Palladium is mined in North America/Canada, South Africa, and Russia inside deposits of nickel-copper sulphide and olivine-rich rocks.
There are various methods to mine Palladium including the ramp and fill method, Sub-level stoping, and slash-cut and fill mining. These are generally done by extracting an area then refilling it with the extra rocks or sand that was brought up with the palladium.
Ammonium chloride and aqua regia are used in the process of purifying palladium so it can be used. Ammonium chloride is used in order to precipitate the palladium which is then subjected to the aqua regia in order to dissolve the palladium. Overall, the process to purify palladium has little to no impact on the environment