Fig. 1. Near Infrared microplastic measuring system
1: Optical fiber; 2: Sample; 3: Integrating sphere with light source; 4: Receiving optical fiber; 5: Spectral collection module; 6: Spectral processing module; 7: Photoelectric conversion module; 8: Date processing module

Fig. 2. K-fold cross-validation structure

Fig. 3. XGBoost and SVM for microplastic detection

Fig. 4. Original Near Infrared spectra of microplastics

Fig. 5. The 30 most important spectral variables

Fig. 6. CV average accuracy of n_estimators, learning_rate, max_depth, gamma

Fig. 7. SVM and XGBoost confusion matrixes

Fig. 8. Accuracy score, precision score, recall and F1-score of 10-fold cross validations of XGBoost and SVM