New Study: The Ocean Is Emitting Millions of Pounds of Plastic Into the Atmosphere

A study quantifies the atmospheric emission of microplastics from sea spray, revealing that oceans release between 0.02 to 7.4 million tons of microplastics annually, necessitating detailed ocean microplastics inventories for accurate assessment.

A new study quantifies how much microplastic is sent into the air from ocean spray. When sea bubbles pop, they launch tiny particles, like salt or organic fragments, into the atmosphere. This activity transfers a considerable amount of material, which can impact the world’s climate by altering the atmosphere’s radiative balance and acting as nuclei for cloud formation.

But can sea spray also toss microplastics, which are now ubiquitous in the ocean, into the atmosphere?

Investigating Bubble-Bursting Ejection Mechanics

Luc Deike and colleagues explored the physical processes behind the bubble-bursting ejection of microplastic in laboratory experiments using high-speed photography.

The authors demonstrate that microplastic particles with diameters from 10 μm–280 μm are transported out of seawater and into the air by small droplets known as “jet drops” that are ejected by a bursting bubble of sea froth. These small drops become airborne with their plastic cargo. Once airborne, the water may evaporate, leaving the plastic aloft in wind currents.

A 1.9 mm bubble bursting to produce a jet drop, which can transport 100 μm diameter polyethylene microplastic pieces. Credit: Shaw et al.

Using estimations of the concentration of microplastics in the sea, the total amount of microplastics emitted by the world’s seas can then be estimated. The authors calculate that between 0.02 (44,000 lbs) and 7.4 Mt (16,000,000 lbs) of plastic—with a best guess of .1 Mt (220,000 lbs) of plastic— is emitted by the ocean each year. Inventories of ocean microplastic concentrations are now needed to reduce uncertainties in quantifying oceanic emissions of microplastics, according to the authors. 

Reference: “Ocean emission of microplastic” by Daniel B Shaw, Qi Li, Janine K Nunes and Luc Deike, 3 October 2023, PNAS Nexus.
DOI: 10.1093/pnasnexus/pgad296