Microplastics Reduce Soil Fertility and Boost Greenhouse Gas Production, Study Shows
By Paul Arnold, Phys.org | Edited by Gaby Clark, Reviewed by Robert Egan
This figure summarizes the main findings from the microplastics (MP) soil study:
Left side – MP diversity gradient:
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CK = control (no plastic)
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D1, D3, D5 = increasing microplastic diversity (1, 3, 5 types of plastic).
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Plastic types include PET, PE, PP, PVC, PA66, POM, EVA.
Middle – Soil properties affected:
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Physicochemical properties:
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pH ↑ (soil becomes more alkaline)
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SOC (soil organic carbon) ↑
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AN (available nitrogen) ↓
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TP (total phosphorus) ↓
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Bacterial community:
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Diversity ↑
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Rhodocyclaceae ↑
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Top right – Nitrogen cycle changes:
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Key denitrification genes (narG, narH, napA, nirS, norB, norC, nosZ) are upregulated.
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More nitrogen is lost as N₂ and N₂O, especially N₂O, a potent greenhouse gas.
Flow interpretation:
Increasing microplastic diversity → alters soil pH and carbon → shifts bacterial community → activates denitrification genes → accelerates nitrogen loss → increases greenhouse gas emissions.
Over 90% of plastic waste ends up in the soil, breaking down into microplastics invisible to the naked eye. Soil pollution from microplastics poses a serious threat to soil health by harming essential microbial communities and reducing crop yields. These tiny plastics may also exacerbate climate change by increasing the production of greenhouse gases, according to a new study published in Environmental Science & Technology.
Most previous research examined one type of plastic at a time and its effect on soil function and nutrient cycling, but microplastics usually occur in mixtures. Yi-Fei Wang and Dong Zhu from the Institute of Urban Environment at the Chinese Academy of Sciences, along with colleagues, studied the combined effect of various plastic types on soil and key functions, such as the nitrogen cycle.
The researchers conducted a microcosm experiment in the lab, mixing soil samples with six types of plastic, including polyethylene terephthalate (PET) and polyvinyl chloride (PVC). Four groups were created with varying levels of plastic—from zero (control) to five types. After 40 days of incubation, soil samples were analyzed for properties such as pH, enzyme activities, and bacterial DNA to identify species and functional genes.
The analysis revealed that increasing microplastic diversity significantly altered soil health. For example, plastic mixtures raised soil pH (making it more alkaline) and increased soil carbon content.
Nitrogen Loss
A key finding was that diverse microplastics boosted bacterial genes responsible for denitrification—the process by which bacteria convert plant nitrogen into nitrogen gas released into the atmosphere. This not only reduces soil fertility but also releases nitrous oxide, a greenhouse gas roughly 300 times more potent than carbon dioxide. The accelerated nitrogen loss was mainly driven by bacteria in the Rhodocyclaceae family.
“Our findings deepen understanding of the ecological effects of microplastic contamination on soil health and nutrient cycling,” the researchers wrote. “More importantly, they highlight the need to consider microplastic diversity in soil management to mitigate nitrogen loss and protect soil ecosystem services.”
Source: Tian-Gui Cai et al., Microplastic Diversity as a Potential Driver of Soil Denitrification Shifts, Environmental Science & Technology (2025). DOI: 10.1021/acs.est.5c04981
