The plastic wrap

From the deepest ocean trenches to the peaks of the highest mountains, plastics can now be found everywhere, and figuring out how to manage them has become a pressing problem.

Several new studies have been released this week addressing the global plastic problem. One predicts how airborne microplastics will have an impact on the climate, another maps the waste washed up on Australian shores, and yet another has found that microplastics are entering the environment from wastewater.

Here’s what they’ve uncovered.

Airborne microplastics are changing the climate

Microplastics are tiny pieces of plastic debris less than five millimetres in length, formed when larger pieces break down. They are in our rivers, oceans and soils, and over the past few years, scientists have realised they are even our atmosphere, transported around the world by winds.

Not much is known about airborne microplastics or their impacts, but we do know that aerosols in the atmosphere – including dust and greenhouse gases – can absorb, emit and scatter radiation, and so their presence can have cooling or warming effects.

Now, new research from the University of Canterbury in New Zealand has modelled how airborne microplastics affect our climate.

An antenna in bushland with blue sky above
Airborne microplastic sampling underway at Kaitorete Spit in Canterbury, New Zealand. Credit: Alex Aves

“We studied how microplastic fragments and fibres – two types of microplastics commonly found in the atmosphere – interact with light, and used this information in a global climate model to calculate the overall impact of airborne microplastics on Earth’s climate,” explains atmospheric chemist Laura Revell, who led the study, published in Nature.

Revell and team found that microplastics are efficient at scattering sunlight, and so they have a minor cooling effect in the Earth’s lower atmosphere.

“However, they can also absorb radiation emitted by the Earth, meaning that they contribute, in a very small way, to the greenhouse effect,” she adds.

“The actual magnitude of microplastics’ influence on climate varies in our climate model simulations, depending on assumptions we made about how microplastics are distributed throughout Earth’s atmosphere. Because airborne microplastics research is so new – microplastics were reported as being in the air only a few years ago – we had a very limited number of studies to inform our research.”

But the influence of microplastics in the atmosphere is only expected to increase with growing plastic consumption. Five billion tonnes of plastic waste has accumulated in landfills and the natural environment to date, which is predicted to double over the next 30 years. As this plastic degrades, it will inject more microplastics into the atmosphere.

“Unless as a species we take serious action to address microplastic pollution, plastic production and waste-management practices, then the abundance of microplastics will continue to increase, and airborne microplastics could contribute to future changes in climate,” Revell concludes.

Trash tides washing up on Australia

Australian researchers have analysed data of coastal debris collected over the past decade to find that 84% of all rubbish found on our beaches is plastic.

Woman collecting plastic from a beach
Plastic picked up from a beach in Gippsland, Victoria, Australia. Credit: Joel Sharpe / Getty Images

The study used data collected by more than 150,000 citizen scientists, who logged their clean-up efforts as part of the Australian Marine Debris Initiative launched in 2004. Over the years, more than 20 million pieces of rubbish have been submitted.

Now researchers from the University of New South Wales (UNSW) have mapped the trends of this debris, focusing on a 10-year period when the database registered clean-ups nationwide.

“The AMDI Database contains entries of beach clean-ups across Australia, but the added value of this database is that volunteers take the time to categorise what they find, sorting and counting the amounts of plastic, glass, rubber, metal, paper and other items,” explains study lead author Jordan Gacutan from UNSW Science’s Centre for Marine Science and Innovation.

“We can combine this rich data over space and time to get patterns of the marine debris and plastic problem across Australia.

“This study shows, with unprecedented resolution, the variation in debris items both regionally and across Australia.”

Gacutan and team found that almost half of the rubbish came from litter and dumping on land, with 7% from dumping at sea. Another 42% couldn’t be related to any definitive source because it had been broken down into small fragments, creating microplastics, which are mapped by another citizen-science project, AUSMAP.

The study appears in the journal Science of The Total Environment.

If you would like to contribute to the AMDI Database, read more here.

A map of australia showing plastic hotspots along coast, colour-coded
A map of the accumulated count [per day] of all debris averaged per clean-up site across the Australian coast. Coasts with insufficient sites were not considered in the analysis. Credit: Jordan Gacutan

Waste-water treatments flush microplastics into the sea

Another study led by the University of Canterbury has found that wastewater treatment plants are a significant source of microplastics in the marine environment.

As reported in the New Zealand Journal of Marine and Freshwater Research, the team sampled water from three treatment plants, finding that they are adding 240,000 microplastics into the coastal environment every single day.

“While microplastics are now considered to be ubiquitous in the environment, sources of microplastics and routes of entry to the environment are not fully understood,” the authors explain in their paper.

“Due to the extensive domestic and commercial use of plastic products, and the prevalence of synthetic clothing and textiles, residential and industrial wastewaters are considered to be potentially significant sources of microplastics.”

Waste-water plants are not designed to remove microplastics from effluent, although previous studies have found that they can be efficient at removing larger pieces.

The research found microplastics in every sample taken from the treatment plants.

The most common plastics detected were polyester (used in textile and synthetic clothes), polyethylene (used in plastic bags, films and bottles) and polypropylene (commonly used in food preparation and storage, such as baby feeding bottles and reusable containers).

“The persistent discharge of microplastics to the coastal environment through waste-water treatment plants is a significant contribution to ocean plastic pollution and concern for a range of aquatic organisms,” the team writes.

The researchers have called for further work to be done to better understand what types of microplastics are entering treatment plants, what is discharged, and where the plastics end up in the marine environment.

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