地质科技通报 (Jul 2022)
Migration mechanism of nanoplastic particles in saturated porous media
Abstract
To investigate the migration of nanoplastic particles in saturated porous media and the associated influencing factors, polystyrene nanoparticles (PSNPs) are selected as typical nanoplastics in this study. The migration behavior and mechanism of PSNPs in saturated porous media is investigated through a combination of physical experiments and DLVO theory. First, the interaction energy between PSNPs and quartz sand particles is calculated based on DLVO theory, and then a column experiment is conducted to investigate the characteristics of PSNP migration in porous media under different conditions.According to the experimental results, when the ionic strength (NaCl) increases from 1 mmol/L to 50 mmol/L, the value of the energy barrier between PSNPs and quartz sand based on DLVO theory gradually decreases from 215.13 KT to 45.9 KT. PSNPs are easier to be adsorbed on the surface of quartz sand media, thereby reducing the migration ability of PSNPs in porous media, the penetration rate consequently decreases from 62.16% to 3.65%. When the ionic strength (CaCl2) increases from 0.1 mmol/L to 5 mmol/L, the value of the energy barrier decreases from 33.72 KT to 14.03 KT, and the penetration rate decreases from 82.46% to 4.27%. These experimental phenomena indicate that increasing the ionic strength can inhibit the penetration of PSNPs, and Ca2+ has a stronger charge shielding effect than Na+. At the same time, increasing the initial concentration, flow rate and particle size of the medium can increase the penetration rate of PSNPs, while the penetration rate of large-diameter PNSPs particles is smaller. The implementation of this research will contribute to further understanding the environmental behavior and risks of nanoplastics in porous media and provide a scientific basis for accurately predicting and assessing the environmental risks of nanoplastics in soil-groundwater systems.
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