Science Buddies: "Ask an Expert"

I have a student that wants to use bioluminescent bacteria as a water pollutant indicator. We are focused on heavy metals, specifically Cu, Cd, and Pb. To create known concentration solutions of each of these metals (I plan to have her start at 1M and do a serial dilution), would I have her use metal salts or is there a better way to toxify the water? Thank you.

Metal salts are definitely the best option! These salts are stable, easy to handle, and will dissociate in solution, releasing the metal ions in their available forms, which is what would interact with the bioluminescent bacteria and potentially affect their bioluminescence.