近海微塑料含量的相干反斯托克斯拉曼光谱成像研究

Research on Coherent Anti-Stokes Raman Spectroscopy Detection of Microplastics in Seawater and Sand

由于塑料工业的发展,微塑料成为一种主要的环境污染物。它在自然界中不易降解,对人类的生存环境及健康都存在不可忽视的潜在危险。因此,环境中微塑料的检测和分析,成为了近年来研究的热点问题。目前人们大多数采用浮选法、密度分离法、离心法等方法提取微塑料,然后放在显微镜下进行目视观察,并结合拉曼光谱分析、傅里叶红外光谱分析、高光谱成像等方法进行分析鉴别,这些方法需要较长时间的等待或预处理,且易受主观因素的影响。因此提出一种快速、准确鉴别环境中是否含有微塑料的技术是必要的。相干反斯托克斯拉曼散射(CARS)光谱成像技术是一种基于化学键振动的非侵入性、非破坏性且无需特殊标记的实时成像方法,由此提出使用多通道图像采集(含有白光通道成像及CARS光谱成像)的方法快速、准确鉴别环境中微塑料的分布。将直径为10μm的聚苯乙烯微球掺入到收集的海水及沙子中,模拟被微塑料污染的海水及沙子,在不作任何处理的情况下对海水及沙子进行多通道图像采集。通过多通道图像采集可以快速直观地检测到海水中聚苯乙烯微球的分布。在对沙子中的聚苯乙烯微球进行多通道图像采集的同时,采用拉曼光谱检测与之对照。在拉曼光谱检测中,聚苯乙烯微球的信号易受沙子荧光信号干扰,且只有在激光聚焦在聚苯乙烯存在的位置时,才能检测到微弱的信号。在多通道图像采集检测中,可以看到沙子中存在的聚苯乙烯微球,且采用形态学分析中先腐蚀后膨胀的开运算算法同时结合中值滤波的算法后,可以实现突出显示聚苯乙烯信号的目的。多通道图像采集可以在无任何预处理的情况下检测出海水及沙子中的微塑料,具有快速简便的优势,对实现环境中微塑料的检测具有一定的潜在应用价值。

With the development of the plastic industry,microplastic,which is difficult to degrade in nature,became one of the main environmental pollutants.Moreover,it harms human health as it accumulates within the organisms and environment.Therefore,the detection and assessment of microplastics in the environment have been highly concern in recent years.Most the works first extract microplastics from samples by flotation,density or centrifugation separation system,and then find the microplastics under a microscope directly or combine with Raman spectroscopy,Fourier Transform infrared spectroscopy,Hyperspectral imaging and other methods for analysis and identification.Nonetheless,these methods require a long waiting time for pretreatment and could easily be affected by subjective factors.To identify whether the microplastics are in environmental samples or not quickly and accurately,we propose to use the multi-channel image acquisition,including white light channel imaging and Coherent Anti-stokes Raman Scattering(CARS) spectral imaging.CARS spectral imaging is a non-invasive and non-destructive real-time imaging method based on chemical bond vibration.Microplastic with a diameter of 10 μm polluted seawater and sand were simulated by the collected seawater/sand mixing with polystyrene microspheres.We detected the distribution of polystyrene in seawater intuitively through multi-channels image acquisition.The multi-channel image of polystyrene microspheres in the sand was collected and compared with the image by Raman spectroscopy.In the detection of Raman spectroscopy,the signal of polystyrene microspheres is easily interfered with by the fluorescence signal of sand,and only when the laser is focused on the location of polystyrene,does the weak signal can be detected.In the multi-channel image acquisition and detection,polystyrene microspheres can be seen in the sand,and we used a simple morphological analysis and filtering algorithm to make the microplastic signal obvious.Multi-channels image acquisition for microplastics detecting(in seawater and sand) without pretreatment is fast and simple,which has a certain potential for detecting microplastics in the environment value.