Physical properties of short chain aqueous organosulfate aerosol

Organosulfates comprise up to 30% of the organic fraction of aerosol. Organosulfate aerosol physical properties, such as water activity, density, refractive index, and surface tension, are key to predicting their impact on global climate. However, current understanding of these properties is limited. Here, we measure the physical properties of aqueous solutions containing sodium methyl or ethyl sulfate and parameterise the data as a function of solute concentration. The experimental data are compared to available literature data for organosulfates, as well as salts (sodium sulfate and sodium bisulfate) and organics (short alkyl chain length alcohols and carboxylic acids) to determine if the physical properties of organosulfates can be approximated by molecules of similar functionality. With the exception of water activity, we find that organosulfates have intermediate physical properties between those of the salts and short alkyl chain organics. This work highlights the importance of measuring and developing models for the physical properties of abundant atmospheric organosulfates in order to better describe aerosol's impact on climate.

Automated summary

Organosulfates make up to 30% of the organic fraction of aerosol. Understanding their physical properties is crucial for predicting their impact on global climate, yet current knowledge is limited. This study measures the physical properties of aqueous solutions containing sodium methyl or ethyl sulfate and compares them with literature data for organosulfates, salts, and organics. The results show that organosulfates have intermediate physical properties between salts and short alkyl chain organics, except for water activity. This work emphasizes the importance of measuring and developing models for the physical properties of abundant atmospheric organosulfates to better understand aerosol's climate impact.