EXPERIMENTAL STUDY ON EFFECT OF SOIL COLLOIDS ON MOBILITY OF NANOPLASTICS UNDER DIFFERENT HYDROCHEMICAL CONDITIONS
To investigate the effect of soil colloids on the migration of nanoplastics under different hydrochemical conditions,Polystyrene nanoplastics(PSNPs)with a particle size of 100 nm were selected,and soil colloids were extracted by siphon method.The mechanism of PSNPs migration in saturated porous media was revealed by zeta potential and DLVO theory.The results showed that the migration of PSNPs was influenced by the pH and the ionic strength(IS).The mobility of PSNP increased with the increase of pH and decreased with the increase of IS.Variations in pH and IS altered the surface charges of both PSNPs and porous media thus affecting the interaction energy.As pH increased from 4.0 to 9.0(10 mmol/L NaCl,bentonite colloid),the peak DLVO barrier increased from 45.11 kT to 61.89 kT,and the zeta potential was significantly reduced.The migration capacity of the PSNPs was improved,resulting in a rise in the outflow rate from 42.80％to 62.21％.Both bentonite colloids and illite colloids accelerated the migration of PSNPs in saturated porous media,whereas the effect of bentonite colloids on the mobility of PSNPs was more significant.The results provide valuable insights into the migration of PSNPs in subsurface soil and water environments,which is of great importance for the prevention of plastic pollution.
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