Henry's Law Solubility Constant Research Articles

Development of a multiphase chemical mechanism to improve secondary organic aerosol formation in CAABA/MECCA (version 4.7.0)

Abstract. During the last few decades, the impact of multiphase chemistry on secondary organic aerosols (SOAs) has been demonstrated to be the key to explaining laboratory experiments and field measurements. However, global atmospheric models still show large biases when simulating atmospheric observations of organic aerosols (OAs). Major reasons for the model errors are the use of simplified chemistry schemes of the gas-phase oxidation of vapours and the parameterization of heterogeneous surface reactions. The photochemical oxidation of anthropogenic and biogenic volatile organic compounds (VOCs) leads to products that either produce new SOA or are taken up by existing aqueous media like cloud droplets and deliquescent aerosols. After partitioning, aqueous-phase processing results in polyols, organosulfates, and other products with a high molar mass and oxygen content. In this work, we introduce the formation of new low-volatility organic compounds (LVOCs) to the multiphase chemistry box model CAABA/MECCA. Most notable are the additions of the SOA precursors, limonene and n-alkanes (5 to 8 C atoms), and a semi-explicit chemical mechanism for the formation of LVOCs from isoprene oxidation in the gas and aqueous phases. Moreover, Henry's law solubility constants and their temperature dependences are estimated for the partitioning of organic molecules to the aqueous phase. Box model simulations indicate that the new chemical scheme predicts the enhanced formation of LVOCs, which are known for being precursor species to SOAs. As expected, the model predicts that LVOCs are positively correlated to temperature but negatively correlated to NOx levels. However, the aqueous-phase processing of isoprene epoxydiols (IEPOX) displays a more complex dependence on these two key variables. Semi-quantitative comparison with observations from the SOAS campaign suggests that the model may overestimate methylbutane-1,2,3,4-tetrol (MeBuTETROL) from IEPOX. Further application of the mechanism in the modelling of two chamber experiments, one in which limonene is consumed by ozone and one in which isoprene is consumed by NO3 shows a sufficient agreement with experimental results within model limitations. The extensions in CAABA/MECCA are transferred to the 3D atmospheric model MESSy for a comprehensive evaluation of the impact of aqueous- and/or aerosol-phase chemistry on SOA at a global scale in a follow-up study.

Measurement of Henry's law constants of ethyl nitrate in deionized water, synthetic sea salt solutions, and n-octanol

Ethyl nitrate (EN; C2H5ONO2) is an important component of atmospheric “odd nitrogen” (NOy) whose main source is marine emissions. To correctly describe its air-water transfer and model its global distribution, accurate values for its temperature- and salinity-dependent Henry's law solubility constants are needed. Here, we report Henry's law (HScp) constants for EN in deionized (DI) water, synthetic sea salt solutions (SSS), and n-octanol at temperatures between 278.2 K and 303.2 K. For DI water, HScp constants of (2.03 ± 0.06) M atm−1 at 293.2 K and (4.88 ± 0.13) M atm−1 at 278.2 K were observed (all stated uncertainties are at the 1σ level). The data are best described by ln(HScp(aq)/[Matm−1]) = -(16.2 ± 0.4)+(4.94 ± 0.11) × 103/T and ln(HScp(octanol)/[Matm−1]) = -(11.1 ± 1.9)+(4.15 ± 0.33) × 103/T, from which the octanol-water partition coefficient (KOW) was calculated. A temperature-independent salting-out factor of 1.25 ± 0.03 and Setschenow constant of KS = (0.33 ± 0.04) mol kg−1 were determined for SSS. Liquid-phase losses of EN were negligible in all solvents (kl < 1 × 10−4 s−1). The HScp(aq) values agree with results by Kames (1993) but are between 2% (at 303.2 K) and 19% (at 278.2 K) lower than the widely used parameterization by Kames and Schurath (1992), indicating a systemic bias in the EN literature and modelling of the Earth's nitrogen cycle.

Corrigendum—The importance of temperature on Henry's‐law solubility constants: Removing trihalomethanes by aeration

Corrigendum—The importance of temperature on Henry's‐law solubility constants: Removing trihalomethanes by aeration

Indoor partitioning and potential thirdhand exposure to carbonyl flavoring agents added in e-cigarettes and hookah tobacco.

Flavoring agents added to the e-cigarettes and hookah tobacco have increased the attractiveness of novel nicotine products. Many widely used flavorings are carbonyls, which are toxic to humans. In an indoor environment, residents can be exposed to such harmful flavorings previously emitted to the surrounding environment, through a process termed thirdhand exposure. The recent discovery of a large volume of indoor reservoirs emphasizes the importance of indoor partitioning, which is responsible for thirdhand exposure. Indoor partitioning can be expressed with partitioning coefficients, such as Henry's law solubility constant (H). However, reliable H values for many key flavorings are currently lacking. To better understand their environmental behavior, this study experimentally determined the effective Henry's law constant (Hcps,eff) using the inert gas stripping (IGS) method. Further, the influence of the hydration process for target flavorings was quantified using proton nuclear magnetic resonance (1H NMR) spectroscopy. We found that hydration of α-dicarbonyls (diacetyl and 2,3-pentanedione) enhanced their Hcps,eff from their intrinsic Henry's law constant (Hcps) by a factor of 3.52 and 2.88, respectively. The two-dimensional partitioning plots were employed to simulate the indoor phase distribution and evaluate the pathways of human exposure. Our findings show that the indoor partitioning of many harmful flavorings is highly sensitive to temperature and the size of indoor reservoirs, indicating that residents are likely to experience third-hand exposure.

The importance of temperature on Henry's‐law solubility constants: Removing trihalomethanes by aeration

AbstractMany small drinking water systems have faced, or are facing, difficulties in meeting U.S. Safe Drinking Water Act regulations. Aeration is a technology that could be effective in helping small systems meet trihalomethane standards, but its effectiveness is based on Henry's law. Henry's law governs the relationship between the concentration of a volatile organic chemical in liquid and the gas' vapor pressure over that liquid. The higher the Henry's‐law constant, the more readily the compound can be transferred from water to air. Henry's‐law constant is independent of flow rate but, as discussed in this article, is a function of temperature. This article provides information on the relationship of temperature to the value of Henry's‐law constants with the goal of assisting water system managers and operators in optimizing aeration for removing disinfection byproducts.

Free energy of solvation and Henry's law solubility constants for mono-, di- and tri-ethylene glycol in water and methane

Free energy of solvation (i.e. residual chemical potential) and Henry's law solubility constants were estimated for mono ethylene glycol (MEG), diethylene glycol (DEG) and triethylene glycol (TEG) with water and methane as solvents at both 298 K and 1 atm and at 283 K and 80 atm using molecular dynamics simulations. Three methods of calculating free energies of solvation were compared: free energy perturbation (FEP), thermodynamic integration (TI) and Bennett acceptance ratio (BAR) method. The solubility constants were estimated based on the obtained free energies and were compared to the previously reported values. We found that free energy differences obtained using the three applied methods agreed very well. For both MEG and DEG the estimated solubility constants were within the same order of magnitude as previously reported solubility constants and therefore in good agreement. The estimated solubility constants of TEG were found to be about an order of magnitude smaller than the lowest reported value, and would still yield a reasonable estimate of residual chemical potential due to the logarithmic dependence.

Heterogeneous Chemistry of Butanol and Decanol with Sulfuric Acid: Implications for Secondary Organic Aerosol Formation

Recent environmental chamber studies suggest that acid-catalyzed reactions between alcohols and aldehydes in the condensed phase lead to the formation of hemiacetals and acetals, enhancing secondary organic aerosol (SOA) growth. We report measurements of heterogeneous uptake of butanol and decanol on liquid H2SO4 in the range of 62-84 wt % and between 273 and 296 K. Both alcohols exhibit two distinct types of uptake behaviors (partially irreversible vs totally irreversible uptake), depending on the acid concentration and temperature. For the partially irreversible uptake, a fraction of the alcohol was physically absorbed while the other fraction underwent irreversible reaction. For the totally irreversible uptake, the alcohols were completely lost onto the sulfuric acid. The Henry's law solubility constant (H*) was determined from the time-dependent uptake, while the reactive uptake coefficients were calculated from the time-independent irreversible loss. Coexistence of butanol or decanol with octanal or decanal did not show enhanced uptake of the aldehydes in the sulfuric acid. Protonation and dissolution likely account for the reversible uptake, while formation of alkyl sulfate or dialkyl sulfate explains irreversible uptake of the alcohols. The results suggest that heterogeneous uptake of larger alcohols is unlikely of significant importance in the lower atmosphere except in the case of freshly nucleated aerosols that may have high acid concentrations.

Heterogeneous Reactions of Methylglyoxal in Acidic Media: Implications for Secondary Organic Aerosol Formation

Recent environmental chamber studies have suggested that acid-catalyzed particle-phase reactions of organic carbonyls contribute to the formation of secondary organic aerosol (SOA). We report the first measurements of uptake of methylglyoxal on liquid H2SO4 over the temperature range of 250-298 K and acidic range of 55-85 wt %. From the time-dependent uptake the effective Henry's law solubility constant (H*) was determined. Heterogeneous reactions of methylglyoxal are shown to decrease with acidity and involve negligible formation of sulfate esters. Hydration and polymerization likely explain the measured uptake of methylglyoxal on H2SO4 and the measurements do not support an acid-catalyzed uptake of methylglyoxal. The results imply that heterogeneous reactions of methylglyoxal contribute to organic aerosol formation in less acidic media and hydration and polymerization of methylglyoxal in the atmospheric aerosol-phase are dependent on the hygroscopicity, rather than the acidity of the aerosols.

Heterogeneous chemistry of octanal and 2, 4‐hexadienal with sulfuric acid

Recent experimental studies using the environmental chamber have suggested that acid‐catalyzed particle‐phase reactions of organic carbonyls lead to multifold increases in secondary organic aerosol (SOA) mass, but the kinetics and mechanism of the heterogeneous chemistry of carbonyls with sulfuric acid remain largely uncertain. We report the first measurements of heterogeneous uptake of octanal and 2, 4‐hexadienal on liquid H2SO4 in the acid range of 60 to 85 wt % and between 250 and 298 K. Octanal was physically absorbed by sulfuric acid without undergoing irreversible reaction. From the time‐dependent uptake the effective Henry's law solubility constant (H*) was determined. Irreversible reactive uptake was observed for 2, 4‐hexadienal, and the uptake coefficient decreased with decreasing acid concentrations. The uptake of octanal and 2, 4‐hexadienal on liquid H2SO4 is explained by aldol condensation, dependent on acidity. The results suggest that aldol condensation of the aldehydes can be important in the upper troposphere, but may not significantly contribute to secondary organic aerosol formation in the lower troposphere.

Kinetics of the reactive uptake of ozone on oleic acid aerosols

Heterogeneous reactions involving particles and gas-phase species can alter important chemical and microphysical properties of aerosols, complicating modeling efforts to assess their effects on climate and human health. Organic aerosols are common in the troposphere; precursors include vegetation, the ocean surface, and various combustion processes. Ozone is an important oxidant in the troposphere (Finlayson-Pitts and Pitts, 1997), often in concentrations sufficient to cause adverse effects on human health and vegetation. Oleic acid is one of a group of organic species proposed as an important tracer species for use in source characterization of ambient aerosols (Rogge et al., 1991). However, the relative fraction of these species may change as the particle ages, and new product species are likely to be introduced. Little is known about the kinetics of organic species in atmospheric aerosols. Such knowledge is necessary for quantitative assessment of field studies as well as for use in climate models. With this motivation, we have chosen oleic acid (one of the simplest condensed phase organics with atmospheric relevance) as the first species to be used in a series of experiments aimed at investigating the dynamic evolution of the composition and size of organic particles in the presence of ozone. Our experimental setup includes an atmospheric pressure flow reactor, in which oleic acid particles of a pre-selected size are allowed to interact with ozone for a controlled time, coupled to a newly developed aerosol mass spectrometer (AMS), (Jayne et al., 2000), which monitors changes in the size distribution and composition of the aerosols. This AMS/flow reactor system permits a new approach to kinetic studies in that the depletion of the particle-phase reactant (rather than the gas-phase reactant) is monitored. In the present study we report the size dependent rate of reactive uptake of ozone by three different sizes of oleic acid particles. Depletion of oleic acid, appearance of product species, and the growth of particle size are all observed simultaneously. With interaction times from 2 to 11 seconds, a given run takes place at nearly constant ozone concentration. The figure below indicates the fraction of oleic acid remaining in a particle as a function of ozone exposure time. We are developing an uptake model which allows determination of the following fundamental physico-chemical parameters: Henry's Law solubility constant for ozone in oleic acid, H, the liquid phase diffusion coefficient for ozone in oleic acid, D, and the second order rate coefficient for ozone reacting with oleic acid, k 2. The plotted curves show a preliminary fit to the size dependent reaction data, yielding the values shown at 293°K. These parameters allow calculation of the reactive collision probability, γ, which ranges from about 10 −3 to 10 −5 (decreasing with a decrease in oleic acid concentration). Our data also show a dependence in the uptake on the purity of the oleic particles, an increase in viscosity upon reaction, and an increase in particle diameter as the interaction time increases. These effects (including those of secondary reaction of products) are currently being modeled in order to assess aerosol phase oleic acid atmospheric lifetimes.

Heterogeneous Chemistry of Acetone in Sulfuric Acid Solutions: Implications for the Upper Troposphere

The uptake of acetone vapor by liquid sulfuric acid has been investigated over the range of 40−87 wt % H2SO4 and between the temperatures 198 and 300 K. Studies were performed with a flow-tube reactor, using a quadrupole mass spectrometer for detection. At most concentrations studied (40−75 wt %), acetone was physically absorbed by sulfuric acid without undergoing irreversible reaction. However, at acid concentrations at or above 80 wt %, reactive uptake of acetone was observed, leading to products such as mesityl oxide and/or mesitylene. From time-dependent uptake data and liquid-phase diffusion coefficients calculated from molecular viscosity, the effective Henry's law solubility constant (H*) was determined. The solubility of acetone in liquid sulfuric acid was found to increase with increasing acid concentration and decreasing temperature. In the 75 wt % and 230 K range, the value for H* was found to be ∼2 × 106 M/atm. This value suggests that acetone primarily remains in the gas phase rather than absorbing into sulfate aerosols under atmospheric conditions.

Chemistry at and near the Surface of Liquid Sulfuric Acid: A Kinetic, Thermodynamic, and Mechanistic Analysis of Heterogeneous Reactions of Acetone

The interactions of gas-phase acetone with liquid sulfuric acid solutions are described. The solutions were prepared as 0.05−0.10 μm thick films deposited on single-crystal metal substrates. Experiments were carried out over broad ranges of acid composition (70 − >96 wt % H2SO4), temperature (180−220 K), and acetone pressure (10-7−10-3 Pa). Two types of measurements are reported: the time-dependent acetone uptake probability, and the infrared spectra of absorbed acetone and its reaction products. From the infrared measurements, a reaction scheme is identified in which gas-phase acetone is taken up by sulfuric acid to form protonated acetone. In solutions containing more than 70 wt % H2SO4, protonated acetone undergoes a self-condensation/dehydration reaction to form mesityl oxide. In films that contain 85 wt % or more H2SO4, a second reaction sequence occurs, ultimately resulting in the formation of trimethylbenzene. The uptake probability measurements are consistent with the infrared data. In 70 wt % H2SO4, the acetone uptake probability rapidly decreases from an initial value near unity to a steady-state value of zero, due to the formation of a saturated acetone + sulfuric acid solution. The Henry's law solubility constants of acetone in 70 wt % H2SO4 were obtained from the integrated uptake measurements. The temperature dependence of the measurements implies that the standard-state enthalpy and entropy changes of acetone solution in 70 wt % sulfuric acid are −66 kJ mol-1 and −249 J mol-1 K-1, respectively. In the more concentrated films, the steady-state uptake probability is never measured to be zero, since absorbed acetone goes on to form the condensation/dehydration products. A two-step kinetic scheme is proposed to account for the reactions of acetone in sulfuric acid. By fitting the data to the model predictions, the Henry's law solubility constants and the reaction rate constants may be estimated.

Heterogeneous Chemistry of HO2NO2 in Liquid Sulfuric Acid

The interaction of HO2NO2 (peroxynitric acid, PNA) vapor with liquid sulfuric acid was investigated for acid contents ranging from 53 to 74 wt % and at temperatures between 205 and 230 K, using a fast-flow reactor coupled to a chemical ionization mass spectrometer. PNA was observed to be physically taken up by liquid sulfuric acid, without undergoing irreversible aqueous-phase reactions. From the time-dependent uptake, the quantity H* (that is, the product of the effective Henry's law solubility constant and the square root of the liquid-phase diffusion coefficient) was obtained. The effective Henry's law solubility constant H* of PNA in liquid sulfuric acid was derived by estimating the liquid-phase diffusion coefficient based on a cubic cell model. In general, the solubility was found to increase with decreasing acid content and decreasing temperature. The heterogeneous reaction between PNA and HCl in liquid sulfuric acid was also examined and was found to be very slow (γ < 1 × 10-4). The measured solub...

Heterogeneous interaction of peroxyacetyl nitrate with liquid sulfuric acid

The uptake of peroxyacetyl nitrate (PAN) on liquid sulfuric acid surfaces has been investigated using a fast‐flow reactor coupled to a chemical ionization mass spectrometer. PAN was observed to be reversibly adsorbed on sulfuric acid. From the time‐dependent uptake, Henry's law solubility constant of PAN in sulfuric acid was obtained. The measured solubility constant was found to depend strongly on temperature (199–226 K), but weakly on acid composition (46–72 wt%). On 72 wt% H2SO4, for example, the effective Henry's law solubility constant was determined to be about 5.6×104 and 3.1×103 M atm−1 at 208 and 222 K, respectively. Heterogeneous reactions of PAN with HCl, Cl, ClO, and OClO on liquid sulfuric acid were also investigated and found to be very slow (γ&lt;1×10−4). Atmospheric implications of the present results are discussed.

Correlation of the Henry's Law Constants for Nonpolar Liquids in Molten Polyisobutylene

We present here a correlation for the estimation of solubilities of nonpolar solutes in molten polyisobutylene. Experimental solubility data from the literature are well described by the proposed equation ln(1/Kp) = A + B/Tr, where Kp is the Henry's law solubility constant and Tr is the reduced temperature (=T/Tc). The two correlation parameters A and B are generalized by a polynomial expansion of the acentric factor ω and the parachor [P] of the solutes. A total of 115 experimental data points, covering 18 nonpolar substances, is used to determine the proposed correlation. The mean absolute percentage error between experimental and predicted values is 4.4%. This is 2.5% lower than that achieved through use of the presently available generalized method.

HCl vapour pressures and reaction probabilities for ClONO2+ HCl on liquid H2SO4–HNO3–HCl–H2O solutions

Henry's Law solubility constants for HCl have been measured for liquid H2SO4–HNO3–HCl–H2O solutions; the results are in good agreement with predictions from published semiempirical models. The ClONO2+ HCl reaction on the surfaces of such solutions with compositions simulating those of stratospheric aerosols has been investigated; as the composition changes following the temperature drop characteristic of the high-latitude stratosphere the reaction probability γ increases rapidly. Furthermore, the γ values remain essentially unchanged when HNO3 uptake is neglected; the controlling factor appears to be the solubility of HCl. These results corroborate our earlier suggestion that supercooled liquid sulfate aerosols promote chlorine activation at low temperatures as efficiently as solid polar stratospheric cloud particles.

Nitric acid uptake by sulfuric acid solutions under stratospheric conditions: Determination of Henry's law solubility

A Knudsen cell flow reactor is used to study the uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate. Henry's law solubility constants are determined using the time dependence of the measured nitric acid uptake efficiencies. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 weight percent sulfuric acid over a temperature range from 188 to 240 K. In general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and decreasing temperature. Over the reported temperature range the solubilities are cast in the form H* = A exp(B/T), where A = 7.47 × 10−8 M/atm, B = 7.16 × 103 K for 58% H2SO4; A = 0.202 M/atm, B = 3.19 × 103 K for 66% H2SO4; A = 8.54 × 10−3 M/atm, B = 3.55 × 103 K for 74% H2SO4; and A = 3.56 × 10−3 M/atm, B = 3.32 × 103 K for 87% H2SO4. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase. The ratio of condensed to gas phase nitric acid is less than 10−4 even under conditions of highly elevated sulfuric acid loading.

The effect of morphology on sorption and transport of carbon dioxide in a polyimide from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐oxydianiline

AbstractSorption and transport of CO2 have been investigated for polyimide films prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐oxydianilline (ODA) as well as for a chemically identical commercial polyimide film, Upilex‐R. The BPDA‐ODA polyimide films annealed above the glass transition temperature (270°C) are found to have some degree of ordering owing to molecular aggregation of polymer chains, whereas the films as‐cast are amorphous. The solubility, permeability, and diffusion coefficients decrease significantly with increasing density or increasing average degree of molecular aggregation. The influence of morphology on the parameters in the dual‐mode sorption and transport model has also been investigated. With an increase in density, the Langmuir capacity constant and the diffusion coefficients for Henry's law and Langmuir populations decrease by a larger factor than the Henry's law solubility constant. These results can be tentatively interpreted by assuming either a one‐phase or two‐phase structure for these polyimide films.

The effect of morphology on sorption and transport of carbon dioxide in poly(4,4'‐oxydiphenylene pyromellitimide)

AbstractSorption and transport of carbon dioxide were investigated for poly(4,4'‐oxydiphenylene‐pyromellitimide) films (PI‐1, PI‐2, and PI‐3) imidized at 160, 200, and 400°C, respectively, as well as for a chemically identical commercial polyimide film, Kapton‐H. The solubility, permeability, and diffusion coefficients (S, P, and \[ \overline D \] , respectively) at 80°C and 20 atm in PI‐3 were 67, 25, and 37%, respectively, as large as those in PI‐2. These significant reductions are attributed to a higher degree of segmental aggregation in PI‐3 caused by a 1.7% increase in the density (d) as compared with PI‐2. The differences in S, P, \[ \overline D \] , and d between PI‐3 and Kapton‐H were rather small as compared with those between PI‐3 and PI‐2, suggesting that the in‐plane orientation has a minor effect on the sorption and transport in Kapton‐H as compared with the aggregation. Influence of the morphology on the dual‐mode sorption and transport parameters was also investigated. With increasing density, the Langmuir capacity constant and the diffusion coefficients for the Henry's law and Langmuir populations decreased by higher rates than the Henry's law solubility constant, being contrary to the results reported for a typical semicrystalline glassy polymer, polyethylene terephthalate. This may suggest that the nonaggregated or less‐aggregated regions taking an important part in the sorption and transport are denser for the sample having a higher overall density.

Evaluation of the rate of uptake of nitrogen dioxide by atmospheric and surface liquid water

The rate of uptake of NO2by liquid water according to (R1), 2NO2(g) + H2O(1) → 2H++ NO3−+ NO2−, is shown to be unaffected by O2(0.2 atm). Hence the rate constant and Henry's law solubility constant of NO2previously obtained may be employed to evaluate the rates of aqueous phase reactions of NO2in the ambient atmosphere. Reactions (R1) and (R2), NO2(g) + NO(g) + H2O(1) → 2H++ 2NO2−, are quite slow at representative atmospheric partial pressures and cloud liquid water content; the characteristic times range upward from 103–104hours at 10−7atm, increasing with decreasing partial pressures of the gases. Direct acidification of cloud liquid water by (R1) or (R2) is also unimportant. Catalytic enhancement of (R1) is potentially important for catalyst concentrations of order 10−7M, assuming sufficiently fast rate constants (∼108M−ls−1). Iron‐catalyzed reaction in particular, however, is found to be unimportant. Reaction of NO2with dissolved S(IV) is potentially mportant, based upon an assumed upper limit rate constant of 2.5×107M−1s−1. Deposition of NO2to surface (ocean or lake) water is shown to be controlled by aqueous phase mass transport and/or reaction and is much slower than heretofore assumed.