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Air pollution declines with height
  • Air pollution declines with height

Copyright: Elena Chernyshova / Panos

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  • Researchers in India find pollution levels vary at different levels above ground

  • Pollutant concentration decreases in areas up to 800 metres from the ground

  • Some pollutant particles that find their way up can potentially influence climate

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[NEW DELHI]A pilot study on air pollutionin New Delhi, India’s capital,showsthatthe concentration of black carbon aerosol and particulate matter varies with height.
 
Though there are manyother researches on pollutant concentration, the study, published in Science of the Total Environment, is the first attempt to profile how pollutionvaries as one goes up from the ground.
 
S. Tiwari, scientist at the Indian Institute of Tropical Meteorology who participated in the research, says, “The study will help us better understand the dynamics between atmospheric aerosol and pollution.”

“The study will help us better understand the dynamics between atmospheric aerosol and pollution.”

S. Tiwari, Indian Institute of Tropical Meteorology

 

Using a hydrogen-filled tethered balloon, scientistsfrom India, Sweden and the United Statesmade measurements at different heights up to one kilometre from the ground.They found that black carbon aerosol and particulate matter concentration weremaximum at the surface and decreased as one went upwards.
 
However, regions up to 200 metres from the ground remained substantially polluted although less in comparison to ground levels. Beyond 200 metres, pollutant concentration decreased up to 800 metres and remained unchanged untilthe one-kilometre mark.
 
Some pollutant particles, after being emitted closer to the ground, find their way up under certain conditions. This results in significant redistribution of pollutant concentrationthat can potentially influence climate in the region.
 
“Black carbon, being lighter than other aerosols like dust, is transported upward easily in favourable meteorological conditions. So black carbon mass fraction is expected to increase, and this would lead to enhanced heating of the atmosphere,”Sagnik Dey, assistant professor at theCentre for Atmospheric Sciences, Indian Institute of Technology, Kanpur, tells SciDev.Net
 
The study also providessome insights into how fog and particulate matter combine to reduce visibility in New Delhi where smog has assumed epidemic proportions, making traffic disruption a norm during winter months.
 
The researchers found that on foggy days, ground level concentration of black carbon and particulate matter increased substantially, resulting in higher light scattering which leadsto reduced visibility. According to the researchers, such correlations are observed in other big polluted cities like Shanghai in China.
In addition to finding the vertical profile, the study exposes the alarming levels of air pollution in New Delhi. Concentration of particulate matter of diameter 2.5 micrometres or less was found to be way more than the upper limits prescribed by the National Ambient Air Quality Standards, US Environmental Protection Agency, World Health Organization and the European Union Air Quality Standards.
 
These particles, about 70 times smaller than the thickness of a human hair, make their way into the human body and go deep into the lungs. According to the latest WHO report on ambient air pollution, in 2012, poor ambient air quality caused more than 620,000 deaths in India.
 
This piecewas produced by SciDev.Net’s South-East Asia & Pacific desk.

References

Tethered balloon-born and ground-based measurements of black carbon and particulate profiles within the lower troposphere during the foggy period in Delhi, India (Science of The Total Environment, December 2016

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