Background:
About half of the particulate matter in the atmosphere caused by human activities comes from secondary aerosols produced by the conversion of gases. It is generally believed that photochemical reactions are the main pathway for the formation and evolution of new particles. However, it has been found that relying solely on atmospheric precursor composition and photochemical reactions cannot fully explain the actual occurrence of new particle formation and growth phenomena, leading to large uncertainties in the prediction of severe pollution events.
A research group led by Dr. Kun Luo from Zhejiang University and Beijing Normal University cloud-aerosol team proposed that the evolution of atmospheric turbulence has important implications for the formation and evolution of new particles.
Research Methods:
The researchers analyzed a large number of new particle formation events that occurred in China, the United States and Finland, as well as various characteristic parameters of atmospheric physics and aerosols observed during the same period. They found that the precursor composition and concentration levels in these regions were very different, but they all had one thing in common: the emergence of new particles was preceded by a strong trend towards the development of turbulence in an unstable atmosphere.
Inspired by this phenomenon, based on the traditional chemical nucleation mechanism and the distribution properties of ultrafine particles in the real atmosphere, the researchers analyse the distribution and change properties of nucleated molecules in the flow field under the control of atmospheric turbulence and propose the physical mechanisms of atmospheric turbulence evolution that influence the formation and evolution of new particles through external field observations and molecular dynamics simulations.
1. particle formation: enhanced turbulence can increase the local supersaturation of condensable molecules, accelerating the formation of clusters of precursor molecules and promoting the nucleation process (which increases the source for new particle formation).
2. particle growth: the newly formed small particles are easily removed from the existing large particles by the process of contact and adsorption, while the sufficient mixing effect of strong turbulence can effectively dilute the concentration of large particles (reduce the sink for the formation of new particles) and promote the rapid growth of newly formed small particles.
The work was published at https://academic.oup.com/nsr/article/8/3/nwaa157/5867800 and the team at the Institute of Thermal Engineering of Zhejiang University simulated the theory using a molecular dynamics model and obtained results consistent with observations, confirming the mechanism described above.
About Professor Luo
Kun Luo is a professor at Zhejiang University. He is a Distinguished Young Scholar, and is a member of the board of the Chinese Society of Engineering Thermophysics, and Deputy Secretary General of the Process Simulation and Simulation Committee of the Chinese Chemical Society.
For many years, he has actively engaged in theoretical modeling and numerical simulation of complex multi-scale coupled problems in power and environmental engineering, including computational multiphase flow, computational combustion, multi-scale simulation of wind energy utilization, and multi-scale modeling of air quality in atmospheric pollution areas. He proposed a new method for direct numerical simulation of complex large-scale multiphase turbulent combustion processes, discovered new phenomena and mechanisms of coupling multiphase turbulent combustion processes at the interface, developed a new model for more accurate engineering calculations, and successfully applied it to engineering practice, which brought obvious economic and environmental benefits. As a project leader and research manager, he has conducted more than ten national/provincial research projects and published more than 200 papers in scholarly journals.
About SIAS
Shanghai Institute for Advanced Study of Zhejiang University (SIAS) is a jointly launched new institution of research and development by Shanghai Municipal Government and Zhejiang University in June, 2020. The platform represents an intersection of technology and economic development, serving as a market leading trail blazer to cultivate a novel community for innovation amongst enterprises.
SIAS is seeking top talents working on the frontiers of computational sciences who can envision and actualize a research program that will bring out new solutions to areas include, but not limited to, Artificial Intelligence, Computational Biology, Computational Engineering and Fintech.