A New Method to Measure Aerosol Particle Bounce Using a Cascade Electrical Low Pressure Impactor

Jain, Shashank; Petrucci, Giuseppe A.

doi:10.1080/02786826.2015.1036393

Cited by 30 publications

(47 citation statements)

References 46 publications

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“…Details of the method used to estimate the phase state of generated SOA is presented elsewhere [42]. Briefly, two separate cascade impactors are used to perform bounce analysis and calculate bounce factor (BF).…”

Section: Bounce Analysismentioning

confidence: 99%

“…Current distributions to estimate the bounce factor and aerosol particle number size distributions were measured continuously using an electrical low pressure impactor (ELPI+, Dekati, Finland) operating either with sintered plates (to eliminate particle bounce) or smooth plates (to favor particle bounce) [42]. Aerosol particle number size distributions were also measured in parallel with a scanning mobility particle sizer (SMPS model 3080, TSI Inc., Shoreview, MN, USA) operating at 0.3 L min −1 and 3.0 L min −1 for aerosol flow and sheath flow, respectively.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Absolute Mass Loading of Secondary Organic Aerosols on Their Phase State

2018

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Absolute secondary organic aerosol (SOA) mass loading (C SOA ) is a key parameter in determining partitioning of semi-and intermediate volatility compounds to the particle phase. Its impact on the phase state of SOA, however, has remained largely unexplored. In this study, systematic laboratory chamber measurements were performed to elucidate the influence of C SOA , ranging from 0.2 to 160 µg m −3 , on the phase state of SOA formed by ozonolysis of various precursors, including α-pinene, limonene, cis-3-hexenyl acetate (CHA) and cis-3-hexen-1-ol (HXL). A previously established method to estimate SOA bounce factor (BF, a surrogate for particle viscosity) was utilized to infer particle viscosity as a function of C SOA . Results show that under nominally identical conditions, the maximum BF decreases by approximately 30% at higher C SOA , suggesting a more liquid phase state. With the exception of HXL-SOA (which acted as the negative control), the phase state for all studied SOA precursors varied as a function of C SOA . Furthermore, the BF was found to be the maximum when SOA particle distributions reached a geometric mean particle diameter of 50-60 nm. Experimental results indicate that C SOA is an important parameter impacting the phase state of SOA, reinforcing recent findings that extrapolation of experiments not conducted at atmospherically relevant SOA levels may not yield results that are relevant to the natural environment.

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Section: Bounce Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Influence of Absolute Mass Loading of Secondary Organic Aerosols on Their Phase State

2018

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“…The electrical low-pressure impactor technique assesses particle phase based on bounce factor but relies on substrate deposition and indirectly infers liquid vs nonliquid aerosol. 12,13 Recently, an atomic force microscopy (AFM)based technique has been introduced that qualitatively distinguishes between liquid, semisolid, and solid states but is also predicated on substrate deposition. 14−16 Viscosity and phase have also been studied with the bead-mobility and pokeflow techniques but depend on substrate deposition.…”

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confidence: 99%

Dual-Balance Electrodynamic Trap as a Microanalytical Tool for Identifying Gel Transitions and Viscous Properties of Levitated Aerosol Particles

et al. 2020

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2020). Dual-balance electrodynamic trap as a microanalytical tool for identifying gel transitions and viscous properties of levitated aerosol particles.ABSTRACT: The formation of gelatinous networks within an aerosol particle significantly alters the physicochemical properties of the aerosol material. Existing techniques for studying gel transitions rely on bulk rheometry, which is limited by contact with the sample, or microrheological techniques such as holographic optical tweezers, which rely on expensive equipment and high-powered lasers that can degrade light-absorbing aerosol. Here, we present a new technique to probe the microrheological characteristics of aerosol particles and explore gel formation under atmospheric conditions in a contactless environment without the need for high-power light sources. In a dualbalance quadrupole electrodynamic balance, levitated droplets of opposite polarity are trapped and equilibrated at fixed relative humidity (RH) and then subsequently merged, and the physical characteristics of the merged droplets are monitored as a function of time and RH using imaging techniques. By comparing the RHdependent characteristics of MgSO 4 (known to undergo a gel transition) to glucose and sucrose (known to remain as viscous Newtonian fluids) under fixed equilibration time scales, we demonstrate that gel phase transitions can be identified in aerosol particles, with MgSO 4 abruptly transitioning to a rigid microgel at 30% RH. Further, we demonstrate this technique can be used to also measure aerosol viscosity and identify non-Newtonian fluid dynamics in model sea spray aerosol composed of NaCl, CaCl 2 , and sorbitol. Thus, using this experimental technique, it is possible to distinguish between aerosol compositions that form viscous Newtonian fluids and those that undergo a gel transition or form non-Newtonian fluids. This technique offers a simple and costeffective analytical tool for probing gel transitions outside of bulk solubility limits, with relevant applications ranging from atmospheric science to microengineering of soft matter materials.

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“…The phase state is also strongly affected by relative humidity, as water can act as a plasticizer to lower viscosity (Mikhailov et al, 2009). Ambient and laboratorygenerated SOA particles have been observed to bounce off the smooth hard surface of an inertial impactor at low RH, implying a non-liquid state (Virtanen et al, 2010;Saukko et al, 2012;Bateman et al, 2015;Jain and Petrucci, 2015), whereas predominantly biogenic SOA particles in the Amazon basin did not bounce off the impactor surface at high RH, implying that they are primarily liquid (Bateman et al, 2016). Upon dilution or heating, SOA particles were observed to evaporate unexpectedly slowly (Cappa and Wilson, 2011;Vaden et al, 2011), and recent modeling studies have evaluated the contributions of low diffusivity and volatility to slow evaporation rates (Roldin et al, 2014;Yli-Juuti et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

et al. 2018

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Abstract. Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (T g ). We have recently developed a method to estimate T g of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol −1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol −1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the T g -scaled Arrhenius plot of fragility (viscosity vs. T g /T ) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon-Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of T g , D, the hygroscopicity parameter (κ), and the Gordon-Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2-5 orders of magnitude. Complementary measurements of viscosity and chemical composition are desired to further constrain RH-dependent viscosity in future studies.

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A New Method to Measure Aerosol Particle Bounce Using a Cascade Electrical Low Pressure Impactor

Cited by 30 publications

References 46 publications

The Influence of Absolute Mass Loading of Secondary Organic Aerosols on Their Phase State

The Influence of Absolute Mass Loading of Secondary Organic Aerosols on Their Phase State

Dual-Balance Electrodynamic Trap as a Microanalytical Tool for Identifying Gel Transitions and Viscous Properties of Levitated Aerosol Particles

Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

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