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Biodegradability of Disposable Surgical Face Masks Littered into Soil Systems during the COVID 19 Pandemic—A First Approach Using Microcosms
Summary
Researchers assessed the microbial degradability of polypropylene-based disposable surgical face masks in soil using a 6-month microcosm experiment at 25 degrees C, measuring CO2 production and using solid-state NMR to characterize degradation products. They found that roughly 4-5% of mask carbon was rapidly mineralized but identified slow-pool mean residence times of 7 to 28 years for the remaining material, suggesting microbial PP degraders exist in soil though mask persistence is prolonged.
The COVID-19 pandemic caused massive use and improper disposal of surgical polypropylene (PP)-based face masks. For a first evaluation of the respective environmental consequences, we performed a 6-month microcosm experiment at 25 °C to determine the microbial degradability of 10 × 10 mm cuts of single mask layers and of a complete mask mixed with topsoil (Cambisol). By analyzing the CO2 production, we identified a fast pool with a mean residence time (MRTfast) of 3 to 7 days, corresponding to approximately 4 to 5% of the total mask carbon. Solid-state nuclear magnetic resonance (NMR) spectroscopy of the degraded masks suggests a cut-off of PP units or oligomers as a main degradation mechanism. The slow carbon pool of the center mask revealed an MRTslow of 7 years and those of the remaining mask material MRTslows between 19 and 28 years, which is three to five times longer than those of soil organic matter (SOM) of the pure soil. Since the masks were not pretreated, and decomposed in the dark without UV radiation, our data support our hypothesis that in soils, microbes must exist that can decompose PP, although their nature still has to be revealed in future attempts.