Black dust in the engine bay / AdBlue injector leak?

Hello everyone! New member here and a new owner of a SKODA Superb III 2019 2.0 TDI 110KW with AdBlue. 

I would like to ask for help with the black dust particles I found in the engine bay. Recently, I replaced a coolant expansion tank with one without the silica bag and noticed black dust particles. I have attached photos for a better understanding.

Has somebody had a problem like this, or what could be the reason for these black particles?

Maybe AdBlue injector is leaking or a clamp?

Thank everybody for their help!🙂