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Physical Sciences
Research Highlights

November 2016

Biogenic Particles Contribute to Formation of Aerosols

Scientists show how a compound emitted by pine trees helps form new aerosol particles

Artistic representation of alpha pinene
This combined experimental and computational study can help improve the accuracy of numerical models that simulate the effect of organic aerosols on climate and air quality.

Climate, air quality, and health are all influenced by aerosols. These particles are produced from vehicular and industrial emissions, as well as through reactions involving compounds released by plants. A recent study by scientists at Pacific Northwest National Laboratory and the Chinese Academy of Sciences provides molecular-level insights into how α-pinene -- a compound emitted in large quantities by pine trees -- helps form new atmospheric aerosols.

Why It Matters: The findings reveal key differences in how cis-pinic acid -- an important product from α-pinene -- forms clusters with various natural and industrial solvents found in the atmosphere. This information could improve the accuracy of models that simulate the effect of certain types of aerosols on climate and air quality.

Methods: Atmospheric organic aerosols affect Earth's climate by influencing cloud formation and by absorbing or reflecting the sun's energy. They have also been implicated in serious health problems such as lung and heart disease. These particles are produced from vehicular and industrial emissions, as well as through oxidation of organic compounds released by plants. Pine and other coniferous trees emit significant quantities of α-pinene, which subsequently interacts with oxidants in the atmosphere to produce a compound called cis-pinic acid, among other products.

Compounds such as cis-pinic acid have been shown to contribute to the growth of newly formed aerosol particles. To shed light on this process, a team from Pacific Northwest National Laboratory and the Chinese Academy of Sciences combined negative ion photoelectron spectroscopy and theoretical calculations to examine early stage formation of clusters consisting of cis-pinic acid and three common solvents: water, methanol, and acetonitrile. The researchers used low temperature photoelectron spectroscopy at EMSL, a U.S. Department of Energy national scientific user facility. 

The findings revealed cis-pinic acid takes on different functions and structures in different solvent environments. These molecular-level insights into how volatile organic compounds such as cis-pinic acid form solvent clusters help to improve the scientific understanding of how atmospheric organic aerosols form.

What's Next? These findings could be incorporated into models to enable more accurate representations of particle growth by condensation of organic compounds and to simulate their effect on climate and air quality.

Acknowledgments

Sponsors: GLH and MV were funded by the EMSL Intramural Aerosol Science Theme Funding, and XBW was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. The theoretical work was supported by the National Natural Science Foundation of China (Grant No. 21273232) and Hundred Talents Program of Chinese Academy of Sciences and conducted on the clusters of the Center for Theoretical and Computational Chemistry at Dalian Institute of Chemical Physics. 

Research Area: Chemical Sciences

User Facility: The experimental work was performed using EMSL, a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory 

Research Team: Xiang-Tao Kong and Ling Jiang, Chinese Academy of Sciences; Gao-Lei Hou,  Marat Valiev, and Xue-Bin Wang, Pacific Northwest National Laboratory

Reference: Hou GL, XT Kong, M Valiev, L Jiang, and XB Wang. 2016. "Probing the Early Stages of Solvation of cis-pinate Dianions by Water, Acetonitrile, and Methanol: A Photoelectron Spectroscopy and Theoretical Study." Physical Chemistry Chemical Physics 18:3628. DOI: 10.1039/c5cp05974g


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In short ...

Scientists at Pacific Northwest National Laboratory and the Chinese Academy of Sciences provides molecular-level insights into how alpha-pinene, a compound emitted in large quantities by pine trees, helps form new atmospheric aerosols. This study can help improve the accuracy of models that simulate the effect of certain aerosols on climate and air quality.

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