Why is mercury (II) sulfide less of an environmental concern than mercury(II) nitrate?
I am not sure of this, but I would suspect that it has to do with solubility. Lead can also be quite toxic. However, I know that the mineral galena (lead sulfide) is not much of a concern because it is biologically inert. The sulfur hold onto the lead atoms so strongly that they can’t get loose to cause problems. I would suspect that it is probably the same thing with mercury sulfide. Sulfur hangs on to the mercury more strongly than the nitrate ions do. So, the sulfur prevents the mercury from being available to poison life forms while the nitrate ion does not.
