Gain Insight into Chemical Components Driving New Particle Growth on a Basis of Particle Hygroscopicity and Volatility Measurements: a Short Review

TLDR: In this article, the particle hygroscopicity and volatility of new particles were measured to infer chemical composition of the particle and the extreme low volatility components in new particles are observed in both clean and polluted environments and contributed to 1/4 of particle growth in a rural site of Melpitz, Germany.

Abstract: Atmospheric new particle formation and growth play important roles in climate change and air quality. Aiming at better understanding the particle growth mechanisms, the measurements on chemical composition of new particles are imperative. However, the instruments directly detecting chemical composition of nanoparticles (<30 nm) are very rare due to the tiny particle masses involved and low transmission efficiency. Alternatively, the hygroscopicity and volatility of nanoparticles were measured to infer chemical composition of the particle. Here, we summarized the progresses in studying the new particle growth processes on a basis of particle hygroscopicity and volatility measurements. Compared to clean environments, such as in boreal forest, the water soluble components contribute a larger fraction of newly formed particles (below 50 nm) in the polluted environments, such as in the sulfur-rich atmosphere of North China Plain. The extreme low volatility components in new particles were observed in both clean and polluted environments and contributed to 1/4 of particle growth in a rural site of Melpitz, Germany. In the future, the instruments capable of precisely detecting the hygroscopicity and volatility of particles below 10 nm are needed. Except for differential mobility analyzer, other novel methods without limitation of charging and transmission efficiency should be considered. The hygroscopicity and volatility of atmospheric relevant compounds should be investigated in the laboratory in order to provide supportive information to explain the hygroscopicity and volatility of new particle in the ambient air.