Hygroscopic properties of newly formed ultrafine particles at an urban site surrounded by deciduous forest (Sapporo, northern Japan) during the summer of 2011

Abstract

Abstract. To investigate the hygroscopic properties of ultrafine particles during new particle formation events, the hygroscopic growth factors of size-segregated atmospheric particles were measured at an urban site in Sapporo, northern Japan, during the summer of 2011. The hygroscopic growth factor at 85 % relative humidity [g(85 %)] of freshly formed nucleation mode particles was 1.11 to 1.28 (average: 1.16 ± 0.06) at a dry particle diameter (D p ) centered on 20 nm, which is equivalent to 1.17 to 1.35 (1.23 ± 0.06) at a dry D p centered on 100 nm after considering the Kelvin effect. These values are comparable with those of secondary organic aerosols, suggesting that low-volatility organic vapors are important to the burst of nucleation mode particles. The equivalent g(85 %) at a dry D p of 100 nm for nucleated particles that have grown to Aitken mode sizes (1.24 to 1.34; average: 1.30 ± 0.04) were slightly higher than those of newly formed nucleation mode particles, suggesting that the growth of freshly formed nucleation mode particles to the Aitken mode size can be subjected to condensation of not only low-volatility organic vapors, but also water-soluble inorganic species. Based on this result, and previous measurement of radiocarbon in aerosols, we suggest that the burst of nucleation mode particles and their subsequent growth were highly affected by biogenic organic emissions at this measurement site, which is surrounded by deciduous forest. Gradual increases in mode diameter after the burst of nucleation mode particles were observed under southerly wind conditions, with a dominant contribution of intermediately hygroscopic particles. However, sharp increases in mode diameter were observed when the wind direction shifted to northwesterly or northeasterly, with a sharp increase in the highly hygroscopic particle fraction of the Aitken mode particles, indicating that the hygroscopic growth factor of newly formed particles is perturbed by the local winds that deliver different air masses to the measurement site.

Atmospheric new particle formation and growth: review of field observations

“…Hygroscopicity and volatility measurements made in forested environments indicate that both highlyand less-hygroscopic material condense onto particles formed by atmospheric NPF, and that the contribution of highly-hygroscopic material is more important for smaller particles and during the photo- Wu et al 2013, Jung andKawamura 2014). In urban environments, the relative contributions of highlyand less-hygroscopic material to the particle growth seem to vary, in addition to which nucleation mode particles show occasionally an external mixture indicative of two very different sources for these particles (Väkevä et al 2002b, Sakurai et al 2005, Park et al 2009.…”

Effects of chemical composition and mixing state on size‐resolved hygroscopicity and cloud condensation nuclei activity of submicron aerosols at a suburban site in northern Japan in summer

“…The N CN at D dry = 20.2–429 nm ranged from 230 cm −3 to 5440 cm −3 , with an average of 1560 cm −3 . This range is similar to that reported in previous field studies conducted at the same sampling site [ Jung et al , ; Jung and Kawamura , ]. The N CN reached a maximum at the dominant size range in the Aitken mode ( D dry = 30–100 nm).…”

“…The average GF at D dry = 146 nm during P1 (1.37 ± 0.04) was larger than those during P2 (1.24 ± 0.05). The observed GF values in the current study generally agree with those (1.19–1.27) at D dry of 120 nm, obtained at the same site in summer 2011 [ Jung and Kawamura , ]. Other studies reported GF values of 1.20–1.50 at similar values of D dry at a suburban site in Paris [ Jurányi et al , ; Laborde et al , ].…”

A Software Package to Simplify Tikhonov Regularization with Examples for Matrix-Based Inversion of SMPS and HTDMA Data

“…Application of the inversion to a 16-day dataset demonstrates that the thus-obtained growth factor frequency distribution data can reveal significant details about the mixing state of the aerosol. The inverted dataset is suitable as input to carry out common analyses made with growth factor frequency distributions, including characterization of the evolution of aerosol mixing state as a function of time, characterization of changes in growth factor with dry diameter and its relationship to chemical composition, characterization of the growth factor at the mode diameter of particles during modal growth events (Park et al, 2008;Wu et al, 2013;Jung and Kawamura, 2014), decomposition of the hygroscopicity frequency distributions into distinct growth factor classes (Swietlicki et al, 2008), evaluation of the temporal trends of spectral concentration for hygroscopicity-resolved data (Royalty et al, 2017), evaluation of the accuracy of aerosol mass spectrometer measured (organic) mass concentration through hygroscopicity constraints (Jimenez et al, 2016), and inclusion of growth factor frequency distributions to account for mixing state in aerosol hygroscopicity to cloud condensation nuclei closure (Mahish et al, 2018).…”