Uranium accumulation in environmentally relevant microplastics and agricultural soil at acidic and circumneutral pH

Casey Miller; Andrew Neidhart; Kendra Hess; Abdul-Mehdi S Ali; Angelica Benavidez; Michael Spilde; Eric Peterson; Adrian Brearley; Xuewen Wang; B Dulani Dhanapala; José M Cerrato; Jorge Gonzalez-Estrella; Eliane El Hayek

doi:10.1016/j.scitotenv.2024.171834

Uranium accumulation in environmentally relevant microplastics and agricultural soil at acidic and circumneutral pH

Sci Total Environ. 2024 May 20:926:171834. doi: 10.1016/j.scitotenv.2024.171834. Epub 2024 Mar 21.

Authors

Affiliations

¹ Gerald May Department of Civil, Construction & Environmental Engineering, MSC01 1070, University of New Mexico, Albuquerque, NM 87131, USA; Department of Pharmaceutical Sciences, MSC09 5360, University of New Mexico, College of Pharmacy, Albuquerque, NM 87131, USA.
² Department of Pharmaceutical Sciences, MSC09 5360, University of New Mexico, College of Pharmacy, Albuquerque, NM 87131, USA; Department of Chemistry and Chemical Biology, MSC03 2060, University of New Mexico, Albuquerque, NM 87131, USA.
³ School of Civil and Environmental Engineering, EN0059, Oklahoma State University, Stillwater, OK 740784, USA.
⁴ Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, NM 87131, USA.
⁵ Center for Micro-Engineered Materials, University of New Mexico, Albuquerque, NM, USA.
⁶ College of Engineering, Architecture, and Technology, Oklahoma State University, Stillwater, OK 740784, USA.
⁷ Gerald May Department of Civil, Construction & Environmental Engineering, MSC01 1070, University of New Mexico, Albuquerque, NM 87131, USA.
⁸ Department of Pharmaceutical Sciences, MSC09 5360, University of New Mexico, College of Pharmacy, Albuquerque, NM 87131, USA. Electronic address: eelhayek@salud.unm.edu.

PMID: 38521258
DOI: 10.1016/j.scitotenv.2024.171834

Abstract

The co-occurrence of microplastics (MPs) with potentially toxic metals in the environment stresses the need to address their physicochemical interactions and the potential ecological and human health implications. Here, we investigated the reaction of aqueous U with agricultural soil and high-density polyethylene (HDPE) through the integration of batch experiments, microscopy, and spectroscopy. The aqueous initial concentration of U (100 μM) decreased between 98.6 and 99.2 % at pH 5 and between 86.2 and 98.9 % at pH 7.5 following the first half hour of reaction with 10 g of soil. In similar experimental conditions but with added HDPE, aqueous U decreased between 98.6 and 99.7 % at pH 5 and between 76.1 and 95.2 % at pH 7.5, suggesting that HDPE modified the accumulation of U in soil as a function of pH. Uranium-bearing precipitates on the cracked surface of HDPE were identified by SEM/EDS after two weeks of agitation in water at both pH 5 and 7.5. Accumulation of U on the near-surface region of reacted HDPE was confirmed by XPS. Our findings suggest that the precipitation of U was facilitated by the weathering of the surface of HDPE. These results provide insights about surface-mediated reactions of aqueous metals with MPs, contributing relevant information about the mobility of metals and MPs at co-contaminated agricultural sites.

Keywords: Agricultural soil; Microplastics; Precipitation; Surface chemistry; Uranium.

Abstract

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