- A study found the formation of plastic-rock hybrids in the intertidal zone of remote beaches of Aves Island in the Andaman archipelago. This is a first record of these hybrid rocks, known as plastiglomerates, from India.
- Samples from the island that were analysed contained polyethylene and polyvinyl chloride. Incineration of plastic litter could have led to their formation.
- The impact of plastiglomerates on marine ecosystems is yet to be understood as research on plastiglomerates is an emerging field.
A new study by the Indian Institute of Science Education and Research, Kolkata, found the first record of plastiglomerates in the Indian sub-continent on Aves Island in the Andaman archipelago. The samples studied contained polyethylene and polyvinyl chloride mixed with rock and sand, and were possibly a result of solid waste burning in the open.
The impact of plastic on geological processes is little known and its presence in the formation of rocks is a relatively new form of plastic pollution. Plastiglomerates or plastic-rock hybrids are formed when plastic pollution mixes with organic or inorganic material and forms rocks through geological processes.
In May 2022, the researchers stumbled upon samples during a coastal monitoring survey of intertidal sandy beaches. Located at 3.5 kilometres east of Mayabunder, a town in the north Andaman district, Aves Island harbours mangroves, coral reefs, seaweed and rocky outcrops. On analysing the samples, a single plastiglomerate composed of green polyethylene and black polyvinyl chloride plastic material, was found.
Prasun Goswami, the lead author of the study, published in March this year, explained how these hybrid forms of plastic and rock are formed when the former, in the form of burnt litter, mixes with conglomerates, which are sedimentary rock made up of fragments like pebbles, sand, and silt. “If benthic organisms such as mussels or shrimp inadvertently ingest plastiglomerates, it will definitely have a toxicological effect on them,” Goswami said.
While the extent of impact on such species is yet to be studied, Punyasloke Bhadury, co-author of the study, expressed concern that this new “stone” poses an imminent danger to the rich marine biodiversity of the region.
Research on plastiglomerates is an emerging field, with only 10-15 studies published on this topic, worldwide. First reported from Hawaii in 2014, plastiglomerates have subsequently been found in Indonesia, Portugal, Canada, Peru, Brazil, and now India. The study site in Andaman extended from the inter-tidal zone to the supra-tidal zone (also called the splash zone; this area lies above the high tide line) on the coast of Aves Island.
At first glance, it is not easy for a layperson to identify if a rock is a conglomerate or a plastiglomerate. “Natural rocks near river streams could have different colour spectrums, so chemical characterisation was needed to confirm the presence of plastiglomerates,” Goswami said. With plastic entering the rock cycle and potentially remaining for thousands of years, the researchers believe that plastiglomerates act as an ‘Anthropocene marker’, which means they reflect the impact that humans are having on the planet.
However, Priti Mahesh, chief programme coordinator at Toxics Link, a Delhi-based non-profit, says it is too early to estimate the impact this recent discovery may have on the island ecosystem. Mahesh was not associated with the study.
Where did plastiglomerates originate?
“The island is remote and does not have any direct human interference. The location of the island and the pattern of the ocean current may have played a role in the formation of the plastiglomerate,” shared Bhadury.
According to the 2011 census of India, Aves Island had only one household and a population of two citizens. However, it is well-established that plastic travels through water or other channels and gets deposited in places where there is no human habitation, shared Mahesh.
The researchers believe that the plastic waste found here is brought through the deep current system in the northern part of the Indian ocean and the Andaman sea and deposited along the coastlines or trapped in intertidal areas. Bhadury shared an example saying, “We found a television set on Aves Island, which was possibly discarded into the adjacent sea from populated areas and it ended up here! The pattern of the ocean currents, waves and adjacent land-ocean boundaries are the determining factors in plastics being deposited along the coastlines of India.”
At this stage, Goswami says they cannot confirm the site of origin of the plastiglomerate analysed in the study. “To my understanding, the plastiglomerate we found does not float for long because it is dense and would submerge in the water. So, we believe it was formed on the island due to the illegal burning of solid waste. Since the island is in the open ocean, plastic dumped in other countries could also be washed ashore here. The local use of plastic is not the issue but it is possible that the locals are burning plastic to get rid of it.”
Both Goswami and Bhadury believe that plastiglomerates or such new forms of plastic pollution could be present in other areas along the Indian coasts. “Aves Island is definitely not the only place where such form of pollution exists. If we look along the Indian coast, I believe we will find more plastiglomerates. However, since this form of plastic pollution is not very well-known, creating public awareness about it is needed for more such discoveries,” shared Goswami. Their study notes that plastiglomerates may potentially form in areas where lava flows, forest fires, and extremely high temperatures occur.
Mahesh warns that remote ecosystems are more fragile and disturbance in such areas makes them more susceptible to environmental disasters. “Fragile ecosystems are dependent on all the flora, fauna and the ecosystem working in cohesion to make the ecosystem functional. In remote areas, any disturbance has a much deeper impact on the ecosystem.”
How can we mitigate the formation of plastiglomerates?
The Port Blair Municipal Council (PBMC) is the only urban local body responsible for the management of solid waste from the Andaman and Nicobar Islands. While the PBMC ensures door-to-door collection of waste from all households, there are no sewage treatment plants, and both untreated liquid waste, as well as unmanaged solid waste, are dumped into the drains.
“Our drains are being used as garbage conveyor belts taking trash from homes to the mangroves and beaches. All the major drains empty into our coastlines. The PBMC claims that all the plastic is segregated and sent to the mainland for recycling but only plastic that has recycle value gets segregated. Multi-layered plastic is not accounted for and the residents are not motivated to dispose plastic waste efficiently,” shared Tanaz Noble, a kayak instructor based in Port Blair.
Mahesh says that the plastic pollution problem is exacerbated by a lack of governance and monitoring by the authorities. Efficient solid waste management models exist within the country, in Indore, Madurai, Surat and other cities, which need to replicated and effectively enforced in other parts of the country.
Goswami also highlights that plastic pollution is a transboundary problem. “As I understand, a majority of the countries accept that the plastic pollution problem is parallel to climate change. Since plastic is primarily manufactured through the burning of fossil fuels, it is essential to reduce its production in order to address both plastic and climate change.”
Mahesh added, “Transboundary movement of plastic waste is difficult to control in the absence of a global treaty. The global plastic treaty that is being discussed and is expected to be finalised by 2024 will hopefully address these issues,” she shared.
In the meantime, experts call for better solid waste management practices at the local level. Mahesh stressed that the amount of plastic produced and used needs to be controlled. “The industry speaks about plastic as a litter issue and makes it seem like recycling is the answer. However, we must remember that there are limitations to the number of times we can recycle plastic. The focus needs to shift to how we can reduce the amount of plastic being manufactured and used.”
Read more: [Explainer] How do we recycle plastic?
Potential for future research
The findings from the present study opens up possibilities to understand the fate of plastic polymers embedded in rocks on marine biota and how plastic particles may end up in the food chain through biomagnification, says Bhadury. “Some polymers when broken down will be chemically more toxic to the environment. Polymers or chemical compounds from plastiglomerates could leach out due to natural processes and have adverse impacts on the marine environment globally,” he warned.
Goswami says that the discovery of the plastiglomerate from Aves Island could stimulate more research by marine geologists along the Indian coast. “Not only researchers, but citizens could also play a role in finding and reporting this form of pollution. As researchers, we cannot cover all the locations along the Indian coast but citizens who participate in plastic litter clean-ups could contribute as citizen scientists if mass awareness about plastiglomerates is created,” he shared.
Banner image: Evidence of a suspected green plastic fragment in a plastiglomerate from Aves Island. Photo from Prasun Goswami and Punyasloke Bhadury.