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Coal Power Stations Disrupt Regional Rainfall

Modern coal-fired power stations produce more ultrafine dust particles than road traffic and can even modify and redistribute rainfall patterns, according to a 15-year international study published in the Bulletin of the American Meteorological Society (https://goo.gl/c2t5H6).

The study indicates that the filtration systems of modern coal-fired power stations are the biggest source of ultrafine particles (UFP), and can have considerable impacts on climate in several ways.

Prof Wolfgang Junkermann from the Karlsruhe Institute of Technology and Prof Jorg Hacker from Airborne Research Australia – who are affiliated with Flinders University – found that:

  • modern coal-fired power stations emit more UFP than urban road traffic;
  • UFP can harm human health;
  • UFP can affect rainfall distribution on local to regional scales by increasing the condensation nuclei count; and
  • UFP can be transported in layers with high concentrations for hundreds of kilometres, and then lead to localised spikes in short-term particle concentrations at ground level far from their source.

The research also found that ultrafine particle concentrations have increased continuously since modern coal-fired power stations were commissioned around the world. While forest fires, dust storms and volcanic eruptions produce fine particles, they are mostly not in the nanometre range of UFP, which have a diameter of less than 100 nm and as a result can have an enormous impact on environmental processes. “The UFP offer surfaces for chemical reactions in the atmosphere or may influence the properties of clouds and precipitation,” Junkermann explains.

The researchers used two unusual small research aircraft – the world’s most comprehensively instrumented motorglider in Australia and a “trike” that is believed to be the smallest manned research aircraft worldwide – to take airborne particle measurements in Europe, Australia and even Mexico and Inner Mongolia. The aircraft 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,” Hacker says. The scientists then linked these data with meteorological observations and used dispersion and transport models to trace back their 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,” Hacker says.

To study the existence and distribution and UFP transport processes, the researchers not only flew their instruments near or downwind of coal-fired power stations but also over remote regions where very low UFP concentrations have been measured in the past at ground level. In regions with conspicuous precipitation trends, such as inland Western Australia and Queensland, the researchers found that UFP concentrations have increased constantly and could be linked to emissions made by coal-fired power stations and refineries.

After smoke stacks emit UFP at a height of 200–300 metres, they typically spread over several hundreds of kilometres depending on weather and climate conditions in the atmosphere, the researchers found.