Henry's Law Constants Research Articles

Cuprous‐based composite ionic liquids for the selective absorption of CO: Experimental study and thermodynamic analysis

AbstractThree cuprous‐based composite ionic liquids (ILs) [EimH][OAc]–xCuOAc (x = 0.5, 0.6, 0.7) were prepared and employed for efficient absorption of CO. It is shown that the cuprous composite IL [EimH][OAc]–0.6CuOAc exhibited the largest absorption capacity for CO (0.031 g/g at 293.15 K and 1 bar) and had a record CO/N2 selectivity of 967, which is better than most of common ILs and solvents reported in the literature. The results of Fourier transform infrared (FTIR) spectra, electrospray ionization mass spectrometry (ESI‐MS) analysis, and theoretical calculations reveal that such superior CO capacity mainly resulted from two kinds of chemical interaction between CO and the active anionic species [Cu(OAc)2]− in [EimH][OAc]–0.6CuOAc. Furthermore, a “deactivated IL model” was further proposed to accurately describe the absorption behavior of CO in [EimH][OAc]–0.6CuOAc, in which the thermodynamic parameters including Henry's law constants, reaction equilibrium constants, and absorption enthalpies were estimated by the correlation of the experimental solubilities of CO.

A source for the continuous generation of pure and quantifiable HONO mixtures

Abstract. A continuous source for the generation of pure HONO mixtures was developed and characterized, which is based on the Henry's law solubility of HONO in acidic aqueous solutions. With the help of a peristaltic pump, diluted nitrite and sulfuric acid solutions are mixed in a temperature-controlled stripping coil, which is operated with pure nitrogen or synthetic air at gas flow rates of 0.5–2 L min−1. Caused by the acidic conditions of the aqueous phase (pH ≈ 2.5), nitrite is almost completely converted into HONO, which partitions to the gas phase limited by its known solubility in water. The source shows a fast time response of ∼ 2 min (0 %–90 %) at higher concentrations and an excellent long-term stability (2σ noise < 1 %). The HONO emission of the source perfectly correlates with the nitrite concentration from the sub-ppb range up to 500 ppb. The rate of NOx formation increases quadratically with the HONO concentration from non-detectable values at atmospheric relevant HONO concentrations reaching a NOx content of 1.6 % at 500 ppb. A general equation based on Henry's law is developed, whereby the HONO concentration of the source can be calculated using measured experimental parameters, i.e. nitrite concentration, liquid flow rates, gas flow rate, pH of the solution, and temperature of the stripping coil. In the equation, the known Henry's law constant of HONO in sulfuric acid solutions is used. For the calculation of the effective Henry's law constant, the acid dissociation equilibrium of HONO / nitrite is used as a variable to adjust the theoretical HONO concentration to the measured values. From the average of all experimental data the equilibrium of HONO / nitrite is described well by pKa=1021.53/T-0.449. The pKa of 3.0 ± 0.1 (1σ) at 25 ∘C is in good agreement with the range of 2.8–3.28 published in former studies. A standard deviation between all measured and theoretical HONO concentrations of only ±3.8 % was observed, and a conservative upper-limit accuracy of the HONO concentration of better 10 % is estimated. Thus, for the first time, a stable HONO source is developed which can be used for the absolute calibration of HONO instruments.

Photoinduced release of odorous volatile organic compounds from aqueous pollutants: The role of reactive oxygen species in increasing risk during cross-media transformation

Photoinduced volatile organic compounds (VOCs) release from fatty alcohols at the air-water interface, has attracted considerable attention. This paper comprehensively explores the release of odorous VOCs from aqueous micropollutants under photoirradiation, especially in terms of the important role of the reactive oxygen species (ROS) in increased risk by cross-media transformation. The formation and distribution of photoinduced VOCs produced by aqueous benzyl alcohol (BzOH), a common ingredient in personal care products, were monitored in situ by online gas chromatography equipped with mass spectrometry and flame ionization detector (GC–MS/FID). The photoreaction of BzOH followed first-order kinetics with a rate constant of 0.0158/min under air. After 180 min of ultraviolet irradiation, the accumulated output of the gas-phase products benzene and benzaldehyde (BA) reached 3.8 μmol and 2.6 μmol respectively, being approximately 10 times that under nitrogen. According to electron paramagnetic resonance measurements, singlet oxygen mainly promoted the oxidation of BzOH to BA, which was an important intermediate producing benzene via photocleavage. Odorous alicyclic hydrocarbons were also generated through photorearrangement under nitrogen. On the other hand, the Henry's law constants of the main products were much lower than those of BzOH, indicating that the photoproducts would volatilize from the aqueous phase into the gas phase. The odor threshold of gas-phase products decreased to varying degrees after photoirradiation. Especially for BA, one of the main products, its odor threshold decreased 130 times compared with BzOH. This study shows that the risk of cross-media pollution could significantly increase due to the transformation of aqueous pollutants into odorous VOCs under photoirradiation and provides new insight into its risk prevention.

CO2 absorption/desorption rates in aqueous DEEA/MDEA and sulfolane-contained hybrid solutions: effects of physical properties and reaction rate.

The rates of CO2 absorption into fresh and regenerated aqueous solutions of N,N-diethylethanolamine (DEEA), N-methyldiethanolamine (MDEA), and their mixture with sulfolane are investigated in a batch stirred cell reactor. The data are obtained in the temperature range of 293.15-313.15K, pressures up to 800kPa, and different concentrations of alkanolamines and sulfolane. The diffusion coefficients and Henry's law constants for all the solutions are obtained. The absorption rate of DEEA solutions increased by increasing component concentrations and pressure, but the effects of temperature on the absorption rates of hybrid and aqueous DEEA solutions are different. Comparison of absorption rates in aqueous and hybrid solutions under the same conditions can determine the role of sulfolane as the physical solvent. It has been found that sulfolane acts as an effective absorption activator in the hybrid DEEA solutions. However, in the MDEA solutions, in all experimental conditions except for high pressure ([Formula: see text] 400kPa) and certain MDEA concentration (20 wt%), sulfolane has a negative effect on the absorption rate. The absorption rates of regenerated aqueous DEEA solutions are in the range of 50.5-87.7% of fresh ones, while these values for the hybrid DEEA solution are in the range of 75-90.5%. These values for the aqueous and hybrid MDEA solutions are almost equal. Based on the values of Hatta number and enhancement factor, the CO2 absorption regime in the DEEA solutions is determined as the fast second-order reaction. The absorption rate can be interpreted considering the tradeoff between kinetics and thermodynamics of CO2 absorption in the aqueous and hybrid DEEA/MDEA solutions. The desorption rates in hybrid DEEA/MDEA solutions are higher than those in aqueous solutions.

A fuzzy knowledge-based model for assessing risk of pesticides into the air in cropping systems

Pesticide use in current cropping systems has become a key input to improve productivity. However, their potential risk to nature demands tools for designing a sustainable use. In this work, a fuzzy knowledge-based model was developed for assessing risk of pesticides into the air. The model was based on fuzzy logic theory which provides a means for representing uncertainty by including knowledge about different processes related to pesticide dynamics using functions, control rules and logical inference systems. All these elements were built through a literature review. Results from the sensitivity analysis on the final model structure showed that the Henry's law constant was the most influential input variable related to the active ingredient identity, while the most influential management and environmental input variables on the pesticide air risk values were the droplet size together with the application method and the current wet bulb temperature depression value, respectively. Results from an independent model validation showed a significant goodness-of-fit between the simulated risk of drift and volatilization and the observed values under experimental conditions. Long-term simulations in a real soybean production system in Argentina showed results of drift reduction in post-emergence conditions of the crop under aerial application condition, and a significant effect of the identity of the active ingredient in the risk values. Simulated risk values from the developed model allow to identify ex ante the combination of agronomic decisions, together with environmental conditions that can reduce the risk of pesticides in the air in real production systems. Further combination with ecotoxicological classification tools should improve pesticide use assessment in agricultural systems.

User-assisted methodology targeted for building structure interpretable QSPR models for boosting CO2 capture with ionic liquids

Task-specific ionic liquid (IL) is an emerging class of compounds that may be environmentally friendly. Properly selected, these compounds may be green alternative to amine solutions and can replace them in post-combustion carbon dioxide (CO2) capture processes on an industrial scale. However, owing to the vast diversity of ions and their possible combinations, laboratory research is time consuming and expensive. Therefore, computational methods are preferred for assessing their potential applications. In this study, three quantitative structure–property relationship models based on six distinct descriptors were created to predict Henry’s law constant (HLC) of CO2 in 62 ILs. The statistical parameters of multiple linear regression, logistic regression, and partial least squares models were satisfactory. In all cases, the coefficients of determination (R2) exceeded 0,90, and both external and internal validation proved them to be reliable and predictive with Q2 and Rpred2 values exceeding 0,90 and 0,87, respectively. Three of the descriptors were attributed to cations, and three were attributed to anions. In contrast to many other models, the descriptors were chosen in a manner that ensured their interpretability. Each of the six descriptors was analyzed for its influence on HLC. On this basis, guidelines for designing the structure of ionic liquids with increased CO2 absorption capacity were developed.

Solubility of carbon dioxide and ethane in Lloydminster heavy oil: Experimental study and modelling

AbstractHeavy oil reserves in the world represent 5.5 trillion barrels, which are equivalent to five times the conventional crude oil reserves. Heavy oil reserves will be the main petroleum source for the world's future demand for energy. To enhance the recovery of heavy oil/bitumen, solvent‐based recovery seems to be one of the most promising alternatives to costly thermal methods. Phase behaviour studies of light gases in heavy oil are therefore very important when designing surface facilities and for enhanced oil recovery operations. In this study, we present solubility data for carbon dioxide and ethane in Lloydminster heavy oil. Measurements were carried out using a microbalance at 290.2, 298.2, and 313.2 K and at pressures varying from 200–2000 kPa. Experimental data were regressed with the Peng‐Robinson (PR) equation of state. We also report results of the fractionation of the heavy oil and its characterization in terms of SARA (saturates, aromatics, resins, and asphaltenes) fractions. Henry's law constants for gaseous solvents were also regressed and reported. As expected, ethane had a higher solubility than CO2 in the heavy oil at all temperatures.

Noble gas adsorption to tuff

A method was developed to measure trace noble gas element adsorption to the surfaces of geologic materials in the presence of a background gas that could potentially compete for surface adsorption sites. Adsorption of four noble gas elements (Ne, Ar, Kr, and Xe) at a concentration of 100 ppm in helium and nitrogen were measured on a sample of crushed tuff at 0, 15, 30, and 45 °C. In addition, Ne, Ar, Kr, and Xe at 250 ppm and 500 ppm in nitrogen at 15 °C were measured. Noble gas adsorption was found to increase with increasing atomic mass and decreasing temperature. It was also observed that the relative increase in noble gas element adsorption with decreasing temperature tends to increase with increasing atomic mass. As the noble gas concentrations in nitrogen increased, adsorption increased in a slightly non-linear fashion which could be modeled using a Freundlich isotherm. For noble gas concentrations that were ≤100 ppm Henry's Law constant were calculated.

COSMO‐RS as an effective tool for predicting the physicochemical properties of fragrance raw materials

AbstractA predictive tool called COSMO‐RS, Conductor‐Like Screening Model for Real Solvents, based on quantum chemistry, dielectric continuum models, electrostatics surface interactions, and statistical thermodynamics, has been used to predict five key physicochemical properties of raw materials used in perfumery industries. The prediction of boiling point (BP), octanol‐water partition coefficient (logP), vapor pressure (VP), water solubility (WS), and Henry's law constant (HLC) of fragrance molecules has been validated with a reference data set of 166 organic compounds. Knowing these properties for a fragrance molecule is essential and being able to predict them precisely can be particularly useful in the development of new molecules or in the replacement of controversial molecules regarding safety issues without compromising the overall hedonic accord. Finally, mapping the vapor pressureversusthe Henry's law constant and the octanol‐water partition coefficient consistently predicts the note class of the molecules useful for release comparison of captives.

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.

Estimated timescales for wet deposition of organic compounds as a function of Henry's law constants

Precipitation frequency and duration rather than intensity drive most of the differences in wet deposition between sites.

Box Model Intercomparison of Cloud Chemistry

AbstractChemical processes in clouds and fogs can substantially alter atmospheric oxidant budgets and lead to aerosol mass formation. However, many regional and global models do not include detailed aqueous‐phase chemical mechanisms due to the (a) lack of complete understanding of the chemical processes and (b) computational burden of adding constituents. Current gas‐aqueous chemistry 0‐dimensional models were evaluated in a cloud‐chemistry box model intercomparison based on a mid‐September 2016 cloud chemistry event at Whiteface Mountain, New York. Multiphase mechanisms in the five participating models ranged from those appropriate for 3‐d models to highly complex with thousands of reactions. This study focused on oxidant levels in both phases and aqueous‐phase sulfate and organic acid formation. Comparison of gas‐phase‐only chemistry gives very similar oxidant predictions at night but shows significant differences during daytime with the hydroxyl radical (OH) variability of about an order of magnitude. The variability in the model results increases substantially with aqueous chemistry due to different Henry's Law constants, aqueous‐phase reaction rate constants, and chemical mechanisms. Using a prescribed liquid water content and pH value of 4.5, modeled aqueous OH, aldehyde, and organic acid concentrations differ by over an order of magnitude in daytime. Simulations were also conducted at a pH = 5.1, predicted variable pH, and with added transition metal ion chemistry. While we compare predicted and measured inorganic anions and water‐soluble organic carbon, we cannot do so for aqueous‐phase oxidant concentrations due to the lack of measurements. We highlight a need for recommended equilibrium and aqueous‐phase rate constants.

Behavior of KCl sorbent traps and KCl trapping solutions used for atmospheric mercury speciation: stability and specificity

Abstract. Atmospheric mercury speciation is of paramount importance for understanding the behavior of mercury once it is emitted into the atmosphere as gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM). GOM and PBM can also be formed in the atmosphere; their sampling is the most problematic step in the atmospheric mercury speciation. GOM sampling with speciation traps composed of KCl sorbent materials and KCl trapping solutions are commonly used sampling methods, although the research conducted with them at ambient air concentrations is limited. The results of the specificity test demonstrated that the KCl sorbent traps are highly specific when using new traps, while their specificity drops dramatically when they are reused. The results of the stability test indicated that the highest Hg2+ losses (up to 5.5 % of Hg2+ loss) occur when low amounts of Hg2+ (< 1 ng) are loaded, due to a reduction of Hg2+ to Hg0. KCl trapping solutions have also been considered as a selective trapping media for GOM in atmospheric samples. A dimensionless Henry law constant was experimentally derived and was used to calculate the solubility of elemental Hg in KCl solution. The degree of GEM oxidation was established by purging elemental Hg calibration gas into a KCl solution and determining the GOM trapped using aqueous-phase propylation liquid–liquid extraction and gas chromatography–atomic fluorescence spectrometry (GC-AFS) measurement. A positive GOM bias was observed due to the solubility and oxidation of GEM in KCl trapping solutions, strongly suggesting that this approach is unsuitable for atmospheric mercury speciation measurements.

Extension of a gaseous dry deposition algorithm to oxidized volatile organic compounds and hydrogen cyanide for application in chemistry transport models.

The dry deposition process refers to flux loss of an atmospheric pollutant due to uptake of the pollutant by the Earth’s surfaces, including vegetation, underlying soil, and any other surface types. In chemistry transport models (CTMs), the dry deposition flux of a chemical species is typically calculated as the product of its surface layer concentration and its dry deposition velocity (Vd); the latter is a variable that needs to be highly empirically parameterized due to too many meteorological, biological, and chemical factors affecting this process. The gaseous dry deposition scheme of Zhang et al. (2003) parameterizes Vd for 31 inorganic and organic gaseous species. The present study extends the scheme of Zhang et al. (2003) to include an additional 12 oxidized volatile organic compounds (oVOCs) and hydrogen cyanide (HCN), while keeping the original model structure and formulas, to meet the demand of CTMs with increasing complexity. Model parameters for these additional chemical species are empirically chosen based on their physicochemical properties, namely the effective Henry’s law constants and oxidizing capacities. Modeled Vd values are compared against field flux measurements over a mixed forest in the southeastern US during June 2013. The model captures the basic features of the diel cycles of the observed Vd. Modeled Vd values are comparable to the measurements for most of the oVOCs at night. However, modeled Vd values are mostly around 1 cm s−1 during daytime, which is much smaller than the observed daytime maxima of 2–5 cm s−1. Analysis of the individual resistance terms and uptake pathways suggests that flux divergence due to fast atmospheric chemical reactions near the canopy was likely the main cause of the large model–measurement discrepancies during daytime. The extended dry deposition scheme likely provides conservative Vd values for many oVOCs. While higher Vd values and bidirectional fluxes can be simulated by coupling key atmospheric chemical processes into the dry deposition scheme, we suggest that more experimental evidence of high oVOC Vd values at additional sites is required to confirm the broader applicability of the high values studied here. The underlying processes leading to high measured oVOC Vd values require further investigation.

Competition of Partitioning and Reaction Controls Brown Carbon Formation from Butenedial in Particles.

Organic reactions in atmospheric particles impact human health and climate, such as by the production of brown carbon. Previous work suggests that reactions are faster in particles than in bulk solutions because of higher reactant concentrations and pronounced surface-mediated processes. Additionally, dialdehydes may have accelerated reactions in particles, as has been shown for the glyoxal reaction with ammonium sulfate (AS). Here, we examine the competition between evaporation and reaction of butenedial, a semivolatile dialdehyde, and reduced nitrogen (NHX) in bulk solutions and levitated particles with mass spectrometry (MS). Pyrrolinone is the major product of butenedial/AS bulk solutions, indicating brown carbon formation via accretion reactions. By contrast, pyrrolinone is completely absent in all MS measurements of comparable levitated particles suspended in a pure N2 stream. Pyrrolinone is only produced in levitated butenedial particles exposed to gas-phase ammonia, without enhanced reaction kinetics previously observed for glyoxal and other systems. Despite butenedial's large Henry's law constant and fast reaction with NHX compared to glyoxal, the brown carbon pathway competes with evaporation only in polluted regions with extreme NHX. Therefore, accurate knowledge of effective volatilities or Henry's law constants for complex aerosol matrices is required when chemistry studied in bulk solutions is extrapolated to atmospheric particles.

Modeling the Removal of Water-Soluble Trace Gases from Indoor Air via Air Conditioner Condensate

Water-soluble trace gas (WSTG) loss from indoor air via air conditioning (AC) units has been observed in several studies, but these results have been difficult to generalize. In the present study, we designed a box model that can be used to investigate and estimate WSTG removal due to partitioning to AC coil condensate. We compared the model output to measurements of a suite of organic acids cycling in an indoor environment and tested the model by varying the input AC parameters. These tests showed that WSTG loss via AC cycling is influenced by Henry's law constant of the compound in question, which is controlled by air and water temperatures and the condensate pH. Air conditioning unit specifications also impact WSTG loss through variations in the sensible heat ratio, the effective recirculation rate of air through the unit, and the timing of coil and fan operation. These findings have significant implications for indoor modeling. To accurately model the fate of indoor WSTGs, researchers must either measure or otherwise account for these unique environmental and operational characteristics.

CO2 absorption in amino acid-based ionic liquids: Experimental and theoretical studies

In this study, eight amino acid-based ionic liquids (AAILs) with 1-butyl-4-methyl pyridinium cation ([B4MPyr][AA]s) were synthesized and characterized. The CO2 absorption capacity of AAILs was studied using quartz crystal microbalance (QCM) at pressures up to 6 bars and at temperature 298.15 K. Based on the “deactivated model”, the reaction equilibrium constant and Henry's law constant were calculated to evaluate the efficiency of AAILs for CO2 absorption. The results indicate that CO2 absorption capacities are in the order of [Arg] > [Lys] > [His] > [Tyr] > [Gly] > [Val] > [Ala] > [Pro]. The accessibility of more available amine groups in AAIL with arginate anion is the main factor for the high CO2 absorption capacity. Also, the chemical absorption of CO2 through carbamate formation was corroborated by spectroscopy of FT-IR. Beside, the density functional theory (DFT) method was also employed to confirm the adsorption energy of CO2 onto AAILs with various anions.

Role of ecosystem-atmosphere exchanges of semi-volatile organic compounds in organic aerosol formation

Deposition of the gas fraction of Semi-Volatile Organic Compounds (SVOC) may be an important removal pathway and may strongly influence concentrations of organic aerosols due to the gas-particle partitioning of SVOC. All the studies on this process are based on the classic Wesely resistance approach that uses Henry's law constants to calculate a deposition rate scaled on the deposition rate of SO2. However, even highly hydrophobic SVOC could be efficiently removed by the vegetation and soils as shown by numerous studies on Persistent Organic Pollutant (POP) modeling. Moreover, the re-volatilization of deposited SVOC is possible and could influence organic aerosol concentrations.An atmosphere-soil-vegetation module was developed and implemented in the 3D air quality model CHIMERE 2017β to represent the accumulation of compounds in the different compartments of the biosphere and the exchanges between them. The soil compartment was represented with a multi-layer approach (the layers corresponding to different in-soil depths) to simulate the multiphase diffusion of compounds inside the soil. Exchanges of SVOC between the air, soil and vegetation compartments were simulated using bi-directional approaches based on Rg (the gas-phase partitioning in the soil compartment) and Kva the vegetation-air partitioning coefficient. Parameters were estimated based on the physical properties of the compounds and their molecular structure.Simulations performed over Europe show that air-vegetation-soil exchanges may be a more efficient removal pathway than dry deposition of particles for SVOC with a gas-phase fraction above 10%. Considering air-vegetation-soil exchanges in the simulations lead to a decrease of organic aerosol concentrations by 15% and primary SVOC (considered as hydrophobic compounds) may be efficiently removed by those pathways (contrary to what is calculated with the Wesely approach). This decrease of concentrations is mainly due to air-vegetation exchanges. During summer, the use of the Wesely approach may lead to a slight overestimation of deposition fluxes (leading to an underestimation of concentration by 1%).Re-volatilization may limit the amount of deposited SVOC. Depending on assumptions, simulations showed that re-emissions (inversion of exchanges toward the emissions) in summer of SVOC accumulated during winter is theoretically possible and may be a minor source of organic aerosol.

Effect of Methane, CO2, and H2S on the Solubility of Methyl and Ethyl Mercaptans in a 25 wt % Methyldiethanolamine Aqueous Solution at 333 and 365 K

We have investigated the solubility of methanethiol and ethanethiol (methyl and ethyl mercaptans in an aqueous methyldiethanolamine solution (25 wt%) by using static-analytic method at 333 and 365K. The measurements were done for different pressure of methane in the absence of acid gas with individual acid gas present, and with mixture of acid gases present (CO2 and/with H2S). Additional measurement of Henry's law constant were realized by considering gas stripping method. Effect of total pressure (realized by addition of methane) and effect of acid gas loading for a constant total pressure around 7 MPa were studied. The increasing of pressure and acid gas loading increase the apparent Henry's law constant of the mercaptan, highlighting a drop out effect of the mercaptans.

Heterogeneous interactions between SO<sub>2</sub> and organic peroxides in submicron aerosol

Abstract. Atmospheric models often underestimate particulate sulfate, a major component in ambient aerosol, suggesting missing sulfate formation mechanisms in the models. Heterogeneous reactions between SO2 and aerosol play an important role in particulate sulfate formation and its physicochemical evolution. Here we study the reactive uptake kinetics of SO2 onto aerosol containing organic peroxides. We present chamber studies of SO2 reactive uptake performed under different relative humidity (RH), particulate peroxide contents, peroxide types, and aerosol acidities. Using different model organic peroxides mixed with ammonium sulfate particles, the SO2 uptake coefficient (γSO2) was found to be exponentially dependent on RH. γSO2 increases from 10−3 at RH 25 % to 10−2 at RH 71 % as measured for an organic peroxide with multiple O–O groups. Under similar conditions, the kinetics in this study were found to be structurally dependent: organic peroxides with multiple peroxide groups have a higher γSO2 than those with only one peroxide group, consistent with the reactivity trend previously observed in the aqueous phase. In addition, γSO2 is linearly related to particle-phase peroxide content, which in turn depends on gas–particle partitioning of organic peroxides. Aerosol acidity plays a complex role in determining SO2 uptake rate, influenced by the effective Henry's Law constant of SO2 and the condensed-phase kinetics of the peroxide–SO2 reaction in the highly concentrated aerosol phase. These uptake coefficients are consistently higher than those calculated from the reaction kinetics in the bulk aqueous phase, and we show experimental evidence suggesting that other factors, such as particle-phase ionic strength, can play an essential role in determining the uptake kinetics. γSO2 values for different types of secondary organic aerosol (SOA) were measured to be on the order of 10−4. Overall, this study provides quantitative evidence of the multiphase reactions between SO2 and organic peroxides, highlighting the important factors that govern the uptake kinetics.