PNNL

The Science

In the atmosphere, individual soot particles emitted from human activities often encounter and combine with organic material, forming soot-containing particles. A research team led by scientists from the U.S. Department of Energy's (DOE) Pacific Northwest National Laboratory and Michigan Technological University established a link between the viscosity of the organic material and its distribution within the soot-containing particle. This mixing configuration is important because it alters the particles' ability to absorb and scatter solar radiation.

The scientists discovered that organic material of low viscosity partially or completely encapsulated soot particles, while highly viscous organic material often attaches to the surface of co-existing soot particles or do not even stick together, remaining separate.

The Impact

Soot particles strongly absorb solar radiation, and therefore, affect Earth's energy balance. However, their optical properties strongly depend on how the individual soot particles mix with other particles in the atmosphere (internal mixing).

This study identified the viscosity of organic matter in the atmosphere as a key factor that influences the distribution of organic matter within soot-containing particles. These findings will improve aerosol models that predict the mixing state of soot via condensation and coagulation processes, thereby improving radiative forcing calculations and climate predictions.

Reference: N. Sharma, S. China, J. Bhandari, K. Gorkowski, M. Dubey, R.A. Zaveri, and C. Mazzoleni, (2018). "Physical Properties of Aerosol Internally Mixed With Soot Particles in a Biogenically Dominated Environment in California." Geophysical Research Letters 45(20), 11,473-11,482. [DOI: 10.1029/2018GL079404].