Study on Recognition of Marine Microplastics Using Raman Spectra
Combined With MTF and CNN
ZHANG Wei1, 2, FENG Wei-wei2, 3*, CAI Zong-qi2, WANG Huan-qing2, YAN Qi1, WANG Qing2, 3
1. Yantai Research Institute of Harbin Engineering University, Yantai 264000, China
2. CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：In recent years, seawater pollution caused by microplastic waste has caught more and more attention. Raman spectroscopy, a non-destructive detection technique, has representative spectral characteristic peaks, making it easier to identify unknown samples. It has always been one of the popular detection methods in biochemical analysis. Deep learning has made remarkable achievements in feature extraction, target detection, and other fields. The feasibility of Raman spectroscopy based on the Markov transition field (MTF) combined with a convolution neural network (CNN)was explored for the accurate and efficient detection of microplastics. The Raman spectra of eleven types of microplastic samples were collected, and 100 spectra were collected for each sample; then, the spectral dataset was expanded through data augmentation. The one-dimensional Raman spectral data was converted into two-dimensional images using a Markov transition field to obtain a two-dimensional image spectral dataset. A small-sized multiple-kernel-based convolutional neural network (SSMKB-CNN) model with continuous small-scale convolutional kernels is designed, including one input layer, six convolutional layers, two pooling layers, one flattened layer, two fully-connected layers, and one output layer. The classification performance of the model is compared with the classification results of AlexNet, VGG16, and ResNet50 deep convolution neural network models based on a two-dimensional MTF image spectral dataset, along withthree classical machine learning classifiers based on a one-dimensional spectral dataset, including K-nearest neighbors (KNN), random forest (RF) and support vector machine (SVM)with three kernel functions (rbf, Linear and Poly). It could be seen from the training curves and the classification confusion matrix that the loss and accuracy curves of the four CNN models are stable and can achieve a good training effect. The accuracy rate of the proposed SSMKB-CNN model reaches 97.04%, and the macroprecision rate, recall rate, and F1-score are 97.05%, 95.06%, and 97.02%, respectively, which is superior to the other three CNN models used for comparison and the three machine learning classifiers. Each training epochconsumes 9 seconds, less than the three CNN models. Overall, the proposed SSMKB-CNN model has the best classification performance. The experimental results show that the Raman spectrum and SSMKB-CNN model combined with MTF can accurately and efficiently extract spectral features and make precise predictions, and the qualitative identification of microplastic samples using the Raman spectrum is realized. It can provide a method reference for the recognition technology of actual microplastic contaminants in seawater.
张 蔚，冯巍巍，蔡宗岐，王焕卿，闫 奇，王 清. 基于MTF变换的拉曼光谱和卷积神经网络的海水微塑料识别方法研究[J]. 光谱学与光谱分析, 2024, 44(09): 2420-2427.
ZHANG Wei, FENG Wei-wei, CAI Zong-qi, WANG Huan-qing, YAN Qi, WANG Qing. Study on Recognition of Marine Microplastics Using Raman Spectra
Combined With MTF and CNN. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(09): 2420-2427.
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