To normalize the freezing data to the mass or surface area of the microplastics and facilitate comparison with existing literature, we calculated the number of nucleation sites per unit mass, 𝑛 𝑚 (𝑇) (Equation ) and per surface area, 𝑛 𝑠 (𝑇) (Equation ). gives the reciprocal of the mass concentration of the sample suspension, and 𝑠 represents the surface area of the particles.