New findings of chemical differences between PM1 and PM2.5 might reshape air pollution studies

March 09, 2020

Current air pollution studies largely rely upon aerosol mass spectrometers, most of which can only measure submicron aerosol (PM1) species--particulate matter with aerodynamic diameter less than 1 μm. In many studies, PM1 aerosol species are therefore used to validate those of PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) in chemical transport models, and estimate particle acidity (pH) and aerosol water content which are key parameters in studying heterogeneous reactions. However, are there chemical differences between PM1 and PM2.5? Will the differences bring uncertainties into air pollution studies, especially in highly polluted environment, e.g., China and India?

Professor Yele Sun and his team with the Institute of Atmospheric Physics, Chinese Academy of Sciences tried to answer these questions by characterizing the chemical differences between PM1 and PM2.5 in a highly polluted environment in north China in winter using a newly developed PM2.5 Time-of-Flight Aerosol Chemical Speciation Monitor. They found that the changes in PM1/PM2.5 ratios as a function of relative humidity (RH) were largely different for primary and secondary aerosol species.

"If organics is the dominant component (> 50%) of particulate matter and RH is below 80%, the chemical species in PM1 would be highly correlated with those in PM2.5. PM1 can be representative of PM2.5" says Sun, the first and corresponding author of this study, "however, if sulfate, nitrate, and secondary organic aerosol that are formed from secondary formation are dominant components, there would be large chemical differences between PM1 and PM2.5 at RH > 60%. The major reason is that these secondary species have higher hygroscopicity and can uptake more water during higher RH periods".

SUN also evaluated the impacts of chemical differences between PM1 and PM2.5 on the predictions of pH and aerosol water content with thermodynamic modeling. "The chemical differences of between PM1 and PM2.5 have negligible impacts on pH prediction, but has a large impact on prediction of aerosol water content by up to 50-70%." says Sun.

"Our findings are important because current air pollution studies in highly polluted environment, particularly during severe haze events with high RH must consider the chemical differences between PM1 and PM2.5." says Sun, "Validation of model simulations in chemical transport models also need to consider such differences."
The study is published in Geophys. Res. Lett.(

Institute of Atmospheric Physics, Chinese Academy of Sciences

Related Particulate Matter Articles from Brightsurf:

Seeing dark matter in a new light
A small team of astronomers have found a new way to 'see' the elusive dark matter haloes that surround galaxies, with a new technique 10 times more precise than the previous-best method.

Zooming in on dark matter
Cosmologists have zoomed in on the smallest clumps of dark matter in a virtual universe - which could help us to find the real thing in space.

Particulate plutonium released from the Fukushima Daiichi meltdowns
Small amounts of plutonium (Pu) were released from the damaged Fukushima Daiichi Nuclear Power Plant (FDNPP) reactors into the environment during the site's 2011 nuclear disaster.

How particulate matter arises from pollutant gases
When winter smog takes over Asian mega-cities, more particulate matter is measured in the streets than expected.

Fine particulate matter may increase mortality among young patients with certain cancers
An analysis of nearly 16,000 young patients with cancer in Utah revealed that exposure to fine particulate matter was associated with increased mortality at five and 10 years after diagnosis of certain cancers.

Being fun is no laughing matter
A longitudinal study examined whether children who are well-liked and children who are popular got that way by being fun to hang around with.

Looking for dark matter
Dark matter is thought to exist as 'clumps' of tiny particles that pass through the earth, temporarily perturbing some fundamental constants.

Tracking down the mystery of matter
Researchers at the Paul Scherrer Institute PSI have measured a property of the neutron more precisely than ever before.

Finer particulate matter (PM1) could increase cardiovascular disease risk
In addition to harmful gases such as carbon monoxide, air pollution contains tiny particles that have been linked to health problems, including cardiovascular disease and asthma.

Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.

Read More: Particulate Matter News and Particulate Matter Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to