Effects of Water-soluble Organic Carbon on Aerosol pH

Abstract. Water soluble organic carbon (WSOC) is a ubiquitous and significant fraction of fine particulate matter. Despite advances in aerosol thermodynamic equilibrium models, there is limited understanding on the comprehensive impacts of WSOC on aerosol acidity (pH). We address this limitation by studying submicron aerosol that represent the two extremes in acidity levels found in the atmosphere: strongly acidic aerosol from Baltimore, MD, and weakly acidic conditions characteristic of Beijing, China. These cases are then used to construct mixed inorganic/organic single-phase aqueous particles, and thermodynamically analyzed by the E-AIM and ISORROPIA models (in combination with activity coefficient model AIOMFAC) to evaluate the effects of WSOC on the H+ ion activity coefficients (γH+) and activity (pH). We find that addition of organic acids and non-acid organic species concurrently increases γH+ and aerosol liquid water. When allowed to modulate pH, these effects mostly offset each other, giving pH changes of

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Effects of water-soluble organic carbon on aerosol pH

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-14607-2019 ◽

2019 ◽

Vol 19 (23) ◽

pp. 14607-14620 ◽

Cited By ~ 6

Author(s):

Michael A. Battaglia Jr. ◽

Rodney J. Weber ◽

Athanasios Nenes ◽

Christopher J. Hennigan

Keyword(s):

Organic Carbon ◽

Activity Coefficient ◽

Organic Acids ◽

Organic Acid ◽

Fine Particulate Matter ◽

Water Soluble ◽

Ph Changes ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon ◽

Acidic Conditions

Abstract. Water-soluble organic carbon (WSOC) is a ubiquitous and significant fraction of fine particulate matter. Despite advances in aerosol thermodynamic equilibrium models, there is limited understanding on the comprehensive impacts of WSOC on aerosol acidity (pH). We address this limitation by studying submicron aerosols that represent the two extremes in acidity levels found in the atmosphere: strongly acidic aerosol from Baltimore, MD, and weakly acidic conditions characteristic of Beijing, China. These cases are then used to construct mixed inorganic–organic single-phase aqueous particles and thermodynamically analyzed by the Extended Aerosol Inorganics Model (E-AIM) and ISORROPIA models in combination with activity coefficient model AIOMFAC (Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficient) to evaluate the effects of WSOC on the H+ ion activity coefficients (γH+) and activity (pH). We find that addition of organic acids and nonacid organic species concurrently increases γH+ and aerosol liquid water. Under the highly acidic conditions typical of the eastern US (inorganic-only pH ∼1), these effects mostly offset each other, giving pH changes of < 0.5 pH units even at organic aerosol dry mass fractions in excess of 60 %. Under conditions with weaker acidity typical of Beijing (inorganic-only pH ∼4.5), the nonacidic WSOC compounds had similarly minor effects on aerosol pH, but organic acids imparted the largest changes in pH compared to the inorganic-only simulations. Organic acids affect pH in the order of their pKa values (oxalic acid > malonic acid > glutaric acid). Although the inorganic-only pH was above the pKa value of all three organic acids investigated, pH changes in excess of 1 pH unit were only observed at unrealistic organic acid levels (aerosol organic acid concentrations > 35 µg m−3) in Beijing. The model simulations were run at 70 %, 80 %, and 90 % relative humidity (RH) levels and the effect of WSOC was inversely related to RH. At 90 % RH, WSOC altered aerosol pH by up to ∼0.2 pH units, though the effect was up to ∼0.6 pH units at 70 % RH. The somewhat offsetting nature of these effects suggests that aerosol pH is sufficiently constrained by the inorganic constituents alone under conditions where liquid–liquid phase separation is not anticipated to occur.

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Effects of Water-soluble Organic Carbon on Aerosol pH

10.5194/egusphere-egu2020-2009 ◽

2020 ◽

Author(s):

Christopher Hennigan ◽

Michael Battaglia, Jr. ◽

Rodney Weber ◽

Athanasios Nenes

Keyword(s):

Organic Carbon ◽

Organic Acids ◽

Organic Acid ◽

Fine Particulate Matter ◽

Dry Mass ◽

Water Soluble ◽

Ph Changes ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon ◽

Acidic Conditions

Water soluble organic carbon (WSOC) is a ubiquitous and significant fraction of fine particulate matter.&#160; Despite advances in aerosol thermodynamic equilibrium models, there is limited understanding on the comprehensive impacts of WSOC on aerosol acidity (pH).&#160; We address this limitation by studying submicron aerosol that represent the two extremes in acidity levels found in the atmosphere: strongly acidic aerosol from Baltimore, MD, and weakly acidic conditions characteristic of Beijing, China. These cases are then used to construct mixed inorganic/organic single-phase aqueous particles, and thermodynamically analyzed by the E-AIM and ISORROPIA models in combination with activity coefficient model AIOMFAC to evaluate the effects of WSOC on the H+ ion activity coefficients (&#947;H+) and activity (pH).&#160; We find that addition of organic acids and non-acid organic species concurrently increases &#947;H+ and aerosol liquid water.&#160; Under the highly acidic conditions typical of the eastern U.S. (inorganic-only pH ~1), these effects mostly offset each other, giving pH changes of < 0.5 pH units even at organic aerosol dry mass fractions in excess of 60%.&#160; Under conditions with weaker acidity typical of Beijing (inorganic-only pH ~4.5), the non-acidic WSOC compounds had similarly minor effects on aerosol pH, but organic acids imparted the largest changes in pH compared to the inorganic-only simulations.&#160; Organic acids affect pH in the order of their pKa values (oxalic acid > malonic acid > glutaric acid).&#160; Although the inorganic-only pH was above the pKa value of all three organic acids investigated, pH changes in excess of 1 pH unit were only observed at unrealistic organic acid levels (aerosol organic acid concentrations > 35 &#181;g m-3) in Beijing.&#160; The model simulations were run at 70%, 80%, and 90% relative humidity (RH) levels and the effect of WSOC was inversely related to RH.&#160; At 90% RH, WSOC altered aerosol pH by up to ~0.2 pH units, though the effect was up to ~0.6 pH units at 70% RH.&#160; The somewhat offsetting nature of these effects suggests that aerosol pH is sufficiently constrained by the inorganic constituents alone under conditions where liquid-liquid phase separation is not anticipated to occur.

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Resolving sources of water-soluble organic carbon in fine particulate matter measured at an urban site during winter

Environmental Science Processes & Impacts ◽

10.1039/c2em30730h ◽

2013 ◽

Vol 15 (2) ◽

pp. 524 ◽

Cited By ~ 11

Author(s):

Sung Yong Cho ◽

Seung Shik Park

Keyword(s):

Particulate Matter ◽

Organic Carbon ◽

Fine Particulate Matter ◽

Water Soluble ◽

Urban Site ◽

Fine Particulate ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

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Insights into the Origin of Water Soluble Organic Carbon in Atmospheric Fine Particulate Matter

Aerosol Science and Technology ◽

10.1080/02786820903188701 ◽

2009 ◽

Vol 43 (11) ◽

pp. 1099-1107 ◽

Cited By ~ 54

Author(s):

David C. Snyder ◽

Andrew P. Rutter ◽

Ryan Collins ◽

Chris Worley ◽

James J. Schauer

Keyword(s):

Particulate Matter ◽

Organic Carbon ◽

Fine Particulate Matter ◽

Water Soluble ◽

Fine Particulate ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

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Tracking sources and behaviors of water-soluble organic carbon in fine particulate matter measured at an urban site in Korea

Atmospheric Environment ◽

10.1016/j.atmosenv.2010.09.045 ◽

2011 ◽

Vol 45 (1) ◽

pp. 60-72 ◽

Cited By ~ 51

Author(s):

Seung Shik Park ◽

Sung Y. Cho

Keyword(s):

Particulate Matter ◽

Organic Carbon ◽

Fine Particulate Matter ◽

Water Soluble ◽

Urban Site ◽

Fine Particulate ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon ◽

And Behaviors

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Composition of water-soluble organic carbon in non-urban atmospheric aerosol collected at the Storm Peak Laboratory

Environmental Chemistry ◽

10.1071/en13079 ◽

2013 ◽

Vol 10 (5) ◽

pp. 370 ◽

Cited By ~ 14

Author(s):

Vera Samburova ◽

A. Gannet Hallar ◽

Lynn R. Mazzoleni ◽

Parichehr Saranjampour ◽

Douglas Lowenthal ◽

...

Keyword(s):

Molecular Weight ◽

Organic Carbon ◽

Negative Ions ◽

Water Soluble ◽

Organic Fraction ◽

Sugar Alcohols ◽

Organic Species ◽

Soluble Organic Fraction ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

Environmental context The organic fraction of atmospheric aerosols is a complex mixture of thousands of species, which play an important role in many atmospheric processes, such as absorbing and scattering solar radiation. We analysed the water-soluble organic fraction of ambient aerosol samples, and quantified over 45 carboxylic acids, sugars, sugar anhydrides and sugar alcohols. The presence of fairly high concentrations of sugars and sugar-alcohols suggests a significant biological input (e.g. pollen, fungi and bacteria) to the water-soluble organic fraction of non-urban aerosols. Abstract Water-soluble organic constituents of PM2.5 aerosol (particulate matter with an aerodynamic diameter ≤2.5µm) have not been well characterised so far. The goal of this work was to perform quantitative analysis of individual water-soluble organic species in aerosol samples collected in July of 2010 at the Storm Peak Laboratory (3210m above sea level) located in the Colorado Park Range (Steamboat Springs, CO, USA). Aqueous extracts were combined into six composites and analysed for organic carbon (OC), water-soluble organic carbon (WSOC), water-insoluble OC, inorganic ions, organic acids, lignin derivatives, sugar-alcohols, sugars and sugar-anhydrates. Analysis of higher molecular weight water-soluble organics was done using ultrahigh resolution mass spectrometry. Approximately 2400 positive and 4000 negative ions were detected and assigned to monoisotopic molecular formulae in the mass range of 100–800Da. The higher number of negative ions reflects a predominant presence of highly oxidised organic compounds. Individual identified organic species represented up to 30% of the water-soluble organic mass (WSOM). The WSOM fractions of the low molecular weight organic acids, sugars and sugar alcohols were 3–12%, 1.0–16% and 0.4–1.9%. Significant amounts of arabitol, mannitol and oxalic acid are most likely associated with airborne fungal spores and conidia that were observed on the filters using high resolution electron microscopy. Overall, higher concentrations of sugars (glucose, sucrose, fructose etc.) in comparison with biomass burning tracer levoglucosan indicate that a significant mass fraction of WSOC is related to airborne biological species.

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Significant Contribution of Primary Sources to Water-Soluble Organic Carbon During Spring in Beijing, China

Atmosphere ◽

10.3390/atmos11040395 ◽

2020 ◽

Vol 11 (4) ◽

pp. 395

Author(s):

Yali Jin ◽

Caiqing Yan ◽

Amy P. Sullivan ◽

Yue Liu ◽

Xinming Wang ◽

...

Keyword(s):

Organic Carbon ◽

Significant Contribution ◽

Fine Particulate Matter ◽

Water Soluble ◽

Primary Sources ◽

Chemical Components ◽

Formation Mechanisms ◽

Secondary Source ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

Despite the significant role water-soluble organic carbon (WSOC) plays in climate and human health, sources and formation mechanisms of atmospheric WSOC are still unclear; especially in some heavily polluted areas. In this study, near real-time WSOC measurement was conducted in Beijing for the first time with a particle-into-liquid-sampler coupled to a total organic carbon analyzer during the springtime, together with collocated online measurements of other chemical components in fine particulate matter with a 1 h time resolution, including elemental carbon (EC), organic carbon (OC), multiple metals, and water-soluble ions. Good correlations of WSOC with primary OC, as well as carbon monoxide, indicated that major sources of WSOC were primary instead of secondary during the study period. The positive matrix factorization model-based source apportionment results quantified that 68 ± 19% of WSOC could be attributed to primary sources, with predominant contributions by biomass burning during the study period. This finding was further confirmed by the estimate with the modified EC-tracer method, suggesting significant contribution of primary sources to WSOC. However, the relative contribution of secondary source to WSOC increased during haze episodes. The WSOC/OC ratio exhibited similar diurnal distributions with O3 and correlated well with secondary WSOC, suggesting that the WSOC/OC ratio might act as an indicator of secondary formation when WSOC was dominated by primary sources. This study provided evidence that primary sources could be major sources of WSOC in some polluted megacities, such as Beijing. From this study, it can be seen that WSOC cannot be simply used as a surrogate of secondary organic aerosol, and its major sources could vary by season and location.

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