A novel heating-assisted density separation method for extracting microplastics from sediments

Microplastics (MPs) pollution in the marine has become a global concern. To obtain accurate measurements of MPs in the marine sediments is important for understanding its effects and potential risks to the environment. In this study, we developed a novel method for extracting MPs from sediments by density flotation of sodium dihydrogen phosphate (NaHPO) solution, which utilized the heating-assisted to increase the density of separation solution. It features high density, nontoxic, and economic, indicating its promising application in the MPs extraction. A standard procedure based on NaHPO for extracting MPs from sediments was established and validated by the recovery experiments of seven common plastics. Results showed NaHPO solution exhibited higher recovery rates than the commonly-used NaCl solution; three plastics with high density couldn't be recovered by NaCl, while NaHPO was available for all the studied MPs. A large number of real beach samples was collected and validated by this method, and the abundance and characteristic of the collected MPs were further analyzed. Results exhibited the heating-assisted NaHPO could be a promising way for extracting MPs in environmental samples.