I'm late responding, but why no backscattered electron images from the SEMs? The micropastics should have a really low average Z, I think the stearates will be

I'm late responding, but why no backscattered electron images from the SEMs? The micropastics should have a really low average Z, I think the stearates will be much higher and distinguishable in a BSE image, and (not to mention if you observe their x-ray spectrum...) So I'm either confused about something or pointing out that they're hard to distinguish in an SE image is not really a useful point, ... it's more relevant that SEM isn't the typical tool used for these counting efforts. I'd look myself but I recently moved and the SEM is in parts. :)