Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China

Cheng, Yafang; Zheng, Guangjie; Wei, Chao; Mu, Qing; Zheng, Bo; Wang, Zhibin; Gao, Meng; Zhang, Qiang; He, Kebin; Carmichael, Gregory R.; Pöschl, Ulrich; Su, Hang

doi:10.1126/sciadv.1601530

Cited by 1,006 publications

(1,069 citation statements)

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“…The studies using the standard ISORROPIA model with the stable state assumption have predicted unrealistic pH values of around 7 and should be reevaluated He et al, 2017). Previous ISORROPIA calculations using the metastable state assumption 15 obtained average pH values from 4.1 to 5.4 (He et al, 2017;Liu et al, 2017a;Shi et al, 2017;Cheng et al, 2016;Guo et al, 2017b;Tan et al, 2018), agreeing reasonably with our results (an average pH value of 4.6). It is noted that concentrations of Ca 2+ and Mg 2+ were not measured in this study and a sensitivity test suggests that including these crustal cations in thermodynamic calculations would increase predicted pH values by about 0.1 unit (Fig.…”

Section: Summary Of Existing Studiessupporting

confidence: 89%

“…The average reverse mode pH reported by previous studies ranged from -1 to 6.2 (Cheng et al, 2011;He et al, 2012;Tian et al, 2018;Cheng et al, 2016). Our calculations show that the reverse mode pH has a bimodal distribution with peaks between -2 and 2 (highly acidic) and between 7 and 10 (basic), and is very sensitive to errors in ionic measurements (Sect.…”

Section: Summary Of Existing Studiessupporting

confidence: 50%

“…Furthermore, an equivalent ratio of near unity may not indicate that fine particles of winter haze have a pH of around 7 or close to 7 Cheng et al, 2016;Ma et al, 2017). The forward mode calculations 10 (using gas + aerosol quantity as model inputs) are affected much less by the measurement errors and should be used to predict the pH for winter haze particles.…”

Section: Reverse Mode Calculationsmentioning

confidence: 99%

“…(1) The contribution of organics to aerosol water is parameterized usually based on the hygroscopicity parameter κorg (Guo et 10 al., 2015;Cheng et al, 2016):…”

Section: Assumptions and Limitations Of Thermodynamic Modelingmentioning

confidence: 99%

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Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Song¹,

Gao²,

Xu³

et al. 2018

Preprint

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Abstract. pH is an important property of aerosol particles but is difficult to measure directly. Several studies have estimated the pH values for fine particles in North China winter haze using thermodynamic models (i.e., E-AIM and ISORROPIA) and ambient measurements. The reported pH values differ widely, ranging from close to 0 (highly acidic) to as high as 7 (neutral).In order to understand the reason for this discrepancy, we calculated pH values using these models with different assumptions 25 with regard to model inputs and particle phase states. We find that the large discrepancy is due primarily to differences in the model assumptions adopted in previous studies. Calculations using only aerosol phase composition as inputs (i.e., reverse mode) are sensitive to the measurement errors of ionic species and inferred pH values exhibit a bimodal distribution with peaks between −2 and 2 and between 7 and 10. Calculations using total (gas plus aerosol phase) measurements as inputs (i.e., forward mode) are affected much less by the measurement errors, and results are thus superior to those obtained from the reverse mode 30 calculations. Forward mode calculations in this and previous studies collectively indicate a moderately acidic condition (pH from about 4 to about 5) for fine particles in North China winter haze, indicating further that ammonia plays an important role in determining this property. The differences in pH predicted by the forward mode E-AIM and ISORROPIA calculations may be attributed mainly to differences in estimates of activity coefficients for hydrogen ions. The phase state assumed, which can be either stable (solid plus liquid) or metastable (only liquid), does not significantly impact pH predictions of ISORROPIA. 35Atmos. Chem. Phys. Discuss., https://doi

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Section: Summary Of Existing Studiessupporting

confidence: 89%

Section: Summary Of Existing Studiessupporting

confidence: 50%

Section: Reverse Mode Calculationsmentioning

confidence: 99%

“…(1) The contribution of organics to aerosol water is parameterized usually based on the hygroscopicity parameter κorg (Guo et 10 al., 2015;Cheng et al, 2016):…”

Section: Assumptions and Limitations Of Thermodynamic Modelingmentioning

confidence: 99%

See 2 more Smart Citations

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Song¹,

Gao²,

Xu³

et al. 2018

Preprint

Self Cite

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show abstract

“…However, there is still a large uncertainty remained for the underestimation of secondary aerosols during the heavy haze periods in eastern China. Because secondary aerosols have a large portion in the chemical composition of the total aerosols during haze periods, and the formation of SA amplifies the magnitude of the short-term variation of PM 2.5 concentrations, and future study is needed to better understand this problem [15,16].…”

Section: Effect Of Chemical Reactionsmentioning

confidence: 99%

Understanding Variability of Haze in Eastern China

Tie¹,

Cao²

2017

J Fundam Renewable Energy Appl

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Fine particle pH during severe haze episodes in northern China

Liu

Song

Zhou

et al. 2017

Geophysical Research Letters

246

207

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Aerosol acidity plays an important role in atmospheric chemistry. China emits large amounts of SO2, NOx, and NH3 into the atmosphere, but aerosol acidity is poorly characterized. In this study, simultaneous 1 h measurements of particulate and gaseous compositions along with the ISORROPIA‐II thermodynamic equilibrium model were used to study aerosol acidity during severe haze episodes in northern China. The summed concentration of sulfate, nitrate, and ammonium was 135 ± 51 μg/m3 with a maximum of 250 μg/m3, and the gas‐phase NH3 mixing ratio was 22 ± 9 ppb. Fine particles were moderately acidic, with a pH range of 3.0–4.9 and an average of 4.2, which was higher than those in the United States and Europe. Excess NH3 and high aerosol water content are responsible for the relatively lower aerosol acidity. These results suggest that the new pathways for sulfate production in China proposed by recent studies should be revisited.

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Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China

Abstract: Multiphase chemistry of NO2 and alkaline matter in aerosol water explains rapid sulfate formation and severe haze in China.

Cited by 1,006 publications

References 131 publications

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Understanding Variability of Haze in Eastern China

Fine particle pH during severe haze episodes in northern China

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