Plastic waste and rocks form chemical bond

For the first time, scientists have verified that rocks and plastic can form a chemical bond. These plastic covered rocks create hotspots for microplastic release. 

“This shows how seriously we are impacting the planet with waste and chemicals,” says scientist Michael Bank, from Institute of Marine Research in Norway, who co-authored the paper. 

Plastic waste

The rocks that were investigated were discovered along a creek in Hechi, China.

The plastic films covering the rocks, comes from waste in and around the creek. Including polypropylene films – like those used to make plastic bags, and polyethylene films – like those used by farmers to cover crops. 

The chemical bonds between the rock and the plastic may have been due to the uv-light from the sun or the microbes on the plastic. 

Hotspot

To determine how much these “plastic rocks” would shed, the scientists ran experimental wet-dry cycles, designed to mimic realistic flooding event conditions. 

The study reported that just one square meter of attached plastic debris could release millions of microplastics and billions of nanoplastics into the environment. 

“It was a hotspot for microplastic release,” says Bank. 

The scientists reported that the rate at which microplastics were generated and released from these plastic-rock complexes was significantly greater than release rates for landfills, seawater, and marine sediments. 

Their findings were published in the prestigious scientific journal Environmental Science & Technology. 

A physical and a chemical threat

Rivers are undoubtedly key ecosystems that connect land and sea. 

“Rivers are important vectors for many pollutants, including microplastics and nanoplastics, and link land and sea ecosystems,” says Bank.

“River ecosystems can also transfer significant amounts of other critical contaminants to coastal zones, including PFOS-PFOA compounds, mercury, PCBs, and agricultural runoff”.

These plastic particles may pose a chemical and physical threat to floodplain organisms, and biota living down-stream in marine ecosystems. 

Managing plastic pollution

Estimations by the United Nations suggest that >80% of marine plastic pollution originates from land-based sources. In 2024 world leaders are due to finalize a new international agreement to end plastic pollution. 

“With plastic it is important to manage the plastic before it gets to the ocean”, says Bank. 

“Once they get into marine ecosystems it is nearly impossible to recover it. Once you’re upstream in rivers and ponds, you have a better opportunity.”
 

References:

Wang L., M.S. Bank, J. Rinklebe, and D. Hou. 2023. Plastic-Rock Complexes as Hotspots for Microplastic Generation. Environmental Science and Technology 57, 7009–7017. doi: 10.1021/acs.est.3c00662.

Bourzac, K. 2023. Plastic waste found chemically bonded to rocks in China. Nature. doi.org/10.1038/d41586-023-01037-6.