Dr Evelyn Freney is discovering how manmade and natural aerosol particles help to form clouds and affect our health.
Viewed from space, the Earth’s atmosphere is a remarkably thin, gassy blanket that envelopes the planet. But without it there would be no habitable climate and no life as we know it today.
Dr Evelyn Freney wants to understand more about this all-important zone, and particularly how tiny aerosol particles (dust, ice, manmade pollution) behave high in the sky where clouds form, and closer to sea level where we inhale them.
“We try and understand different sources of aerosol particles in the atmosphere, from manmade activities but also natural aerosols from sources, such as forests or the sea. These aerosols can grow to become larger particles and can influence cloud formation in the atmosphere,” explains Freney, who is a CNRS researcher at the Université Blaise Pascal, in Clermont-Ferrand, France. “We try and study the formation of these aerosol particles and then follow their evolution throughout their full life cycle.”
What influences cloud formation
Despite the familiarity of clouds, there’s still much to find out about how they form in the atmosphere, and Freney is interested in how particle behaviour affects the process. “Cloud formation is strongly influenced by the physical and chemical properties of aerosol particles,” she explains.
She has recently been working on an EU-funded project to analyse how individual particles interact with cloud droplets.
Some of her data come from the high-altitude Puy de Dôme observatory in Central France, where several instruments collect information about particle size and cloud droplets almost 1.5km above sea level.
Freney is particularly interested in characterising how ice clouds form.
“We are currently building an instrument that will allow us to characterise the properties of particles and how they form not just liquid water droplets but ice crystals in the atmosphere,” she says.
“There is a great deal of uncertainty associated with the formation of ice clouds, as well as their impact on the climate. This uncertainty is due to the fact that they are found at high altitudes in the atmosphere and the difficulty in finding instruments that are capable of generating cold atmospheric conditions required to characterise ice crystal properties.”
Images of atmospheric particles taken with an electron microscope
Up close with the particles
Freney’s work involves taking measurements of the types and behaviours of the tiny atmospheric particles, but in a previous job at Arizona State University she got a closer look at their form, using an electron microscope to see their minute shapes.
“You can see the morphology of single aerosol particles and how they are mixed together, you can really see the particles, rather than it just being numbers on a screen,” she says. “It was quite cool.”
During this time she also worked on the Southeast Queensland Cloud Seeding Programme, which looked for optimum ways to ‘make’ clouds in the Australian region with a view to addressing water shortages.
Impact of aerosols on health
While aerosols are players in forming clouds, which in turn play roles in weather and climate, Freney is also interested in how aerosols behave closer to terra firma, where we inhale them. During her PhD at the University of Edinburgh, she analysed the properties of aerosol particles from manmade and natural sources, and collaborated with the medical school to look at the impact of these tiny agents on health.
“Willing volunteers inhaled the concentrated aerosol particles, and the work showed that ‘clean’ particles, such as mineral dust or sea salt, did not have a big influence on health, but if the experiment used vehicle particles, the impacts on health were much more pronounced. That was interesting.”
It highlights the need to take not just the size of airborne particles into account when measuring pollution, but also the nature of the particles too, she notes.
“We are inclined to look at particle concentrations in a certain size range,” she says. “But sometimes we have to consider whether those particles are dust or sea salt and so the impact on health may not be very important.”
The appliance of science
Freney, who studied applied science at Limerick Institute of Technology, says she was interested in science at school but focused on chemistry and biology.
“I was never attracted to the physics or maths back then,” she says.
Yet today, physics and maths are a mainstay of her work and they have opened up exciting new opportunities for her to work in atmospheric science. So she would like to see students – and particularly girls – learn more about how maths and physics can be used beyond school.
“I think students should learn more at a young age about the applications of these subjects so that more and more women get interested in them.”
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