Roles of RH, aerosol pH and sources in concentrations of secondary inorganic aerosols, during different pollution periods

Gao, Jie; Wei, Yuting; Shi, Guoliang; Yu, Haofei; Zhang, Zhongcheng; Song, Shaojie; Wang, Wei; Liang, Danni; Feng, Yinchang

doi:10.1016/j.atmosenv.2020.117770

Cited by 27 publications

(11 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to SO 2 and oxidants/catalysts, different meteorological conditions and aerosol chemical regimes are key factors in resolving sulfate oxidation mechanisms, such as acidity (pH) and solute strength (ionic strength) . Aerosol acidity is an important reaction condition, which largely regulates the chemistry of atmospheric particles and affects the chemical kinetics of formation processes. − Generally, SO 2 is absorbed into the aqueous phase to form hydrated SO 2 (SO 2 ·H 2 O), bisulfite (HSO 3 – ), and sulfite (SO 3 2– ), which then react with different oxidants/catalysts. Relative proportions of the three products and the relative importance of oxidation pathways strongly depend on pH values .…”

Section: Introductionmentioning

confidence: 99%

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Gao

Shi

Zhang

et al. 2022

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Particulate sulfate is one of the most important components in the atmosphere. The observation of rapid sulfate aerosol production during haze events provoked scientific interest in the multiphase oxidation of SO 2 in aqueous aerosol particles. Diverse oxidation pathways can be enhanced or suppressed under different aerosol acidity levels and high ionic strength conditions of atmospheric aerosol. The importance of ionic strength to sulfate multiphase chemistry has been verified under laboratory conditions, though studies in the actual atmosphere are still limited. By utilizing online observations and developing an improved solute strengthdependent chemical thermodynamics and kinetics model (EF-T&K model, EF is the enhancement factor that represents the effect of ionic strength on an aerosol aqueous-phase reaction), we provided quantitative evidence that the H 2 O 2 pathway was enhanced nearly 100 times and dominated sulfate formation for entire years (66%) in Tianjin (a northern city in China). TMI (oxygen catalyzed by transition-metal ions) (14%) and NO 2 (14%) pathways got the second-highest contributions. Machine learning supported the result that aerosol sulfate production was more affected by the H 2 O 2 pathway. The collaborative effects of atmospheric oxidants and SO 2 on sulfate aerosol production were further investigated using the improved EF-T&K model. Our findings highlight the effectiveness of adopting target oxidant control as a new direction for sustainable mitigation of sulfate, given the already low SO 2 concentrations in China.

show abstract

Section: Introductionmentioning

confidence: 99%

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Gao

Shi

Zhang

et al. 2022

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…These findings are consistent with those of Ding et al (2019), who employed ISORROPIA II to calculate PM 2.5 pH in Beijing for the four seasons and found that the highest PM 2.5 pH appeared on clean days ranging from 2 to 7, followed by polluted and heavily polluted days for all seasons except winter. The analysis in Gao et al (2020) also showed that the range of pH was more confined with aggravation of air pollution.…”

Section: Temporal Variation Of Pm 25 Ph In Haze Eventsmentioning

confidence: 90%

“…For example, He et al (2018) utilized ISORROPIA II to estimate PM 2.5 pH during the Beijing winter haze and found a similarly large pH range of 3.4-7.6 when assuming a metastable aerosol state. Gao et al (2020) calculated aerosol pH in Tianjin using ISORROPIA II and reported that the PM 2.5 pH ranged from −0.08 to 13.75, in which pH varied more severely.…”

Section: Temporal Variation Of Pm 25 Ph In Haze Eventsmentioning

confidence: 99%

Simulations of aerosol pH in China using WRF-Chem (v4.0): sensitivities of aerosol pH and its temporal variations during haze episodes

Ruan

Zhao²,

Zaveri³

et al. 2022

Geosci. Model Dev.

View full text Add to dashboard Cite

Abstract. Aerosol pH is a fundamental property of aerosols in terms of atmospheric chemistry and its impact on air quality, climate, and health. Precise estimation of aerosol pH in chemical transport models (CTMs) is critical for aerosol modeling and thus influences policy development that partially relies on results from model simulations. We report the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) simulated PM2.5 pH over China during a period with heavy haze episodes in Beijing, and explore the sensitivity of the modeled aerosol pH to factors including emissions of nonvolatile cations (NVCs) and NH3, aerosol phase state assumption, and heterogeneous production of sulfate. We find that default WRF-Chem could predict spatial patterns of PM2.5 pH over China similar to other CTMs, but with generally lower pH values, largely due to the underestimation of alkaline species (NVCs and NH3) and the difference in thermodynamic treatments between different models. Increasing NH3 emissions in the model would improve the modeled pH in comparison with offline thermodynamic model calculations of pH constrained by observations. In addition, we find that the aerosol phase state assumption and heterogeneous sulfate production are important in aerosol pH predictions for regions with low relative humidity (RH) and high anthropogenic SO2 emissions, respectively. These factors should be better constrained in model simulations of aerosol pH in the future. Analysis of the modeled temporal trend of PM2.5 pH in Beijing over a haze episode reveals a clear decrease in pH from 5.2 ± 0.9 in a clean period to 3.6 ± 0.5 in a heavily polluted period. The increased acidity under more polluted conditions is largely due to the formation and accumulation of secondary species including sulfuric acid and nitric acid, even though being modified by alkaline species (NVCs, NH3). Our result suggests that NO2 oxidation is unlikely to be important for heterogeneous sulfate production during the Beijing haze as the effective pH for NO2 oxidation of S(IV) is at a higher pH of ∼ 6.

show abstract

“…𝐻 2 𝑂 were shifted to generate more NH4NO3 and (NH4)2SO4 (Nenes et al, 2020;Gao et al, 2020) due to the driving force of more ammonia partitioned in elevated ALWC (NH3+H2O⇌ NH3•H2O, NH3•H2O⇌NH4 + +OH -). Therefore, NH3 and NOx became as the decisive factors on regional atmospheric oxidability in the ammonia-rich regime (Zhai et al, 2021;Fu et al, 2017;Liu et al, 2019;Li et al, 2019).…”

Section: Perturbation Gasesmentioning

confidence: 99%

The shifting of secondary inorganic aerosols formation mechanism during haze aggravation: The decisive role of aerosol liquid water

Xie

Y²,

Tian³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Although many considerable efforts have been done to reveal the driving factors on haze aggravation, however, the roles of aerosol liquid water (ALW) in SIAs formation were mainly focused on the condition of aerosol liquid water content (ALWC)<100 μg/m3. Based on the in-situ high-resolution field observation, this work studied the decisive roles and the shifting of secondary inorganic aerosols formation mechanism during haze aggravation, revealing the different roles of ALWC in a broader scale (~ 500 μg/m3) in nitrate and sulfate formation induced by aqueous chemistry in ammonia-rich atmosphere. The results showed that chemical domains of perturbation gas limiting the generation of secondary particulate matters presented obvious shifts from HNO3 sensitive to HNO3 and NH3 co-sensitive regime with the haze aggravation, indicating the powerful driving effects of ammonia in ammonia-rich atmosphere. When ALWC<75 μg/m3, the sulfate generation was preferentially triggered by the high ammonia utilization, then accelerated by nitrogen oxide oxidation from Clean to Moderate pollution stages, characterizing as NOR<0.3, SOR<0.4, NTR<0.7 and the moral ratio of NO3-:SO42-=2:1. While ALWC>75 μg/m3, aqueous-phase chemistry reaction of SO2 and NH3 in ALW became the prerequisite for SIAs formation driven by Henry’s law in the ammonia-rich atmosphere during Heavy and Serious stages, characterizing as high SOR (0.5–0.9), NOR (0.3–0.5), NTR (>0.7) and the moral ratio of NO3-:SO42-=1:1. A positive feedback of sulfate on nitrate production was also observed in this work. Our results provided the evidence for the response of the transition ALWC with seasonal variability and climate change. It implies the target controlling of haze should not simply focus on SO2 and NO2, more attention should be paid on gaseous precursors (e.g., SO2, NO2, NH3) and aerosol chemical constitution during different haze stages.

show abstract

Roles of RH, aerosol pH and sources in concentrations of secondary inorganic aerosols, during different pollution periods

Cited by 27 publications

References 44 publications

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Simulations of aerosol pH in China using WRF-Chem (v4.0): sensitivities of aerosol pH and its temporal variations during haze episodes

The shifting of secondary inorganic aerosols formation mechanism during haze aggravation: The decisive role of aerosol liquid water

Contact Info

Product

Resources

About

Roles of RH, aerosol pH and sources in concentrations of secondary inorganic aerosols, during different pollution periods

Cited by 27 publications

References 44 publications

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H2O2 Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H2O2 Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Simulations of aerosol pH in China using WRF-Chem (v4.0): sensitivities of aerosol pH and its temporal variations during haze episodes

The shifting of secondary inorganic aerosols formation mechanism during haze aggravation: The decisive role of aerosol liquid water

Contact Info

Product

Resources

About

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H₂O₂ Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze