Modern Australian


after a storm, microplastic pollution surged in the Cooks River

  • Written by James Hitchcock, Post-Doctoral Research Fellow, University of Canberra

Each year the ocean is inundated with 4.8 to 12.7 million tonnes of plastic washed in from land. A big proportion of this plastic is between 0.001 to 5 millimetres, and called “microplastic”.

But what happens during a storm, when lashings of rain funnel even more water from urban land into waterways? To date, no one has studied just how important storm events may be in polluting waterways with microplastics.

Read more: Microplastic pollution is everywhere, but scientists are still learning how it harms wildlife

So to find out, I studied my local waterway in Sydney, the Cooks River estuary. I headed out daily to measure how many microplastics were in the water, before, during, and after a major storm event in October, 2018.

The results, published on Wednesday, were startling. Microplastic particles in the river had increased more than 40 fold from the storm.

after a storm, microplastic pollution surged in the Cooks River Particles of plastic found in rivers. They may be tiny, but they’re devastating to wildlife in waterways. Author provided

To inner west Sydneysiders, the Cooks River is known to be particularly polluted. But it’s largely similar to many urban catchments around the world.

If the relationship between storm events and microplastic I found in the Cooks River holds for other urban rivers, then the concentrations of microplastics we’re exposing aquatic animals to is far higher than previously thought.

14 million plastic particles

They may be tiny, but microplastics are a major concern for aquatic life and food webs. Animals such as small fish and zooplankton directly consume the particles, and ingesting microplastics has the potential to slow growth, interfere with reproduction, and cause death.

Determining exactly how much microplastic enters rivers during storms required the rather unglamorous task of standing in the rain to collect water samples, while watching streams of unwanted debris float by (highlights included a fire extinguisher, a two-piece suit, and a litany of tennis balls).

Back in the laboratory, a multi-stage process is used to separate microplastics. This includes floating, filtering, and using strong chemical solutions to dissolve non-plastic items, before identification and counting with specialised microscopes.

after a storm, microplastic pollution surged in the Cooks River Litter caught in a trap in Cooks River. These traps aren’t effective at catching microplastic. Author provided

In the days before the October 2018 storm, there were 0.4 particles of microplastic per litre of water in the Cooks River. That jumped to 17.4 microplastics per litre after the storm.

Overall, that number averages to a total of 13.8 million microplastic particles floating around in the Cooks River estuary in the days after the storm.

Read more: Seafloor currents sweep microplastics into deep-sea hotspots of ocean life

In other urban waterways around the world scientists have found similarly high numbers of microplastic.

For example in China’s Pearl River, microplastic averages 19.9 particles per litre. In the Mississippi River in the US, microplastic ranges from 28 to 60 particles per litre.

Where do microplastics come from?

We know runoff during storms is one of the main ways pollutants such as sediments and heavy metals end up in waterways. But not much is known about how microplastic gets there.

However think about your street. Wherever you see litter, there are also probably microplastics you cannot see that will eventually work their way into waterways when it rains.

Read more: Sustainable shopping: how to stop your bathers flooding the oceans with plastic

Many other sources of microplastics are less obvious. Car tyres, for example, which typically contain more plastic than rubber, are a major source of microplastics in our waterways. When your tyres lose tread over time, microscopic tyre fragments are left on roads.

after a storm, microplastic pollution surged in the Cooks River Did you know your car tyres can be a major source of microplastic pollution? Shutterstock

Microplastics may even build up on roads and rooftops from atmospheric deposition. Everyday, lightweight microplastics such as microfibres from synthetic clothing are carried in the wind, settling and accumulating before they’re washed into rivers and streams.

What’s more, during storms wastewater systems may overflow, contaminating waterways. Along with sewage, this can include high concentrations of synthetic microfibers from household washing machines.

And in regional areas, microplastics may be washing in from agricultural soils. Sewage sludge is often applied to soils as it is rich in nutrients, but the same sludge is also rich in microplastics.

What can be done?

There are many ways to mitigate the negative effects of stormwater on waterways.

Screens, traps, and booms can be fitted to outlets and rivers and catch large pieces of litter such as bottles and packaging. But how useful these approaches are for microplastics is unknown.

Raingardens and retention ponds are used to catch and slow stormwater down, allowing pollutants to drop to bottom rather than being transported into rivers. Artificial wetlands work in similar ways, diverting stormwater to allow natural processes to remove toxins from the water.

after a storm, microplastic pollution surged in the Cooks River Almost 14 million plastic particles were floating in Cooks River after a storm two years ago. Shutterstock

But while mitigating the effects of stormwater carrying microplastics is important, the only way we’ll truly stop this pollution is to reduce our reliance on plastic. We must develop policies to reduce and regulate how much plastic material is produced and sold.

Plastic is ubiquitous, and its production around the world hasn’t slowed, reaching 359 million tonnes each year. Many countries now have or plan to introduce laws regulating the sale or production of some items such as plastic bags, single-use plastics and microbeads in cleaning products.

Read more: We have no idea how much microplastic is in Australia's soil (but it could be a lot)

In Australia, most state governments have committed to banning plastic bags, but there are still no laws banning the use of microplastics in cleaning or cosmetic products, or single-use plastics.

We’ve made a good start, but we’ll need deeper changes to what we produce and consume to stem the tide of microplastics in our waterways.

Authors: James Hitchcock, Post-Doctoral Research Fellow, University of Canberra

Read more https://theconversation.com/a-fire-extinguisher-a-suit-and-14-million-plastic-particles-after-a-storm-microplastic-pollution-surged-in-the-cooks-river-139043

NEWS

The world endured 2 extra heatwave days per decade since 1950 – but the worst is yet to come

ShutterstockThe term “heatwave” is no stranger to Australians. Defined as when conditions are excessively hot for at least three days in a row, these extreme temperature events have always punctuated...

Michelle Grattan on Melbourne cluster outbreaks, Australia's defence spending, and the Eden-Monaro byelection

University of Canberra Vice-Chancellor and President Professor Paddy Nixon and Professorial Fellow Michelle Grattan discuss the week in politics including the Eden-Monaro byelection, Scott Morrison’s 2020 Defence Strategic Update, and...

The US has bought most of the world's remdesivir. Here's what it means for the rest of us

Dimitri Karastelev/Unsplash, CC BYTo beat the coronavirus pandemic, countries need to collaborate. We need the best possible science to develop vaccines and drugs, and to test, track and contain the...

Why some people don't want to take a COVID-19 test

Last week, outgoing chief medical officer Brendan Murphy announced all returned travellers would be tested for COVID-19 before and after quarantine.Some were surprised testing was not already required. Others were...

Giant sea scorpions were the underwater titans of prehistoric Australia

Dimitris Siskopoulos/Wiki commonc, CC BY-SALet’s turn back the hands of time. Before extinction knocked dinosaurs off their pillar, before the “Great Dying” extinction wiped out 95% of all organisms –...

stay silent, or flee the city. The world must give them a path to safety

Sipa USA Willie Siau / SOPA Images/Sipa UIn recent days, the prime ministers of the UK and Australia each declared they are working toward providing safe haven visas for Hong...

Victoria's coronavirus contact tracers are already under the pump. What happens next?

ShutterstockThe emergence of significant community transmission of COVID-19 in Melbourne over the past week is greatly concerning to the whole of Australia.Earlier this week, Victoria’s chief health officer Brett Sutton...

China's push into PNG has been surprisingly slow and ineffective. Why has Beijing found the going so tough?

Peter Parks/Pool/EPAChinese activity in Papua New Guinea was not the only factor behind Australia’s Pacific “Step-Up”. As a former high commissioner to PNG, I know it followed serious deliberations about...

Why Bernard Collaery's case is one of the gravest threats to freedom of expression

Lukas Coch/AAPAfter a lengthy delay due to the coronavirus pandemic, the legal case that constitutes the most significant threat to freedom of expression in this country will soon play out...

what's the new coronavirus saliva test, and how does it work?

A cornerstone of containing the COVID-19 pandemic is widespread testing to identify cases and prevent new outbreaks emerging. This strategy is known as “test, trace and isolate”.The standard test so...

need a sitter? Revisiting girlhood, feminism and diversity in The Baby-Sitters Club

Kailey Schwerman/NetflixThe Baby-Sitters Club, the popular series by Ann M. Martin, defined my childhood. I collected the books until I was 11. I played it in the school yard (I...

Defunding arts degrees is the latest battle in a 40-year culture war

The government’s recently proposed restructure of university fees would see students pay 113% more for many humanities subjects.The package is not a case of “humanities vs STEM (science, technology, engineering...

Popular articles from Modern Australian

How to find affordable steel blue work boots in Australia for safety6 Ways To Get Quality Sleep When It’s HotThe Dangers of Uncontrolled High Blood Pressure7 Tips for Renovating a Heritage Home8 Bathroom Renovation Tips for the ElderlyWhy Flying Kites Is Considered A Fun Activity In PerthHow TV Shows Affect the Online Casino Industry in AustraliaCould Rose Byrne Become One of the Best Australian Actresses of All Time?The Latest Trends In Bathroom DesigniPhone Repairs Brisbane – How To Find a Trustworthy Repair ProviderProzac for Dogs: An Effective PsychotropicBehavioural Sleep Problems in School-Aged ChildrenBest Reasons to Use Amino Acid SupplementsUnderwater Paradise: Best Islands for SnorkelingHow To Choose The Right Table Saw for Your Workshop