Highly Oxygenated Molecules in the Amazon, Beijing and elsewhere

Air pollution is created by enhanced concentrations of particles in the air. Some of these particles are so large that you can easily see them, such as dust or sand. However many are much smaller so that they can’t be seen with the naked eye. This fine particulate matter (PM2.5) is often more dangerous because smaller particles can penetrate deeper into the lung. In addition, these particles play an important role in our climate system. In the atmosphere, for example, they absorb and reflect light, and act as condensation nuclei for clouds. Thus PM2.5 plays a key role for public health and for climate change.

In a new study, Dr. Haijie Tong and co-authors studied a subset of PM2.5, the so-called highly oxygenated molecules (HOMs) and its relationship with radical yield and aerosol oxidative potential. They analyzed fine particulate matter in the air in multiple locations. This including the highly polluted megacity Bejing and in the pristine rainforest at ATTO. They wanted to get insights into the chemical characteristic and evolutions of these HOM particles. In particular, they wanted to find out more about the potential of HOMs to form free radicals. These are highly reactive species with unpaired electrons.

Indeed, they found that the potential that such free radicals are formed is closely associated with the relative abundance of HOMs, radical yield of particulate matter, and the concentration of PM2.5In comparing the different study sites, they made some interesting observations. The forest sites, including at ATTO, the overall concentration of PM2.5is low. But the relative abundance of HOMs within the PM2.5 is fairly high. Therefore, the radical yield of PM2.5 at ATTO is high, but the total radical abundance per volume of air is still pretty low. On the other hand in the megacities, there are lots of PM2.5, but which contains few HOMs. Therefore, the PM2.5 has a lower radical yield compared to the forest sites. However, the total abundance per volume of air is much higher in the cities.

Graphical Abstract
Graphical Abstract from Tong et al. (2019)
Tong et al. (2019) published the paper titled “Radical Formation by Fine Particulate Matter Associated with Highly Oxygenated Molecules” in Environmental Science and Technology: https://doi.org/10.1021/acs.est.9b05149

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