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

Area of Science:

• Atmospheric Chemistry
• Ocean-Atmosphere Interactions
• Environmental Science

Background:

• Aerosols significantly influence climate, human health, and atmospheric chemistry.
• Aerosol pH is a critical factor in aerosol physicochemical properties.
• Current understanding of aerosol pH (acidic, neutral, or basic) remains uncertain.

Purpose of the Study:

• To investigate the pH of freshly emitted sea spray aerosols.
• To determine the factors influencing sea spray aerosol acidity.
• To understand the implications of aerosol acidity on atmospheric chemistry.

Main Methods:

• Measurements of nascent sea spray aerosol pH were conducted in a specialized ocean-atmosphere facility.
• Analysis of the relationship between aerosol acidity, dissolved carbon dioxide, and marine biology.
• Characterization of aerosol pH across different particle sizes.

Main Results:

• Freshly emitted sea spray aerosols exhibit a significantly lower pH than seawater, with a difference of approximately four pH units.
• Smaller aerosol particles (below 1 μm in diameter) show even lower pH values.
• A correlation was observed between aerosol acidity and dissolved carbon dioxide, but not with marine biology.

Conclusions:

• Sea spray aerosol acidification occurs rapidly across the ocean-air interface within minutes of aerosol formation.
• Dissolved carbon dioxide appears to be a contributing factor to aerosol acidity.
• The findings have significant implications for understanding aerosol impacts on atmospheric chemistry and climate.