Supplementary material to "Characterization of aerosol hygroscopicity, mixing state, and CCN activity at a suburban site in the central North China Plain"

Abstract. This study investigates aerosol hygroscopicity, mixing state, and cloud condensation nucleation as part of the Atmosphere–Aerosol–Boundary Layer–Cloud Interaction Joint Experiment performed in the summer of 2016 at Xingtai (XT), a suburban site located in the center of the North China Plain (NCP). In general, the probability density function (PDF) of the hygroscopicity parameter (κ) for 40–200 nm particles had a unimodal distribution, and mean κ-PDF patterns for different sizes were similar, suggesting that the particles were highly aged and internally mixed because of strong photochemical reactions. The κ calculated from the hygroscopic growth factor in the daytime and at night suggests that photochemical reactions largely enhanced the aerosol hygroscopicity. This effect became weaker as the particle size increased. In addition, the aerosol hygroscopicity was much larger at XT than at other sites in the NCP. This is because new particle formation takes place much more frequently in the central NCP, which is heavily polluted from industrial activities, than elsewhere in the region. The evolution of the planetary boundary layer played a dominant role in dictating aerosol mass concentration. Particle size was the most important factor influencing the ability of aerosols to activate, whereas the effect of chemical composition was secondary, especially when supersaturation was high. Using a fixed value of κ=0.31 to calculate the cloud condensation nuclei number concentration in this region suffices.

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Characterization of aerosol hygroscopicity, mixing state, and CCN activity at a suburban site in the central North China Plain

10.5194/acp-2017-1100 ◽

2018 ◽

Author(s):

Yuying Wang ◽

Zhanqing Li ◽

Yingjie Zhang ◽

Wei Du ◽

Fang Zhang ◽

...

Keyword(s):

Boundary Layer ◽

Particle Size ◽

Chemical Composition ◽

North China Plain ◽

North China ◽

Particle Formation ◽

Photochemical Reactions ◽

Mixing State ◽

Aerosol Hygroscopicity ◽

Suburban Site

Abstract. Aerosol hygroscopicity, mixing state and CCN activity were investigated as a part of the Atmosphere-Aerosol-Boundary Layer-Cloud (A2BC) Interaction Joint Experiment carried out at Xingtai (XT), a suburban site in the center of the North China Plain (NCP). In general, the probability density function of the hygroscopicity parameter (κ-PDF) for 40–200 nm particles had a unimodal distribution and mean κ-PDF patterns for different sizes were similar, suggesting that the particles were highly aged and internally mixed because of strong photochemical reactions. The κ calculated from the hygroscopic growth factor in the daytime and at nighttime showed that photochemical reactions largely enhanced the aerosol hygroscopicity, and the effect became weaker as the particle size increased. In addition, the aerosol hygroscopicity was much larger at XT than at sites in the northern part of the NCP, illustrating that the hygroscopicity of particles varies due to different emissions and chemical processes in the NCP. Measurement results also showed that new particle formation events occurred frequently at XT, one of the most polluted city in China. The evolution of the planetary boundary layer played a dominant role in aerosol mass concentration changes while particle formation and growth had a greater influence on the variation in aerosol number concentrations. Particle size was the most important factor influencing the ability of aerosols to activate, especially at higher levels of supersaturation (SS). The cloud condensation nuclei (CCN) number concentration (NCCN) derived from chemical composition was highly correlated with the measured NCCN (R2 ≥ 0.85), but was generally overestimated due to measurement uncertainties. The effect of chemical composition on NCCN was weaker relative to the particle size. NCCN sensitivity tests showed that the impact of chemical composition on NCCN became weaker with increasing SS, suggesting that chemical composition played a less role in NCCN estimations at higher SS levels. A good proxy for the chemical comical composition (κ = 0.31) was found, which can simplify the calculation of NCCN on models.

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Supplementary material to "Measurement report: Evaluation of sources and mixing state of black carbon aerosol under the background of emission reduction in the North China Plain: implications for radiative effect"

10.5194/acp-2020-570-supplement ◽

2020 ◽

Author(s):

Qiyuan Wang ◽

Li Li ◽

Jiamao Zhou ◽

Jianhuai Ye ◽

Wenting Dai ◽

...

Keyword(s):

Black Carbon ◽

Emission Reduction ◽

North China Plain ◽

North China ◽

Radiative Effect ◽

Mixing State ◽

The North ◽

The North China Plain ◽

Supplementary Material ◽

Black Carbon Aerosol

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Secondary aerosol formation alters CCN activity in the North China Plain

10.5194/egusphere-egu21-11204 ◽

2021 ◽

Author(s):

Jiangchuan Tao ◽

Ye Kuang ◽

Nan Ma ◽

Juan Hong ◽

Yele Sun ◽

...

Keyword(s):

Particle Size ◽

North China Plain ◽

North China ◽

Particle Mass ◽

Mixing State ◽

Particle Size Range ◽

The North ◽

The North China Plain ◽

Aerosol Mixing State ◽

Ccn Activity

The formation of secondary aerosols (SA, including secondary organic and inorganic aerosols, SOA and SIA) were the dominant sources of aerosol particles in the North China Plain and can result in significant variations of particle size distribution (PNSD) and hygroscopicity. Earlier studies have shown that the mechanism of SA formation can be affected by relative humidity (RH), and thus has different influences on the aerosol hygroscopicity and PNSD under different RH conditions. Based on the measurements of size-resolved particle activation ratio (SPAR), hygroscopicity distribution (GF-PDF), PM2.5 chemical composition, PNSD, meteorology and gaseous pollutants in a recent field campaign McFAN (Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain) conducted at Gucheng site from November 16th to December 16th in 2018, the influences of SA formation on CCN activity and CCN number concentration (NCCN) calculation at super-saturation of 0.05% under different RH conditions were studied. Measurements showed that during daytime, SA formation could lead to a significant increase in NCCN and a strong diurnal variation in CCN activity. During periods with daytime minimum RH exceeding 50% (high RH conditions), SA formation significantly contributed to the particle mass/size changes in wide particle size range of 150 nm to 1000 nm, and led to an increase of NCCN in particle size range of 200 nm to 300 nm, while increases in particle mass concentration mainly occurred within particle sizes larger than 300nm. During periods with daytime minimum RH below 30% in (low RH conditions), SA formation mainly contributed to the particle mass/size and NCCN changes in particle sizes smaller than 300 nm. As a result, under the same amount SA formation induced mass increase, the increase of NCCN was weaker under high RH conditions, while stronger under low RH conditions. Moreover, the diurnal variations of aerosol mixing state (inferred from CCN measurements) due to SA formation was different under different RH conditions. If the variations of the aerosol mixing state were not considered, estimations of NCCN would bear significant deviations. By applying aerosol mixing state estimated by number fraction of hygroscopic particles from measurements of particle hygroscopicity or mass fraction of SA from measurements of particle chemical compositions, NCCN calculation can be largely improved with relative deviation within 30%. This study improves the understanding of the impact of SA formation on CCN activity and NCCN calculation, which is of great significance for improving parameterization of SA formation in aerosol models and CCN calculation in climate models.

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