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Electrochemical-oxidative dualism: Decoupling the acute effects of lake water-aged tire wear particles on periphytic biofilm-mediated denitrification
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This study examined how freshly generated and lake water-aged tire wear particles (TWPs) of different types affect denitrification in periphytic biofilms. Neither fresh nor aged TWPs altered nitrate removal or denitrification gene abundance, despite aging increasing the electron exchange capacity and free radical content of particles.
As emerging microplastic pollutants, tire wear particles (TWPs) have unclear photochemical impacts on aquatic nitrogen cycles. This study investigated how three types of TWPs-mechanically generated via rolling (R-TWPs), sliding (S-TWPs), and low-temperature crushing (C-TWPs)-and their aged counterparts (AC-, AR-, AS-TWPs) influenced nitrate reduction in periphytic biofilms. Aging in lake water altered the surface properties of TWPs: AC- and AR-TWPs accumulated inorganic ions and organic coatings, while AS-TWPs facilitated microbial colonization. Aged TWPs exhibited enhanced electron exchange capacity (EEC) and elevated levels of environmentally persistent free radicals (EPFRs). However, neither fresh nor aged TWPs altered nitrate removal, denitrification gene abundance (nirK, nirS), or microbial community structure in a dose-dependent manner; their impacts showed no simple correlation with EEC or EPFRs. Under illumination, TWPs acted as electron shuttles, transferring photogenerated electrons. Quenching hydroxyl radicals (·OH) revealed a strong positive correlation between EEC (specifically, electron donating and accepting capacities) and nitrate removal rates (r = 0.928-0.957, p < 0.01). Variance partitioning analysis identified EPFRs as promoters (contribution: 0.16) and ·OH as inhibitors (contribution: -0.18) of denitrification. At concentrations of 1.0-50.0 mg L over 7 days, TWPs exerted paradoxical effects on urban river nitrogen cycling. This paradox arose from synergistic interactions between surface-active components (e.g., carbon black, zinc oxide) and photosensitive moieties (e.g., EPFRs, redox functional groups). This work highlights the dual role of photoactive TWPs in modulating aquatic nitrogen cycles and underscores the necessity of evaluating their photochemical reactivity and oxidative stress effects when assessing microplastic pollution in urban water systems.
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Toxic effects of environmentally persistent free radicals (EPFRs) on the surface of tire wear particles on freshwater biofilms: The alleviating role after sewage-incubation-aging
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Researchers investigated how tire wear particles affect freshwater biofilms, which are communities of microorganisms that play important roles in aquatic ecosystems. They found that reactive chemical compounds on the surface of fresh tire particles caused significant toxicity, reducing photosynthesis and biological activity in the biofilms. The study suggests that aging in sewage environments reduces the toxicity of tire wear particles by breaking down these harmful surface chemicals.
Effects of tire wear particles on freshwater bacterial-fungal community dynamics and subsequent elemental cycles using microcosms.
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Researchers conducted freshwater microcosm experiments to assess how tire wear particles (TWPs) affect bacterial-fungal community dynamics and biogeochemical cycles in rural versus urban lake sediments and overlying water. They found TWPs altered microbial composition more strongly in water than sediment and increased bacteria-fungi network complexity, with cascading effects on nitrogen and carbon cycling.
Effects of pristine and photoaged tire wear particles and their leachable additives on key nitrogen removal processes and nitrous oxide accumulation in estuarine sediments
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Researchers exposed estuarine sediments to pristine and photoaged tire wear particles (TWPs) and their leachates, finding that photoaged TWPs inhibited both denitrification and anammox processes while increasing nitrous oxide accumulation, driven largely by elevated zinc release from weathered particles altering microbial community structure.
Aging increases the particulate- and leachate-induced toxicity of tire wear particles to microalgae.
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Researchers found that environmental aging of tire wear particles increases their toxicity to marine microalgae beyond that of fresh particles, with aged particles triggering greater oxidative stress, photosynthesis disruption, and metabolic changes in the algae.
Effects of aged tire wear particles on nitrogen removal in constructed wetlands: Mechanistic insights into different aging pathways
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Tiny particles worn off tires wash into constructed wetlands—engineered systems that use plants and microbes to filter pollutants from water—and this study found they can weaken the wetland's ability to remove nitrogen, a common water pollutant. Whether the tire particles were broken down by sunlight or heat mattered: both types harmed helpful bacteria and stressed plants, but through different mechanisms, with sun-degraded particles causing more damage. This matters because if these widely used water treatment systems become less effective at removing nitrogen, it could allow more pollution to reach rivers and drinking water sources, highlighting a
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