Gas-phase Concentrations Research Articles

Fluxes of Polychlorinated Biphenyls Volatilizing from the Hudson River, New York Measured Using Micrometeorological Approaches

This study represents the first time that a micrometeorological technique, using turbulent transport measurements, has been used to determine the direction and magnitude of air-water exchange of polychlorinated biphenyls (PCBs). The study was conducted during July 2008 on the Hudson River estuary near the Tappan Zee Bridge, which is the site of some of the most serious PCB contamination in the world. Gas-phase ΣPCB concentrations measured at two heights above the water column averaged 1.1 ng m(-3), and concentrations were usually lower in the upper air sample, indicating net transport of PCBs from the water column to the air. Volatilization PCB fluxes were calculated using the modified Thornthwaite-Holzman equation. Values of friction velocity and atmospheric stability were calculated using the Aerodynamic Gradient and Eddy Correlation techniques. The PCB fluxes were corrected for changes in atmospheric stability using the atmospheric stability factor of water vapor (ϕ(w)) calculated from empirical formulations which ranged from 1.0 to 3.2 (neutral to stable atmospheric boundary layer conditions). Vertical ΣPCB fluxes ranged from +0.5 μg m(-2) d (-1) to +13 μg m(-2) d (-1). Mono- through tri-homologues accounted for about half of ΣPCB fluxes, with tetra- through hexa-homologue accounting for the other half. This work demonstrates the utility of a micrometeorological approach to measuring the air-water exchange of organic contaminants.

Influence of Temperature on the Emission of Di-(2-ethylhexyl)phthalate (DEHP) from PVC Flooring in the Emission Cell FLEC

Emissions of di-(2-ethylhexyl) phthalate (DEHP) from one type of polyvinylchloride (PVC) flooring with approximately 13% (w/w) DEHP as plasticizer were measured in the Field and Laboratory Emission Cell (FLEC). The gas-phase concentrations of DEHP versus time were measured at air flow rate of 450 mL·min(-1) and five different temperatures: 23 °C, 35 °C, 47 °C, 55 °C, and 61 °C. The experiments were terminated two weeks to three months after steady-state was reached and the interior surface of the FLECs was rinsed with methanol to determine the surface concentration of DEHP. The most important findings are (1) DEHP steady-state concentrations increased greatly with increasing temperature (0.9 ± 0.1 μg·m(-3), 10 ± 1 μg·m(-3), 38 ± 1 μg·m(-3), 91 ± 4 μg·m(-3), and 198 ± 5 μg·m(-3), respectively), (2) adsorption to the chamber walls decreased greatly with increasing temperature (measured partition coefficient between FLEC air and interior surface are: 640 ± 146 m, 97 ± 20 m, 21 ± 5 m, 11 ± 2 m, and 2 ± 1 m, respectively), (3) gas-phase DEHP concentration in equilibrium with the vinyl flooring surface is close to the vapor pressure of pure DEHP, and (4) with an increase of temperature in a home from 23 to 35 °C, the amount of DEHP in the gas- and particle-phase combined is predicted to increase almost 10-fold. The amount in the gas-phase increases by a factor of 24 with a corresponding decrease in the amount on the airborne particles.

Amorphous silicon-germanium (a-Si0.01Ge0.99:H) doped with phosphorous deposited by LF PECVD and its electrical and optical characteristics

ABSTRACTAmorphous silicon-germanium (a-Si0.01Ge0.99:H) thin film, practically amorphous germanium with small concentration of silicon, were deposited by the low frequency PECVD technique under different flow gas of phosphine in the range of QPH3 = 20 to 100 sccm. In this range the phosphorous concentration in gas phase was calculated as XP= 4 to 20 % which resulted in a content in solid phase [P]sol=0.12% - 0.4%. The P content of the solid phase was measured by SIMS profiling and it was also observed a preferential incorporation of phosphorous in the range of [P]sol=0.12% - 0.3%. Hydrogen concentration in the films was determined from FTIR and SIMS measurements. The activation energy was determined by measuring the temperature dependence of conductivity in DC regime in a vacuum thermostat. For the a-Si0.01Ge0.99:H films it is found that the activation energy have a minimum, (Ea= 0.15eV), its conductivity at room temperature have a maximum and there is a minimum of of both band tail and deep localized state for a phosphorous incorporation in solid phase [P] =0.28%.

Seasonal Variation and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor and Outdoor Air in a Semi Arid Tract of Northern India

PAHs concentration in particulate and gas phase was investigated in indoor and outdoor air of urban residential and roadside homes in a semiarid region of India. Samples were collected during winter and summer season (Nov 2006–Jun 2007). In particulate phase at roadside homes the annual mean concentration of PAHs in indoor was 5.53 to 952.28 ng/m 3

Distributions, Sources, and Backward Trajectories of Atmospheric Polycyclic Aromatic Hydrocarbons at Lake Small Baiyangdian, Northern China

Air samples were collected seasonally at Lake Small Baiyangdian, a shallow lake in northern China, between October 2007 and September 2008. Gas phase, particulate phase and dust fall concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured using a gas chromatograph-mass spectrometer (GC-MS). The distribution and partitioning of atmospheric PAHs were studied, and the major sources were identified; the backward trajectories of air masses starting from the center of Lake Small Baiyangdian were calculated for the entire year. The following results were obtained: (1) The total concentration of 16 priority controlled PAHs (PAH16) in the gas phase was 417.2 ± 299.8 ng·m−3, in the particulate phase was 150.9 ± 99.2 ng·m−3, and in dust fall was 6930.2 ± 3206.5 ng·g−1. (2) Vehicle emission, coal combustion, and biomass combustion were the major sources in the Small Baiyangdian atmosphere and accounted for 28.9%, 45.1% and 26.0% of the total PAHs, respectively. (3) Winter was dominated by relatively greater PAHs polluted northwesterly air mass pathways. Summer showed a dominant relatively clean southern pathway, whereas the trajectories in autumn and spring might be associated with high pollution from Shanxi or Henan province.

Prediction of gas-particle partitioning of polycyclic aromatic hydrocarbons based on M5' model trees

During the thermal combustion processes of carbon-enriched organic compounds, emission of polycyclic aromatic hydrocarbons into ambient air occurs. Previous studies of atmospheric distribution of polycyclic aromatic hydrocarbons showed low correlation between the experimental values and Junge-Pankow theoretical adsorption model, suggesting that other approaches should be used to describe the partitioning phenomena. The paper evaluates the applicability of multivariate piece-wise-linear M5' model-tree models to the problem of gas-particle partitioning. Experimental values of particle-associated fraction, obtained for 129 ambient air samples collected at 24 background, urban, and industrial sites, were compared to the prediction results obtained using M5' and the Junge-Pankow model. The M5' approach proposed and models learned are able to achieve good correlation (correlation coefficient >0.9) for some low-molecular-weight compounds, when the target is to predict the concentration of gas phase based on the particle-associated phase. When converted to particle-bound fraction values, the results, for selected compounds, are superior to those obtained by Junge-Pankow model by several orders of magnitude, in terms of the prediction error. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/TSCI121205224E">10.2298/TSCI121205224E</a><u></b></font>

Chemical Kinetics of Photoinduced Chemical Vapor Deposition: Silica Coating of Gas-Phase Nanoparticles

Experimental studies of gas-phase nanoparticle coating by photoinduced chemical vapor deposition (photo-CVD) have shown that silica coatings can be produced with controllable thicknesses on different nanoparticle cores for a variety of applications. This study presents a chemical reaction sequence for the photo-CVD process to describe the production of silica coatings from the decomposition of tetraethyl orthosilicate (TEOS). The model incorporates photochemical reactions into known thermal reaction sequences involving gas-phase and surface reactions to describe the nanoparticle coating process. Modeled results of the photo-CVD process indicate that the dominant reactions for the production of silica coatings on the surface of the nanoparticles are the photodecomposition of TEOS and the removal of surface ethyl groups from adsorbed TEOS species. Relative concentrations of gas-phase and surface species are compared for different model configurations and system parameters. Modeled coating thicknesses agree ...

Dioxin inhalation doses from wood combustion in indoor cookfires

Approximately 3 billion people worldwide rely on solid biomass fuels for household cooking and space heating, and approximately 50–60% use wood, often indoors in poorly ventilated situations. Daily exposures to high concentrations of smoke from cookstoves inside kitchens create large smoke exposures for women cooks and their small children. The smoke from burning the wood fuel contains hundred of toxic compounds, including dioxins and furans some of the most toxic compounds known to science. Health effects from exposure to dioxins include reproductive and developmental problems, damage the immune system, interference with hormones and also cause cancer. This study measured concentrations of dioxins and furans in a typical Guatemalan village home during open cookfires. Measured concentrations averaged 0.32 ± 0.07 ng m −3 over 31 fires. A Monte Carlo simulation was conducted using parameter estimates based on 8 years of research experience in the study area. The estimated total daily intake of 17 particle phase dioxin and furans for women, a 5-year-old child and a 6-month-old infant were 1.2 (S.D. = 0.4), 1.7 (S.D. = 0.7) and 2.0 (S.D. = 0.5) respectively. The 46% of babies have and estimated total daily intake (TDI) which exceed the WHO TDI guideline for dioxins and furans, 3% of women and 26% of 5-year-old children based solely inhalation of particle phase dioxins in woodsmoke from an open cooking fire. These values maybe underestimates, as they did not include gas phase concentrations or ingestion of dioxins and furans through food, which is the largest route of exposure in the developed world.

Experimental Investigation of the Effect of Calcium Lignosulfonate on Adsorption Phenomenon in Surfactant Alternative Gas Injection

Fractional flow analysis confirms the advantages of surfactant alternative gas injection (SAG) in enhanced oil recovery, but an adsorption phenomenon that has been affected by several factors, weakens the effectiveness of SAG injection. In this study, the effects of sacrificial agent, gas phase, and surfactant concentration on adsorption density on silica mineral were investigated by static and dynamic adsorption experiments. A series of SAG tests were performed to examine the effect of injection rates and presence of Calcium Lignosulfonate (CLS) on oil recovery. Also, variation of effluent sodium dodecyl sulfate (SDS) concentration during SAG test was examined. Spectrophotometric method based on the formation of an ion-pair was used in all experiments for determination of SDS concentration. The results of adsorption experiments show that SDS adsorption density on silica was reduced when nitrogen was imposed instead of using methane. It can be reduced with addition of CLS as sacrificial agents and amount of adsorption reduction increases as concentration increases. Flooding experiment results show that SAG injection increase ultimate recovery up to 10% in comparison with water alternative gas (WAG) injection. Increasing viscosity of gas phase and its trapping in porous media results a decrease in the mobility of gas and an increase in oil recovery. Stability of formed foam in porous media is rate-depended and higher SDS adsorption was observed at first cycle of SAG injection due to high solid/liquid interaction. Using CLS slightly increases the ultimate oil recovery, while it decreases the adsorption density of SDS about 22 percent during the SAG test.

Illustrating the benefit of using hourly monitoring data on secondary inorganic aerosol and its precursors for model evaluation

Abstract. Secondary inorganic aerosol, most notably ammonium nitrate and ammonium sulphate, is an important contributor to ambient particulate mass and provides a means for long range transport of acidifying components. The modelling of the formation and fate of these components is challenging. Especially, the formation of the semi-volatile ammonium nitrate is strongly dependent on ambient conditions and the precursor concentrations. For the first time an hourly artefact free data set from the MARGA instrument is available for the period of a full year (1 August 2007 to 1 August 2008) at Cabauw, the Netherlands. This data set is used to verify the results of the LOTOS-EUROS model. The comparison showed that the model underestimates the SIA levels. Closer inspection revealed that base line values appear well estimated for ammonium and sulphate and that the underestimation predominantly takes place at the peak concentrations. For nitrate the variability towards high concentrations is much better captured, however, a systematic relative underestimation was found. The model is able to reproduce many features of the intra-day variability observed for SIA. Although the model captures the seasonal and average diurnal variation of the SIA components, the modelled variability for the nitrate precursor gas nitric acid is much too large. It was found that the thermodynamic equilibrium module produces a too stable ammonium nitrate in winter and during night time in summer, whereas during the daytime in summer it is too unstable. We recommend to improve the model by verification of the equilibrium module, inclusion of coarse mode nitrate and to address the processes concerning SIA formation combined with a detailed analysis of the data set at hand. The benefit of the hourly data with both particulate and gas phase concentrations is illustrated and a continuation of these measurements may prove to be very useful in future model evaluation and improvement studies. Based on our findings we propose to implement a monitoring strategy using three levels of detail within the Netherlands.

NOx Sensing with n-type WO3 - CuWO4 Composites

Thin-films of WO3 : CuWO4 composites were used as sensing materials for NO monitoring. The thin-films were prepared by the pulsed laser deposition technique using formulations with molar ratio spanning from 1 to 0. The sensing films were characterized by depth-profilometry, X-ray diffraction (XRD) and electron transport measurements. The transduction mechanism and its relation to the chemical surroundings, including temperature effects, were studied by monitoring the changes in electronic conductance (resistance) with temperature, gas-phase analyte chemical nature and concentration. Sensor performance studies were carried out. It was found that the best sensing material was composed of a nanometric layer of CuWO4. This formulation offers fast response and short recovery times towards both O2 and NO, with a response proportional to analyte concentration and excellent reproducibility.

Condensational uptake of semivolatile organic compounds in gasoline engine exhaust onto pre-existing inorganic particles

Abstract. This paper presents the results of laboratory studies on the condensational uptake of gaseous organic compounds in the exhaust of a light-duty gasoline engine onto preexisting sulfate and nitrate seed particles. Significant condensation of the gaseous organic compounds in the exhaust occurs onto these inorganic particles on a time scale of 2–5 min. The amount of condensed organic mass (COM) is proportional to the seed particle mass, suggesting that the uptake is due to dissolution determined by the equilibrium partitioning between gas phase and particles, not adsorption. The amount of dissolution in unit seed mass, S, decreases as a power function with increased dilution of the exhaust, ranging from 0.23 g g−1 at a dilution ratio of 81, to 0.025 g g−1 at a dilution ratio of 2230. It increases nonlinearly with increasing concentration of the total hydrocarbons in the gas phase (THC), rising from 0.12 g g−1 to 0.26 g g−1 for a CTHC increase of 1 to 18 μg m−3, suggesting that more organics are partitioned into the particles at higher gas phase concentrations. In terms of gas-particle partitioning, the condensational uptake of THC gases in gasoline engine exhaust can account for up to 30% of the total gas + particle THC. The organic mass spectrum of COM has the largest fragment at m/z 44, with mass ratios of mass fragments 43/44 and 57/44 at 0.59 and 2.91, much lower than those reported for gasoline engine primary organic aerosols. The mass fragment 44/total organic mass ratio of 0.097 indicates that COM contains large oxygenated components. By incorporating the present findings, regional air quality modelling results suggest that the condensational uptake of THC onto sulfate particles alone can be comparable to the primary particle mass under moderately polluted ambient conditions. These findings are important for modelling and regulating the air quality impacts of gasoline vehicular emissions.

Formation and growth of organic aerosols downwind of the Deepwater Horizon oil spill

[1] Aerosol size distributions were measured in June 2010 downwind of the surface oil slick produced by the Deepwater Horizon oil spill in the Gulf of Mexico. Previous work has shown that rapid condensation of partially oxidized hydrocarbons was responsible for formation of a plume of secondary organic aerosol downwind of the spill region. Here we examine new particle formation and growth kinetics. New particles were formed upwind of the freshest oil but downwind of oil that surfaced less than about 100 hours previously. Four nm particles formed at a rate of ∼3 cm−3 s−1 and subsequently grew by condensation at a rate of ∼20 nm hr−1; preexisting accumulation mode particles grew by ∼10 nm hr−1. The gas-phase concentration of a condensing species necessary to support irreversible growth with unit accommodation coefficient is estimated to be ∼0.04–0.09 μg m−3 (∼3–8 pptv). Gas-phase concentrations may have been higher if condensation were limited by volatility. The ratio of growth rates for newly formed particles to accumulation mode particles was consistent within error limits with irreversible condensation. The absence of new particle formation away from the <100 hr-old oil slick indicates that the oxidation products of gas-phase hydrocarbon species were directly involved in the formation and growth of new particles.

The Numerical Simulation of Gas-Liquid-Solid Three-Phase Flow in the Disc Pump

In this paper, the flow law of gas-liquid-solid three-phase flow was studied in the disc pump internal, established a set of numerical simulation method that calculated multiphase flows of disc pump internal. Finally the structure of the disk pump impeller was improved, and designed a new disc pump with multiple-blade structure, through numerical simulation calculation for the gas-liquid-solid three-phase flow of the disc pump internal, mastered change rule of fluid pressure and speed in disk pump internal, obtained relation curves between the different solid phase particle concentration with different gas phase concentration and the head with the efficiency of the pump. The head of the new disc pump was significantly improved by analyzing the disc pump head curve and the actual application.

Theoretical insights into the surface growth of rutile TiO 2

Adsorption of TiCl 4 molecules on the reduced [1 1 0] surface of TiO 2 is investigated using density functional theory with plane wave basis sets and pseudo-potentials. Adsorption energies and barriers are calculated and discussed. The rate of this adsorption process is calculated using transition state theory with estimated vibrational frequencies. Derived activation energies for TiCl 4 adsorption are associated with significant error bounds, which encapsulate the experimental activation energy for the overall growth process. Quantitative predictions of the rate can not be made based on these theoretical calculations alone, due to sensitive dependence on the vibrational frequencies. Building on the theoretical work presented here and previous experimental results a new kinetic model is constructed consisting of a TiCl 4 adsorption step followed by a secondary reaction with gaseous O 2. Simulations of a plug flow reactor are used to fit the kinetic constants for the rate limiting adsorption step. Unlike the previous phenomenological models, this new Eley–Rideal model is under the theoretical limit at all conditions and contains a physically motivated dependence on gas phase concentrations.

Beyond phthalates: Gas phase concentrations and modeled gas/particle distribution of modern plasticizers

The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called “alternative” plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p 0 and octanol–air partitioning coefficients K OA were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K p and fractions can widely differ due to the uncertainty in the predicted p 0 and K OA values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a microchamber as is shown for di-n-butyl phthalate (DnBP), di(2-ethylhexyl) adipate(DEHA), tri(octyl) trimellitate (TOTM) and DEHP.

Development and evaluation of the aerosol dynamics and gas phase chemistry model ADCHEM

Abstract. The aim of this work was to develop a model suited for detailed studies of aerosol dynamics, gas and particle phase chemistry within urban plumes, from local scale (1 × 1 km2) to regional scale. This article describes and evaluates the trajectory model for Aerosol Dynamics, gas and particle phase CHEMistry and radiative transfer (ADCHEM). The model treats both vertical and horizontal dispersion perpendicular to an air mass trajectory (2-space dimensions). The Lagrangian approach enables a more detailed representation of the aerosol dynamics, gas and particle phase chemistry and a finer spatial and temporal resolution compared to that of available regional 3D-CTMs. These features make it among others well suited for urban plume studies. The aerosol dynamics model includes Brownian coagulation, dry deposition, wet deposition, in-cloud processing, condensation, evaporation, primary particle emissions and homogeneous nucleation. The organic mass partitioning was either modeled with a 2-dimensional volatility basis set (2D-VBS) or with the traditional two-product model approach. In ADCHEM these models consider the diffusion limited and particle size dependent condensation and evaporation of 110 and 40 different organic compounds respectively. The gas phase chemistry model calculates the gas phase concentrations of 61 different species, using 130 different chemical reactions. Daily isoprene and monoterpene emissions from European forests were simulated separately with the vegetation model LPJ-GUESS, and included as input to ADCHEM. ADCHEM was used to simulate the ageing of the urban plumes from the city of Malmö in southern Sweden (280 000 inhabitants). Several sensitivity tests were performed concerning the number of size bins, size structure method, aerosol dynamic processes, vertical and horizontal mixing, coupled or uncoupled condensation and the secondary organic aerosol formation. The simulations show that the full-stationary size structure gives accurate results with little numerical diffusion when more than 50 size bins are used between 1.5 and 2500 nm, while the moving-center method is preferable when only a few size bins are selected. The particle number size distribution in the center of the urban plume from Malmö was mainly affected by dry deposition, coagulation and vertical dilution. The modeled PM2.5 mass was dominated by organic material, nitrate, sulfate and ammonium. If the condensation of HNO3 and NH3 was treated as a coupled process (pH independent) the model gave lower nitrate PM2.5 mass than if considering uncoupled condensation. Although the time of ageing from that SOA precursors are emitted until condensable products are formed is substantially different with the 2D-VBS and two product model, the models gave similar total organic mass concentrations.

Dynamics of odorant binding to thin aqueous films of rat-OBP3.

Uptake, retention and release of 5 selected odorants (benzaldehyde, 2-methylpyrazine, 2-isobutyl-3-methoxypyrazine, 2-isobutylthiazole, and 2,4,5-trimethylthiazole) by recombinant rat odor-binding protein 3 (rat-OBP3) were measured in a model system under nonequilibrium conditions. Gaseous odorants were introduced into a 100 mm section of a polar deactivated capillary in which aqueous rat-OBP3 films were formed to mimic the olfactory epithelium (OE), and the change in the gas-phase concentration of the outflow gas was monitored in real time using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The 5 odorants were chosen because they exhibited a broad range of dissociation constants with rat-OBP3 and because they were amenable to detection by on-line APCI-MS. All 5 odorants were quantitatively bound by rat-OBP3, which resulted in an effective concentration of the odorants in the aqueous layer (about 50 000-fold). Odorant release from the rat-OBP3-odorant complex into the gas phase showed that odorant release was governed by the dissociation constant of the complex and the flow rate of odorant-free air. When 2 odorants were introduced into the system, odorant uptake and release were influenced by the method of introduction and their relative affinities for the protein. Because rat-OBP3 exhibits typical odorant-binding characteristics, the results not only provide fundamental information on the kinetics of odorant mass transfer induced by the presence of OBPs in the olfactory mucus layer but also support the possibility that vertebrate OBPs may facilitate the accumulation of odorants in the OE.

Heat and Mass Transfer Model for the Thin Material Layer Consisting of Zinc-Containing Pellets in Rotary Hearth Furnace

In this paper, a mathematical model is established to simulate heat and mass transfer process among the thin material layer consisting of zinc-containing pellets while being reduced in Rotary Heath Furnace (RHF). The material layer model is based on a single pellet model, coupling heat and mass transfer and chemical reactions. The model essentially involved solving the unsteady-state equations with appropriate initial and boundary conditions using the control volume formulation. Temperature distribution, gas phase concentration, metallization rate, and dezincing rate have been obtained and discussed.

Determination of Abraham model solute descriptors for 2-ethylanthraquinone based on measured solubility ratios

The Abraham model is used to calculate the numerical values of the solute descriptors for 2-ethylanthraquinone from experimental solubilities. The correlations are log ( /) = c + e · E + s · S + a · A + b · B + v · V, log ( /C G) = c + e · E + s · S + a · A + b · B + l · L, where and refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration and E, V, A, B, S and L denote the solute descriptors. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas/solvent and water/solvent systems. The Abraham solvation parameter model was found to describe the measured solubility data to within an overall standard deviation of 0.123 log units.