Crop-dependent changes in water absorption of expanded polystyrene in soil environments

As expanded polystyrene (EPS) has been utilized in soil environments, there is a need to understand interactions between chemical adsorption and the soil system. We conducted a plant bioassay using agricultural crops in a soil system containing a macro-sized EPS (83 0.5 mm). When the EPS was collected after cultivation of no crop (control), mung bean, lettuce, and rice, we found that its water absorption rate significantly (p < 0.05) increased after mung bean and rice cultivation as compared to the no crop condition. We expected that these crop-dependent differences would be highly linked with metal adsorption and desorption. However, cadmium (Cd) adsorption percentages (%) from the initial Cd solution were calculated as 15-18% with no significant differences between the different crop cultivation conditions. The desorption percentages also showed low levels of interaction with the crop-dependent water absorption rate. These results provide useful data for better understanding the interaction between plastics and their roles as chemical vectors in the soil system. (C) 2018 Elsevier Ltd. All rights reserved.