Comparison of cellulolytic enzyme treatment and Fenton oxidation for analysis of microplastics in tire rubber particles

Uncertainties in the quantification of microplastics in various products arise from the applied pretreatment processes. Road dust, a significant source of microplastics, requires precise quantification methods to ensure accuracy. In this study, we examined the impact of pretreatment processes on the accuracy of microplastic quantification in road dust, specifically focusing on tire rubber particles. We compared the effects of cellulolytic enzyme (EZM) and Fenton (FT) treatments by analyzing the changes in particle number, size, shape, and identification accuracy for each treatment. Both treatments increased the number of tire rubber particles, reduced their size, and made them more spherical. Notably, the FT treatment resulted in smaller particle parameters (Feret, MinFeret, Major, Minor, and Area) compared to the EZM treatment. Identification accuracy also varied, with 89% of tire rubber particles identified after EZM treatment, compared to 51% after FT treatment. Furthermore, microplastic volume was overestimated by 4.5% following EZM treatment and underestimated by 21% after FT treatment. These findings demonstrate that pretreatment procedures significantly influence the accuracy of microplastic quantification. Our study underscores the need for further research to determine whether current microplastic estimates are accurate, as the estimated volume can change due to organic removal processes. PRACTITIONER POINTS: Pretreatment to eliminate organic materials is necessary for improving the efficiency of microplastic analysis. Tire rubber particles (TRPs) are a significant plastic material found in urban surfaces. Pretreatment can reduce the size of TRPs and lead to material misidentification of materials. Compared to the Fenton oxidation treatment, cellulolytic enzyme treatment results in less particle fragmentation and volume modification.