Plastic Waste Carrying Rivers
Brahmaputra, Ganga, Indus Among Top 10
Out of the ten rivers that drain over 90 percent of the total plastic debris into the sea globally, there are three flowing through India – the Indus, Ganga and Brahmaputra. These plastic wastes originate not only from cities but also from villages along these riverine systems.
By Vrushal Pendharkar
Floating polyethylene terephthalate (PET) bottles, plastic bags and even toys have become a part of the marine environment in recent times. Pitiful photographs of such plastic debris washed ashore on remote shorelines have frequently made headlines. Many beaches around the world are rimmed with mounds of plastic waste.
Most of this plastic pollution is attributed to an increase in tourism, shipping and fishing activities. But according to a recent study, a considerable portion of plastic garbage afloat in the open waters originates on land, and is drained into the seas by rivers. Christian Schmidt and Stephan Wagner of the Helmholtz Centre for Environmental Research in Leipzig, Germany estimate that 57 of worlds rivers ferry between 40,000 and 4 million tonnes of plastic waste down to the open oceans every year. Just 10 of these rivers are responsible for nearly 90 percent of the plastic debris drained into the oceans. Three flow through India _ the Indus, the Ganga and Brahmaputra.
The study also finds that a combination of large rivers and huge populations along their banks are together responsible for unusually high amounts of untreated plastic waste going into the oceans.
Any action to reduce plastic in these rivers would be highly effective to reduce the total riverine inputs into the oceans, says Schmidt, the lead author of the study.
A previous study had estimated 20 rivers account for two-thirds of the global plastic waste that reaches the oceans. But according to Schmidt, for the first time, all available data on plastic in rivers have been collected and analysed to provide global numbers on riverine plastic transport.
Apart from the plastic waste found floating in the open oceans, debris from between 50 to 200 km of coastal areas is accounted for, but plastic found in the rivers is not taken into consideration by scientists working on marine issues. This leaves out plastic found in areas away from the coasts and further inland, although rivers transport plastic debris into the sea.
Another example of plastic that slips through the net is known as the missing plastic problem. This is the discrepancy between the amount of plastic believed to be in the oceans and the debris actually encountered. It is not clear yet whether particles sink or are fragmented to very small hardly detectable particles, says Schmidt.
To address such discrepancies, the researchers compiled all the available data on plastic debris in rivers. For this, they identified patterns in concentrations of plastic and the time taken for those to be transported by the river. As villages grow to become towns and towns metamorphose into cities to accommodate exploding populations, they directly have a bearing on the amount of plastic waste generated.
Schmidt and team trawled through 1,870 scientific papers and extracted 73 of them concerned with aquatic ecosystems to compile data on river plastic pollution. About 98.5 percent of the samples reported in the studies contained microplastics particles less than 5 mm in diameter. More than half the samples (55 percent) contained macroplastics, particles more than 5 mm.
The researchers also estimated population size for 1,494 catchments that drained into the seas. Taking the catchment and their population size, the team further calculated the mismanaged plastic waste generated per person every day in more than 230 countries that have river catchments draining into the sea. This is the ineptly disposed waste or garbage littered around.
The study estimates anywhere between 4.7 tonnes a year and 10 million tonnes per year of mismanaged plastic waste is generated in individual river catchments around the world. While Yangtze River in China carries the most amount of microplastic load, the San Gabriel that flows through Los Angeles carries the highest load of macroplastic.
Out of the 10 rivers that drain over 90 percent of the total plastic debris into the sea globally, there are three flowing through India the Indus, Ganga and Brahmaputra. While the Indus carries the second highest amount of mismanaged plastic debris to the sea, both Brahmaputra and Ganga together carry the sixth highest.
According to estimates computed in 2016 by the Ministry of Environment, Forests and Climate Change, 25,000 tonnes of plastic are generated every day in the country. Out of this, only 9,000 tonnes is recycled, the remaining is not even collected for processing.
To address this situation, in 2016, Plastic Waste Management Rules were introduced by the ministry. The rules put the responsibility squarely on the manufacturers of plastic both to manage the waste system as well as to buy back the plastic waste generated.
But according to Chitra Mukherjee, Operations Head at Chintan Environmental Research and Action Group, the waste management rules are very good, but the implementation is lacking.
Mukherjee thinks manufacturers should look to make non-toxic alternatives to plastic as stipulated in the Waste Management Rules. Instead, she reckons, we are recycling waste that was toxic in the first place and putting back materials that are equally toxic, like oxo-biodegradable plastic bags. These bags shed into smaller pieces overtime and have been known to cause death in aquatic life.
PET bottles, polythene bags and food sachets are not the most difficult ones to recycle. The most difficult to recycle, like shopping bags and industrial packaging material, are the ones responsible for choking rivers, lakes, or landfills, says Mukherjee.
Everyday items made of plastics are not only ubiquitous in cities but have also become commonplace in villages. Siddharth Agarwal of Veditum Foundation has walked the length of Ganga from Gangasagar to Gangotri documenting plastic pollution along the river. Speaking to grocery store owners and villagers, he found plastic has replaced materials like earthenware and tin due to its convenience and durability.
Agarwal encountered plastic all along the river, in agricultural fields and in clogged drains, except for the stretch between Kanpur and Haridwar. He documented gutka packets, sachets of everyday consumables and discarded plastic from community events as the most polluting sources in the villages.
At the United Nations Environment Assembly organised in Nairobi, Kenya, in early December 2017, India along with 193 other nations signed a resolution to reduce marine plastic waste but stopped short of adhering to specific targets in reduction. The UN hopes countries keep their promises otherwise it fears there could be more plastic than fish in the oceans by 2050. n
Citation: C Schmidt, T Krauth, and S Wagner (2017). Export of Plastic Debris by Rivers into the Sea. Environmental Science Technology 51 (21), 12246-12253. DOI: 10.1021/acs.est.7b02368
Photos: S Gopikrishna Warrier, wikimedia.
Source: india.mongabay.com
