18 December 2013

New measurements on the properties and spread of airborne pollen to improve the forecasting of this natural allergen, which affects human health as well as the Earth’s temperature, have been published in a new international study led by Dr Detlef Mueller in the research journal Atmospheric Environment.

Pollen – a major contributor to pollution

Pollen, considered to be one of the main causes of allergies and also a major contributor to pollution, is easily spread through the air and its impact on human health may increase due to climate change. The physical and optical properties of pollen also determine how much sunlight arrives on the Earth's surface – and the amount of sunlight reaching the surface has a major influence on our planet's temperature.

Dr Mueller, now at the University of Hertfordshire's School of Physics, Astronomy and Mathematics and previously at Leibniz Institute of Tropospheric Research (TROPOS) in Germany, said: "Together with colleagues from the Gwangju Institute of Science and Technology (GIST) in Korea, we used a tool called a polarisation lidar to observe particles, including pollen particles, in the atmosphere."

 "We found that pollen particles from trees are distributed in the lower part of the atmosphere in cities.  This is caused by small air convections, air updrafts and downdrafts – and good weather conditions, such as high temperatures and low relative humidity, also contribute to this."

Polarisation lidar – a new research technology

Polarisation lidar (Light Detection and Ranging) is a relatively new research technology.  Operating in a similar way to radar, it measures the difference in time between sending a laser pulse up into the sky and receiving the back-reflected laser pulse – allowing the distance between the instrument and the reflecting object (pollution particles in this case) to be computed.

Using these sophisticated laser techniques, the team measured some different optical properties of airborne pollen for the first time – including the light-extinction coefficient which enables the determination of the optical depth of the atmosphere.  This optical depth determines the amount of sunlight falling onto Earth's surface, and hence directly influences Earth's temperature.

Strong allergic reactions

Dr Mueller continued: "Dust is known to act as carrier of bacteria and fungi as well as pollen.  We observed an increase in the number of people who were hospitalised after large dust outbreaks over South Korea where we were taking the measurements.  They suffered from breathing problems, eye inflammations and other strong allergic reactions. And we have noted similar conditions around the world, such as in the Sahel Zone in Africa, where cases of meningitis may have been caused by bacteria carried by dust."

Dr Mueller recently joined the University of Hertfordshire where he is funded by the Royal Society through the Wolfson Research Merit Award which is given to outstanding scientists in the UK.  He continues to develop and improve lidar measurement technology for climate research, and also for investigating the spread of dust, spores and fungi.  As well as helping to improve the forecast of the spread of natural airborne allergens, this research will help to find new ways of reducing crop losses - it is estimated that approximately sixteen per cent of the global crop yield is lost each year due to fungal diseases.

Y. M. Noh, D. Müller, H. L. Lee, T. J. Choi (2013): Influence of biogenic pollen on optical properties of atmospheric aerosols observed by lidar over Gwangju, South Korea, Atmospheric Environment, Volume 69, pages 139-147,http://dx.doi.org/10.1016/j.atmosenv.2012.12.018