A new method to quantify mineral dust and other aerosol species from aircraft platforms using single-particle mass spectrometry

Froyd, K. D.; Murphy, D. M.; Brock, C. A.; Campuzano‐Jost, Pedro; Dibb, Jack E.; Jimenez, José L.; Kupc, Agnieszka; Middlebrook, A. M.; Schill, G. P.; Thornhill, K. L.; Williamson, Christina; Wilson, J. C.; Ziemba, L. D.

doi:10.5194/amt-12-6209-2019

Cited by 76 publications

(73 citation statements)

References 148 publications

(201 reference statements)

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“…3.2), with f (BB) = 1 taken as BC and OA being of pure BB air mass origin and f (BB) = 0 exclusively from a non-biomass burning source. By using the POA / BC ratio at the source regions after most evaporation but before POA chemical degradation evaporation has taken place, we implicitly assume POA to be chemically inert, while in reality it can slowly be lost to the gas phase by heterogeneous chemistry (e.g., George and Abbatt, 2010;Palm et al, 2018). Thus, the observationbased method provides an upper limit to the fraction of POA.…”

Section: Contribution Of Primary Vs Secondary Oamentioning

confidence: 99%

Characterization of organic aerosol across the global remote troposphere: a comparison of ATom measurements and global chemistry models

et al. 2020

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Abstract. The spatial distribution and properties of submicron organic aerosol (OA) are among the key sources of uncertainty in our understanding of aerosol effects on climate. Uncertainties are particularly large over remote regions of the free troposphere and Southern Ocean, where very few data have been available and where OA predictions from AeroCom Phase II global models span 2 to 3 orders of magnitude, greatly exceeding the model spread over source regions. The (nearly) pole-to-pole vertical distribution of non-refractory aerosols was measured with an aerosol mass spectrometer onboard the NASA DC-8 aircraft as part of the Atmospheric Tomography (ATom) mission during the Northern Hemisphere summer (August 2016) and winter (February 2017). This study presents the first extensive characterization of OA mass concentrations and their level of oxidation in the remote atmosphere. OA and sulfate are the major contributors by mass to submicron aerosols in the remote troposphere, together with sea salt in the marine boundary layer. Sulfate was dominant in the lower stratosphere. OA concentrations have a strong seasonal and zonal variability, with the highest levels measured in the lower troposphere in the summer and over the regions influenced by biomass burning from Africa (up to 10 µg sm−3). Lower concentrations (∼0.1–0.3 µg sm−3) are observed in the northern middle and high latitudes and very low concentrations (<0.1 µg sm−3) in the southern middle and high latitudes. The ATom dataset is used to evaluate predictions of eight current global chemistry models that implement a variety of commonly used representations of OA sources and chemistry, as well as of the AeroCom-II ensemble. The current model ensemble captures the average vertical and spatial distribution of measured OA concentrations, and the spread of the individual models remains within a factor of 5. These results are significantly improved over the AeroCom-II model ensemble, which shows large overestimations over these regions. However, some of the improved agreement with observations occurs for the wrong reasons, as models have the tendency to greatly overestimate the primary OA fraction and underestimate the secondary fraction. Measured OA in the remote free troposphere is highly oxygenated, with organic aerosol to organic carbon (OA ∕ OC) ratios of ∼2.2–2.8, and is 30 %–60 % more oxygenated than in current models, which can lead to significant errors in OA concentrations. The model–measurement comparisons presented here support the concept of a more dynamic OA system as proposed by Hodzic et al. (2016), with enhanced removal of primary OA and a stronger production of secondary OA in global models needed to provide better agreement with observations.

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Section: Contribution Of Primary Vs Secondary Oamentioning

confidence: 99%

Characterization of organic aerosol across the global remote troposphere: a comparison of ATom measurements and global chemistry models

et al. 2020

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“…We have applied the 1D version of the Chen method to each field campaign after filtering it by the AN f and pH constraints for regime II. OS f is nominally slightly greater than zero for ATom-1 (OS f ~ 3%, greater than the 0.3% estimate in regime II from PALMS (for ATom-1 and ATom-2, estimated by only considering the sulfate moiety from the IEPOX or glycolic acid sulfate (GAS) OS, neither of which was detected in the supermicron aerosol (Froyd et al, 2009(Froyd et al, , 2019Liao et al, 2015) ) but still small, (see Fig. S7) much less than zero for ATom-2 (OS f ~ -23%) and KORUS-AQ (OS f ~ -26%).…”

Section: Specification Of Aerosol Chemical Regimes For Feasibility Ofmentioning

confidence: 74%

Aerosol pH Indicator and Organosulfate Detectability from Aerosol Mass Spectrometry Measurements

Schueneman¹,

Nault²,

Campuzano‐Jost³

et al. 2020

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Abstract. Aerosol sulfate is a major component of submicron particulate matter (PM1). Sulfate can be present as inorganic (mainly ammonium sulfate, AS) or organic sulfate (OS). Although OS are thought to be a smaller fraction of total sulfate in most cases, recent literature argues that this may not be the case in more polluted environments. Aerodyne Aerosol Mass Spectrometers (AMS) measure total submicron sulfate, but it has been difficult to apportion AS vs. OS as the detected ion fragments are similar. Recently, two new methods have been proposed to quantify OS separately from AS with AMS data. We use observations collected during several airborne field campaigns covering a wide range of sources and airmass ages (spanning the continental US, marine remote troposphere, and Korea) and targeted laboratory experiments to investigate the performance and validity of the proposed OS methods. Four chemical regimes are defined to categorize the factors impacting sulfate fragmentation (Fig. shown in abstract). In polluted areas with high ammonium nitrate concentrations and in remote areas with high aerosol acidity, the decomposition and fragmentation of sulfate in the AMS is influenced by multiple complex effects, and estimation of OS does not seem possible with current methods. In regions with lower acidity (pH>0) and ammonium nitrate (fraction<0.3), the proposed OS methods might be more reliable, although application of these methods often produced nonsensical results. However, the fragmentation of ambient neutralized sulfate varies somewhat within studies, adding uncertainty, possibly due to variations in the effect of organics. Under highly acidic conditions, sulfate fragment ratios show a clear relationship with acidity (pH and ammonium balance). The measured ammonium balance (and to a lesser extent, the HySOx+/SOx+ AMS ratio) is a promising indicator for rapid estimation of aerosol pH < 0, including when gas-phase NH3 and HNO3 are not available. These results allow an improved understanding of important intensive properties of ambient aerosols.

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“…An accommodation coefficient of 1 for ammonia onto acidic PM was assumed (Hanson and Kosciuch, 2003), with a density of 1.8 g cm −3 for sulfuric acid (Rumble, 2019). For the mass transfer calculations, the transition regime (between the free molecular and continuum regimes) equations were used with the Fuchs and Sutugin parameterization (Fuchs and Sutugin, 1971). The model was used to estimate the ammonia molecular flux to acidic PM on the filter (Eq.…”

Section: Theoretical Ammonia Flux Modelmentioning

confidence: 99%

Interferences with aerosol acidity quantification due to gas-phase ammonia uptake onto acidic sulfate filter samples

et al. 2020

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Abstract. Measurements of the mass concentration and chemical speciation of aerosols are important to investigate their chemical and physical processing from near emission sources to the most remote regions of the atmosphere. A common method to analyze aerosols is to collect them onto filters and analyze the filters offline; however, biases in some chemical components are possible due to changes in the accumulated particles during the handling of the samples. Any biases would impact the measured chemical composition, which in turn affects our understanding of numerous physicochemical processes and aerosol radiative properties. We show, using filters collected onboard the NASA DC-8 and NSF C-130 during six different aircraft campaigns, a consistent, substantial difference in ammonium mass concentration and ammonium-to-anion ratios when comparing the aerosols collected on filters versus an Aerodyne aerosol mass spectrometer (AMS). Another online measurement is consistent with the AMS in showing that the aerosol has lower ammonium-to-anion ratios than obtained by the filters. Using a gas uptake model with literature values for accommodation coefficients, we show that for ambient ammonia mixing ratios greater than 10 ppbv, the timescale for ammonia reacting with acidic aerosol on filter substrates is less than 30 s (typical filter handling time in the aircraft) for typical aerosol volume distributions. Measurements of gas-phase ammonia inside the cabin of the DC-8 show ammonia mixing ratios of 45±20 ppbv, consistent with mixing ratios observed in other indoor environments. This analysis enables guidelines for filter handling to reduce ammonia uptake. Finally, a more meaningful limit of detection for University of New Hampshire Soluble Acidic Gases and Aerosol (SAGA) filters collected during airborne campaigns is ∼0.2 µg sm−3 of ammonium, which is substantially higher than the limit of detection of ion chromatography. A similar analysis should be conducted for filters that collect inorganic aerosol and do not have ammonia scrubbers and/or are handled in the presence of human ammonia emissions.

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A new method to quantify mineral dust and other aerosol species from aircraft platforms using single-particle mass spectrometry

Cited by 76 publications

References 148 publications

Characterization of organic aerosol across the global remote troposphere: a comparison of ATom measurements and global chemistry models

Characterization of organic aerosol across the global remote troposphere: a comparison of ATom measurements and global chemistry models

Aerosol pH Indicator and Organosulfate Detectability from Aerosol Mass Spectrometry Measurements

Interferences with aerosol acidity quantification due to gas-phase ammonia uptake onto acidic sulfate filter samples

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