Coal-fired power stations affect rainfall patterns, says global study

An international study has revealed that modern coal-fired power stations produce more ultrafine particles (UFPs) than road traffic and can modify and redistribute rainfall patterns. The 15-year study indicates that filtration systems on modern coal-fired power stations are a persistent source of UFPs and can have considerable impacts on climate.

In urban areas, road traffic has been considered the main source of small-particle emissions, which have the potential to adversely affect health and the environment. However, longitudinal data collected by Professor Wolfgang Junkermann from the Karlsruhe Institute of Technology in Germany and Professor Jorg Hacker from Airborne Research Australia have revealed that modern fossil fuel-burning power stations, refineries and smelters, in particular, affect regional climate.

In the Bulletin of the American Meteorological Society, the researchers reported that coal-fired power stations emit high concentrations of UFPs via the filtration of exhaust gas. The study reported several key findings:

• Modern coal-fired power stations emit more UFPs than urban road traffic.
• UFPs can harm human health.
• UFPs can affect rainfall distribution on local to regional scales by increasing the condensation nuclei count.
• UFPs can be transported for hundreds of kilometres leading to localised ‘particle events’ (dramatic spikes in short-term particle concentrations on the ground) far away from their source.
   

The study found that UFP concentrations have increased continuously since modern coal-fired power stations were commissioned in many locations around the world. For the measurement flights in Europe, Australia, Mexico and Inner Mongolia, the research team used two rather unusual research aircraft: a comprehensively instrumented motor glider in Australia and a ‘trike’ developed in Germany. The flying laboratories were equipped with highly sensitive instruments and sensors measuring dust particles, trace gases, temperature, humidity, wind and energy balances.

“Our two research aircraft are particularly suitable to follow the plumes from the smoke stacks downwind for hundreds of kilometres and study their behaviour in great detail,” Prof Hacker said.

The researchers linked data from the aircraft with meteorological observations and used dispersion and transport models to trace the particles’ origin. “In this way, we found that fossil power stations have for many years become the strongest individual sources of ultrafine particles worldwide. They massively influence meteorological processes and may cause extreme weather events, including intensive rain events. By redistributing rainfall events, this can lead to drier than usual conditions in some places and to unusually heavy and persistent strong rainfall elsewhere,” Prof Hacker explained.

“Exhaust-gas cleaning takes place under conditions that are optimal for the new formation of particles. Ammonia is added to the exhaust gases in order to convert nitrogen oxides into harmless water and nitrogen,” Prof Junkermann explained. At this time, ammonia is available at the right mixing ratio for particle formation, resulting in high concentrations in the exhaust gas.

The research paper is available at the Bulletin of the American Meteorological Society.

Image courtesy of Flinders University.