̽��ֱ�� of Cambridge - Richard Harrison

Roadside hedges can reduce harmful ultrafine particle pollution around schools

cmm201 — Wed, 13 Sep 2023 14:19:33 +0000

̽��ֱ��research, a collaboration with Lancaster ̽��ֱ��, found that hedges can act as protective barriers against air pollution from major city roads by soaking up significant quantities of harmful particles emitted by traffic.

̽��ֱ��researchers applied a new type of pollution analysis, using magnetism to study particles trapped by a hedge separating a major 6-lane road from a primary school in Manchester, UK. They found that the hedge was especially successful in removing ultrafine particle pollution, which can be more damaging to health.

“Our findings show that hedges can provide a simple, cheap and effective way to help reduce exposure to local sources of pollution,” said lead author Hassan Sheikh from Cambridge’s Department of Earth Sciences.

̽��ֱ��new study differs from conventional air pollution studies because the researchers specifically measured magnetic particles, which originate from vehicle exhaust and the wearing of brake pads and tyres. That allowed them to distinguish local traffic pollution from other sources of air pollution.

In England alone, epidemiological studies estimate that 26,000 to 38,000 deaths and thousands of NHS hospital admissions are linked to dust-like particles carried in air pollution — much of which is generated by heavy traffic in urban environments.

This particle pollution — or particulate matter — is made up of a variety of chemical compounds, metals and other materials, some of which are toxic. ̽��ֱ��bigger particles (which are still tiny) measure less than 10 microns in diameter (called PM10) and are easily inhaled. Finer particles of less than 2.5 microns across (PM2.5) can penetrate deeper into the lungs and are small enough to enter the bloodstream.

Children attending schools next to busy roads are especially vulnerable to the effects of air pollution because their airways are still developing and they breath faster than adults.

Sheikh and the team studied magnetic particles captured by a western red cedar ‘tredge’ (trees managed at head-height), which was previously installed outside St Ambrose Primary School as part of a trial led by Lancaster ̽��ֱ��.

“Western red cedar does a great job in 'capturing ' particulate pollution because it has abundant, fine, evergreen leaves into which airborne particles bump and then settle from the roadside air,” said study co-author Professor Barbara Maher from the Lancaster ̽��ֱ��, who led the previous research.

Sheikh and the team measured particles of varying sizes on the leaves of the tredge and used air filters to measure particle abundance at intervals downwind toward the school playground.

They also developed a new experiment that used a tracer gas to understand how ultrafine particles (measuring less that 2.5 microns) moved through and were trapped by the tredge.

Their results revealed that there was a substantial reduction in particle pollution downwind of the tredge. “ ̽��ֱ��tredge acts as a permeable barrier, intercepting and capturing particles effectively on its leaves,” said Sheikh.

In the school playground, 30 metres from the road, they measured a 78% decrease in PM10 relative to roadside air.

They noticed that this removal was even more efficient for ultrafine PM2.5 particles. “What was remarkable was just how efficiently the tredge hoovered up the very finest particles,” said senior author Professor Richard Harrison, also from Cambridge’s Department of Earth Sciences. They measured an 80% reduction in the ultrafine particles just behind the tredge.

They think the ultrafine particles are preferentially filtered out by the tredge because they have a higher likelihood of being captured on the ridged surfaces of the red cedar leaves than coarser particles.

However, they did note a slight uptick in levels of magnetic PM2.5 in the playground, although they were still 63% below roadside air. “ ̽��ֱ��ultrafine particles were very effectively removed, but this shows that some air still goes over or around the tredge,” said Sheikh. Less is currently known about how particulate matter moves and disperses at this higher level, where air mixes around buildings and trees.

“That means the design and placement of tredges near playgrounds and schools should be carefully considered so that their ability to soak up particles can be used to maximum effect,” said Harrison.

Cllr Tracey Rawlins, Executive Member for Environment for Manchester City Council, said: "We were keen to be part of this study as Manchester seeks to embrace innovation in our efforts to become a greener city with cleaner air and tackle climate change.

" ̽��ֱ��findings underline the contribution which nature-based innovations can make to rising to that challenge. We look forward to delivering more green screens as well as many trees at school sites, complementing our education climate change strategy," said Rawlins.

Previously, Sheikh and Harrison used their new magnetic analysis to identify high levels of ultrafine particles polluting the London Underground. They now plan on working with colleagues at the MRC Toxicology Unit in Cambridge to find out what happens when cells are exposed to this type of ultrafine particle pollution.

Reference

Sheikh, H A, Maher, B A, Woods, A W, Tung, P Y, and Harrison, R J (2023). Efficacy of green infrastructure in reducing exposure to local, traffic-related sources of airborne particulate matter (PM). Science of the Total Environment, 166598.

A new study led by Cambridge ̽��ֱ�� confirms that planting hedges between roadsides and school playgrounds can dramatically reduce children’s exposure to traffic-related particle pollution.

Our findings show that hedges can provide a simple, cheap and effective way to help reduce exposure to local sources of pollution

Hassan Sheikh

H A Sheikh

Monitoring particle air pollution either side of the tredge installed at St Ambrose primary school, Manchester

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London Underground polluted with metallic particles small enough to enter human bloodstrem

sc604 — Thu, 15 Dec 2022 15:55:12 +0000

̽��ֱ��London Underground is polluted with ultrafine metallic particles small enough to end up in the human bloodstream, according to ̽��ֱ�� of Cambridge researchers. These particles are so small that they are likely being underestimated in surveys of pollution in the world’s oldest metro system.

Death of a dynamo – a hard drive from space

sc604 — Wed, 21 Jan 2015 18:00:01 +0000

̽��ֱ��dying moments of an asteroid’s magnetic field have been successfully captured by researchers, in a study that offers a tantalising glimpse of what may happen to the Earth’s magnetic core billions of years from now.

Using a detailed imaging technique, the research team were able to read the magnetic memory contained in ancient meteorites, formed in the early solar system over 4.5 billion years ago. ̽��ֱ��readings taken from these tiny ‘space magnets’ may give a sneak preview of the fate of the Earth’s magnetic core as it continues to freeze. ̽��ֱ��findings are published today (22 January) in the journal Nature.

Using an intense beam of x-rays to image the nanoscale magnetisation of the meteoritic metal, researchers led by the ̽��ֱ�� of Cambridge were able to capture the precise moment when the core of the meteorite’s parent asteroid froze, killing its magnetic field. These ‘nano-paleomagnetic’ measurements, the highest-resolution paleomagnetic measurements ever made, were performed at the BESSY II synchrotron in Berlin.

̽��ֱ��researchers found that the magnetic fields generated by asteroids were much longer-lived than previously thought, lasting for as long as several hundred million years after the asteroid formed, and were created by a similar mechanism to the one that generates the Earth’s own magnetic field. ̽��ֱ��results help to answer many of the questions surrounding the longevity and stability of magnetic activity on small bodies, such as asteroids and moons.

“Observing magnetic fields is one of the few ways we can peek inside a planet,” said Dr Richard Harrison of Cambridge’s Department of Earth Sciences, who led the research. “It’s long been assumed that metal-rich meteorites have poor magnetic memories, since they are primarily composed of iron, which has a terrible memory – you wouldn’t ever make a hard drive out of iron, for instance. It was thought that the magnetic signals carried by metal-rich meteorites would have been written and rewritten many times during their lifetime, so no-one has ever bothered to study their magnetic properties in any detail.”

̽��ֱ��particular meteorites used for this study are known as pallasites, which are primarily composed of iron and nickel, studded with gem-quality silicate crystals. Contained within these unassuming chunks of iron however, are tiny particles just 100 nanometres across – about one thousandth the width of a human hair – of a unique magnetic mineral called tetrataenite, which is magnetically much more stable than the rest of the meteorite, and holds within it a magnetic memory going back billions of years.

“We’re taking ancient magnetic field measurements in nanoscale materials to the highest ever resolution in order to piece together the magnetic history of asteroids – it’s like a cosmic archaeological mission,” said PhD student James Bryson, the paper’s lead author.

̽��ֱ��researchers’ magnetic measurements, supported by computer simulations, demonstrate that the magnetic fields of these asteroids were created by compositional, rather than thermal, convection – meaning that the field was long-lasting, intense and widespread. ̽��ֱ��results change our perspective on the way magnetic fields were generated during the early life of the solar system.

These meteorites came from asteroids formed in the first few million years after the formation of the Solar System. At that time, planetary bodies were heated by radioactive decay to temperatures hot enough to cause them to melt and segregate into a liquid metal core surrounded by a rocky mantle. As their cores cooled and began to freeze, the swirling motions of liquid metal, driven by the expulsion of sulphur from the growing inner core, generated a magnetic field, just as the Earth does today.

“It’s funny that we study other bodies in order to learn more about the Earth,” said Bryson. “Since asteroids are much smaller than the Earth, they cooled much more quickly, so these processes occur on shorter timescales, enabling us to study the whole process of core solidification.”

Scientists now think that the Earth’s core only began to freeze relatively recently in geological terms, maybe less than a billion years ago. How this freezing has affected the Earth’s magnetic field is not known. “In our meteorites we’ve been able to capture both the beginning and the end of core freezing, which will help us understand how these processes affected the Earth in the past and provide a possible glimpse of what might happen in the future,” said Harrison.

However, the Earth’s core is freezing rather slowly. ̽��ֱ��solid inner core is getting bigger, and eventually the liquid outer core will disappear, killing the Earth’s magnetic field, which protects us from the Sun’s radiation. “There’s no need to panic just yet, however,” said Harrison. “ ̽��ֱ��core won’t completely freeze for billions of years, and chances are, the Sun will get us first.”

̽��ֱ��research was funded by the European Research Council (ERC) and the Natural Environment Research Council (NERC).

Hidden magnetic messages contained within ancient meteorites are providing a unique window into the processes that shaped our solar system, and may give a sneak preview of the fate of the Earth’s core as it continues to freeze.

It’s like a cosmic archaeological mission

James Bryson

̽��ֱ��Esquel pallasite from the Natural History Museum collections, consists of gem-quality crystals of the silicate mineral olivine embedded in a matrix of iron-nickel alloy.

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