Tons of plastic waste enters the Great Lakes every year. So where does it end up?

The Chicago shore of Lake Michigan. Image: J. Crocker/Wikimedia Commons.

Awareness is rising worldwide about the scourge of ocean plastic pollution, from Earth Day 2018 events to the cover of National Geographic magazine. But few people realise that similar concentrations of plastic pollution are accumulating in lakes and rivers. One recent study found microplastic particles – fragments measuring less then five millimeters – in globally sourced tap water and beer brewed with water from the Great Lakes.

According to recent estimates, over 8m tons of plastic enter the oceans every year. Using that study’s calculations of how much plastic pollution per person enters the water in coastal regions, one of us (Matthew Hoffman) has estimated that around 10,000 tons of plastic enter the Great Lakes annually. Now we are analysing where it accumulates and how it may affect aquatic life.

No garbage patches, but lots of scrap on beaches

Plastic enters the Great Lakes in many ways. People on the shore and on boats throw litter in the water. Microplastic pollution also comes from wastewater treatment plants, stormwater and agricultural runoff. Some plastic fibres become airborne – possibly from clothing or building materials weathering outdoors – and are probably deposited into the lakes directly from the air.

Sampling natural water bodies for plastic particles is time-consuming and can be done on only a small fraction of any given river or lake. To augment actual sampling, researchers can use computational models to map how plastic pollution will move once it enters the water. In the ocean, these models show how plastic accumulates in particular locations around the globe, including the Arctic.

When plastic pollution was initially found in the Great Lakes, many observers feared that it could accumulate in large floating garbage patches, like those created by ocean currents. However, when we used our computational models to predict how plastic pollution would move around in the surface waters of Lake Erie, we found that temporary accumulation regions formed but did not persist as they do in the ocean. In Lake Erie and the other Great Lakes, strong winds break up the accumulation regions.

Three-dimensional transport simulations of particle movement in Lake Erie, based on water current models developed by the National Oceanic & Atmospheric Administration.

Subsequent simulations have also found no evidence for a Great Lakes garbage patch. Initially this seems like good news. But we know that a lot of plastic is entering the lakes. If it is not accumulating at their centers, where is it?

Using our models, we created maps that predict the average surface distribution of Great Lakes plastic pollution. They show that most of it ends up closer to shore. This helps to explain why so much plastic is found on Great Lakes beaches: in 2017 alone, volunteers with the Alliance for the Great Lakes collected more than 16 tons of plastic at beach cleanups. If more plastic is ending up near shore, where more wildlife is located and where we obtain our drinking water, is that really a better outcome than a garbage patch?

Average density of simulated particles in the Great Lakes from 2009-14. Notice that there are no patches in the middle of the Lakes, but more of the particles are concentrated near the shores. Image: Matthew Hoffman/creative commons.

Searching for missing plastic

We estimate that over four tons of microplastic are floating in Lake Erie. This figure is only a small fraction of the approximately 2,500 tons of plastic that we estimate enter the Lake each year. Similarly, researchers have found that their estimates of how much plastic is floating at the ocean’s surface account for only around 1 per cent of estimated input. Plastic pollution has adverse effects on many organisms, and to predict which ecosystems and organisms are most affected, it is essential to understand where it is going.

We have begun using more advanced computer models to map the three-dimensional distribution of plastic pollution in the Great Lakes. Assuming that plastic simply moves with currents, we see that a large proportion of it is predicted to sink to lake bottoms. Mapping plastic pollution this way begins to shed light on exposure risks for different species, based on where in the lake they live.

According to our initial simulations, much of the plastic is expected to sink. This prediction is supported by sediment samples collected from the bottom of the Great Lakes, which can contain high concentrations of plastic.

Three-dimensional transport simulation in Lake Erie. Particle color represents depth below the water surface: the bluer the particle, the deeper it is.

In a real lake, plastic does not just move with the current. It also can float or sink, based on its size and density. As a particle floats and is “weathered” by sun and waves, breaks into smaller particles, and becomes colonised by bacteria and other microorganisms, its ability to sink will change.

Better understanding of the processes that affect plastic transport will enable us to generate more accurate models of how it moves through the water. In addition, we know little so far about how plastic is removed from the water as it lands on the bottom or the beach, or is ingested by organisms.


Prediction informs prevention

Developing a complete picture of how plastic pollution travels through waterways, and which habitats are most at risk, is crucial for conceiving and testing possible solutions. If we can accurately track different types of plastic pollution after they enter the water, we can focus on the types that end up in sensitive habitats and predict their ultimate fate. The Conversation

Of course, preventing plastic from entering our waterways in the first place is the best way to eliminate the problem. But by determining which plastics are more toxic and also more likely to come into contact with sensitive organisms, or end up in our water supply, we can target the “worst of the worst”.

With this information, government agencies and conservation groups can develop specific community education programmes, target cleanup efforts and work with industries to develop alternatives to products that contain these materials.

Matthew J. Hoffman, Associate Professor of Mathematical Sciences, Rochester Institute of Technology and Christy Tyler, Associate Professor of Environmental Science, Rochester Institute of Technology.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Jane Jacobs and Le Corbusier would agree on one thing: we need more social housing

Unite d’Habitation, Marseille. Image: Iantomferry/Wikimedia Commons.

Much has been written in CityMetric and beyond about the urban planning debates of the 1950s and ‘60s, that came to be characterised as a battle between master-planning and preservation. One side of the debate was personified by the father of modernist architecture, Le Corbusier, whilst the counter-argument was advanced by writer and journalist Jane Jacobs.

But when it comes to London’s housing crisis, aren’t there a few things that these two would actually agree on?

Jane Jacobs’ writing about the organic nature of self-organising communities, demonstrated, in her words, by the “intricate sidewalk ballet” of inner city neighbourhoods, should be required reading for anyone interested in how cities function. But today, Jacobs is increasingly invoked in attempts to oppose new developments of any kind. Her role in conceiving Manhattan’s West Village Houses, a low cost rented housing scheme built through New York State’s Mitchell-Lama Program, is unfortunately much less well known. It’s been suggested that if Jacobs were around today, she’d be working with New York’s housing activists. When her seminal work The Death and Life of Great American Cities was written, there were almost 2 million rent-controlled or rent-stabilised apartments in New York City; nowadays, there are fewer than half that number.

Le Corbusier, on the other hand, is too often blamed for drab high-rise blocks. But regardless of how well his followers across Europe interpreted his ideas, Le Corbusier’s vision for cities was about high quality residential blocks that also contained shops and leisure amenities and were surrounded by parkland – the original mixed use development if you like. His most famous building, Marseille’s Unite d’Habitation, consisted of 337 apartments with views of the mountains and the sea together with shops, a restaurant and a nursery school. The building was originally intended to be public housing, but the French government eventually sold off the flats to recoup costs. Alton West Estate in Roehampton and Park Hill in Sheffield are just some of the examples of Le Corbusier’s influence on the design of post-war council housing here in the UK.

Building homes for a serious business in post-war Britain. Under Attlee’s 1945 Labour Government, 700,000 new council homes were completed. In 1952, the largest architectural practice in the World was at London County Council, with 1,577 staff including 350 professional architects and trainees. These were the days of consensus, and very quickly Tory governments were actually competing with Labour governments about who could built the most council homes.

Some of the council homes built post-war have stood the test of time better than others. But what’s not in doubt is that building council homes on such a scale immeasurably changed the lives of so many families in desperate need of a decent, secure and affordable home. And so many of the post-war modernist high-rise blocks so despised by Jacobs quickly took on the organic self-organising traits that she held in such high regard and have become some of the most enduring and closely-knit communities in London.

Fast forward to 2019 and Right To Buy continues to decimate council housing stock, but perversely home ownership seems more out of reach than ever for so many. An entire generation is being forced to embrace long term private ting in a country that has some weakest protections for private tenants in Europe. Meanwhile, government spending on building new homes fell from £11.4bn in 2009 to just £5.3bn in 2015 – from 0.7 per cent to 0.2 per cent of GDP – and since then, the housing minister’s desk has been occupied by no fewer than six people.


So what would a comprehensive drive for new council and social housing on the scale of the 1945 government’s efforts look like in 2019?

Lubetkin, the architect responsible for Islington’s Spa Green Estate and Bevin Court, summed up the spirit of post-war council home building with his maxim that “nothing is too good for ordinary people”. It’s a vision that we’re trying to recreate through our own council home building programme in Islington.

One of the best opportunities for small council home building schemes is to expand upon existing communities. The vast majority of Islington’s new council housing takes the form of infill, construction on existing estates; in unloved spaces, in old garages, and in old undercrofts. These projects often involve landscaping and new amenities to enhance rather than reinvent local communities. We have built community centres and even rebuilt a library as part of council housing schemes. One Tenants’ and Residents’ Association had an idea for a new specialist over 55s block for the older residents of the estate who wanted to stay in their community.

But there’s a place for large-scale place making as well. When the Ministry of Justice closed Holloway Prison and announced that the site would be sold, Islington Council published a Supplementary Planning Document (SPD) on the site. We had one aim – to send a clear signal to the market that anyone who was looking at buying the site needed to be aware of their planning obligations. Most importantly, any development on the site needed to include at least 50 per cent genuinely affordable homes. The speculation around the site came to an end on 8 March this year when Peabody Housing Association announced that it had bought it. It has committed to going well above and beyond our planning requirements, by making 600 out of a total 1000 homes genuinely affordable homes, including 420 homes for social rent. We need to see more detail on what they are proposing but this is potentially brilliant for the borough. A local grassroots group, Community Plan for Holloway, have been instrumental in ensuring that the community’s voice is heard since the site was sold.

To recreate the scale of the massive post-war council home building programmes would require a Jane Jacobs inspired level of community activism combined with the architectural idealism of Le Corbusier. But it would also need the political will from central government to help local authorities get council housing built. And that, sadly, feels as far away as ever.

Diarmaid Ward is a Labour councillor and the executive member for housing & development at the London Borough of Islington.