We analysed data from 29,798 clean-ups around the world to uncover some of the worst litter hotspots


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Lauren Roman, CSIRO; Britta Denise Hardesty, CSIRO, and Chris Wilcox, CSIROCoastal litter is a big environmental problem. But how does this litter differ around the world, and why? In the first global analysis of its kind, we set out to answer those questions using data collected by thousands of citizen scientists.

Our analysis, released today, discovered litter hotspots on every inhabited continent, including Australia. This finding busts two persistent myths: that most of the world’s plastic pollution comes from just a few major rivers, and that countries in the Global South are largely to blame for the marine plastic problem.

Single-use plastics formed the majority of litter in this study. And in general, litter hotspots were associated with socioeconomic factors such as a concentration of built infrastructure, less national wealth, and a high level of lighting at night.

Our insights reveal the complex patterns driving coastal pollution, and suggest there is no “one size fits all” solution to cleaning up the world’s oceans. In fact, the best solution is to stop the waste problem long before it reaches the sea.

This study analyses the data collected by hundreds of thousands of citizen scientists conducting clean-ups worldwide.
Copyright PADI AWARE

A complex picture

We are scientists from the CSIRO’s Marine Debris Research team. Our study involved working closely with Ocean Conservancy and the PADI AWARE Foundation, which together hold the world’s most comprehensive litter data sets gathered by citizen scientists.

We analysed hundreds of thousands of items from 22,508 clean-ups on land (at beaches and the edge of rivers and lakes) as well as 7,290 seafloor clean-ups. The clean-ups spanned 116 and 118 countries, respectively, and involved participants recording counts for each item collected.

The analysis showed a huge diversity in the location and scale of plastic pollution hotspots. They were not limited to single countries or rivers – instead, the hotspots occurred in all inhabited continents and across many countries. In many places, litter patterns between neighbouring locations were vastly different.




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Most litter comprised single-use items: cigarette butts, fishing line, food wrappers, and plastic bottles and bags.

In general, places with more overall litter tended to have:

  • more built infrastructure
  • less national wealth
  • bright lighting at night (which indicated urban density).

Cities and other dense urban areas around the world were linked with hotspots of “convenience” single-use plastic items, such as plastic bags, food wrappers, drink bottles, take-away containers, straws, plastic cutlery and lids. These hotspots are represented in the infographic below.



However, not all litter items followed this pattern. For example, cigarette butts followed a regional pattern and were more common in Southern Europe and North Africa.

Fishing line was most abundant in wealthier countries where recreational fishing is a popular pastime. Hotspots included Australia, the United Kingdom and the United States.

Clusters of hotspots were often associated with partially enclosed bays, seas and lakes. These included areas such as the Mediterranean Sea, the Bay of Bengal, the South China and Philippine seas, the Gulf of Mexico, the Caribbean Sea, Lake Malawi and the Great Lakes of North America.

Plastic accumulation in these areas is likely due to factors such as high local littering combined with relatively contained bodies of water.

Plastic bottle hotspots were more common in tropical countries such as Costa Rica and Jamaica, among others. Plastic food wrappers were abundant in the island nations of Southeast Asia, particularly around Indonesia and the Philippines.




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fishing line and bobber wrapped around twig in water
Australia contained several global hotspots for fishing line waste.
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Cleaning up our coasts

Ultimately, our study reveals the diversity and complexity of the plastic pollution issue. We hope it helps governments make waste policy decisions based on sound scientific evidence.

The findings suggest programs to tackle ocean litter should be rolled out at the grassroots level, or within one part of a country, as well as nationally.

In Australia, for example, Zoos Victoria’s Seal The Loop program aims to tackle localised fishing line waste at locations where the pastime is common. The program includes fishing line bins placed on piers and at boat ramps to encourage responsible waste disposal.

And in Malawi and 15 other countries in southern Africa, national bans on plastic bags target this locally problematic item.

Our analysis shows much non-degradable waste found in the environment comes from pre-packaged food and beverages. So regulations specifically addressing this type of packaging can be useful.

In Australia, for example, Hobart is aiming to become the first Australian city to ban single-use plastic takeaway food packaging, as part of an ambitious goal of zero-waste to landfill by 2030.

Other strategies known to change litter behaviour include recycling incentives such as container deposit schemes, particularly in lower socioeconomic areas where littering is highest, as well as education campaigns. And levies on plastic items could also help stop litter entering the environment.

This Saturday September 18, Ocean Conservancy is holding its annual International Coastal Cleanup – come along if you can and if COVID restrictions allow. You’ll be helping your local environment and collecting data to inform tomorrow’s waste management policies.

Land-based clean-ups were conducted across 116 countries. Please join us for the next one.
Rafeed Hussain Ocean Conservancy

The authors would like to acknowledge the tireless volunteers from the International Coastal Cleanup and Dive Against Debris, and collaborators; Ocean Conservancy’s Dr George H. Leonard and Nicholas Mallos, and PADI AWARE Foundation’s Hannah Pragnell-Raasch and Ian Campbell.The Conversation

Lauren Roman, Postdoctoral Researcher, Oceans and Atmosphere, CSIRO; Britta Denise Hardesty, Senior Principal Research Scientist, Oceans and Atmosphere, CSIRO, and Chris Wilcox, Senior Principal Research Scientist, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A tale of two valleys: Latrobe and Hunter regions both have coal stations, but one has far worse mercury pollution


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Larissa Schneider, Australian National University; Anna Lintern, Monash University; Cameron Holley, UNSW; Darren Sinclair, University of Canberra; Neil Rose, UCL; Ruoyu Sun, and Simon Haberle, Australian National UniversityWe know coal-fired power stations can generate high levels of carbon dioxide, but did you know they can be a major source of mercury emissions as well?

Our new research compared the level of mercury pollution in the Hunter Valley in New South Wales and the Latrobe Valley in Victoria.

And we found power stations in the Latrobe Valley emit around 10 times more mercury than power stations in the Hunter Valley. Indeed, the mercury level in the Latrobe Valley environment is 14 times higher than what’s typically natural for the region.

So why is there such a stark difference between states? Well, it has a lot to do with regulations.

Following a NSW requirement for power stations to install pollution control technology, mercury levels in the environment dropped. In Victoria, on the other hand, coal-fired power stations continue to operate without some of the air pollution controls NSW and other developed countries have mandated.

To minimise the safety risks that come with excessive mercury pollution, coal-fired power stations in all Australian jurisdictions should adopt the best available technologies to reduce mercury emissions.

A dangerous neurotoxin

Mercury is a neurotoxin, which means it can damage the nervous system, brain and other organs when a person or animal is exposed to unsafe levels.

Coal naturally contains mercury. So when power stations burn coal, mercury is released to the atmosphere and is then deposited back onto the Earth’s surface. When a high level of mercury ends up in bodies of water, such as lakes and rivers, it can be transferred to fish and other aquatic organisms, exposing people and larger animals to mercury that feed on these fish.




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Mercury does not readily degrade or leave aquatic environments such as lakes and rivers. It’s a persistent toxic element — once present in water, it’s there to stay.

The amount of mercury emitted depends on the type of coal burnt (black or brown) and the type of pollution control devices the power stations use.

The Latrobe Valley stations in Victoria burn brown coal, which has more mercury than the black coal typically found in NSW. Despite this, Victorian regulations have historically not placed specific limits on mercury emissions.

In contrast, NSW power plants are required to use “bag filters”, a technology that’s used to trap mercury (and other) particles before they enter the atmosphere.

While bag filters alone fall short of the world’s best practices, they can still be effective. In fact, after bag filters were retrofitted to Hunter Valley’s Liddell power station in the early 1990s, mercury deposition in the surrounding environment halved.

Mercury deposited in sediments of Lake Glenbawn (left) in the Hunter Valley and Traralgon Railway Reservoir (right) in the Latrobe Valley.

The best available technology to control mercury emissions from coal-fired power plants is a combination of “wet flue-gas desulfurization” (which removes mercury in its gaseous form) and bag filters (which removes mercury bound to particles).

This is what’s been adopted across North America and parts of Europe. It not only filters out mercury, but also removes sulphur dioxide, nitrogen oxides and other toxic air compounds.

Using lake sediments to see into the past

Lake sediments can capture mercury deposited from the atmosphere and from surrounding areas. Sediments that contain this mercury accumulate at the bottom of lakes over time — the deeper the sediment, the further back in time we can analyse.

We took sediment samples from lakes in the Latrobe and Hunter valleys, and dated them back to 1940 to get a historical record of mercury deposition.

This information can help us understand how much naturally occurring mercury there was before coal-fired power stations were built, and therefore show us the impact of burning coal.

A power station by a lake
Lake Narracan: one of the lakes we sampled sediments from, near a coal-fired power station in Latrobe Valley.
Larissa Schneider, Author provided

From these records, we found the adoption of bag filters in the Hunter Valley corresponded with mercury depositions declining in NSW from the 1990s.

In contrast, in Victoria, where there’s been no such requirement, mercury emissions and depositions have continued to increase since Hazelwood power station was completed in 1971.

What do we do about it?

In March, the Victorian government announced changes to the regulatory licence conditions for brown coal-fired power stations. Although mercury emissions allowances have been included for the first time, they’re arguably still too high, and there’s no requirement to install specific pollution control technologies.

There’s a risk this approach won’t reduce mercury emissions from existing levels. Victoria should instead consider more ambitious regulations that encourage the adoption of best practice technology to help protect local communities and the environment.

Coal-fired power station at the end of a road, at night
Loy Yang power station, Victoria’s largest, burns brown coal which contains more mercury.
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Another vital step toward protecting human health and the environment from mercury is for the federal government to ratify the Minamata Convention on Mercury, an international treaty to protect human health and the environment from mercury.

Despite signing the convention in 2013, the Australian government is yet to ratify it, which is required to make it legally binding in Australia.

Ratifying the convention will oblige state and federal governments to develop and implement a strategy to reduce mercury emissions, including from coal-fired power stations across Australia. And this strategy should include rolling out effective technologies — our research shows it can make a big difference.


The authors acknowledge Lauri Myllyvirta from the Centre for Research on Energy and Clean Air for her contributions to this article.




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Hazelwood power station: from modernist icon to greenhouse pariah


The Conversation


Larissa Schneider, DECRA fellow, Australian National University; Anna Lintern, Lecturer, Monash University; Cameron Holley, Professor, UNSW; Darren Sinclair, Professor, University of Canberra; Neil Rose, Professor of Environmental Pollution and Palaeolimnology, UCL; Ruoyu Sun, Associate Professor, and Simon Haberle, Professor, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The story of Rum Jungle: a Cold War-era uranium mine that’s spewed acid into the environment for decades


Gavin Mudd, Author provided

Gavin Mudd, RMIT UniversityBuried in last week’s budget was money for rehabilitating the Rum Jungle uranium mine near Darwin. The exact sum was not disclosed.

Rum Jungle used to be a household name. It was Australia’s first large-scale uranium mine and supplied the US and British nuclear weapons programs during the Cold War.

Today, the mine is better known for extensively polluting the Finniss River after it closed in 1971. Despite a major rehabilitation project by the Commonwealth in the 1980s, the damage to the local environment is ongoing.

I first visited Rum Jungle in 2004, and it was a colourful mess, to say the least. Over later years, I saw it worsen. Instead of a river bed, there were salt crusts containing heavy metals and radioactive material. Pools of water were rich reds and aqua greens — hallmarks of water pollution. Healthy aquatic species were nowhere to be found, like an ecological desert.

The government’s second rehabilitation attempt is significant, as it recognises mine rehabilitation isn’t always successful, even if it appears so at first.

Rum Jungle serves as a warning: rehabilitation shouldn’t be an afterthought, but carefully planned, invested in and monitored for many, many years. Otherwise, as we’ve seen, it’ll be left up to future taxpayers to fix.

The quick and dirty history

Rum Jungle produced uranium from 1954 to 1971, roughly one-third of which was exported for nuclear weapons. The rest was stockpiled, and then eventually sold in 1994 to the US.

A sign for Rum Jungle rehabilitation on a fence
Rehabilitation of Rum Jungle began in the 1980s.
Mick Stanic/Flickr, CC BY-NC-SA

The mine was owned by the federal government, but was operated under contract by a former subsidiary of Rio Tinto. Back then, there were no meaningful environmental regulations in place for mining, especially for a military project.

The waste rock and tailings (processed ore) at Rum Jungle contains significant amounts of iron sulfide, called “pyrite”. When mining exposes the pyrite to water and oxygen, a chemical reaction occurs generating so-called “acidic mine drainage”. This drainage is rich in acid, salts, heavy metals and radioactive material (radionuclides), such as copper, zinc and uranium.

Acid drainage seeping from waste rock, plus acidic liquid waste from the process plant, caused fish and macroinvertebrates (bugs, worms, crustaceans) to die out, and riverbank vegetation to decline. By the time the mine closed in 1971, the region was a well-known ecological wasteland.

Once an ecosystem, now a wasteland.
Gavin Mudd, Author provided

When mines close, the modern approach is to rehabilitate them to an acceptable condition, with the aim of minimal ongoing environmental damage. But after working in environmental engineering across Australia for 26 years, I’ve seen few mines completely rehabilitated — let alone successfully.

Many Australian mines have major problems with acid mine drainage. This includes legacy mines from historical, unregulated times (Mount Morgan, Captains Flat, Mount Lyell) and modern mines built under stricter environmental requirements (Mount Todd, Redbank, McArthur River).

This is why Rum Jungle is so important: it was one of the very few mines once thought to have been rehabilitated successfully.

Salts litter the bed of the Finniss River.
Gavin Mudd, Author provided

So what went wrong?

From 1983 to 1986, the government spent some A$18.6 million (about $55.5 million in 2020 value) to reduce acid drainage and restore the Finniss River ecology. Specially engineered soil covers were placed over the waste rock to reduce water and oxygen getting into the pyrite.

The engineering project was widely promoted as successful through conferences and academic studies, with water quality monitoring showing that the metals polluting the Finniss had substantially subsided. But this lasted only for a decade.




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By the late 1990s, it became clear the engineered soil covers weren’t working effectively anymore.

First, the design was insufficient to reduce infiltration of water during the wet season (thicker covers should have been used). Second, the covers weren’t built to design in parts (they were thinner and with the wrong type of soils).

The first reason is understandable, we’d never done this before. But the second is not acceptable, as the thinner covers and wrong soils made it easier for water and oxygen to get into the waste rock and generate more polluting acid mine drainage.

The iron-tainted red hues of the Finniss River near the waste rock dumps leaking acid mine drainage.
Gavin Mudd, Author provided
The copper-tainted green hues of the Finniss River near the waste rock dumps leaking acid mine drainage.
Gavin Mudd, Author provided

The stakes are higher

There are literally thousands of recent and still-operating mines around Australia, where acid mine drainage remains a minor or extreme risk. Other, now closed, acid drainage sites have taken decades to bring under control, such as Brukunga in South Australia, Captain’s Flat in NSW, and Agricola in Queensland.

We got it wrong with Rum Jungle, which generated less than 20 million tonnes of mine waste. Modern mines, such as Mount Whaleback in the Pilbara, now involve billions of tonnes — and we have dozens of them. Getting even a small part of modern mine rehabilitation wrong could, at worst, mean billions of tonnes of mine waste polluting for centuries.

So what’s the alternative? Let’s take the former Woodcutters lead-zinc mine, which operated from 1985 to 1999, as an example.

Given its acid drainage risks, the mine’s rehabilitation involved placing reactive waste into the open pit, rather than using soil covers. “Backfilling” such wastes into pits makes good sense, as the pyrite is deeper and not exposed to oxygen, substantially reducing acid drainage risks.

Backfilling isn’t commonly used because it’s widely perceived in the industry as expensive. Clearly, we need to better assess rehabilitation costs and benefits to justify long-term options, steering clear of short-term, lowest-cost approaches.

The Woodcutters experience shows such thinking can be done to improve the chances for successfully restoring the environment.

Getting it right

The federal government funded major environmental studies of the Rum Jungle mine from 2009, including an environmental impact statement in 2020, before the commitment in this year’s federal budget.




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The plan this time includes backfilling waste rock into the open pits, and engineering much more sophisticated soil covers. It will need to be monitored for decades.

And the cost of it? Well, that was kept confidential in the budget due to sensitive commercial negotiations.

But based on my experiences, I reckon they’d be lucky to get any change from half a billion dollars. Let’s hope we get it right this time.The Conversation

Gavin Mudd, Associate Professor of Environmental Engineering, RMIT University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Think all your plastic is being recycled? New research shows it can end up in the ocean


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Monique Retamal, University of Technology Sydney; Elsa Dominish, University of Technology Sydney; Nick Florin, University of Technology Sydney, and Rachael Wakefield-Rann, University of Technology Sydney

We all know it’s wrong to toss your rubbish into the ocean or another natural place. But it might surprise you to learn some plastic waste ends up in the environment, even when we thought it was being recycled.

Our study, published today, investigated how the global plastic waste trade contributes to marine pollution.

We found plastic waste most commonly leaks into the environment at the country to which it’s shipped. Plastics which are of low value to recyclers, such as lids and polystyrene foam containers, are most likely to end up polluting the environment.

The export of unsorted plastic waste from Australia is being phased out – and this will help address the problem. But there’s a long way to go before our plastic is recycled in a way that does not harm nature.

Man puts items in bins
Research shows plastic meant for recycling often ends up elsewhere.
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Know your plastics

Plastic waste collected for recycling is often sold for reprocessing in Asia. There, the plastics are sorted, washed, chopped, melted and turned into flakes or pellets. These can be sold to manufacturers to create new products.

The global recycled plastics market is dominated by two major plastic types:

  • polyethylene terephthalate (PET), which in 2017 comprised 55% of the recyclable plastics market. It’s used in beverage bottles and takeaway food containers and features a “1” on the packaging

  • high-density polyethylene (HDPE), which comprises about 33% of the recyclable plastics market. HDPE is used to create pipes and packaging such as milk and shampoo bottles, and is identified by a “2”.

The next two most commonly traded types of plastics, each with 4% of the market, are:

  • polypropylene or “5”, used in containers for yoghurt and spreads

  • low-density polyethylene known as “4”, used in clear plastic films on packaging.

The remaining plastic types comprise polyvinyl chloride (3), polystyrene (6), other mixed plastics (7), unmarked plastics and “composites”. Composite plastic packaging is made from several materials not easily separated, such as long-life milk containers with layers of foil, plastic and paper.

This final group of plastics is not generally sought after as a raw material in manufacturing, so has little value to recyclers.




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Symbols on PET plastic item
Items made from PET plastic resin are marked with a ‘1’.
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Shifting plastic tides

China banned the import of plastic waste in January 2018 to prevent the receipt of low-value plastics and to stimulate the domestic recycling industry.

Following the bans, the global plastic waste trade shifted towards Southeast Asian nations such as Vietnam, Thailand, Malaysia, and Indonesia. The largest exporters of waste plastics in 2019 were Europe, Japan and the US. Australia exported plastics primarily to Malaysia and Indonesia.

Australia’s waste export ban recently became law. From July this year, only plastics sorted into single resin types can be exported; mixed plastic bales cannot. From July next year, plastics must be sorted, cleaned and turned into flakes or pellets to be exported.

This may help address the problem of recyclables becoming marine pollution. But it will require a significant expansion of Australian plastic reprocessing capacity.

Map showing the import and export map of plastic waste globally.
Map showing the import and export map of plastic waste globally.
Authors provided

What we found

Our study was funded by the federal Department of Agriculture, Water and the Environment. It involved interviews with trade experts, consultants, academics, NGOs and recyclers (in Australia, India, Indonesia, Japan, Malaysia, Vietnam and Thailand) and an extensive review of existing research.

We found when it comes to the international plastic trade, plastics most often leak into the environment at the destination country, rather than at the country of origin or in transit. Low-value or “residual” plastics – those left over after more valuable plastic is recovered for recycling – are most likely to end up as pollution. So how does this happen?

In Southeast Asia, often only registered recyclers are allowed to import plastic waste. But due to high volumes, registered recyclers typically on-sell plastic bales to informal processors.

Interviewees said when plastic types were considered low value, informal processors frequently dumped them at uncontrolled landfills or into waterways. Sometimes the waste is burned.

Plastics stockpiled outdoors can be blown into the environment, including the ocean. Burning the plastic releases toxic smoke, causing harm to human health and the environment.

Interviewees also said when informal processing facilities wash plastics, small pieces end up in wastewater, which is discharged directly into waterways, and ultimately, the ocean.

However, interviewees from Southeast Asia said their own domestic waste management was a greater source of ocean pollution.

Birds fly over landfill site
Plastic waste meant for recycling can end up in overseas landfill, before it blows into the ocean.
Anupam Nath/AP

A market failure

The price of many recycled plastics has crashed in recent years due to oversupply, import restrictions and falling oil prices, (amplified by the COVID-19 pandemic). However clean bales of PET and HDPE are still in demand.

In Australia, material recovery facilities currently sort PET and HDPE into separate bales. But small contaminants of other materials (such as caps and plastic labels) remain, making it harder to recycle into high quality new products.

Before the price of many recycled plastics dropped, Australia baled and traded all other resin types together as “mixed plastics”. But the price for mixed plastics has fallen to zero and they’re now largely stockpiled or landfilled in Australia.

Several Australian facilities are, however, investing in technology to sort polypropylene so it can be recovered for recycling.

Shampoo bottles in supermarket
High-density polyethylene items such as shampoo bottles comprise a large share of the plastic waste market.
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Doing plastics differently

Exporting countries can help reduce the flow of plastics to the ocean by better managing trade practices. This might include:

  • improving collection and sorting in export countries

  • checking destination processing and monitoring

  • checking plastic shipments at export and import

  • improving accountability for shipments.

But this won’t be enough. The complexities involved in the global recycling trade mean we must rethink packaging design. That means using fewer low-value plastic and composites, or better yet, replacing single-use plastic packaging with reusable options.


The authors would like to acknowledge research contributions from Asia Pacific Waste Consultants (APWC) – Dr Amardeep Wander, Jack Whelan and Anne Prince, as well as Phil Manners at CIE.




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The Conversation


Monique Retamal, Research Principal, Institute for Sustainable Futures, University of Technology Sydney; Elsa Dominish, Senior Research Consultant, Institute for Sustainable Futures, University of Technology Sydney; Nick Florin, Research Director, Institute for Sustainable Futures, University of Technology Sydney, and Rachael Wakefield-Rann, Research Consultant, Institute for Sustainable Futures, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We tested tiger snake scales to measure wetland pollution in Perth. The news is worse than expected


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Damian Lettoof, Curtin University; Kai Rankenburg, Curtin University; Monique Gagnon, Curtin University, and Noreen Evans, Curtin University

Australia’s wetlands are home to a huge range of stunning flora and fauna, with large snakes often at the top of the food chain.

Many wetlands are located near urban areas. This makes them particularly susceptible to contamination as stormwater, urban drainage and groundwater can wash metals — such as arsenic, cadmium, lead and mercury — into the delicate ecosystem.

We know many metals can travel up the food chain when they’re present in the environment. So to assess contamination levels, we caught highly venomous tiger snakes across wetlands in Perth, and repurposed laser technology to measure the metals they accumulated.

In our new paper, we show metal contamination in wild wetland tiger snakes is chronic, and highest in human-disturbed wetlands. This suggests all other plants and animals in these wetlands are likely contaminated as well.

34 times more arsenic in wild wetland snakes than captive snakes

Urban growth and landscape modification often introduces metals into the surrounding environment, such as mining, landfill and waste dumps, vehicles and roadworks, and agriculture.

When they reach wetlands, sediments collect and store these metals for hundreds of years. And if a wetland’s natural water levels are lowered, from agricultural draining for example, sediments can become exposed and erode. This releases the metals they’ve been storing into the ecosystem.

A reflective lake, with green vegetation surrounding it
The wetland in Yanchep National Park, Perth, was supposed to be our ‘clean’ comparison site. Its levels of metal contamination was unprecedented.
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This is what we suspect happened in Yanchep National Park’s wetland, which was supposed to be our “clean” comparison site to more urban wetlands. But in a 2020 study looking at sediment contamination, we found this wetland had higher levels of selenium, mercury, chromium and cadmium compared to urban wetlands we tested.

And at Herdsman Lake, our most urban wetland five minutes from the Perth city centre, we found concentrations of arsenic, lead, copper and zinc in sediment up to four times higher than government guidelines.




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In our new study on tiger snake scales, we compared the metal concentrations in wild wetland tiger snakes to the concentrations that naturally occurs in captive-bred tiger snakes, and to the sediment in the previous study.

We found arsenic was 20-34 times higher in wild snakes from Herdsman Lake and Yanchep National Park’s wetland. And snakes from Herdsman Lake had, on average, eight times the amount of uranium in their scales compared to their captive-bred counterparts.

Tiger snake on the ground, near rubbish.
Our research confirmed snake scales are a good indicator of environmental contamination.
Damian Lettoof, Author provided

Tiger snakes usually prey on frogs, so our results suggest frogs at these lakes are equally as contaminated.

We know for many organisms, exposure to a high concentration of metals is fatally toxic. And when contamination is chronic, it can be “neurotoxic”. This can, for example, change an organism’s behaviour so they eat less, or don’t want to breed. It can also interfere with their normal cellular function, compromising immune systems, DNA repair or reproductive processes, to name a few.

Snakes in general appear relatively resistant to the toxic effects of metal contamination, but we’re currently investigating what these levels of contamination are doing to tiger snakes’ health and well-being.

Our method keeps snakes alive

Snakes can be a great indicator of environmental contamination because they generally live for a long time (over 10 years) and don’t travel too far from home. So by measuring metals in older snakes, we can assess the contamination history of the area they were collected from.

Typically, scientists use liver tissue to measure biological contamination since it acts like a filter and retains a substantial amount of the contaminants an animal is exposed to.

But a big problem with testing the liver is the animal usually has to be sacrificed. This is often not possible when studying threatened species, monitoring populations or working with top predators.

Two black swans in a lake, near cut grass
Sediment in Herdsman Lake had four times higher heavy metal levels than what government guidelines allow.
Shutterstock

In more recent years, studies have taken to measuring metals in external “keratin” tissues instead, which include bird feathers, mammal hair and nails, and reptile scales. As it grows, keratin can accumulate metals from inside the body, and scientists can measure this without needing to kill the animal.

Our research used “laser ablation” analysis, which involves firing a focused laser beam at a solid sample to create a small crater or trench. Material is excavated from the crater and sent to a mass spectrometer (analytical machine) where all the elements are measured.

This technology was originally designed for geologists to analyse rocks, but we’re among the first researchers applying it to snake scales.

Laser ablation atomises the keratin of snake scales, and allowed us to accurately measure 19 contaminants from each tiger snake caught over three years around different wetlands.

Wild tiger snake
Snakes generally appear resistant to the toxic effects of heavy metals.
Kristian Bell/Shutterstock

We need to minimise pollution

Our research has confirmed snake scales are a good indicator of environmental contamination, but this is only the first step.

Further research could allow us to better use laser ablation as a cost-effective technology to measure a larger suite of metals in different parts of the ecosystem, such as in different animals at varying levels in the food chain.

This could map how metals move throughout the ecosystem and help determine whether the health of snakes (and other top predators) is actually at risk by these metal levels, or if they just passively record the metal concentrations in their environment.




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It’s difficult to prevent contaminants from washing into urban wetlands, but there are a number of things that can help minimise pollution.

This includes industries developing strict spill management requirements, and local and state governments deploying storm-water filters to catch urban waste. Likewise, thick vegetation buffer zones around the wetlands can filter incoming water.The Conversation

Damian Lettoof, PhD Candidate, Curtin University; Kai Rankenburg, Researcher, Curtin University; Monique Gagnon, Researcher, Curtin University, and Noreen Evans, Professor, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.