Identifying Microplastics with Fluorescent Dye
99% of Ocean Microplastics Still Undetected
Previous scientific field work surveys report that only 1% of the plastic waste in the oceans has been found yet. With an innovative and cheap new method, developed by University of Warwick researchers, smallest microplastics in oceans can be identified more effectively.
New research, led by Gabriel Erni-Cassola and Dr. Joseph A. Christie-Oleza from Warwick’s School of Life Sciences, Warwick, UK, has established a pioneering way to detect the smaller fraction of microplastics – many as small as 20 micrometers (comparable to the width of a human hair or wool fiber) – using a fluorescent dye. The dye specifically binds to plastic particles, and renders them easily visible under a fluorescence microscope. This allows scientists to distinguish microplastics amongst other natural materials and makes it easy to accurately quantify them.
To test their new method, the researchers took samples from surface sea water and beach sand from the English coast around Plymouth – and, after extracting the microplastics from these environmental samples, they applied their method and were able to quantify the smaller fraction of microplastics effectively. The researchers detected a much larger amount of small microplastics (smaller than 1 mm) than was previously estimated – and significantly more than would have been identified previously with traditional methods.
These results challenge the current belief of the apparent loss of the smallest microplastics from surface seawater, and highlights the need of further research to understand the real fate of plastic waste in the oceans. Interestingly, the researchers also discovered that the greatest abundance of microplastics of this small size was polypropylene, a common polymer which is used in packaging and food containers – demonstrating that our consumer habits are directly affecting the oceans. Gabriel Erni-Cassola comments: “Using this method, a huge series of samples can be viewed and analysed very quickly, to obtain large amounts of data on the quantities of small microplastics in seawater or, effectively, in any environmental sample. Current methods used to assess the amount of microplastics mostly consist in manually picking the microplastics out of samples one by one – demonstrating the great improvement of our method.”
The research "Lost, but found with Nile red; a novel method to detect and quantify small microplastics (20 μm–1 mm) in environmental samples" is published in Environmental Science & Technology.
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