Determining the link between hygroscopicity and composition for semi-volatile aerosol species

Alroe, Joel; Cravigan, Luke T.; Mallet, Marc; Ristovski, Zoran; Miljevic, Branka; Osuagwu, Chiemeriwo Godday; Johnson, Graham R.

doi:10.5194/amt-11-4361-2018

Cited by 5 publications

(10 citation statements)

References 55 publications

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“…Size distributions and number concentrations of 10 to 300 nm diameter SSA were measured using a TSI 3080 scanning mobility particle sizer (SMPS), coupled with a 3071 differential mobility analyser and a 3010 condensation particle counter (CPC) (TSI, Shoreview, MN), with an aerosol sample flow rate of 1 L min −1 and a sheath flow rate of 10 L min −1 . The volatility and hygroscopicity of nascent SSA was determined with a volatility and hygroscopicity tandem differential mobility analyser (VH-TDMA) (Alroe et al, 2018;Johnson et al, 2008Johnson et al, , 2004. The VH-TDMA selects particles based on mobility diameter, conditions them, and measures the resulting particle size distributions using parallel SMPSs (V-SMPS and H-SMPS in Fig.…”

Section: Measurements/instrumentationmentioning

confidence: 99%

“…Externally mixed organics have also been observed to comprise the majority of the number concentration of sub-180 nm SSA in some studies (Collins et al, 2014(Collins et al, , 2013Prather et al, 2013). It should be noted that the externally mixed organic fraction still contained inorganic ions but was characterised by an absence of Cl (Ault et al, 2013a).…”

Section: Introductionmentioning

confidence: 96%

“…The enrichment of Ca 2+ in SSA, relative to seawater, has been identified in a number of ambient marine (Leck and Svensson, 2015;Sievering et al, 2004) and nascent SSA chamber studies (Keene et al, 2007;Salter et al, 2016;Schwier et al, 2017). Cation enrichment has also been observed in the form of Mg 2+ and K + (Ault et al, 2013b;Schwier et al, 2017) and is also associated with deficits in Cl − (Ault et al, 2013a;Prather et al, 2013;Schwier et al, 2017). PM 1 Ca 2+ has been observed to be enriched by up to 500 % (Schwier et al, 2017), relative to seawater, with a number of studies showing stronger enrichment for sub-100 nm diameter SSA (Leck and Svensson, 2015;Salter et al, 2016).…”

Section: Introductionmentioning

confidence: 97%

“…It is uncertain whether the ocean surface Ca 2+ is complexed with organic matter or is the product of precipitation of CaCO 3 by certain phytoplankton groups, which can be a product of photosynthetic reactions. Observations of organic carbon particles that contain inorganic cations (such as Ca 2+ , Mg 2+ and K + ) but no Cl − has also been reported, suggesting that in some cases these species complex with organic material (Ault et al, 2013a).…”

Section: Introductionmentioning

confidence: 99%

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Sea spray aerosol organic enrichment, water uptake and surface tension effects

et al. 2020

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Abstract. The aerosol-driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, in particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of sea spray aerosol organic enrichment and the resulting impact on water uptake over the remote Southern Hemisphere are scarce, and therefore the region is under-represented in existing parameterisations. The Surface Ocean Aerosol Production (SOAP) voyage was a 23 d voyage which sampled three phytoplankton blooms in the highly productive water of the Chatham Rise, east of New Zealand. In this study we examined the enrichment of organics to nascent sea spray aerosol and the modifications to sea spray aerosol water uptake using in situ chamber measurements of seawater samples taken during the SOAP voyage. Primary marine organics contributed up to 23 % of the sea spray mass for particles with diameter less than approximately 1 µm and up to 79 % of the particle volume for 50 nm diameter sea spray. The composition of the submicron organic fraction was consistent throughout the voyage and was largely composed of a polysaccharide-like component, characterised by very low alkane-to-hydroxyl-concentration ratios of approximately 0.1–0.2. The enrichment of organics was compared to the output from the chlorophyll-a-based sea spray aerosol parameterisation suggested by Gantt et al. (2011) and the OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) models. OCEANFILMS improved on the representation of the organic fraction predicted using chlorophyll a, in particular when the co-adsorption of polysaccharides was included; however, the model still under-predicted the proportion of polysaccharides by an average of 33 %. Nascent 50 nm diameter sea spray aerosol hygroscopic growth factors measured at 90 % relative humidity averaged 1.93±0.08 and did not decrease with increasing sea spray aerosol organic fractions. The observed hygroscopicity was greater than expected from the assumption of full solubility, particularly during the most productive phytoplankton bloom (B1), during which organic fractions were greater than approximately 0.4. The water uptake behaviour observed in this study is consistent with that observed for other measurements of phytoplankton blooms and can be partially attributed to the presence of sea salt hydrates, which lowers the sea spray aerosol hygroscopicity when the organic enrichment is low. The inclusion of surface tension effects only marginally improved the modelled hygroscopicity, and a significant discrepancy between the observed and modelled hygroscopicity at high organic volume fractions remained. The findings from the SOAP voyage highlight the influence of biologically sourced organics on sea spray aerosol composition; these data improve the capacity to parameterise sea spray aerosol organic enrichment and water uptake.

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Section: Measurements/instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Sea spray aerosol organic enrichment, water uptake and surface tension effects

et al. 2020

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Section: Measurements/instrumentationmentioning

confidence: 99%

Sea spray aerosol organic enrichment, water uptake and surface tension effects

Cravigan¹,

Mallet²,

Vaattovaara³

et al. 2019

Preprint

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Abstract. The aerosol driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, in particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of sea spray aerosol organic enrichment and the resulting impact on water uptake over the remote southern hemisphere are scarce, and are therefore the region is under-represented in existing parameterisations. The Surface Ocean Aerosol Production (SOAP) voyage was a 23 day voyage which sampled three phytoplankton blooms in the highly productive water of the Chatham Rise, east of New Zealand. In this study we examined the enrichment of organics to nascent sea spray aerosol and the modifications to sea spray aerosol water uptake using in-situ chamber measurements of seawater samples taken during the SOAP voyage. Primary marine organics contributed up to 23 % of the sea spray mass for particles with diameter less than approximately 1 μm, and up to 87 % of the particle volume in the Aitken mode. The composition of the organic fraction was consistent throughout the voyage and was largely comprised of a polysaccharide-like component, characterised by very low alkane to hydroxyl concentration ratios of approximately 0.1–0.2. The enrichment of organics was compared to the output from the chlorophyll-a based sea spray aerosol parameterisation suggested by Gantt et al. (2011) and the OCEANFILMS models. OCEANFILMS improved on the representation of the organic fraction predicted using chlorophyll-a, in particular when the co-adsoprtion of polysaccharides was included, however the model still under predicted the proportion of polysaccharides by an average of 33 %. Nascent sea spray aerosol hygroscopic growth factors averaged 1.93 ± 0.08, and did not decrease with increasing sea spray aerosol organic fractions. The observed hygroscopicity was greater than expected from the assumption of full solubility, particularly during the most productive phytoplankton bloom (B1), during which organic fractions were greater than approximately 0.4. The water uptake behaviour observed in this study is consistent with that observed for other measurements of phytoplankton blooms, and was attributed to the surface partitioning of the organic components which leads to a decrease in particle surface tension and an increase in hygroscopicity. The compressed film model was used to estimate the influence of surface partitioning and the error in the modelled hygroscopicity was low only when the entire organic fraction was available to partition to the particle surface. The modelled sea spray aerosol hygroscopicity at high organic fractions was underestimated when only a portion of the organic component was available to be partitioned to the surface. The findings from the SOAP voyage highlight the influence of biologically-sourced organics on sea spray aerosol composition, these data improve the capacity to parameterise sea spray aerosol organic enrichment and water uptake.

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