Determination of Water Activity in Ammonium Sulfate and Sulfuric Acid Mixtures Using Levitated Single Particles

Kim, Yong Pyo; Pun, Betty K.; Chan, Chak K.; Flagan, Richard C.; Seinfeld, John H.

doi:10.1080/02786829408959683

Cited by 43 publications

(33 citation statements)

References 31 publications

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“…The growth of inorganic salts and mixtures of salts have also been studied in the laboratory using electric fields to trap single particles that are subjected to varying humidity conditions. [5][6][7][8] Results from these studies, in general, have agreed reasonably well with thermodynamic model predictions for inorganic aerosol growth. These research efforts provide a basic understanding of how inorganic aerosols respond when the relative humidity is changing and also serve as a basis for modeling the equilibrium chemistry of inorganic atmospheric aerosols.…”

Section: Introductionsupporting

confidence: 55%

Aerosol Light Scattering Measurements as a Function of Relative Humidity

Day

Malm

Kreidenweis

2000

Journal of the Air & Waste Management Association

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The hygroscopic nature of atmospheric fine aerosol was investigated at a rural site in the Great Smoky Mountains National Park during July and August 1995. Passing the sample aerosol through an inlet, which housed an array of Perma Pure diffusion dryers, controlled the sample aerosol's relative humidity (RH). After conditioning the aerosol sample in the inlet, the light scattering coefficient and the aerosol size distribution were simultaneously measured. During this study, the conditioned aerosol's humidity ranged between 5% < RH < 95%. Aerosol response curves were produced using the ratio b spw / b spd ; where b spw is the scattering coefficient measured at some RH greater than 20% and b spd is the scattering coefficient of the "dry" aerosol. For this work, any sample RH values below 15% were considered dry. Results of this investigation showed that the light scattering ratio increased continuously and smoothly over the entire range of relative humidity. The magnitude of the ratio at a particular RH value, however, varied considerably in time, particularly for RH values greater than approximately 60%. Curves of the scattering coefficient ratios as a function of RH were IMPLICATIONS Ambient aerosol particles are known to absorb or release water in response to the changing RH conditions of the atmosphere. As particles lose or absorb liquid water their physical and chemical properties such as size and index of refraction will change. These changes can dramatically influence the extent of interaction between the aerosol particles and the solar radiation incident upon them. This work focuses on measuring the change in the light scattering coefficient with a change in RH, which has important implications both in visibility research and global climate modeling. generated for each day and compared to the average 12-hour chemical composition of the aerosol. This comparison showed that for any particular RH value the ratio was highest during time periods of high sulfate concentrations and lowest during time periods of high soil or high organic carbon concentrations.

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Section: Introductionsupporting

confidence: 55%

Aerosol Light Scattering Measurements as a Function of Relative Humidity

Day

Malm

Kreidenweis

2000

Journal of the Air & Waste Management Association

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“…This range is typical of indoor residential environments in the Southeast controlled by an HVAC system. Data from Kim et al (1994 ) showed that the moisture uptake of ammonium sulfate (NH 4 SO 4 ) particles increases dramatically above approximately 60% RH. This suggested that significant changes in moisture uptake might be observed above this humidity and should be avoided.…”

Section: Rodes Et Almentioning

confidence: 99%

Experimental methodologies and preliminary transfer factor data for estimation of dermal exposures to particles

Rodes

Newsome

Vanderpool

et al. 2001

J Expo Sci Environ Epidemiol

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Developmental efforts and experimental data that focused on quantifying the transfer of particles on a mass basis from indoor surfaces to human skin are described. Methods that utilized a common fluorescein -tagged Arizona Test Dust ( ATD ) as a possible surrogate for housedust and a uniform surface dust deposition chamber to permit estimation of particle mass transfer for selected dust size fractions were developed. Particle transfers to both wet and dry skin were quantified for contact events with stainless steel, vinyl, and carpeted surfaces that had been pre -loaded with the tagged test dust. To better understand the representativeness of the test dust, a large housedust sample was collected and analyzed for particle size distribution by mass and several metals ( Pb, Mn, Cd, Cr, and Ni ) . The real housedust sample was found to have multimodal size distributions ( mg / g ) for particle -phase metals. The fluorescein tagging provided surface coatings of 0.11 ± 0.36 ng fluorescein per gram of dust. The predominant surface location of the fluorescein tag would best represent simulated mass transfers for contaminant species coating the surfaces of the particles. The computer -controlled surface deposition chamber provided acceptably uniform surface coatings with known particle loadings on the contact test panels. Significant findings for the dermal transfer factor data were: ( a ) only about 1 / 3 of the projected hand surface typically came in contact with the smooth test surfaces during a press; ( b ) the fraction of particles transferred to the skin decreased as the surface roughness increased, with carpeting transfer coefficients averaging only 1 / 10 those of stainless steel; ( c ) hand dampness significantly increased the particle mass transfer; ( d ) consecutive presses decreased the particle transfer by a factor of 3 as the skin surface became loaded, requiring $100 presses to reach an equilibrium transfer rate; and ( e ) an increase in metals concentration with decreasing particle size, with levels at 25 m typically two or more times higher than those at 100 m Ð consistent with the earlier finding of Lewis et al. for the same sample for pesticides and polycyclic aromatic hydrocarbons ( PAHs ) .

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“…5 might therefore be attributed to the particles' SA core being liquid, with potential effects of SA also in the organic shell. As far as the liquid content is concerned, a very rough estimate of the liquid content (water and sulfuric acid) can be made by assuming phase separation and water uptake of sulphuric acid according to Kim et al (1994). Based on this, the water+H 2 SO 4 -volume concentration of the particles is above 60 % for the case of 0.36 SO 4 fraction, and below 31 % for the case of 0.09 SO 4 fraction.…”

Section: Phase State and Humidity-induced Phase Transitions Of Mixed mentioning

confidence: 99%

Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors

et al. 2012

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Abstract. The physical phase state (solid, semi-solid, or liquid) of secondary organic aerosol (SOA) particles has important implications for a number of atmospheric processes. We report the phase state of SOA particles spanning a wide range of oxygen to carbon ratios (O / C), used here as a surrogate for SOA oxidation level, produced in a flow tube reactor by photo-oxidation of various atmospherically relevant surrogate anthropogenic and biogenic volatile organic compounds (VOCs). The phase state of laboratory-generated SOA was determined by the particle bounce behavior after inertial impaction on a polished steel substrate. The measured bounce fraction was evaluated as a function of relative humidity and SOA oxidation level (O / C) measured by an Aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF AMS).The main findings of the study are: (1) biogenic and anthropogenic SOA particles are found to be amorphous solid or semi-solid based on the measured bounced fraction (BF), which was typically higher than 0.6 on a 0 to 1 scale. A decrease in the BF is observed for most systems after the SOA is exposed to relative humidity of at least 80 % RH, corresponding to a RH at impaction of 55 %. (2) Long-chain alkanes have a low BF (indicating a "liquid-like", less viscous phase) particles at low oxidation levels (BF < 0.2 ± 0.05 for O / C = 0.1). However, BF increases substantially upon increasing oxidation. (3) Increasing the concentration of sulphuric acid (H 2 SO 4 ) in solid SOA particles (here tested for longifolene SOA) causes a decrease in BF levels. (4) In the majority of cases the bounce behavior of the various SOA systems did not show correlation with the particle O / C. Rather, the molar mass of the gas-phase VOC precursor showed a positive correlation with the resistance to the RH-induced phase change of the formed SOA particles.

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Determination of Water Activity in Ammonium Sulfate and Sulfuric Acid Mixtures Using Levitated Single Particles

Cited by 43 publications

References 31 publications

Aerosol Light Scattering Measurements as a Function of Relative Humidity

Aerosol Light Scattering Measurements as a Function of Relative Humidity

Experimental methodologies and preliminary transfer factor data for estimation of dermal exposures to particles

Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors

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