Effect of ammonia on fine-particle pH in agricultural regions of China: comparison between urban and rural sites

Wang, Shenbo; Wang, Lingling; Li, Yuqing; Wang, Chen; Wang, Weisi; Yin, Shasha; Zhang, Ruiqin

doi:10.5194/acp-20-2719-2020

Cited by 35 publications

(20 citation statements)

References 64 publications

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“…Notably, the pH in spring (4.2 ± 0.7) was similar to the value found in urban Beijing (4.4 ± 1.2) in the same season. In comparison, the pH values in autumn and winter were 0.5 to 1.1 lower than those found in urban areas of northern China, such as 4.3 ± 0.8 in autumn in Beijing,2) in winter in Zhengzhou and 4.8 (3.9-5.9) in winter in Anyang (Ding et al, 2019;Wang et al, 2020). The higher LWC in urban areas may be one of the important reasons for its slightly lower acidity in autumn and winter compared to that in background areas in northern China.…”

Section: Seasonality Of Aerosol Aciditycontrasting

confidence: 54%

“…This difference of MO-OOA formation between urban and background sites in the NCP was mainly due to the higher atmospheric oxidation capability in the background atmosphere than in the urban atmosphere in summer. A previous study showed that O x concentration at the background sites was 30 % higher than that at the urban site during summertime (Wang et al, 2013). Furthermore, increases in LO-OOA and MO-OOA as functions of O x were clearly associated with the increases in wind speed in Xinglong, which were more significant in summer than in other seasons.…”

Section: Evolution and Formation Of Soamentioning

confidence: 76%

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Seasonal variations in the highly time-resolved aerosol composition, sources and chemical processes of background submicron particles in the North China Plain

Cao

Gao

et al. 2021

Atmos. Chem. Phys.

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Abstract. For the first time in the North China Plain (NCP) region, we investigated the seasonal variations in submicron particles (NR-PM1) and their chemical composition at a background mountainous site of Xinglong using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer. The average concentration of NR-PM1 was highest in autumn (15.1 µg m−3) and lowest in summer (12.4 µg m−3), with a greater abundance of nitrate in spring (34 %), winter (31 %) and autumn (34 %) and elevated organics (40 %) and sulfate (38 %) in summer. PM1 in Xinglong showed higher acidity in summer and moderate acidity in spring, autumn and winter, with average pH values of 2.7±0.6, 4.2±0.7, 3.5±0.5 and 3.7±0.6, respectively, which is higher than those estimated in the United States and Europe. The size distribution of all PM1 species showed a consistent accumulation mode peaking at approximately 600–800 nm (dva), indicating a highly aged and internally mixed nature of the background aerosols, which was further supported by the source appointment results using positive matrix factorization and multilinear engine analysis. Significant contributions of aged secondary organic aerosol (SOA) in organic aerosol (OA) were resolved in all seasons (>77 %), especially in summer. The oxidation state and the process of evolution of OAs in the four seasons were further investigated, and an enhanced carbon oxidation state (−0.45–0.10) and O/C (0.54–0.75) and OM/OC (1.86–2.13) ratios – compared with urban studies – were observed, with the highest oxidation state appearing in summer, likely because of the relatively stronger photochemical processing that dominated the formation processes of both less oxidized OA (LO-OOA) and more oxidized OA (MO-OOA). Aqueous-phase processing also contributed to the SOA formation and prevailed in winter, with the share to MO-OOA being more important than that to LO-OOA. In addition, regional transport also played an important role in the variations in SOA. Especially in summer, continuous increases in SOA concentration as a function of odd oxygen (Ox=O3+NO2) were found to be associated with the increases in wind speed. Furthermore, backward trajectory analysis showed that higher concentrations of submicron particles were associated with air masses transported short distances from the southern regions in all four seasons, while long-range transport from Inner Mongolia (western and northern regions) also contributed to summertime particulate pollution in the background areas of the NCP. Our results illustrate that the background particles in the NCP are influenced significantly by aging processes and regional transport, and the increased contribution of aerosol nitrate highlights how regional reductions in nitrogen oxide emissions are critical for remedying occurrence of nitrate-dominated haze events over the NCP.

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Section: Seasonality Of Aerosol Aciditycontrasting

confidence: 54%

Section: Evolution and Formation Of Soamentioning

confidence: 76%

Seasonal variations in the highly time-resolved aerosol composition, sources and chemical processes of background submicron particles in the North China Plain

Cao

Gao

et al. 2021

Atmos. Chem. Phys.

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“…Higher PM 2.5 pH values (around 2 to 3) were reported for Los Angeles during the CalNex campaign due to higher aerosol water concentrations, which was a result of higher total NO 3 − concentrations and NO 3 − -HNO 3 partitioning [5]. Locations close to areas with intensive agricultural activities that emitted high levels of NH 3 (e.g., parts of mainland China and Europe) had fine pH values as high as 6 [14,36,37]. Higher fine aerosol pH values (around 4 to 6) were reported for urban areas impacted by sea salt (e.g., San Paulo, Hawaii) and dust (e.g., Inner Mongolia, Po Valley) due to the neutralizing effect of NVCs [14,[38][39][40][41].…”

Section: Introductionmentioning

confidence: 81%

Fine Aerosol Acidity and Water during Summer in the Eastern North Atlantic

et al. 2021

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Aerosol pH governs many important atmospheric processes that occur in the marine boundary layer, including regulating halogen and sulfur chemistries, and nutrient fertilization of surface ocean waters. In this study, we investigated the acidity of PM1 over the eastern North Atlantic during the Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) aircraft campaign. The ISORROPIA-II thermodynamic model was used to predict PM1 pH and water. We first investigated the sensitivities of PM1 pH and water predictions to gas-phase NH3 and HNO3 concentrations. Our sensitivity analysis indicated that even though NH3 and HNO3 were present at very low concentrations in the eastern North Atlantic during the campaign, PM1 pH calculations can still be sensitive to NH3 concentrations. Specifically, NH3 was needed to constrain the pH of populations of PM1 that had low mass concentrations of NH4+ and non-volatile cations (NVCs). We next assumed that gas-phase NH3 and HNO3 concentrations during the campaign were 0.15 and 0.09 µg m−3, respectively, based on previous measurements conducted in the eastern North Atlantic. Using the assumption that PM1 were internally mixed (i.e., bulk PM1), we determined that PM1 pH ranged from 0.3–8.6, with a mean pH of 5.0 ± 2.3. The pH depended on both and . was controlled primarily by the NVCs/SO42− molar ratio, while was controlled by the SO42− mass concentration and RH. Changes in pH with altitude were driven primarily by changes in SO42−. Since aerosols in marine atmospheres are rarely internally mixed, the scenario where non-sea salt species and sea-salt species were present in two separate aerosol modes in the PM1 (i.e., completely externally mixed) was also considered. Smaller pH values were predicted for the aerosol mode comprised only of non-sea salt species compared to the bulk PM1 (difference of around 1 unit on average). This was due to the exclusion of sea-salt species (especially hygroscopic alkaline NVCs) in this aerosol mode, which led to increases in values and decreases in values. This result demonstrated that assumptions of aerosol mixing states can impact aerosol pH predictions substantially, which will have important implications for evaluating the nature and magnitude of pH-dependent atmospheric processes that occur in the marine boundary layer.

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“…Sulfate, an important component of atmospheric secondary inorganic aerosols, plays an important role in the formation of haze (Wang et al, 2014;Yue et al, 2019). The correlation coefficient (R 2 ) between the measured IC-SO 2− 4 and ACSM-SO 2− 4 was only 0.26 for IAP with a slope of 0.54.…”

Section: Comparison With Tof-acsm Datamentioning

confidence: 99%

An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography: implications for aerosol pH estimate

Song

Harrison

et al. 2020

Atmos. Meas. Tech.

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Abstract. Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl−, SO42-, NO3-, NH4+ and K+. However, F−, Mg2+ and Ca2+ were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO42-, NO3- and NH4+ generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl− from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl−, SO42-, NO3-, NH4+ and K+ across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl−, SO42-, NO3-, NH4+ and K+ decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE / CE) and ion balance (anions–cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent.

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Effect of ammonia on fine-particle pH in agricultural regions of China: comparison between urban and rural sites

Cited by 35 publications

References 64 publications

Seasonal variations in the highly time-resolved aerosol composition, sources and chemical processes of background submicron particles in the North China Plain

Seasonal variations in the highly time-resolved aerosol composition, sources and chemical processes of background submicron particles in the North China Plain

Fine Aerosol Acidity and Water during Summer in the Eastern North Atlantic

An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography: implications for aerosol pH estimate

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