Effect of gastric fluid on adsorption and desorption of endocrine disrupting chemicals on microplastics

Microplastics and endocrine disrupting chemicals are emerging pollutants in the marine environment because of their potential hazards. The effect of gastric fluid on the adsorption and desorption of 17 beta-estradiol (E2) and 17 alpha-ethynylestradiol (EE2) to microplastics was investigated. The adsorption and desorption isotherms of E2/EE2 on microplastics could be well fitted by the Freundlich model while the Gibbs free energy of these processes were negative, proving that the reaction occurred spontaneously on the heterogeneous surface of the microplastics. Desorption ratios of EE2 (55%-59%) on PVC were larger than that of E2 (49%-55%) to indicate that EE2 was less stable in gastric fluid, which could be explained by the fact that the hydrophobicity of EE2 was greater than E2. E2/EE2 were more easily desorbed from PVC in the gastric fluid and the desorption amount (5.25-12.91/7.19-17.86 mu g/g) increased by 2.51 times in comparison with that in saline solution (2.22-7.81/2.87-10.80 mu g/g). The decrease of pH and the increase of ionic strength in gastric fluid could further strengthen desorption of E2/EE2 from PVC. The promotion of gastric juice on desorption of PVC was achieved by reducing the hydrophobicity of the PVC surface. The desorption rate of E2/EE2 at 18 degrees C and 38 degrees C was respectively 44%-47%/46%-50% and 49%-55%/56%-59%, indicating that PVC loaded with E2/EE2 had a relatively greater risk of releasing pollutants in the gastric fluid of constant temperature marine organisms while higher temperatures exposed higher hazards for variable temperature animals. The interaction between microplastics and pollutants might be mainly hydrophobic interaction. (C) Higher Education Press 2022

Automated summary

Gastric fluid affects the adsorption and desorption of endocrine disrupting chemicals on microplastics, leading to their release in the marine environment. The decrease of pH and the increase of ionic strength in gastric fluid enhance the desorption of these chemicals from microplastics.