Dheivanai P. for Accessing the microplastics accumulation in water bodies one can try these steps:

• Sampling: Researchers collect water samples from different depths and locations within the water body.
• Filtration: The water samples are filtered to capture microplastics of various sizes.
• Separation: Techniques like density separation or chemical digestion are used to isolate microplastics from other particles.
• Identification and Quantification: Microplastics are identified under a microscope or using advanced techniques like spectroscopy. Their quantity is determined by counting or weighing.
• Data Analysis: The collected data is analyzed to assess the extent of microplastic pollution, identify sources, and understand the potential ecological impacts.

It requires advanced technology in order to detect it in water.

As of my study, when I got interested & explored about it long time ago... I found it's nearly expensive to remove micro plastic.

But I would recommend you to utilize multiple layers of filter paper in micro pore size. Then calculate the results.. You will find significant reduction..