Modelling Studies of HOMs and Their Contributions to New Particle Formation and Growth: Comparison of Boreal Forest in Finland and A Polluted Environment in China


Recently, Prof. Aijun Ding's research group made progress on comparison of new particle formation in atmospheric conditions of Eastern China and boreal forest of northern Europe. Under the framework of the Joint International Research Laboratory of Atmospheric and Earth Systematic Sciences (JirLATEST), through cooperation with Prof. Markku Kulmala in University of Helsinki (Academician of Academy of Finland, Foreign Academician of Chinese Academy of Sciences),,  the research group compared the new particle formation and growth in typically different environmental conditions and revealed the quantitative contributions made by Highly Oxygenated Multifunctional Compounds (HOMs) to them. The MALTE-BOX model developed by University of Helsinki and the data observed respectively at two of the most representative sites, i.e. Station for Observing Regional Processes of the Earth System (SORPES) of Nanjing University and Station for Measuring Ecosystems-Atmosphere Relationships (SMEAR II) of University of Helsinki in Finland, were applied in this study. The article titled Modelling studies of HOMs and their contributions to new particle formation and growth: comparison of boreal forest in Finland and a polluted environment in China was published in Atmos. Chem. Phys. (Impact Factors 5.509), EGU.

New particle formation (NPF) and particle growth are the internationally cutting-edge scientific issue in the field of aerosol, which exert an important influence equally on air pollution and climate change. One of the hotspot issues recently is the study on the quantitative contributions of HOMs to the NPF and particle growth worldwide. As measurements of relevant elements remain rather difficult, their quantitative roles in NPF and particle growth in different environments in the world have not been well studied yet, leaving huge uncertainty for people to understand the climactic effects of aerosol on a global scale. The SORPES of Nanjing University and the SMEAR II of University of Helsinki happen to represent two globally-distinctive atmospheric environments: the Scots-pine-forest surrounded boreal area less frequented by human beings (with high monoterpene emissions) and the Yangtze River Delta city cluster in eastern China, which is intensively influenced by human activities (high emissions from fossil fuel burning). The comparative study that combining observations and models at the two sites is conducive to the understanding of the aerosol formation mechanisms and its climate and environmental effects.

Figure 1. SORPES and SMEAR II site locations (a: SO2, b: monoterpenes)

By applying MALTE-BOX model and WRF-Chen model, the HOMs concentrations and NPF event in distinctive environments are simulated and their roles in NPF and particle growth are discussed. The model provides an acceptable agreement between the simulated and measured concentrations of sulfuric acid and HOMs at SMEAR II. The sulfuric acid and HOM organonitrate concentrations are significantly higher while the concentrations of HOM monomers and dimers from monoterpene oxidation are lower at SORPES. The model simulates the NPF events in clean areas like the boreal forest in Finland with a good agreement but underestimates the NPF and particle growth at SORPES, indicating a dominant role of anthropogenic processes in the polluted environment. At SMEAR II, HOMs from monoterpene oxidation dominate the growth of ultrafine particles while sulfuric acid and HOMs from aromatics oxidation play a more important role in the growth of nanoparticles at SORPES (figure 2). The study highlights the distinct role of sulfuric acid and HOMs in NPF and particle growth in different environmental conditions and suggests the need for molecular-scale measurements in improving the understanding of NPF mechanisms in polluted areas like eastern China.

Figure 2 The relative contributions of precursor vapours to the growth of sub-100 nm particles at (a) SMEAR II and (b) SORPES. 

This study is jointly finished with Michael Boy and others in Kulmala's team of University of Helsinki under the framework of JirLATEST. The study is supported by atmospheric special program of Space-sky-land Integrated Monitoring Technologies of Combined Atmospheric Pollution in Eastern China of National Key R&D Program of China, key program of atmospheric combined pollution of the National Natural Science Foundation of China, the National Science Fund for Distinguished Young Scholars and Jiangsu Collaborative Innovation Center for Climate Change. Assistant researcher of Nanjing University Dr. Ximeng Qi is the first author and Prof. Aijun Ding is the corresponding author.

Related papers: 

X. Qi, A. Ding*, P. Roldin, Z. Xu, P. Zhou, N. Sarnela, W. Nie, X. Huang, A. Rusanen, M. Ehn, M. P. Rissannen, T. Petaja, M. Kulmala, and M. Boy: Modeling studies of HOMs and their contributions to new particle formation and growth: Comparison of boreal forest in Finland and a polluted environment in China, Atmos. Chem. Phys., 18, 16, 11779-11791, 2018.

X. Qi, A. Ding*, W. Nie, T. Petaja, V.-M. Kerminen, E. Herrmann, Y. Xie, L. Zheng, H. Manninen, P. Aalto, J. Sun, Z. Xu, X. Chi, X. Huang, M. Boy, A. Virkkula, X. Yang, C. Fu, M. Kulmala,?Aerosol size distribution and new particle formation in the western Yangtze River Delta of China: 2 years of measurements at SORPES station, Atmos. Chem. Phys., 15, 12445-12464, 2015.

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