Size-resolved aerosol pH over Europe during summer

Ζακούρα, Μαρία; Kakavas, Stylianos; Nenes, Athanasios; Pandis, Spyros N.

doi:10.5194/acp-2019-1146

Cited by 6 publications

(4 citation statements)

References 19 publications

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“…The pH calculated here is compared against pH estimations from field derived PM 2.5 compositional data around the world compiled by Pye et al (2020) (Table S1). pH data derived from other aerosol sizes (e.g., PM 1 ) has been omitted since aerosol acidity can vary significantly with size (Zakoura et al, 2020 in Table S1 aims to corroborate the spatial variability of pH found in this study and not to strictly evaluate the model calculations. Observationally estimated aerosol pH is derived from a variety of methods that can affect the result significantly as discussed above (i.e., the use of E-AIM or ISORROPIA, stable/metastable assumption, forward/reverse mode, and the availability of gas phase NH 3 /HNO 3 , crustal species, and organic aerosol water observations).…”

Section: Ph Calculationsmentioning

confidence: 99%

How alkaline compounds control atmospheric aerosol acidity

Karydis¹,

Tsimpidi²,

Pozzer³

et al. 2020

Preprint

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Abstract. The acidity of atmospheric aerosols regulates the particulate mass, composition and toxicity, and has important consequences for public health, ecosystems and climate. Despite these broad impacts, the global distribution and evolution of aerosol acidity are unknown. We used the particular, comprehensive atmospheric multiphase chemistry – climate model EMAC to investigate the main factors that control aerosol acidity, and uncovered remarkable variability and unexpected trends during the past 50 years in different parts of the world. We find that alkaline compounds, notably ammonium, and to a lesser extent crustal cations, buffer the aerosol pH on a global scale. Given the importance of aerosols for the atmospheric energy budget, cloud formation, pollutant deposition and public health, alkaline species hold the key to control strategies for air quality and climate change.

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Section: Ph Calculationsmentioning

confidence: 99%

How alkaline compounds control atmospheric aerosol acidity

Karydis¹,

Tsimpidi²,

Pozzer³

et al. 2020

Preprint

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“…Dust particles chemically age in the atmosphere, getting coated by acids (such as sulphuric acid, nitric acid or chlorine), or organic species (Goodman et al, 2000). The uptake rates of such compounds on dust aerosols are enhanced by the amount of calcite and other alkaline components present (Krueger et al, 2004;Zakoura et al, 2020). Due to these coatings, originally hydrophobic dust becomes hygroscopic, which favors cloud formation processes (Usher et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

Gonçalves¹,

Obiso

Miller

et al. 2023

Preprint

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Abstract. Soil dust aerosols are a key component of the climate system, as they interact with short- and long-wave radiation, alter cloud formation processes, affect atmospheric chemistry and play a role in biogeochemical cycles by providing nutrient inputs such as iron and phosphorus. The influence of dust on these processes depends on its physico-chemical properties, which far from being homogeneous, are shaped by its regionally varying mineral composition. The relative amount of minerals in dust depends on the source region and shows a large geographical variability. However, many state-of-the-art Earth System Models (ESMs), upon which climate analyses and projections rely, still consider dust mineralogy as invariant. The explicit representation of minerals in ESMs is more hindered by our limited knowledge of the global soil composition along with the resulting size-resolved airborne mineralogy than by computational constraints. In this work, we introduce an explicit mineralogy representation within the state-of-the-art atmosphere-chemistry model MONARCH. We review and compare two existing soil mineralogy datasets, which remain a source of uncertainty for dust mineralogy modelling, and provide an evaluation of multi-annual simulations against available mineralogy observations. Soil mineralogy datasets are based on measurements performed after wet sieving, which breaks the aggregates found in the parent soil. Our model predicts the emitted particle size distribution (PSD) in terms of its constituent minerals based on Brittle Fragmentation Theory (BFT), which reconstructs the emitted mineral aggregates destroyed by wet sieving. Our simulations broadly reproduce the most abundant mineral fractions, independently of the soil composition data used. Feldspars and calcite are highly sensitive to the soil mineralogy map, mainly due to the different assumptions made in each soil dataset to extrapolate a handful of soil measurements to arid and semiarid regions worldwide. For the least abundant or more difficult to determine minerals, such as the iron oxides, uncertainties in soil mineralogy yield differences in annual mean aerosol mass fractions of up to ∼100 %. Although BFT restores coarse aggregates including phyllosilicates that usually break during soil analysis, we still identify an overestimation of coarse quartz mass fractions (above 2 µm in diameter). In a dedicated experiment, we estimate the fraction of dust with undetermined composition as given by a soil map, which makes a ∼10 % of the emitted dust mass at the global scale, and can be regionally larger. Changes in the underlying soil mineralogy impact our estimates of climate-relevant variables, particularly affecting the regional variability of the single scattering albedo at solar wavelengths, or the total iron deposited over oceans. All in all, this assessment represents a baseline for future model experiments including new mineralogical maps constrained by high quality spaceborne hyperspectral measurements, such as those arising from the NASA EMIT mission.

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“…Each method has different advantages and disadvantages (e.g., time resolution, sample preparation, range of species identified, cost, and personnel needs). These results, in turn, have been used to inform and improve the results of CTMs, influencing our understanding of processes such as the direct radiative effect (Wang et al, 2008b), transport of ammonia in deep convection (Ge et al, 2018), aerosol pH (Pye et al, 2020;Zakoura et al, 2020) and subsequent chemistry, and precursor emissions (Henze et al, 2009;Heald et al, 2012;Walker et al, 2012;Mezuman et al, 2016).…”

Section: Introductionmentioning

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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Size-resolved aerosol pH over Europe during summer

Cited by 6 publications

References 19 publications

How alkaline compounds control atmospheric aerosol acidity

How alkaline compounds control atmospheric aerosol acidity

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

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

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