Rising Gas Bubbles Can Lift Microplastics From Sediment Back Into Water, Study Finds

The mud at the bottom of a lake or river is often described as a final resting place for microplastics. A new lab study suggests that isn’t always true. When gas bubbles rise out of sediment, they can carry microplastics back up into the water above.

The paper, “Ebullition-Enhanced Release of Microplastics from Aquatic Sediment to Overlying Water: An Overlooked Transport Pathway,” was published online on October 5, 2026 in Environmental Science & Technology (DOI: 10.1021/acs.est.6c06432). Ebullition is the scientific term for gas bubbling up from sediment, which happens naturally in many lakes, ponds, wetlands and reservoirs as microbes break down organic matter.

What the team did

• In laboratory experiments, the researchers used air-purged ebullition (bubbles pushed up through sediment) to test whether rising gas could move microplastics out of sediment.
• They tested four common plastics: polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and polylactic acid (PLA), a plant-based plastic.

What they found

• Bubbles moved plastics out of the sediment. Over 9 days, between 8.9% and 12.1% of the microplastics were released from the sediment into the overlying water.
• Most of it happened early. Suspended microplastic levels in the water rose quickly during the first 48 hours, then slowed and eventually levelled off, a pattern the team described with a power-law model.
• Sediment clumps slow, but don’t stop, the ride up. Theoretical calculations suggest that when microplastics aggregate with suspended sediment, their rise speed drops from about 9.38–9.99 cm per second to 8.64–9.95 cm per second.
• How it works. The authors point to a combined mechanism: particles attach to rising bubbles, bubble-driven flow works against gravity settling, and short-lived pressure changes help lift particles.

Why it matters

The authors conclude that gas bubbling could turn sediments from a long-term sink for microplastics into a secondary source, releasing particles back into the water. Most attention goes to wastewater, runoff and air as the ways microplastics enter water. This study adds a pathway that starts at the bottom.

It’s also a reminder about scope. This was a controlled lab experiment with air bubbles and four plastic types. It did not measure drinking water or a specific lake, and it makes no health finding. Field studies will be needed to show how much this matters in real waterways.

A note on scope: this post summarises a peer-reviewed study. It is not medical advice, and WaterVO was not involved in the research.

Sources

• Liu, S.; et al. “Ebullition-Enhanced Release of Microplastics from Aquatic Sediment to Overlying Water: An Overlooked Transport Pathway.” Environmental Science & Technology, published online October 5, 2026. DOI: 10.1021/acs.est.6c06432

Photo: methane bubbles on a lake near Fairbanks, Alaska, NASA Earth Right Now / ABoVE (public domain).

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