsoon samples collected at the river basin’s mouth in Bhola also had four times as many particles compared to those taken at Harsil. Meanwhile, post-monsoon samples had double the amount—reflecting the impacts of increasing human activity along the rivers.

By combining predicted microplastic concentrations with the discharge rate, the researchers concluded that between one and three billion microplastics are likely released from the river basin every day.

“Globally, [around] 60 billion pieces of plastic are discharged into the ocean from rivers worldwide each day. What has been lacking until now is a detailed analysis of how microplastic concentrations vary along a river’s course,” shared lead author Dr. Imogen Napper from the University of Plymouth. “These results provide the first step in understanding how [the Ganges-Brahmaputra-Meghna river basin], as well as other major rivers, may contribute to oceanic microplastic.”

The article can be found at: Napper et al. (2021) The Abundance and Characteristics of Microplastics in Surface Water in the Transboundary Ganges River.


Source: University of Plymouth; Photo: Sara Hylton/National Geographic.
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