Acidity across the interface from the ocean surface to sea spray aerosol

The pH of aerosols controls their impact on climate and human health. Sea spray aerosols are one of the largest sources of aerosols by mass globally, yet measuring the pH of fresh sea spray aerosols has previously been challenging. The authors of a recent study measured sea spray aerosols under controlled conditions during a sampling intensive called SeaSCAPE and optimized a pH paper-based technique to measure aerosol acidity. The authors found that fresh sea spray aerosols can be rapidly acidify by 4-6 orders of magnitude relative to the ocean. This is caused by interaction with surrounding acidic gases such as carbon dioxide, changes in relative humidity, and enhanced dissociation of organic acids within the aerosols. This result substantially changes how the chemistry of sea spray aerosols can be understood.

Reference: Angle, K. J., Crocker, D. R., Simpson, R. M. C., et al. (2021), Acidity across the interface from the ocean surface to sea spray aerosol, PNAS, 118 (2) e2018397118, https://doi.org/10.1073/pnas.2018397118