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 (NaH₂PO₄) 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 NaH₂PO₄ for extracting MPs from sediments was established and validated by the recovery experiments of seven common plastics. Results showed NaH₂PO₄ solution exhibited higher recovery rates than the commonly-used NaCl solution; three plastics with high density couldn't be recovered by NaCl, while NaH₂PO₄ 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 NaH₂PO₄ could be a promising way for extracting MPs in environmental samples.