A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles

Hennigan, Christopher J.; Izumi, J.; Sullivan, A.; Weber, R. J.; Nenes, Athanasios

doi:10.5194/acp-15-2775-2015

Cited by 322 publications

(416 citation statements)

References 77 publications

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“…The above results suggest that the reverse mode calculations (only using aerosol quantity as model inputs) are strongly affected by the ion balance and hence the ionic measurement errors are very likely to lead to unreliable estimates of particle pH (Murphy et al, 2017;Hennigan et al, 2015). 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).…”

Section: Reverse Mode Calculationsmentioning

confidence: 93%

“…The samples with negative ion balance (cations < anions) usually project pH values below 2 (highly acidic), whereas those with positive ion balance (cations > anions) are identified with pH values above 7.4 (neutral or basic). These features have been demonstrated also by Hennigan et al (2015) and Murphy et al (2017) using different observational datasets. Since 25 the inputs to reverse mode calculations include only aerosol phase measurements of ions, the predicted pH values depend largely on the ion balance (Hennigan et al, 2015).…”

Section: Overview Of Measurements and Model Calculationsmentioning

confidence: 96%

“…These features have been demonstrated also by Hennigan et al (2015) and Murphy et al (2017) using different observational datasets. Since 25 the inputs to reverse mode calculations include only aerosol phase measurements of ions, the predicted pH values depend largely on the ion balance (Hennigan et al, 2015). On the other hand, the pH values calculated using the forward mode (both E-AIM and ISORROPIA) range from 3.5 to 5.3 and are not as sensitive to the ion balance.…”

Section: Overview Of Measurements and Model Calculationsmentioning

confidence: 96%

“…(2-5) respectively. Although they are straightforward to calculate, a few recent studies (Murphy et al, 2017;Hennigan et al, 2015;Guo et al, 2016) have demonstrated that the ion balance and equivalent ratio calculated from ambient particle measurements…”

Section: Ion Balance and Equivalent Ratiomentioning

confidence: 99%

“…The direct filter sampling approach is challenged by the nature of hydrogen ion in that its concentration in a solution does not scale in proportion to the level of dilution, and is also subject to sampling errors (Hennigan et al, 2015). A few studies have determined the pH of laboratory generated particles using colorimetry/spectrometry and Raman microspectroscopy (Li and Jang, 2012;Rindelaub et al, 2016;Craig et al, 2017), but such techniques have not been applied to ambient particles partly due to their much more complex chemical and physical 15 properties.…”

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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: Reverse Mode Calculationsmentioning

confidence: 93%

Section: Overview Of Measurements and Model Calculationsmentioning

confidence: 96%

Section: Overview Of Measurements and Model Calculationsmentioning

confidence: 96%

Section: Ion Balance and Equivalent Ratiomentioning

confidence: 99%

mentioning

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

View full text Add to dashboard Cite

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Metals and metalloids in precipitation collected during CHINARE campaign from Shanghai, China, to Zhongshan Station, Antarctica: Spatial variability and source identification

Shi

Teng

et al. 2015

Global Biogeochemical Cycles

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Metals and metalloids in continental precipitation have been widely observed, but the data over open oceans are still very limited. Investigation of metals and metalloids in marine precipitation is of great significance to understand global transport of these elements in the atmosphere and their input fluxes to the oceans. So shipboard sampling of precipitation was conducted during a Chinese National Antarctic Research Expedition campaign from Shanghai, China, to Zhongshan Station, East Antarctica, and 22 samples (including 17 rainfall and 5 snowfall events) were collected and analyzed for concentrations of Pb, Ni, Cr, Cu, Co, Hg, As, Cd, Sb, Se, Zn, Mn, and Ti. Results show that concentrations of both metals and metalloids vary considerably along the cruise, with higher concentrations at coastal sites and lower values on the south Indian Ocean. Although only soluble fractions were determined for elements, concentrations in this study are generally comparable to the reported values of marine rain. Enrichment factor analysis shows that most of metals and metalloids are enriched versus crustal sources, even in the samples collected from remote south Indian Ocean. In addition, metals and metalloids in precipitation are also very enriched above sea-salt abundance, indicating that impacts of sea-salt aerosols on their concentrations are negligible. Main sources of metals and metalloids were explored with the aid of multivariate statistical analyses. The results show that human emissions have far-reaching distribution, which may exert an important influence on the solubility of elements in precipitation. This investigation provides valuable information on spatial variation and possible sources of trace elements in precipitation over the open oceans corresponding to understudied region.

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Airborne measurements of organosulfates over the continental U.S.

et al. 2015

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Organosulfates are important secondary organic aerosol (SOA) components and good tracers for aerosol heterogeneous reactions. However, the knowledge of their spatial distribution, formation conditions, and environmental impact is limited. In this study, we report two organosulfates, an isoprene-derived isoprene epoxydiols (IEPOX) (2,3-epoxy-2-methyl-1,4-butanediol) sulfate and a glycolic acid (GA) sulfate, measured using the NOAA Particle Analysis Laser Mass Spectrometer (PALMS) on board the NASA DC8 aircraft over the continental U.S. during the Deep Convective Clouds and Chemistry Experiment (DC3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). During these campaigns, IEPOX sulfate was estimated to account for 1.4% of submicron aerosol mass (or 2.2% of organic aerosol mass) on average near the ground in the southeast U.S., with lower concentrations in the western U.S. (0.2–0.4%) and at high altitudes (<0.2%). Compared to IEPOX sulfate, GA sulfate was more uniformly distributed, accounting for about 0.5% aerosol mass on average, and may be more abundant globally. A number of other organosulfates were detected; none were as abundant as these two. Ambient measurements confirmed that IEPOX sulfate is formed from isoprene oxidation and is a tracer for isoprene SOA formation. The organic precursors of GA sulfate may include glycolic acid and likely have both biogenic and anthropogenic sources. Higher aerosol acidity as measured by PALMS and relative humidity tend to promote IEPOX sulfate formation, and aerosol acidity largely drives in situ GA sulfate formation at high altitudes. This study suggests that the formation of aerosol organosulfates depends not only on the appropriate organic precursors but also on emissions of anthropogenic sulfur dioxide (SO2), which contributes to aerosol acidity.Key PointsIEPOX sulfate is an isoprene SOA tracer at acidic and low NO conditions Glycolic acid sulfate may be more abundant than IEPOX sulfate globally SO2 impacts IEPOX sulfate by increasing aerosol acidity and water uptake

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A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles

Cited by 322 publications

References 77 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

Metals and metalloids in precipitation collected during CHINARE campaign from Shanghai, China, to Zhongshan Station, Antarctica: Spatial variability and source identification

Airborne measurements of organosulfates over the continental U.S.

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