Taking a bath in sacred waters filled with trash. (Photo: Ganga Action Parivar)

Ten rivers may dump almost 4 million tonnes of ocean plastic debris

GERMANY
Monday, October 16, 2017, 22:20 (GMT + 9)

A team of scientists from the Helmholtz Centre for Environmental Research and the Weihenstephan-Triesdorf University of Applied Science, both in Germany, has found that only 10 rivers may be to blame for millions of tonnes of ocean plastic.

These researchers have calculated that these rivers, eight of them in Asia, contribute with 88 to 95 per cent of the four million tonnes of oceanic plastic debris.

The rivers that these scientists consider are to blame are the Yangtze, Xi and Huanpu in China; the Ganges in India; the Cross, bordering Cameroon and Nigeria; the Brantas and Solo in Indonesia; the Amazon, mostly in Brazil; the Pasig in the Philippines; and the Irrawaddy in Myanmar.

The scientists believe that that making more precise estimates of how much plastic is ending up in the oceans is bedevilled by unknowns including the “missing plastic” problem − the mismatch between the large estimated plastic inputs into the sea, based on what is known about plastics produced, used, recycled and dumped in landfill, and the amount actually observed in the water, as plastic concentrations in different parts of the ocean can differ significantly.

To carry out the analysis, the German team used a similar methodology employed in an earlier study, published in Nature Communications, based on work by researchers from the Netherlands-based Ocean Cleanup project.

This earlier study had calculated 1.15 to 2.41 million tonnes of plastic waste is now entering the ocean every year from rivers; 67 per cent of the global total came from the top 20 polluting rivers.

The German study compiled a larger data set – analysing plastic concentrations in 240 individual samples from 79 sites covering 57 rivers.

The researchers also classified plastic particles into those smaller or larger than five milimetres in size, and treated each cohort separately to make their calculations.

These scientists conclude that only a few river catchments contribute the vast majority of the total plastics load, targeted mitigation measures would be highly efficient.

“Reducing plastic loads by 50 per cent in the 10 top-ranked rivers would reduce the total river-based load to the sea by 45 per cent,” they state.

The study findings were published in the journal Environmental Science and Technology.
 

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