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Effect of Polystyrene Microplastics on Pb(II) Adsorption onto a Loessial Soil (Sierozem) and Its Mechanism

ACS Omega 2024 10 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Yin Zhang, Baowei Zhao, Xin Zhang, Yingquan Li, Hui Liu, Jian Zhang, Tuo Wang

Summary

Researchers examined how polystyrene microplastics affect the adsorption of lead onto loessial soil and found that the presence of microplastics reduced lead uptake by the soil. Smaller microplastic particles had a greater inhibitory effect on lead adsorption compared to larger ones, likely due to competitive binding on soil surfaces. The study suggests that microplastic contamination in agricultural soils could alter heavy metal mobility and increase environmental risk.

Polymers

Microplastics (MPs) have received significant attention recently. However, their influence on soil heavy metal adsorption remains unclear. The effect of polystyrene (PS) MPs on the adsorption of Pb(II) onto a loessial soil (sierozem) was studied by batch experiments in single soil (S), soil with 1 mm PS (S-PS1), and soil with 100 μm PS (S-PS100) systems. The mechanisms of Pb(II) adsorption reduction were investigated. The adsorption of Pb(II) reached equilibrium within 12 h, and the pseudo-second-order model fitted the adsorption processes best. The Langmuir adsorption model provided a better fit to the isotherms, compared to the Freundlich one. The presence of PS decreased the level of adsorption of Pb(II). Larger PS particle size, dose, and fulvic acid (FA) concentration inhibited Pb(II) adsorption onto the soil. The solution pH value showed a positive correlation with the adsorption amount. The adsorption amounts (q e) of Pb(II) in binary metal systems (Cu-Pb and Cd-Pb) were lower than those in single Pb systems, indicating the competitive adsorption among the ions. The adsorption amount presented a trend of S > S-PS100 > S-PS1. The primary mechanism on which PS reduced the adsorption of Pb(II) was the "dilution effect" of MPs. Conclusively, the presence of MPs might elevate the availability of heavy metals by reducing the soil's adsorption capacity for them and then amplifying the risk of heavy metal contamination and migration.

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