Microplastics Concentration Difficulty

[Xagan]

Hi everyone,

I would really appreciate some advice. For my college project, I'm researching the impacts that microplastics have upon Artemia salina, and one of the things we will be assessing is the LC50 (the lethal concentration that will kill 50% of the test population) value of the microplastics over a 96 hour test period.

A lot of research has gone into this project to get it going, but one sticking point I'm having is understanding the idea of working out the concentrations of microplastics. I like the idea of measuring out the plastics in either micrograms or microlitres per millilitres, but according to researchers and the microplastic distributors, it is much more scientific to measure in particles per mL, which I understand in theory, but how you would work out the number of tiny microplastic particles per millilitre is something beyond me.

Unfortunately, only one LC50 has previously been calculated for microplastics, and that was a ten day LC50 test for a small species of fresh water amphipod. The LC50 concentration was 4.6 × 10⁴ microplastics/mL. Now, I'm not going to lie, I have absolutely no idea what that concentration means, but I need to know it as I'm going to use that as a rough indicator to use as one of our upper level concentrations for our experiments, since it has caused mortalities in a similar sized organism to the one in our experiments.

We have 10mL of microplastics at our disposal. The distributor states that the 10mL is 5% w/v (I'm not sure what that means). They said that since the density of polystyrene is to all intents and purposes the same as water (actually 1.05), 10mL of the particles contains approx. 0.5g of polymer. We're going to have to centrifuge the microplastics to remove the storage chemicals, so when that's done we'll have to re-suspend the plastics in clean water.

We will be using 250mL vessels with 200mL of water to carry out the experiments. Sorry for rambling on, but practically what I need help with is how to work out the concentrations. I mean, how would I work out and get the concentration of 4.6 × 10⁴ microplastics/mL? I can only get my head around the idea of µg or µl per mL!

Any help would be much appreciated.

Xagan

[wtf]

I'd use Zorn's lemma.