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Polystyrene microplastics reduce Cr(VI) and decrease its aquatic toxicity under simulated sunlight

Journal of Hazardous Materials 2022 28 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count. Score: 50 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.
Jun Zhang, Jiating Wei, Tian Hu, Li Du, Zhaojin Chen, Yao Zhang, Weicheng Zhang, Weicheng Zhang

Summary

Researchers discovered that polystyrene microplastics can reduce toxic Cr(VI) to less harmful Cr(III) under simulated sunlight, decreasing chromium's aquatic toxicity and revealing an unexpected role of microplastics in contaminant transformation.

Polymers

Microplastics (MPs) serve as vectors for chromium (Cr), influencing its fate and toxicity in aquatic environments, and have attracted much attention recently. However, it is still unknown whether MPs mediate Cr species transformation under sunlight irradiation. This study confirmed that polystyrene (PS) MPs could reduce Cr(VI) to Cr(III) under sunlight irradiation, with a photoreduction rate constant of 0.0023 h. PS MPs-mediated Cr(VI) reduction was predominantly dependent on O and simultaneously suppressed by O, •OH and PS* . Aged PS MPs were exposed to simulated sunlight irradiation for 0, 200, 500, and 800 h, and Cr(VI) reduction was hindered by increased O and •OH formation and light-screening effects (decreased photon absorption). The size, functional groups and concentration of PS MPs and environmental factors (e.g., humic acid, pH, Mg, Fe and O) strongly affected Cr(VI) reduction. Furthermore, Cr(VI) reduction induced by PS MPs could occur in reservoir water, and the reduction rate was faster than that in double distilled (DD) water. Correspondingly, PS MPs (1 mg/L) decreased the oxidative stress induced by Cr(VI) to Lemna minor in reservoir water after 96 h of sunlight irradiation. This study provided deep insight into how PS MPs affect Cr species transformations and hazardous effects in realistic aquatic environments under sunlight conditions.

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