scholarly journals Joint effect of organic acids and inorganic salts on cloud droplet activation

2011 ◽  
Vol 11 (8) ◽  
pp. 3895-3911 ◽  
Author(s):  
M. Frosch ◽  
N. L. Prisle ◽  
M. Bilde ◽  
Z. Varga ◽  
G. Kiss
Keyword(s):  
Surface Tension ◽  
Sodium Chloride ◽  
Organic Acids ◽  
Aqueous Solutions ◽  
Fulvic Acid ◽  
Water Activity ◽  
Inorganic Salt ◽  
Cloud Droplet ◽  
Surface Partitioning ◽  
Kohler Theory

Abstract. We have investigated CCN properties of internally mixed particles composed of one organic acid (oxalic acid dihydrate, succinic acid, adipic acid, citric acid, cis-pinonic acid, or Nordic reference fulvic acid) and one inorganic salt (sodium chloride or ammonium sulphate). Surface tension and water activity of aqueous model solutions with concentrations relevant for CCN activation were measured using a tensiometer and osmometry, respectively. The measurements were used to calculate Köhler curves and critical supersaturations, which were compared to measured critical supersaturations of particles with the same chemical compositions, determined with a cloud condensation nucleus counter. Surfactant surface partitioning was not accounted for. For the aqueous solutions containing cis-pinonic acid and fulvic acid, a depression of surface tension was observed, but for the remaining solutions the effect on surface tension was negligible at concentrations relevant for cloud droplet activation. The surface tension depression of aqueous solutions containing both organic acid and inorganic salt was approximately the same as or smaller than that of aqueous solutions containing the same mass of the corresponding pure organic acids. Water activity was found to be highly dependent on the type and amount of inorganic salt. Sodium chloride was able to decrease water activity more than ammonium sulphate and both inorganic salts are predicted to have a smaller Raoult term than the studied organic acids. Increasing the mass ratio of the inorganic salt led to a decrease in water activity. Water activity measurements were compared to results from the E-AIM model and values estimated from both constant and variable van't Hoff factors. The correspondence between measurements and estimates was overall good, except for highly concentrated solutions. Critical supersaturations calculated with Köhler theory based on measured water activity and surface tension, but not accounting for surface partitioning, compared well with measurements, except for the solutions containing sodium chloride and oxalic acid or one of the more surface active organic compounds. In such cases, significantly lower values were obtained from Köhler theory than the measured critical supersaturations with deviations above 50% for a 60 nm particle containing 50% (dry mass) of Nordic reference fulvic acid, suggesting that surfactant partitioning and/or an effect of sodium chloride on solubility of the organic component is important.

scholarly journals Joint effect of organic acids and inorganic salts on cloud droplet activation

2010 ◽  
Vol 10 (7) ◽  
pp. 17981-18023
Author(s):  
M. Frosch ◽  
N. L. Prisle ◽  
M. Bilde ◽  
Z. Varga ◽  
G. Kiss
Keyword(s):  
Surface Tension ◽  
Sodium Chloride ◽  
Organic Acids ◽  
Organic Acid ◽  
Water Activity ◽  
Inorganic Salt ◽  
Cloud Droplet ◽  
Surface Partitioning ◽  
Kohler Theory ◽  
Droplet Activation

Abstract. We have investigated CCN properties of internally mixed particles composed of one organic acid (oxalic acid, succinic acid, adipic acid, citric acid, cis-pinonic acid, or nordic reference fulvic acid) and one inorganic salt (sodium chloride or ammonium sulphate). Surface tension and water activity of aqueous model solutions with concentrations relevant for CCN activation were measured using a tensiometer and osmometry, respectively. The measurements were used to calculate Köhler curves, which were compared to measured critical supersaturations of particles with the same chemical compositions, determined with a cloud condensation nucleus counter. Surfactant surface partitioning was not accounted for. For the mixtures containing cis-pinonic acid or fulvic acid, a depression of surface tension was observed, but for the remaining mixtures the effect on surface tension was negligle at concentrations relevant for cloud droplet activation, and water activity was the more significant term in the Köhler equation. The surface tension depression of aqueous solutions containing both organic acid and inorganic salt was approximately the same as or smaller than that of aqueous solutions containing the same mass of the corresponding pure organic acids. Water activity was found to be highly dependent on the type and amount of inorganic salt. Sodium chloride was able to decrease water activity more than ammonium sulphate and both inorganic compounds had a higher effect on water activity than the studied organic acids, and increasing the mass ratio of the inorganic compound led to a decrease in water activity. Water activity measurements were compared to results from the E-AIM model and values estimated from both constant and variable van't Hoff factors to evaluate the performance of these approaches. The correspondence between measuments and estimates was overall good, except for highly concentrated solutions. Critical supersaturations calculated with Köhler theory based on measured water activity and surface tension, but not accounting for surface partitioning, compared well with measurements, except for the solutions containing sodium chloride or one of the more surface active organic compounds. In such cases, significantly lower values were obtained from Köhler theory than the measured critical supersaturations, suggesting that surfactant partitioning and/or an effect of sodium chloride on solubility of the organic component is important.

scholarly journals Cloud droplet activation and surface tension of mixtures of slightly soluble organics and inorganic salt

2005 ◽  
Vol 5 (2) ◽  
pp. 575-582 ◽  
Author(s):  
S. Henning ◽  
T. Rosenørn ◽  
B. D'Anna ◽  
A. A. Gola ◽  
B. Svenningsson ◽  
...  
Keyword(s):  
Surface Tension ◽  
Sodium Chloride ◽  
Inorganic Salt ◽  
Cloud Droplet ◽  
Dicarboxylic Acids ◽  
Solid Particles ◽  
Particle Phase ◽  
Critical Supersaturation ◽  
Kohler Theory ◽  
Droplet Activation

Abstract. Critical supersaturations for internally mixed particles of adipic acid, succinic acid and sodium chloride were determined experimentally for dry particles sizes in the range 40-130nm. Surface tensions of aqueous solutions of the dicarboxylic acids and sodium chloride corresponding to concentrations at activation were measured and parameterized as a function of carbon content. The activation of solid particles as well as solution droplets were studied and particle phase was found to be important for the critical supersaturation. Experimental data were modelled using Köhler theory modified to account for limited solubility and surface tension lowering.

scholarly journals Cloud droplet activation and surface tension of mixtures of slightly soluble organics and inorganic salt

2004 ◽  
Vol 4 (6) ◽  
pp. 7463-7485 ◽  
Author(s):  
S. Henning ◽  
T. Rosenørn ◽  
B. D’Anna ◽  
A. A. Gola ◽  
B. Svenningsson ◽  
...  
Keyword(s):  
Surface Tension ◽  
Sodium Chloride ◽  
Inorganic Salt ◽  
Cloud Droplet ◽  
Dicarboxylic Acids ◽  
Solid Particles ◽  
Particle Phase ◽  
Critical Supersaturation ◽  
Kohler Theory ◽  
Droplet Activation

Abstract. Critical supersaturations for internally mixed particles of adipic acid, succinic acid and sodium chloride were determined experimentally for dry particles sizes in the range 40–130 nm. Surface tensions of aqueous solutions of the dicarboxylic acids and sodium chloride corresponding to concentrations at activation were measured and parameterized as a function of carbon content. The activation of solid particles as well as solution droplets were studied and particle phase was found to be important for the critical supersaturation. Experimental data were modelled using Köhler theory modified to account for limited solubility and surface tension lowering.

scholarly journals Modeling CCN activity of chemically unresolved model HULIS, including surface tension, non-ideality, and surface partitioning

2018 ◽  
Author(s):  
Nonne L. Prisle ◽  
Bjarke Molgaard
Keyword(s):  
Surface Tension ◽  
Water Activity ◽  
Cloud Droplet ◽  
Tension Reduction ◽  
Surface Tension Reduction ◽  
Surface Partitioning ◽  
Critical Supersaturation ◽  
Surface Active ◽  
Droplet Activation ◽  
Ccn Activity

Abstract. Cloud condensation nuclei (CCN) activity of aerosol particles comprising surface active Nordic Aquatic Fulvic Acid (NAFA) and NaCl was modeled with four different approaches to account for NAFA bulk-to-surface partitioning and the combined influence of NAFA and NaCl on surface tension and water activity of activating droplets. Calculations were made for particles with dry diameters of 30–230 nm and compositions covering the full range of relative NAFA and NaCl mixing ratios. Continuous ternary parametrizations of aqueous surface tension and water activity with respect to independently varying NAFA and NaCl mass concentrations were developed from previous measurements on macroscopic bulk solutions and implemented to a Köhler model framework. This enabled comprehensive thermodynamic predictions of cloud droplet activation, including equilibrium surface partitioning, for particles comprising chemically unresolved organic NAFA mixtures. NAFA here serves as a model for surface active atmospheric humic-like substances (HULIS) and for chemically complex organic aerosol in general. Surfactant effects are gauged via predictions of a suite of properties for activating droplets, including critical supersaturation and droplet size, bulk phase composition, surface tension, Kelvin effect, and water activity. Assuming macroscopic solution properties for activating droplets leads to gross overestimations of reported experimental CCN activation, mainly by overestimating surface tension reduction from NAFA solute in droplets. Failing to account for bulk-to-surface partitioning of NAFA introduces severe biases in evaluated droplet bulk and surface composition and critical size, which here specifically affect cloud activation thermodynamics, but more generally could also impact heterogeneous chemistry on droplet surfaces. Model frameworks based on either including surface partitioning and/or neglecting surface tension reduction give similar results for both critical supersaturation and droplet properties and reproduce reported experimental CCN activity well. These perhaps counterintuitive results reflect how the bulk phase is nearly depleted in surface active organic from surface partitioning in submicron droplets with large surface area for a given bulk volume. As a result, NAFA has very little impact on surface tension and water activity at the point of droplet activation. In other words, the predicted surfactant strength of NAFA is significantly lower in sub-micron activating droplets than in macroscopic aqueous solutions of the same overall composition. These results show similar effects of chemically complex surfactants as have previously been seen only for simple surfactants with well-defined molecular properties and add to the growing appreciation of the complex role of surface activity in cloud droplet activation.

scholarly journals Surfactants in cloud droplet activation: mixed organic-inorganic particles

2009 ◽  
Vol 9 (6) ◽  
pp. 24669-24715 ◽  
Author(s):  
N. L. Prisle ◽  
T. Raatikainen ◽  
A. Laaksonen ◽  
M. Bilde
Keyword(s):  
Surface Tension ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Cloud Droplet ◽  
Droplet Growth ◽  
Inorganic Particles ◽  
Surfactant Properties ◽  
Surface Partitioning ◽  
Kohler Theory ◽  
Droplet Activation

Abstract. Organic compounds with surfactant properties are commonly found in atmospheric aerosol particles. Surface activity can significantly influence the cloud droplet forming ability of these particles. We have studied the cloud droplet formation by two-component particles comprising one of the organic surfactants sodium octanoate, sodium decanoate, sodium dodecanoate, and sodium dodecyl sulfate, mixed with sodium chloride. Critical supersaturations were measured with a static diffusion cloud condensation nucleus counter (Wyoming CCNC-100B). Results were modeled from Köhler theory applying three different representations of surfactant properties: (1) using concentration-dependent surface tension reduction during droplet growth and explicitly accounting for surfactant surface partitioning in both solute suppression (Raoult effect) and curvature enhancement (Kelvin effect) contributions to the droplet equilibrium water vapor supersaturation, (2) disregarding surfactant partitioning and using a concentration-dependent surface tension for the droplets corresponding to a macroscopic (bulk) aqueous solution of the same overall composition, and (3) disregarding surfactant properties and assuming the constant surface tension of pure water throughout droplet activation. We confirm previous results for single-component organic surfactant particles, that experimental critical supersaturations are greatly underpredicted, if reduced surface tension is applied in Köhler theory while ignoring the effects of surface partitioning in droplets. We further show that assuming the constant surface tension of pure water can also lead to significant underpredictions of experimental critical supersaturations. The full account for surfactant partitioning in activating droplets generally predicts experimental critical supersaturations well. In addition, for mixed particles comprising less than 50% by mass of surfactant, ignoring surfactant properties and simply using the constant surface tension of pure water also provides a good first-order approximation of the observed activation.

scholarly journals Inverse modelling of Köhler theory – Part 1: A response surface analysis of CCN spectra with respect to surface-active organic species

2016 ◽  
Author(s):  
Samuel Lowe ◽  
Daniel Partridge ◽  
David Topping ◽  
Philip Stier
Keyword(s):  
Surface Tension ◽  
Sensitivity Analysis ◽  
Physicochemical Parameters ◽  
Response Surfaces ◽  
Inverse Modelling ◽  
Organic Species ◽  
Surface Partitioning ◽  
Bulk Surface ◽  
Kohler Theory ◽  
Surface Active

Abstract. In this study a novel framework for inverse modelling of CCN spectra is developed using Köhler theory. The framework is established by carrying out an extensive parametric sensitivity analysis of CCN spectra using 2-dimensional response surfaces. The focus of the study is to assess the relative importance of aerosol physicochemical parameters while accounting for bulk-surface partitioning of surface active organic species. By introducing an Objective Function (OF) that provides a diagnostic metric for deviation of modelled CCN concentrations from observations, a novel method of analysing CCN sensitivity over a range of atmospherically relevant supersaturations, corresponding to broad range of cloud types and updraft velocities, is presented. Such a scalar metric facilitates the use of response surfaces as a tool for visualising CCN sensitivity over a range of supersaturations to two parameters simultaneously. Using response surfaces, the posedness of the problem as suitable for further study using inverse modelling methods in a future study is confirmed. The organic fraction of atmospheric aerosols often includes surface-active organics. Partitioning of such species between the bulk and surface phases has implications for both the Kelvin and Raoult terms in Köhler theory. As such, the analysis conducted here is carried out for a standard Köhler model as well more sophisticated partitioning schemes seen in previous studies. Using Köhler theory to model CCN concentrations requires knowledge of many physicochemical parameters some of which are difficult to measure in-situ at the scale of interest. Therefore, novel methodologies such as the one developed here are required to probe the entire parameter space of aerosol-cloud interaction problems of high dimensionality and provide global sensitivity analyses (GSA) to constrain parametric uncertainties. In this study, for all partitioning schemes and environments considered, the accumulation mode size distribution parameters, surface tension σ, organic:inorganic mass ratio α, insoluble fraction and solution ideality ϕ were found to have significant sensitivity. In particular, the number concentration of the accumulation mode N2 and surface tension σ showed a high degree of sensitivity. The complete treatment of bulk-surface partitioning is found to model CCN spectra similar to those calculated using classical Köhler theory with the surface tension of a pure water drop, as found in traditional sensitivity analysis studies. In addition, the sensitivity of CCN spectra to perturbations in the partitioning parameters K and Γ was found to be negligible. As a result, this study supports previously held recommendations that complex surfactant effects might be neglected and continued use of classical Köhler theory in GCMs is recommended to avoid additional computational burden. In this study we do not include all possible composition dependent processes that might impact CCN activation potential. Nonetheless, this study demonstrates the efficacy of the applied sensitivity analysis to identify important parameters in those processes and will be extended to facilitate a complete GSA using the Monte Carlo Markov Chain (MCMC) algorithm class. As parameters such as σ and ϕ are difficult to measure at the scale of interest in the atmosphere they can introduce considerable parametric uncertainty to models and therefore they are particularly good candidates for a future parameter calibration study that facilitates a global sensitivity analysis (GSA) using automatic search algorithms.

The metachors of polyvalent and associated electrolytes in aqueous solutions

1984 ◽  
Vol 49 (5) ◽  
pp. 1079-1089
Author(s):  
Jiří Čeleda ◽  
Stanislav Škramovský ◽  
Jana Žilková
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Oxalic Acid ◽  
Organic Acids ◽  
Aqueous Solutions ◽  
Preceding Paper ◽  
Weak Electrolytes ◽  
Direct Proportionality ◽  
Very High

The quantity metachor introduced in the preceding paper was evaluated from the experimental data on surface tension of the aqueous solutions for a set of polyvalent and weak electrolytes. The almost complete concentration independence of the metachor and its direct proportionality to the number of the free charges in a dissociated molecule (observed and theoretically substantiated in the above cited paper for strong 1,1-, 1,2- and 2,1-valent electrolytes) has been verified in the present paper also for electrolytes of the higher valency types. The metachor values of fully dissociated 1,1-, 1,2-, 1,3- and 1,4-valent electrolytes follow a ratio (5 ± 1) : (10 ± 1.5) : 15 : 22 cm3 mol-1. Association of the electrolytes decreases correspondingly the metachor value as one can see on the case of electrolytes with bulky ions (NH4SCN, KCH3COO, Na2S2O3, hexacyanoferrates(II) or with the free acids H2SO4, H2CrO4, H3PO4 etc. A weak, in the investigated concentration range neglibility dissociated oxalic acid, consisting of small hydrated hydrophilic molecules, exhibits metachor values close to zero. Dibasic organic acids with a larger number of hydrophobic CH2 groups reach very high negative metachor values, however, their salts again possess metachor values close to 10 cm3 mol-1 - in accordance with the values found for strong 1,2-valent electrolytes. The metachors of ZnCl2 and CdCl2 decrease sharply from the last mentioned value, with increasing concentration while the metachor value of zinc perchlorate remains unchanged at the level corresponding to the fully dissociated salt. This is in agreement with the well known sequence of tendency of the d10-cations to form complexes with the Cl- and ClO-4 anions. All these facts have verified that the metachor can be, in principle, applied for a diagnostic states of the electrolytes in aqueous solutions.

scholarly journals Surface Tension of Aqueous Solutions of Small-Chain Amino and Organic Acids

2019 ◽  
Vol 64 (12) ◽  
pp. 5049-5056
Author(s):  
Mohsin Ali Raza ◽  
Paul D. Hallett ◽  
Xiangyang Liu ◽  
Maogang He ◽  
Waheed Afzal
Keyword(s):  
Surface Tension ◽  
Organic Acids ◽  
Aqueous Solutions ◽  
Small Chain

scholarly journals Modelling the cloud condensation nucleus activity of organic acids

2007 ◽  
Vol 7 (2) ◽  
pp. 5341-5364 ◽  
Author(s):  
Z. Varga ◽  
G. Kiss ◽  
H.-C. Hansson
Keyword(s):  
Surface Tension ◽  
Organic Acids ◽  
Water Activity ◽  
Adipic Acid ◽  
Early Phase ◽  
Carbon Number ◽  
Droplet Formation ◽  
Cloud Condensation Nucleus ◽  
Minor Effect ◽  
Critical Supersaturation

Abstract. In this study vapour pressure osmometry was used to determine water activity in solutions of organic acids. The surface tension of the solutions was also monitored in parallel and then Köhler curves were calculated for nine organic acids (oxalic, malonic, succinic, glutaric, adipic acid, maleic acid, malic acid, citric acid and pinonic acid). Surface tension depression is negligible for most of the organic acids in dilute (≤1 w/w%) solutions. Therefore, these compounds affect the supersaturation only in the beginning phase of droplet formation but not necessarily at the critical size. An exception is cis-pinonic acid which remarkably depress surface tension also in dilute (0.1 w/w%) solution and hence at the critical point. The surface tension of organic acid solutions is influenced by the solubility of the compound, the length of the carbon chain and also by the polar functional groups present in the molecule. Similarly to surface tension solubility plays an important role also in water activity: compounds with higher solubility (e.g. malonic, maleic, and glutaric acid) reduce water activity significantly in the early phase of droplet formation while less soluble acids (e.g. succinic and adipic acid) are saturated in small droplets and the solution starts diluting only in bigger droplets. As a consequence, compounds with lower solubility have a minor effect on water activity in the early phase of droplet formation. To deduce the total effect Köhler curves were calculated and critical supersaturations were determined for the organic acids using measured surface tension and water activity. It was found that critical supersaturation grew with growing carbon number. Oxalic acid had the lowest critical supersaturation in the size range studied and it was comparable to the activation of ammonium sulfate. The Sc values obtained in this study were compared to data from CCNC measurements. In most cases good agreement was found.

Sign in / Sign up

Export Citation Format

Share Document